[askvictor]

Interesting; some time ago the Ogg audio transport was working on bitrate peeling https://en.wikipedia.org/wiki/Bitrate_peeling with the basic idea that a stream can be encoded at one bitrate but can be served at that or any lower bitrate. A simpler example is FM stereo radio - the main frequency provides a mono audio signal, which works just fine, but if the receiver can also pick up the stereo sub-frequency (containing just the diff of left and right channels), it gets stereo.

Anyways, the wikipedia page linked above links to this about the same concept, for video: https://en.wikipedia.org/wiki/Scalable_Video_Coding so it might be feasible. Not sure how feasible/secure encrypting this would be.