[FFmpeg-trac] #8366(avformat:new): Audio ticks and video/audio out-of-sync when using MXF files with pre-charge
FFmpeg
trac at avcodec.org
Tue Nov 19 12:51:29 EET 2019
#8366: Audio ticks and video/audio out-of-sync when using MXF files with pre-
charge
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Reporter: HenkDemper | Owner:
Type: defect | Status: new
Priority: normal | Component: avformat
Version: git-master | Resolution:
Keywords: MXF | Blocked By:
Blocking: | Reproduced by developer: 0
Analyzed by developer: 0 |
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Comment (by ngaullie):
I have analyzed your files and I have another reading :
- every picture sample is encoded to your MOV file, and every audio sample
is rewrapped, there is no loss
- the loss of sync (ffmpeg bug) does not seem to be related to the MXF
wrapper itself. At the output, the MOV file has a video track with an edit
list that shift video of 0.0667s (precisely=2/29.97) - but not the audio
track, and this breaks sync.
It you disables B-frames when encoding (-bf 0), there is no precharge
signalization in the output, that should fix you problem, can you confirm
?
----
The input MXF file has a precharge value which is consistent amongst the
tracks (video/audios/tc), and I agree that, in this case, you can claim
its's Op1a because this is the state of the art, broadly implemented,
despite absence of clarification in actual texts.
Support for MXF having non-consistent precharges values does not seem
necessary in my opinion.
Handling MXF files having a consistent precharge value like yours is no
big deal with a first pass analysis and a basic trim clip switch; but of
course this is not ideal and could be enhanced.
--
Ticket URL: <https://trac.ffmpeg.org/ticket/8366#comment:9>
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