[FFmpeg-user] Combining 24fps Video with 23.976fps Audio

[Carl Eugen Hoyos]

Sam Logan <shapableline <at> gmail.com> writes:

> ffmpeg -i "Video1.mp4" -i "Video2.mp4" -acodec copy 
> -vcodec copy -map 0:0 -map 1:1 -map 0:1 "Output.mkv"

I don't see how you can change the speed of audio with 
-codec copy, so below applies to reencoding.
-r 24 / -r 24000/1001 might allow to change the video 
speed even with -vcodec copy.

> Which works fine until I play the resulting video, 
> whereupon I realized that I overlooked that Video1 
> had a framerate of 24 fps, whereas Video2 has a framerate 
> of 23.976 fps

The atempo and the setpts filter should allow you to change 
the speed of the files:
http://ffmpeg.org/ffmpeg-filters.html#setpts_002c-asetpts
http://ffmpeg.org/ffmpeg-filters.html#atempo

Carl Eugen