[lkhpinsx] Progressive robust media formats

Create a media format (images, audio, video) such that the effect of erased bytes results in a smooth degradation of quality over the entire media object.  Especially, the effect of a bursty erasure, e.g., a lost segment or packet, should be averaged over the entire object, perhaps making it barely perceptible.

Motivation was media inserted into Freenet: some parts might have become permanently irretrievable even after FEC, but show the resulting object anyway.