[FFmpeg-trac] #735(FFmpeg:new): Incorrect DTS sync in OGG codec

[FFmpeg]

#735: Incorrect DTS sync in OGG codec
-------------------------------------+-------------------------------------
             Reporter:  zvi          |                     Type:  defect
               Status:  new          |                 Priority:  important
            Component:  FFmpeg       |                  Version:  0.8.7
             Keywords:  ffmpeg ogv   |               Blocked By:
  sync                               |  Reproduced by developer:  0
             Blocking:               |
Analyzed by developer:  0            |
-------------------------------------+-------------------------------------
 Hi,

 I've noticed incorrect DTS values in OGG encoded audio streams (as part of
 an OGV file). This happened with a ffmpeg-0.8.7

 These are the steps I have taken to reproduce it.

 1. Convert a valid and working MP4 (h264/aac) as confirmed by ffprobe to
 an OGV file using:
 {{{
 ffmpeg -y -i vid.mp4 -vcodec libtheora -b 1000k -acodec libvorbis -ab 192k
 vid.ogv
 }}}

 2. Probing the "vid.ogv" file using ffprobe shows that during audio
 frames, the "pos" doesn't change - even for the video frames it seems to
 repeat ~10 times. See simplified format dump below.

 3. While "vid.ogv" plays ok in VLC, after doing a zero transformation on
 it, it breaks completely and audio goes totally out of sync (video plays
 ok).
 {{{
 ffmpeg -y -i vid.ogv -vcodec copy -acodec copy new_vid.ogv
 }}}

 4. The '''new_vid.ogv''' file no longer plays correctly. Putting some
 debug prints in ffmpeg.c:output_packet(...) I see the following.[[BR]]
 A sequence of consecutive audio frames gets the correct DTS values. From 0
 to 10941 in steps of ~64.[[BR]]
 Then there is a sequence of consecutive video frames. For video the DTS
 always appears to be correct.[[BR]]
 The next sequence of consecutive audio frames now starts at 154048 -
 instead of being at ~11005[[BR]]

 Also notice the negative '''duration''' value.

 {{{
 Input #0, ogg, from 'new_vid.ogv':
   Duration: -513359:-56:-35.41, start: 0.000000, bitrate: N/A
     Stream #0.0: Video: theora, yuv420p, 960x540 [PAR 1:1 DAR 16:9], 29.97
 tbr, 29.97 tbn, 29.97 tbc
     Stream #0.1: Audio: vorbis, 48000 Hz, stereo, s16, 192 kb/s
 }}}

 If you need any additional information, please let me know.

 Thanks,
    TR

 {{{
 type=video index=0 dts=0 dts_time=0.000000  [100/2997] duration=1 pos=7414
 type=video index=0 dts=1 dts_time=0.033367  [100/2997] duration=1 pos=7414
 type=video index=0 dts=2 dts_time=0.066733  [100/2997] duration=1 pos=7414
 type=video index=0 dts=3 dts_time=0.100100  [100/2997] duration=1 pos=7414
 ...
 type=video index=0 dts=83 dts_time=2.769436  [100/2997] duration=1
 pos=260411
 type=audio index=1 dts=0 dts_time=0.000000  [1/48000] duration=0
 pos=323479
 type=audio index=1 dts=N/A dts_time=N/A [1/48000] duration=0 pos=323479
 type=audio index=1 dts=N/A dts_time=N/A [1/48000] duration=0 pos=323479
 ...
 type=audio index=1 dts=N/A dts_time=N/A [1/48000] duration=0 pos=323479
 type=audio index=1 dts=N/A dts_time=N/A [1/48000] duration=0 pos=323479
 type=video index=0 dts=84 dts_time=2.802803  [100/2997] duration=1
 pos=260411
 type=video index=0 dts=85 dts_time=2.836170  [100/2997] duration=1
 pos=355961
 type=video index=0 dts=86 dts_time=2.869536  [100/2997] duration=1
 pos=355961
 type=video index=0 dts=87 dts_time=2.902903  [100/2997] duration=1
 pos=355961
 type=video index=0 dts=88 dts_time=2.936270  [100/2997] duration=1
 pos=355961
 type=video index=0 dts=89 dts_time=2.969636  [100/2997] duration=1
 pos=355961
 type=video index=0 dts=90 dts_time=3.003003  [100/2997] duration=1
 pos=355961
 type=video index=0 dts=91 dts_time=3.036370  [100/2997] duration=1
 pos=355961
 type=video index=0 dts=92 dts_time=3.069736  [100/2997] duration=1
 pos=355961
 type=video index=0 dts=93 dts_time=3.103103  [100/2997] duration=1
 pos=355961
 type=video index=0 dts=94 dts_time=3.136470  [100/2997] duration=1
 pos=355961
 type=video index=0 dts=95 dts_time=3.169837  [100/2997] duration=1
 pos=355961
 type=video index=0 dts=96 dts_time=3.203203  [100/2997] duration=1
 pos=355961
 type=video index=0 dts=97 dts_time=3.236570  [100/2997] duration=1
 pos=355961
 type=video index=0 dts=98 dts_time=3.269937  [100/2997] duration=1
 pos=419330
 type=video index=0 dts=99 dts_time=3.303303  [100/2997] duration=1
 pos=419330
 type=video index=0 dts=100 dts_time=3.336670  [100/2997] duration=1
 pos=419330
 type=video index=0 dts=101 dts_time=3.370037  [100/2997] duration=1
 pos=419330
 type=video index=0 dts=102 dts_time=3.403403  [100/2997] duration=1
 pos=419330
 type=video index=0 dts=103 dts_time=3.436770  [100/2997] duration=1
 pos=419330
 type=video index=0 dts=104 dts_time=3.470137  [100/2997] duration=1
 pos=419330
 type=video index=0 dts=105 dts_time=3.503504  [100/2997] duration=1
 pos=419330
 ...
 type=video index=0 dts=148 dts_time=4.938272  [100/2997] duration=1
 pos=545023
 type=audio index=1 dts=154048 dts_time=3.209333  [1/48000] duration=0
 pos=608173
 type=audio index=1 dts=N/A dts_time=N/A [1/48000] duration=0 pos=608173
 type=audio index=1 dts=N/A dts_time=N/A [1/48000] duration=0 pos=608173
 }}}

-- 
Ticket URL: <https://ffmpeg.org/trac/ffmpeg/ticket/735>
FFmpeg <http://ffmpeg.org>
FFmpeg issue tracker