[MPlayer-DOCS] [PATCH] Improving muxing reliability

[Guillaume POIRIER]

Hi there,

Here is a little sub-section that I would like to add to the "muxing"
section of he encoding guide. Please review.

<sect3 id="menc-feat-dvd-mpeg4-muxing-filter-issues">
<title>Improving muxing reliability</title>
<para>
  You may experience some serious A/V sync problems while trying to mux
  your video and some audio tracks, where no matter how your adjust the
  audio delay, you won't ever get proper sync.
  That may happen when you use some video filters that will drop or
  duplicate some frames, like the inverse telecine filters.
  It is strongly encouraged to append the <option>harddup</option> video
  filter at the end of the filter chain to avoid that kind of problems.
</para>

<para>
  Without <option>harddup</option>, <application>MEncoder</application>
  wants to duplicate a frame, it writes a zero byte frame into the muxer,
  causing an empty AVI packet that just maintains sync while writing no
  actual frame.
  With <option>harddup</option>, <application>MEncoder</application>
  will instead just pushes the last frame displayed again into the filter
  chain.
  This means that the encoder receives the <emphasis>exact</emphasis>
  same frame twice, and compresses it.
  This will result in a slightly bigger file but which won't cause problems
  when demuxing and remuxing them into other container formats.
</para>
</sect3>

Guillaume