Different principles for Lossy compression
What is "unnecessary" ?
Averaging ( + repetition/pattern ) (clever forced digitisation)
Range Reduction : from 32 bits to 16 bits, to 8 bits (clever forced quantisation)
issues : classical music ( Orff - Carmina Burana : o Fortuna , Ravel's Boléro ) / subtleties in high contrasted pictures
Variation in Quantisation
Selectivity
Use the way human perception works : more receptive to high frequencies
E.g. : we see better objects that move, we notice the edge of things more
than the centers
Frame difference Compression
In video, sending information only about what did change from a key frame
(head talking in front of a fixed background)