[FFmpeg-devel] [PATCH] activate ac3 decoder

[Michael Niedermayer]

Hi

On Tue, Aug 07, 2007 at 06:14:59AM -0400, Justin Ruggles wrote:
[...]
> > What's the slowest part of AC3 decoding currently?
> 
> I haven't profiled it yet, but my best guess is the 512-point IMDCT.

official liba52 has a split radix FFT writen in C it doesnt have a
SSE one, it also supports djbfft (which itself neither supports SSE
AFAIK)

our fft is crap, all of it ...
the C fft is a very slow cooley tukey fft
our SSE fft contains unneeded instructions (see 
MPlayer-svn/mplayer/liba52/imdct.c for anonther inefficit cooley tukey
SSE fft but at least with fewer SSE instructions, note this one was
writen by me ...)

so to solve this and make our code faster
1. implement a plain C split radix fft

2. implement djbfft support (this should be trivial considering that
liba52 needs something like 5 lines of code for it)

3. fix the SSE code so it doesnt do redundant moves

4. implement a split radix SSE FFT

[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

The worst form of inequality is to try to make unequal things equal.
-- Aristotle
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