[FFmpeg-devel] [PATCH] avcodec/utils: initialize delay in avcodec_parameters_to_context()

[Michael Niedermayer]

On Sat, Jun 04, 2016 at 01:30:20PM -0400, Ronald S. Bultje wrote:
> Hi,
> 
> On Sat, Jun 4, 2016 at 1:09 PM, Michael Niedermayer <michael at niedermayer.cc>
> wrote:
> 
> > On Sat, Jun 04, 2016 at 09:16:09AM -0400, Ronald S. Bultje wrote:
> > > Hi,
> > >
> > > On Sat, Jun 4, 2016 at 7:27 AM, Michael Niedermayer
> > <michael at niedermayer.cc>
> > > wrote:
> > >
> > > > On Sat, Jun 04, 2016 at 12:15:50PM +0200, Hendrik Leppkes wrote:
> > > > > On Sat, Jun 4, 2016 at 12:09 PM, Michael Niedermayer
> > > > > <michael at niedermayer.cc> wrote:
> > > > > > On Sat, Jun 04, 2016 at 09:47:47AM +0200, Hendrik Leppkes wrote:
> > > > > >> On Sat, Jun 4, 2016 at 4:55 AM, Michael Niedermayer
> > > > > >> <michael at niedermayer.cc> wrote:
> > > > > >> > Fixes lost codec delayy
> > > > > >> > Should fix Ticket5509
> > > > > >> >
> > > > > >> > Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>
> > > > > >> > ---
> > > > > >> >  libavcodec/utils.c |    1 +
> > > > > >> >  1 file changed, 1 insertion(+)
> > > > > >> >
> > > > > >> > diff --git a/libavcodec/utils.c b/libavcodec/utils.c
> > > > > >> > index 7b99526..4016583 100644
> > > > > >> > --- a/libavcodec/utils.c
> > > > > >> > +++ b/libavcodec/utils.c
> > > > > >> > @@ -4157,6 +4157,7 @@ int
> > > > avcodec_parameters_to_context(AVCodecContext *codec,
> > > > > >> >          codec->sample_rate     = par->sample_rate;
> > > > > >> >          codec->block_align     = par->block_align;
> > > > > >> >          codec->frame_size      = par->frame_size;
> > > > > >> > +        codec->delay           =
> > > > > >> >          codec->initial_padding = par->initial_padding;
> > > > > >> >          codec->seek_preroll    = par->seek_preroll;
> > > > > >> >          break;
> > > > > >> > --
> > > > > >> > 1.7.9.5
> > > > > >> >
> > > > > >>
> > > > > >> Its probably fine to set it, but delay is not the correct field
> > for
> > > > > >> ffmpeg.c and/or whichever muxer is involved to be using then.
> > > > > >
> > > > > > delay must be set for the demuxer (required by API and used by
> > > > > > applications), avcodec_parameters_to_context()
> > > > > > has no knowledge about working on demuxer or muxer side
> > > > > > contexts unless i miss something. (i tried avctx->codec but its
> > never
> > > > > > set)
> > > > > > I can add a parameter to avcodec_parameters_to_context() that
> > > > > > indicates if its for the demuxer or muxer or add a
> > > > > > avcodec_parameters_to_context2() or a
> > > > > > avcodec_parameters_to_context_demuxer()
> > > > > > ff_parameters_to_context_demuxer()
> > > > > > do you agree to add such function ?
> > > > > > (iam asking as changes to AVCodecParameters API tend to receive
> > > > > >  a lot of opposition)
> > > > >
> > > > > Adding more weird API sounds silly, this patch is likely the better
> > > > option.
> > > >
> > > > applied
> > > >
> > > >
> > > > > Once ffmpeg.c is updated to use codecpar properly, this whole
> > > > > double-field issue goes away anyway.
> > > >
> > > > i dont think it does as the API requires delay to be set
> > >
> > >
> > > We can change API on the next major version bump.
> >
> > The field is not deprecated
> > we can mark the API as deprecated before the next version bump and
> > remove it on the following API bump at the earliest
> >
> > my oppinion was and is that maintaining long term API compatibility
> > is better than frequent API changes though
> 
> 
> Well, partially. We now have two fields that are set to the same codecpar
> value. The question is: is there ever a case where these two act
> meaningfully concurrent and have distinctly different meanings?
> 
> If not, we should deprecate one of them. I don't care which we deprecate.

AVCodecContext.delay has no replacement for video

for audio it is mutually exclusive with initial_padding as one is
decoding and one is encoding only

all based on the docs

AVCodecParameters has initial_padding and video_delay fields instead

[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Democracy is the form of government in which you can choose your dictator
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