[FFmpeg-devel] H264 video and AVPacket::duration

Michael Niedermayer michaelni at gmx.at
Wed Dec 4 05:14:01 CET 2013


On Tue, Dec 03, 2013 at 11:39:49PM +0400, Michael Doilnitsyn wrote:
> On Wed, Nov 20, 2013 at 2:35 PM, Michael Niedermayer <michaelni at gmx.at  <http://ffmpeg.org/mailman/listinfo/ffmpeg-devel>>wrote:
> 
> >/  On Wed, Nov 20, 2013 at 11:02:10AM -0800, Alex Sukhanov wrote:
> />/  > On Tue, Nov 19, 2013 at 5:58 PM, Michael Niedermayer <michaelni at gmx.at  <http://ffmpeg.org/mailman/listinfo/ffmpeg-devel>
> />/  >wrote:
> />/  >
> />/  > > On Tue, Nov 19, 2013 at 02:27:55PM -0800, Alex Sukhanov wrote:
> />/  > > > Hi Michael and ffmpeg-devel,
> />/  > > >
> />/  > > > I recently found that for H264 video ffmpeg demuxers and ffprobe
> />/  doesn't
> />/  > > > set AVPacket::duration field.
> />/  > > > This is typical ffprobe output for H264 video packed into FLV
> />/  container:
> />/  > > >
> />/  > > >
> />/  > >
> />/  packet|codec_type=audio|stream_index=1|pts=0|pts_time=0.000000|dts=0|dts_time=0.000000|duration=23|duration_time=0.023000|convergence_duration=N/A|convergence_duration_time=N/A|size=9|pos=103|flags=K_
> />/  > > >
> />/  > >
> />/  *packet|codec_type=video|stream_index=0|pts=0|pts_time=0.000000|dts=0|dts_time=0.000000|duration=N/A|duration_time=N/A|convergence_duration=N/A|convergence_duration_time=N/A|size=4188|pos=132|flags=K_*
> />/  > > >
> />/  > >
> />/  packet|codec_type=audio|stream_index=1|pts=23|pts_time=0.023000|dts=23|dts_time=0.023000|duration=23|duration_time=0.023000|convergence_duration=N/A|convergence_duration_time=N/A|size=9|pos=4337|flags=K_
> />/  > > >
> />/  > >
> />/  *packet|codec_type=video|stream_index=0|pts=37|pts_time=0.037000|dts=37|dts_time=0.037000|duration=N/A|duration_time=N/A|convergence_duration=N/A|convergence_duration_time=N/A|size=43|pos=4366|flags=__*
> />/  > > >
> />/  > >
> />/  packet|codec_type=audio|stream_index=1|pts=46|pts_time=0.046000|dts=46|dts_time=0.046000|duration=23|duration_time=0.023000|convergence_duration=N/A|convergence_duration_time=N/A|size=9|pos=4426|flags=K_
> />/  > > >
> />/  > >
> />/  packet|codec_type=audio|stream_index=1|pts=70|pts_time=0.070000|dts=70|dts_time=0.070000|duration=23|duration_time=0.023000|convergence_duration=N/A|convergence_duration_time=N/A|size=56|pos=4452|flags=K_
> />/  > > >
> />/  > >
> />/  *packet|codec_type=video|stream_index=0|pts=73|pts_time=0.073000|dts=73|dts_time=0.073000|duration=N/A|duration_time=N/A|convergence_duration=N/A|convergence_duration_time=N/A|size=26|pos=4528|flags=__*
> />/  > > >
> />/  > >
> />/  packet|codec_type=audio|stream_index=1|pts=93|pts_time=0.093000|dts=93|dts_time=0.093000|duration=23|duration_time=0.023000|convergence_duration=N/A|convergence_duration_time=N/A|size=607|pos=4571|flags=K_
> />/  > > >
> />/  > >
> />/  *packet|codec_type=video|stream_index=0|pts=110|pts_time=0.110000|dts=110|dts_time=0.110000|duration=N/A|duration_time=N/A|convergence_duration=N/A|convergence_duration_time=N/A|size=31|pos=5198|flags=__*
> />/  > > >
> />/  > >
> />/  packet|codec_type=audio|stream_index=1|pts=116|pts_time=0.116000|dts=116|dts_time=0.116000|duration=23|duration_time=0.023000|convergence_duration=N/A|convergence_duration_time=N/A|size=599|pos=5246|flags=K_
> />/  > > >
> />/  > >
> />/  packet|codec_type=audio|stream_index=1|pts=139|pts_time=0.139000|dts=139|dts_time=0.139000|duration=23|duration_time=0.023000|convergence_duration=N/A|convergence_duration_time=N/A|size=611|pos=5862|flags=K_
> />/  > > >
> />/  > > >
> />/  > > > I found following patch, which may be related:
> />/  > > >
> />/  > >
> />/  http://git.videolan.org/?p=ffmpeg.git;a=commit;h=497431a5b645ffc39cf3acbd333c9ff0f3031adb
> />/  > > > I understand the problem with interlaced video  which you fixed in
> />/  this
> />/  > > > patch, but I wanted to ask you If it's possible to move back
> />/  calculation
> />/  > > of
> />/  > > > AVPacket::duration for codecs which support Interlace?
> />/  > > >
> />/  > > > I would like to solve my problem and rollback aforementioned patch,
> />/  but
> />/  > > > before that I wanted to check with you and probably encourage some
> />/  > > > discussion.
> />/  > > > What do you think? Should I elaborate a fix in different way?
> />/  > >
> />/  > > if you have a file with mixed interlaced and progressive packets
> />/  > > does reverting the commit produce correct durations?
> />/  > > what if a parser is initialized ?
> />/  > >
> />/  > > also can you share the/a file that is affected (its always useful
> />/  > > if everyone can look at the same data insteda of everyone using a
> />/  > > different file)
> />/  > >
> />/  > > [...]
> />/  > > --
> />/  > > Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB
> />/  > >
> />/  > > it is not once nor twice but times without number that the same ideas
> />/  make
> />/  > > their appearance in the world. -- Aristotle
> />/  > >
> />/  > > _______________________________________________
> />/  > > ffmpeg-devel mailing list
> />/  > >ffmpeg-devel at ffmpeg.org  <http://ffmpeg.org/mailman/listinfo/ffmpeg-devel>
> />/  > >http://ffmpeg.org/mailman/listinfo/ffmpeg-devel
> />/  > >
> />/  > > Hi,
> />/  >
> />/  > I was told that I can share file only with Michael. File sent directly to
> />/  > him. Sorry that I can not share it with everyone.
> />/  > I had some time yesterday to study FFmpeg version which we use currently
> />/  > (It's a few years old), and I found that we modified our FFmpeg and moved
> />/  > AVPacket::duration computation back. Now we are updating FFmpeg and we
> />/  > faced with this problem again. As long as we computed AVPacket::duration
> />/  > all the time, looks like it's safe to rollback
> />/  >
> />/  http://git.videolan.org/?p=ffmpeg.git;a=commit;h=497431a5b645ffc39cf3acbd333c9ff0f3031adb
> />/
> />/  what about PAFF
> />/  PAFF means mixed fields and frames
> />/  the code sets duration to a constant, how is a constant going to
> />/  equal 2 different durations ?
> />/  also a packet can contain a frame that is supposed to be displayed
> />/  for 3 fields time
> />/  i must be missing something, as to me it looks like this works just
> />/  because such cases are rare
> />/
> />/
> />/  [...]
> />/  --
> />/  Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB
> />/
> />/  When the tyrant has disposed of foreign enemies by conquest or treaty, and
> />/  there is nothing more to fear from them, then he is always stirring up
> />/  some war or other, in order that the people may require a leader. -- Plato
> />/
> />/  _______________________________________________
> />/  ffmpeg-devel mailing list
> />/  ffmpeg-devel at ffmpeg.org  <http://ffmpeg.org/mailman/listinfo/ffmpeg-devel>
> />/  http://ffmpeg.org/mailman/listinfo/ffmpeg-devel
> />/
> />/
> /
> /     /Thu Nov 21 01:07:36 CET 2013/  /
> /*Alex Sukhanov*  alx.sukhanov at gmail.com  <mailto:ffmpeg-devel%40ffmpeg.org?Subject=Re%3A%20%5BFFmpeg-devel%5D%20H264%20video%20and%20AVPacket%3A%3Aduration&In-Reply-To=%3CCAHufB%2BVi61XqK%3Di_FuNNVFrQL3MZUa2opDWZW2Z7jua9aOVmWw%40mail.gmail.com%3E>/  wrote:
> >/  /Michael,
> >/  /I think you are right: our old FFmpeg works just because it's a rare case.
> >/  /In worst scenario I can copy duration computation from old ffmpeg to new
> >/  /one in our private repository, but as I said, I would be happy to elaborate
> >/  /some universal solution here in public repository, which would fix issue
> >/  /1756 and set duration for each frame packet at the same time.
> >/  /What if FFmpeg could distinguish fields and frames and reset packet
> >/  /duration only if it's a field? That would work for me, because I don't deal
> >/  /with fields at all. What do you think?
> >/  /I'm not familiar with Ffmpeg yet, so I also would like to ask if it's
> >/  /possible and how better to do that?
> 
> Hi Michael,
> 
> Alex Sukhanov kindly asked me to help with this issue cause I have essential video experience (participating in
> Vanguard H.264 codec development).
> 
> Since we are talking about ff_compute_frame_duration() function, I think it is safe to suppose we should
> calculate exactly/frame/  duration (not/field/  or/slice/  or something else).

ff_compute_frame_duration() is used to set AVPacket.duration
if the AVPacket doesnt contain a frame then setting it to the frame
duration will not be correct

maybe ff_compute_frame_duration() should be renamed

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

Freedom in capitalist society always remains about the same as it was in
ancient Greek republics: Freedom for slave owners. -- Vladimir Lenin
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