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Sync issue slowing down a video and audio mp4 file

Posted: Wed Jun 12, 2019 12:42 pm
by giulianocatrambone
Hi,
I need to slow down a bit a video and audio mp4 file.

Looked at the page
https://trac.ffmpeg.org/wiki/How to speed up / slow down a video
I'm able to slow down a video-audio by the half of the original speed using the command
ffmpeg -i input.mkv -filter_complex "[0:v]setpts=2.0*PTS[v];[0:a]atempo=0.5[a]" -map "[v]" -map "[a]" output.mkv

The problem is that the half of the original speed is too much, I would need a bit faster.
So I tried the command:
ffmpeg -i input.mkv -filter_complex "[0:v]setpts=1.5*PTS[v];[0:a]atempo=0.75[a]" -map "[v]" -map "[a]" output.mkv
but the problem here is that the resulting video is out of sync.

How I can solve this issue?
Thanks
Giuliano