Here is a command that we can get images composed of the screenshots when the scene changed:
$ ffmpeg -i YosemiteHDI.mp4 -vf select='gt(scene\,0.4)',scale=640:360,tile -frames:v 1 Yosemite_mosaic.png
Here is the output:
The following command will select every 300th frame, scale it to 640x360 pixels and create 6x4 tiles in the output image:
$ ffmpeg -i YosemiteHDI.mp4 -frames 1 -vf "select=not(mod(n\,500)),scale=640:360,tile=4x3" Yosemite_mosaic2.png
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