ref: 822ac747bc1da9df628b98553697445f1e59742a
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.
*/
#ifndef MDCT_H
#define MDCT_H
#include "kiss_fft.h"
#include "arch.h"
typedef struct {
int n;
kiss_fft_cfg kfft;
kiss_twiddle_scalar * restrict trig;
} mdct_lookup;
void mdct_init(mdct_lookup *l,int N);
void mdct_clear(mdct_lookup *l);
/** Compute a forward MDCT and scale by 4/N */
void mdct_forward(const mdct_lookup *l, kiss_fft_scalar *in, kiss_fft_scalar *out, const celt_word16_t *window, int overlap);
/** Compute a backward MDCT (no scaling) and performs weighted overlap-add
(scales implicitly by 1/2) */
void mdct_backward(const mdct_lookup *l, kiss_fft_scalar *in, kiss_fft_scalar *out, const celt_word16_t * restrict window, int overlap);
#endif