ffmpeg feature request: new cropdetect based on motionlessness

[pat284e]

The filter "cropdetect" is helpful to crop off black rectangular rim or black outer belt. However, I need to crop off a motionless pictorial belt that surrounds a motionful video content. A motionless pictorial belt that surrounds a motionful video content may be thought of as a big still picture into which a small video is overlaid. (Note that the size and location of the small video inside the big picture is steady and immutable.)

So, I need a new different kind of "cropdetect" that works based on motionlessness but not on blackness.

I will try to attach or upload an example video. Here is the code that composed the sample video.

ffmpeg -f image2 -loop 1 -t 6 -thread_queue_size 500 -i BigPicture.png -i SmallVideo.mp4 -filter_complex "overlay=140:50" -vcodec h264 VideoWithPictorialBelt.mp4

What I need is to extract the small video by removing the surrounding motionless pictorial belt. I need some automatic detection of appropriate parameters for the crop, when I do not know the parameters or when it is difficult for me to find the parameters.

Key words: "motionless pictorial belt", "pictorial outer frame", "pictorial outer rim", "motion-based cropdetect", "motionlessness-based cropdetect"

[pat284e]

Video surrounded by motionless pictorial belt

[Elon Musk]

-vf tblend=all_mode=difference,cropdetect