[FFmpeg-trac] #9843(avformat:new): Matroska muxer never returns avio markers

[FFmpeg]

#9843: Matroska muxer never returns avio markers
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             Reporter:  Sesse     |                     Type:  defect
               Status:  new       |                 Priority:  normal
            Component:  avformat  |                  Version:  git-master
             Keywords:            |               Blocked By:
             Blocking:            |  Reproduced by developer:  0
Analyzed by developer:  0         |
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 The Matroska/WebM muxer has this code to send avio markers on sync points:

       if (!mkv->cluster_pos)
           avio_write_marker(s->pb,
                             av_rescale_q(pkt->dts,
 s->streams[pkt->stream_index]->time_base, AV_TIME_BASE_Q),
                             keyframe && (mkv->have_video ? codec_type ==
 AVMEDIA_TYPE_VIDEO : 1) ? AVIO_DATA_MARKER_SYNC_POINT :
 AVIO_DATA_MARKER_BOUNDARY_POINT);

 This was merged into FFmpeg in


 commit dc62016c4b77a48284b24ad927eb68035b133925
 Merge: a86fe0d738 71852a1ba8
 Author: Matthieu Bouron <matthieu.bouron at stupeflix.com>
 Date:   Thu Jun 23 17:57:34 2016 +0200

     Merge commit '71852a1ba89abc8749e309d9d662c49d47e19531'

     * commit '71852a1ba89abc8749e309d9d662c49d47e19531':
       matroskaenc: Provide output bytestream markers

     Merged-by: Matthieu Bouron <matthieu.bouron at stupeflix.com>

 However, it didn't take into account that this patch was already in the
 tree:

 commit bda5b6627a558cf10c4d09eeff264289a1370cc1
 Author: Aaron Colwell <acolwell at chromium.org>
 Date:   Wed Mar 14 21:40:29 2012 +0100

     matroskaenc: change cluster_pos to use -1 as the "I'm not currently
 working on a cluster" signal instead of 0.

     This avoids problems
     where avio_tell() returns 0. I've updated all the checks against
     cluster_pos

     Signed-off-by: Michael Niedermayer <michaelni at gmx.at>

 So now mkv->cluster_pos cannot be 0, and the markers are never sent. It
 seems this functionality has been broken in FFmpeg since it was merged.

 Changing the test to (mkv->cluster_pos == -1) instead seems to fix the
 issue, but someone should verify that this was indeed the intention.
-- 
Ticket URL: <https://trac.ffmpeg.org/ticket/9843>
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