[MPlayer-users] Re: [BUG] mencoder -oac lavc produces bad audio sync

[Rich Felker]

On Tue, Apr 03, 2007 at 04:18:40PM -0600, Joey Parrish wrote:
> On 4/3/07, Joey Parrish <joey.parrish at gmail.com> wrote:
> >./mencoder $anything -ovc lavc -oac lavc -lavcopts
> >acodec=mp3:abitrate=64:vcodec=mpeg4:vbitrate=200 -o noname.avi
> >I also tried acodec=mp2 and acodec=ac3, same issues.
> >
> >Using mplayer noname.avi, video gets ahead of audio very fast.
> >Using mplayer -nobps noname.avi, it plays correctly.
> >Even with nobps option, audio restarts on any seek.
> >
> >If audio is encoded with mp3lame instead of lavc, the resulting file
> >has no problems what-so-ever.
> [snip]
> >In the mean time, I will continue my svn
> >search and try to identify the key change.
> 
> Aha!  I found it.  If I revert this change, the problem vanishes:
> http://svn.mplayerhq.hu/mplayer/trunk/libmpcodecs/ae_lavc.c?r1=21787&r2=21789&view=patch
> This is a December 29th commit by Michael.  If there are any devs
> still listening on this list, please look into it.  I don't know
> enough about the code in question to grok the problem or the fix
> myself.  For now, I will patch my local copy.

Reverting this patch is not correct either. The old behavior had
mencoder writing invalid 'CBR mode' AVI files where frames were split
across AVI packets. Such AVI files are not valid but many codecs (such
as mp3) can handle it anyway.

Michael was trying to fix this but I think he made a mistake...

Rich