ffmpeg overlay tranparency video loop

Question

I'm trying to superimpose a transparent video on another video. If the original video has a longer duration than the transparent video, then the transparent video should be looped until the end of the original video. I wrote the following operation, but the transparent video does not repeat. How can I change this ffmpeg command to make the overlay video loop?

-i preresult.mp4 -c:v libvpx-vp9 -i Overlay.webm -filter_complex ""[1]loop=0,setpts=N/FRAME_RATE/TB[bg];[0][bg]overlay=shortest=1:x=(W-w)/2:y=(H-h)/2"" -preset ultrafast output.mp4

Answer 1

If you're using a recent git build, use stream_loop and drop the loop filter:

-stream_loop -1 -c:v libvpx-vp9 -i Overlay.webm -filter_complex "[0][1]overlay=...

For older builds, you'll have to supply the loop filter with full details,

[1]loop=-1:C:0,setpts=N/FRAME_RATE/TB[bg]

where C is a value greater than the frame count of the file.