Similar to other compression methods, it uses keyframes (which are saved frames that exist throughout the video) as the starting point, after which the next frame is a diff of that until you reach the next keyframe. It seems to generate keyframes when the compression drops below a certain level (at which point you might as well just store the compressed frame instead of the bloom bitmap).

https://github.com/ross39/new_bloom_filter_repo/blob/4798d90...