[FFmpeg-trac] #6251(undetermined:new): copyts fails badly for negative start time

[FFmpeg]

#6251: copyts fails badly for negative start time
-------------------------------------+-------------------------------------
               Reporter:  cehoyos    |                  Owner:
                   Type:  defect     |                 Status:  new
               Priority:  normal     |              Component:
                Version:  git-       |  undetermined
  master                             |               Keywords:  mpegts dts
             Blocked By:             |               Blocking:
Reproduced by developer:  0          |  Analyzed by developer:  0
-------------------------------------+-------------------------------------
 http://ffmpeg.org/pipermail/ffmpeg-user/2017-March/035579.html
 A user provided an mpegts sample with negative start time that produces
 bad output file if audio is copied and video transcoded.
 {{{
 $ ffmpeg -copyts -i 63a2061a-e871-438b-baf3-a05a1ff7a7aa_000000977_cut.ts
 -acodec copy -qscale 2 -mbd 2 out.ts
 ffmpeg version N-84292-gb7cc4eb Copyright (c) 2000-2017 the FFmpeg
 developers
   built with gcc 4.7 (SUSE Linux)
   configuration: --enable-gpl
   libavutil      55. 50.100 / 55. 50.100
   libavcodec     57. 83.100 / 57. 83.100
   libavformat    57. 66.104 / 57. 66.104
   libavdevice    57.  3.100 / 57.  3.100
   libavfilter     6. 77.100 /  6. 77.100
   libswscale      4.  3.101 /  4.  3.101
   libswresample   2.  4.100 /  2.  4.100
   libpostproc    54.  2.100 / 54.  2.100
 Input #0, mpegts, from '63a2061a-e871-438b-
 baf3-a05a1ff7a7aa_000000977_cut.ts':
   Duration: 00:00:04.20, start: -58.427689, bitrate: 4871 kb/s
   Program 1
     Stream #0:0[0x1e4]: Data: timed_id3 (ID3  / 0x20334449)
     Stream #0:1[0x1e1]: Video: h264 (Main) ([27][0][0][0] / 0x001B),
 yuv420p(progressive), 1280x720 [SAR 1:1 DAR 16:9], Closed Captions, 29.97
 fps, 29.97 tbr, 90k tbn, 59.94 tbc
     Stream #0:2[0x1e2]: Audio: aac (LC) ([15][0][0][0] / 0x000F), 48000
 Hz, stereo, fltp, 117 kb/s
 Please use -q:a or -q:v, -qscale is ambiguous
 Stream mapping:
   Stream #0:1 -> #0:0 (h264 (native) -> mpeg2video (native))
   Stream #0:2 -> #0:1 (copy)
 Press [q] to stop, [?] for help
 Output #0, mpegts, to 'out.ts':
   Metadata:
     encoder         : Lavf57.66.104
     Stream #0:0: Video: mpeg2video (Main), yuv420p, 1280x720 [SAR 1:1 DAR
 16:9], q=2-31, 200 kb/s, 29.97 fps, 90k tbn, 29.97 tbc
     Metadata:
       encoder         : Lavc57.83.100 mpeg2video
     Side data:
       cpb: bitrate max/min/avg: 0/0/200000 buffer size: 0 vbv_delay: -1
     Stream #0:1: Audio: aac (LC) ([15][0][0][0] / 0x000F), 48000 Hz,
 stereo, fltp, 117 kb/s
 [h264 @ 0x34474e0] error while decoding MB 57 20, bytestream -17
 [h264 @ 0x34474e0] concealing 1992 DC, 1992 AC, 1992 MV errors in P frame
 frame=    0 fps=0.0 q=0.0 Lsize=      73kB time=00:00:00.00 bitrate=N/A
 dup=0 drop=122 speed=   0x
 video:0kB audio:65kB subtitle:0kB other streams:0kB global headers:0kB
 muxing overhead: 11.009791%
 }}}
 Output should have 122 video frames.
 A similar sample with non-negative start time works fine, the command line
 without {{{-copyts}}} also works fine.

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Ticket URL: <https://trac.ffmpeg.org/ticket/6251>
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