2005-04-20 07:41:24 +00:00
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<?xml version="1.0" encoding="iso-8859-2"?>
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2005-05-09 05:43:21 +00:00
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<!-- Synced with: 1.58 -->
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2005-04-20 07:41:24 +00:00
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<chapter id="mencoder">
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<title>Enk<EFBFBD>dov<EFBFBD>n<EFBFBD> s <application>MEncoder</application>em</title>
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<para>
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<EFBFBD>pln<EFBFBD> seznam dostupn<70>ch voleb a p<><70>klad<61> pro <application>MEncoder</application>
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naleznete v man str<74>nce. <20>adu u<>ite<74>n<EFBFBD>ch p<><70>klad<61> a podrobn<62>ch n<>vod<6F> pro
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pou<EFBFBD>it<EFBFBD> mnoha enk<6E>dovac<61>ch voleb naleznete v
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<ulink url="../../tech/encoding-tips.txt">tipech pro enk<6E>dov<6F>n<EFBFBD></ulink>, kter<65>
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byly z<>sk<73>ny z n<>kolika diskus<75> v konferenci MPlayer-users. Prohledejte
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<ulink url="http://mplayerhq.hu/pipermail/mplayer-users/">archivy</ulink>,
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chcete-li bohatost diskus<75> o v<>ech aspektech a probl<62>mech vzta<74>en<65>ch
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k enk<6E>dov<6F>n<EFBFBD> <application>MEncoder</application>em.
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</para>
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<sect1 id="menc-feat-mpeg4">
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<title>Dvoupr<EFBFBD>chodov<EFBFBD> enk<6E>dov<6F>n<EFBFBD> MPEG-4 ("DivX")</title>
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<para>
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N<EFBFBD>zev vych<63>z<EFBFBD> z faktu, <20>e soubor je enk<6E>dov<6F>n <emphasis>dvakr<EFBFBD>t</emphasis>.
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Prvn<EFBFBD> enk<6E>dov<6F>n<EFBFBD> (dubbed pass) vytvo<76><6F> do<64>asn<73> soubory
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(<filename>*.log</filename>) velikosti n<>kolika megabajt<6A>, kter<65> zat<61>m nema<6D>te
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(m<><6D>ete smazat AVI). Ve druh<75>m pr<70>chodu je vytvo<76>en dvoupr<70>chodov<6F> v<>stupn<70>
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soubor s pou<6F>it<69>m <20><>zen<65> datov<6F>ho toku z do<64>asn<73>ch soubor<6F>. V<>sledn<64> soubor
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bude m<>t lep<65><70> kvalitu obrazu. Pokud jste o tom te<74> sly<6C>eli poprv<72>, m<>li byste
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si prostudovat n<>kter<65> n<>vody dostupn<70> na netu.
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</para>
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<example>
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<title>kop<EFBFBD>rov<EFBFBD>n<EFBFBD> zvukov<6F> stopy</title>
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<para>
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Dvoupr<EFBFBD>chodov<EFBFBD> enk<6E>dov<6F>n<EFBFBD> DVD do MPEG-4 ("DivX") AVI zat<61>mco se zvuk
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pouze zkop<6F>ruje.
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<screen>
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mencoder dvd://2 -ovc lavc -lavcopts vcodec=mpeg4:vpass=1 -oac copy -o <replaceable>film.avi</replaceable>
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mencoder dvd://2 -ovc lavc -lavcopts vcodec=mpeg4:vpass=2 -oac copy -o <replaceable>film.avi</replaceable>
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</screen>
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</para>
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</example>
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<example>
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<title>enk<EFBFBD>dov<EFBFBD>n<EFBFBD> zvukov<6F> stopy</title>
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<para>
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Dvoupr<EFBFBD>chodov<EFBFBD> enk<6E>dov<6F>n<EFBFBD> DVD do MPEG-4 ("DivX") AVI a sou<6F>asn<73>
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enk<EFBFBD>dov<EFBFBD>n<EFBFBD> zvukov<6F> stopy do MP3.
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<screen>
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mencoder dvd://2 -ovc lavc -lavcopts vcodec=mpeg4:vpass=1 -oac mp3lame -lameopts vbr=3 -o <replaceable>film.avi</replaceable>
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mencoder dvd://2 -ovc lavc -lavcopts vcodec=mpeg4:vpass=2 -oac mp3lame -lameopts vbr=3 -o <replaceable>film.avi</replaceable>
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</screen>
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</para>
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</example>
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</sect1>
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<sect1 id="menc-feat-mpeg">
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<title>Enk<EFBFBD>dov<EFBFBD>n<EFBFBD> do MPEG form<72>tu</title>
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<para>
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<application>MEncoder</application> um<75> vytvo<76>it v<>stupn<70> soubor form<72>tu
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MPEG (MPEG-PS). To je pravd<76>podobn<62> pou<6F>iteln<6C> pouze s <emphasis>mpeg1video</emphasis>
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2005-04-20 09:22:27 +00:00
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kodekem z <link linkend="ffmpeg"><systemitem class="library">libavcodec</systemitem></link>, proto<74>e
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2005-04-20 07:41:24 +00:00
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p<EFBFBD>ehr<EFBFBD>va<EFBFBD>e – s v<>jimkou <application>MPlayer</application>u –
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o<EFBFBD>ek<EFBFBD>vaj<EFBFBD> MPEG-1 video a MPEG-1 layer 2 (MP2) audio proudy v MPEG souborech.
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</para>
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<para>
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Tato vlastnost nyn<79> nen<65> moc u<>ite<74>n<EFBFBD>, pomi<6D>me <20>e m<> asi mnoho chyb, ale hlavn<76>
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proto, <20>e <application>MEncoder</application> v sou<6F>asnosti neum<75> enk<6E>dovat
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MPEG-1 layer 2 (MP2) zvuk, kter<65> v<>echny ostatn<74> p<>ehr<68>va<76>e o<>ek<65>vaj<61> v MPEG
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souborech.
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</para>
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<para>
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V<EFBFBD>stupn<EFBFBD> souborov<6F> form<72>t <application>MEncoder</application>u zm<7A>n<EFBFBD>te pou<6F>it<69>m
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volby <option>-of mpeg</option>.
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</para>
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<para>
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Example:
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<screen>
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mencoder -of mpeg -ovc lavc -lavcopts vcodec=mpeg1video -oac copy <replaceable>dal<EFBFBD><EFBFBD>_volby</replaceable> <replaceable>media.avi</replaceable> -o <replaceable>v<EFBFBD>stup.mpg</replaceable>
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</screen>
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</para>
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</sect1>
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<sect1 id="menc-feat-rescale">
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<title><EFBFBD>k<EFBFBD>lov<EFBFBD>n<EFBFBD> (zm<7A>na velikosti) film<6C></title>
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<para>
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<EFBFBD>asto pot<6F>ebujeme zm<7A>nit velikost obr<62>zk<7A> ve filmu a to z mnoha d<>vod<6F>: zmen<65>en<65>
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souboru, z<>t<EFBFBD><74>e s<>t<EFBFBD> atd. Mnoho lid<69> dokonce m<>n<EFBFBD> velikost p<>i p<>evodu DVD nebo
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SVCD do DivX AVI. Pokud si p<>ejete video p<>e<EFBFBD>k<EFBFBD>lovat, p<>e<EFBFBD>t<EFBFBD>te si sekci
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<link linkend="aspect">Zachov<EFBFBD>n<EFBFBD> pom<6F>ru stran</link>.
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</para>
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<para>
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Samotn<EFBFBD> proces <20>k<EFBFBD>lov<6F>n<EFBFBD> je prov<6F>d<EFBFBD>n video filtrem <literal>scale</literal>:
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<option>-vf scale=<replaceable><EFBFBD><EFBFBD><EFBFBD>ka</replaceable>:<replaceable>v<EFBFBD><EFBFBD>ka</replaceable></option>.
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Jeho kvalita m<><6D>e b<>t nastavena volbou <option>-sws</option>.
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Pokud ji neuvedete, <application>MEncoder</application> pou<6F>ije 2: bikubickou.
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</para>
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<para>
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Pou<EFBFBD>it<EFBFBD>:
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<screen>
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mencoder <replaceable>vstup.mpg</replaceable> -ovc lavc -lavcopts vcodec=mpeg4 -vf scale=640:480 -o <replaceable>v<EFBFBD>stup.avi</replaceable>
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</screen>
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</para>
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</sect1>
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<sect1 id="menc-feat-streamcopy">
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<title>Proudov<EFBFBD> kop<6F>rov<6F>n<EFBFBD></title>
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<para>
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<application>MEncoder</application> m<><6D>e zpracovat vstupn<70> datov<6F> proudy dv<64>ma
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zp<EFBFBD>soby:
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<emphasis role="bold">enk<EFBFBD>duje</emphasis> je, nebo je
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<emphasis role="bold">kop<EFBFBD>ruje</emphasis>. Tato <20><>st je o
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<emphasis role="bold">kop<EFBFBD>rov<EFBFBD>n<EFBFBD></emphasis>.
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</para>
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<itemizedlist>
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<listitem><para>
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<emphasis role="bold">Video proud</emphasis> (volba <option>-ovc copy</option>):
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m<><6D>ete d<>lat p<>kn<6B> v<>ci :) Jako um<75>st<73>n<EFBFBD> (nikoli konverze!) FLI nebo VIVO nebo
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MPEG-1 videa do AVI souboru! Samoz<6F>ejm<6A> takov<6F> soubory p<>ehraje pouze
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<application>MPlayer</application> :) A proto to nejsp<73><70> nem<65> <20><>dnou rozumnou
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hodnotu. A te<74> v<><76>n<EFBFBD>: kop<6F>rov<6F>n<EFBFBD> video proudu m<><6D>e b<>t u<>ite<74>n<EFBFBD> nap<61><70>klad
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tehdy, kdy<64> m<> b<>t enk<6E>dov<6F>n pouze zvuk (nap<61>. nekomprimovan<61> PCM do MP3).
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</para></listitem>
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<listitem><para>
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<emphasis role="bold">Audio proud</emphasis> (volba <option>-oac copy</option>):
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jednoduch<63>. Je mo<6D>n<EFBFBD> vz<76>t extern<72> zvukov<6F> soubor (MP3, WAV) a namultiplexovat
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jej do v<>stupn<70>ho proudu. K tomu pou<6F>ijte volbu
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<option>-audiofile <replaceable>soubor</replaceable></option>.
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</para></listitem>
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</itemizedlist>
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</sect1>
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<sect1 id="menc-feat-enc-libavcodec">
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<title>Enk<EFBFBD>dov<EFBFBD>n<EFBFBD> s rodinou kodek<65> <systemitem class="library">libavcodec</systemitem>
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</title>
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<para>
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<link linkend="ffmpeg"><systemitem class="library">libavcodec</systemitem></link>
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zaji<EFBFBD><EFBFBD>uje jednoduch<63> enk<6E>dov<6F>n<EFBFBD> do mnoha zaj<61>mav<61>ch video a audio form<72>t<EFBFBD>.
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M<EFBFBD><EFBFBD>ete enk<6E>dovat do n<>sleduj<75>c<EFBFBD>ch kodek<65> (v<>ce m<>n<EFBFBD> aktu<74>ln<6C>):
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<informaltable frame="all">
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<tgroup cols="2">
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<thead>
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<row><entry>Jm<EFBFBD>no kodeku</entry><entry>Popis</entry></row>
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</thead>
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<tbody>
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<row><entry>mjpeg</entry><entry>
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Motion JPEG
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</entry></row>
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<row><entry>ljpeg</entry><entry>
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Lossless (bezztr<74>tov<6F>) JPEG
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</entry></row>
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<row><entry>h263</entry><entry>
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H.263
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</entry></row>
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<row><entry>h263p</entry><entry>
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H.263+
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</entry></row>
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<row><entry>mpeg4</entry><entry>
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standardn<64> ISO MPEG-4 (DivX 5, XVID kompatibiln<6C>)
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</entry></row>
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<row><entry>msmpeg4</entry><entry>
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prvotn<74> MPEG-4 varianta od MS, v3 (DivX3)
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</entry></row>
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<row><entry>msmpeg4v2</entry><entry>
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prvotn<74> MPEG-4 od MS, v2 (pou<6F>it<69> ve star<61>ch asf souborech)
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</entry></row>
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<row><entry>wmv1</entry><entry>
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Windows Media Video, verze 1 (WMV7)
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</entry></row>
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<row><entry>wmv2</entry><entry>
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Windows Media Video, verze 2 (WMV8)
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</entry></row>
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<row><entry>rv10</entry><entry>
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star<61> RealVideo kodek
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</entry></row>
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<row><entry>mpeg1video</entry><entry>
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MPEG-1 video
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</entry></row>
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<row><entry>mpeg2video</entry><entry>
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MPEG-2 video
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</entry></row>
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<row><entry>huffyuv</entry><entry>
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bezztr<74>tov<6F> komprese
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</entry></row>
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<row><entry>asv1</entry><entry>
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ASUS Video v1
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</entry></row>
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<row><entry>asv2</entry><entry>
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ASUS Video v2
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</entry></row>
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<row><entry>ffv1</entry><entry>
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bezztr<74>tov<6F> video kodek z FFmpeg
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</entry></row>
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</tbody>
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</tgroup>
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</informaltable>
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Prvn<EFBFBD> pole obsahuje n<>zvy kodek<65>, kter<65> m<><6D>ete p<>i<EFBFBD>adit konfigura<72>n<EFBFBD>mu parametru
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<literal>vcodec</literal>, nap<61>: <option>-lavcopts vcodec=msmpeg4</option>
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</para>
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<informalexample>
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<para>
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P<EFBFBD><EFBFBD>klad, s MJPEG kompres<65>:
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<screen>mencoder dvd://2 -o titul2.avi -ovc lavc -lavcopts vcodec=mjpeg -oac copy</screen>
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</para>
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</informalexample>
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</sect1>
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<sect1 id="menc-feat-enc-images">
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<title>Enk<EFBFBD>dov<EFBFBD>n<EFBFBD> z mno<6E>stv<74> vstupn<70>ch obr<62>zkov<6F>ch soubor<6F> (JPEG, PNG, TGA, SGI)</title>
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<para>
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<application>MEncoder</application> je schopen vytvo<76>it film z jednoho nebo v<>ce
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JPEG, PNG nebo TGA soubor<6F>. Pomoc<6F> jednoduch<63>ho sn<73>mkov<6F>ho kop<6F>rov<6F>n<EFBFBD> m<><6D>e
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vytvo<EFBFBD>it MJPEG (Motion JPEG), MPNG (Motion PNG) nebo MTGA (Motion TGA) soubory.
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</para>
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<orderedlist>
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<title>Vysv<EFBFBD>tlen<EFBFBD> procesu:</title>
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<listitem><para>
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<application>MEncoder</application> <emphasis>dek<EFBFBD>duje</emphasis> vstupn<70>
|
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|
|
soubor(y) pomoc<6F> knihovny <systemitem class="library">libjpeg</systemitem>
|
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|
(kdy<64> dek<65>duje PNG, pou<6F>ije <systemitem class="library">libpng</systemitem>).
|
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</para></listitem>
|
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|
<listitem><para>
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|
Potom <application>MEncoder</application> nakrm<72> dek<65>dovan<61> sn<73>mek do
|
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|
zvolen<65>ho video kompresoru (DivX4, XviD, FFmpeg msmpeg4, atd).
|
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</para></listitem>
|
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</orderedlist>
|
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<formalpara>
|
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|
<title>P<EFBFBD><EFBFBD>klady</title>
|
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|
<para>
|
|
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|
Vysv<EFBFBD>tlen<EFBFBD> volby <option>-mf</option> je v man str<74>nce.
|
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<informalexample>
|
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<para>
|
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|
|
|
Vytvo<EFBFBD>en<EFBFBD> MPEG-4 souboru ze v<>ech JPEG soubor<6F> v aktu<74>ln<6C>m adres<65><73>i:
|
|
|
|
|
<screen>
|
|
|
|
|
mencoder mf://*.jpg -mf w=800:h=600:fps=25:type=jpg -ovc lavc -lavcopts vcodec=mpeg4 -oac copy -o <replaceable>v<EFBFBD>stup.avi</replaceable>
|
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|
</screen>
|
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</para>
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</informalexample>
|
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|
<informalexample>
|
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<para>
|
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|
|
Vytvo<EFBFBD>en<EFBFBD> MPEG-4 souboru z n<>kter<65>ch JPEG soubor<6F> v aktu<74>ln<6C>m adres<65><73>i:
|
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|
|
<screen>
|
|
|
|
|
mencoder mf://<replaceable>sn<EFBFBD>mek001.jpg,sn<73>mek002.jpg</replaceable> -mf w=800:h=600:fps=25:type=jpg -ovc lavc -lavcopts vcodec=mpeg4 -oac copy -o <replaceable>v<EFBFBD>stup.avi</replaceable>
|
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</screen>
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</para>
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|
</informalexample>
|
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|
<informalexample>
|
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<para>
|
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|
Vytvo<EFBFBD>en<EFBFBD> Motion JPEG (MJPEG) souboru ze v<>ech JPEG soubor<6F> v aktu<74>ln<6C>m
|
|
|
|
|
adres<EFBFBD><EFBFBD>i:
|
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|
|
<screen>
|
|
|
|
|
mencoder mf://*.jpg -mf w=800:h=600:fps=25:type=jpg -ovc copy -oac copy -o <replaceable>v<EFBFBD>stup.avi</replaceable>
|
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|
|
|
</screen>
|
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|
</para>
|
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|
</informalexample>
|
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|
<informalexample>
|
|
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|
|
<para>
|
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|
|
Vytvo<EFBFBD>en<EFBFBD> nekomprimovan<61>ho souboru ze v<>ech PNG soubor<6F> v aktu<74>ln<6C>m adres<65><73>i:
|
|
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|
|
<screen>
|
|
|
|
|
mencoder mf:// -mf w=800:h=600:fps=25:type=png -ovc raw -oac copy -o <replaceable>v<EFBFBD>stup.avi</replaceable>
|
|
|
|
|
</screen>
|
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|
</para>
|
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|
</informalexample>
|
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|
|
<note><para>
|
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|
|
<EFBFBD><EFBFBD><EFBFBD>ka mus<75> b<>t cel<65> <20><>slo n<>sobek 4, to je d<>no omezen<65>m RAW RGB AVI form<72>tu.
|
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|
|
</para></note>
|
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|
|
<informalexample>
|
|
|
|
|
<para>
|
|
|
|
|
Vytvo<EFBFBD>en<EFBFBD> Motion PNG (MPNG) souboru ze v<>ech PNG soubor<6F> v aktu<74>ln<6C>m adres<65><73>i:
|
|
|
|
|
<screen>
|
|
|
|
|
mencoder mf://*.png -mf w=800:h=600:fps=25:type=png -ovc copy -oac copy -o <replaceable>v<EFBFBD>stup.avi</replaceable> <!--
|
|
|
|
|
--></screen>
|
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|
|
</para>
|
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|
|
</informalexample>
|
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|
|
<informalexample>
|
|
|
|
|
<para>
|
|
|
|
|
Vytvo<EFBFBD>en<EFBFBD> Motion TGA (MTGA) souboru ze v<>ech TGA soubor<6F> v aktu<74>ln<6C>m adres<65><73>i:
|
|
|
|
|
<screen>
|
|
|
|
|
mencoder mf://*.tga -mf w=800:h=600:fps=25:type=tga -ovc copy -oac copy -o <replaceable>v<EFBFBD>stup.avi</replaceable><!--
|
|
|
|
|
--></screen>
|
|
|
|
|
</para>
|
|
|
|
|
</informalexample>
|
|
|
|
|
|
|
|
|
|
</para>
|
|
|
|
|
</formalpara>
|
|
|
|
|
</sect1>
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
<sect1 id="menc-feat-extractsub">
|
|
|
|
|
<title>Extrakce DVD titulk<6C> do VOBsub souboru</title>
|
|
|
|
|
|
|
|
|
|
<para>
|
|
|
|
|
<application>MEncoder</application> je schopen vyextrahovat titulky z DVD do
|
|
|
|
|
VOBsub form<72>tovan<61>ch soubor<6F>. Ty sest<73>vaj<61> ze dvou soubor<6F> zakon<6F>en<65>ch
|
|
|
|
|
<filename>.idx</filename> a <filename>.sub</filename> a jsou obvykle zabaleny
|
|
|
|
|
v jedin<69>m <filename>.rar</filename> archivu.
|
|
|
|
|
<application>MPlayer</application> je um<75> p<>ehr<68>vat s pomoc<6F> voleb
|
|
|
|
|
<option>-vobsub</option> a <option>-vobsubid</option>.
|
|
|
|
|
</para>
|
|
|
|
|
|
|
|
|
|
<para>
|
|
|
|
|
Zadejte z<>kladn<64> jm<6A>no (<28>ili bez p<><70>pony <filename>.idx</filename> nebo
|
|
|
|
|
<filename>.sub</filename>) v<>stupn<70>ch soubor<6F> pomoc<6F> volby
|
|
|
|
|
<option>-vobsubout</option> a index pro tyto titulky ve zb<7A>vaj<61>c<EFBFBD>ch souborech
|
|
|
|
|
pomoc<EFBFBD> <option>-vobsuboutindex</option>.
|
|
|
|
|
</para>
|
|
|
|
|
|
|
|
|
|
<para>
|
|
|
|
|
Pokud nen<65> vstup z DVD, m<>li byste pou<6F><75>t <option>-ifo</option> pro indikaci
|
|
|
|
|
<filename>.ifo</filename> souboru nutn<74>ho k vytvo<76>en<65> v<>sledn<64>ho
|
|
|
|
|
<filename>.idx</filename> souboru.
|
|
|
|
|
</para>
|
|
|
|
|
|
|
|
|
|
<para>
|
|
|
|
|
Pokud vstup nen<65> z DVD a nem<65>te <filename>.ifo</filename> soubor, budete muset
|
|
|
|
|
pou<EFBFBD><EFBFBD>t volbu <option>-vobsubid</option> k nastaven<65>, pro kter<65> id jazyka se m<>
|
|
|
|
|
vytvo<EFBFBD>it <filename>.idx</filename> soubor.
|
|
|
|
|
</para>
|
|
|
|
|
|
|
|
|
|
<para>
|
|
|
|
|
Ka<EFBFBD>d<EFBFBD>m spu<70>t<EFBFBD>n<EFBFBD>m se p<>idaj<61> b<><62><EFBFBD>c<EFBFBD> titulky pokud soubory <filename>.idx</filename>
|
|
|
|
|
a <filename>.sub</filename> ji<6A> existuj<75>. Tak<61>e byste je m<>li v<>echny odstranit
|
|
|
|
|
d<EFBFBD><EFBFBD>ve ne<6E> za<7A>nete.
|
|
|
|
|
</para>
|
|
|
|
|
|
|
|
|
|
<example>
|
|
|
|
|
<title>Kop<EFBFBD>rov<EFBFBD>n<EFBFBD> dvoj<6F>ch titulk<6C> z DVD b<>hem dvoupr<70>chodov<6F>ho enk<6E>dov<6F>n<EFBFBD></title>
|
|
|
|
|
<screen>
|
|
|
|
|
rm titulky.idx titulky.sub
|
|
|
|
|
mencoder dvd://1 -oac copy -ovc lavc -lavcopts vcodec=mpeg4:vpass=1 -vobsubout titulky -vobsuboutindex 0 -sid 2
|
|
|
|
|
mencoder dvd://1 -oac copy -ovc lavc -lavcopts vcodec=mpeg4:vpass=2 -vobsubout titulky -vobsuboutindex 1 -sid 5<!--
|
|
|
|
|
--></screen>
|
|
|
|
|
</example>
|
|
|
|
|
|
|
|
|
|
<example>
|
|
|
|
|
<title>Kop<EFBFBD>rov<EFBFBD>n<EFBFBD> francouzsk<73>ch titulk<6C> z MPEG souboru</title>
|
|
|
|
|
<screen>
|
|
|
|
|
rm titulky.idx titulky.sub
|
|
|
|
|
mencoder <replaceable>film.mpg</replaceable> -ifo <replaceable>film.ifo</replaceable> -vobsubout titulky -vobsuboutindex 0 -vobsuboutid fr -sid 1<!--
|
|
|
|
|
--></screen>
|
|
|
|
|
</example>
|
|
|
|
|
|
|
|
|
|
</sect1>
|
|
|
|
|
|
|
|
|
|
<sect1 id="aspect">
|
|
|
|
|
<title>Zachov<EFBFBD>n<EFBFBD> pom<6F>ru stran</title>
|
|
|
|
|
<para>
|
|
|
|
|
DVD a SVCD (<28>ili MPEG-1/2) soubory obsahuj<75> hodnotu pom<6F>ru stran,
|
|
|
|
|
popisuj<EFBFBD>c<EFBFBD>, jak by m<>l p<>ehr<68>va<76> <20>k<EFBFBD>lovat video proud, tak<61>e lid<69> nebudou m<>t
|
|
|
|
|
<EFBFBD>i<EFBFBD>at<EFBFBD> hlavy (p<>.: 480x480 + 4:3 = 640x480). Pokud ov<6F>em enk<6E>dujeme do AVI
|
|
|
|
|
(DivX) soubor<6F>, m<>jte na pam<61>ti, <20>e AVI hlavi<76>ky neukl<6B>daj<61> tuto hodnotu.
|
|
|
|
|
P<EFBFBD>e<EFBFBD>k<EFBFBD>lov<EFBFBD>n<EFBFBD> videa je odporn<72> a <20>asov<6F> n<>ro<72>n<EFBFBD>, tak<61>e mus<75> b<>t lep<65><70> zp<7A>sob!
|
|
|
|
|
</para>
|
|
|
|
|
|
|
|
|
|
<para>A zde jej m<>te</para>
|
|
|
|
|
|
|
|
|
|
<para>
|
|
|
|
|
MPEG-4 m<> unik<69>tn<74> vlastnost: video proud m<><6D>e obsahovat sv<73>j po<70>adovan<61> pom<6F>r
|
|
|
|
|
stran. Ano, p<>esn<73> jako MPEG-1/2 (DVD, SVCD) a H.263 soubory. Nane<6E>t<EFBFBD>st<73>,
|
|
|
|
|
<emphasis role="bold"><EFBFBD><EFBFBD>dn<EFBFBD></emphasis> video p<>ehr<68>va<76> nepodporuje tento atribut
|
|
|
|
|
MPEG-4, s v<>jimkou <application>MPlayer</application>u.
|
|
|
|
|
</para>
|
|
|
|
|
|
|
|
|
|
<para>
|
|
|
|
|
Tato vlastnost m<><6D>e b<>t pou<6F>ita pouze s kodekem <systemitem>mpeg4</systemitem> z
|
|
|
|
|
<link linkend="ffmpeg"><systemitem class="library">libavcodec</systemitem></link>u.
|
|
|
|
|
M<EFBFBD>jte na pam<61>ti: a<>koli
|
|
|
|
|
<application>MPlayer</application> korektn<74> p<>ehraje vytvo<76>en<65> soubor, ostatn<74>
|
|
|
|
|
p<EFBFBD>ehr<EFBFBD>va<EFBFBD>e pou<6F>ij<69> <20>patn<74> pom<6F>r stran.
|
|
|
|
|
</para>
|
|
|
|
|
|
|
|
|
|
<para>
|
|
|
|
|
Opravdu byste m<>li o<><6F>znout <20>ern<72> okraje nad a pod filmem.
|
|
|
|
|
Nastudujte si pou<6F>it<69> filtr<74> <systemitem>cropdetect</systemitem> a
|
|
|
|
|
<systemitem>crop</systemitem> v man str<74>nce.
|
|
|
|
|
</para>
|
|
|
|
|
|
|
|
|
|
<para>
|
|
|
|
|
Pou<EFBFBD>it<EFBFBD>
|
|
|
|
|
<screen>mencoder <replaceable>vzorov<EFBFBD>-svcd.mpg</replaceable> -ovc lavc -lavcopts vcodec=mpeg4:autoaspect -vf crop=714:548:0:14 -oac copy -o <replaceable>v<EFBFBD>stup.avi</replaceable></screen>
|
|
|
|
|
</para>
|
|
|
|
|
</sect1>
|
|
|
|
|
|
|
|
|
|
<sect1 id="custommatrices"><title>U<EFBFBD>ivatelsk<EFBFBD> inter/intra matice</title>
|
|
|
|
|
|
|
|
|
|
<para>
|
|
|
|
|
D<EFBFBD>ky t<>to vlastnosti
|
|
|
|
|
<link linkend="ffmpeg"><systemitem class="library">libavcodec</systemitem></link>u
|
|
|
|
|
m<EFBFBD><EFBFBD>ete nastavit u<>ivatelskou inter (I-sn<73>mky/kl<6B><6C>ov<6F> sn<73>mky) a intra
|
|
|
|
|
(P-sn<73>mky/predikovan<61> (rozum<75>jte vypo<70><6F>tan<61>) sn<73>mky) matice. To je podporov<6F>no
|
|
|
|
|
mnoha kodeky:
|
|
|
|
|
<systemitem>mpeg1video</systemitem> a <systemitem>mpeg2video</systemitem>
|
|
|
|
|
jsou hl<68><6C>eny jako funk<6E>n<EFBFBD>.
|
|
|
|
|
</para>
|
|
|
|
|
|
|
|
|
|
<para>
|
|
|
|
|
Typick<EFBFBD> pou<6F>it<69> t<>to vlastnosti je nastaven<65> matic preferovan<61>ch
|
|
|
|
|
<ulink url="http://www.kvcd.net/">KVCD</ulink> specifikacemi.
|
|
|
|
|
</para>
|
|
|
|
|
|
|
|
|
|
<para>
|
|
|
|
|
<emphasis role="bold">Kvantiza<EFBFBD>n<EFBFBD> Matice KVCD "Notch":</emphasis>
|
|
|
|
|
</para>
|
|
|
|
|
|
|
|
|
|
<para>
|
|
|
|
|
Intra:
|
|
|
|
|
<screen>
|
|
|
|
|
8 9 12 22 26 27 29 34
|
|
|
|
|
9 10 14 26 27 29 34 37
|
|
|
|
|
12 14 18 27 29 34 37 38
|
|
|
|
|
22 26 27 31 36 37 38 40
|
|
|
|
|
26 27 29 36 39 38 40 48
|
|
|
|
|
27 29 34 37 38 40 48 58
|
|
|
|
|
29 34 37 38 40 48 58 69
|
|
|
|
|
34 37 38 40 48 58 69 79
|
|
|
|
|
</screen>
|
|
|
|
|
|
|
|
|
|
Inter:
|
|
|
|
|
<screen>
|
|
|
|
|
16 18 20 22 24 26 28 30
|
|
|
|
|
18 20 22 24 26 28 30 32
|
|
|
|
|
20 22 24 26 28 30 32 34
|
|
|
|
|
22 24 26 30 32 32 34 36
|
|
|
|
|
24 26 28 32 34 34 36 38
|
|
|
|
|
26 28 30 32 34 36 38 40
|
|
|
|
|
28 30 32 34 36 38 42 42
|
|
|
|
|
30 32 34 36 38 40 42 44
|
|
|
|
|
</screen>
|
|
|
|
|
</para>
|
|
|
|
|
|
|
|
|
|
<para>
|
|
|
|
|
Pou<EFBFBD>it<EFBFBD>:
|
|
|
|
|
<screen>
|
|
|
|
|
$ mencoder <replaceable>vstup.avi</replaceable> -o <replaceable>v<EFBFBD>stup.avi</replaceable> -oac copy -ovc lavc -lavcopts inter_matrix=...:intra_matrix=...
|
|
|
|
|
</screen>
|
|
|
|
|
</para>
|
|
|
|
|
|
|
|
|
|
<para>
|
|
|
|
|
<screen>
|
|
|
|
|
$ mencoder <replaceable>vstup.avi</replaceable> -ovc lavc -lavcopts
|
|
|
|
|
vcodec=mpeg2video:intra_matrix=8,9,12,22,26,27,29,34,9,10,14,26,27,29,34,37,
|
|
|
|
|
12,14,18,27,29,34,37,38,22,26,27,31,36,37,38,40,26,27,29,36,39,38,40,48,27,
|
|
|
|
|
29,34,37,38,40,48,58,29,34,37,38,40,48,58,69,34,37,38,40,48,58,69,79
|
|
|
|
|
:inter_matrix=16,18,20,22,24,26,28,30,18,20,22,24,26,28,30,32,20,22,24,26,
|
|
|
|
|
28,30,32,34,22,24,26,30,32,32,34,36,24,26,28,32,34,34,36,38,26,28,30,32,34,
|
|
|
|
|
36,38,40,28,30,32,34,36,38,42,42,30,32,34,36,38,40,42,44 -oac copy -o svcd.mpg
|
|
|
|
|
</screen>
|
|
|
|
|
</para>
|
|
|
|
|
</sect1>
|
|
|
|
|
|
|
|
|
|
<sect1 id="menc-feat-dvd-mpeg4">
|
|
|
|
|
<title>Vytvo<EFBFBD>en<EFBFBD> MPEG-4 ("DivX") ripu DVD filmu ve vysok<6F> kvalit<69></title>
|
|
|
|
|
|
|
|
|
|
<para>
|
|
|
|
|
Velmi <20>astou ot<6F>zkou je "Jak mohu vytvo<76>it rip v nejvy<76><79><EFBFBD> mo<6D>n<EFBFBD> kvalit<69> pro
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danou velikost?". Dal<61><6C> ot<6F>zkou je "Jak vytvo<76><6F>m DVD rip v nejvy<76><79><EFBFBD> mo<6D>n<EFBFBD>
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kvalit<69>? Velikost souboru m<> nezaj<61>m<EFBFBD>, chci tu nejvy<76><79><EFBFBD> kvalitu."
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</para>
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<para>
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Druh<75> ot<6F>zka je pon<6F>kud <20>patn<74> polo<6C>en<65>. Konec konc<6E>, pokud je v<>m lhostejn<6A>
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velikost souboru, pro<72> prost<73> nezkop<6F>rujete cel<65> MPEG-2 video proud z DVD?
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Jist<73><74>e va<76>e AVI bude m<>t kolem 5 GB, ale pokud chcete nejvy<76><79><EFBFBD> kvalitu a
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na velikosti nez<65>le<6C><65>, je to jist<73> nejlep<65><70> volba.
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</para>
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<para>
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Ve skute<74>nosti, d<>vodem p<>evodu DVD do MPEG-4 je pr<70>v<EFBFBD> to, <20>e v<>m na velikosti
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souboru <emphasis role="bold">z<EFBFBD>le<EFBFBD><EFBFBD></emphasis>.
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</para>
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<para>
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Je t<><74>k<EFBFBD> nab<61>dnout kucha<68>ku jak vytvo<76>it DVD rip ve velmi vysok<6F> kvalit<69>. Je
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nutn<74> uv<75><76>it mno<6E>stv<74> faktor<6F> a m<>li byste rozum<75>t t<>mto detail<69>m, jinak
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budete asi zklam<61>ni v<>sledkem. N<><4E>e prozkoum<75>me n<>kter<65> z t<>chto v<>c<EFBFBD> a
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pak se pod<6F>v<EFBFBD>me na p<><70>klad. P<>edpokl<6B>d<EFBFBD>me, <20>e pou<6F>ijete
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<systemitem class="library">libavcodec</systemitem> pro enk<6E>dov<6F>n<EFBFBD> videa,
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a<>koli teorie je stejn<6A> i pro ostatn<74> kodeky.
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</para>
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<para>
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Pokud je toho na v<>s moc, asi byste m<>li pou<6F><75>t n<>kter<65> z p<>kn<6B>ch frontend<6E>,
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kter<65> jsou zm<7A>n<EFBFBD>ny v
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<ulink url="http://mplayerhq.hu/homepage/design7/projects.html#mencoder_frontends">sekci MEncoder</ulink>
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na na<6E><61> str<74>nce odvozen<65>ch projekt<6B>.
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Takto budete schopni dosahovat vysoce kvalitn<74>ch rip<69> bez velk<6C>ho p<>em<65><6D>len<65>,
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proto<74>e v<>t<EFBFBD>ina t<>chto n<>stroj<6F> je navr<76>ena tak, aby d<>lala vhodn<64> rozhodnut<75>
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za v<>s.
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</para>
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<sect2 id="menc-feat-dvd-mpeg4-2pass">
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<title>Pevn<EFBFBD> kvantizer vs. dva pr<70>chody</title>
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<para>
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Jsou t<>i p<><70>stupy k enk<6E>dov<6F>n<EFBFBD> videa: pevn<76> datov<6F> tok (CBR), pevn<76> kvantizer
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a dvoupr<70>chodov<6F> (ABR, nebili pr<70>m<EFBFBD>rovan<61> datov<6F> tok).
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</para>
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<para>
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V ka<6B>d<EFBFBD>m z t<>chto re<72>im<69> <systemitem class="library">libavcodec</systemitem>
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rozbije videosn<73>mek na makrobloky 16x16 pixel<65> a potom na ka<6B>d<EFBFBD> makroblok
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aplikuje kvantizer. <20><>m je ni<6E><69><EFBFBD> kvantizer, t<>m je vy<76><79><EFBFBD> kvalita a datov<6F> tok.
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Metoda, kterou <systemitem class="library">libavcodec</systemitem> pou<6F><75>v<EFBFBD> pro
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ur<75>en<65> jak<61> kvantizer pou<6F><75>t pro dan<61> makroblok, se li<6C><69> a je vysoce
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ovlivniteln<6C>. (Toto je extr<74>mn<6D> zjednodu<64>en<65> dan<61>ho procesu, ale je vhodn<64>
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rozum<75>t z<>kladn<64>mu principu.)
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</para>
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<para>
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Pokud nastav<61>te konstantn<74> datov<6F> tok, <systemitem
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class="library">libavcodec</systemitem> bude enk<6E>dovat video tak, <20>e zahod<6F>
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detaily podle pot<6F>eby a jen tolik, aby se udr<64>el pod zadan<61>m datov<6F>m tokem.
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Pokud je v<>m opravdu lhostejn<6A> velikost souboru, m<><6D>ete tak<61> pou<6F><75>t CBR a
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nastavit datov<6F> tok na nekone<6E>no. (V praxi to znamen<65> nastavit hodnotu tak
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vysoko, aby nijak neomezovala, jako 10000 Kbit<69>.) Bez re<72>ln<6C>ho omezen<65>
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datov<6F>ho toku pou<6F>ije <systemitem class="library">libavcodec</systemitem>
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nejni<6E><69><EFBFBD> mo<6D>n<EFBFBD> kvantizer pro ka<6B>d<EFBFBD> makroblok (ten je nastaven pomoc<6F>
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<option>vqmin</option>, v<>choz<6F> je 2). Jakmile nastav<61>te dostate<74>n<EFBFBD> ni<6E><69><EFBFBD>
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datov<6F> tok, tak<61>e je <systemitem class="library">libavcodec</systemitem>
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p<>inucen pou<6F><75>t vy<76><79><EFBFBD> kvantizer, pak t<>m<EFBFBD><6D> jist<73> sn<73><6E><EFBFBD>te kvalitu sv<73>ho videa.
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Abyste se tomu vyhnuli, m<>li byste zv<7A><76>it zmen<65>en<65> videa podle postupu
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popsan<61>ho pozd<7A>ji v t<>to p<><70>ru<72>ce.
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</para>
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<para>
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P<>i konstantn<74>m kvantizeru <systemitem class="library">libavcodec</systemitem>
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pou<6F><75>v<EFBFBD> kvantizer nastaven<65> volbou <option>vqscale</option> na ka<6B>d<EFBFBD> makroblok.
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Pokud chcete maxim<69>ln<6C> kvalitn<74> rip, op<6F>t bez ohledu na datov<6F> tok, m<><6D>ete
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pou<6F><75>t <option>vqscale=2</option>. To povede ke stejn<6A>mu datov<6F>mu toku a PSNR
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(odstup sign<67>l–<EFBFBD>um) jako CBR s <option>vbitrate</option>=infinity a
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v<>choz<6F>m <option>vqmin</option> rovn<76>m 2.
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</para>
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<para>
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Probl<62>m s konstantn<74> kvantizac<61> je ten, <20>e pou<6F><75>v<EFBFBD> zadan<61> kvantizer a<> to dan<61>
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makroblok pot<6F>ebuje <20>i nikoli. Je toti<74> mo<6D>n<EFBFBD> pou<6F><75>t vy<76><79><EFBFBD> kvantizer na
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makroblok bez ob<6F>tov<6F>n<EFBFBD> viditeln<6C> kvality. Pro<72> tedy pl<70>tvat bity s nem<65>stn<74>
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n<>zk<7A>m kvantizerem? V<><56>e CPU m<> tolik cykl<6B>, kolik m<>te <20>asu, ale na harddisku
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m<>te jen ur<75>it<69> po<70>et bit<69>.
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</para>
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<para>
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P<>i dvoupr<70>chodov<6F>m enk<6E>dov<6F>n<EFBFBD> se v prvn<76>m pr<70>chodu projde film jakoby m<>l b<>t
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CBR, ale vlastnosti ka<6B>d<EFBFBD>ho sn<73>mku se zaznamenaj<61> do logu. Tato data jsou pak
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pou<6F>ita p<>i druh<75>m pr<70>chodu pro inteligentn<74> stanoven<65> pou<6F>it<69>ho kvantizeru.
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V rychl<68>ch sc<73>n<EFBFBD>ch nebo sc<73>n<EFBFBD>ch s mal<61>m po<70>tem detail<69> budou <20>ast<73>ji pou<6F><75>v<EFBFBD>ny
|
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vy<76><79><EFBFBD> kvantizery a v pomal<61>ch nebo detailn<6C>ch sc<73>n<EFBFBD>ch zase ni<6E><69><EFBFBD> kvantizery.
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</para>
|
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<para>
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|
Pokud pou<6F>ijete <option>vqscale=2</option>, pl<70>tv<74>te bity. Pokud pou<6F>ijete
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|
<option>vqscale=3</option>, pak nedostanete nejkvalitn<74>j<EFBFBD><6A> mo<6D>n<EFBFBD> rip.
|
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|
Dejme tomu, <20>e ripujete DVD p<>i <option>vqscale=3</option> a
|
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|
v<>sledkem je 1800Kbit. Pokud provedete dvoupr<70>chodov<6F> enk<6E>dov<6F>n<EFBFBD>
|
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|
|
s <option>vbitrate=1800</option>, v<>sledn<64> video bude m<>t <emphasis
|
|
|
|
|
role="bold">vy<76><79><EFBFBD> kvalitu</emphasis> p<>i
|
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|
<emphasis role="bold">stejn<EFBFBD>m datov<6F>m toku</emphasis>.
|
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|
</para>
|
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<para>
|
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|
Jeliko<6B> jsme v<>s nyn<79> p<>esv<73>d<EFBFBD>ili, <20>e dvoupr<70>chodov<6F> re<72>im je spr<70>vn<76> volba,
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skute<74>nou ot<6F>zkou je, jak<61> datov<6F> tok pou<6F><75>t? Odpov<6F><76> je, <20>e nen<65> jedin<69>
|
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odpov<6F><76>. Ide<64>ln<6C> byste m<>li zvolit takov<6F> datov<6F> tok, kter<65> zajist<73> nejlep<65><70>
|
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|
rovnov<6F>hu mezi kvalitou a velikost<73> souboru. Ten bude poka<6B>d<EFBFBD> jin<69>
|
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|
v z<>vislosti na zdrojov<6F>m videu.
|
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|
</para>
|
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|
<para>
|
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|
|
Pokud na velikosti souboru nez<65>le<6C><65>, pak je dobr<62> startovn<76> m<>stek pro rip
|
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|
|
s velmi vysokou kvalitou je kolem 2000 Kbit<69> plus-m<>nus 200 Kbit<69>.
|
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|
Pro rychl<68> ak<61>n<EFBFBD> nebo vysoce detailn<6C> zdrojov<6F> video, nebo m<>te-li velmi
|
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|
|
kritick<63> oko, se budete rozhodovat mezi 2400 nebo 2600.
|
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|
U n<>kter<65>ch DVD nepozn<7A>te rozd<7A>l p<>i 1400 Kbitech. Je vhodn<64> experimentovat
|
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|
se sc<73>nami p<>i r<>zn<7A>ch datov<6F>ch toc<6F>ch, abyste pro to dostali cit.
|
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|
</para>
|
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|
<para>
|
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|
Pokud se sna<6E><61>te o ur<75>itou velikost, budete muset n<>jak spo<70><6F>tat datov<6F> tok.
|
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|
Ale je<6A>t<EFBFBD> p<>edt<64>m mus<75>te zjistit, kolik m<>sta byste m<>li rezervovat pro
|
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|
zvukov<6F>(ou) stopy(u), tak<61>e byste si
|
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|
|
|
<link linkend="menc-feat-dvd-mpeg4-audio">je m<>li ripnout</link> jako prvn<76>.
|
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|
M<><4D>ete si pak spo<70><6F>tat datov<6F> tok pomoc<6F> n<>sleduj<75>c<EFBFBD> rovnice:
|
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|
|
<systemitem>datov<EFBFBD>_tok = (po<70>adovan<61>_velikost_v_Mbajtech - velikost_zvuku_v_Mbajtech) *
|
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|
|
1024 * 1024 / d<>lka_v_sek * 8 / 1000</systemitem>
|
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|
Nap<61><70>klad abyste nacpali dvouhodinov<6F> film na 702MB CD, se 60MB zvukovou
|
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|
|
stopou, bude muset b<>t datov<6F> tok videa:
|
|
|
|
|
<systemitem>(702 - 60) * 1024 * 1024 / (120*60) * 8 / 1000
|
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|
|
|
= 740kbps (kilobit<69> za sekundu)</systemitem>
|
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|
|
</para>
|
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|
|
</sect2>
|
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|
|
<sect2 id="menc-feat-dvd-mpeg4-constraints">
|
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|
|
|
<title>Omezen<EFBFBD> pro efektivn<76> enk<6E>dov<6F>n<EFBFBD></title>
|
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|
<para>
|
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|
Ze sam<61> podstaty komprese typu MPEG vypl<70>vaj<61> ur<75>it<69> omezen<65>, kter<65> byste m<>li
|
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|
ct<63>t, pokud chcete maxim<69>ln<6C> kvalitu.
|
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|
MPEG rozd<7A>l<EFBFBD> video na <20>tverce 16x16 naz<61>van<61> makrobloky, kter<65> se skl<6B>daj<61>
|
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|
ze <20>ty<74> blok<6F> 8x8 jasov<6F> (luma) slo<6C>ky a dvou blok<6F> 8x8 barevn<76> (chroma)
|
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|
slo<6C>ky v polovi<76>n<EFBFBD>m rozli<6C>en<65> (jeden pro osu <20>erven<65>-cyan (modrozelen<65>) a druh<75> pro osu
|
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|
modr<64>-<2D>lut<75>).
|
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|
Dokonce i kdy<64> <20><><EFBFBD>ka a v<><76>ka va<76>eho videa nejsou n<>sobky 16, pou<6F>ije enkod<6F>r
|
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|
dostatek 16x16 makroblok<6F>, aby pokryl celou oblast obrazu a zabere m<>sto
|
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|
nav<61>c, kter<65> p<>ijde vnive<76>.
|
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|
Tak<61>e chcete-li maximalizovat kvalitu p<>i dan<61> velikosti souboru, nen<65> dobr<62>
|
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|
n<>pad pou<6F><75>vat rozm<7A>ry kter<65> nejsou n<>sobky 16.
|
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|
|
</para>
|
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|
<para>
|
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|
V<>t<EFBFBD>ina DVD m<> tak<61> r<>zn<7A> velk<6C> <20>ern<72> okraje videa. Ponech<63>n<EFBFBD> t<>chto ploch
|
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|
m<><6D>e r<>zn<7A>m zp<7A>sobem sn<73><6E>it kvalitu.
|
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|
|
|
</para>
|
|
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|
<orderedlist>
|
|
|
|
|
<listitem>
|
|
|
|
|
<para>
|
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|
|
|
Komprese typu MPEG je rovn<76><6E> velmi z<>visl<73> na plo<6C>n<EFBFBD>ch frekven<65>n<EFBFBD>ch
|
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|
|
|
transformac<61>ch, konkr<6B>tn<74> Diskr<6B>tn<74> Kosinov<6F> Transformaci (DCT), kter<65> se
|
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|
|
|
podob<6F> Fourierov<6F> transformaci. Tento druh enk<6E>dov<6F>n<EFBFBD> je efektivn<76> na
|
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|
|
|
reprezentaci opakuj<75>c<EFBFBD>ch se vzor<6F> a pozvoln<6C> p<>echody, ale m<> pot<6F><74>e s ostr<74>mi
|
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|
p<>echody. Chcete-li je enk<6E>dovat, mus<75>te pou<6F><75>t mnoho bit<69>, jinak se objev<65>
|
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|
|
|
artefakty zn<7A>m<EFBFBD> jako krou<6F>kov<6F>n<EFBFBD>.
|
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|
|
|
</para>
|
|
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|
|
<para>
|
|
|
|
|
Frekven<65>n<EFBFBD> transformace (DCT) je provedena zvlṻ pro ka<6B>d<EFBFBD> makroblok
|
|
|
|
|
(ve skute<74>nosti na ka<6B>d<EFBFBD> blok), tak<61>e probl<62>m nastane pouze tehdy, je-li ostr<74>
|
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|
|
p<>echod uvnit<69> bloku. Pokud va<76>e <20>ern<72> okraje za<7A><61>naj<61> p<>esn<73> na hranic<69>ch
|
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|
n<>sobk<62> 16 pixel<65>, pak to nen<65> probl<62>m. <20>ern<72> okraje jsou v<>ak na DVD jen
|
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|
m<>lokdy p<>kn<6B> um<75>st<73>ny, tak<61>e je v praxi budete muset v<>dy odstranit, abyste
|
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|
|
se vyhnuli tomuto probl<62>mu.
|
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|
|
</para>
|
|
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|
|
</listitem>
|
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|
|
</orderedlist>
|
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|
<para>
|
|
|
|
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Nav<61>c k plo<6C>n<EFBFBD> frekven<65>n<EFBFBD>m transformac<61>m pou<6F><75>v<EFBFBD> komprese typu MPEG vektory
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pohybu k popisu zm<7A>n od jednoho sn<73>mku ke druh<75>mu. Vektory pohybu p<>irozen<65>
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pracuj<75> m<>n<EFBFBD> efektivn<76> s nov<6F>m obsahem p<>ich<63>zej<65>c<EFBFBD>m zpoza okraj<61> sn<73>mku,
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proto<74>e ten nebyl p<><70>tomen na p<>edchoz<6F>m sn<73>mku. Dokud se obraz roz<6F>i<EFBFBD>uje
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sm<73>rem k okraj<61>m sn<73>mku, nemaj<61> s t<>m vektory pohybu <20><>dn<64> probl<62>m, ale
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jsou-li zde <20>ern<72> okraje, m<><6D>e probl<62>m nastat:
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</para>
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<orderedlist continuation="continues">
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<listitem>
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<para>
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Komprese typu MPEG ukl<6B>d<EFBFBD> pro ka<6B>d<EFBFBD> makroblok vektor, identifikuj<75>c<EFBFBD> kter<65>
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<20><>st p<>edchoz<6F>ho obr<62>zku by m<>la b<>t zkop<6F>rov<6F>na onoho makrobloku jako z<>klad
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pro predikci n<>sleduj<75>c<EFBFBD>ho sn<73>mku. Pouze zb<7A>vaj<61>c<EFBFBD> odli<6C>nosti mus<75> b<>t
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enk<6E>dov<6F>ny. Pokud makroblok p<>esahuje okraj obr<62>zku a obsahuje <20><>st <20>ern<72>ho
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okraje, vektory pohybu z ostatn<74>ch <20><>st<73> obr<62>zku p<>ep<65><70><EFBFBD> <20>ern<72> okraj.
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To znamen<65> mnoho bit<69> spot<6F>ebovan<61>ch bu<62> na znovuza<7A>ern<72>n<EFBFBD>, nebo se (sp<73><70>)
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vektory pohybu nepou<6F>ij<69> v<>bec a v<>echny zm<7A>ny v tomto makrobloku se budou
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k<>dovat p<><70>mo. Jin<69>mi slovy se velmi sn<73><6E><EFBFBD> efektivita enk<6E>dov<6F>n<EFBFBD>.
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</para>
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<para>
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Tento probl<62>m nast<73>v<EFBFBD> op<6F>t jen v p<><70>pad<61>, <20>e <20>ern<72> okraje neza<7A><61>naj<61> na lince
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jej<65><6A> pozice je n<>sobkem 16.
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</para>
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</listitem>
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<listitem>
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<para>
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Nakonec zde m<>me makroblok uvnit<69> obr<62>zku do n<>j<EFBFBD> se posunuje objekt z okraje
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obr<62>zku. K<>dov<6F>n<EFBFBD> typu MPEG neum<75> <20><>ct "zkop<6F>ruj to co je na obr<62>zku, ale ne
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<20>ern<72> okraj." Tak<61>e se zkop<6F>ruje i <20>ern<72> okraj a spot<6F>ebuje se spousta bit<69>
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na enk<6E>dov<6F>n<EFBFBD> t<> <20><>sti obr<62>zku, kter<65> tu m<>la b<>t.
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</para>
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<para>
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Pokud se obr<62>zek dostane <20>pln<6C> ven z enk<6E>dovan<61> oblasti, m<> MPEG speci<63>ln<6C>
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optimalizace pro opakovan<61> kop<6F>rov<6F>n<EFBFBD> pixel<65> na okraj obr<62>zku pokud p<>ijde
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vektor pohybu zven<65><6E> enk<6E>dovan<61> oblasti. Tato vlastnost bude k ni<6E>emu, pokud
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m<> film <20>ern<72> okraje. Na rozd<7A>l od probl<62>m<EFBFBD> 1 a 2 zde um<75>st<73>n<EFBFBD> okraj<61> na
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n<>sobky 16 nepom<6F><6D>e.
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</para>
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</listitem>
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<listitem>
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<para>
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Navzdory tomu, <20>e okraje jsou <20>pln<6C> <20>ern<72> a nikdy se nem<65>n<EFBFBD>, je zde v<>dy
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alespo<70> minim<69>ln<6C> datov<6F> tok spot<6F>ebovan<61> na v<>t<EFBFBD><74> mno<6E>stv<74> makroblok<6F>.
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</para>
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</listitem>
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</orderedlist>
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<para>
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Ze v<>ech t<>chto d<>vod<6F> doporu<72>ujeme zcela odstranit <20>ern<72> okraje. D<>le, pokud
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je na okraji obr<62>zku oblast se <20>umem/zkreslen<65>m, jej<65>m odst<73>i<EFBFBD>en<65>m se je<6A>t<EFBFBD>
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zv<7A><76><EFBFBD> efektivita enk<6E>dov<6F>n<EFBFBD>. Videofiln<6C> purist<73>, kte<74><65> cht<68>j<EFBFBD> z<>stat tak
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bl<62>zko origin<69>lu, jak je to jen mo<6D>n<EFBFBD>, mohou protestovat proti tomuto o<>ez<65>n<EFBFBD>,
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ale pokud nehodl<64>te enk<6E>dovat s konstantn<74>m kvantizerem, kvalita kterou
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dostanete d<>ky o<>ez<65>n<EFBFBD> znateln<6C> p<>ev<65><76><EFBFBD> mno<6E>stv<74> ztracen<65>ch informac<61> na
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okraj<61>ch.
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</para>
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</sect2>
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<sect2 id="menc-feat-dvd-mpeg4-crop">
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<title>O<EFBFBD>ez<EFBFBD>v<EFBFBD>n<EFBFBD> a <20>k<EFBFBD>lov<6F>n<EFBFBD></title>
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2005-05-09 05:43:21 +00:00
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<para>
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P<>ipome<6D>me z p<>edchoz<6F> <20><>sti, <20>e kone<6E>n<EFBFBD> velikost obr<62>zku by m<>la m<>t
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jak <20><><EFBFBD>ku, tak v<><76>ku beze zbytku d<>litelnou 16, <20>eho<68> m<><6D>ete dos<6F>hnout
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pomoc<6F> o<>ez<65>n<EFBFBD>, <20>k<EFBFBD>lov<6F>n<EFBFBD>, nebo kombinac<61> obou.
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</para>
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<para>
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P<>i o<>ez<65>v<EFBFBD>n<EFBFBD> byste se m<>li dr<64>et n<>kolika z<>sad, abyste p<>ede<64>li po<70>kozen<65>
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sv<73>ho filmu.
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Norm<72>ln<6C> YUV form<72>t 4:2:0, ukl<6B>d<EFBFBD> barvonosnou (chroma) informaci
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podvzorkovanou, <20>ili hustota vzorkov<6F>n<EFBFBD> barvy je polovi<76>n<EFBFBD> oproti jasov<6F>
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(<28>ernob<6F>l<EFBFBD>) slo<6C>ce v obou sm<73>rech.
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Prohl<68>dn<64>te si tento diagram, kde L ozna<6E>uje vzorkovac<61> body jasu a C
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barvy.
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</para>
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<informaltable>
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<?dbhtml table-width="40%" ?>
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<?dbfo table-width="40%" ?>
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<tgroup cols="8" align="center">
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<colspec colnum="1" colname="col1"/>
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<colspec colnum="2" colname="col2"/>
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<colspec colnum="3" colname="col3"/>
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<colspec colnum="4" colname="col4"/>
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<colspec colnum="5" colname="col5"/>
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<colspec colnum="6" colname="col6"/>
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<colspec colnum="7" colname="col7"/>
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<colspec colnum="8" colname="col8"/>
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<spanspec spanname="spa1-2" namest="col1" nameend="col2"/>
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<spanspec spanname="spa3-4" namest="col3" nameend="col4"/>
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<spanspec spanname="spa5-6" namest="col5" nameend="col6"/>
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<spanspec spanname="spa7-8" namest="col7" nameend="col8"/>
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<tbody>
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<row>
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<entry>L</entry>
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<entry>L</entry>
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<entry>L</entry>
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<entry>L</entry>
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<entry>L</entry>
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<entry>L</entry>
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<entry>L</entry>
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<entry>L</entry>
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</row>
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<row>
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<entry spanname="spa1-2">C</entry>
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<entry spanname="spa3-4">C</entry>
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<entry spanname="spa5-6">C</entry>
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<entry spanname="spa7-8">C</entry>
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</row>
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<row>
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<entry>L</entry>
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<entry>L</entry>
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<entry>L</entry>
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<entry>L</entry>
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<entry>L</entry>
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<entry>L</entry>
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<entry>L</entry>
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<entry>L</entry>
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</row>
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<row>
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<entry>L</entry>
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<entry>L</entry>
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<entry>L</entry>
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<entry>L</entry>
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<entry>L</entry>
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<entry>L</entry>
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<entry>L</entry>
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<entry>L</entry>
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</row>
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<row>
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<entry spanname="spa1-2">C</entry>
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<entry spanname="spa3-4">C</entry>
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<entry spanname="spa5-6">C</entry>
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<entry spanname="spa7-8">C</entry>
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</row>
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<row>
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<entry>L</entry>
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<entry>L</entry>
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<entry>L</entry>
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<entry>L</entry>
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<entry>L</entry>
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<entry>L</entry>
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<entry>L</entry>
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<entry>L</entry>
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</row>
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</tbody>
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</tgroup>
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</informaltable>
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<para>
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Jak vid<69>te, <20><>dky i sloupce obr<62>zku se p<>irozen<65> p<>ruj<75>. P<>i o<>ez<65>v<EFBFBD>n<EFBFBD> tedy
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<emphasis>mus<EFBFBD></emphasis> b<>t hodnoty odsazen<65> i rozm<7A>r<EFBFBD> sud<75> <20><>sla.
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Pokud nejsou, nebude se barvonosn<73> informace zpr<70>vn<76> kr<6B>t s jasovou.
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Teoreticky lze st<73><74>hat s lich<63>m odsazen<65>m, ale to vy<76>aduje p<>evzorkov<6F>n<EFBFBD>
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barvy, co<63> je potenci<63>ln<6C> ztr<74>tov<6F> <20>kon a nen<65> podporov<6F>n filtrem crop.
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</para>
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<para>
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D<>le, prokl<6B>dan<61> video je vzorkov<6F>no takto:
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</para>
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<informaltable>
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<?dbhtml table-width="80%" ?>
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<?dbfo table-width="80%" ?>
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<tgroup cols="16" align="center">
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<colspec colnum="1" colname="col1"/>
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<colspec colnum="2" colname="col2"/>
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<colspec colnum="3" colname="col3"/>
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<colspec colnum="4" colname="col4"/>
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<colspec colnum="5" colname="col5"/>
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<colspec colnum="6" colname="col6"/>
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<colspec colnum="7" colname="col7"/>
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<colspec colnum="8" colname="col8"/>
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<colspec colnum="9" colname="col9"/>
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<colspec colnum="10" colname="col10"/>
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<colspec colnum="11" colname="col11"/>
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<colspec colnum="12" colname="col12"/>
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<colspec colnum="13" colname="col13"/>
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<colspec colnum="14" colname="col14"/>
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<colspec colnum="15" colname="col15"/>
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<colspec colnum="16" colname="col16"/>
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<spanspec spanname="spa1-2" namest="col1" nameend="col2"/>
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<spanspec spanname="spa3-4" namest="col3" nameend="col4"/>
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<spanspec spanname="spa5-6" namest="col5" nameend="col6"/>
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<spanspec spanname="spa7-8" namest="col7" nameend="col8"/>
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<spanspec spanname="spa9-10" namest="col9" nameend="col10"/>
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<spanspec spanname="spa11-12" namest="col11" nameend="col12"/>
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<spanspec spanname="spa13-14" namest="col13" nameend="col14"/>
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<spanspec spanname="spa15-16" namest="col15" nameend="col16"/>
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<tbody>
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<row>
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|
<entry namest="col1" nameend="col8">Horn<EFBFBD> p<>lsn<73>mek</entry>
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<entry namest="col9" nameend="col16">Spodn<EFBFBD> p<>lsn<73>mek</entry>
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</row>
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<row>
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<entry>L</entry>
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<entry>L</entry>
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<entry>L</entry>
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<entry>L</entry>
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<entry>L</entry>
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<entry>L</entry>
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<entry>L</entry>
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<entry>L</entry>
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<entry></entry>
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<entry></entry>
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<entry></entry>
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<entry></entry>
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<entry></entry>
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<entry></entry>
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</row>
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<row>
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<entry spanname="spa1-2">C</entry>
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<entry spanname="spa3-4">C</entry>
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<entry spanname="spa5-6">C</entry>
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<entry spanname="spa7-8">C</entry>
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<entry></entry>
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<entry></entry>
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</row>
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<row>
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<entry></entry>
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<entry></entry>
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<entry></entry>
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<entry></entry>
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<entry></entry>
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<entry></entry>
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<entry></entry>
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<entry></entry>
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<entry>L</entry>
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<entry>L</entry>
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<entry>L</entry>
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<entry>L</entry>
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<entry>L</entry>
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<entry>L</entry>
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<entry>L</entry>
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<entry>L</entry>
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</row>
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<row>
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<entry>L</entry>
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<entry>L</entry>
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<entry>L</entry>
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<entry>L</entry>
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<entry>L</entry>
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<entry>L</entry>
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<entry>L</entry>
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<entry>L</entry>
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<entry></entry>
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<entry></entry>
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<entry></entry>
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<entry></entry>
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<entry></entry>
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<entry></entry>
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<entry></entry>
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<entry></entry>
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</row>
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<row>
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<entry></entry>
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<entry></entry>
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<entry></entry>
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<entry></entry>
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<entry></entry>
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<entry></entry>
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<entry></entry>
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<entry></entry>
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<entry spanname="spa9-10">C</entry>
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<entry spanname="spa11-12">C</entry>
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<entry spanname="spa13-14">C</entry>
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<entry spanname="spa15-16">C</entry>
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</row>
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<row>
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<entry></entry>
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<entry></entry>
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<entry></entry>
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<entry></entry>
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<entry></entry>
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<entry></entry>
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<entry></entry>
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<entry></entry>
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<entry>L</entry>
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<entry>L</entry>
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<entry>L</entry>
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<entry>L</entry>
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<entry>L</entry>
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<entry>L</entry>
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<entry>L</entry>
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<entry>L</entry>
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</row>
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<row>
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<entry>L</entry>
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<entry>L</entry>
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<entry>L</entry>
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<entry>L</entry>
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<entry>L</entry>
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<entry>L</entry>
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<entry>L</entry>
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<entry>L</entry>
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<entry></entry>
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<entry></entry>
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<entry></entry>
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<entry></entry>
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<entry></entry>
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<entry></entry>
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<entry></entry>
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<entry></entry>
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</row>
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<row>
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<entry spanname="spa1-2">C</entry>
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<entry spanname="spa3-4">C</entry>
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<entry spanname="spa5-6">C</entry>
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<entry spanname="spa7-8">C</entry>
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<entry></entry>
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<entry></entry>
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<entry></entry>
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<entry></entry>
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<entry></entry>
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<entry></entry>
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<entry></entry>
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<entry></entry>
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</row>
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<row>
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<entry></entry>
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<entry></entry>
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<entry></entry>
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<entry></entry>
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<entry></entry>
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<entry></entry>
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<entry></entry>
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<entry></entry>
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<entry>L</entry>
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<entry>L</entry>
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<entry>L</entry>
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<entry>L</entry>
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<entry>L</entry>
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<entry>L</entry>
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<entry>L</entry>
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<entry>L</entry>
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</row>
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<row>
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<entry>L</entry>
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<entry>L</entry>
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<entry>L</entry>
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<entry>L</entry>
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<entry>L</entry>
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<entry>L</entry>
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<entry>L</entry>
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<entry>L</entry>
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<entry></entry>
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<entry></entry>
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<entry></entry>
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<entry></entry>
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<entry></entry>
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<entry></entry>
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<entry></entry>
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<entry></entry>
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</row>
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<row>
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<entry></entry>
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<entry></entry>
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<entry></entry>
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<entry></entry>
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<entry></entry>
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<entry></entry>
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<entry></entry>
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<entry></entry>
|
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<entry spanname="spa9-10">C</entry>
|
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<entry spanname="spa11-12">C</entry>
|
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<entry spanname="spa13-14">C</entry>
|
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<entry spanname="spa15-16">C</entry>
|
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</row>
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<row>
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<entry></entry>
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<entry></entry>
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<entry></entry>
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<entry></entry>
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<entry></entry>
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<entry></entry>
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<entry></entry>
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<entry></entry>
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<entry>L</entry>
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<entry>L</entry>
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<entry>L</entry>
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<entry>L</entry>
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<entry>L</entry>
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<entry>L</entry>
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<entry>L</entry>
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<entry>L</entry>
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</row>
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</tbody>
|
|
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|
|
</tgroup>
|
|
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|
|
</informaltable>
|
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|
|
<para>
|
|
|
|
|
Jak vid<69>te, tak se vzor opakuje ka<6B>d<EFBFBD> 4 <20><>dky, tak<61>e p<>i o<>ezu prokl<6B>dan<61>ho
|
|
|
|
|
videa mus<75> b<>t odsazen<65> v ose y a v<><76>ka beze zbytku deliteln<6C> 4.
|
|
|
|
|
</para>
|
|
|
|
|
|
2005-04-20 07:41:24 +00:00
|
|
|
|
<para>
|
|
|
|
|
Nativn<76> DVD rozli<6C>en<65> je 720x480 pro NTSC a 720x576 pro PAL, ale je zde je<6A>t<EFBFBD>
|
|
|
|
|
p<><70>znak pom<6F>ru stran, kter<65> ud<75>v<EFBFBD>, zda se jedn<64> o obrazovku (full-screen)(4:3),
|
|
|
|
|
nebo <20>iroko<6B>hl<68> film (wide-screen)(16:9). Mnoho (jestli ne v<>t<EFBFBD>ina)
|
|
|
|
|
<20>iroko<6B>hl<68>ch DVD nen<65> p<>esn<73> 16:9, ale bude bu<62> 1.85:1 anebo 2.35:1
|
|
|
|
|
(cinescope). To znamen<65>, <20>e zde budou ve videu <20>ern<72> okraje, kter<65> bude nutn<74>
|
|
|
|
|
odst<73>ihnout.
|
|
|
|
|
</para>
|
|
|
|
|
|
|
|
|
|
<para>
|
|
|
|
|
<application>MPlayer</application> poskytuje filtr pro detekci pot<6F>ebn<62>ho
|
|
|
|
|
o<>ezu, kter<65> stanov<6F> o<>ezov<6F> obd<62>ln<6C>k (<option>-vf cropdetect</option>).
|
2005-05-09 05:43:21 +00:00
|
|
|
|
Spus<75>te <application>MPlayer</application> s volbou
|
|
|
|
|
<option>-vf cropdetect</option> a on v<>m vyp<79><70>e nastaven<65> filtru crop pro
|
|
|
|
|
o<>ez<65>n<EFBFBD> okraj<61>.
|
|
|
|
|
M<>li byste nechat b<><62>et film tak dlouho, dokud nen<65> pou<6F>ita cel<65> plocha
|
|
|
|
|
obr<62>zku, abyste dostali spr<70>vn<76> hodnoty crop.
|
|
|
|
|
</para>
|
|
|
|
|
|
|
|
|
|
<para>
|
|
|
|
|
Pak otestujte z<>skan<61> hodnoty z p<><70>kazov<6F>ho <20><>dku
|
|
|
|
|
<application>MPlayer</application>u vypisovan<61> <option>cropdetect</option>em
|
|
|
|
|
a upravte obd<62>ln<6C>k podle pot<6F>eby.
|
|
|
|
|
V tom v<>m pom<6F><6D>e filtr <option>rectangle</option>, kter<65> interaktivn<76>
|
|
|
|
|
nastavit obd<62>ln<6C>k pro v<><76> film.
|
|
|
|
|
Nezapome<6D>te zachovat v<><76>e uveden<65> doporu<72>en<65>, abyste nepo<70>kodili barevnou
|
|
|
|
|
mapu.
|
|
|
|
|
</para>
|
|
|
|
|
|
|
|
|
|
<para>
|
|
|
|
|
<20>k<EFBFBD>lov<6F>n<EFBFBD> je obvykle nevhodn<64>.
|
|
|
|
|
<20>k<EFBFBD>lov<6F>n<EFBFBD> prokl<6B>dan<61>ho videa je obt<62><74>n<EFBFBD> a pokud chcete zachovat prokl<6B>d<EFBFBD>n<EFBFBD>,
|
|
|
|
|
m<>li byste se mu <20>pln<6C> vyhnout.
|
|
|
|
|
Pokud mebudete <20>k<EFBFBD>lovat, ale budete cht<68>t pou<6F><75>vat rozm<7A>ry v n<>sobc<62>ch 16,
|
|
|
|
|
budete muset o<><6F>znout i <20><>st obrazu.
|
|
|
|
|
Neponech<63>vejte ani mal<61> <20>ern<72> okraje, jeliko<6B> se velmi <20>patn<74> k<>duj<75>!
|
|
|
|
|
</para>
|
|
|
|
|
|
|
|
|
|
<para>
|
2005-04-20 07:41:24 +00:00
|
|
|
|
Proto<74>e MPEG-4 pou<6F><75>v<EFBFBD> makrobloky 16x16, m<>li byste se ujistit, <20>e oba rozm<7A>ry
|
|
|
|
|
videa jsou n<>sobkem 16, jinak sn<73><6E><EFBFBD>te kvalitu, zvlṻ p<>i n<>zk<7A>ch datov<6F>ch
|
|
|
|
|
toc<6F>ch. M<><4D>ete to zajistit zaokrouhlen<65>m <20><><EFBFBD>ky a v<><76>ky o<>ezov<6F>ho obd<62>ln<6C>ku
|
2005-05-09 05:43:21 +00:00
|
|
|
|
dol<6F> na nejbli<6C><69><EFBFBD> n<>sobek 16.
|
|
|
|
|
Jak jsme ji<6A> <20>ekli, m<>li byste p<>i o<>ez<65>v<EFBFBD>n<EFBFBD> zv<7A><76>it odsazen<65>
|
2005-04-20 07:41:24 +00:00
|
|
|
|
(offset) v ose y o polovinu rozd<7A>lu mezi starou a novou v<><76>kou, tak<61>e bude
|
|
|
|
|
v<>sledn<64> video br<62>no ze st<73>edu sn<73>mku. Z d<>vodu principu vzorkov<6F>n<EFBFBD> DVD videa
|
|
|
|
|
se ujist<73>te, <20>e je odsazen<65> sud<75> <20><>slo. (Popravd<76>, p<>ijm<6A>te jako pravidlo,
|
|
|
|
|
nikdy nepou<6F><75>vat lich<63> hodnoty pro jak<61>koli z parametr<74> p<>i o<>ez<65>v<EFBFBD>n<EFBFBD> a
|
|
|
|
|
<20>k<EFBFBD>lov<6F>n<EFBFBD> videa.) Pokud nechcete zahodit t<>ch n<>kolik pixel<65> nav<61>c, m<><6D>ete
|
|
|
|
|
m<>sto toho rad<61>ji zm<7A>nit velikost videa (<28>k<EFBFBD>lovat). Na to se pod<6F>v<EFBFBD>me
|
|
|
|
|
v p<><70>kladu n<><6E>e.
|
|
|
|
|
V praxi m<><6D>ete nechat filtr <option>cropdetect</option> ud<75>lat v<>echnu pr<70>ci
|
|
|
|
|
zm<7A>n<EFBFBD>nou v<><76>e, jeliko<6B> m<> voliteln<6C> parametr <option>round</option>
|
|
|
|
|
(zaokrouhlen<65>), jeho<68> v<>choz<6F> hodnota je 16.
|
|
|
|
|
</para>
|
|
|
|
|
|
|
|
|
|
<para>
|
|
|
|
|
Rovn<76><6E> bu<62>te opatrn<72> na "nap<61>l <20>ern<72>" pixely na okraj<61>ch. V<>dy je rovn<76><6E>
|
|
|
|
|
odst<73>ihn<68>te, jinak zde budete pl<70>tvat bity, kter<65> m<><6D>ete pou<6F><75>t jinde.
|
|
|
|
|
</para>
|
|
|
|
|
|
|
|
|
|
<para>
|
|
|
|
|
Pot<6F> co provedete v<>e, co jsme si doposud <20>ekli, budete m<>t video, kter<65> asi
|
|
|
|
|
nebude pr<70>v<EFBFBD> 1.85:1 nebo 2.35:1, ale n<>kde pobl<62><6C>. M<><4D>ete spo<70><6F>tat nov<6F> pom<6F>r
|
|
|
|
|
stran ru<72>n<EFBFBD>, ale <application>MEncoder</application> nab<61>z<EFBFBD> volbu pro
|
2005-04-20 09:22:27 +00:00
|
|
|
|
<systemitem class="library">libavcodec</systemitem> naz<61>vanou <option>autoaspect</option>,
|
2005-04-20 07:41:24 +00:00
|
|
|
|
kter<65> to za v<>s ud<75>l<EFBFBD>. Nezv<7A>t<EFBFBD>ujte video jen proto, abyste dos<6F>hli <20>tvercov<6F>ch
|
|
|
|
|
pixel<65>, pokud je v<>m mil<69> m<>sto na disku. <20>k<EFBFBD>lov<6F>n<EFBFBD> by m<>lo b<>t provedeno p<>i
|
|
|
|
|
p<>ehr<68>v<EFBFBD>n<EFBFBD>, kdy p<>ehr<68>va<76> pou<6F>ije pom<6F>r stran ulo<6C>en<65> v AVI pro zaji<6A>t<EFBFBD>n<EFBFBD>
|
|
|
|
|
spr<70>vn<76>ho rozli<6C>en<65>.
|
|
|
|
|
Nane<6E>t<EFBFBD>st<73> ne v<>echny p<>ehr<68>va<76>e uplat<61>uj<75> tuto auto<74>k<EFBFBD>lovac<61> informaci,
|
|
|
|
|
tak<61>e m<><6D>ete p<>ece jen cht<68>t <20>k<EFBFBD>lovat.
|
|
|
|
|
</para>
|
|
|
|
|
|
|
|
|
|
<para>
|
|
|
|
|
Nejd<6A><64>v byste si m<>li spo<70><6F>tat enk<6E>dovan<61> pom<6F>r stran:
|
|
|
|
|
<systemitem>PSo = (<28>o x (PSa / PRdvd )) / Vo</systemitem>
|
|
|
|
|
<itemizedlist>
|
|
|
|
|
<title>kde:</title>
|
|
|
|
|
<listitem><para>
|
|
|
|
|
<20>o a Vo jsou <20><><EFBFBD>ka a v<><76>ka o<>ezan<61>ho videa,
|
|
|
|
|
</para></listitem>
|
|
|
|
|
<listitem><para>
|
|
|
|
|
PRdvd je pom<6F>r pixel<65> v DVD, kter<65> je roven 1.25=(720/576) pro DVD
|
|
|
|
|
v PALu a 1.5=(720/480) pro DVD v NTSC,
|
|
|
|
|
</para></listitem>
|
|
|
|
|
</itemizedlist>
|
|
|
|
|
</para>
|
|
|
|
|
|
|
|
|
|
<para>
|
|
|
|
|
Pak si m<><6D>ete spo<70><6F>tat rozli<6C>en<65> X a Y podle ur<75>it<69>ho faktoru kvality komprese
|
|
|
|
|
(CQ):
|
|
|
|
|
<systemitem>RozY = INT(SQRT( 1000*Datov<6F>_tok/25/PSo/CQ )/16) * 16</systemitem>
|
|
|
|
|
<systemitem>RozX = INT( RozY * PSo / 16) * 16</systemitem>
|
|
|
|
|
</para>
|
|
|
|
|
|
|
|
|
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<para>
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|
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Dob<6F>e, ale co je ten CQ?
|
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CQ odpov<6F>d<EFBFBD> po<70>tu bit<69> na pixel a na sn<73>mek v zak<61>dov<6F>n<EFBFBD>. Jin<69>mi slovy, <20><>m
|
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vy<76><79><EFBFBD> je CQ, t<>m ni<6E><69><EFBFBD> je <20>ance uvid<69>t enk<6E>dovac<61> artefakty.
|
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Pokud ov<6F>em m<>te c<>lov<6F> rozm<7A>r va<76>eho filmu (1 nebo 2 CD nap<61><70>klad), m<>te jen
|
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omezen<65> mno<6E>stv<74> bit<69>, kter<65> m<><6D>ete spot<6F>ebovat; tak<61>e je nutn<74> naj<61>t vhodn<64>
|
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kompromis mezi komprimovatelnost<73> a kvalitou.
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|
</para>
|
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<para>
|
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CQ z<>vis<69> jak na datov<6F>m toku, tak na rozli<6C>en<65> filmu. Abyste zv<7A><76>ili CQ,
|
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obvykle zmen<65><6E>te dan<61> film, tak<61>e je datov<6F> tok spo<70><6F>t<EFBFBD>n ve funkci c<>lov<6F>
|
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velikosti a d<>lky filmu, kter<65> jsou konstantn<74>.
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CQ pod 0.18 obvykle vede k velmi <20>tvere<72>kovan<61>mu obrazu, proto<74>e nen<65> dostatek
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bit<69> pro zak<61>dov<6F>n<EFBFBD> informac<61> ka<6B>d<EFBFBD>ho makrobloku (MPEG4, stejn<6A> jako mnoho
|
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jin<69>ch kodek<65> seskupuje pixely do blok<6F> p<>i komprimaci obr<62>zku; pokud nen<65>
|
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dostatek bit<69>, jsou viditeln<6C> hranice t<>chto blok<6F>).
|
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Proto je rozumn<6D> volit CQ v rozmez<65> 0.20 a<> 0.22 pro rip na 1 CD a
|
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0.26 a<> 0.28 pro 2 CD.
|
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|
</para>
|
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<para>
|
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Pros<6F>me berte v potaz, <20>e CQ je jen informa<6D>n<EFBFBD> pom<6F>cka z<>visej<65>c<EFBFBD> na
|
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|
|
enk<6E>dovan<61>m obsahu. CQ okolo 0.18 m<><6D>e b<>t dostate<74>n<EFBFBD> dobr<62> pro Bergmana,
|
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|
na rozd<7A>l od filmu jako je Matrix, kter<65> obsahuje mnoho rychl<68>ch sc<73>n.
|
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Na druhou stranu je zbyte<74>n<EFBFBD> zvy<76>ovat CQ v<><76> ne<6E> 0.30, jeliko<6B> budete pl<70>tvat
|
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bity za minim<69>ln<6C> zisk kvality.
|
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|
</para>
|
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|
</sect2>
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<sect2 id="menc-feat-dvd-mpeg4-audio">
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<title>Zvuk</title>
|
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<para>
|
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Zvuk je mnohem jednodu<64><75><EFBFBD> probl<62>m k <20>e<EFBFBD>en<65>: pokud prahnete po kvalit<69>, prost<73>
|
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jej nechte tak jak je.
|
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Dokonce i AC3 5.1 datov<6F> proudy maj<61> nanejv<6A><76> 448Kbit<69>/s a stoj<6F> za ka<6B>d<EFBFBD> bit.
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Mo<4D>n<EFBFBD> jste v poku<6B>en<65> p<>ev<65>st zvuk do Ogg Vorbis p<>i vysok<6F> kvalit<69>, ale jen
|
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proto, <20>e dnes nem<65>te A/V receiver pro hardwarov<6F> dek<65>dov<6F>n<EFBFBD> AC3 neznamen<65>,
|
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|
<20>e jej nebudete m<>t z<>tra. P<>ipravte sv<73> DVD ripy zachov<6F>n<EFBFBD>m AC3 datov<6F>ch
|
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proud<75>.
|
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Datov<6F> proud AC3 m<><6D>ete zachovat bu<62> jeho zkop<6F>rov<6F>n<EFBFBD>m p<><70>mo do video proudu
|
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|
|
<link linkend="menc-feat-mpeg4">b<EFBFBD>hem enk<6E>dov<6F>n<EFBFBD></link>.
|
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|
Tak<61> m<><6D>ete extrahovat AC3 proud, abyste jej pak namixovali do nosi<73><69> jako je
|
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|
NUT nebo Matroska.
|
|
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|
|
<screen>mplayer <replaceable>zdrojov<EFBFBD>_soubor.vob</replaceable> -aid 129 -dumpaudio -dumpfile <replaceable>zvuk.ac3</replaceable></screen>
|
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|
|
vyt<79>hne do souboru <replaceable>zvuk.ac3</replaceable> zvukovou stopu
|
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|
<20><>slo 129 ze souboru <replaceable>zdrojov<EFBFBD>_soubor.vob</replaceable> (NB: DVD
|
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|
VOB soubory obvykle pou<6F><75>vaj<61> odli<6C>n<EFBFBD> <20><>slov<6F>n<EFBFBD> audia,
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|
co<63> znamen<65>, <20>e VOB zvukov<6F> stopa 120 je druhou zvukovou stopou v souboru).
|
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|
</para>
|
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|
<para>
|
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|
N<>kdy ov<6F>em opravdu nem<65>te jinou mo<6D>nost ne<6E> d<>le zkomprimovat zvuk, aby v<>m
|
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|
|
zbylo v<>ce bit<69> na video.
|
|
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|
V<>t<EFBFBD>ina lid<69> vol<6F> komprimaci bu<62> pomoc<6F> MP3 nebo Vorbis audio kodek<65>.
|
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|
Zat<61>mco ten druh<75> je efektivn<76>j<EFBFBD><6A> z prostorov<6F>ho hlediska, MP3 je l<>pe
|
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|
podporov<6F>n hardwarov<6F>mi p<>ehr<68>va<76>i, a<>koli <20>asy se m<>n<EFBFBD>.
|
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|
|
</para>
|
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|
<para>
|
|
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|
|
Nejd<6A><64>ve ze v<>eho budete muset p<>ev<65>st DVD zvuk do WAV souboru, kter<65> pak
|
|
|
|
|
pou<6F>ije zvukov<6F> kodek jako vstup.
|
|
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|
|
Nap<61><70>klad:
|
|
|
|
|
<screen>mplayer <replaceable>zdrojov<EFBFBD>_soubor.vob</replaceable> -ao pcm:file=<replaceable>v<EFBFBD>sledn<EFBFBD>_zvuk.wav</replaceable> -vc dummy -aid 1 -vo null</screen>
|
|
|
|
|
vylije druhou zvukovou stopu ze souboru
|
|
|
|
|
<replaceable>zdrojov<EFBFBD>_soubor.vob</replaceable> do souboru
|
|
|
|
|
<replaceable>v<EFBFBD>sledn<EFBFBD>_zvuk.wav</replaceable>.
|
|
|
|
|
M<>li byste normalizovat zvuk p<>ed enk<6E>dov<6F>n<EFBFBD>m, proto<74>e DVD zvukov<6F> stopy jsou
|
|
|
|
|
obvykle nahr<68>v<EFBFBD>ny p<>i n<>zk<7A>ch hlasitostech.
|
|
|
|
|
M<><4D>ete nap<61><70>klad pou<6F><75>t n<>stroj <application>normalize</application>, kter<65> je
|
|
|
|
|
k dispozici ve v<>t<EFBFBD>in<69> distribuc<75>.
|
|
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|
|
Pokud pou<6F><75>v<EFBFBD>te Windows, stejnou pr<70>ci ud<75>l<EFBFBD> n<>stroj jako
|
|
|
|
|
<application>BeSweet</application>.
|
|
|
|
|
Komprimovat budete bu<62> ve Vorbisu nebo MP3.
|
|
|
|
|
Nap<61><70>klad:
|
|
|
|
|
<screen>oggenc -q1 <replaceable>c<EFBFBD>lov<EFBFBD>_zvuk.wav</replaceable></screen>
|
|
|
|
|
provede enk<6E>dov<6F>n<EFBFBD> <replaceable>c<EFBFBD>lov<EFBFBD>ho_zvuku.wav</replaceable> s kvalitou 1,
|
|
|
|
|
kter<65> p<>ibli<6C>n<EFBFBD> odpov<6F>d<EFBFBD> 80Kb/s a je to minim<69>ln<6C> kvalita na kterou byste m<>li
|
|
|
|
|
enk<6E>dovat, pokud v<>m z<>le<6C><65> na kvalit<69>.
|
|
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|
|
Poznamenejme, <20>e <application>MEncoder</application> v sou<6F>asnosti neum<75>
|
|
|
|
|
muxovat Vorbis zvukov<6F> stopy do v<>stupn<70>ho souboru, proto<74>e podporuje pouze
|
|
|
|
|
AVI a MPEG kontejnery jako v<>stup. Pro oba plat<61>, <20>e n<>kter<65> p<>ehr<68>va<76>e mohou
|
|
|
|
|
m<>t probl<62>my s udr<64>en<65>m audio/video synchronizace, pokud je p<><70>tomen VBR zvuk
|
|
|
|
|
jako je Vorbis.
|
|
|
|
|
Nem<65>jte obavy, v tomto dokumentu v<>m uk<75><6B>eme, jak to lze ud<75>lat pomoc<6F>
|
|
|
|
|
program<61> t<>et<65>ch stran.
|
|
|
|
|
</para>
|
|
|
|
|
|
|
|
|
|
</sect2>
|
|
|
|
|
|
|
|
|
|
<sect2 id="menc-feat-dvd-mpeg4-interlacing">
|
|
|
|
|
<title>Prokl<EFBFBD>d<EFBFBD>n<EFBFBD> a Telecine</title>
|
|
|
|
|
|
|
|
|
|
<para>
|
|
|
|
|
T<>m<EFBFBD><6D> ve<76>ker<65> filmy jsou nat<61><74>eny p<>i 24 sn<73>mc<6D>ch/s. Jeliko<6B> NTSC m<>
|
|
|
|
|
sn<73>mkovou rychlost 30000/1001 sn<73>mk<6D>/s, je t<>eba prov<6F>st <20>pravu t<>chto
|
|
|
|
|
24 sn<73>mk<6D>/s vide<64>, aby m<>ly spr<70>vnou NTSC sn<73>mkovou rychlost. Tato <20>prava se
|
|
|
|
|
jmenuje 3:2 pulldown a obecn<63> je zn<7A>ma jako telecine (proto<74>e je pulldown
|
|
|
|
|
<20>asto prov<6F>d<EFBFBD>n b<>hem p<>enosu filmu na video) a, jednodu<64>e <20>e<EFBFBD>eno, pracuje tak,
|
|
|
|
|
<20>e se film zpomal<61> na 24000/1001 sn<73>mk<6D>/s a ka<6B>d<EFBFBD> <20>tvrt<72> sn<73>mek se zopakuje.
|
|
|
|
|
</para>
|
|
|
|
|
|
|
|
|
|
<para>
|
|
|
|
|
Naopak <20><>dn<64> speci<63>ln<6C> <20>pravy se neprov<6F>d<EFBFBD>j<EFBFBD> videu pro PAL DVD, kter<65> b<><62><EFBFBD>
|
|
|
|
|
p<>i 25 sn<73>mc<6D>ch/s. (Technicky lze na PAL prov<6F>st telecine, tzv. 2:2 pulldown,
|
|
|
|
|
ale v praxi se nepou<6F><75>v<EFBFBD>.) Film s 24 sn<73>mky/s je jednodu<64>e p<>ehr<68>v<EFBFBD>n rychlost<73>
|
|
|
|
|
25 sn<73>mk<6D>/s. V<>sledkem je, <20>e video b<><62><EFBFBD> o n<>co rychleji, ale pokud nejste
|
|
|
|
|
vet<65>elec, tak si rozd<7A>lu ani nev<65>imnete. V<>t<EFBFBD>ina film<6C> m<> nav<61>c v<><76>kov<6F>
|
|
|
|
|
korigovan<61> zvuk, tak<61>e p<>i p<>ehr<68>v<EFBFBD>n<EFBFBD> 25 sn<73>mk<6D>/s v<>e zn<7A> jak m<> i p<>esto, <20>e
|
|
|
|
|
zvuk (a proto i cel<65> video) m<> o 4% krat<61><74> dobu p<>ehr<68>v<EFBFBD>n<EFBFBD> ne<6E> NTSC DVD.
|
|
|
|
|
</para>
|
|
|
|
|
|
|
|
|
|
<para>
|
|
|
|
|
Jeliko<6B> video na PAL DVD nebylo upravov<6F>no, nemus<75>te si d<>lat starosti s jeho
|
|
|
|
|
sn<73>mkovou rychlost<73>. Zdroj m<> 25 sn<73>mk<6D>/s, v<><76> rip tak<61>. Pokud ov<6F>em ripujete
|
|
|
|
|
NTSC DVD film, mus<75>te prov<6F>st inverzn<7A> telecine.
|
|
|
|
|
</para>
|
|
|
|
|
|
|
|
|
|
<para>
|
|
|
|
|
Filmy to<74>en<65> rychlost<73> 24 sn<73>mk<6D>/s jsou na NTSC DVD ulo<6C>eny bu<62> jako
|
|
|
|
|
30000/1001 po telecine, nebo jako progresivn<76> (neprokl<6B>dan<61>) se sn<73>mkovou
|
|
|
|
|
24000/1001 sn<73>mk<6D>/s, na kter<65>ch by m<>l prov<6F>st telecine DVD p<>ehr<68>va<76> za letu.
|
|
|
|
|
Nen<65> to ale z<>kon: n<>kter<65> TV s<>rie jsou prokl<6B>dan<61> (nap<61>. Buffy Lovec up<75>r<EFBFBD>),
|
|
|
|
|
zat<61>mco jin<69> jsou por<6F>znu neprokl<6B>dan<61> nebo prokl<6B>dan<61> (nap<61>. And<6E>l, nebo 24
|
|
|
|
|
hodin).
|
|
|
|
|
</para>
|
|
|
|
|
|
|
|
|
|
<para>
|
|
|
|
|
Doporu<72>ujeme, abyste si p<>e<EFBFBD>etli sekci o tom
|
|
|
|
|
<link linkend="menc-feat-telecine">Jak si poradit s telecine a prokladem na NTSC DVD</link>
|
|
|
|
|
a nau<61>ili se jak vyu<79><75>t r<>zn<7A> mo<6D>nosti.
|
|
|
|
|
</para>
|
|
|
|
|
|
|
|
|
|
<para>
|
|
|
|
|
Pokud ov<6F>em v<>t<EFBFBD>inou ripujete pouze filmy, nejsp<73><70> se setk<74>v<EFBFBD>te
|
|
|
|
|
s neprokl<6B>dan<61>m nebo prokl<6B>dan<61>m videem 24 sn<73>mk<6D>/s. V tom p<><70>pad<61> m<><6D>ete
|
|
|
|
|
pou<6F><75>t <option>pullup</option> filtr <option>-vf pullup,softskip</option>.
|
|
|
|
|
</para>
|
|
|
|
|
|
|
|
|
|
</sect2>
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
<sect2 id="menc-feat-dvd-mpeg4-filtering">
|
|
|
|
|
<title>Filtrov<EFBFBD>n<EFBFBD></title>
|
|
|
|
|
|
|
|
|
|
<para>
|
|
|
|
|
Obecn<63> byste m<>li filtrovat video tak m<>lo, jak je to jen mo<6D>n<EFBFBD>, abyste
|
|
|
|
|
z<>stali co nejbl<62><6C> DVD origin<69>lu. O<>ez<65>n<EFBFBD> je <20>asto nutn<74> (jak jsme ji<6A> <20>ekli),
|
|
|
|
|
ale ne<6E>k<EFBFBD>lujte video. A<>koli zmen<65>en<65> rozli<6C>en<65> je ob<6F>as up<75>ednost<73>ov<6F>no p<>ed
|
|
|
|
|
pou<6F>it<69>m vy<76><79><EFBFBD>ch kvantizer<65>, mus<75>me se vyhnout ob<6F>ma p<><70>pad<61>m: pamatujme, <20>e
|
|
|
|
|
jsme se ji<6A> na za<7A><61>tku rozhodli ob<6F>tovat bity za kvalitu.
|
|
|
|
|
</para>
|
|
|
|
|
|
|
|
|
|
<para>
|
|
|
|
|
Rovn<76><6E> neupravujte gamu, kontrast, jas, atd. Co vypad<61> dob<6F>e na va<76><61>
|
|
|
|
|
obrazovce, nemus<75> vypadat dob<6F>e na jin<69>ch. Tato p<>izp<7A>soben<65> by m<>la b<>t
|
|
|
|
|
prov<6F>d<EFBFBD>na pouze p<>i p<>ehr<68>v<EFBFBD>n<EFBFBD>.
|
|
|
|
|
</para>
|
|
|
|
|
|
|
|
|
|
<para>
|
|
|
|
|
Jednu v<>c byste v<>ak ud<75>lat m<>li, a to prot<6F>hnout video velmi lehk<68>m
|
|
|
|
|
od<6F>umovac<61> filtr, jako je <option>-vf hqdn3d=2:1:2</option>.
|
|
|
|
|
Op<4F>t je to proto, abychom mohli n<>kter<65> bity l<>pe vyu<79><75>t: pro<72> s nimi pl<70>tvat
|
|
|
|
|
na <20>um, kdy<64> si jej m<><6D>ete p<>idat p<>i p<>ehr<68>v<EFBFBD>n<EFBFBD>? Zv<5A><76>en<65> parametr<74> pro
|
|
|
|
|
<option>hqdn3d</option> je<6A>t<EFBFBD> v<>ce zv<7A><76><EFBFBD> komprimovatelnost, ale pokud to
|
|
|
|
|
p<>e<EFBFBD>enete, riskujete zhor<6F>en<65> viditelnosti obrazu. Doporu<72>en<65> hodnoty okolo
|
|
|
|
|
(<option>2:1:2</option>) jsou dost konzervativn<76>; m<>li byste voln<6C>
|
|
|
|
|
experimentovat s vy<76><79><EFBFBD>mi hodnotami a posoudit v<>sledek sami.
|
|
|
|
|
</para>
|
|
|
|
|
|
|
|
|
|
</sect2>
|
|
|
|
|
|
|
|
|
|
<sect2 id="menc-feat-dvd-mpeg4-lavc-encoding-options">
|
|
|
|
|
<title>Enk<EFBFBD>dovac<EFBFBD> volby libavcodecu</title>
|
|
|
|
|
|
|
|
|
|
<para>
|
|
|
|
|
V ide<64>ln<6C>m p<><70>pad<61> byste asi cht<68>li jen <20><>ct enkod<6F>ru, aby se p<>epnul do
|
|
|
|
|
re<72>imu "vysok<6F> kvalita" a <20>el na to.
|
|
|
|
|
To by bylo jist<73> hezk<7A>, ale nane<6E>t<EFBFBD>st<73> je to t<><74>k<EFBFBD> zav<61>st, jeliko<6B> r<>zn<7A>
|
|
|
|
|
volby enk<6E>dov<6F>n<EFBFBD> vedou k r<>zn<7A> kvalit<69> v z<>vislosti na zdrojov<6F>m materi<72>lu.
|
|
|
|
|
To proto, <20>e komprese z<>vis<69> na vizu<7A>ln<6C>ch vlastnostech dan<61>ho videa.
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Nap<61><70>klad anime a <20>iv<69> akce maj<61> zcela rozd<7A>ln<6C> vlastnosti a tedy vy<76>aduj<75>
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odli<6C>n<EFBFBD> volby pro dosa<73>en<65> optim<69>ln<6C>ho enk<6E>dov<6F>n<EFBFBD>.
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Dobr<62> zpr<70>va je, <20>e n<>kter<65> volby by nikdy nem<65>ly chyb<79>t, jako
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<option>mbd=2</option>, <option>trell</option> a <option>v4mv</option>.
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Podrobn<62> popis obvykl<6B>ch enk<6E>dovac<61>ch voleb naleznete n<><6E>e.
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</para>
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<itemizedlist>
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<title>Volby k nastaven<65>:</title>
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<listitem><para>
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<emphasis role="bold">vmax_b_frames</emphasis>: 1 nebo 2 je v po<70><6F>dku,
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v z<>vislosti na filmu.
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Poznamenejme, <20>e libavcodec zat<61>m nepodporuje uzav<61>en<65> GOP (volba
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<option>cgop</option> zat<61>m nepracuje), tak<61>e DivX5 nebude schopen dek<65>dovat
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nic enk<6E>dovan<61>ho s B-sn<73>mky.
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</para></listitem>
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<listitem><para>
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<emphasis role="bold">vb_strategy=1</emphasis>: pom<6F>h<EFBFBD> ve sc<73>n<EFBFBD>ch s rychl<68>m
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pohybem.
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Vy<56>aduje vmax_b_frames >= 2.
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V n<>kter<65>ch vide<64>ch m<><6D>e vmax_b_frames sn<73><6E>it kvalitu, ale vmax_b_frames=2
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spolu s vb_strategy=1 pom<6F><6D>e.
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</para></listitem>
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<listitem><para>
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<emphasis role="bold">dia</emphasis>: okruh vyhled<65>v<EFBFBD>n<EFBFBD> pohybu. <20><>m v<>t<EFBFBD><74>, t<>m
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lep<65><70> a pomalej<65><6A>.
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Z<>porn<72> hodnoty maj<61> <20>pln<6C> jin<69> v<>znam.
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Dobr<62>mi hodnotami jsou -1 pro rychl<68> enk<6E>dov<6F>n<EFBFBD>, nebo 2-4 pro pomalej<65><6A>.
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</para></listitem>
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<listitem><para>
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<emphasis role="bold">predia</emphasis>: p<>edpr<70>chod pro vyhled<65>v<EFBFBD>n<EFBFBD> pohybu.
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Nen<65> tak d<>le<6C>it<69> jako dia. Dobr<62> hodnoty jsou 1 (v<>choz<6F>) a<> 4. Vy<56>aduje
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preme=2, aby byla opravdu k n<><6E>emu.
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</para></listitem>
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<listitem><para>
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<emphasis role="bold">cmp, subcmp, precmp</emphasis>: Porovn<76>vac<61> funkce pro
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odhad pohybu.
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Experimentujte s hodnotami 0 (v<>choz<6F>), 2 (hadamard), 3 (dct) a 6 (omezen<65>
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datov<6F>ho toku).
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0 je nejrychlej<65><6A> a dostate<74>n<EFBFBD> pro precmp.
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Pro cmp a subcmp je 2 dobr<62> pro anime a 3 zase pro <20>ivou akci.
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6 m<><6D>e, ale nemus<75> b<>t o n<>co lep<65><70>, ale je pomal<61>.
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</para></listitem>
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<listitem><para>
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<emphasis role="bold">last_pred</emphasis>: Po<50>et prediktor<6F> pohybu
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p<>eb<65>ran<61>ch z p<>edchoz<6F>ho sn<73>mku.
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1-3 nebo tak pom<6F><6D>ou za cenu men<65><6E>ho zdr<64>en<65>.
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Vy<56><79><EFBFBD> hodnoty jsou v<>ak pomal<61> a nep<65>in<69><6E><EFBFBD> <20><>dn<64> dal<61><6C> u<>itek.
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</para></listitem>
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<listitem><para>
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<emphasis role="bold">cbp, mv0</emphasis>: Ovl<76>d<EFBFBD> v<>b<EFBFBD>r makroblok<6F>.
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Mal<61> ztr<74>ta rychlosti za mal<61> zisk kvality.
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</para></listitem>
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<listitem><para>
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<emphasis role="bold">qprd</emphasis>: adaptivn<76> kvantizace zalo<6C>en<65> na
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komplexnosti makrobloku.
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M<><4D>e pomoci i u<>kodit v z<>vislosti na videu a ostatn<74>ch volb<6C>ch.
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Toto m<><6D>e zp<7A>sobovat artefakty, pokud nenastav<61>te vqmax na n<>jakou rozumn<6D>
|
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malou hodnotu (6 je dobr<62>, mo<6D>n<EFBFBD> byste ale m<>li j<>t a<> na 4); vqmin=1 m<><6D>e
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tak<61> pomoci.
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</para></listitem>
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<listitem><para>
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<emphasis role="bold">qns</emphasis>: velmi pomal<61>, zvlṻ v kombinaci
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s qprd.
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Tato volba nut<75> enkod<6F>r minimalizovat <20>um d<>ky kompresi artefakt<6B>, m<>sto aby
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se sna<6E>il striktn<74> zachov<6F>vat v<>rnost videa. Nepou<6F><75>vejte ji, pokud jste ji<6A>
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nezkusili v<>echno ostatn<74> kam a<> to <20>lo a v<>sledek p<>esto nen<65> dost dobr<62>.
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</para></listitem>
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<listitem><para>
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<emphasis role="bold">vqcomp</emphasis>: Vylep<65>en<65> ovl<76>d<EFBFBD>n<EFBFBD> datov<6F>ho toku.
|
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Dobr<62> hodnoty se li<6C><69> podle videa. M<><4D>ete to bezpe<70>n<EFBFBD> ponechat jak to je,
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pokud chcete.
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Sn<53><6E>en<65>m vqcomp pust<73>te v<>ce bit<69> do sc<73>n s n<>zkou komplexnost<73>, zv<7A><76>en<65>m je
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po<70>lete do sc<73>n s vysokou komplexnost<73> (v<>choz<6F>: 0.5, rozsah: 0-1. doporu<72>en<65>
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rozsah: 0.5-0.7).
|
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</para></listitem>
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<listitem><para>
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<emphasis role="bold">vlelim, vcelim</emphasis>: Nastav<61> jedin<69> koeficient
|
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prahu eliminace pro jasov<6F> a barevn<76> roviny.
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Ty jsou enk<6E>dov<6F>ny odd<64>len<65> ve v<>ech MPEGu podobn<62>ch algoritmech.
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My<4D>lenka stoj<6F>c<EFBFBD> za t<>mito volbami je pou<6F>it<69> dobr<62> heuristiky pro ur<75>en<65>,
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zda je zm<7A>na v bloku men<65><6E> ne<6E> v<>mi nastaven<65> pr<70>h a v tom p<><70>pad<61> se blok
|
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enk<6E>duje jako "nezm<7A>n<EFBFBD>n<EFBFBD>".
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To <20>et<65><74> bity a mo<6D>n<EFBFBD> i zrychl<68> enk<6E>dov<6F>n<EFBFBD>. vlelim=-4 a vcelim=9 se zdaj<61> b<>t
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dobr<62> pro hran<61> filmy, ale p<><70>li<6C> nepomohou s anime; pokud enk<6E>dujete anime,
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|
m<>li byste je asi nechat beze zm<7A>n.
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</para></listitem>
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<listitem><para>
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<emphasis role="bold">qpel</emphasis>: Odhad pohybu s p<>esnost<73> na <20>tvrt
|
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|
pixelu. MPEG-4 pou<6F><75>v<EFBFBD> p<>esnost na p<>l pixelu jako v<>choz<6F> p<>i vyhled<65>v<EFBFBD>n<EFBFBD>
|
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pohybu, proto je tato volba spojena s ur<75>itou re<72>i<EFBFBD>, jeliko<6B> se do v<>stupn<70>ho
|
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|
souboru ukl<6B>d<EFBFBD> v<>ce informac<61>.
|
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|
Kompresn<73> zisk/ztr<74>ta z<>vis<69> na filmu, ale obvykle to nen<65> p<><70>li<6C> efektivn<76>
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na anime.
|
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qpel v<>dy zp<7A>sob<6F> zv<7A><76>en<65> v<>po<70>etn<74> n<>ro<72>nosti dek<65>dov<6F>n<EFBFBD> (v praxi +20% <20>asu
|
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|
CPU).
|
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|
</para></listitem>
|
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|
<listitem><para>
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|
<emphasis role="bold">psnr</emphasis>: neovlivn<76> aktu<74>ln<6C> enk<6E>dov<6F>n<EFBFBD>, ale
|
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|
|
zaznamen<65> typ/velikost/kvalitu ka<6B>d<EFBFBD>ho sn<73>mku do log souboru a na konci vyp<79><70>e
|
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|
|
souhrnn<6E> PSNR (odstup sign<67>lu od <20>umu).
|
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|
</para></listitem>
|
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|
</itemizedlist>
|
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|
<itemizedlist>
|
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|
<title>Volby se kter<65>mi nedoporu<72>ujeme si hr<68>t:</title>
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|
<listitem><para>
|
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|
<emphasis role="bold">vme</emphasis>: V<>choz<6F> je nejlep<65><70>.
|
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|
</para></listitem>
|
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|
<listitem><para>
|
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|
|
<emphasis role="bold">lumi_mask, dark_mask</emphasis>: Psychovizu<7A>ln<6C>
|
|
|
|
|
adaptivn<76> kvantizace.
|
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|
|
Nehrajte si s t<>mito volbami, pokud v<>m jde o kvalitu. Rozumn<6D> hodnoty mohou
|
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|
|
b<>t efektivn<76> ve va<76>em p<><70>pad<61>, ale pozor, je to velmi subjektivn<76>.
|
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|
</para></listitem>
|
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|
<listitem><para>
|
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|
<emphasis role="bold">scplx_mask</emphasis>: Sna<6E><61> se p<>edch<63>zet blokov<6F>m
|
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|
|
artefakt<6B>m, ale postprocesing je lep<65><70>.
|
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|
</para></listitem>
|
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|
</itemizedlist>
|
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|
</sect2>
|
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|
<sect2 id="menc-feat-dvd-mpeg4-example">
|
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|
<title>P<EFBFBD><EFBFBD>klad</title>
|
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|
<para>
|
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|
|
Tak<61>e jste si koupili zbrusu novou kopii filmu Harry Potter a Tajemn<6D> komnata
|
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|
|
(<28>iroko<6B>hlou verzi samoz<6F>ejm<6A>) a chcete si toto DVD ripnout, tak<61>e si jej
|
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|
|
|
m<><6D>ete p<>idat do sv<73>ho Dom<6F>c<EFBFBD>ho kino-po<70><6F>ta<74>e PC. Je to region 1 DVD, tak<61>e je
|
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|
|
v NTSC. N<><4E>e uveden<65> p<><70>klad je st<73>le vhodn<64> i pro PAL, jen mus<75>te vynechat
|
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|
|
<option>-ofps 24000/1001</option> (proto<74>e v<>stupn<70> sn<73>mkov<6F> rychlost je
|
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|
shodn<64> se vstupn<70>) a p<>irozen<65> budou rozd<7A>ln<6C> sou<6F>adnice pro o<>ez.
|
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|
</para>
|
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<para>
|
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|
Po spu<70>t<EFBFBD>n<EFBFBD> <option>mplayer dvd://1</option>, postupujeme podle informac<61>
|
|
|
|
|
obsa<73>en<65>ch v sekci <link linkend="menc-feat-telecine">Jak nalo<6C>it s telecine
|
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|
|
a prokladem v NTSC DVD</link> a zjist<73>me <20>e je to 24000/1001 neprokl<6B>dan<61>
|
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|
video, tak<61>e nepot<6F>ebujeme pou<6F><75>t inverzn<7A> telecine filtr, jako je
|
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|
|
<option>pullup</option> nebo <option>filmdint</option>.
|
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|
|
</para>
|
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|
<para>
|
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|
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|
D<>le mus<75>me zjistit vhodn<64> o<>ezov<6F> obd<62>ln<6C>k, tak<61>e pou<6F>ijeme filtr cropdetect:
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|
<screen>mplayer dvd://1 -vf cropdetect</screen>
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|
Ujist<73>te se, <20>e jste p<>e<EFBFBD>li p<>es zapln<6C>n<EFBFBD> sn<73>mek (n<>jakou jasnou sc<73>nu) a
|
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|
v konzoli <application>MPlayer</application>u uvid<69>te:
|
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|
<screen>crop area: X: 0..719 Y: 57..419 (-vf crop=720:362:0:58)</screen>
|
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|
Potom p<>ehrajeme film s t<>mto filtrem, abychom otestovali jeho spr<70>vnost:
|
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|
<screen>mplayer dvd://1 -vf crop=720:362:0:58</screen>
|
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A zjist<73>me, <20>e to vypad<61> zcela v po<70><6F>dku. D<>le se ujist<73>me, <20>e <20><><EFBFBD>ka i v<><76>ka
|
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jsou n<>sobky 16. <20><><EFBFBD>ka je v po<70><6F>dku, v<><76>ka ov<6F>em ne. Proto<74>e jsme nepropadli
|
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|
|
v sedm<64> t<><74>d<EFBFBD> z matematiky, v<>me, <20>e nejbli<6C><69><EFBFBD>m n<>sobkem 16 ni<6E><69><EFBFBD>m ne<6E> 362 je
|
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352.
|
|
|
|
|
</para>
|
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|
|
<para>
|
|
|
|
|
Mohli bychom pou<6F><75>t <option>crop=720:352:0:58</option>, ale bude lep<65><70>
|
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|
|
ust<73>ihnout kousek naho<68>e i dole, tak<61>e zachov<6F>me st<73>ed. Zkr<6B>tili jsme v<><76>ku
|
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|
|
o 10 pixel<65>, ale nechceme zv<7A><76>it odsazen<65> y o 5 pixel<65>, proto<74>e je to lich<63>
|
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|
|
<20><>slo, co<63> by nep<65><70>zniv<69> ovlivnilo kvalitu. M<>sto toho zv<7A><76><EFBFBD>me odsazen<65> y o 4
|
|
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|
|
pixely:
|
|
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|
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|
|
|
<screen>mplayer dvd://1 -vf crop=720:352:0:62</screen>
|
|
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|
Dal<61><6C> d<>vod pro odst<73>i<EFBFBD>en<65> pixel<65> shora i zdola je to, <20>e si m<><6D>eme b<>t jisti
|
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|
odst<73>i<EFBFBD>en<65>m nap<61>l <20>ern<72>ch pixel<65> pokud existuj<75>. Pokud je v<>ak va<76>e video
|
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|
telecinov<6F>no, ujist<73>te se, <20>e m<>te v <20>et<65>zu filtr<74> <option>pullup</option>
|
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|
|
filtr (nebo jin<69> filtr pro inverzi telecine, kter<65> hodl<64>te pou<6F><75>t) je<6A>t<EFBFBD> p<>ed
|
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|
odstran<61>n<EFBFBD>m prokladu a o<>ezem. (Pokud se rozhodnete zachovat va<76>e video
|
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|
prokl<6B>dan<61>, pak se ujist<73>te, <20>e va<76>e vertik<69>ln<6C> odsazen<65> (offset)
|
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|
|
je n<>sobkem 4.)
|
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|
</para>
|
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|
<para>
|
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|
Pokud si d<>l<EFBFBD>te starosti se ztr<74>tou t<>ch 10 pixel<65>, mo<6D>n<EFBFBD> rad<61>ji sn<73><6E><EFBFBD>te
|
|
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|
|
rozm<7A>ry na nejbli<6C><69><EFBFBD> n<>sobek 16. <20>et<65>zec filtr<74> by pak vypadal asi takto:
|
|
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|
|
|
|
|
|
|
<screen>-vf crop=720:362:0:58,scale=720:352</screen>
|
|
|
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|
|
Takov<6F>to zmen<65>en<65> videa bude znamenat ztr<74>tu mal<61>ho mno<6E>stv<74> detail<69>, co<63> bude
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pravd<76>podobn<62> st<73><74><EFBFBD> post<73>ehnuteln<6C>. Zv<5A>t<EFBFBD>ov<6F>n<EFBFBD> by naopak vedlo ke sn<73><6E>en<65>
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kvality (pokud byste nezv<7A><76>ili datov<6F> tok). O<>ez odstran<61> tyto pixely <20>pln<6C>.
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To je jedna z v<>c<EFBFBD>, kterou byste si m<>li uv<75><76>it pro ka<6B>d<EFBFBD> p<><70>pad zvlṻ.
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Nap<61><70>klad pokud bylo DVD video vyrobeno pro televizi, m<>li byste se vyvarovat
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vertik<69>ln<6C>mu <20>k<EFBFBD>lov<6F>n<EFBFBD>, jeliko<6B> po<70>et <20><>dk<64> odpov<6F>d<EFBFBD> origin<69>ln<6C> nahr<68>vce.
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</para>
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<para>
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P<>i prohl<68>dce jsme zjistili, <20>e video je pom<6F>rn<72> ak<61>n<EFBFBD>, s vysok<6F>m po<70>tem
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detail<69>, tak<61>e jsme zvolili datov<6F> tok 2400 Kbit<69>.
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</para>
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<para>
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Nyn<79> jsme p<>ipraveni prov<6F>st dvoupr<70>chodov<6F> enk<6E>dov<6F>n<EFBFBD>. Pr<50>chod jedna:
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<screen>mencoder dvd://1 -ofps 24000/1001 -oac copy -vf crop=720:352:0:62,hqdn3d=2:1:2 -ovc lavc \
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-lavcopts vcodec=mpeg4:vbitrate=2400:v4mv:mbd=2:trell:cmp=3:subcmp=3:mbcmp=3:autoaspect:vpass=1 \
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-o Harry_Potter_2.avi</screen>
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A pr<70>chod dva je stejn<6A>, jen nastav<61>me <option>vpass=2</option>:
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<screen>mencoder dvd://1 -ofps 24000/1001 -oac copy -vf crop=720:352:0:62,hqdn3d=2:1:2 -ovc lavc \
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-lavcopts vcodec=mpeg4:vbitrate=2400:v4mv:mbd=2:trell:cmp=3:subcmp=3:mbcmp=3:autoaspect:vpass=2 \
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-o Harry_Potter_2.avi</screen>
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</para>
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<para>
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Volby <option>v4mv:mbd=2:trell</option> velmi zv<7A><76><EFBFBD> kvalitu za cenu <20>asov<6F>
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n<>ro<72>nosti enk<6E>dov<6F>n<EFBFBD>. Vcelku nen<65> d<>vod tuto volbu vypustit, pokud je
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prim<69>rn<72>m c<>lem kvalita. Volby <option>cmp=3:subcmp=3:mbcmp=3</option>
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vyberou porovn<76>vac<61> funkci, kter<65> poskytuje lep<65><70> kvalitu, ne<6E> v<>choz<6F>.
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S t<>mto parametrem m<><6D>ete zkusit experimentovat (nahl<68>dn<64>te do man str<74>nky pro
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seznam mo<6D>n<EFBFBD>ch hodnot), jeliko<6B> r<>zn<7A> funkce mohou m<>t velk<6C> vliv na kvalitu
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v z<>vislosti na zdrojov<6F>m materi<72>lu. Nap<61><70>klad pokud zjist<73>te, <20>e
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<systemitem class="library">libavcodec</systemitem> produkuje p<><70>li<6C> mnoho
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<20>tvere<72>kov<6F>ch artefakt<6B>, m<><6D>ete zkusit zvolit experiment<6E>ln<6C> NSSE jako
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porovn<76>vac<61> funkci p<>es <option>*cmp=10</option>.
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</para>
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<para>
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V p<><70>pad<61> tohoto filmu bude v<>sledn<64> AVI dlouh<75> 138 minut a velik<69> kolem 3GB.
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A proto<74>e jste <20>ekli, <20>e na velikosti nez<65>le<6C><65>, je to p<>ijateln<6C> velikost.
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Ale pokud byste jej cht<68>li men<65><6E>, m<><6D>ete zkusit ni<6E><69><EFBFBD> datov<6F> tok.
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Efekt zvy<76>ov<6F>n<EFBFBD> datov<6F>ho toku se toti<74> neust<73>le sni<6E>uje, tak<61>e zat<61>mco je
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zlep<65>en<65> po zv<7A><76>en<65> z 1800 Kbit<69> na 2000 Kbit<69> zjevn<76>, nemus<75> b<>t ji<6A> tak
|
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velk<6C> nad 2000 Kbit<69>. Beze v<>eho s t<>m experimentujte, dokud nebudete
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spokojeni.
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</para>
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<para>
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Jeliko<6B> jsme prot<6F>hli video od<6F>umovac<61>m filtrem, m<>li bychom jej trochu p<>idat
|
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b<>hem p<>ehr<68>v<EFBFBD>n<EFBFBD>. To, spolu s <option>spp</option> post-procesn<73>m filtrem,
|
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|
|
|
znateln<6C> zv<7A><76><EFBFBD> vn<76>manou kvalitu a pom<6F><6D>e odstranit <20>tvere<72>kov<6F> artefakty ve
|
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|
|
videu. S <application>MPlayer</application>ovou volbou <option>autoq</option>
|
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|
m<><6D>e b<>t mno<6E>stv<74> postprocesingu prov<6F>d<EFBFBD>n<EFBFBD>ho filtrem spp p<>izp<7A>sobov<6F>no
|
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|
vyt<79><74>en<65> CPU. V tuto chv<68>li rovn<76><6E> m<><6D>ete prov<6F>st korekci gama a/nebo barevnou
|
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|
korekci k dosa<73>en<65> nejlep<65><70>ch v<>sledk<64>. Nap<61><70>klad:
|
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|
<screen>mplayer Harry_Potter_2.avi -vf spp,noise=9ah:5ah,eq2=1.2 -autoq 3</screen>
|
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|
</para>
|
|
|
|
|
</sect2>
|
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|
|
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|
<sect2 id="menc-feat-dvd-mpeg4-muxing">
|
|
|
|
|
<title>Muxov<EFBFBD>n<EFBFBD> (multiplexov<6F>n<EFBFBD>)</title>
|
|
|
|
|
<para>
|
|
|
|
|
Nyn<79>, kdy<64> m<>te sv<73> video enk<6E>dovan<61>, budete jej nejsp<73><70> cht<68>t muxovat
|
|
|
|
|
s jedn<64>m nebo v<>ce zvukov<6F>mi stopami do nosn<73>ho filmov<6F>ho form<72>tu, jako je
|
|
|
|
|
AVI, MPEG, Matroska nebo NUT.
|
|
|
|
|
<application>MEncoder</application> je zat<61>m schopen zvuk a video zapracovat
|
|
|
|
|
pouze do nosn<73>ch form<72>t<EFBFBD> MPEG a AVI.
|
|
|
|
|
Nap<61><70>klad:
|
|
|
|
|
<screen>mencoder -oac copy -ovc copy -o <replaceable>v<EFBFBD>stupn<EFBFBD>_film.avi</replaceable> -audiofile <replaceable>vstupn<EFBFBD>_audio.mp2</replaceable> <replaceable>vstupn<EFBFBD>_video.avi</replaceable></screen>
|
|
|
|
|
To by m<>lo slou<6F>it video soubor <replaceable>vstupn<EFBFBD>_video.avi</replaceable>
|
|
|
|
|
a zvukov<6F> soubor <replaceable>vstupn<EFBFBD>_audio.mp2</replaceable>
|
|
|
|
|
do AVI souboru <replaceable>v<EFBFBD>stupn<EFBFBD>_film.avi</replaceable>.
|
|
|
|
|
Tento p<><70>kaz pracuje s MPEG-1 layer I, II a III (zn<7A>m<EFBFBD>m jako MP3) zvukem,
|
|
|
|
|
WAV a tak<61> n<>kolika dal<61><6C>mi form<72>ty zvuku.
|
|
|
|
|
</para>
|
|
|
|
|
|
|
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|
|
<para>
|
|
|
|
|
<application>MEncoder</application> obsahuje experiment<6E>ln<6C> podporu pro
|
|
|
|
|
<systemitem class="library">libavformat</systemitem>, co<63> je knihovna
|
|
|
|
|
z projektu FFmpeg, kter<65> podporuje muxov<6F>n<EFBFBD> a demuxov<6F>n<EFBFBD> cel<65> <20>ady nosn<73>ch
|
|
|
|
|
form<72>t<EFBFBD>.
|
|
|
|
|
Nap<61><70>klad:
|
|
|
|
|
<screen>mencoder -oac copy -ovc copy -o <replaceable>v<EFBFBD>stupn<EFBFBD>_film.asf</replaceable> -audiofile <replaceable>vstupn<EFBFBD>_audio.mp2</replaceable> <replaceable>vstupn<EFBFBD>_video.avi</replaceable> -of lavf -lavfopts format=asf</screen>
|
|
|
|
|
To provede stejnou <20>innost jako p<>edchoz<6F> p<><70>klad, av<61>ak v<>stupn<70>m form<72>tem
|
|
|
|
|
bude ASF.
|
|
|
|
|
Pros<6F>m berte na v<>dom<6F>, <20>e tato podpora je velmi experiment<6E>ln<6C> (ale de ode
|
|
|
|
|
dne lep<65><70>) a bude funk<6E>n<EFBFBD> pouze pokud jste zkompilovali
|
|
|
|
|
<application>MPlayer</application> s podporou pro
|
|
|
|
|
<systemitem class="library">libavformat</systemitem> (co<63> znamen<65>, <20>e
|
|
|
|
|
p<>edkompilovan<61> bin<69>rn<72> verze nebude v<>t<EFBFBD>inou fungovat).
|
|
|
|
|
</para>
|
|
|
|
|
|
|
|
|
|
<sect3 id="menc-feat-dvd-mpeg4-muxing-avi-limitations">
|
|
|
|
|
<title>Limitace nosn<73>ho form<72>tu AVI</title>
|
|
|
|
|
<para>
|
|
|
|
|
A<>koli je to po MPEG-1 nejpodporovan<61>j<EFBFBD><6A> nosn<73> form<72>t, m<> AVI i jist<73>
|
|
|
|
|
z<>sadn<64> nedostatky. Snad nejviditeln<6C>j<EFBFBD><6A> je re<72>ie.
|
|
|
|
|
Na ka<6B>d<EFBFBD> chunk AVI souboru je 24 bajt<6A> ztraceno na hlavi<76>ky a index.
|
|
|
|
|
To se projev<65> asi 5 MP na hodinu, neboli 1-2.5% prodlou<6F>en<65> 700 MB filmu.
|
|
|
|
|
Nevypad<61> to jako mnoho, ale m<><6D>e to znamenat rozd<7A>l mezi mo<6D>nost<73> pou<6F><75>t
|
|
|
|
|
video p<>i 700 kbitech/s nebo 714 kbitech/s a tady se ka<6B>d<EFBFBD> bit projev<65> na
|
|
|
|
|
kvalit<69>.
|
|
|
|
|
</para>
|
|
|
|
|
|
|
|
|
|
<para>
|
|
|
|
|
Nav<61>c k t<>to neefektivit<69> m<> AVI tak<61> n<>sleduj<75>c<EFBFBD> hlavn<76> omezen<65>:
|
|
|
|
|
</para>
|
|
|
|
|
|
|
|
|
|
<orderedlist>
|
|
|
|
|
<listitem>
|
|
|
|
|
<para>
|
|
|
|
|
M<><4D>e b<>t uchov<6F>v<EFBFBD>n pouze obsah s konstantn<74> sn<73>mkovou rychlost<73>. To je
|
|
|
|
|
zvl<76><6C>t<EFBFBD> omezuj<75>c<EFBFBD>, kdy<64> m<> p<>vodn<64> materi<72>l, kter<65> chcete enk<6E>dovat, sm<73><6D>en<65>
|
|
|
|
|
obsah. Nap<61><70>klad sm<73>s NTSC videa a filmov<6F>ho materi<72>lu.
|
|
|
|
|
Jist<73><74>e jsou zde cesti<74>ky, kter<65> umo<6D>n<EFBFBD> ulo<6C>it obsah se sm<73><6D>enou sn<73>mkovou
|
|
|
|
|
rychlost<73> v AVI, ale ty zvy<76>uj<75> (ji<6A> tak velkou) re<72>ii p<>tin<69>sobn<62> nebo v<>c,
|
|
|
|
|
proto nejsou praktick<63>.
|
|
|
|
|
</para>
|
|
|
|
|
</listitem>
|
|
|
|
|
<listitem>
|
|
|
|
|
<para>
|
|
|
|
|
Zvuk v AVI mus<75> m<>t bu<62> konstantn<74> datov<6F> tok (CBR) nebo konstantn<74> velikost
|
|
|
|
|
r<>mce (<28>ili v<>echny r<>mce se dek<65>duj<75> na stejn<6A> po<70>et vzork<72>).
|
|
|
|
|
Nane<6E>t<EFBFBD>st<73> ten nejefektivn<76>j<EFBFBD><6A> kodek, Vorbis, nespl<70>uje ani jeden z t<>chto
|
|
|
|
|
po<70>adavk<76>.
|
|
|
|
|
Pokud tedy pl<70>nujete ulo<6C>it sv<73>j film do AVI, budete muset pou<6F><75>t m<>n<EFBFBD>
|
|
|
|
|
efektivn<76> kodek, jako MP3 nebo AC3.
|
|
|
|
|
</para>
|
|
|
|
|
</listitem>
|
|
|
|
|
</orderedlist>
|
|
|
|
|
|
|
|
|
|
<para>
|
|
|
|
|
Z v<><76>e uveden<65>ch d<>vod<6F> <application>MEncoder</application> zat<61>m
|
|
|
|
|
nepodporuje prom<6F>nnou sn<73>mkovou rychlost ani enk<6E>dov<6F>n<EFBFBD> do Vorbisu.
|
|
|
|
|
Nemus<75>te to v<>ak pova<76>ovat za omezen<65>, jestli<6C>e je
|
|
|
|
|
<application>MEncoder</application> jedin<69>m n<>strojem pro va<76>e
|
|
|
|
|
enk<6E>dov<6F>n<EFBFBD>. Nakonec je mo<6D>n<EFBFBD> pou<6F><75>t <application>MEncoder</application> pouze
|
|
|
|
|
pro enk<6E>dov<6F>n<EFBFBD> videa a pak pou<6F><75>t extern<72> n<>stroje pro enk<6E>dov<6F>n<EFBFBD> zvuku a
|
|
|
|
|
namuxov<6F>n<EFBFBD> do jin<69>ho nosn<73>ho form<72>tu.
|
|
|
|
|
</para>
|
|
|
|
|
</sect3>
|
|
|
|
|
|
|
|
|
|
<sect3 id="menc-feat-dvd-mpeg4-muxing-matroska">
|
|
|
|
|
<title>Muxov<EFBFBD>n<EFBFBD> do nosn<73>ho form<72>tu Matroska</title>
|
|
|
|
|
<para>
|
|
|
|
|
Matroska je svobodn<64> a otev<65>en<65> standard nosn<73>ho form<72>tu, zam<61><6D>en<65> na
|
|
|
|
|
nab<61>dku mnoha pokro<72>il<69>ch vlastnost<73>, kter<65> star<61><72> nosn<73> form<72>ty, jako AVI,
|
|
|
|
|
nemohou poskytnout.
|
|
|
|
|
Nap<61><70>klad Matroska podporuje zvuk s prom<6F>nn<6E>m datov<6F>m tokem (VBR),
|
|
|
|
|
prom<6F>nn<6E> sn<73>mkov<6F> rychlosti (VFR), kapitoly, p<><70>lohy soubor<6F>, k<>d pro
|
|
|
|
|
detekci chyb (EDC) a modern<72> A/V kodeky jako "Advanced Audio
|
|
|
|
|
Coding" (AAC), "Vorbis" nebo "MPEG-4 AVC" (H.264), z nich<63> <20><>dn<64> nelze
|
|
|
|
|
pou<6F><75>t v AVI.
|
|
|
|
|
</para>
|
|
|
|
|
|
|
|
|
|
<para>
|
|
|
|
|
N<>stroje pro vytv<74><76>en<65> Matroska soubor<6F> jsou souhrnn<6E> nazv<7A>ny
|
|
|
|
|
<application>mkvtoolnix</application> a jsou dostupn<70> pro v<>t<EFBFBD>inu Unixov<6F>ch
|
|
|
|
|
platforem a stejn<6A> tak <application>Windows</application>.
|
|
|
|
|
Proto<74>e je Matroska otev<65>en<65> standard, m<><6D>ete naj<61>t jin<69> n<>stroje, kter<65> v<>m
|
|
|
|
|
l<>pe padnou, ale proto<74>e mkvtoolnix je nejroz<6F><7A><EFBFBD>en<65>j<EFBFBD><6A> a je podporov<6F>n
|
|
|
|
|
p<><70>mo Matroska t<>mem, pokryjeme jen jejich pou<6F>it<69>.
|
|
|
|
|
</para>
|
|
|
|
|
|
|
|
|
|
<para>
|
|
|
|
|
Asi nejsnaz<61><7A> zp<7A>sob, jak za<7A><61>t s Matroskou je pou<6F><75>t
|
|
|
|
|
<application>MMG</application>, grafickou nadstavbu dod<6F>vanou s
|
|
|
|
|
<application>mkvtoolnix</application> a <20><>dit se
|
|
|
|
|
<ulink url="http://www.bunkus.org/videotools/mkvtoolnix/doc/mkvmerge-gui.html">n<EFBFBD>vodem k mkvmerge GUI (mmg)</ulink>
|
|
|
|
|
</para>
|
|
|
|
|
|
|
|
|
|
<para>
|
|
|
|
|
M<><4D>ete rovn<76><6E> muxovat zvukov<6F> a video soubory z p<><70>kazov<6F>ho <20><>dku:
|
|
|
|
|
<screen>mkvmerge -o <replaceable>v<EFBFBD>stup.mkv</replaceable> <replaceable>vstupn<EFBFBD>_video.avi</replaceable> <replaceable>vstupn<EFBFBD>_audio1.mp3</replaceable> <replaceable>vstupn<EFBFBD>_audio2.ac3</replaceable></screen>
|
|
|
|
|
To spoj<6F> video soubor <replaceable>vstupn<EFBFBD>_video.avi</replaceable>
|
|
|
|
|
a dva zvukov<6F> soubory <replaceable>vstupn<EFBFBD>_audio1.mp3</replaceable>
|
|
|
|
|
a <replaceable>vstupn<EFBFBD>_audio2.ac3</replaceable> do Matroska souboru
|
|
|
|
|
<replaceable>v<EFBFBD>stup.mkv</replaceable>.
|
|
|
|
|
Matroska, jak jsme ji<6A> <20>ekli, um<75> mnohem v<>c ne<6E> to, jako v<>ce zvukov<6F>ch stop
|
|
|
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|
(v<>etn<74> dolad<61>n<EFBFBD> audio/video synchronizace), kapitoly, titulky, st<73><74>h<EFBFBD>n<EFBFBD>,
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atd...
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Detaily naleznete v dokumentaci k t<>mto aplikac<61>m.
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</para>
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</sect3>
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</sect2>
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</sect1>
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2005-05-09 05:43:21 +00:00
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<sect1 id="menc-feat-x264">
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<title>Enk<EFBFBD>dov<EFBFBD>n<EFBFBD> s <systemitem class="library">x264</systemitem> kodekem</title>
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<para>
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<systemitem class="library">x264</systemitem> je svobodn<64> knihovna pro
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enk<6E>dov<6F>n<EFBFBD> H264/AVC video proud<75>.
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P<>e zah<61>jen<65>m enk<6E>dov<6F>n<EFBFBD> budete muset <link linkend="codec-x264-encode">
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nastavit jej<65> podporu v<application>MEncoder</application>u</link>.
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</para>
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<sect2 id="menc-feat-x264-intro">
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<title>Jak<EFBFBD> volby bychom m<>li nastavit pro nejlep<65><70> v<>sledky?</title>
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<para>
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Za<5A>n<EFBFBD>te pros<6F>m prostudov<6F>n<EFBFBD>m <20><>sti
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<systemitem class="library">x264</systemitem> v man str<74>nce
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<application>MPlayer</application>u.
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Tato sekce je zam<61><6D>lena jako dopln<6C>k man str<74>nky.
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</para>
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<orderedlist>
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<title>Obecn<EFBFBD> jsou zde t<>i typy uva<76>ov<6F>n<EFBFBD> p<>i volb<6C> vhodn<64>ch voleb enkod<6F>ru:
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</title>
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<listitem><para><EFBFBD>asov<EFBFBD> n<>ro<72>nost enk<6E>dov<6F>n<EFBFBD> vs. kvalita</para></listitem>
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<listitem><para>Volby rozhoduj<75>c<EFBFBD> o typu sn<73>mk<6D></para></listitem>
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<listitem><para>Volby ovliv<69>uj<75>c<EFBFBD> kontrolu datov<6F>ho toku a kvantizaci</para></listitem>
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</orderedlist>
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<para>
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Tento n<>vod se v<>t<EFBFBD>inou zam<61><6D>uje na prvn<76> skupinu voleb.
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Dal<61><6C> dv<64> skupiny <20>asto z<>le<6C><65> na osobn<62>ch preferenc<6E>ch a individu<64>ln<6C>ch
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po<70>adavc<76>ch.
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</para>
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<para>
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Ne<4E> budeme pokra<72>ovat, poznamenejme, <20>e tento n<>vod pou<6F><75>v<EFBFBD> jedin<69> m<><6D><EFBFBD>tko
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kvality: celkov<6F> PSNR.
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Stru<72>n<EFBFBD> vysv<73>tlen<65> co je to PSNR, naleznete
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<ulink url="http://en.wikipedia.org/wiki/PSNR">ve Wikipedii pod heslem PSNR</ulink>.
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Celkov<6F> PSNR je posledn<64> hl<68><6C>en<65> PSNR <20><>slo p<>i za<7A>azen<65> volby
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<option>psnr</option> v <option>x264encopts</option>.
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Kdykoli budete <20><>st prohl<68><6C>en<65> o PSNR, jeden z p<>edpoklad<61> tohoto sd<73>len<65>
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je, <20>e jsou pou<6F>ity shodn<64> datov<6F> toky.
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</para>
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<para>
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T<>m<EFBFBD><6D> v<>echny koment<6E><74>e v tomto n<>vodu p<>edpokl<6B>daj<61>, <20>e enk<6E>dujete
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dvoupr<70>chodov<6F>.
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P<>i porovn<76>v<EFBFBD>n<EFBFBD> voleb jsou zde dva hlavn<76> d<>vody pro pou<6F>it<69> dvoupr<70>chodov<6F>ho
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enk<6E>dov<6F>n<EFBFBD>.
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Zaprv<72>, dvoupr<70>chodov<6F> enk<6E>dov<6F>n<EFBFBD> v<>m z<>sk<73> zhruba 1dB PSNR, co<63> je
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velk<6C> rozd<7A>l.
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Zadruh<75>, testov<6F>n<EFBFBD> voleb pomoc<6F> p<><70>m<EFBFBD>ho porovn<76>n<EFBFBD> kvality v jednopr<70>chodov<6F>ch
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v<>sledc<64>ch je pochybn<62>, jeliko<6B> se datov<6F> tok zna<6E>n<EFBFBD> li<6C><69> s ka<6B>d<EFBFBD>m
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enk<6E>dov<6F>n<EFBFBD>m.
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Nen<65> v<>dy snadn<64> ur<75>it, zda se zm<7A>nila kvalita d<>ky zm<7A>n<EFBFBD> voleb, nebo
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z v<>t<EFBFBD><74> <20><>sti odpov<6F>daj<61> zm<7A>n<EFBFBD>m datov<6F>ho toku.
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</para>
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<para>
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Z voleb, kter<65> umo<6D><6F>uj<75> vym<79>nit <20>as za kvalitu, jsou obvykle nejd<6A>le<6C>it<69>j<EFBFBD><6A>
|
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|
<option>subq</option> a <option>frameref</option>.
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M<>te-li z<>jem ovlivnit jak rychlost, tak kvalitu, jsou to prvn<76> volby,
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kter<65> byste m<>li zv<7A><76>it.
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</para>
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|
<para>
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Ve smyslu rychlosti se spolu volby <option>frameref</option> a
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|
<option>subq</option> velmi siln<6C> ovliv<69>uj<75>.
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Zku<6B>enosti ukazuj<75>, <20>e p<>i jednom referen<65>n<EFBFBD>m sn<73>mku si
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<option>subq=5</option> vezme asi o 35% v<>ce <20>asu ne<6E>
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|
<option>subq=1</option>.
|
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|
P<>i 6 referen<65>n<EFBFBD>ch sn<73>mc<6D>ch naroste spomalen<65> nad 60%.
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|
Vliv <option>subq</option> na PSNR se zd<7A> b<>t pom<6F>rn<72> st<73>l<EFBFBD>,
|
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|
bez ohledu na po<70>et referen<65>n<EFBFBD>ch sn<73>mk<6D>.
|
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|
Typicky <option>subq=5</option> z<>sk<73> 0.2-0.5 dB
|
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|
celkov<6F>ho PSNR p<>es <option>subq=1</option>.
|
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To je obvykle ji<6A> viditeln<6C>.
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</para>
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</sect2>
|
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|
|
<sect2 id="menc-feat-x264-encoding-options">
|
|
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|
|
<title>Enk<EFBFBD>dovac<EFBFBD> volby x264</title>
|
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|
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|
<itemizedlist>
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|
|
<listitem><para>
|
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|
|
<emphasis role="bold">frameref</emphasis>:
|
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|
V<>choz<6F> nastaven<65> <option>frameref</option> je 1, ale nem<65>lo by to b<>t br<62>no
|
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|
tak, <20>e je rozumn<6D> nastavovat jej na 1.
|
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|
Pouh<75> zv<7A><76>en<65> <option>frameref</option> na 2 z<>sk<73> okolo
|
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|
|
0.15dB PSNR s 5-10% spomalen<65>m, co<63> je z<>ejm<6A> dobr<62> obchod.
|
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|
|
<option>frameref=3</option> z<>sk<73> kolem 0.25dB PSNR nav<61>c k
|
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|
<option>frameref=1</option>, co<63> ji<6A> m<><6D>e b<>t viditeln<6C>
|
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|
rozd<7A>l.
|
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|
<option>frameref=3</option> je asi o 15% pomalej<65><6A> ne<6E>
|
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|
<option>frameref=1</option>.
|
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|
Nane<6E>t<EFBFBD>st<73> se zisk rychle vytr<74>c<EFBFBD>.
|
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|
Pr<50> <option>frameref=6</option> m<><6D>ete o<>ek<65>vat zisk pouze
|
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|
|
0.05-0.1 dB nad <option>frameref=3</option> p<>i dodate<74>n<EFBFBD>m
|
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|
|
15% zpomalen<65>.
|
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|
|
Nad <option>frameref=6</option> je zisk kvality obvykle velmi mal<61>
|
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|
(a<>koli byste m<>li m<>t na pam<61>ti, <20>e se to m<><6D>e v<>razn<7A> li<6C>it v z<>vislosti
|
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|
|
na zdrojov<6F>m materi<72>lu).
|
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|
|
|
V pom<6F>rn<72> typick<63>m p<><70>pad<61> zlep<65><70> <option>frameref=12</option>
|
|
|
|
|
celkov<6F> PSNR o pouh<75> 0.02dB nad <option>frameref=6</option>,
|
|
|
|
|
p<>i spomalen<65> o 15%-20%.
|
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|
P<>i tak vysok<6F>ch hodnot<6F>ch <option>frameref</option> lze <20><>ct pouze
|
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|
jedinou dobrou v<>c, a to <20>e jejich dal<61><6C> zvy<76>ov<6F>n<EFBFBD> t<>m<EFBFBD><6D> nikdy
|
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|
|
|
<emphasis role="bold">nesn<EFBFBD><EFBFBD><EFBFBD></emphasis> PSNR, ale dal<61><6C> zisk kvality
|
|
|
|
|
je st<73><74><EFBFBD> m<><6D>iteln<6C>, nato<74> viditeln<6C>.
|
|
|
|
|
</para>
|
|
|
|
|
<note><title>Pozn<EFBFBD>mka:</title>
|
|
|
|
|
<para>
|
|
|
|
|
Zv<5A><76>en<65> <option>frameref</option> na nem<65>stn<74> vysokou hodnotu
|
|
|
|
|
<emphasis role="bold">m<EFBFBD><EFBFBD>e</emphasis> a
|
|
|
|
|
<emphasis role="bold">obvykle taky sn<73><6E><EFBFBD></emphasis>
|
|
|
|
|
efektivitu k<>dov<6F>n<EFBFBD>, pokud vypnete CABAC.
|
|
|
|
|
Se zapnut<75>m CABAC (v<>choz<6F> chov<6F>n<EFBFBD>) se zd<7A> b<>t mo<6D>nost nastavit
|
|
|
|
|
<option>frameref</option> "p<><70>li<6C> vysoko" p<><70>li<6C> vzd<7A>len<65> na to,
|
|
|
|
|
abyste se t<>m museli tr<74>pit a v budoucnu mohou optimalizace
|
|
|
|
|
tuto mo<6D>nost zcela vylou<6F>it.
|
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|
|
|
</para>
|
|
|
|
|
</note>
|
|
|
|
|
<para>
|
|
|
|
|
Pokud v<>m z<>le<6C><65> na rychlosti, b<>v<EFBFBD> vhodn<64>m kompromisem pou<6F><75>t
|
|
|
|
|
n<>zk<7A> hodnoty <option>subq</option> a <option>frameref</option>
|
|
|
|
|
v prvn<76>m pr<70>chodu a zv<7A><76>it je ve druh<75>m.
|
|
|
|
|
Typicky to m<> zanedbateln<6C> z<>porn<72> vliv na kone<6E>nou kvalitu:
|
|
|
|
|
pravd<76>podobn<62> strat<61>te m<>n<EFBFBD> ne<6E> 0.1dB PSNR, co<63> by m<>l b<>t a<> p<><70>li<6C>
|
|
|
|
|
mal<61> rozd<7A>l, ne<6E> aby byl vid<69>t.
|
|
|
|
|
Odli<6C>n<EFBFBD> hodnoty <option>frameref</option> v<>ak mohou m<>sty ovlivnit
|
|
|
|
|
volbu typu sn<73>mku.
|
|
|
|
|
Nejsp<73><70> to budou ojedin<69>l<EFBFBD> p<><70>pady, ale chcete-li si b<>t zcela jisti,
|
|
|
|
|
zjist<73>te, jestli va<76>e video obsahuje bu<62> bl<62>skav<61> vzory p<>es celou obrazovku,
|
|
|
|
|
nebo rozs<7A>hl<68> kr<6B>tkodob<6F> zm<7A>ny, kter<65> by mohly vynutit I-sn<73>mek.
|
|
|
|
|
Nastavte <option>frameref</option> pro prvn<76> pr<70>chod tak, aby byl
|
|
|
|
|
dostate<74>n<EFBFBD> velk<6C> pro pokryt<79> doby bliknut<75> (nebo zm<7A>ny).
|
|
|
|
|
Nap<61><70>klad, pokud sc<73>na p<>ep<65>n<EFBFBD> tam a zp<7A>t mezi dv<64>ma obr<62>zky p<>es t<>i sn<73>mky,
|
|
|
|
|
nastavte <option>frameref</option> pro prvn<76> pr<70>chod na 3 a v<>ce.
|
|
|
|
|
Tento p<><70>pad je nejsp<73><70> zcela ojedin<69>l<EFBFBD> v hran<61>ch filmech, ale ob<6F>as se
|
|
|
|
|
vyskytuje v z<>znamech z videoher.
|
|
|
|
|
</para></listitem>
|
|
|
|
|
|
|
|
|
|
<listitem><para>
|
|
|
|
|
<emphasis role="bold">bframes</emphasis>:
|
|
|
|
|
Pou<6F>itelnost B-sn<73>mk<6D> je ve v<>t<EFBFBD>in<69> ostatn<74>ch kodek<65> diskutabiln<6C>.
|
|
|
|
|
V H.264 se to zm<7A>nilo: jsou zde nov<6F> techniky a typy blok<6F> pro pou<6F>it<69>
|
|
|
|
|
v B-sn<73>mc<6D>ch.
|
|
|
|
|
Obvykle i naivn<76> algoritmus pro v<>b<EFBFBD>r B-sn<73>mku m<><6D>e zajistit znateln<6C>
|
|
|
|
|
zisk PSNR.
|
|
|
|
|
Tak<61> je zaj<61>mav<61>, <20>e pokud vypnete adaptivn<76> rozhodov<6F>n<EFBFBD> o B-sn<73>mku
|
|
|
|
|
(<option>nob_adapt</option>), zv<7A><76><EFBFBD> obvykle enk<6E>dov<6F>n<EFBFBD> s
|
|
|
|
|
<option>bframes</option> o trochu rychlost enk<6E>dov<6F>n<EFBFBD>.
|
|
|
|
|
</para>
|
|
|
|
|
<para>
|
|
|
|
|
S vypnut<75>m adaptivn<76>m rozhodov<6F>n<EFBFBD>m o B-sn<73>mku
|
|
|
|
|
(<option>x264encopts</option>'s <option>nob_adapt</option>),
|
|
|
|
|
se optim<69>ln<6C> hodnota t<>to volby obvykle pohybuje od
|
|
|
|
|
<option>bframes=1</option> do <option>bframes=3</option>.
|
|
|
|
|
Se zapnut<75>m adaptivn<76>m rozhodov<6F>n<EFBFBD>m o B-sn<73>mku (v<>choz<6F> chov<6F>n<EFBFBD>),
|
|
|
|
|
je obvykle bezpe<70>n<EFBFBD> pou<6F><75>t vy<76><79><EFBFBD> hodnoty; enkod<6F>r se pokus<75> sn<73><6E>it
|
|
|
|
|
pou<6F>it<69> B-sn<73>mk<6D> ve sc<73>n<EFBFBD>ch, kde by sn<73><6E>ily kompresi.
|
|
|
|
|
</para>
|
|
|
|
|
<para>
|
|
|
|
|
Pokud v<>bec pou<6F>ijete <option>bframes</option>, zva<76>te
|
|
|
|
|
nastaven<65> maxim<69>ln<6C>ho po<70>tu B-sn<73>mk<6D> na 2 nebo v<>ce, pokud chcete
|
|
|
|
|
t<><74>it z v<><76>en<65> predikce.
|
|
|
|
|
</para></listitem>
|
|
|
|
|
|
|
|
|
|
<listitem><para>
|
|
|
|
|
<emphasis role="bold">b_adapt</emphasis>:
|
|
|
|
|
Pozn<7A>mka: ve v<>choz<6F>m stavu zapnuto.
|
|
|
|
|
</para>
|
|
|
|
|
<para>
|
|
|
|
|
Je-li tato volba zapnuta, bude enkod<6F>r pou<6F><75>vat jendoduchou
|
|
|
|
|
heuristiku pro sn<73><6E>en<65> po<70>tu B-sn<73>mk<6D> ve sc<73>n<EFBFBD>ch, kde by jejich
|
|
|
|
|
pou<6F>it<69>m p<><70>li<6C> nez<65>skaly.
|
|
|
|
|
M<><4D>ete pou<6F><75>t <option>b_bias</option> pro nastaven<65> jak p<><70>telsk<73>
|
|
|
|
|
bude enkod<6F>r k B-sn<73>mk<6D>m.
|
|
|
|
|
Spomalen<65> p<>soben<65> adaptivn<76>mi B-sn<73>mky je nyn<79> sp<73><70>e mal<61>, ale
|
|
|
|
|
stejn<6A> tak potenci<63>ln<6C> zisk kvality.
|
|
|
|
|
Obvykle v<>ak nijak ne<6E>kod<6F>.
|
|
|
|
|
Poznamenejme, <20>e ovliv<69>uje rychlost a rozhodov<6F>n<EFBFBD> o typu sn<73>mku pouze
|
|
|
|
|
v prvn<76>m pr<70>chodu.
|
|
|
|
|
<option>b_adapt</option> a <option>b_bias</option> nemaj<61> <20><>dn<64> vliv
|
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v n<>slydn<64>ch pr<70>chodech.
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</para></listitem>
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<listitem><para>
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<emphasis role="bold">b_pyramid</emphasis>:
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Pokud pou<6F><75>v<EFBFBD>te >2 B-sn<73>mky, m<><6D>ete tak<61> zapnout tuto volbu; jak
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<20><>k<EFBFBD> man str<74>nka, dostanete mal<61> zv<7A><76>en<65> kvality bez ztr<74>ty rychlosti.
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Poznamenejme, <20>e tato videa nelze <20><>st dekod<6F>ry zalo<6C>en<65>mi na libavcodec
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star<61><72>mi ne<6E> 5. b<>ezna 2005.
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</para></listitem>
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<listitem><para>
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<emphasis role="bold">weight_b</emphasis>:
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V typick<63>ch p<><70>padech tato volba nep<65>in<69><6E><EFBFBD> velk<6C> zisk.
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V prol<6F>nac<61>ch nebo stm<74>vac<61>ch sc<73>n<EFBFBD>ch v<>ak v<><76>en<65> predikce
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umo<6D><6F>uje pom<6F>rn<72> velkou <20>sporu datov<6F>ho toku.
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V MPEG-4 ASP b<>v<EFBFBD> stm<74>v<EFBFBD>n<EFBFBD> obvykle nejl<6A>pe k<>dov<6F>no jako s<>rie
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velk<6C>ch I-sn<73>mk<6D>; pou<6F>it<69> v<><76>en<65> predikce v B-sn<73>mc<6D>ch umo<6D><6F>uje
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zm<7A>nit alespo<70> n<>kter<65> z nich na rozumn<6D> men<65><6E> B-sn<73>mky.
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Spomalen<65> enk<6E>dov<6F>n<EFBFBD> se zd<7A> b<>t minim<69>ln<6C>, pokud n<>jak<61> je.
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Rovn<76><6E>, v rozporu s t<>m, co si n<>kte<74><65> lid<69> mohou myslet,
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po<70>adavky dekod<6F>ru na CPU nejsou v<><76>enou predikc<6B> ovlivn<76>ny,
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ostatn<74> mo<6D>nosti jsou stejn<6A> n<>ro<72>n<EFBFBD>.
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</para>
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<para>
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Nane<6E>t<EFBFBD>st<73> m<> aktu<74>ln<6C> algoritmus adaptivn<76>ho rozhodov<6F>n<EFBFBD> o B-sn<73>mc<6D>ch
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v<>raznou tendenci vyvarovat se B-sn<73>mk<6D> p<>i stm<74>v<EFBFBD>n<EFBFBD>.
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Dokud se to nezm<7A>n<EFBFBD>, bude dobr<62> p<>idat
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<option>nob_adapt</option> do x264encopts, pokud o<>ek<65>v<EFBFBD>te, <20>e stm<74>v<EFBFBD>n<EFBFBD>
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bude m<>t znateln<6C> vliv ve va<76>em konkr<6B>tn<74>m klipu.
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</para></listitem>
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<listitem><para>
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<emphasis role="bold">deblockalpha, deblockbeta</emphasis>:
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Toto bude pon<6F>kud kontroverzn<7A>.
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</para>
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<para>
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H.264 definuje jednoduchou deblokuj<75>c<EFBFBD> proceduru na I-bloc<6F>ch, kter<65>
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pou<6F><75>v<EFBFBD> p<>ednastaven<65> s<>ly a prahy na QP dan<61>ho bloku.
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Ve v<>choz<6F>m stavu jsou bloky s n<>zk<7A>m QP siln<6C> filtrov<6F>ny a bloky s
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n<>zk<7A>m QP nejsou deblokov<6F>ny v<>bec.
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P<>ednastaven<65> s<>ly definovan<61> standardem jsou dob<6F>e voleny a
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odchylky jsou velmi dobr<62>, tak<61>e jsou PSNR optim<69>ln<6C> pro jak<61>koli
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video, kter<65> zkou<6F><75>te enk<6E>dovat.
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Volby <option>deblockalpha</option> a <option>deblockbeta</option>
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v<>m umo<6D>n<EFBFBD> nastavit odchylky p<>ednastaven<65>ch deblokovac<61>ch prah<61>.
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</para>
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<para>
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Zd<5A> se, <20>e si mnoho lid<69> mysl<73>, <20>e je vhodn<64> v<>razn<7A> sn<73><6E>it s<>lu (<28>ekn<6B>me, -3)
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deblokovac<61>ho filtru.
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To v<>ak nen<65> t<>m<EFBFBD><6D> nikdy dobr<62> n<>pad a v mnoha p<><70>padech lid<69>, kte<74><65>
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tak <20>in<69>, dob<6F>e nerozum<75> jak v<>choz<6F> deblokov<6F>n<EFBFBD> pracuje.
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</para>
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<para>
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Prvn<76> a nejd<6A>le<6C>it<69>j<EFBFBD><6A> v<>c, kterou byste m<>li o in-loop deblokovac<61>m
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filtru v<>d<EFBFBD>t je, <20>e v<>choz<6F> nastaven<65> prah<61> je t<>m<EFBFBD><6D> v<>dy optim<69>ln<6C>
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vzhledem k PSNR.
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V <20><>dk<64>ch p<><70>padech kdy nen<65>, je ide<64>ln<6C> odchylka plus m<>nus 1.
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Zm<5A>na deblokuj<75>c<EFBFBD>ch parametr<74> o v<>t<EFBFBD><74> hodnotu vede t<>m<EFBFBD><6D> s jistotou
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ke zhor<6F>en<65> PSNR.
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Zes<65>len<65> filtru set<65>e v<>ce detail<69>; zeslaben<65> zv<7A><76><EFBFBD> viditelnost <20>tvere<72>kov<6F>n<EFBFBD>.
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</para>
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<para>
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Rozhodn<64> je nevhodn<64> sni<6E>ovat deblokovac<61> prahy, pokud m<> va<76>e video
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n<>zkou prostorovou komplexnost (<28>ili nemnoho detail<69> nebo <20>umu).
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In-loop filtr t<>m<EFBFBD><6D> perfektn<74> kryje artefakty, kter<65> se vyskytnou.
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Pokud m<> v<>ak zdroj vysokou prostorovou komplexnost, jsou artefakty
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h<><68>e rozeznateln<6C>.
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To proto, <20>e krou<6F>kov<6F>n<EFBFBD> m<> tendenci vypadat jako detail nebo <20>um.
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Lidsk<73> vizu<7A>ln<6C> vn<76>mavost si snadno pov<6F>imne, kdy<64> je odstran<61>n detail,
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ale obt<62><74>n<EFBFBD>ji si v<>imne, kdy<64> je <20>patn<74> reprezentov<6F>n <20>um.
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Kdy<64> p<><70>jde na subjektivn<76> kvalitu, je <20>um <20><>ste<74>n<EFBFBD> zam<61>niteln<6C> s detaily.
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Sn<53><6E>en<65>m s<>ly deblokovac<61>ho filtru nejsp<73><70>e zv<7A><76><EFBFBD>te chybu p<>id<69>n<EFBFBD>m
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krou<6F>kov<6F>ch artefakt<6B>, ale oko si toho nev<65>imne, proto<74>e si splete
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artefakty s detaily.
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</para>
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<para>
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To v<>ak <emphasis role="bold">st<EFBFBD>le</emphasis> neospravedl<64>uje
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sn<73><6E>en<65> s<>ly deblokovac<61>ho filtru.
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|
Obecn<63> dostanete kvalitn<74>j<EFBFBD><6A> <20>um z postprocesingu.
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Pokud va<76>e H.264 videa vypadaj<61> p<><70>li<6C> rozmazan<61> nebo flekat<61>, zkuste si
|
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pohr<68>t s
|
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<option>-vf noise</option> p<>i p<>ehr<68>v<EFBFBD>n<EFBFBD>.
|
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|
<option>-vf noise=8a:4a</option> by m<>lo zamaskovat v<>t<EFBFBD>inu smazan<61>ch
|
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artefak<61>.
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T<>m<EFBFBD><6D> jist<73> to bude vypadat l<>pe ne<6E> to, co dostanete pomoc<6F>
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podv<64>d<EFBFBD>n<EFBFBD> deblokovac<61>ho filtru.
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</para></listitem>
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|
</itemizedlist>
|
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|
|
</sect2>
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|
|
</sect1>
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|
2005-04-20 07:41:24 +00:00
|
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|
<sect1 id="menc-feat-telecine">
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<title>Jak nalo<6C>it s telecine a prokladem v NTSC DVD</title>
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|
<sect2 id="menc-feat-telecine-intro">
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<title>P<EFBFBD>edstaven<EFBFBD></title>
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|
<formalpara>
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|
|
<title>Co je to telecine?</title>
|
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<para>
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|
Pokud moc nerozum<75>te tomu, co je naps<70>no v tomto dokumentu, doporu<72>ujeme
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|
nav<61>t<EFBFBD>vit tuto str<74>nku:
|
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|
|
<ulink url="http://www.divx.com/support/guides/guide.php?gid=10">http://www.divx.com/support/guides/guide.php?gid=10</ulink>
|
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|
|
Na t<>to adrese je srozumiteln<6C> a rozumn<6D> vy<76>erp<72>vaj<61>c<EFBFBD> popis co je to
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telecine.
|
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|
</para></formalpara>
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<formalpara>
|
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<title>Pozn<EFBFBD>mka k <20><>sl<73>m.</title>
|
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|
<para>
|
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|
Mnoho dokument<6E>, v<>etn<74> v<><76>e odkazovan<61> p<><70>ru<72>ky, ud<75>v<EFBFBD> hodnotu p<>lsn<73>mk<6D> za
|
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|
|
sekundu NTSC videa jako 59.94 a odpov<6F>daj<61>c<EFBFBD> sn<73>mky za sekundu jako 29.97
|
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|
|
(pro telecinovan<61> a prokl<6B>dan<61> video) a 23.976 (pro neprokl<6B>dan<61>).
|
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|
|
Pro jednoduchost n<>kter<65> dokumenty zaokrouhluj<75> tyto hodnoty na 60, 30 a 24.
|
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|
</para></formalpara>
|
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<para>
|
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|
P<>esn<73> <20>e<EFBFBD>eno jsou v<>echny tyto <20><>sla p<>ibli<6C>n<EFBFBD>. <20>ernob<6F>l<EFBFBD> NTSC video m<>lo
|
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p<>esn<73> 60 p<>lsn<73>mk<6D> za sekundu, ale pozd<7A>ji byla zvolena hodnota 60000/1001,
|
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|
aby bylo mo<6D>n<EFBFBD> p<>idat barevn<76> data a z<>stat kompatibiln<6C> se star<61>mi
|
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|
|
<20>ernob<6F>l<EFBFBD>mi televizemi. Digit<69>ln<6C> NTSC (jak je na DVD) m<> rovn<76><6E> rychlost
|
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60000/1001 p<>lsn<73>mk<6D> za sekundu. Z toho vypl<70>v<EFBFBD>, <20>e prokl<6B>dan<61> a telecinovan<61>
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|
video m<> 30000/1001 sn<73>mk<6D> za sekundu; neprokl<6B>dan<61> video m<> 24000/1001 sn<73>mk<6D>
|
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|
za sekundu.
|
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|
|
</para>
|
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|
<para>
|
|
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|
|
Star<61><72> verze dokumentace <application>MEncoder</application>u a mnoho zpr<70>v
|
|
|
|
|
v archivu konference hovo<76><6F> o 59.94, 29.97 a 23.976.
|
|
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|
|
V<>echna dokumentace <application>MEncoder</application>u byla aktualizov<6F>na
|
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|
|
a pou<6F><75>v<EFBFBD> zlomkov<6F>ch hodnot. Vy byste je m<>li pou<6F><75>vat tak<61>.
|
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|
|
</para>
|
|
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|
|
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|
|
<para>
|
|
|
|
|
<option>-ofps 23.976</option> je nespr<70>vn<76>.
|
|
|
|
|
M<>sto toho byste m<>li pou<6F><75>t <option>-ofps 24000/1001</option>.
|
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|
|
</para>
|
|
|
|
|
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|
|
|
<formalpara>
|
|
|
|
|
<title>Jak je pou<6F><75>v<EFBFBD>no telecine.</title>
|
|
|
|
|
<para>
|
|
|
|
|
Ve<56>ker<65> video ur<75>en<65> k zobrazen<65> na NTSC televizi mus<75> m<>t 60000/1001
|
|
|
|
|
p<>lsn<73>mk<6D> za sekundu. Filmy vyr<79>b<EFBFBD>n<EFBFBD> pro televizi jsou <20>asto nat<61><74>eny p<><70>mo
|
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|
|
ve 60000/1001 p<>lsn<73>mc<6D>ch za sekundu, ale v<>t<EFBFBD>ina film<6C> do kin je nat<61><74>ena p<>i
|
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|
|
24 nebo 24000/1001 sn<73>mc<6D>ch za sekundu. Kdy<64> je film p<>episov<6F>n na DVD, je
|
|
|
|
|
video upraveno pro televizi v procesu zvan<61>m telecine.
|
|
|
|
|
</para></formalpara>
|
|
|
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|
|
|
|
|
|
<para>
|
|
|
|
|
Na DVD nen<65> video ve skute<74>nosti nikdy ulo<6C>eno v 60000/1001 p<>lsn<73>mc<6D>ch za
|
|
|
|
|
sekundu. Video je<6A> bylo p<>vodn<64> 60000/1001, bude m<>t ka<6B>d<EFBFBD> p<>r p<>lsn<73>mk<6D>
|
|
|
|
|
zkombinov<6F>n do podoby sn<73>mku s rychlost<73> 30000/1001 sn<73>mk<6D> za sekundu.
|
|
|
|
|
Hardwarov<6F> DVD p<>ehr<68>va<76>e pak <20>tou p<><70>znak, zabudovan<61> ve video proudu, kter<65>
|
|
|
|
|
ud<75>v<EFBFBD> jestli prvn<76> p<>lsn<73>mek tvo<76><6F> lich<63> nebo sud<75> <20><>dky.
|
|
|
|
|
</para>
|
|
|
|
|
|
|
|
|
|
<para>
|
|
|
|
|
Obsah ve 24000/1001 sn<73>mc<6D>ch za sekundu obvykle z<>st<73>v<EFBFBD> tak jak byl v dob<6F>
|
|
|
|
|
p<>episu na DVD a DVD p<>ehr<68>va<76> mus<75> prov<6F>st telecine za letu. N<>kdy je v<>ak
|
|
|
|
|
video telecinov<6F>no <emphasis>p<EFBFBD>ed</emphasis> ulo<6C>en<65>m na DVD; dokonce i kdy<64>
|
|
|
|
|
m<>lo p<>vodn<64> 24000/1001 sn<73>mk<6D> za sekundu, bude m<>t 60000/1001 p<>lsn<73>mk<6D> za
|
|
|
|
|
sekundu. Pokud je ulo<6C>en na DVD, p<>ry p<>lsn<73>mk<6D> jsou zkombinov<6F>ny do formy
|
|
|
|
|
30000/1001 sn<73>mk<6D> za sekundu.
|
|
|
|
|
</para>
|
|
|
|
|
|
|
|
|
|
<para>
|
|
|
|
|
Kdy<64> se pod<6F>v<EFBFBD>me na jednotliv<69> sn<73>mky vznikl<6B> z videa o 60000/10001 p<>lsn<73>mc<6D>ch
|
|
|
|
|
za sekundu, telecinovan<61>ho nebo ne, je z<>eteln<6C> vid<69>t toto prokl<6B>d<EFBFBD>n<EFBFBD> jakmile
|
|
|
|
|
je zde n<>jak<61> pohyb, jeliko<6B> jeden p<>lsn<73>mek (<28>ekn<6B>me lich<63> <20><>dky)
|
|
|
|
|
reprezentuje <20>asov<6F> okam<61>ik o 1/(60000/1001) sekundy pozd<7A>j<EFBFBD><6A> ne<6E> ten druh<75>.
|
|
|
|
|
P<>ehr<68>v<EFBFBD>n<EFBFBD> prokl<6B>dan<61>ho videa na po<70><6F>ta<74>i vypad<61> <20>kared<65> jak proto, <20>e monitor
|
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|
|
m<> vy<76><79><EFBFBD> rozli<6C>en<65>, ale i proto<74>e video je zobrazov<6F>no sn<73>mek po sn<73>mku m<>sto
|
|
|
|
|
p<>lsn<73>mek po p<>lsn<73>mku.
|
|
|
|
|
</para>
|
|
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|
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|
|
<itemizedlist>
|
|
|
|
|
<title>Pozn<EFBFBD>mky:</title>
|
|
|
|
|
<listitem><para>
|
|
|
|
|
Tento odstavec plat<61> pouze pro NTSC DVD, nikoli PAL.
|
|
|
|
|
</para></listitem>
|
|
|
|
|
<listitem><para>
|
|
|
|
|
<20><>dky s p<><70>klady spu<70>t<EFBFBD>n<EFBFBD> <application>MEncoder</application>u v dokumentu
|
|
|
|
|
<emphasis role="bold">nejsou</emphasis> ur<75>eny pro opravdov<6F> pou<6F>it<69>.
|
|
|
|
|
Obsahuj<75> pouze nutn<74> minimum vy<76>adovan<61> pro enk<6E>dov<6F>n<EFBFBD> p<><70>slu<6C>n<EFBFBD> ke kategorii
|
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|
videa. Jak d<>lat dobr<62> DVD ripy nebo doladit
|
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<systemitem class="library">libavcodec</systemitem> pro maxim<69>ln<6C> kvalitu
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nen<65> v z<>b<EFBFBD>ru tohoto dokumentu.
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</para></listitem>
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<listitem><para>
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Pozn<7A>mky pod <20>arou p<><70>slu<6C>n<EFBFBD> pro tuto p<><70>ru<72>ku jsou linkov<6F>ny takto:
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<link linkend="menc-feat-telecine-footnotes">[1]</link>
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</para></listitem>
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</itemizedlist>
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</sect2>
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<sect2 id="menc-feat-telecine-ident">
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<title>Jak zjistit o jak<61> typ videa se jedn<64></title>
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<sect3 id="menc-feat-telecine-ident-progressive">
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<title>Progresivn<EFBFBD> (neprokl<6B>dan<61>)</title>
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<para>
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Progresivn<76> video je p<>vodn<64> nato<74>eno p<>i 24000/1001 sn<73>mc<6D>ch za sekundu a
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ulo<6C>eno na DVD beze zm<7A>n.
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</para>
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<para>
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Kdy<64> p<>ehrajete progresivn<76> DVD v <application>MPlayer</application>u,
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<application>MPlayer</application> vyp<79><70>e n<>sleduj<75>c<EFBFBD> <20><>dek jakmile za<7A>ne
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p<>ehr<68>vat:
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<screen> demux_mpg: 24000/1001 fps progressive NTSC content detected, switching framerate.</screen>
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Od tohoto okam<61>iku by demux_mpg nem<65>l nikdy <20><>ct <20>e na<6E>el
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"30000/1001 fps NTSC obsah."
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</para>
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<para>
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Kdy<64> sledujete progresivn<76> video, nem<65>li byste nikdy vid<69>t <20><>dn<64> proklad.
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Dejte si ale pozor, jeliko<6B> je ob<6F>as tro<72>ku telecine namixov<6F>no tam, kde byste
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to v<>bec ne<6E>ekali. Setkal jsem se s TV show na DVD, kter<65> m<>ly sekundu
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telecine p<>i ka<6B>d<EFBFBD> zm<7A>n<EFBFBD> sc<73>ny nebo na zcela n<>hodn<64>ch m<>stech. Jednou jsem se
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d<>val na DVD, kter<65> bylo do p<>lky progresivn<76> a od p<>lky telecinov<6F>no. Pokud
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chcete b<>t <emphasis>opravdu</emphasis> d<>kladn<64>, m<><6D>ete oskenovat cel<65> film:
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<screen>mplayer dvd://1 -nosound -vo null -benchmark</screen>
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Pou<6F>it<69> volby <option>-benchmark</option> nech<63>
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<application>MPlayer</application> p<>ehr<68>t film tak rychle, jak je to jen
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mo<6D>n<EFBFBD>; stejn<6A> to ale, v z<>vislosti na va<76>em stroji, chv<68>li potrv<72>.
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V<>dy, kdy<64> demux_mpg ohl<68>s<EFBFBD> zm<7A>nu sn<73>mkov<6F> rychlosti, <20><>dek t<>sn<73> nad hl<68><6C>en<65>m
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uk<75><6B>e <20>as ve kter<65>m ke zm<7A>n<EFBFBD> do<64>lo.
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</para>
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<para>
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Ob<4F>as je progresivn<76> video na DVD ozna<6E>eno jako
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"soft-telecine" proto<74>e je zam<61><6D>leno, aby telecine provedl DVD
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p<>ehr<68>va<76>.
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</para>
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</sect3>
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<sect3 id="menc-feat-telecine-ident-telecined">
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<title>Telecinov<EFBFBD>no (p<>eps<70>no pro NTSC televizi)</title>
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<para>
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Telecinovan<61> video bylo p<>vodn<64> nato<74>eno p<>i 24000/1001, ale bylo telecinov<6F>no
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<emphasis>p<EFBFBD>ed</emphasis> z<>pisem na DVD.
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</para>
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<para>
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<application>MPlayer</application> (nikdy) nehl<68>s<EFBFBD> <20><>dnou zm<7A>nu sn<73>mkov<6F>
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rychlosti, kdy<64> p<>ehr<68>v<EFBFBD> telecinovan<61> video.
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</para>
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<para>
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P<>i sledov<6F>n<EFBFBD> telecinovan<61>ho videa uvid<69>te prokladov<6F> artefakty, kter<65> jako by
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"blikaly": opakovan<61> miz<69> a objevuj<75> se.
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Bl<42><6C>e se na to m<><6D>ete pod<6F>vat:
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<orderedlist>
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<listitem>
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<screen>mplayer dvd://1</screen>
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</listitem>
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<listitem><para>
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P<>evi<76>te na <20><>st s pohybem.
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</para></listitem>
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<listitem><para>
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Pou<6F>ijte kl<6B>vesu <keycap>.</keycap> pro krokov<6F>n<EFBFBD> po jednom sn<73>mku.
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</para></listitem>
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<listitem><para>
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Sledujte vzor prokl<6B>dan<61> vypadaj<61>c<EFBFBD>ch a progresivn<76> vypadaj<61>c<EFBFBD>ch sn<73>mk<6D>.
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Pokud je vzor, kter<65> sledujete PPPII,PPPII,PPPII,..., pak je video
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telecinov<6F>no. Pokud vid<69>te jin<69> vzor, pak mohlo b<>t video telecinov<6F>no
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pou<6F>it<69>m n<>jak<61> nestandardn<64> metody; <application>MEncoder</application>
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neum<75> bezztr<74>tov<6F> p<>ev<65>st nestandardn<64> telecine do progresivn<76>ho. Pokud
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nevid<69>te <20><>dn<64> vzor, pak je video nejsp<73><70> prokl<6B>dan<61>.
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</para></listitem>
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</orderedlist>
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</para>
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<para>
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N<>kdy je telecinovan<61> video na DVD ozna<6E>eno jako "hard-telecine".
|
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Jeliko<6B> hard-telecine ji<6A> je ve 60000/1001 p<>lsn<73>mc<6D>ch za sekundu, DVD
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p<>ehr<68>va<76> p<>ehraje video bez jak<61>chkoli manipulac<61>.
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</para>
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</sect3>
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<sect3 id="menc-feat-telecine-ident-interlaced">
|
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<title>Prokl<EFBFBD>dan<EFBFBD></title>
|
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<para>
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|
Prokl<6B>dan<61> video bylo od sam<61>ho za<7A><61>tku filmov<6F>no p<>i 60000/1001 p<>lsn<73>mc<6D>ch
|
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|
za sekundu a ulo<6C>eno na DVD ve 30000/1001 sn<73>mc<6D>ch za sekundu. Efekt
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|
prokl<6B>d<EFBFBD>n<EFBFBD> (<28>asto ozna<6E>ovan<61> jako "rozt<EFBFBD>epen<EFBFBD>") je v<>sledkem
|
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|
skl<6B>d<EFBFBD>n<EFBFBD> p<>lsn<73>mk<6D> do sn<73>mk<6D>. Vzd<7A>lenost mezi p<>lsn<73>mky m<> b<>t 1/(60000/1001)
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sekundy a proto kdy<64> jsou zobrazeny sou<6F>asn<73>, je rozd<7A>l jasn<73> patrn<72>.
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|
</para>
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<para>
|
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|
Stejn<6A> jako u telecinovan<61>ho videa by <application>MPlayer</application> nem<65>l
|
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|
hl<68>sit jak<61>koli zm<7A>ny sn<73>mkov<6F> rychlosti p<>i p<>ehr<68>v<EFBFBD>n<EFBFBD> prokl<6B>dan<61>ho obsahu.
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|
</para>
|
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<para>
|
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|
Kdy<64> si prohl<68>dnete video bl<62><6C>e pomoc<6F> krokov<6F>n<EFBFBD> sn<73>mk<6D> pomoc<6F> kl<6B>vesy
|
|
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|
<keycap>.</keycap>, uvid<69>te, <20>e ka<6B>d<EFBFBD> jednotliv<69> sn<73>mek je prokl<6B>dan<61>.
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|
</para>
|
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|
</sect3>
|
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|
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|
<sect3 id="menc-feat-telecine-ident-mixedpt">
|
|
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|
|
<title>Sm<EFBFBD><EFBFBD>en<EFBFBD> progresivn<76> a telecinovan<61></title>
|
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|
|
|
<para>
|
|
|
|
|
Ve<56>ker<65> obsah "sm<EFBFBD><EFBFBD>en<EFBFBD>ho progresivn<76>ho a telecinovan<61>ho" videa m<>l
|
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|
p<>vodn<64> 24000/1001 sn<73>mk<6D> za sekundu, ale n<>kter<65> <20><>sti pro<72>ly telecine.
|
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|
|
</para>
|
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|
<para>
|
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|
|
Kdy<64> <application>MPlayer</application> p<>ehr<68>v<EFBFBD> tuto kategorii, bude (<28>asto
|
|
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|
|
i opakovan<61>) p<>ep<65>nat mezi "30000/1001 sn<73>mky/s NTSC"
|
|
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|
|
a "24000/1001 sn<73>mky/s progresivn<76>m NTSC". Sledujte spodek
|
|
|
|
|
<application>MPlayer</application>ova v<>stupu, abyste zachytili tyto zpr<70>vy.
|
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|
</para>
|
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<para>
|
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|
M<>li byste prov<6F><76>it <20><>sti se "30000/1001 sn<73>mky/s NTSC", abyste m<>li
|
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|
jistotu, <20>e jsou skute<74>n<EFBFBD> telecinov<6F>ny a ne jen prokl<6B>dan<61>.
|
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|
</para>
|
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|
|
</sect3>
|
|
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|
|
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|
|
<sect3 id="menc-feat-telecine-ident-mixedpi">
|
|
|
|
|
<title>Sm<EFBFBD><EFBFBD>en<EFBFBD> progresivn<76> a prokl<6B>dan<61></title>
|
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|
<para>
|
|
|
|
|
Ve "sm<EFBFBD><EFBFBD>en<EFBFBD>m progresivn<76>m a prokl<6B>dan<61>m" obsahu bylo progresivn<76> a
|
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|
prokl<6B>dan<61> video spl<70>c<EFBFBD>no dohromady.
|
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|
</para>
|
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|
<para>
|
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|
|
Tato kategorie vypad<61> jako "sm<EFBFBD><EFBFBD>en<EFBFBD> progresivn<76> a telecine",
|
|
|
|
|
dokud si neprohl<68>dnete <20><>sti se 30000/1001 sn<73>mky/s a neuvid<69>te, <20>e nemaj<61>
|
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|
|
|
telecine vzor.
|
|
|
|
|
</para>
|
|
|
|
|
</sect3>
|
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|
|
|
|
|
|
|
</sect2>
|
|
|
|
|
|
|
|
|
|
<sect2 id="menc-feat-telecine-encode">
|
|
|
|
|
<title>Jak enk<6E>dovat jednotliv<69> kategorie</title>
|
|
|
|
|
<para>
|
|
|
|
|
Jak jsem se zm<7A>nil na za<7A><61>tku, p<><70>klady p<><70>kazov<6F>ch <20><>dk<64>
|
|
|
|
|
<application>MEncoder</application>u n<><6E>e <emphasis role="bold">nejsou</emphasis>
|
|
|
|
|
ur<75>eny pro praktick<63> pou<6F>it<69>; pouze demonstruj<75>, minimum voleb nutn<74>ch k tomu,
|
|
|
|
|
abyste spr<70>vn<76> enk<6E>dovali ka<6B>dou kategorii.
|
|
|
|
|
</para>
|
|
|
|
|
|
|
|
|
|
<sect3 id="menc-feat-telecine-encode-progressive">
|
2005-04-20 09:22:27 +00:00
|
|
|
|
<title>Progresivn<EFBFBD></title>
|
2005-04-20 07:41:24 +00:00
|
|
|
|
<para>
|
|
|
|
|
Progresivn<76> video nevy<76>aduje <20><>dn<64> speci<63>ln<6C> filtrov<6F>n<EFBFBD> pro enk<6E>dov<6F>n<EFBFBD>.
|
|
|
|
|
Jedin<69> volba, kter<65> by ur<75>it<69> nem<65>la chyb<79>t je
|
|
|
|
|
<option>-ofps 24000/1001</option>. Jinak se <application>MEncoder</application>
|
|
|
|
|
pokus<75> enk<6E>dovat p<>i 30000/1001 sn<73>mc<6D>ch/s a bude opakovat sn<73>mky.
|
|
|
|
|
</para>
|
|
|
|
|
|
|
|
|
|
<para>
|
|
|
|
|
<screen>mencoder dvd://1 -nosound -ovc lavc -ofps 24000/1001</screen>
|
|
|
|
|
</para>
|
|
|
|
|
|
|
|
|
|
<para>
|
|
|
|
|
<20>asto se st<73>v<EFBFBD>, <20>e video, kter<65> vypad<61> progresivn<76>, m<> v sob<6F> zam<61>ch<63>ny
|
|
|
|
|
krati<74>k<EFBFBD> telecinovan<61> <20><>sti. Pokud si nejste jisti, je nejbezpe<70>n<EFBFBD>j<EFBFBD><6A>
|
|
|
|
|
pova<76>ovat video za
|
|
|
|
|
<link linkend="menc-feat-telecine-encode-mixedpt">sm<EFBFBD><EFBFBD>en<EFBFBD> progresivn<76> a
|
|
|
|
|
telecinovan<61></link>. Ztr<74>ta v<>konu je jen mal<61>
|
|
|
|
|
<link linkend="menc-feat-telecine-footnotes">[3]</link>.
|
|
|
|
|
</para>
|
|
|
|
|
</sect3>
|
|
|
|
|
|
|
|
|
|
<sect3 id="menc-feat-telecine-encode-telecined">
|
|
|
|
|
<title>Telecinovan<EFBFBD></title>
|
|
|
|
|
<para>
|
|
|
|
|
Telecine lze obr<62>tit a dostat tak p<>vodn<64> 24000/1001 obsah, za pou<6F>it<69> metody
|
|
|
|
|
zvan<61> inverzn<7A> telecine.
|
|
|
|
|
<application>MPlayer</application> m<> n<>kolik filtr<74> pr<70>v<EFBFBD> pro tuto <20>innost;
|
|
|
|
|
nejlep<65><70> z t<>chto filtr<74>, <option>pullup</option>, je pops<70>n v <20><>sti
|
|
|
|
|
<link linkend="menc-feat-telecine-encode-mixedpt">sm<EFBFBD><EFBFBD>en<EFBFBD> progresivn<76> a
|
|
|
|
|
telecinovan<61></link>.
|
|
|
|
|
</para>
|
|
|
|
|
</sect3>
|
|
|
|
|
|
|
|
|
|
<sect3 id="menc-feat-telecine-encode-interlaced">
|
|
|
|
|
<title>Prokl<EFBFBD>dan<EFBFBD></title>
|
|
|
|
|
<para>
|
|
|
|
|
V praxi nen<65> v<>t<EFBFBD>inou mo<6D>n<EFBFBD> dostat kompletn<74> progresivn<76> video z prokl<6B>dan<61>ho
|
|
|
|
|
obsahu. Jedin<69> zp<7A>sob jak to ud<75>lat bez ztr<74>ty poloviny svisl<73>ho rozli<6C>en<65> je
|
|
|
|
|
zdvojen<65>m sn<73>mkov<6F> rychlosti a zkusit "odhadnout" co m<>m prov<6F>st
|
|
|
|
|
s odpov<6F>daj<61>c<EFBFBD>mi linkami ka<6B>d<EFBFBD>ho z p<>lsn<73>mk<6D> (m<> to ov<6F>em i nev<65>hody –
|
|
|
|
|
viz metoda 3).
|
|
|
|
|
</para>
|
|
|
|
|
|
|
|
|
|
<orderedlist>
|
|
|
|
|
<listitem><para>
|
|
|
|
|
Enk<6E>dujte video v prokl<6B>dan<61> form<72>. Obvykle prokl<6B>d<EFBFBD>n<EFBFBD> zp<7A>sob<6F> t<><74>kou <20>jmu
|
|
|
|
|
schopnosti enkod<6F>ru dob<6F>e komprimovat, ale
|
|
|
|
|
<systemitem class="library">libavcodec</systemitem> m<> dv<64> volby ur<75>en<65> pr<70>v<EFBFBD>
|
|
|
|
|
pro lep<65><70> ukl<6B>d<EFBFBD>n<EFBFBD> prokl<6B>dan<61>ho videa: <option> ildct</option> a
|
|
|
|
|
<option>ilme</option>. Rovn<76><6E> velmi doporu<72>ujeme pou<6F>it<69> volby
|
|
|
|
|
<option>mbd=2</option> <link linkend="menc-feat-telecine-footnotes">[2] </link>
|
|
|
|
|
proto<74>e bude enk<6E>dovat makrobloky jako neprokl<6B>dan<61> tam, kde nen<65> <20><>dn<64> pohyb.
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Volba <option>-ofps</option> zde <emphasis role="bold">nen<EFBFBD></emphasis> nutn<74>.
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<screen>mencoder dvd://1 -nosound -ovc lavc -lavcopts ildct:ilme:mbd=2</screen>
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</para></listitem>
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<listitem><para>
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Pou<6F>ijte filtr odstra<72>uj<75>c<EFBFBD> proklad p<>ed enk<6E>dov<6F>n<EFBFBD>m. Je jich zde n<>kolik,
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m<><6D>ete si vybrat. Ka<4B>d<EFBFBD> z nich m<> sv<73> pro i proti. Prohl<68>dn<64>te si v<>stup
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<option>mplayer -pphelp</option> abyste zjistili, kter<65> jsou k dispozici
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(grep pro "deint") a vyhledejte
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<ulink url="http://www.mplayerhq.hu/homepage/design6/info.html#mailing_lists">
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e-mailov<6F> konference MPlayeru</ulink>, kde naleznete mnoho diskus<75> o r<>zn<7A>ch
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filtrech. Sn<53>mkov<6F> rychlost se ani zde nem<65>n<EFBFBD>, tak<61>e <20><>dn<64>
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<option>-ofps</option>. Odstran<61>n<EFBFBD> proklady by rovn<76><6E> m<>lo b<>t provedeno po
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o<>ez<65>n<EFBFBD> <link linkend="menc-feat-telecine-footnotes">[1]</link>, ale p<>ed
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<20>k<EFBFBD>lov<6F>n<EFBFBD>m.
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<screen>mencoder dvd://1 -nosound -vf pp=lb -ovc lavc</screen>
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</para></listitem>
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<listitem><para>
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Nane<6E>t<EFBFBD>st<73> je tato volba vadn<64> v <application>MEncoder</application>u;
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m<>la by dob<6F>e pracovat v <application>MEncoder G2</application>, ale ten tu
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zat<61>m nen<65>. Stejn<6A> je ur<75>en<65>m <option> -vf tfields</option> vytvo<76>en<65>
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kompletn<74>ho sn<73>mku z ka<6B>d<EFBFBD>ho p<>lsn<73>mku, co<63> zv<7A><76><EFBFBD> sn<73>mkovou rychlost na
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60000/1001. V<>hoda tohoto p<><70>stupu je v tom, <20>e nep<65>ijdete o <20><>dn<64> data;
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Proto<74>e v<>ak ka<6B>d<EFBFBD> sn<73>mek poch<63>z<EFBFBD> jen z jedin<69>ho p<>lsn<73>mku, mus<75> b<>t chyb<79>j<EFBFBD>c<EFBFBD>
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linky n<>jak dopo<70><6F>t<EFBFBD>ny. Neexistuje mnoho dobr<62>ch metod, generuj<75>c<EFBFBD>ch chyb<79>j<EFBFBD>c<EFBFBD>
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data, tak<61>e v<>sledek bude trochu podobn<62> tomu, kdy<64> se pou<6F>ije n<>kter<65> filtr
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odstra<72>uj<75>c<EFBFBD> proklad.
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Generov<6F>n<EFBFBD>m chyb<79>j<EFBFBD>c<EFBFBD>ch linek vznikaj<61> dal<61><6C> probl<62>my t<>m, <20>e se zdvojn<6A>sob<6F>
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mno<6E>stv<74> dat. Tak<61>e jsou pot<6F>eba vy<76><79><EFBFBD> datov<6F> toky pro enk<6E>dov<6F>n<EFBFBD>, aby byla
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zachov<6F>na kvalita a spot<6F>ebuje se v<>ce v<>konu CPU jak pro enk<6E>dov<6F>n<EFBFBD>, tak pro
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dek<65>dov<6F>n<EFBFBD>. tfields m<> n<>kolik r<>zn<7A>ch voleb pro volbu zp<7A>sobu generov<6F>n<EFBFBD>
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chyb<79>j<EFBFBD>c<EFBFBD>ch linek. Pokud pou<6F>ijete tuto mo<6D>nost, prostudujte si manu<6E>l a
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zvolte si volbu, kter<65> s va<76><61>m materi<72>lem vypad<61> nejl<6A>pe.
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Poznamenejme, <20>e p<>i pou<6F>it<69> <option>tfields</option>
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<emphasis role="bold">mus<EFBFBD>te</emphasis> nastavit <option>-fps</option> a
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<option>-ofps</option> na dvojn<6A>sobek sn<73>mkov<6F> rychlosti origin<69>lu.
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<screen>mencoder dvd://1 -nosound -vf tfields=2 -ovc lavc -fps 60000/1001 -ofps 60000/1001</screen>
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</para></listitem>
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<listitem><para>
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Pokud pl<70>nujete v<>razn<7A> zmen<65>ov<6F>n<EFBFBD>, m<><6D>ete extrahovat a enk<6E>dovat jen jeden
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z p<>lsn<73>mk<6D>. Samoz<6F>ejm<6A> p<>ijdete o polovinu svisl<73>ho rozli<6C>en<65>, ale pokud
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pl<70>nujete zmen<65>en<65> ide<64>ln<6C> na 1/2 origin<69>ln<6C> velikosti, nebude na t<>to ztr<74>t<EFBFBD>
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v<>bec z<>le<6C>et. V<>sledek bude progresivn<76> soubor s 30000/1001 sn<73>mky za sekundu.
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Cel<65> postup spo<70><6F>v<EFBFBD> v pou<6F>it<69> <option>-vf field</option> a n<>sledn<64>m o<>ezu
|
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<link linkend="menc-feat-telecine-footnotes">[1]</link> a p<><70>slu<6C>n<EFBFBD>m
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<20>k<EFBFBD>lov<6F>n<EFBFBD>. Pamatujte, <20>e mus<75>te nastavit scale tak, aby kompenzoval
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zmen<65>en<65> svisl<73>ho rozm<7A>ru na polovinu.
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<screen>mencoder dvd://1 -nosound -vf field=0 -ovc lavc</screen>
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</para></listitem>
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</orderedlist>
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</sect3>
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<sect3 id="menc-feat-telecine-encode-mixedpt">
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<title>Sm<EFBFBD><EFBFBD>en<EFBFBD> progresivn<76> a telecinovan<61></title>
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<para>
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Abychom p<>evedli sm<73><6D>en<65> progresivn<76> a telecinovan<61> video zcela na progresivn<76>
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video, mus<75> b<>t telecinovan<61> <20><>sti inverzn<7A> telecinov<6F>ny. K tomu lze dosp<73>t
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t<>emi postupy popsan<61>mi n<><6E>e.Poznamenejme, <20>e byste m<>li
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<emphasis role="bold">v<EFBFBD>dy</emphasis> prov<6F>st inverzn<7A> telecine p<>ed
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jak<61>mkoliv <20>k<EFBFBD>lov<6F>n<EFBFBD>m; a v p<><70>pad<61>, <20>e p<>esn<73> nev<65>te co d<>l<EFBFBD>te, tak<61> p<>ed
|
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|
o<>ez<65>n<EFBFBD>m <link linkend="menc-feat-telecine-footnotes">[1]</link>.
|
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|
|
Volba <option>-ofps 24000/1001</option> je vy<76>adov<6F>na, proto<74>e v<>stupn<70> video
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|
bude m<>t 24000/1001 sn<73>mk<6D> za sekundu.
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|
</para>
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<itemizedlist>
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<listitem><para>
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|
<option>-vf pullup</option> je navr<76>en tak, aby inverzn<7A> telecinoval, ale
|
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|
|
progresivn<76> data nech<63>val jak jsou. Pro spr<70>vnou funkci
|
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|
<emphasis role="bold">mus<EFBFBD></emphasis> b<>t <option>pullup</option> n<>sledov<6F>n
|
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|
|
filtrem <option>softskip</option>, jinak <application>MEncoder</application>
|
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|
zhavaruje. <option>pullup</option> je v<>ak nej<65>ist<73><74> a nejp<6A>esn<73>j<EFBFBD><6A> dostupnou
|
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|
metodou pro enk<6E>dov<6F>n<EFBFBD> jak telecinovan<61>ho, tak "sm<EFBFBD><EFBFBD>en<EFBFBD>ho progresivn<76>ho a
|
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telecinovan<61>ho".
|
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|
<screen>mencoder dvd://1 -nosound -vf pullup,softskip -ovc lavc -ofps 24000/1001</screen>
|
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|
</para>
|
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|
</listitem>
|
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|
<listitem><para>
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|
Star<61><72> metodou je, sp<73><70>e ne<6E> inverzn<7A> telecinovat telecinovan<61> <20><>sti,
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|
telecinovat progresivn<76> <20><>sti a pot<6F> inverzn<7A> telecinovat cel<65> video.
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|
Zmaten<65>? softpulldown je filtr, kter<65> projde cel<65> video a p<>evede cel<65> soubor
|
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|
na telecinovan<61>. Pokud budeme n<>sledovat softpulldown bu<62>
|
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|
<option>detc</option> nebo <option>ivtc</option>, bude kone<6E>n<EFBFBD> v<>sledek zcela
|
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|
progresivn<76>. Nutn<74> je volba <option>-ofps 24000/1001</option>.
|
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|
<screen>mencoder dvd://1 -nosound -vf softpulldown,ivtc=1 -ovc lavc -ofps 24000/1001</screen>
|
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|
|
</para>
|
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|
</listitem>
|
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|
<listitem><para>
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|
Osobn<62> jsem nepou<6F>il <option>-vf filmdint</option>, ale toto o n<>m (p<>ibli<6C>n<EFBFBD>)
|
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|
|
<20>ekl D Richard Felker III:
|
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|
<blockquote><para>Je to OK, ale IMO to zkou<6F><75> a<> p<><70>li<6C> <20>asto odstra<72>ovat
|
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|
proklad m<>sto prov<6F>d<EFBFBD>n<EFBFBD> inverzn<7A>ho telecine (stejn<6A> jako settop DVD
|
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|
p<>ehr<68>va<76>e & progresivn<76> televize) co<63> vede ke <20>kared<65>mu t<>epot<6F>n<EFBFBD> a
|
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|
dal<61><6C>m artefakt<6B>m. Pokud jej chcete pou<6F><75>vat, m<>li byste p<>edt<64>m alespo<70>
|
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|
trochu <20>asu v<>novat lad<61>n<EFBFBD> voleb a sledov<6F>n<EFBFBD>m v<>stupu, abyste m<>li jistotu,
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|
<20>e v<>m to n<>co nekaz<61>.</para></blockquote>
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|
</para></listitem>
|
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|
|
</itemizedlist>
|
|
|
|
|
</sect3>
|
|
|
|
|
|
|
|
|
|
<sect3 id="menc-feat-telecine-encode-mixedpi">
|
|
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|
|
<title>Sm<EFBFBD><EFBFBD>en<EFBFBD> progresivn<76> a prokl<6B>dan<61></title>
|
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|
|
<para>
|
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|
M<>me dv<64> volby pro pr<70>ci s touto kategori<72>, ob<6F> jsou v<>ak kompromisem. M<>li
|
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|
|
byste se rozhodnout podle trv<72>n<EFBFBD>/um<75>st<73>n<EFBFBD> ka<6B>d<EFBFBD>ho typu.
|
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|
</para>
|
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|
<itemizedlist>
|
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|
|
<listitem><para>
|
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|
Pova<76>ujte to za progresivn<76>. Prokl<6B>dan<61> <20><>sti budou vypadat prokl<6B>dan<61> a
|
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|
n<>kter<65> z prokl<6B>dan<61>ch pol<6F><6C>en bude muset b<>t zahozeno, co<63> povede
|
|
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|
|
k nestejnom<6F>rn<72>mu poskakov<6F>n<EFBFBD>. M<><4D>ete proti tomu nasadit postprocesn<73> filtr,
|
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|
|
pokud chcete, ale t<>m m<>rn<72> degradujete progresivn<76> <20><>sti.
|
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|
</para>
|
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|
<para>
|
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|
|
T<>to volb<6C> byste se m<>li rozhodn<64> vyhnout, pokud chcete nakonec zobrazovat
|
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|
|
video na zobrazova<76>i s prokl<6B>dan<61>m obrazem (p<>es TV kartu nap<61><70>klad).
|
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|
Pokud m<>te prokl<6B>dan<61> sn<73>mky ve videu s rychlost<73> 24000/1001 sn<73>mk<6D> za
|
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|
|
sekundu, budou telecinov<6F>ny spolu s progresivn<76>mi sn<73>mky. Polovina
|
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|
|
prokl<6B>dan<61>ch "sn<73>mk<6D>" bude zobrazena po dobu trv<72>n<EFBFBD> t<>ech sn<73>mk<6D>
|
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|
|
|
(3/(60000/1001) sekund), co<63> povede k poskakov<6F>n<EFBFBD>. Efekt
|
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|
|
"cuk<EFBFBD>n<EFBFBD> zp<7A>t" vypad<61> skute<74>n<EFBFBD> zle. Pokud se o to p<>ece pokus<75>te,
|
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|
<emphasis role="bold">mus<EFBFBD>te</emphasis> pou<6F><75>t filtr odstra<72>uj<75>c<EFBFBD> proklad,
|
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|
|
jako je <option>lb</option> nebo <option>l5</option>.
|
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|
|
</para>
|
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|
|
<para>
|
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|
<20>patnou volbou je to i pro progresivn<76> zobrazova<76>. Ten zahod<6F> p<>ry po sob<6F>
|
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|
|
jdouc<75>ch sn<73>mk<6D>, co<63> povede k p<>eru<72>ov<6F>n<EFBFBD>, kter<65> m<><6D>e b<>t v<>ce viditeln<6C>, ne<6E>
|
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|
p<>i druh<75> metod<6F>, kter<65> zobrazuje n<>kter<65> progresivn<76> sn<73>mky dvakr<6B>t.
|
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|
Prokl<6B>dan<61> video se 30000/1001 sn<73>mky za sekundu je toti<74> pon<6F>kud trhan<61>,
|
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|
|
proto<74>e by ve skute<74>nosti m<>lo b<>t prom<6F>t<EFBFBD>no p<>i 60000/1001 p<>lsn<73>mc<6D>ch za
|
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|
|
sekundu, tak<61>e zdvojen<65> n<>kter<65>ch sn<73>mk<6D> nen<65> tak moc vid<69>t.
|
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|
|
</para>
|
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|
|
<para>
|
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|
V ka<6B>d<EFBFBD>m p<><70>pad<61> je nejlep<65><70> posoudit obsah a zp<7A>sob, jak<61>m bude zobrazov<6F>n.
|
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|
Pokud je va<76>e video z 90% progresivn<76> a nikdy jej nebudete pou<6F>t<EFBFBD>t na
|
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|
|
televizi, m<>li byste volit progresivn<76> p<><70>stup.
|
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|
|
Pokud je progres<65>vn<76> jen z poloviny, pravd<76>podobn<62> jej bude lep<65><70> enk<6E>dovat
|
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|
|
jako ba bylo cel<65> prokl<6B>dan<61>.
|
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|
|
</para>
|
|
|
|
|
</listitem>
|
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|
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|
|
|
<listitem><para>
|
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|
|
Pokl<6B>dat jej za prokl<6B>dan<61>. N<>kter<65> sn<73>mky v progresivn<76>ch <20><>stech budou muset
|
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|
|
b<>t duplikov<6F>ny, co<63> povede k nepravideln<6C>mu poskakov<6F>n<EFBFBD>. Op<4F>t plat<61>, <20>e
|
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|
|
filtry pro odstran<61>n<EFBFBD> prokladu mohou pon<6F>kud degradovat progresivn<76> <20><>sti.
|
|
|
|
|
</para></listitem>
|
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|
|
|
|
|
|
|
|
</itemizedlist>
|
|
|
|
|
</sect3>
|
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|
|
|
|
|
|
|
</sect2>
|
|
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|
|
|
|
|
|
<sect2 id="menc-feat-telecine-footnotes">
|
|
|
|
|
<title>Pozn<EFBFBD>mky pod <20>arou</title>
|
|
|
|
|
<orderedlist>
|
|
|
|
|
<listitem><formalpara>
|
|
|
|
|
<title>K o<>ezu:</title>
|
|
|
|
|
<para>
|
|
|
|
|
Video data na DVD jsou ukl<6B>d<EFBFBD>na ve form<72>tu zvan<61>m YUV 4:2:0. V YUV videu jsou,
|
|
|
|
|
jasov<6F> ("<EFBFBD>ernob<EFBFBD>l<EFBFBD>"; angl. luma) a barvonosn<73> (angl. chroma) slo<6C>ka
|
|
|
|
|
ukl<6B>d<EFBFBD>ny odd<64>len<65>. Proto<74>e je lidsk<73> oko m<>n<EFBFBD> citliv<69> na zm<7A>nu barvy, ne<6E> na
|
|
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|
|
jas, p<>ipad<61> v YUV 4:2:0 obr<62>zku pouze jeden barvonosn<73> pixel na ka<6B>d<EFBFBD> <20>ty<74>i
|
|
|
|
|
jasov<6F> pixely. V progresivn<76>m obr<62>zku m<> ka<6B>d<EFBFBD> <20>tverec 2x2 jasov<6F>mi pixely
|
|
|
|
|
pr<70>v<EFBFBD> jeden barvonosn<73> pixel. Proto mus<75>te o<>ez<65>vat progresivn<76> YUV 4:2:0
|
|
|
|
|
na sud<75> rozm<7A>ry a pou<6F><75>vat sud<75> odsazen<65> (offsety). Nap<61><70>klad
|
|
|
|
|
<option>crop=716:380:2:26</option> je OK, ale
|
|
|
|
|
<option>crop=716:380:3:26 </option> nen<65>.
|
|
|
|
|
</para>
|
|
|
|
|
</formalpara>
|
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<para>
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Kdy<64> m<>te co do <20>in<69>n<EFBFBD> s prokl<6B>dan<61>m YUV 4:2:0, je situace mnohem
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komplikovan<61>j<EFBFBD><6A>. M<>sto ka<6B>d<EFBFBD>ch <20>ty<74>ech pixel<65> v <emphasis>r<EFBFBD>mu</emphasis>
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sd<73>lej<65>c<EFBFBD>ch barvonosn<73> pixel, ka<6B>d<EFBFBD> <20>ty<74>i jasov<6F> pixely v ka<6B>d<EFBFBD>m
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<emphasis>p<EFBFBD>lsn<EFBFBD>mku</emphasis> sd<73>lej<65> barvonosn<73> pixel. Kdy<64> jsou p<>lsn<73>mky
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prolo<6C>eny do sn<73>mku, ka<6B>d<EFBFBD> linka m<> v<><76>ku jeden pixel. A nyn<79> m<>sto aby dan<61>
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<20>ty<74>i pixely tvo<76>ily <20>tverec, jsou prvn<76> dva vedle sebe a druh<75> dva jsou vedle
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sebe o dv<64> linky n<><6E>. Dva pixely t<>sn<73> pod nimi pat<61><74> do jin<69>ho p<>lsn<73>mku a
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proto sd<73>l<EFBFBD> jin<69> barvonosn<73> pixel se dv<64>ma jasov<6F>mi pixely o dva <20><>dky n<><6E>.
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V<>echno tohle n<>s nut<75> m<>t svisl<73> rozm<7A>ry o<>ez<65>n<EFBFBD> a odsazen<65> bezezbytku
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d<>liteln<6C> <20>ty<74>mi. Vodorovn<76> sta<74><61> mohou z<>stat jen sud<75>.
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</para>
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<para>
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Pro telecinovan<61> video doporu<72>uji, abyste o<>ez<65>n<EFBFBD> prov<6F>d<EFBFBD>li a<> po inverzi
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telecine. Jakmile je video progresivn<76>, sta<74><61> <20>ezat jen na sud<75> rozm<7A>ry.
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Pokud si v<>ak p<>ece jen chcete dop<6F><70>t m<>rn<72> zrychlen<65>, kter<65> m<><6D>e poskytnout
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<20>asn<73> o<>ez, mus<75>te svisle dodr<64>et n<>sobky <20>ty<74>ech, jinak nebude m<>t filtr
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pro inverzi telecine spr<70>vn<76> data.
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</para>
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<para>
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Prokl<6B>dan<61> (nikoli telecinovan<61>) video mus<75>te v<>dy o<>ez<65>vat svisle n<>sobky
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<20>ty<74>, pokud p<>ed o<>ez<65>n<EFBFBD>m nepou<6F>ijete <option>-vf field</option>.
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</para>
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</listitem>
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<listitem><formalpara>
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<title>K volb<6C>m pro enk<6E>dov<6F>n<EFBFBD> a kvalit<69>:</title>
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<para>
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Jen proto, <20>e doporu<72>uji <option>mbd=2</option> zde neznamen<65>, <20>e by tato
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volba nemohla b<>t pou<6F>ita jinde. V kombinaci s <option>trell</option>, je
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<option>mbd=2</option> jednou ze dvou voleb
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<systemitem class="library">libavcodec</systemitem>u, kter<65> nejv<6A>ce zvy<76>uj<75>
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kvalitu a vy byste m<>li v<>dy pou<6F><75>t alespo<70> tyto dv<64>, pokud nen<65> na <20>kodu
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zpomalen<65> rychlosti enk<6E>dov<6F>n<EFBFBD> (nap<61>. p<>i enk<6E>dov<6F>n<EFBFBD> v re<72>ln<6C>m <20>ase).
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Mnoho dal<61><6C>ch voleb <systemitem class="library">libavcodec</systemitem>u
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zvy<76>uje kvalitu enk<6E>dov<6F>n<EFBFBD> (a sni<6E>uje jeho rychlost), ale to je mimo zam<61><6D>en<65>
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tohoto textu.
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</para>
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</formalpara>
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</listitem>
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<listitem><formalpara>
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<title>K v<>konu filtru pullup:</title>
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<para>
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Pou<6F>it<69> <option>pullup</option> je bezpe<70>n<EFBFBD> (spolu se <option>softskip
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</option>) ne progresivn<76> video a je to obvykle dobr<62> volba, pokud nebyl zdroj
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prov<6F><76>en, <20>e je cel<65> progresivn<76>. Ve v<>t<EFBFBD>in<69> p<><70>pad<61> je ztr<74>ta v<>konu mal<61>.
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V ojedin<69>l<EFBFBD>ch p<><70>padech enk<6E>dov<6F>n<EFBFBD> zp<7A>sob<6F> <option>pullup</option>, <20>e je
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<application>MEncoder</application> o 50% pomalej<65><6A>. P<>id<69>n<EFBFBD> zpracov<6F>n<EFBFBD> zvuku
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a pokro<72>il<69>ch <option>lavcopts</option> zast<73>n<EFBFBD> tento rozd<7A>l tak, <20>e rozd<7A>l
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v rychlosti p<>soben<65> pou<6F>it<69>m <option>pullup</option> se sn<73><6E><EFBFBD> na 2%.
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</para>
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</formalpara>
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</listitem>
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<!-- Some further explanation, because of homonym problem in interlace and
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interleave translation. If anybody wants it in english, just ask. -->
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<listitem><formalpara>
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<title>K p<>ekladu:</title>
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<para>
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P<>eklad slov interlace a interleave je velmi obt<62><74>n<EFBFBD>, proto<74>e vede k jedin<69>mu
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<20>esk<73>mu ekvivalentu – prokl<6B>d<EFBFBD>n<EFBFBD>. V prvn<76>m p<><70>pad<61> (interlace) se jedn<64>
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o prokl<6B>d<EFBFBD>n<EFBFBD> obr<62>zku, kdy se z lich<63>ch a sud<75>ch <20><>dk<64> vytvo<76><6F> dva p<>lsn<73>mky,
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co<63> je b<><62>n<EFBFBD> v TV.
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Prokl<6B>d<EFBFBD>n<EFBFBD> (interleave) je naproti tomu slou<6F>en<65> r<>zn<7A>ho obsahu (zvuk, video)
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do jedin<69>ho souboru – kontejneru (nap<61>. AVI) tak, <20>e se ka<6B>d<EFBFBD> slo<6C>ka
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rozd<7A>l<EFBFBD> na mal<61> <20><>sti (tzv. chunky) a ty se pak jeden za druh<75>m ukl<6B>daj<61> podle
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ur<75>it<69>ho vzoru. O to se star<61> muxer (multiplexer). Abychom dostali zp<7A>t
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jednotliv<69> slo<6C>ky, mus<75>me poskl<6B>dat proh<6F>zen<65> kousky zase zp<7A>t, o co<63> se star<61>
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demuxer (demultiplexor).
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</para>
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</formalpara>
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</listitem>
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</orderedlist>
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</sect2>
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</sect1>
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</chapter>
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