[Vorbis-dev] Well decomposed mdct

[petshome at atlas.cz]

I did composition of butterfly8 and butterfly16 and I found, that these functions are well decomposed - decomposition doesn't lower computional speed. On the other hand the same can be done with butterfly8 - decomposition to butterfly4 (further decomposition is not possible) but there's no reason to do this. I think little improvement can be done by inlining them. Compiler and processor can do some speed up only in functions, not between them. Speculative execution works better without jumps.
Did anybody tested MDCT on pictures/video data? It can bring same computional load as DCT but lower data rates (as MP3 - Vorbis).
Did anybody tested arithmetic coding instead of Huffman coding? This can lower data rate (or increase quality). Computional complexity will increase but cannot be so high for Pentium 4. This can be audiophile option when coding. I don't suppose support of this on fixed-point decoders.

Spirit