[MPlayer-users] TV recording: audio faster than video (drifts)!?

Christian Niederreiter cndg at gmx.net
Tue Sep 19 15:25:50 CEST 2006


> > Thanks for your reply. I tried -mc 0 and -mc 1 (correct up to one
> > second/frame) but the drift didn't decrease in the least. 
> 
> Can you upload a segment of the file that exhibits the problem to
> /MPlayer/incoming ?

Maybe you could tell me start/end byte of the segment? I don't know the internals of an AVI file. Maybe I could record another but considerably shorter file instead (10 to 50 MBytes)?

> > All I know about -mc is "maximum A-V sync correction per frame (in
> > seconds)" but I have no clue why this could help me on :-)
> 
> By default, and with any nonzero value for -mc, MPlayer adjusts a/v sync
> using the flags in the file.  On occasion, they are wrong, and -mc 0
> will play the file properly.  With different file types, and with
> different -ao methods, larger or smaller -mc values may allow it to
> reach sync more quickly, or not desync as much in the first place.

To avoid misunderstandings, the way I applied -mc was the following:
mencoder tv://S11 -tv driver=v4l2:width=200:height=150:normid=0 -ovc lavc -oac lavc -o tv.avi -mc 0

> By default, and with any nonzero value for -mc, MPlayer adjusts a/v sync
> using the flags in the file.

I didn't encode from a file but rather directly from TV/audio input and
I don't want the playback software (e.g. VideoLAN, MPlayer,...) to
countervail the drift but rather MEncoder to produce proper AVIs.

My favorite players are VideoLAN and MPlayer. Both of them play audio
faster than video when I use them in order to play my MEncoder TV recordings. That shows MEncoder's output contains the drift.

Transcode took MEncoder's "corrupted" file which contained the drift and
"repaired" it automagically (i didn't pass any option to transcode).
Hence somewhere in the file that came from MEncoder transcode presumably
could find some information on how to remove the drift.
When MEncoder is able to provide information on how to remove the drift
and store that information in the output file, why doesn't it remove the drift itself before it writes the file to harddisk?

best regards, cn

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