[FFmpeg-devel] [PATCH] HE-AAC v1 decoder

Michael Niedermayer michaelni
Wed Jan 27 17:37:45 CET 2010

On Tue, Jan 26, 2010 at 11:42:43PM -0500, Vitor Sessak wrote:
> Alex Converse wrote:
>> Greetings Sirs,
>> Enclosed you will find one (1) HE-AAC decoder to make glorious great
>> software FFmpeg.
> Nice!! Just one comment:
>> More seriously, attached is a patch that implements SBR and integrates
>> it with AAC to make an HE-AAC v1 decoder. A filterbank compatible with
>> ff_float_to_int16_interleave_c is missing but otherwise the code is
>> complete. Note that the decoder spends 90+% of its time in the
>> filterbank and will be extremely slow on any system that does not have
>> a asm version of  scalarproduct_float().
> This filtering looks pretty much to me a kind of FFT. I think it should be 
> possible to do it using some of the existing FFT (or RFDT or DCT or IMDCT) 
> with some pre- and post-processing. Its complexity will go down from O(n^2) 
> to O(n log n).

Either way, this question must be resolved before the related code is asm
optimized. because its kinda lame to optimize the wrong algorithm in asm


Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

He who knows, does not speak. He who speaks, does not know. -- Lao Tsu
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