I need to replace video in a larger mp4 file with a smaller mp4 clip - but leaving the original (larger clip) audio intact.
So for example I might want the first 2 seconds of SmallClip.mp4 to replace the video in LargeClip.mp4 starting at (say) 10 seconds in to LargeClip.mp4.
The format of both clips is likely to be identical, so I'm hoping I can copy instead of decoding for speed etc (I'll have to do it a lot).
Finally, I might want to do exactly the same thing but in several places in LargeClip.mp4 - all places in the output getting the video replaced with the same input clip's video. I'd be happy to do this in multiple oerations if neccessary but if it were possible on one command so much the better :)
I'm reading up on the options for ffmpeg but I'm new to it and haven't figured it out yet. Any help much appreciated!