[FFmpeg-devel] [PATCH] 1D DCT for dsputil

pross at xvid.org pross
Tue Dec 22 12:25:51 CET 2009

On Mon, Dec 21, 2009 at 02:02:00PM -0500, Daniel Verkamp wrote:
> Hi,
> 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.

-- Peter
(A907 E02F A6E5 0CD2 34CD 20D2 6760 79C5 AC40 DD6B)
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