[FFmpeg-devel] [PATCH] HE-AAC v1 decoder
Wed Jan 27 05:42:43 CET 2010
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).
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