mpv/DOCS/xml/en/mencoder.xml

<?xml version="1.0" encoding="iso-8859-1"?>
<!-- $Revision$ -->
<chapter id="mencoder">
<title>Encoding with <application>MEncoder</application></title>

<para>
For the complete list of available <application>MEncoder</application> options
and examples, please see the man page. For a series of hands-on examples and
detailed guides on using several encoding parameters, read the
<ulink url="../../tech/encoding-tips.txt">encoding-tips</ulink> that were
collected from several mailing list threads on MPlayer-users. Search the
<ulink url="http://mplayerhq.hu/pipermail/mplayer-users/">archives</ulink>
for a wealth of discussions about all aspects of and problems related to
encoding with <application>MEncoder</application>.
</para>

<sect1 id="menc-feat-mpeg4">
<title>Encoding two pass MPEG-4 (&quot;DivX&quot;)</title>

<para>
The name comes from the fact that this method encodes the file <emphasis>twice</emphasis>.
The first encoding (dubbed pass) creates some temporary files
(<filename>*.log</filename>) with a size of few megabytes, do not delete
them yet (you can delete the AVI). In the second pass, the two pass output
file is created, using the bitrate data from the temporary files. The
resulting file will have much better image quality. If this is the first
time you heard about this, you should consult some guides available on the
net.
</para>

<example>
<title>copy audio track</title>
<para>
Two pass encode of a DVD to an MPEG-4 (&quot;DivX&quot;) AVI while copying
the audio track.
<screen>
mencoder dvd://2 -ovc lavc -lavcopts vcodec=mpeg4:vpass=1 -oac copy -o <replaceable>movie.avi</replaceable>
mencoder dvd://2 -ovc lavc -lavcopts vcodec=mpeg4:vpass=2 -oac copy -o <replaceable>movie.avi</replaceable>
</screen>
</para>
</example>

<example>
<title>encode audio track</title>
<para>
Two pass encode of a DVD to an MPEG-4 (&quot;DivX&quot;) AVI while encoding
the audio track to MP3.
<screen>
mencoder dvd://2 -ovc lavc -lavcopts vcodec=mpeg4:vpass=1 -oac mp3lame -lameopts vbr=3 -o <replaceable>movie.avi</replaceable>
mencoder dvd://2 -ovc lavc -lavcopts vcodec=mpeg4:vpass=2 -oac mp3lame -lameopts vbr=3 -o <replaceable>movie.avi</replaceable>
</screen>
</para>
</example>
</sect1>

<sect1 id="menc-feat-mpeg">
<title>Encoding to MPEG format</title>
<para>
<application>MEncoder</application> can create MPEG (MPEG-PS) format output
files. It's probably useful only with
<link linkend="ffmpeg"><systemitem class="library">libavcodec</systemitem></link>'s
<emphasis>mpeg1video</emphasis> codec, because players - except
<application>MPlayer</application> - expect MPEG-1 video, and MPEG-1 layer 2 (MP2)
audio streams in MPEG files.
</para>

<para>
This feature is not very useful right now, aside that it probably has many bugs,
but the more importantly because <application>MEncoder</application> currently
cannot encode MPEG-1 layer 2 (MP2) audio, which all other players expect in MPEG files.
</para>

<para>
To change <application>MEncoder</application>'s output file format,
use the <option>-of mpeg</option> option.
</para>

<para>
Example:
<screen>
mencoder -of mpeg -ovc lavc -lavcopts vcodec=mpeg1video -oac copy <replaceable>other_options</replaceable> <replaceable>media.avi</replaceable> -o <replaceable>output.mpg</replaceable>
</screen>
</para>
</sect1>


<sect1 id="menc-feat-rescale">
<title>Rescaling movies</title>

<para>
Often the need to resize movie images' size emerges. Its reasons can be
many: decreasing file size, network bandwidth,etc. Most people even do
rescaling when converting DVDs or SVCDs to DivX AVI. If you wish to rescale,
read the <link linkend="aspect">Preserving aspect ratio</link> section.
</para>

<para>
The scaling process is handled by the <literal>scale</literal> video filter:
<option>-vf scale=<replaceable>width</replaceable>:<replaceable>height</replaceable></option>.
Its quality can be set with the <option>-sws</option> option.
If it's not specified, <application>MEncoder</application> will use 2: bicubic.
</para>

<para>
Usage:
<screen>
mencoder <replaceable>input.mpg</replaceable> -ovc lavc -lavcopts vcodec=mpeg4 -vf scale=640:480 -o <replaceable>output.avi</replaceable>
</screen>
</para>
</sect1>


<sect1 id="menc-feat-streamcopy">
<title>Stream copying</title>

<para>
<application>MEncoder</application> can handle input streams in two ways:
<emphasis role="bold">encode</emphasis> or <emphasis role="bold">copy</emphasis>
them. This section is about <emphasis role="bold">copying</emphasis>.
</para>

<itemizedlist>
<listitem><para>
  <emphasis role="bold">Video stream</emphasis> (option <option>-ovc copy</option>):
  nice stuff can be done :) Like, putting (not converting!) FLI or VIVO or
  MPEG-1 video into an AVI file! Of course only
  <application>MPlayer</application> can play such files :) And it probably
  has no real life value at all. Rationally: video stream copying can be
  useful for example when only the audio stream has to be encoded (like,
  uncompressed PCM to MP3).
  </para></listitem>
<listitem><para>
  <emphasis role="bold">Audio stream</emphasis> (option <option>-oac copy</option>):
  straightforward. It is possible to take an external audio file (MP3,
  WAV) and mux it into the output stream. Use the
  <option>-audiofile <replaceable>filename</replaceable></option> option
  for this.
  </para></listitem>
</itemizedlist>
</sect1>


<sect1 id="menc-feat-enc-libavcodec">
<title>Encoding with the <systemitem class="library">libavcodec</systemitem>
  codec family</title>

<para>
<link linkend="ffmpeg"><systemitem class="library">libavcodec</systemitem></link>
provides simple encoding to a lot of interesting video and audio formats.
You can encode to the following codecs (more or less up to date):

<informaltable frame="all">
<tgroup cols="2">
<thead>
<row><entry>Codec name</entry><entry>Description</entry></row>
</thead>
<tbody>
<row><entry>mjpeg</entry><entry>
   Motion JPEG
  </entry></row>
<row><entry>ljpeg</entry><entry>
   Lossless JPEG
  </entry></row>
<row><entry>h263</entry><entry>
  H.263
  </entry></row>
<row><entry>h263p</entry><entry>
  H.263+
  </entry></row>
<row><entry>mpeg4</entry><entry>
  ISO standard MPEG-4 (DivX 5, XVID compatible)
  </entry></row>
<row><entry>msmpeg4</entry><entry>
  pre-standard MPEG-4 variant by MS, v3 (AKA DivX3)
  </entry></row>
<row><entry>msmpeg4v2</entry><entry>
  pre-standard MPEG-4 by MS, v2 (used in old asf files)
  </entry></row>
<row><entry>wmv1</entry><entry>
  Windows Media Video, version 1 (AKA WMV7)
  </entry></row>
<row><entry>wmv2</entry><entry>
  Windows Media Video, version 2 (AKA WMV8)
  </entry></row>
<row><entry>rv10</entry><entry>
  an old RealVideo codec
  </entry></row>
<row><entry>mpeg1video</entry><entry>
  MPEG-1 video
  </entry></row>
<row><entry>mpeg2video</entry><entry>
  MPEG-2 video
  </entry></row>
<row><entry>huffyuv</entry><entry>
  lossless compression
  </entry></row>
<row><entry>asv1</entry><entry>
  ASUS Video v1
  </entry></row>
<row><entry>asv2</entry><entry>
  ASUS Video v2
  </entry></row>
<row><entry>ffv1</entry><entry>
  FFmpeg's lossless video codec
  </entry></row>
</tbody>
</tgroup>
</informaltable>

The first column contains the codec names that should be passed after the
<literal>vcodec</literal> config, like: <option>-lavcopts vcodec=msmpeg4</option>
</para>

<informalexample>
<para>
An example, with MJPEG compression:
<screen>mencoder dvd://2 -o title2.avi -ovc lavc -lavcopts vcodec=mjpeg -oac copy</screen>
</para>
</informalexample>
</sect1>


<sect1 id="menc-feat-enc-images">
<title>Encoding from multiple input image files (JPEG, PNG, TGA, SGI)</title>

<para>
<application>MEncoder</application> is capable of creating movies from one
or more JPEG, PNG or TGA files. With simple framecopy it can create MJPEG
(Motion JPEG), MPNG (Motion PNG) or MTGA (Motion TGA) files.
</para>

<orderedlist>
<title>Explanation of the process:</title>
<listitem><para>
  <application>MEncoder</application> <emphasis>decodes</emphasis> the input image(s) with
  <systemitem class="library">libjpeg</systemitem> (when decoding PNGs, it
  will use <systemitem class="library">libpng</systemitem>).
  </para></listitem>
<listitem><para>
  <application>MEncoder</application> then feeds the decoded image to the
  chosen video compressor (DivX4, XviD, FFmpeg msmpeg4, etc.).
  </para></listitem>
</orderedlist>

<formalpara>
<title>Examples</title>
<para>
The explanation of the <option>-mf</option> option is in the man page.

<informalexample>
<para>
Creating an MPEG-4 file from all the JPEG files in the current directory:
<screen>
mencoder mf://*.jpg -mf w=800:h=600:fps=25:type=jpg -ovc lavc -lavcopts vcodec=mpeg4 -oac copy -o <replaceable>output.avi</replaceable>
</screen>
</para>
</informalexample>

<informalexample>
<para>
Creating an MPEG-4 file from some JPEG files in the current directory:
<screen>
mencoder mf://<replaceable>frame001.jpg,frame002.jpg</replaceable> -mf w=800:h=600:fps=25:type=jpg -ovc lavc -lavcopts vcodec=mpeg4 -oac copy -o <replaceable>output.avi</replaceable>
</screen>
</para>
</informalexample>

<informalexample>
<para>
Creating a Motion JPEG (MJPEG) file from all the JPEG files in the current
directory:
<screen>
mencoder mf://*.jpg -mf w=800:h=600:fps=25:type=jpg -ovc copy -oac copy -o <replaceable>output.avi</replaceable>
</screen>
</para>
</informalexample>

<informalexample>
<para>
Creating an uncompressed file from all the PNG files in the current directory:
<screen>
mencoder mf:// -mf w=800:h=600:fps=25:type=png -ovc raw -oac copy -o <replaceable>output.avi</replaceable>
</screen>
</para>
</informalexample>

<note><para>
Width must be integer multiple of 4, it's a limitation of the RAW RGB AVI format.
</para></note>

<informalexample>
<para>
Creating a Motion PNG (MPNG) file from all the PNG files in the current
directory:
<screen>
mencoder mf://*.png -mf w=800:h=600:fps=25:type=png -ovc copy -oac copy -o <replaceable>output.avi</replaceable> <!--
--></screen>
</para>
</informalexample>

<informalexample>
<para>
Creating a Motion TGA (MTGA) file from all the TGA files in the current
directory:
<screen>
mencoder mf://*.tga -mf w=800:h=600:fps=25:type=tga -ovc copy -oac copy -o <replaceable>output.avi</replaceable><!--
--></screen>
</para>
</informalexample>

</para>
</formalpara>
</sect1>


<sect1 id="menc-feat-extractsub">
<title>Extracting DVD subtitles to VOBsub file</title>

<para>
<application>MEncoder</application> is capable of extracting subtitles from
a DVD into VOBsub formatted files. They consist of a pair of files ending in
<filename>.idx</filename> and <filename>.sub</filename> and are usually
packaged in a single <filename>.rar</filename> archive.
<application>MPlayer</application> can play these with the
<option>-vobsub</option> and <option>-vobsubid</option> options.
</para>

<para>
You specify the basename (i.e without the <filename>.idx</filename> or
<filename>.sub</filename> extension) of the output files with
<option>-vobsubout</option> and the index for this subtitle in the
resulting files with <option>-vobsuboutindex</option>.
</para>

<para>
If the input is not from a DVD you should use <option>-ifo</option> to
indicate the <filename>.ifo</filename> file needed to construct the
resulting <filename>.idx</filename> file.
</para>

<para>
If the input is not from a DVD and you do not have the
<filename>.ifo</filename> file you will need to use the
<option>-vobsubid</option> option to let it know what language id to put in
the <filename>.idx</filename> file.
</para>

<para>
Each run will append the running subtitle if the <filename>.idx</filename>
and <filename>.sub</filename> files already exist. So you should remove any
before starting.
</para>

<example>
<title>Copying two subtitles from a DVD while doing two pass encoding</title>
<screen>
rm subtitles.idx subtitles.sub
mencoder dvd://1 -oac copy -ovc lavc -lavcopts vcodec=mpeg4:vpass=1 -vobsubout subtitles -vobsuboutindex 0 -sid 2
mencoder dvd://1 -oac copy -ovc lavc -lavcopts vcodec=mpeg4:vpass=2 -vobsubout subtitles -vobsuboutindex 1 -sid 5<!--
--></screen>
</example>

<example>
<title>Copying a french subtitle from an MPEG file</title>
<screen>
rm subtitles.idx subtitles.sub
mencoder <replaceable>movie.mpg</replaceable> -ifo <replaceable>movie.ifo</replaceable> -vobsubout subtitles -vobsuboutindex 0 -vobsuboutid fr -sid 1<!--
--></screen>
</example>

</sect1>

<sect1 id="aspect">
<title>Preserving aspect ratio</title>
<para>
DVDs and SVCDs (i.e. MPEG-1/2) files contain an aspect ratio value, which
describes how the player should scale the video stream, so humans won't
have egg heads (ex.: 480x480 + 4:3 = 640x480). However when encoding to AVI
(DivX) files, you have be aware that AVI headers don't store this value.
Rescaling the movie is disgusting and time consuming, there has to be a better
way!
</para>

<para>There is</para>

<para>
MPEG-4 has an unique feature: the video stream can contain its needed aspect
ratio. Yes, just like MPEG-1/2 (DVD, SVCD) and H.263 files. Regretfully, there are
<emphasis role="bold">no</emphasis> video players outside which support this
attribute of MPEG-4, except <application>MPlayer</application>.
</para>

<para>
This feature can be used only with
<link linkend="ffmpeg"><systemitem class="library">libavcodec</systemitem></link>'s
<systemitem>mpeg4</systemitem> codec. Keep in mind: although
<application>MPlayer</application> will correctly play the created file,
other players will use the wrong aspect ratio.
</para>

<para>
You seriously should crop the black bands over and below the movie image.
See the man page for the usage of the <systemitem>cropdetect</systemitem> and
<systemitem>crop</systemitem> filters.
</para>

<para>
Usage
<screen>mencoder <replaceable>sample-svcd.mpg</replaceable> -ovc lavc -lavcopts vcodec=mpeg4:autoaspect -vf crop=714:548:0:14 -oac copy -o <replaceable>output.avi</replaceable></screen>
</para>
</sect1>

<sect1 id="custommatrices"><title>Custom inter/intra matrices</title>

<para>
With this feature of
<link linkend="ffmpeg"><systemitem class="library">libavcodec</systemitem></link>
you are able to set custom inter (I-frames/keyframes) and intra
(P-frames/predicted frames) matrices. It is supported by many of the codecs:
<systemitem>mpeg1video</systemitem> and <systemitem>mpeg2video</systemitem>
are reported as working.
</para>

<para>
A typical usage of this feature is to set the matrices preferred by the
<ulink url="http://www.kvcd.net/">KVCD</ulink> specifications.
</para>

<para>
The <emphasis role="bold">KVCD &quot;Notch&quot; Quantization Matrix:</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>
Usage:
<screen>
$ mencoder <replaceable>input.avi</replaceable> -o <replaceable>output.avi</replaceable> -oac copy -ovc lavc -lavcopts inter_matrix=...:intra_matrix=...
</screen>
</para>

<para>
<screen>
$ mencoder <replaceable>input.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>Making a high quality MPEG-4 (&quot;DivX&quot;) rip of a DVD movie</title>

<para>
  One frequently asked question is "How do I make the highest quality rip for
  a given size?". Another question is "How do I make the highest quality DVD
  rip possible? I don't care about file size, I just want the best quality."
</para>

<para>
  The latter question is perhaps at least somewhat wrongly posed. After all, if
  you don't care about file size, why not simply copy the entire MPEG-2 video
  stream from the the DVD? Sure, your AVI will end up being 5GB, give
  or take, but if you want the best quality and don't care about size,
  this is certainly your best option.
</para>

<para>
  In fact, the reason you want to transcode a DVD into MPEG-4 is
  specifically because you <emphasis role="bold">do</emphasis> care about
  file size.
</para>

<para>
  It's difficult to offer a cookbook recipe on how to create a very high
  quality DVD rip. There are several factors to consider, and you should
  understand these details or else you're likely to end up disappointed
  with your results. Below we'll investigate some of these issues, and
  then have a look at an example. We assume you're using
  <systemitem class="library">libavcodec</systemitem> to encode the video,
  although the theory applies to other codecs as well.
</para>

<para>
  If this seems to be too much for you, you should probably use one of the
  many fine frontends that are listed in the
  <ulink url="http://mplayerhq.hu/homepage/design7/projects.html#mencoder_frontends">MEncoder section</ulink>
  of our related projects page.
  That way, you should be able to achieve high quality rips without too much
  thinking, because most of those tools are designed to take clever decisions
  for you.
</para>

<sect2 id="menc-feat-dvd-mpeg4-2pass">
<title>Constant Quantizer vs. two pass</title>

<para>
  There are three approaches to encoding the video: constant bitrate
  (CBR), constant quantizer, and two pass (ABR, or average bitrate).
</para>

<para>
  In each of these modes, <systemitem class="library">libavcodec</systemitem>
  breaks the video frame into 16x16 pixel macroblocks and then applies a
  quantizer to each macroblock. The lower the quantizer, the better the
  quality and higher the bitrate. The method
  <systemitem class="library">libavcodec</systemitem> uses to determine
  which quantizer to use for a given macroblock varies and is highly
  tunable. (This is an extreme over-simplification of the actual
  process, but the basic concept is useful to understand.)
</para>

<para>
  When you specify a constant bitrate, <systemitem
  class="library">libavcodec</systemitem> will encode the video, discarding
  detail as much as necessary and as little as possible in order to remain
  lower than the given bitrate. If you truly don't care about file size,
  you could as well use CBR and specify a bitrate of infinity. (In
  practice, this means a value high enough so that it poses no limit, like
  10000Kbit.) With no real restriction on bitrate, the result is that
  <systemitem class="library">libavcodec</systemitem> will use the lowest
  possible quantizer for each macroblock (as specified by
  <option>vqmin</option>, which is 2 by default). As soon as you specify a
  low enough bitrate that <systemitem class="library">libavcodec</systemitem>
  is forced to use a higher quantizer, then you're almost certainly ruining
  the quality of your video.
  In order to avoid that, you should probably downscale your video, according
  to the method described later on in this guide.
  In general, you should avoid CBR altogether if you care about quality.
</para>

<para>
  With constant quantizer, <systemitem
  class="library">libavcodec</systemitem> uses the same quantizer, as
  specified by the <option>vqscale</option> option, on every macroblock. If
  you want the highest quality rip possible, again ignoring bitrate, you can
  use <option>vqscale=2</option>. This will yield the same bitrate and PSNR
  (peak signal-to-noise ratio) as CBR with
  <option>vbitrate</option>=infinity and the default <option>vqmin</option>
  of 2.
</para>

<para>
  The problem with constant quantizing is that it uses the given quantizer
  whether the macroblock needs it or not. That is, it might be possible
  to use a higher quantizer on a macroblock without sacrificing visual
  quality. Why waste the bits on an unnecessarily low quantizer? Your
  CPU has as many cycles as there is time, but there's only so many bits
  on your hard disk.
</para>

<para>
  With a two pass encode, the first pass will rip the movie as though it
  were CBR, but it will keep a log of properties for each frame. This
  data is then used during the second pass in order to make intelligent
  decisions about which quantizers to use. During fast action or low
  detail scenes, higher quantizers will likely be used, and during
  slow moving or high detail scenes, lower quantizers will be used.
</para>

<para>
  If you use <option>vqscale=2</option>, then you're wasting bits. If you
  use <option>vqscale=3</option>, then you're not getting the highest
  quality rip. Suppose you rip a DVD at <option>vqscale=3</option>, and
  the result is 1800Kbit. If you do a two pass encode with
  <option>vbitrate=1800</option>, the resulting video will have <emphasis
  role="bold">higher quality</emphasis> for the
  <emphasis role="bold">same bitrate</emphasis>.
</para>

<para>
  Since you're now convinced that two pass is the way to go, the real
  question now is what bitrate to use? The answer is that there's no
  single answer. Ideally you want to choose a bitrate that yields the
  best balance between quality and file size. This is going to vary
  depending on the source video.
</para>

<para>
  If size doesn't matter, a good starting point for a very high quality
  rip is about 2000Kbit plus or minus 200Kbit.
  For fast action or high detail source video, or if you just have a very
  critical eye, you might decide on 2400 or 2600.
  For some DVDs, you might not notice a difference at 1400Kbit. It's a
  good idea to experiment with scenes at different bitrates to get a feel.
</para>

<para>
  If you aim at a certain size, you will have to somehow calculate the bitrate.
  But before that, you need to know how much space you should reserve for the
  audio track(s), so you should <link linkend="menc-feat-dvd-mpeg4-audio">rip
  those</link> first.
  You can compute the bitrate with the following equation:
  <systemitem>bitrate = (target_size_in_Mbytes - sound_size_in_Mbytes) *
  1024 * 1024 / length_in_secs * 8 / 1000</systemitem>
  For instance, to squeeze a two-hour movie onto a 702MB CD, with 60MB
  of audio track, the video bitrate will have to be:
  <systemitem>(702 - 60) * 1024 * 1024 / (120*60) * 8 / 1000
  = 740kbps</systemitem>
</para>

</sect2>


<sect2 id="menc-feat-dvd-mpeg4-constraints">
<title>Constraints for efficient encoding</title>

<para>
  Due to the nature of MPEG-type compression, there are various
  constraints you should follow for maximal quality.
  MPEG splits the video up into 16x16 squares called macroblocks,
  each composed of 4 8x8 blocks of luma (intensity) information and two
  half-resolution 8x8 chroma (color) blocks (one for red-cyan axis and
  the other for the blue-yellow axis).
  Even if your movie width and height are not multiples of 16, the
  encoder will use enough 16x16 macroblocks to cover the whole picture
  area, and the extra space will go to waste.
  So in the interests of maximizing quality at a fixed filesize, it is
  a bad idea to use dimensions that are not multiples of 16.
</para>

<para>
  Most DVDs also have some degree of black borders at the edges. Leaving
  these in place can hurt quality in several ways.
</para>

<orderedlist>
<listitem>
<para>
  MPEG-type compression is also highly dependent on frequency domain
  transformations, in particular the Discrete Cosine Transform (DCT),
  which is similar to the Fourier transform. This sort of encoding is
  efficient for representing patterns and smooth transitions, but it
  has a hard time with sharp edges. In order to encode them it must
  use many more bits, or else an artifact known as ringing will
  appear.
</para>

<para>
  The frequency transform (DCT) takes place separately on each
  macroblock (actually each block), so this problem only applies when
  the sharp edge is inside a block. If your black borders begin
  exactly at multiple-of-16 pixel boundaries, this is not a problem.
  However, the black borders on DVDs rarely come nicely aligned, so
  in practice you will always need to crop to avoid this penalty.
</para>
</listitem>
</orderedlist>

<para>
  In addition to frequency domain transforms, MPEG-type compression uses
  motion vectors to represent the change from one frame to the next.
  Motion vectors naturally work much less efficiently for new content
  coming in from the edges of the picture, because it is not present in
  the previous frame. As long as the picture extends all the way to the
  edge of the encoded region, motion vectors have no problem with
  content moving out the edges of the picture. However, in the presence
  of black borders, there can be trouble:
</para>

<orderedlist continuation="continues">
<listitem>
<para>
  For each macroblock, MPEG-type compression stores a vector
  identifying which part of the previous frame should be copied into
  this macroblock as a base for predicting the next frame. Only the
  remaining differences need to be encoded. If a macroblock spans the
  edge of the picture and contains part of the black border, then
  motion vectors from other parts of the picture will overwrite the
  black border. This means that lots of bits must be spent either
  re-blackening the border that was overwritten, or (more likely) a
  motion vector won't be used at all and all the changes in this
  macroblock will have to be coded explicitly. Either way, encoding
  efficiency is greatly reduced.
</para>

<para>
  Again, this problem only applies if black borders do not line up on
  multiple-of-16 boundaries.
</para>
</listitem>

<listitem>
<para>
  Finally, suppose we have a macroblock in the interior of the
  picture, and an object is moving into this block from near the edge
  of the image. MPEG-type coding can't say "copy the part that's
  inside the picture but not the black border." So the black border
  will get copied inside too, and lots of bits will have to be spent
  encoding the part of the picture that's supposed to be there.
</para>

<para>
  If the picture runs all the way to the edge of the encoded area,
  MPEG has special optimizations to repeatedly copy the pixels at the
  edge of the picture when a motion vector comes from outside the
  encoded area. This feature becomes useless when the movie has black
  borders. Unlike problems 1 and 2, aligning the borders at multiples
  of 16 does not help here.
</para>
</listitem>

<listitem>
<para>
  Depite the borders being entirely black and never changing, there
  is at least a minimal amount of overhead involved in having more
  macroblocks.
</para>
</listitem>
</orderedlist>

<para>
  For all of these reasons, it's recommended to fully crop black
  borders. Further, if there is an area of noise/distortion at the edge
  of the picture, cropping this will improve encoding efficiency as
  well. Videophile purists who want to preserve the original as close as
  possible may object to this cropping, but unless you plan to encode at
  constant quantizer, the quality you gain from cropping will
  considerably exceed the amount of information lost at the edges.
</para>
</sect2>


<sect2 id="menc-feat-dvd-mpeg4-crop">
<title>Cropping and Scaling</title>

<para>
  Native DVD resolution is 720x480 for NTSC, and 720x576 for PAL, but
  there's an aspect flag that specifies whether it's full-screen (4:3) or
  wide-screen (16:9). Many (if not most) widescreen DVDs are not strictly
  16:9, and will be either 1.85:1 or 2.35:1 (cinescope). This means that
  there will be black bands in the video that will need to be cropped out.
</para>

<para>
  <application>MPlayer</application> provides a crop detection filter that
  will determine the crop rectangle (<option>-vf cropdetect</option>).
  Because MPEG-4 uses 16x16 macroblocks, you'll want to make sure that each
  dimension of the video you're encoding is a multiple of 16 or else you
  will be degrading quality, especially at lower bitrates. You can do this
  by rounding the width and height of the crop rectangle down to the nearest
  multiple of 16. When cropping, you'll want to increase the y-offset by
  half the difference of the old and the new height so that the resulting
  video is taken from the center of the frame. And because of the way DVD
  video is sampled, make sure the offset is an even number. (In fact, as a
  rule, never use odd values for any parameter when you're cropping and
  scaling video.) If you're not comfortable throwing a few extra pixels
  away, you might prefer instead to scale the video instead. We'll look
  at this in our example below.
  You can actually let the <option>cropdetect</option> filter do all of the
  above for you, as it has an optional <option>round</option> parameter that
  is equal to 16 by default.
</para>

<para>
  Also, be careful about "half black" pixels at the edges. Make sure you
  crop these out too, or else you'll be wasting bits there that
  are better spent elsewhere.
</para>

<para>
  After all is said and done, you'll probably end up with video whose pixels
  aren't quite 1.85:1 or 2.35:1, but rather something close to that. You
  could calculate the new aspect ratio manually, but
  <application>MEncoder</application> offers an option for <systemitem
  class="library">libavcodec</systemitem> called <option>autoaspect</option>
  that will do this for you. Absolutely do not scale this video up in order to
  square the pixels unless you like to waste your hard disk space. Scaling
  should be done on playback, and the player will use the aspect stored in
  the AVI to determine the correct resolution.
  Unfortunately, not all players enforce this auto-scaling information,
  therefore you may still want to rescale.
</para>

<para>
  First, you should compute the encoded aspect ratio:
  <systemitem>ARc = (Wc x (ARa / PRdvd )) / Hc</systemitem>
<itemizedlist>
<title>where:</title>
<listitem><para>
  Wc and Hc are the width and height of the cropped video,
</para></listitem>
<listitem><para>
  PRdvd is the pixel ratio of the DVD wich is equal to 1.25=(720/576) for PAL,
</para></listitem>
<listitem><para>
  DVDs and 1.5=(720/480) for NTSC DVDs,
</para></listitem>
</itemizedlist>
</para>

<para>
  Then, you can compute the X and Y resolution, according to a certain
  Compression Quality (CQ) factor:
  <systemitem>ResY = INT(SQRT( 1000*Bitrate/25/ARc/CQ )/16) * 16</systemitem>
  <systemitem>ResX = INT( ResY * ARc / 16) * 16</systemitem>
</para>

<para>
  Okay, but what is the CQ?
  The CQ represents the number of bits per pixel and per frame of the encode.
  Roughly speaking, the greater the CQ, the less the likelihood to see
  encoding artifacts.
  However, if you have a target size for your movie (1 or 2 CDs for instance),
  there's a limited total number of bits that you can spend; therefore it's
  necessary to find a good tradeoff between compressibility and quality.
</para>

<para>
  The CQ depends both on the bitrate and the movie resolution.
  In order to raise the CQ, typically you'd downscale the movie given that the
  bitrate is computed in function of the target size and the length of the
  movie, which are constant.
  A CQ below 0.18 usually ends up in a very blocky picture, because there
  aren't enough bits to code the information of each macroblock (MPEG4, like
  many other codecs, groups pixels by blocks of several pixels to compress the
  image; if there aren't enough bits, the edges of those blocks are
  visible).
  It's therefore wise to take a CQ ranging from 0.20 to 0.22 for a 1 CD rip,
  and  0.26-0.28 for 2 CDs.
</para>

<para>
  Please take note that the CQ is just an indicative figure, as depending on
  the encoded content, a CQ of 0.18 may look just fine for a Bergman, contrary
  to a movie such as The Matrix, which contains many high-motion scenes.
  On the other hand, it's worthless to raise CQ higher than 0.30 as you'd
  be wasting bits without any noticeable quality gain.
</para>

</sect2>

<sect2 id="menc-feat-dvd-mpeg4-audio">
<title>Audio</title>

<para>
  Audio is a much simpler problem to solve: if you care about quality, just
  leave it as is.
  Even AC3 5.1 streams are at most 448Kbit/s, and they're worth every bit.
  You might be tempted to transcode the audio to high quality Vorbis, but
  just because you don't have an A/V receiver for AC3 pass-through today
  doesn't mean you won't have one tomorrow. Future-proof your DVD rips by
  preserving the AC3 stream.
  You can keep the AC3 stream either by copying it directly into the video
  stream <link linkend="menc-feat-mpeg4">during the encoding</link>.
  You can also extract the AC3 stream in order to mux it into containers such
  as NUT or Matroska.
  <screen>mplayer <replaceable>source_file.vob</replaceable> -aid 129 -dumpaudio -dumpfile <replaceable>sound.ac3</replaceable></screen>
  will dump into the file <replaceable>sound.ac3</replaceable> the
  audio track number 129 from the file
  <replaceable>source_file.vob</replaceable> (NB: DVD VOB files
  usually use a different audio numbering,
  which means that the VOB audio track 129 is the 2nd audio track of the file).
</para>

<para>
  But sometimes you truly have no choice but to further compress the
  sound so that more bits can be spent on the video.
  Most people choose to compress audio with either MP3 or Vorbis audio
  codecs.
  While the latter is a very space-efficient codec, MP3 is better supported
  by hardware players, although this trend is changing.
</para>

<para>
  First of all, you will have to convert the DVD sound into a WAV file that the
  audio codec can use as input.
  For example:
  <screen>mplayer <replaceable>source_file.vob</replaceable> -ao pcm:file=<replaceable>destination_sound.wav</replaceable> -vc dummy -aid 1 -vo null</screen>
  will dump the second audio track from the file
  <replaceable>source_file.vob</replaceable> into the file
  <replaceable>destination_sound.wav</replaceable>.
  You may want to normalize the sound before encoding, as DVD audio tracks
  are commonly recorded at low volumes.
  You can use the tool <application>normalize</application> for instance,
  which is available in most distributions.
  If you're using Windows, a tool such as <application>BeSweet</application>
  can do the same job.
  You will compress in either Vorbis or MP3.
  For example:
  <screen>oggenc -q1 <replaceable>destination_sound.wav</replaceable></screen>
  will encode <replaceable>destination_sound.wav</replaceable> with
  the encoding quality 1, which is roughly equivalent to 80Kb/s, and
  is the minimum quality at which you should encode if you care about
  quality.
  Please note that MEncoder currently cannot mux Vorbis audio tracks
  into the output file because it only supports AVI and MPEG
  containers as an output, each of which may lead to audio/video
  playback synchronization problems with some players when the AVI file
  contain VBR audio streams such as Vorbis.
  Don't worry, this document will show you how you can do that with third
  party programs.
</para>

</sect2>

<sect2 id="menc-feat-dvd-mpeg4-interlacing">
<title>Interlacing and Telecine</title>

<para>
  Almost all movies are shot at 24 fps. Because NTSC is 30000/1001 fps, some
  processing must be done to this 24 fps video to make it run at the correct
  NTSC framerate. The process is called 3:2 pulldown, commonly referred to
  as telecine (because pulldown is often applied during the telecine
  process), and, naively described, it works by slowing the film down to
  24000/1001 fps, and repeating every fourth frame.
</para>

<para>
  No special processing, however, is done to the video for PAL DVDs, which
  run at 25 fps. (Technically, PAL can be telecined, called 2:2 pulldown,
  but this doesn't become an issue in practice.) The 24 fps film is simply
  played back at 25 fps. The result is that the movie runs slightly faster,
  but unless you're an alien, you probably won't notice the difference.
  Most PAL DVDs have pitch-corrected audio, so when they're played back at
  25 fps things will sound right, even though the audio track (and hence the
  whole movie) has a running time that's 4% less than NTSC DVDs.
</para>

<para>
  Because the video in a PAL DVD hasn't been altered, you needn't worry
  much about frame rate. The source is 25 fps, and your rip will be 25
  fps. However, if you're ripping an NTSC DVD movie, you may need to
  apply inverse telecine.
</para>

<para>
  For movies shot at 24 fps, the video on the NTSC DVD is either telecined
  30000/1001, or else it is progressive 24000/1001 fps and intended to be telecined
  on-the-fly by a DVD player. On the other hand, TV series are usually
  only interlaced, not telecined. This is not a hard rule: some TV series
  are interlaced (such as Buffy the Vampire Slayer) whereas some are a
  mixture of progressive and interlaced (such as Angel, or 24).
</para>

<para>
  It's highly recommended that you read the section on
  <link linkend="menc-feat-telecine">How to deal with telecine and interlacing in NTSC DVDs</link>
  to learn how to handle the different possibilities.
</para>

<para>
  However, if you're mostly just ripping movies, likely you're either
  dealing with 24 fps progressive or telecined video, in which case you can
  use the <option>pullup</option> filter <option>-vf
  pullup,softskip</option>.
</para>

</sect2>


<sect2 id="menc-feat-dvd-mpeg4-filtering">
<title>Filtering</title>

<para>
  In general, you want to do as little filtering as possible to the movie
  in order to remain close to the original DVD source. Cropping is often
  necessary (as described above), but do not scale the video. Although
  scaling down is sometimes preferred to using higher quantizers, we want
  to avoid both these things: remember that we decided from the start to
  trade bits for quality.
</para>

<para>
  Also, do not adjust gamma, contrast, brightness, etc. What looks good
  on your display may not look good on others. These adjustments should
  be done on playback only.
</para>

<para>
  One thing you might want to do, however, is pass the video through a
  very light denoise filter, such as <option>-vf hqdn3d=2:1:2</option>.
  Again, it's a matter of putting those bits to better use: why waste them
  encoding noise when you can just add that noise back in during playback?
  Increasing the parameters for <option>hqdn3d</option> will further
  improve compressibility, but if you increase the values too much, you
  risk degrading the image visibily. The suggested values above
  (<option>2:1:2</option>) are quite conservative; you should feel free to
  experiment with higher values and observe the results for yourself.
</para>

</sect2>

<sect2 id="menc-feat-dvd-mpeg4-lavc-encoding-options">
<title>Encoding options of libavcodec</title>

<para>
  Ideally, you'd probably want to be able to just tell the encoder to switch
  into "high quality" mode and move on.
  That would probably be nice, but unfortunately hard to implement as different
  encoding options yield different quality results depending on the source material.
  That's because compression depends on the visual properties of the video
  in question.
  For example, anime and live action have very different properties and
  thus require different options to obtain optimum encoding.
  The good news is that some options should never be left out, like
  <option>mbd=2</option>, <option>trell</option>, and <option>v4mv</option>.
  See below for a detailed description of common encoding options.
</para>


<itemizedlist>
<title>Options to adjust:</title>
<listitem><para>
  <emphasis role="bold">vmax_b_frames</emphasis>: 1 or 2 is good, depending on
  the movie.
  Note that libavcodec does not yet support closed GOP (the option
  <option>cgop</option> doesn't currently work), so DivX5 won't be able to
  decode anything encoded with B-frames.
</para></listitem>

<listitem><para>
  <emphasis role="bold">vb_strategy=1</emphasis>: helps in high-motion scenes.
  Requires vmax_b_frames >= 2.
  On some videos, vmax_b_frames may hurt quality, but vmax_b_frames=2 along
  with vb_strategy=1 helps.
</para></listitem>

<listitem><para>
  <emphasis role="bold">dia</emphasis>: motion search range. Bigger is better
  and slower.
  Negative values are a completely different scale.
  Good values are -1 for a fast encode, or 2-4 for slower.
</para></listitem>

<listitem><para>
  <emphasis role="bold">predia</emphasis>: motion search pre-pass.
  Not as important as dia. Good values are 1 (default) to 4. Requires preme=2
  to really be useful.
</para></listitem>

<listitem><para>
  <emphasis role="bold">cmp, subcmp, precmp</emphasis>: Comparison function for
  motion estimation.
  Experiment with values of 0 (default), 2 (hadamard), 3 (dct), and 6 (rate
  distortion).
  0 is fastest, and sufficient for precmp.
  For cmp and subcmp, 2 is good for anime, and 3 is good for live action.
  6 may or may not be slightly better, but is slow.
</para></listitem>

<listitem><para>
  <emphasis role="bold">last_pred</emphasis>: Number of motion predictors to
  take from the previous frame.
  1-3 or so help at little speed cost.
  Higher values are slow for no extra gain.
</para></listitem>

<listitem><para>
  <emphasis role="bold">cbp, mv0</emphasis>: Controls the selection of macroblocks.
  Small speed cost for small quality gain.
</para></listitem>

<listitem><para>
  <emphasis role="bold">qprd</emphasis>: adaptive quantization based on the
  macroblock's complexity.
  May help or hurt depending on the video and other options.
  This can cause artifacts unless you set vqmax to some reasonably small value
  (6 is good, maybe as low as 4); vqmin=1 should also help.
</para></listitem>

<listitem><para>
  <emphasis role="bold">qns</emphasis>: very slow, especially when combined
  with qprd.
  This option will make the encoder minimize noise due to compression
  artifacts instead of making the encoded video strictly match the source.
  Don't use this unless you've already tweaked everything else as far as it
  will go and the results still aren't good enough.
</para></listitem>

<listitem><para>
  <emphasis role="bold">vqcomp</emphasis>: Tweak ratecontrol.
  What values are good depends on the movie.
  You can safely leave this alone if you want.
  Reducing vqcomp puts more bits on low-complexity scenes, increasing it puts
  them on high-complexity scenes (default: 0.5, range: 0-1. recommended range:
  0.5-0.7).
</para></listitem>

<listitem><para>
  <emphasis role="bold">vlelim, vcelim</emphasis>: Sets the single coefficient
  elimination threshold for luminance and chroma planes.
  These are encoded separately in all MPEG-like algorithms.
  The idea behind these options is to use some good heuristics to determine
  when the change in a block is less than the threshold you specify, and in
  such a case, to just  encode the block as "no change".
  This saves bits and perhaps speeds up encoding. vlelim=-4 and vcelim=9
  seem to be good for live movies, but seem not to help with anime;
  when encoding animation, you should probably leave them unchanged.
</para></listitem>

<listitem><para>
  <emphasis role="bold">qpel</emphasis>: Quarter pixel motion estimation.
  MPEG-4 uses half pixel precision for its motion search by default,
  therefore this option comes with an overhead as more information will be
  stored in the encoded file.
  The compression gain/loss depends on the movie, but it's usually not very
  effective on anime.
  qpel always incurs a significant cost in CPU decode time (+20% in
  practice).
</para></listitem>

<listitem><para>
  <emphasis role="bold">psnr</emphasis>: doesn't affect the actual encoding,
  but writes a log file giving the type/size/quality of each frame, and
  prints a summary of PSNR (Peak Signal to Noise Ratio) at the end.
</para></listitem>

</itemizedlist>

<itemizedlist>
<title>Options not recommended to play with:</title>
<listitem><para>
  <emphasis role="bold">vme</emphasis>: The default is best.
</para></listitem>

<listitem><para>
  <emphasis role="bold">lumi_mask, dark_mask</emphasis>: Psychovisual adaptive
  quantization.
  You don't want to play with those options if you care about quality.
  Reasonable values may be effective in your case, but be warned this is very
  subjective.
</para></listitem>

<listitem><para>
  <emphasis role="bold">scplx_mask</emphasis>: Tries to prevent blocky
  artifacts, but postprocessing is better.
</para></listitem>
</itemizedlist>

</sect2>

<sect2 id="menc-feat-dvd-mpeg4-example">
<title>Example</title>

<para>
  So, you've just bought your shiny new copy of Harry Potter and the Chamber
  of Secrets (widescreen edition, of course), and you want to rip this DVD
  so that you can add it to your Home Theatre PC. This is a region 1 DVD,
  so it's NTSC. The example below will still apply to PAL, except you'll
  omit <option>-ofps 24000/1001</option> (because the output framerate is the
  same as the input framerate), and of course the crop dimensions will be
  different.
</para>

<para>
  After running <option>mplayer dvd://1</option>, we follow the process
  detailed in the section <link linkend="menc-feat-telecine">How to deal
  with telecine and interlacing in NTSC DVDs</link> and discover that it's
  24000/1001 fps progressive video, which means that we needn't use an inverse
  telecine filter, such as <option>pullup</option> or
  <option>filmdint</option>.
</para>

<para>
  Next, we want to determine the appropriate crop rectangle, so we use the
  cropdetect filter:

  <screen>mplayer dvd://1 -vf cropdetect</screen>

  Make sure you seek to a fully filled frame (such as a bright scene), and
  you'll see in <application>MPlayer</application>'s console output:

  <screen>crop area: X: 0..719  Y: 57..419  (-vf crop=720:362:0:58)</screen>

  We then play the movie back with this filter to test its correctness:

  <screen>mplayer dvd://1 -vf crop=720:362:0:58</screen>

  And we see that it looks perfectly fine. Next, we ensure the width and
  height are a multiple of 16. The width is fine, however the height is
  not. Since we didn't fail 7th grade math, we know that the nearest
  multiple of 16 lower than 362 is 352.
</para>

<para>
  We could just use <option>crop=720:352:0:58</option>, but it'd be nice
  to take a little off the top and a little off the bottom so that we
  retain the center. We've shrunk the height by 10 pixels, but we don't
  want to increase the y-offset by 5-pixels since that's an odd number and
  will adversely affect quality. Instead, we'll increase the y-offset by
  4 pixels:

  <screen>mplayer dvd://1 -vf crop=720:352:0:62</screen>

  Another reason to shave pixels from both the top and the bottom is that we
  ensure we've eliminated any half-black pixels if they exist. Note that if
  your video is telecined, make sure the <option>pullup</option> filter (or
  whichever inverse telecine filter you decide to use) appears in the filter
  chain before you crop. If it is interlaced, deinterlace before cropping.
  (If you choose to preserve the interlaced video, then make sure your
  vertical crop offset is a multiple of 4.)
</para>

<para>
  If you're really concerned about losing those 10 pixels, you might
  prefer instead to scale the dimensions down to the nearest multiple of 16.
  The filter chain would look like:

  <screen>-vf crop=720:362:0:58,scale=720:352</screen>

  Scaling the video down like this will mean that some small amount of
  detail is lost, though it probably won't be perceptible. Scaling up will
  result in lower quality (unless you increase the bitrate). Cropping
  discards those pixels altogether. It's a tradeoff that you'll want to
  consider for each circumstance. For example, if the DVD video was made
  for television, you might want to avoid vertical scaling, since the line
  sampling corresponds to the way the content was originally recorded.
</para>

<para>
  On inspection, we see that our movie has a fair bit of action and high
  amounts of detail, so we pick 2400Kbit for our bitrate.
</para>

<para>
  We're now ready to do the two pass encode. Pass one:

  <screen>mencoder dvd://1 -ofps 24000/1001 -oac copy -vf crop=720:352:0:62,hqdn3d=2:1:2 -ovc lavc \
-lavcopts vcodec=mpeg4:vbitrate=2400:v4mv:mbd=2:trell:cmp=3:subcmp=3:mbcmp=3:autoaspect:vpass=1 \
-o Harry_Potter_2.avi</screen>

  And pass two is the same, except that we specify <option>vpass=2</option>:

  <screen>mencoder dvd://1 -ofps 24000/1001 -oac copy -vf crop=720:352:0:62,hqdn3d=2:1:2 -ovc lavc \
-lavcopts vcodec=mpeg4:vbitrate=2400:v4mv:mbd=2:trell:cmp=3:subcmp=3:mbcmp=3:autoaspect:vpass=2 \
-o Harry_Potter_2.avi</screen>
</para>

<para>
  The options <option>v4mv:mbd=2:trell</option> will greatly increase the
  quality at the expense of encoding time. There's little reason to leave
  these options out when the primary goal is quality. The options
  <option>cmp=3:subcmp=3:mbcmp=3</option> select a comparison function that
  yields higher quality than the defaults. You might try experimenting with
  this parameter (refer to the man page for the possible values) as
  different functions can have a large impact on quality depending on the
  source material. For example, if you find
  <systemitem class="library">libavcodec</systemitem> produces too much
  blocky artifacting, you could try selecting the experimental NSSE as
  comparison function via <option>*cmp=10</option>.
</para>

<para>
  For this movie, the resulting AVI will be 138 minutes long and nearly
  3GB. And because you said that file size doesn't matter, this is a
  perfectly acceptable size. However, if you had wanted it smaller, you
  could try a lower bitrate. Increasing bitrates have diminishing
  returns, so while we might clearly see an improvement from 1800Kbit to
  2000Kbit, it might not be so noticeable above 2000Kbit. Feel
  free to experiment until you're happy.
</para>

<para>
  Because we passed the source video through a denoise filter, you may want
  to add some of it back during playback. This, along with the
  <option>spp</option> post-processing filter, drastically improves the
  perception of quality and helps eliminate blocky artifacts in the video.
  With <application>MPlayer</application>'s <option>autoq</option> option,
  you can vary the amount of post-processing done by the spp filter
  depending on available CPU. Also, at this point, you may want to apply
  gamma and/or color correction to best suit your display. For example:

  <screen>mplayer Harry_Potter_2.avi -vf spp,noise=9ah:5ah,eq2=1.2 -autoq 3</screen>

</para>
</sect2>

<sect2 id="menc-feat-dvd-mpeg4-muxing">
<title>Muxing</title>
<para>
  Now that you have encoded your video, you will most likely want
  to mux it with one or more audio tracks into a movie container, such
  as AVI, MPEG, Matroska or NUT.
  <application>MEncoder</application> is currently only able to output
  audio and video into MPEG and AVI container formats.
  for example:
  <screen>mencoder -oac copy -ovc copy  -o <replaceable>output_movie.avi</replaceable> -audiofile <replaceable>input_audio.mp2</replaceable> <replaceable>input_video.avi</replaceable></screen>
  This would merge the video file <replaceable>input_video.avi</replaceable>
  and the audio file <replaceable>input_audio.mp2</replaceable>
  into the AVI file <replaceable>output_movie.avi</replaceable>.
  This command works with MPEG-1 layer I, II and III (more commonly known
  as MP3) audio, WAV and a few other audio formats too.
</para>

<para>
  MEncoder features experimental support for
  <systemitem class="library">libavformat</systemitem>, which is a
  library from the FFmpeg project that supports muxing and demuxing
  a variety of containers.
  For example:
  <screen>mencoder -oac copy -ovc copy  -o <replaceable>output_movie.asf</replaceable> -audiofile <replaceable>input_audio.mp2</replaceable> <replaceable>input_video.avi</replaceable> -of lavf -lavfopts format=asf</screen>
  This will do the same thing as the previous example, except that
  the output container will be ASF.
  Please note that this support is highly experimental (but getting
  better every day), and will only work if you compiled
  <application>MPlayer</application> with the support for
  <systemitem class="library">libavformat</systemitem> enabled (which
  means that a pre-packaged binary version will not work in most cases).
</para>

<sect3 id="menc-feat-dvd-mpeg4-muxing-avi-limitations">
<title>Limitations of the AVI container</title>
<para>
  Although it is the most widely-supported container format after MPEG-1,
  AVI also has some major drawbacks.
  Perhaps the most obvious is the overhead.
  For each chunk of the AVI file, 24 bytes are wasted on headers and
  index.
  This translates into a little over 5 MB per hour, or 1-2.5%
  overhead for a 700 MB movie. This may not seem like much, but it could
  mean the difference between being able to use 700 kbit/sec video or
  714 kbit/sec, and every bit of quality counts.
</para>

<para>
  In addition this gross inefficiency, AVI also has the following major
  limitations:
</para>

<orderedlist>
<listitem>
<para>
  Only fixed-fps content can be stored. This is particularly limiting
  if the original material you want to encode is mixed content, for
  example a mix of NTSC video and film material.
  Actually there are hacks that can be used to store mixed-framerate
  content in AVI, but they increase the (already huge) overhead
  fivefold or more and so are not practical.
</para>
</listitem>
<listitem>
<para>
  Audio in AVI files must be either constant-bitrate (CBR) or
  constant-framesize (i.e. all frames decode to the same number of
  samples).
  Unfortunately, the most efficient codec, Vorbis, does not meet
  either of these requirements.
  Therefore, if you plan to store your movie in AVI, you'll have to
  use a less efficient codec such as MP3 or AC3.
</para>
</listitem>
</orderedlist>

<para>
  Having said all that, <application>MEncoder</application> does not
  currently support variable-fps output or Vorbis encoding.
  Therefore, you may not see these as limitations if
  <application>MEncoder</application> is the
  only tool you will be using to produce your encodes.
  However, it is possible to use <application>MEncoder</application>
  only for video encoding, and then use external tools to encode
  audio and mux it into another container format.
</para>
</sect3>

<sect3 id="menc-feat-dvd-mpeg4-muxing-matroska">
<title>Muxing into the Matroska container</title>
<para>
  The Matroska is a free, open standard container format, aiming
  to offer a lot of advanced features, which older containers
  like AVI cannot handle.
  For example, Matroska supports variable bitrate audio content
  (VBR), variable framerates (VFR), chapters, file attachments,
  error detection (EDC) and modern A/V Codecs like "advanced audio
  coding" (AAC), "Vorbis" or "MPEG-4 AVC" (H.264), next to nothing
  handled by AVI.
</para>

<para>
  The tools required to create Matroska files are collectively called
  <application>mkvtoolnix</application>, and are available for most
  Unix platforms as well as <application>Windows</application>.
  Given that Matroska is an open standard, you may find other
  tools that suit you better, but since mkvtoolnix is the most
  common, and is supported by the Matroska team itself, we will
  only cover its usage.
</para>

<para>
  Probably the easiest way to get started with Matroska is to use 
  <application>MMG</application>, the graphical frontend shipped with
  <application>mkvtoolnix</application>, and follow the
  <ulink url="http://www.bunkus.org/videotools/mkvtoolnix/doc/mkvmerge-gui.html">guide to mkvmerge GUI (mmg)</ulink>
</para>

<para>
  You may also mux audio and video files using the command line:
  <screen>mkvmerge -o <replaceable>output.mkv</replaceable> <replaceable>input_video.avi</replaceable> <replaceable>input_audio1.mp3</replaceable> <replaceable>input_audio2.ac3</replaceable></screen>
  This would merge the video file <replaceable>input_video.avi</replaceable>
  and the two audio files <replaceable>input_audio1.mp3</replaceable>
  and <replaceable>input_audio2.ac3</replaceable> into the Matroska
  file <replaceable>output.mkv</replaceable>.
  Matroska, as mentioned earlier, is able to do much more than that, like
  multiple audio tracks (including fine-tuning of audio/video
  synchronization), chapters, subtitles, splitting, etc...
  Please refer to the documentation of those applications for
  more details.
</para>

</sect3>

</sect2>

</sect1>

<sect1 id="menc-feat-telecine">
<title>How to deal with telecine and interlacing within NTSC DVDs</title>

<sect2 id="menc-feat-telecine-intro">
<title>Introduction</title>
<formalpara>
<title>What is telecine?</title>
<para>
  I suggest you visit this page if you don't understand much of what
  is written in this document:
  <ulink url="http://www.divx.com/support/guides/guide.php?gid=10">http://www.divx.com/support/guides/guide.php?gid=10</ulink>
  This URL links to an understandable and reasonably comprehensive
  description of what telecine is.
</para></formalpara>

<formalpara>
<title>A note about the numbers.</title>
<para>
  Many documents, including the guide linked above, refer to the fields
  per second value of NTSC video as 59.94 and the corresponding frames
  per second values as 29.97 (for telecined and interlaced) and 23.976
  (for progressive). For simplicity, some documents even round these
  numbers to 60, 30, and 24.
</para></formalpara>

<para>
  Strictly speaking, all those numbers are approximations. Black and
  white NTSC video was exactly 60 fields per second, but 60000/1001
  was later chosen to accomodate color data while remaining compatible
  with contemporary black and white televisions. Digital NTSC video
  (such as on a DVD) is also 60000/1001 fields per second. From this,
  interlaced and telecined video are derived to be 30000/1001 frames
  per second; progressive video is 24000/1001 frames per second.
</para>

<para>
  Older versions of the <application>MEncoder</application> documentation
  and many archived mailing list posts refer to 59.94, 29.97, and 23.976.
  All <application>MEncoder</application> documentation has been updated
  to use the fractional values, and you should use them too.
</para>

<para>
  <option>-ofps 23.976</option> is incorrect.
  <option>-ofps 24000/1001</option> should be used instead.
</para>

<formalpara>
<title>How telecine is used.</title>
<para>
  All video intended to be displayed on an NTSC
  television set must be 60000/1001 fields per second. Made-for-TV movies
  and shows are often filmed directly at 60000/1001 fields per second, but
  the majority of cinema is filmed at 24 or 24000/1001 frames per
  second. When cinematic movie DVDs are mastered, the video is then
  converted for television using a process called telecine.
</para></formalpara>

<para>
  On a DVD, the video is never actually stored as 60000/1001 fields per
  second. For video that was originally 60000/1001, each pair of fields is
  combined to form a frame, resulting in 30000/1001 frames per
  second. Hardware DVD players then read a flag embedded in the video
  stream to determine whether the odd- or even-numbered lines should
  form the first field.
</para>

<para>
  Usually, 24000/1001 frames per second content stays as it is when
  encoded for a DVD, and the DVD player must perform telecining
  on-the-fly. Sometimes, however, the video is telecined
  <emphasis>before</emphasis> being stored on the DVD; even though it
  was originally 24000/1001 frames per second, it becomes 60000/1001 fields per
  second. When it is stored on the DVD, pairs of fields are combined to form
  30000/1001 frames per second.
</para>

<para>
  When looking at individual frames formed from 60000/10001 fields per
  second video, telecined or otherwise, interlacing is clearly visible
  wherever there is any motion, because one field (say, the
  even-numbered lines) represents a moment in time 1/(60000/1001)
  seconds later than the other. Playing interlaced video on a computer
  looks ugly both because the monitor is higher resolution and because
  the video is shown frame-after-frame instead of field-after-field.
</para>

<itemizedlist>
<title>Notes:</title>
<listitem><para>
  This section only applies to NTSC DVDs, and not PAL.
  </para></listitem>
<listitem><para>
  The example <application>MEncoder</application> lines throughout the
  document are <emphasis role="bold">not</emphasis> intended for
  actual use. They are simply the bare minimum required to encode the
  pertaining video category. How to make good DVD rips or fine-tune
  <systemitem class="library">libavcodec</systemitem> for maximal
  quality is not within the scope of this document.
  </para></listitem>
<listitem><para>
  There are a couple footnotes specific to this guide, linked like this:
  <link linkend="menc-feat-telecine-footnotes">[1]</link>
  </para></listitem>
</itemizedlist>
</sect2>

<sect2 id="menc-feat-telecine-ident">
<title>How to tell what type of video you have</title>

<sect3 id="menc-feat-telecine-ident-progressive">
<title>Progressive</title>
<para>
  Progressive video was originally filmed at 24000/1001 fps, and stored
  on the DVD without alteration.
</para>

<para>
  When you play a progressive DVD in <application>MPlayer</application>,
  <application>MPlayer</application> will print the following line as
  soon as the movie begins to play:

  <screen> demux_mpg: 24000/1001 fps progressive NTSC content detected, switching framerate.</screen>

  From this point forward, demux_mpg should never say it finds
  &quot;30000/1001 fps NTSC content.&quot;
</para>

<para>
  When you watch progressive video, you should never see any
  interlacing. Beware, however, because sometimes there is a tiny bit
  of telecine mixed in where you wouldn't expect. I've encountered TV
  show DVDs that have one second of telecine at every scene change, or
  at seemingly random places. I once watched a DVD that had a
  progressive first half, and the second half was telecined. If you
  want to be <emphasis>really</emphasis> thorough, you can scan the
  entire movie:

  <screen>mplayer dvd://1 -nosound -vo null -benchmark</screen>

  Using <option>-benchmark</option> makes
  <application>MPlayer</application> play the movie as quickly as it
  possibly can; still, depending on your hardware, it can take a
  while. Every time demux_mpg reports a framerate change, the line
  immediately above will show you the time at which the change
  occurred.
</para>

<para>
  Sometimes progressive video on DVDs is referred to as
  &quot;soft-telecine&quot; because it is intended to
  be telecined by the DVD player.
</para>
</sect3>

<sect3 id="menc-feat-telecine-ident-telecined">
<title>Telecined</title>
<para>
  Telecined video was originally filmed at 24000/1001, but was telecined
  <emphasis>before</emphasis> it was written to the DVD.
</para>

<para>
  <application>MPlayer</application> does not (ever) report any
  framerate changes when it plays telecined video.
</para>

<para>
  Watching a telecined video, you will see interlacing artifacts that
  seem to &quot;blink&quot;: they repeatedly appear and disappear.
  You can look closely at this by
  <orderedlist>
  <listitem>
    <screen>mplayer dvd://1</screen>
    </listitem>
  <listitem><para>
    Seek to a part with motion.
    </para></listitem>
  <listitem><para>
    Use the <keycap>.</keycap> key to step forward one frame at a time.
    </para></listitem>
  <listitem><para>
    Look at the pattern of interlaced-looking and progressive-looking
    frames. If the pattern you see is PPPII,PPPII,PPPII,... then the
    video is telecined. If you see some other pattern, then the video
    may have been telecined using some non-standard method;
    <application>MEncoder</application> cannot losslessly convert
    non-standard telecine to progressive. If you don't see any
    pattern at all, then it is most likely interlaced.
    </para></listitem>
  </orderedlist>
</para>

<para>
  Sometimes telecined video on DVDs is referred to as
  &quot;hard-telecine&quot;. Since hard-telecine is already 60000/1001 fields
  per second, the DVD player plays the video without any manipulation.
</para>
</sect3>

<sect3 id="menc-feat-telecine-ident-interlaced">
<title>Interlaced</title>
<para>
  Interlaced video was originally filmed at 60000/1001 fields per second,
  and stored on the DVD as 30000/1001 frames per second. The interlacing effect
  (often called &quot;combing&quot;) is a result of combining pairs of
  fields into frames. Each field is supposed to be 1/(60000/1001) seconds apart,
  and when they are displayed simultaneously the difference is apparent.
</para>

<para>
  As with telecined video, <application>MPlayer</application> should
  not ever report any framerate changes when playing interlaced content.
</para>

<para>
  When you view an interlaced video closely by frame-stepping with the
  <keycap>.</keycap> key, you will see that every single frame is interlaced.
</para>
</sect3>

<sect3 id="menc-feat-telecine-ident-mixedpt">
<title>Mixed progressive and telecine</title>
<para>
  All of a &quot;mixed progressive and telecine&quot; video was originally
  24000/1001 frames per second, but some parts of it ended up being telecined.
</para>

<para>
  When <application>MPlayer</application> plays this category, it will
  (often repeatedly) switch back and forth between &quot;30000/1001 fps NTSC&quot;
  and &quot;24000/1001 fps progressive NTSC&quot;. Watch the bottom of
  <application>MPlayer</application>'s output to see these messages.
</para>

<para>
  You should check the &quot;30000/1001 fps NTSC&quot; sections to make sure
  they are actually telecine, and not just interlaced.
</para>
</sect3>

<sect3 id="menc-feat-telecine-ident-mixedpi">
<title>Mixed progressive and interlaced</title>
<para>
  In &quot;mixed progressive and interlaced&quot; content, progressive
  and interlaced video have been spliced together.
</para>

<para>
  This category looks just like &quot;mixed progressive and telecine&quot;,
  until you examine the 30000/1001 fps sections and see that they don't have the
  telecine pattern.
</para>
</sect3>

</sect2>

<sect2 id="menc-feat-telecine-encode">
<title>How to encode each category</title>
<para>
  As I mentioned in the beginning, example <application>MEncoder</application>
  lines below are <emphasis role="bold">not</emphasis> meant to actually be used;
  they only demonstrate the minimum parameters to properly encode each category.
</para>

<sect3 id="menc-feat-telecine-encode-progressive">
<title>Progressive</title>
<para>
  Progressive video requires no special filtering to encode. The only
  parameter you need to be sure to use is
  <option>-ofps 24000/1001</option>. Otherwise, <application>MEncoder</application>
  will try to encode at 30000/1001 fps and will duplicate frames.
</para>

<para>
  <screen>mencoder dvd://1 -nosound -ovc lavc -ofps 24000/1001</screen>
</para>

<para>
  It is often the case, however, that a video that looks progressive
  actually has very short parts of telecine mixed in. Unless you are
  sure, it is safest to treat the video as
  <link linkend="menc-feat-telecine-encode-mixedpt">mixed progressive and telecine</link>.
  The performance loss is small
  <link linkend="menc-feat-telecine-footnotes">[3]</link>.
</para>
</sect3>

<sect3 id="menc-feat-telecine-encode-telecined">
<title>Telecined</title>
<para>
  Telecine can be reversed to retrieve the original 24000/1001 content,
  using a process called inverse-telecine.
  <application>MPlayer</application> contains several filters to
  accomplish this; the best filter, <option>pullup</option>, is described
  in the <link linkend="menc-feat-telecine-encode-mixedpt">mixed
  progressive and telecine</link> section.
</para>
</sect3>

<sect3 id="menc-feat-telecine-encode-interlaced">
<title>Interlaced</title>
<para>
  For most practical cases it is not possible to retrieve a complete
  progressive video from interlaced content. The only way to do so
  without losing half of the vertical resolution is to double the
  framerate and try to &quot;guess&quot; what ought to make up the
  corresponding lines for each field (this has drawbacks - see method
  3).
</para>

<orderedlist>
<listitem><para>

  Encode the video in interlaced form. Normally, interlacing wreaks
  havoc with the encoder's ability to compress well, but
  <systemitem class="library">libavcodec</systemitem> has two
  parameters specifically for dealing with storing interlaced video a
  bit better: <option> ildct</option> and <option>ilme</option>. Also,
  using <option>mbd=2</option> is strongly recommended
  <link linkend="menc-feat-telecine-footnotes">[2] </link> because it
  will encode macroblocks as non-interlaced in places where there is
  no motion. Note that <option>-ofps</option> is NOT needed here.

  <screen>mencoder dvd://1 -nosound -ovc lavc -lavcopts ildct:ilme:mbd=2</screen>
  </para></listitem>
<listitem><para>
  Use a deinterlacing filter before encoding. There are several of
  these filters available to choose from, each with its own advantages
  and disadvantages. Consult <option>mplayer -pphelp</option> to see
  what's available (grep for &quot;deint&quot;), and search the
  <ulink url="http://www.mplayerhq.hu/homepage/design6/info.html#mailing_lists">
  MPlayer mailing lists</ulink> to find many discussions about the
  various filters. Again, the framerate is not changing, so no
  <option>-ofps</option>. Also, deinterlacing should be done after
  cropping <link linkend="menc-feat-telecine-footnotes">[1]</link> and
  before scaling.

  <screen>mencoder dvd://1 -nosound -vf pp=lb -ovc lavc</screen>
  </para></listitem>
<listitem><para>
  Unfortunately, this option is buggy with
  <application>MEncoder</application>; it ought to work well with
  <application>MEncoder G2</application>, but that isn't here yet. You
  might experience crahes. Anyway, the purpose of <option> -vf
  tfields</option> is to create a full frame out of each field, which
  makes the framerate 60000/1001. The advantage of this approach is that no
  data is ever lost; however, since each frame comes from only one
  field, the missing lines have to be interpolated somehow. There are
  no very good methods of generating the missing data, and so the
  result will look a bit similar to when using some deinterlacing
  filters. Generating the missing lines creates other issues, as well,
  simply because the amount of data doubles. So, higher encoding
  bitrates are required to maintain quality, and more CPU power is
  used for both encoding and decoding. tfields has several different
  options for how to create the missing lines of each frame. If you
  use this method, then Reference the manual, and chose whichever
  option looks best for your material. Note that when using
  <option>tfields</option> you
  <emphasis role="bold">have to</emphasis> specify both
  <option>-fps</option> and <option>-ofps</option> to be twice the
  framerate of your original source.

  <screen>mencoder dvd://1 -nosound -vf tfields=2 -ovc lavc -fps 60000/1001 -ofps 60000/1001</screen>
  </para></listitem>
<listitem><para>
  If you plan on downscaling dramatically, you can extract and encode
  only one of the two fields. Of course, you'll lose half the vertical
  resolution, but if you plan on downscaling to at most 1/2 of the
  original, the loss won't matter much. The result will be a
  progressive 30000/1001 frames per second file. The procedure is to use
  <option>-vf field</option>, then crop
  <link linkend="menc-feat-telecine-footnotes">[1]</link> and scale
  appropriately. Remember that you'll have to adjust the scale to
  compensate for the vertical resolution being halved.
  <screen>mencoder dvd://1 -nosound -vf field=0 -ovc lavc</screen>
  </para></listitem>
</orderedlist>
</sect3>

<sect3 id="menc-feat-telecine-encode-mixedpt">
<title>Mixed progressive and telecine</title>
<para>
  In order to turn mixed progressive and telecine video into entirely
  progressive video, the telecined parts have to be
  inverse-telecined. There are three ways to accomplish this,
  described below. Note that you should
  <emphasis role="bold">always</emphasis> inverse-telecine before any
  rescaling; unless you really know what you're doing,
  inverse-telecine before cropping, too
  <link linkend="menc-feat-telecine-footnotes">[1]</link>.
  <option>-ofps 24000/1001</option> is needed here because the output video
  will be 24000/1001 frames per second.
</para>

<itemizedlist>
<listitem><para>
  <option>-vf pullup</option> is designed to inverse-telecine
  telecined material while leaving progressive data alone. In order to
  work properly, <option>pullup</option> <emphasis role="bold">must</emphasis>
  be followed by the <option>softskip</option> filter or
  else <application>MEncoder</application> will crash.
  <option>pullup</option> is, however, the cleanest and most
  accurate method available for encoding both telecine and
  &quot;mixed progressive and telecine&quot;.

  <screen>mencoder dvd://1 -nosound -vf pullup,softskip -ovc lavc -ofps 24000/1001</screen>
  </para>


  </listitem>
  <listitem><para>
  An older method
  is to, rather than inverse-telecine the telecined parts, telecine
  the non-telecined parts and then inverse-telecine the whole
  video. Sound confusing? softpulldown is a filter that goes through
  a video and makes the entire file telecined. If we follow
  softpulldown with either <option>detc</option> or
  <option>ivtc</option>, the final result will be entirely
  progressive. <option>-ofps 24000/1001</option> is needed.

  <screen>mencoder dvd://1 -nosound -vf softpulldown,ivtc=1 -ovc lavc -ofps 24000/1001</screen>
  </para>
  </listitem>

<listitem><para>
  I haven't used <option>-vf filmdint</option> myself, but here's what
  D Richard Felker III has to say:

  <blockquote><para>It's OK, but IMO it tries to deinterlace rather
    than doing inverse telecine too often (much like settop DVD
    players &amp; progressive TVs) which gives ugly flickering and
    other artifacts. If you're going to use it, you at least need to
    spend some time tuning the options and watching the output first
    to make sure it's not messing up.</para></blockquote>
  </para></listitem>
</itemizedlist>
</sect3>

<sect3 id="menc-feat-telecine-encode-mixedpi">
<title>Mixed progressive and interlaced</title>
<para>
  There are two options for dealing with this category, each of
  which is a compromise. You should decide based on the
  duration/location of each type.
</para>

<itemizedlist>
<listitem><para>
  Treat it as progressive. The interlaced parts will look interlaced,
  and some of the interlaced fields will have to be dropped, resulting
  in a bit of uneven jumpiness. You can use a postprocessing filter if
  you want to, but it may slightly degrade the progressive parts.
  </para>

  <para>
  This option should definitely not be used if you want to eventually
  display the video on an interlaced device (with a TV card, for
  example). If you have interlaced frames in a 24000/1001 frames per
  second video, they will be telecined along with the progressive
  frames. Half of the interlaced "frames" will be displayed for three
  fields' duration (3/(60000/1001) seconds), resulting in a flicking
  &quot;jump back in time&quot; effect that looks quite bad. If you
  even attempt this, you <emphasis role="bold">must</emphasis> use a
  deinterlacing filter like <option>lb</option> or
  <option>l5</option>.
  </para>

  <para>
  It may also be a bad idea for progressive display, too. It will drop
  pairs of consecutive interlaced fields, resulting in a discontinuity
  that can be more visible than with the second method, which shows
  some progressive frames twice. 30000/1001 frames per second interlaced
  video is already a bit choppy because it really should be shown at
  60000/1001 fields per second, so the duplicate frames don't stand out as
  much.
  </para>

  <para>
  Either way, it's best to consider your content and how you intend to
  display it. If your video is 90% progressive and you never intend to
  show it on a TV, you should favor a progressive approach. If it's
  only half progressive, you probably want to encode it as if it's all
  interlaced.
  </para>
  </listitem>

<listitem><para>
  Treat it as interlaced. Some frames of the progressive parts will
  need to be duplicated, resulting in uneven jumpiness. Again,
  deinterlacing filters may slightly degrade the progressive parts.
  </para></listitem>

</itemizedlist>
</sect3>

</sect2>

<sect2 id="menc-feat-telecine-footnotes">
<title>Footnotes</title>
<orderedlist>
<listitem><formalpara>
  <title>About cropping:</title>
  <para>
  Video data on DVDs are stored in a format called YUV 4:2:0. In YUV
  video, luma (&quot;brightness&quot;) and chroma (&quot;color&quot;)
  are stored separately. Because the human eye is somewhat less
  sensitive to color than it is to brightness, in a YUV 4:2:0 picture
  there is only one chroma pixel for every four luma pixels. In a
  progressive picture, each square of four luma pixels (two on each
  side) has one common chroma pixel. You must crop progressive YUV
  4:2:0 to even resolutions, and use even offsets. For example,
  <option>crop=716:380:2:26</option> is OK but
  <option>crop=716:380:3:26 </option> is not.
  </para>
  </formalpara>

  <para>
  When you are dealing with interlaced YUV 4:2:0, the situation is a
  bit more complicated. Instead of every four luma pixels in the
  <emphasis>frame</emphasis> sharing a chroma pixel, every four luma
  pixels in each <emphasis> field</emphasis> share a chroma
  pixel. When fields are interlaced to form a frame, each scanline is
  one pixel high. Now, instead of all four luma pixels being in a
  square, there are two pixels side-by-side, and the other two pixels
  are side-by-side two scanlines down. The two luma pixels in the
  intermediate scanline are from the other field, and so share a
  different chroma pixel with two luma pixels two scanlines away. All
  this confusion makes it necessary to have vertical crop dimensions
  and offsets be multiples of four. Horizontal can stay even.
  </para>

  <para>
  For telecined video, I recommend that cropping take place after
  inverse telecining. Once the video is progressive you only need to
  crop by even numbers. If you really want to gain the slight speedup
  that cropping first may offer, you must crop vertically by multiples
  of four or else the inverse-telecine filter won't have proper data.
  </para>

  <para>
  For interlaced (not telecined) video, you must always crop
  vertically by multiples of four unless you use <option>-vf
  field</option> before cropping.
  </para>
  </listitem>

<listitem><formalpara>
  <title>About encoding parameters and quality:</title>
  <para>
  Just because I recommend <option>mbd=2</option> here doesn't mean it
  shouldn't be used elsewhere. Along with <option>trell</option>,
  <option>mbd=2</option> is one of the two
   <systemitem class="library">libavcodec</systemitem> options that
  increases quality the most, and you should always use at least those
  two unless the drop in encoding speed is prohibitive (e.g. realtime
  encoding). There are many other options to
  <systemitem class="library">libavcodec</systemitem> that increase
  encoding quality (and decrease encoding speed) but that is beyond
  the scope of this document.
  </para>
  </formalpara>
  </listitem>

<listitem><formalpara>
  <title>About the performance of pullup:</title>
  <para>
  It is safe to use <option>pullup</option> (along with <option>softskip
  </option>) on progressive video, and is usually a good idea unless
  the source has been definitively verified to be entirely progressive.
  The performace loss is small for most cases. On a bare-minimum encode,
  <option>pullup</option> causes <application>MEncoder</application> to
  be 50% slower. Adding sound processing and advanced <option>lavcopts
  </option> overshadows that difference, bringing the performance
  decrease of using <option>pullup</option> down to 2%.
  </para>
  </formalpara>
  </listitem>

</orderedlist>

</sect2>

</sect1>

</chapter>