[FFmpeg-devel] [PATCH] [RFC] avformat: use "genpts" option for output file.

[Michael Niedermayer]

On Tue, Nov 04, 2014 at 02:32:55PM +0100, Benoit Fouet wrote:
> Hi,
> 
> ----- Mail original -----
> > On Tue, Nov 04, 2014 at 01:15:02PM +0100, Benoit Fouet wrote:
> > > Hi,
> > > 
> > > ----- Mail original -----
> > > > On Mon, Nov 03, 2014 at 03:21:33PM +0100, Benoit Fouet wrote:
> > > > > When "-fflags +genpts" is used for output file, use dts as pts.
> > > > > 
> > > > > Signed-off-by: Benoit Fouet <benoit.fouet at free.fr>
> > > > > ---
> > > > >  libavformat/mux.c | 3 +++
> > > > >  1 file changed, 3 insertions(+)
> > > > > 
> > > > > diff --git a/libavformat/mux.c b/libavformat/mux.c
> > > > > index 5e45bd8..1d42451 100644
> > > > > --- a/libavformat/mux.c
> > > > > +++ b/libavformat/mux.c
> > > > > @@ -884,6 +884,9 @@ int
> > > > > av_interleaved_write_frame(AVFormatContext
> > > > > *s, AVPacket *pkt)
> > > > >              ret = AVERROR(EINVAL);
> > > > >              goto fail;
> > > > >          }
> > > > > +
> > > > > +        if (pkt->pts == AV_NOPTS_VALUE && s->flags &
> > > > > AVFMT_FLAG_GENPTS)
> > > > > +            pkt->pts = pkt->dts;
> > > > 
> > > > does this set pts to invalid value for h264 with b frames or
> > > > b pyramid ?
> > > > 
> > > 
> > > No.
> > 
> > how did you test this ?
> > can you show an example of b pyramid and the filled in PTS values
> > 
> 
> Oh... I only tested stream copy. And this is the only thing I want to fix. I should ensure this is only used for this case, right?
> I think this can mess things up if used with "real" transcoding...

no, you misunderstand i think


        consider
raw.h264 originally encoded with B pyramid
        IPBBBPBBB
PTS     ????????? <-- these are actually stored in the h264 one way
                      or another but not read
DTS     012345678

Correct (stream copy into file.ts, file.mkv and others)
        IPBBBPBBB
PTS     26435A879
DTS     012345678

what i suspect this patch creates:
PTS     012345678
DTS     012345678

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

Republics decline into democracies and democracies degenerate into
despotisms. -- Aristotle
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