[FFmpeg-devel] [PATCH] 1D DCT for dsputil
pross at xvid.org
Tue Dec 22 12:25:51 CET 2009
On Mon, Dec 21, 2009 at 02:02:00PM -0500, Daniel Verkamp wrote:
> In an effort to get at least some parts of the Bink patch committed, I
> am splitting it into separable pieces.
> This is a one-dimensional floating-point DCT used by Bink audio. The
> actual code was written by Peter Ross.
> The comments I myself have about this code:
> - Should it be using math.h cos()/sin() or some lookup table approach?
> - Can there be a test written? (I don't know enough about the math
> involved to write a sane test...)
Thanks for taking the time to split the patch.
Note that the algorithm here is inefficient. It requires a 2*N FFT,
whereas there are ways of achieving this with 1*N FFT. Michael posted
some info on this many months ago.
IIRC, optimising the DCT was the only outstanding comment raised against
my earlier Bink audio patch. Reported audio glitches were fixed.
(A907 E02F A6E5 0CD2 34CD 20D2 6760 79C5 AC40 DD6B)
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