[MPlayer-dev-eng] [PATCH] -oac copy with ac3 sound and lavf ts demuxer issues (Was: Re: [MEncoder-users] Video/Audio asynchronous)

Michael Niedermayer michaelni at gmx.at
Sat Feb 24 19:14:56 CET 2007


On Sat, Feb 24, 2007 at 06:41:42PM +0100, Matthias Hopf wrote:
> > > > note dwSampleSize MUST be 0 for VBR streams
> > > 
> > > I think I understand *that* part of avi...
> > > 
> > >          - If the dwSampleSize is 0, then it's VBR stream, so its bitrate
> > >          isn't constant. It means that 1 chunk stores 1 sample, and
> > >          dwRate/dwScale gives the chunks/sec value.
> > > 
> > > So how can I check the chunk size? One AC3 frame is 1152 in this
> > > case (384kbit/s), but where is this stored?
> > 
> > well you can easily find the size in bytes of each chunk, just search for 
> > 00dc the size is the 32bit int afterwards after that comes the next chunk
> No, I mean in which field in codec or sh_aud I can find this value.
> I have the AC3 spec at hand and have already written my own
> demultiplexer ;)

well i dont know, id look at the avi muxer code to see what it gets and
then backtrace that ... :)

> > also the chunk sizes and their content MUST match from what lavf gives
> > mencoder and what mencoder stored in the stream copy case with vbr, this
> > is what i suspect will not be true and likely what causes the problems
> > 
> > mencoder is full of hacks to workaround its own bugs sadly they break
> > fatally if correct data is feeded to it ...
> I guess so. Unfortunately I don't know how it should behave in the first
> place, so I've got difficulties to fix this correctly.

well i dont know that either (the problem is not the avi spec but rather
what will be accepted by the microshitty players), maybe you could try
ffmpeg or mencoder + lavf muxer and test if the output works with whatever
player you have if it does work then the lavf rate/scale is likely correct
and the issues are somewhere else (maybe in the avi muxer in mencoder)

Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

I am the wisest man alive, for I know one thing, and that is that I know
nothing. -- Socrates
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: application/pgp-signature
Size: 189 bytes
Desc: not available
URL: <http://lists.mplayerhq.hu/pipermail/mplayer-dev-eng/attachments/20070224/de4ab7a5/attachment.pgp>

More information about the MPlayer-dev-eng mailing list