[MEncoder-users] avi sync questions

[RC]

On Mon, 07 Apr 2008 14:03:09 +0200
Erik Slagter <erik at slagter.name> wrote:

> Are you saying that avi's produced by mencoder always their audio AND 
> video start at the first frame list entry AND that these are always a 
> video and audio sync that actually belong to the same moment in time? 

Yes, mencoder skips and/or duplicates frames to keep the video perfectly
synchronized with audio.  There is one minor exception (see
-audio-delay) but it's quite rare.

> That is not my experience, two years ago I used mencoder to create
> avi's  with mpeg4-2 for my media player, and they always had a/v sync
> issues  while mplayer played them fine. This looks like a/v skew in
> the file.

Mencoder simply doesn't have any code that could do what you're accusing
it of doing.  What you describe must have been the result of a bug
somewhere.

> I'd really like mencoder to produce two raw streams at the same time
> (either transcoded  or original) while mencoders takes care that the
> a/v sync as expressed  in the timestamps of the input file, are
> reflected in the raw output  files, by dropping or repeating audio or
> video frames.

What else could Mencoder possibly do?  It either does exactly that to
maintain A/V sync, or it does nothing at all (upon request).