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New section: Notes on Audio/Video synchronization, taken from Rich's encoding guide 

NOTE: someone please make sure the doc is cleanly generated.


git-svn-id: svn://svn.mplayerhq.hu/mplayer/trunk@16340 b3059339-0415-0410-9bf9-f77b7e298cf2
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gpoirier 2005-09-01 22:09:27 +00:00
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DOCS/xml/en/encoding-guide.xml
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@ -1288,6 +1288,48 @@ Note the <option>ilmv</option> and <option>ildct</option> options.
</sect2>
<sect2 id="menc-feat-dvd-mpeg4-av-sync">
<title>Notes on Audio/Video synchronization</title>
<para>
<application>MEncoder</application>'s audio/video synchronization
algorithms were designed with the intention of recovering files with
broken sync.
However they seem to cause unnecessary skipping and duplication of
frames, and possibly slight A/V desync, when used with proper input.
It is therefore recommended that you switch to basic A/V sync with
the <option>-mc 0</option> option, or put this in your
<systemitem>~/.mplayer/mencoder</systemitem> config file, as long as
you are only working with good sources (DVD, TV capture, high quality
MPEG-4 rips, etc) and not broken ASF/RM/MOV files.
</para>
<para>
If you want to further guard against strange frame skips and
duplication, you can use both <option>-mc 0</option> and
<option>-noskip</option>.
This will prevent <emphasis>all</emphasis> A/V sync, and copy frames
one-to-one, so you cannot use it if you will be using any filters that
unpredictably add or drop frames, or if your input file has variable
framerate!
Therefore, using <option>-noskip</option> is not in general recommended.
</para>
<para>
The so-called "three-pass" encoding which <application>MEncoder</application>
supports has been reported to cause A/V desync.
This will definitely happen if it is used in conjunction with certain
filters, therefore, it is now recommended <emphasis>not</emphasis> to
use three-pass mode.
This feature is only left for compatibility purposes and for expert
users who understand when it is safe to use and when it is not.
If you have never heard of three-pass mode before, forget that we
even mentioned it!
</para>
<para>
There have also been reports of A/V desync when encoding from stdin
with <application>MEncoder</application>.
Do not do this! Always use a file or CD/DVD/etc device as input.
</para>
</sect2>
<sect2 id="menc-feat-dvd-mpeg4-audio">
<title>Audio</title>