Hi all,
While working on a Kdenlive rendering issue, I noticed that the avformat
consumer duplicates the last frame on encoding. So the resulting file is
1 frame longer than wanted.
This is easily reproducible with:
melt color:red out=10 -consumer avformat:red.mp4
This produces a 12 frames video, instead of 11 (0 - 10 range).
You can notice the frame duplication using the count producer:
melt count style=frames out=10 -consumer avformat:count.mp4
Results in a 12 frames long video with last video frame repeated twice.
After some tests, I can give the following details:
This only happens when encoding audio, so is related to the handling of
audio data.
rendering with an=1 (to disable audio) gives a correct length file.
After more tests, I traced back the regressions to this commit (1) from
may 2018 (!), switching to the newer FFmpeg api using
avcodec_send_frame()/avcodec_receive_packet.
Commenting out the code flushing audio data :
https://github.com/mltframework/mlt/blob/master/src/modules/avformat/consumer_avformat.c#L2184
Seems to fixes the problem, but I am not sure it's the correct solution.
So if anyone has a hint on how to correctly fix this, help is welcome.
Best regards,
Jean-Baptiste
(1)
https://github.com/mltframework/mlt/commit/1937704936a6569f181b7295fb8bafd223d13d66#diff-1bba886ccf70d0171adb4e7842ec3d58
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