[FFmpeg-user] Syncing stereo videos - what method?

Paul B Mahol onemda at gmail.com
Sat Aug 29 07:50:16 CEST 2015

Dana 29. 8. 2015. 01:40 osoba "Jesper Taxbøl" <jesper at taxboel.dk> napisala
> Hi Guys,
> I am trying to sync two videos recorded simultaniously from a stereo
> I am extracting their audio (mono) and find their offset, which I can
> easily find in Audacity. With the offset in hand I cut off the start of
>  the earliest video, so they start at the same time. I use the -ss flag
> this.
>  ffmpeg -ss 0.75 -i A.mp4 -acodec copy -vcodec copy cut_A.mp4
> Hereafter I assemble them side by side into one video using a complex
> filter.
> I am however having trouble with their syncronization in the end product.
> I am therefore wondering if the -ss flag is the right way to do this or if
> I can achieve syncronization between the videos a different way?

You can use trim filter to trim to exact frame, but you cannot use it with
-c copy.

> I suspect the -ss method is affected by where there are keyframes in the
> video as I constantly get it wrong more than a second.
> All ideas are welcome.
> Kind regards
> Jesper
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