[MPlayer-users] Re: [MEncoder] Synchonization lost when using Vorbis in a OGM

[Jonathan Rogers]

Rodolfo J. Quesada wrote:
> [Automatic answer: RTFM (read DOCS, FAQ), also read DOCS/bugreports.html]
> Hi,
> 
> This is my first post to this list... As I had been looking for a long 
> time how to deal with a problem I got recently...
> 
> I'm trying to compress some VOBs copied with vobcopy, and after that, 
> dump the audio, convert it to Vorbis, and mux it all, with ogmmerge to 
> get a nice OGM.
> 
> The problem is, that those VOBs after starting mencoder, keeps saying 
> that there was duplicate frames, enters and leaves telecine mode, it 
> jumps from 23.976 to 29.970 in those changes... All of that things are 
> expected by the nature of the DVD, when I got to the final AVI, with an 
> AC3 audio track (-oac copy), the A-V sync is always around 0.000, with a 
> few tens of milliseconds changes... That's still fine...
> 
> Then I dump the PCM audio...
> 
> cat *.VOB | mplayer -vc null -vo null -ao pcm -aofile audio.wav
> 
> And I get a pretty big PCM file... Then I encode it...
> 
> oggenc -q0 audio.wav
> 
> And got an audio.ogg file...
> 
> Then, I merge it...
> 
> ogmmerge -A video.avi audio.ogg -o pelicula.ogm
> 
> And when I play it with MPlayer, the sync ratio jumps up to 15 seconds, 
> in some scenes where the telecine mode was enabled... It gets 
> desynchronized all the way, in the plain old 29.970fps scenes, the audio 
> is synced, but not in the 23.976 ones... I tried it in Windows Media 
> Player 6.4, and those scenes not synchonized get blurred or stoped, and 
> follows the audio synchronizations nicely, but the video quality is not 
> appealing at all... Pretty ugly in fact...
> 
> So, the question, somebody has faced this problem before? It can be 
> solved?... I really love OGM... The audio is so sweet, even at a -q0 
> ratio...

I have a very similar problem. I transcoded a movie from DVD to MPEG-4 
which has many cuts between NTSC interlaced video at 29.97 and telecined 
film at 23.976. Since there is 29.97 fps video in there, I encoded to 
29.97 and used pp=lb.

When I play the AVI containing the encoded video and PCM audio with 
mplayer, the sync is good. However, when I play the OGM produced with 
the Vorbis audio and ogmmerge, the sync is horrible. The A-V delta gets 
up to a second or two by mplayer's admission and according to my eyes 
and ears.

In particular, mplayer starts getting out of sync when the movie cuts to 
an originally telecined segment. It somewhat regains sync when the movie 
cuts back to something that was originally NTSC. During film segments, 
mplayer's "A-V" value will sometimes jump from less than one second to 
greater than one. If I seek forward, then back to the same spot, sync is 
usually restored.

Now, it's time for the kicker. When I play the exact same OGM with Xine, 
there are no sync problems. Based on my previous experience with 
mplayer's flakiness in seeking and sync of OGM movies and this mess, I 
tend to think this is a bug in mplayer. It could be a bug in ogmmerge, 
but if so, Xine is somehow working around it.

Jonathan Rogers