[FFmpeg-trac] #8443(undetermined:new): A/V drift when reencoding NTSC

FFmpeg trac at avcodec.org
Thu Dec 26 18:47:07 EET 2019

#8443: A/V drift when reencoding NTSC
             Reporter:               |                    Owner:
  madscientist159                    |
                 Type:  defect       |                   Status:  new
             Priority:  normal       |                Component:
                                     |  undetermined
              Version:  unspecified  |               Resolution:
             Keywords:               |               Blocked By:
             Blocking:               |  Reproduced by developer:  0
Analyzed by developer:  0            |

Comment (by madscientist159):

 Yes, I understand now that showwaves is not going to be able to help
 diagnose the other A/V sync issue due to this bug.  I'm still searching
 for an alternate method to view per-frame A/V sync using open source
 software, without much luck so far.

 kdenlive apparently uses ffmpeg for its audio waveform display, and is
 very much affected by the same bug.  This also added some confusion.

 The live streaming bug manifests as a desync of several hundred ms over a
 few hours, and is not practical to debug until a reliable way is found to
 measure the small (one or two ms) desync that would occur over a much
 shorter period of time.  I have an initial hardware method to detect the
 output sync within some hundreds of microseconds accuracy,  but since I
 cannot measure the *input* file A/V sync (yet) I am kind of stuck.

Ticket URL: <https://trac.ffmpeg.org/ticket/8443#comment:6>
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