[FFmpeg-devel] [PATCH] ffmpeg: remove unused sync_ist attribute from OutputStream

Michael Niedermayer michaelni at gmx.at
Sun Mar 25 19:35:45 CEST 2012

On Sun, Mar 25, 2012 at 01:22:50PM +0200, Wolfram Gloger wrote:
> > On Wed, Mar 21, 2012 at 02:23:44PM +0100, Matthieu Bouron wrote:
> >> Hi,
> >> 
> >> This patch remove the sync_ist attribute from OutputStream.
> >> sync_ist is not used anymore in ffmpeg.c. Usage was removed by commit:
> >> d97fa416d62fe00a69e5be947d7c51b71982dd12.
> Michael Niedermayer <michaelni at gmx.at> writes:
> > theres more dead code resulting from this, up to the parsing of the
> > sync streams. I think it would be better to fix the code unless it
> > has no use case
> >
> > maybe wolfram could comment on the usecase part? he was the author of
> > this IIRC
> Good memory :)..  The above commit actually removed the 'sync against an
> arbitrary input stream' feature.  If you want to keep it this way, you
> might as well also remove the specification of the input sync stream
> index.
> But, I still consider this feature necessary.
> Example: input is mpeg with one video and one audio stream, with precise
> timestamps for every packet.  Output is avi (no timestamps) and you want
> to reencode video but copy audio (therefore no -async option possible).
> If you don't use the 'sync the video stream against the audio stream'
> (which used to be the default in ffmpeg way back before May 2005),
> you can then get the audio stream drifting further and further away,
> because the AVI player only has the decoded duration of the audio frames
> available, and _not_ the precise timestamps the audio frames had in the
> original input.
> I would suggest to fix the above commit if possible so as to retain
> the feature.  Have not looked at that yet; do you agree?

i agree

thanks for the explanation


Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

The worst form of inequality is to try to make unequal things equal.
-- Aristotle
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