[FFmpeg-trac] #5263(undetermined:new): Negative start times with segment recording rtsp stream

[FFmpeg]

#5263: Negative start times with segment recording rtsp stream
-------------------------------------+-------------------------------------
             Reporter:  peterpion    |                     Type:  defect
               Status:  new          |                 Priority:  normal
            Component:               |                  Version:
  undetermined                       |  unspecified
             Keywords:  segment      |               Blocked By:
  start time ffmpeg                  |  Reproduced by developer:  0
             Blocking:               |
Analyzed by developer:  0            |
-------------------------------------+-------------------------------------
 Summary of the bug:
 How to reproduce:
 {{{
 ffmpeg -i "rtsp://192.168.1.10:554/channel=1&stream=0.sdp" -vcodec copy -r
 10 -acodec aac -f segment -segment_time 900 -segment_atclocktime 1
 -reset_timestamps 1 -strftime 1 "/var/www/html/%y/%m/%d/cam1_%H%M%S.mp4"

 Output of ffprobe for recorded files:
 cam1_191637.mp4, Duration: 00:13:17.31, start: 0.000000, bitrate: 651 kb/s
 (beginning of recording)
 -cut-
 cam1_213000.mp4, Duration: 00:14:59.97, start: 0.000000, bitrate: 647 kb/s
 cam1_214500.mp4, Duration: 00:14:59.97, start: 0.000000, bitrate: 649 kb/s
 cam1_220000.mp4, Duration: 00:14:59.94, start: 0.000000, bitrate: 649 kb/s
 cam1_221504.mp4, Duration: 00:14:59.97, start: -4.324000, bitrate: 649
 kb/s
 cam1_223004.mp4, Duration: 00:14:59.97, start: -4.356000, bitrate: 652
 kb/s
 cam1_224504.mp4, Duration: 00:14:59.97, start: -4.388000, bitrate: 653
 kb/s
 cam1_230004.mp4, Duration: 00:14:59.97, start: -4.420000, bitrate: 653
 kb/s
 cam1_231504.mp4, Duration: 00:14:59.97, start: -4.452000, bitrate: 654
 kb/s
 cam1_233004.mp4, Duration: 00:14:59.97, start: -4.484000, bitrate: 654
 kb/s
 -cut- (2 days later after continuous recording)
 cam1_101503.mp4, Duration: 00:14:59.97, start: -174.188000, bitrate: 660
 kb/s

 (restart recording)

 cam1_105648.mp4, Duration: 00:03:12.26, start: 0.000000, bitrate: 661 kb/s

 ffmpeg version N-78596-g8fdee3e Copyright (c) 2000-2016 the FFmpeg
 developers
 built with gcc 4.8 (Ubuntu 4.8.4-2ubuntu1~14.04)
 configuration: --enable-gpl --enable-nonfree

 Result:
 Files when played through web server do not start for the period of
 seconds indicated
 by ffprobe 'start' output. So last file listed above waits for 174 seconds
 before it
 starts to play. Video that is recorded has accurate time displayed in it
 and I can
 see that recording does actually start at the time indicated by the file
 name, but
 the negative start value which must be written into the mp4 file causes
 the player
 to wait for that time before it starts playing. The effect seems to take
 several hours
  of recording to become apparent, once its started to produce incorrect
 start times
 the start time gradually becomes more negative with occasional large
 jumps.

 I'm currently running a recording with verbose logs turned on so hope to
 catch ffmpegs
  output showing pts, pts_time, dts and dts_time when it starts to fail and
 will
 update with that once I get it. Currently the start times on the files its
 recorded
 are showing 0 though so it might not be for a few hours.

 The code's a bit complex for me to get my head round but I do see that
 some rounding
 seems to be going on which might be responsible for this, maybe I am
 asking too much
 to record continuously for days. But I thought it was worth mentioning in
 case it
 is an actual bug.

 }}}
 Patches should be submitted to the ffmpeg-devel mailing list and not this
 bug tracker.

--
Ticket URL: <https://trac.ffmpeg.org/ticket/5263>
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