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Floating out of a-v sync, way to fix?

sspphheerraa
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Hello there!
I have the film which is out of a-v sync. The worse thing is that out of sync is floating. So correcting that is possible (as I think) by cutting audio track into pieces and stretch/squeeze (time duration) each of them according to picture.
Is there way to do it in kdenlive?
capslock
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Yes, you can separate video and audio track, then ungroup them and edit the audio track.

If audio changes constantly over time, you can also use ffmpeg to demux the footage, adjust the audio to the correct length in audacity and mux video and audio again. This would have he advantage that you will not render and have no quality loss.
sspphheerraa
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The out of sync is FLOATING.
It means that in one places sound is ahead of video and in other places it falls behind.
Possibly the 'atempo' ffmpeg filter might be useful, but unfortunately it's absent in kdenlive...
vpinon
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Hello,
FFmpeg(->MLT->Kdenlive) audio navigation is imprecise with VBR codecs (you might see its warning if running from a console)
Try to transcode your audio to WAV (either muxed with video or separate), cuts should now be much more precise.
sspphheerraa
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vpinon wrote:Hello,
FFmpeg(->MLT->Kdenlive) audio navigation is imprecise with VBR codecs (you might see its warning if running from a console)
Try to transcode your audio to WAV (either muxed with video or separate), cuts should now be much more precise.

It goes without saying.

Any ideas about topic subj?
vpinon
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That's what I am speaking about: what is your audio source codec? video source?
I do transcode my source media to MOV/(WAV+MJPEG) (huge files) or DNxHD when I face A/V sync issues, it has always solved the problem.
sspphheerraa
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vpinon wrote:That's what I am speaking about: what is your audio source codec? video source?

avi(ffvhuff + pcm_s16le)
Video stream is from VHS and sound stream is from HDTV (The goal is to mux 4:3 fullscreen video from VHS with high quality sound from HDTV which is cropped 16:9 widescreen). These two different sources (VHS, HDTV) have two different stamps of time initially. So, the floating out of sync is not because of codecs.
Stetsbequem
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I would try another container first. (ffmpeg -i x.avi -c copy x.mkv)


Either you choose the right job for the tool, or the right tool for the job.
sspphheerraa
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Stetsbequem wrote:I would try another container first. (ffmpeg -i x.avi -c copy x.mkv)

And what will it give?

 
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