How would you implement analog parity? Parity doesn't translate well as a concept into the analog space.

You can take an analog signal and "quantize" it into sixteen possible values so that you can apply a parity algorithm that returns sensible results and doesn't fail with expected noise, but you're digitizing the signal.

I don't understand what analog has to do with it? The video is digitized first, then error-correction (parity?) information added before transmission, so all parity would be related to the digital bitstream -- unless I missed something?

Even then I think it would still be all-or-nothing. That may increase the chances of "all" over "nothing" but not allow graceful degradation of the video.

Hierarchical coding: send a low quality version of the video with high redundancy, and a higher quality refinement of the video with lesser redundancy.