ref: 43b3537d380e50db1acfd7109cfb0c091282c59f
dir: /libcelt/mdct.h/
/* (C) 2008 Jean-Marc Valin, CSIRO
*/
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/* This is a simple MDCT implementation that uses a N/4 complex FFT
to do most of the work. It should be relatively straightforward to
plug in pretty much and FFT here.
This replaces the Vorbis FFT (and uses the exact same API), which
was a bit too messy and that was ending up duplicating code
(might as well use the same FFT everywhere).
The algorithm is similar to (and inspired from) Fabrice Bellard's
MDCT implementation in FFMPEG, but has differences in signs, ordering
and scaling in many places.
*/
#include "kiss_fft.h"
typedef struct {
int n;
kiss_fft_cfg kfft;
kiss_twiddle_scalar *trig;
} mdct_lookup;
void mdct_init(mdct_lookup *l,int N);
void mdct_clear(mdct_lookup *l);
/** Compute a forward MDCT and scale by 2/N */
void mdct_forward(mdct_lookup *l, kiss_fft_scalar *in, kiss_fft_scalar *out);
/** Compute a backward MDCT (no scaling) */
void mdct_backward(mdct_lookup *l, kiss_fft_scalar *in, kiss_fft_scalar *out);