[FFmpeg-devel] [PATCH 2/2] Enable parsing in FLV container

[Michael Niedermayer]

On Wed, Dec 11, 2013 at 09:40:49PM -0800, Alex Sukhanov wrote:
> On Wed, Dec 11, 2013 at 7:34 PM, Michael Niedermayer <michaelni at gmx.at>wrote:
> 
> > On Wed, Dec 11, 2013 at 05:49:07PM -0800, Alex Sukhanov wrote:
> > > ---
> > >  libavformat/flvdec.c | 1 +
> > >  1 file changed, 1 insertion(+)
> > >
> > > diff --git a/libavformat/flvdec.c b/libavformat/flvdec.c
> > > index 1024001..b19db0e 100644
> > > --- a/libavformat/flvdec.c
> > > +++ b/libavformat/flvdec.c
> > > @@ -256,6 +256,7 @@ static int flv_set_video_codec(AVFormatContext *s,
> > AVStream *vstream,
> > >          return 1;     // 1 byte body size adjustment for
> > flv_read_packet()
> > >      case FLV_CODECID_H264:
> > >          vcodec->codec_id = AV_CODEC_ID_H264;
> > > +        vstream->need_parsing = AVSTREAM_PARSE_FULL;
> >
> > full parsing needs some extra parsing and spliting over the data
> > and could cause some slowdown
> >
> >
> > >          return 3;     // not 4, reading packet type will consume one
> > byte
> > >      case FLV_CODECID_MPEG4:
> > >          vcodec->codec_id = AV_CODEC_ID_MPEG4;
> > > --
> > > 1.8.5.1
> > >
> > > _______________________________________________
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> > >
> >
> > --
> > Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB
> >
> > Concerning the gods, I have no means of knowing whether they exist or not
> > or of what sort they may be, because of the obscurity of the subject, and
> > the brevity of human life -- Protagoras
> >
> > _______________________________________________
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> > ffmpeg-devel at ffmpeg.org
> > http://ffmpeg.org/mailman/listinfo/ffmpeg-devel
> >
> >
> 
> Hi Michael,
> 
> This is how it's implemented in MPEG2TS Demuxer:
> http://git.videolan.org/?p=ffmpeg.git;a=blob;f=libavformat/mpegts.c;h=d67c63a4de20480d351c7d089467e923241cdefa;hb=HEAD#l688

mpeg ts needs a parser as the bytestream doesnt come packaged in AUs
but can be in random pieces of bytes unrelated to AU boundaries


> Let me know please how you would like to process here.

its hard to say as most questions are unawnsered
is PAFF allowed in flv ?
is the duration from the codec bitstream matching the container
duration ?
does AVSTREAM_PARSE_HEADERS work too ?
does the demuxer have enough information to set the durations ?

i suspect setting the duration from the demuxer is the best solution
if that is easily possible. If not then AVSTREAM_PARSE_HEADERS could
be tried.
full parsing causes a slowdown and the durations are generally not
needed by user applications so some means to allow a user app to
avoid this extra step would then make sense. That is allow a user
app to inform avformat about what information it needs, like duration
or r_frame_rate, ...


[...]

-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

If a bugfix only changes things apparently unrelated to the bug with no
further explanation, that is a good sign that the bugfix is wrong.
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