Make 3s sketch filter effect every minute in ffmpeg
Solution 1:
You'll need to run an edge detector.
Basic syntax is
ffmpeg -i in.mp4 -vf "edgedetect=enable='gt(mod(t,60),57)',negate" -c:a copy out.mp4
The negate filter is added since the output of edgedetect is white edges on black canvas,
If the edgedetect options don't provide fine enough tweaking, run a convolution filter beforehand.
ffmpeg -i in.mp4 -vf "convolution=0 -1 0 -1 5 -1 0 -1 0:0 -1 0 -1 5 -1 0 -1 0:0 -1 0 -1 5 -1 0 -1 0:0 -1 0 -1 5 -1 0 -1 0:enable='gt(mod(t,60),57)',edgedetect=enable='gt(mod(t,60),57)',negate" -c:a copy out.mp4