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278 lines
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<TITLE>Encoding - MEncoder - The Movie Encoder for Linux</TITLE>
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<H2><A NAME="encoding">2.4 Encoding with MEncoder</A></H2>
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<P>For the complete list of available MEncoder options and examples, please see
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the man page.</P>
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<H3><A NAME="2pass">2.4.1 Encoding 2 or 3-pass DivX4</A></H3>
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<P><U><B>2-pass encoding:</B></U> the name comes from the fact that this method
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encodes the file <I>twice</I>. The first encoding (dubbed <I>pass</I>)
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creates some temporary files (*.log) with a size of few megabytes, do not
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delete them yet (you can delete the AVI). In the second pass, the 2-pass
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output file is created, using the bitrate data from the temporary files. The
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resulting file will have much better image quality. If this is the first time
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you heard about this, you should consult some guides available on the
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Net.</P>
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<P>This example shows how to encode a DVD to a 2-pass DivX4 AVI. Just two
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commands are needed:<BR>
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<CODE> rm frameno.avi</CODE> - remove this file, which
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can come from a previous 3-pass encoding (it interferes with current
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one)<BR>
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<CODE> mencoder -dvd 2 -ovc lavc -lavcopts
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vcodec=mpeg4:vpass=1 -oac copy -o movie.avi<BR>
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mencoder -dvd 2 -ovc lavc -lavcopts
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vcodec=mpeg4:vpass=2 -oac copy -o movie.avi</CODE></P>
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<P><U><B>3-pass encoding:</B></U> this is an extension of 2-pass encoding,
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where the audio encoding takes place in a separate pass. This method enables
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estimation of recommended video bitrate in order to fit on a CD. Also, the
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audio is encoded only once, unlike in 2-pass mode. The schematics:</P>
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<OL>
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<LI>Remove conflicting temporary file:
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<P><CODE>rm frameno.avi</CODE></P></LI>
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<LI>First pass:
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<P><CODE>mencoder <file/DVD> -ovc frameno -oac mp3lame -lameopts vbr=3 -o frameno.avi</CODE></P>
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<P>An audio-only avi file will be created, containing
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<B>only</B> the requested audio stream. Don't forget <CODE>-lameopts</CODE>,
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if you need to set it. If you were encoding a long movie, MEncoder
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prints the recommended bitrate values for 650Mb, 700Mb, and 800Mb
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destination sizes, after this pass finishes.</P></LI>
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<LI>Second pass:
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<P><CODE>mencoder <file/DVD> -oac copy
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-ovc lavc -lavcopts vcodec=mpeg4:vpass=1:vbitrate=<bitrate></CODE></P>
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<P>Alias the first pass of DivX4 video encoding.
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Optionally specify the video bitrate MEncoder printed at the end of
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the previous pass.</P></LI>
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<LI>Third pass:
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<P><CODE>mencoder <file/DVD> -oac copy
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-ovc lavc -lavcopts vcodec=mpeg4:vpass=2:vbitrate=<bitrate></CODE></P>
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<P>Alias the second pass of DivX4 video encoding.
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Optionally specify the video bitrate MEncoder printed at the end of
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the previous pass. In this pass, audio from <CODE>frameno.avi</CODE> will
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be inserted into the destination file.. and it's all ready!</P></LI>
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</OL>
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<H4>Example for 3-pass encoding:</H4>
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<P><CODE> rm frameno.avi</CODE> - remove this file,
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which can come from a previous 3-pass encoding (it interferes with current
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one)<BR>
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<CODE> mencoder -dvd 2 -ovc frameno
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-o frameno.avi -oac mp3lame -lameopts vbr=3<BR>
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mencoder -dvd 2 -ovc lavc
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-lavcopts vcodec=mpeg4:vpass=1 -oac copy -o movie.avi<BR>
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mencoder -dvd 2 -ovc lavc
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-lavcopts vcodec=mpeg4:vpass=2 -oac copy -o movie.avi</CODE></P>
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<H3><A NAME="rescaling">2.4.2 Rescaling movies</A></H3>
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<P>Often the need to resize movie images' size emerges. Its reasons can be
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many: decreasing file size, network bandwidth, etc. Most people
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even do rescaling when converting DVDs or SVCDs to DivX AVI. <B>This is bad.</B>
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Instead of even you doing so, read the <A HREF="#aspect">Preserving
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aspect ratio</A> section.</P>
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<P>The scaling process is handled by the <I>'scale'</I> video filter:
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<CODE>-vop scale=widht:height</CODE>. Its quality can be set with the
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<CODE>-sws</CODE> option. If it's not specified, MEncoder will use 0:
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fast bilinear.</P>
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<H5>Usage:</H5>
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<P><CODE> mencoder input.mpg -ovc lavc -lavcopts
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vcodec=mpeg4 -vop scale=640:480 -oac copy -o
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output.avi</CODE></P>
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<H3><A NAME="copying">2.4.3 Stream copying</A></H3>
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<P>MEncoder can handle input streams in two ways: <B>encode</B> or
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<B>copy</B> them. This section is about <B>copying</B>.</P>
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<UL>
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<LI><B>Video stream</B> (option <CODE>-ovc copy</CODE>): nice stuff can be
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done :)<BR>
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Like, putting (not converting) FLI or VIVO or MPEG1 video into
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an AVI file. Of course only MPlayer can play such files :) And it
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probably has no real life value at all. Rationally: video stream copying
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can be useful for example when only the audio stream has to be encoded
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(like, uncompressed PCM to MP3).</LI>
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<LI><B>Audio stream</B> (option <CODE>-oac copy</CODE>): straightforward.
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It is possible to take an external audio file (MP3, Vorbis) and mux it
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into the output stream. Use the <CODE>-audiofile <filename></CODE>
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option for this.</LI>
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</UL>
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<H3><A NAME="fixing">2.4.4 Fixing AVIs with broken index or interleaving</A></H3>
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<P>Easiest thing. We simply copy the video and audio streams, and
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MEncoder generates the index. Of course this cannot fix possible bugs
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in the video and/or audio streams. It also fixes files with broken
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interleaving, thus the <CODE>-ni</CODE> option won't be needed for them
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anymore.</P>
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<P>Command: <CODE>mencoder -idx input.avi -ovc copy -oac copy -o output.avi</CODE></P>
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<H3><A NAME="libavcodec">2.4.5 Encoding with the libavcodec codec family</A></H3>
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<P><A HREF="codecs.html#libavcodec">libavcodec</A> provides simple encoding to a
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lot of interesting video and audio formats (currently its audio codecs are
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unsupported). You can encode to the following codecs:</P>
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<UL>
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<LI>mjpeg - Motion JPEG</LI>
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<LI>h263 - H263</LI>
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<LI>h263p - H263 Plus</LI>
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<LI>mpeg4 - DivX4</LI>
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<LI>msmpeg4 - the old DivX</LI>
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<LI>msmpeg4v2 - Micro$oft MPEG4 V2 (DivX alias MP43 predecessor)</LI>
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<LI>rv10 - an old RealVideo codec</LI>
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<LI>mpeg1video - MPEG1 video :)</LI>
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</UL>
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<P>The first column contains the codec names that should be passed after the
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<CODE>vcodec</CODE> config, like: <CODE>-lavcopts vcodec=msmpeg4</CODE></P>
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<P>An example, with MJPEG compression:<BR>
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<CODE> mencoder -dvd 2 -o title2.avi -ovc lavc
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-lavcopts vcodec=mjpeg -oac copy</CODE></P>
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<H3><A NAME="image_files">2.4.6 Encoding from multiple input image files (JPEGs, PNGs or TGAs)</A></H3>
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<P>MEncoder is capable of creating movies from one or more JPEG, PNG or TGA
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files. With simple framecopy it can create MJPEG (Motion JPEG), MPNG
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(Motion PNG) or MTGA (Motion TGA) files.</P>
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Explanation of the process:
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<OL>
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<LI>MEncoder <I>decodes</I> the input image(s) with
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<CODE>libjpeg</CODE> (when decoding PNGs, it will use <B>libpng</B>).</LI>
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<LI>MEncoder then feeds the decoded image to the chosen video compressor
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(DivX4, Xvid, ffmpeg msmpeg4, etc...). Watch for the PNG decoder, as
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currently it can output only to RGB formats, thus can't be used with codecs
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that require YUV as input, like DivX4 or ffmpeg's msmpeg4.</LI>
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</OL>
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<H4>Examples</H4>
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<P>The explanation of the <CODE>-mf</CODE> option can be found below in the
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global <A HREF="#options">Options</A> section and in the man page.</P>
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<P><I>Creating a DivX4 file from all the JPEG files in the current dir:</I><BR>
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<CODE>mencoder \*.jpg -mf on:w=800:h=600:fps=25 -ovc divx4
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-o output.avi</CODE></P>
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<P><I>Creating a DivX4 file from some JPEG files in the current dir:</I><BR>
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<CODE>mencoder frame001.jpg,frame002.jpg -mf on:w=800:h=600:fps=25
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-ovc divx4 -o output.avi</CODE></P>
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<P><I>Creating a Motion JPEG (MJPEG) file from all the JPEG files in the current dir:</I><BR>
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<CODE>mencoder \*.jpg -mf on:w=800:h=600:fps=25 -ovc copy
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-o output.avi</CODE></P>
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<P><I>Creating an uncompressed file from all the PNG files in the current dir:</I><BR>
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<CODE>mencoder \*.png -mf on:w=800:h=600:fps=25:type=png -ovc raw
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-o output.avi</CODE></P>
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<P><I>Creating a Motion PNG (MPNG) file from all the PNG files in the current dir:</I><BR>
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<CODE>mencoder \*.png -mf on:w=800:h=600:fps=25:type=png -ovc copy
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-o output.avi</CODE></P>
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<P><I>Creating a Motion TGA (MTGA) file from all the TGA files in the current dir:</I><BR>
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<CODE>mencoder \*.tga -mf on:w=800:h=600:fps=25:type=tga -ovc copy
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-o output.avi</CODE></P>
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<H3><A NAME="vobsub">2.4.7 Extracting DVD subtitles to a Vobsub file</A></H3>
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<P>MEncoder is capable of extracting subtitles from a DVD into
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Vobsub fomat files. They consist of a pair of files ending in
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<CODE>.idx</CODE> and <CODE>.sub</CODE> and are usually packaged in a single
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<CODE>.rar</CODE> archive. MPlayer can play these with the
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<CODE>-vobsub</CODE> and <CODE>-vobsubid</CODE> options.</P>
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<P>You specify the basename (i.e without the <CODE>.idx</CODE> or
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<CODE>.sub</CODE> extension) of the output files with <CODE>-vobsubout</CODE>
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and the index for this subtitle in the resulting files with
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<CODE>-vobsuboutindex</CODE>.</P>
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<P>If the input is not from a DVD you should use <CODE>-ifo</CODE> to
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indicate the <CODE>.ifo</CODE> file needed to construct the resulting
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<CODE>.idx</CODE> file.</P>
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<P>If the input is not from a DVD and you do not have the <CODE>.ifo</CODE>
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file you will need to use the <CODE>-vobsubid</CODE> option to let it know
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what language id to put in the <CODE>.idx</CODE> file.</P>
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<P>Each run will append the running subtitle if the <CODE>.idx</CODE> and
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<CODE>.sub</CODE> files already exist. So you should remove any before
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starting.</P>
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<H4>Examples</H4>
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<P><I>Copying two subtitles from a DVD while doing 3-pass encoding</I><BR>
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<CODE>rm subtitles.idx subtitles.sub</CODE><BR>
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<CODE>mencoder -dvd 1 -vobsubout subtitles -vobsuboutindex 0
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-sid 2 -o frameno.avi -ovc frameno -oac mp3lame -lameopts vbr=3</CODE><BR>
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<CODE>mencoder -dvd 1 -oac copy -ovc divx4 -divx4opts pass=1</CODE><BR>
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<CODE>mencoder -dvd 1 -oac copy -ovc divx4 -divx4opts pass=2 -vobsubout
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subtitles -vobsuboutindex 1 -sid 5</CODE></P>
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<P><I>Copying a french subtitle from an MPEG file</I><BR>
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<CODE>rm subtitles.idx subtitles.sub</CODE><BR>
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<CODE>mencoder movie.mpg -ifo movie.ifo -vobsubout subtitles
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-vobsuboutindex 0 -vobsuboutid fr -sid 1</CODE></P>
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<H3><A NAME="aspect">2.4.8 Preserving aspect ratio</A></H3>
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<P>DVDs and SVCDs (i.e. MPEG1/2) files contain an aspect ratio value,
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which describes how should the player scale the video stream, so humans
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won't have egg heads (ex.: 480x480 + 4:3 = 640x480). However when encoding
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to AVI (DivX) files, you have be aware that AVI headers don't store this
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value. Rescaling the movie is disgusting and time consuming, there
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must be a better feature!</P>
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<P>There is.</P>
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<P>MPEG4 has an unique feature: the video stream can contain
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its needed aspect ratio. Yes, just like MPEG1/2 files (DVD, SVCD).
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Regretfully, there are <U>no</U> video players outside which support this
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attribute. Except MPlayer.</P>
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<P>This feature can be used only with <B>libavcodec</B>'s <CODE>mpeg4</CODE>
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codec. Keep in mind: although MPlayer will correctly play the created file,
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other players will use the wrong aspect ratio.</P>
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<P>You seriously should crop the black bands over and below the movie image.
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See the manpage about the usage of the <CODE>cropdetect</CODE> and
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<CODE>crop</CODE> filters.</P>
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<H5>Usage:</H5>
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<P><CODE>$ mencoder sample-svcd.mpg -ovc lavc -lavcopts
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vcodec=mpeg4:aspect=16.0/9.0 -vop crop=714:548:0:14 -oac copy -o output.avi</CODE></P>
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