[FFmpeg-devel] [PATCH] Set AVStream duration in several demuxers

[Michael Niedermayer]

On Wed, Jan 20, 2010 at 06:02:48PM +0100, Aurelien Jacobs wrote:
> On Mon, Jan 18, 2010 at 10:43:06PM -0500, David Conrad wrote:
> > Hi,
> > 
> > Several demuxers set duration and start_time in AVFormatContext, despite the comment to never set them directly. This sets them in AVStream instead, fixing "Estimating duration from bitrate, this may be inaccurate" messages.
> > 
> > iavs/ivas AVIs still set AVFormatContext duration, I didn't find a sample to test.
> > 
> 
> > commit d1ec4470be04fba3ff10fbecd455a14ab322d14e
> > Author: David Conrad <lessen42 at gmail.com>
> > Date:   Mon Jan 18 22:33:25 2010 -0500
> > 
> >     Set start_time and duration in AVStream not AVFormatContext.
> >     The latter is deduced from the former.
> > 
> > diff --git a/libavformat/matroskadec.c b/libavformat/matroskadec.c
> > index 59dc166..7fcef04 100644
> > --- a/libavformat/matroskadec.c
> > +++ b/libavformat/matroskadec.c
> > @@ -1151,9 +1151,6 @@ static int matroska_read_header(AVFormatContext *s, AVFormatParameters *ap)
> >          return -1;
> >      matroska_execute_seekhead(matroska);
> >  
> > -    if (matroska->duration)
> > -        matroska->ctx->duration = matroska->duration * matroska->time_scale
> > -                                  * 1000 / AV_TIME_BASE;
> >      av_metadata_set(&s->metadata, "title", matroska->title);
> >  
> >      tracks = matroska->tracks.elem;
> > @@ -1338,6 +1335,9 @@ static int matroska_read_header(AVFormatContext *s, AVFormatParameters *ap)
> >              track->time_scale = 1.0;
> >          av_set_pts_info(st, 64, matroska->time_scale*track->time_scale, 1000*1000*1000); /* 64 bit pts in ns */
> >  
> > +        if (matroska->duration)
> > +            st->duration = matroska->duration;
> > +
> >          st->codec->codec_id = codec_id;
> >          st->start_time = 0;
> >          if (strcmp(track->language, "und"))
> 
> Strictly speeking this don't really seem correct. The segment duration
> stored in matroska file is (IIUC) the total duration of the segment.
> IOW it is the duration of the longest track. So using this same duration
> for every streams is not excatly correct. But provided the current avformat
> API, it seems to be the best we can do :-(
> 
> Maybe it would be better to improve the avformat API instead, to allow
> demuxers to write directly AVFormatContext.duration when they only know
> the total duration and not individual streams duration.
> I guess this (untested) patch would fix your original issue. It would
> also require an update of AVFormatContext.duration documentation.

iam not against this patch but it would have to be tested

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

There will always be a question for which you do not know the correct awnser.
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