[FFmpeg-user] Some inputs make MP4 output sync incompatible with other applications

[Francois Visagie]

> -----Original Message-----
> From: Francois Visagie [mailto:francois.visagie at gmail.com]
> Sent: 23 August 2013 15:53
> To: 'FFmpeg user questions'
> Subject: RE: [FFmpeg-user] Some inputs make MP4 output sync incompatible
> with other applications
> 
> > > Out of sync for other applications:
> > >
> > > ffmpeg -i VTS_01_1.cut.VOB -filter:a aformat=channel_layouts=stereo
> > > -c:a libvo_aacenc -c:v libx264 -preset ultrafast -b:v 1000000
> > > zzz.mp4
> > >
> > > In sync for other applications:
> > >
> > > ffmpeg -i VTS_01_1.cut.VOB -filter:a aformat=channel_layouts=stereo
> > > -c:a libvo_aacenc -c:v libx264 -preset ultrafast -b:v 1000000
> > > zzz.mpg
> >
> > (Difficult to see a difference.)
> 
> There's a very clear difference in output.
> 
> > There have been reports that libvo_aacenc produces worse results than
> > the native encoder and should not be used.
> 
> By native do you mean the "experimental aac" codec below (from the
> Zeranoe builds)? I.e. using it requires '-strict -2'?

With '-strict -2 -c:a aac' instead of '-c:a libvo_aacenc', i.e. with

ffmpeg -i VTS_01_1.cut.VOB -filter:a aformat=channel_layouts=stereo -strict
-2 -c:a aac -c:v libx264 -preset ultrafast -b:v 1000000 zzzaac.mp4

timing results are the same as before. E.g. at around 52s into the sample
clip the words "to go" appear around 650 ms before the utterance on video.