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Moves the bitrev step to the IMDCT pre-rotation

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This commit is contained in:
Jean-Marc Valin 2013-12-20 23:13:29 -05:00
parent 8e02afcfff
commit 2e26b82ec2
4 changed files with 30 additions and 18 deletions
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18
celt/kiss_fft.c
View file

@ -665,7 +665,7 @@ void opus_fft(const kiss_fft_state *st,const kiss_fft_cpx *fin,kiss_fft_cpx *fou
}
}
void opus_ifft(const kiss_fft_state *st,const kiss_fft_cpx *fin,kiss_fft_cpx *fout)
void opus_ifft_impl(const kiss_fft_state *st,kiss_fft_cpx *fout)
{
int m2, m;
int p;
@ -676,11 +676,6 @@ void opus_ifft(const kiss_fft_state *st,const kiss_fft_cpx *fin,kiss_fft_cpx *fo
/* st->shift can be -1 */
shift = st->shift>0 ? st->shift : 0;
celt_assert2 (fin != fout, "In-place FFT not supported");
/* Bit-reverse the input */
for (i=0;i<st->nfft;i++)
fout[st->bitrev[i]] = fin[i];
fstride[0] = 1;
L=0;
do {
@ -717,3 +712,14 @@ void opus_ifft(const kiss_fft_state *st,const kiss_fft_cpx *fin,kiss_fft_cpx *fo
}
}
#ifdef TEST_UNIT_DFT_C
void opus_ifft(const kiss_fft_state *st,const kiss_fft_cpx *fin,kiss_fft_cpx *fout)
{
int i;
celt_assert2 (fin != fout, "In-place FFT not supported");
/* Bit-reverse the input */
for (i=0;i<st->nfft;i++)
fout[st->bitrev[i]] = fin[i];
opus_ifft_impl(st, fout);
}
#endif

2
celt/kiss_fft.h
View file

@ -130,6 +130,8 @@ kiss_fft_state *opus_fft_alloc(int nfft,void * mem,size_t * lenmem);
void opus_fft(const kiss_fft_state *cfg,const kiss_fft_cpx *fin,kiss_fft_cpx *fout);
void opus_ifft(const kiss_fft_state *cfg,const kiss_fft_cpx *fin,kiss_fft_cpx *fout);
void opus_ifft_impl(const kiss_fft_state *st,kiss_fft_cpx *fout);
void opus_fft_free(const kiss_fft_state *cfg);
#ifdef __cplusplus

27
celt/mdct.c
View file

@ -214,13 +214,13 @@ void clt_mdct_backward(const mdct_lookup *l, kiss_fft_scalar *in, kiss_fft_scala
int i;
int N, N2, N4;
kiss_twiddle_scalar sine;
VARDECL(kiss_fft_scalar, f2);
VARDECL(kiss_fft_cpx, f2);
SAVE_STACK;
N = l->n;
N >>= shift;
N2 = N>>1;
N4 = N>>2;
ALLOC(f2, N2, kiss_fft_scalar);
ALLOC(f2, N4, kiss_fft_cpx);
/* sin(x) ~= x here */
#ifdef FIXED_POINT
sine = TRIG_UPSCALE*(QCONST16(0.7853981f, 15)+N2)/N;
@ -233,23 +233,26 @@ void clt_mdct_backward(const mdct_lookup *l, kiss_fft_scalar *in, kiss_fft_scala
/* Temp pointers to make it really clear to the compiler what we're doing */
const kiss_fft_scalar * OPUS_RESTRICT xp1 = in;
const kiss_fft_scalar * OPUS_RESTRICT xp2 = in+stride*(N2-1);
kiss_fft_scalar * OPUS_RESTRICT yp = f2;
const kiss_twiddle_scalar *t = &l->trig[0];
kiss_fft_cpx * OPUS_RESTRICT yp = f2;
const kiss_twiddle_scalar * OPUS_RESTRICT t = &l->trig[0];
const opus_int16 * OPUS_RESTRICT bitrev = l->kfft[shift]->bitrev;
for(i=0;i<N4;i++)
{
kiss_fft_scalar yr, yi;
kiss_fft_cpx yc;
yr = -S_MUL(*xp2, t[i<<shift]) + S_MUL(*xp1,t[(N4-i)<<shift]);
yi = -S_MUL(*xp2, t[(N4-i)<<shift]) - S_MUL(*xp1,t[i<<shift]);
/* works because the cos is nearly one */
*yp++ = yr - S_MUL(yi,sine);
*yp++ = yi + S_MUL(yr,sine);
yc.r = yr - S_MUL(yi,sine);
yc.i = yi + S_MUL(yr,sine);
/* Storing the pre-rotation directly in the bitrev order. */
yp[*bitrev++] = yc;
xp1+=2*stride;
xp2-=2*stride;
}
}
/* Inverse N/4 complex FFT. This one should *not* downscale even in fixed-point */
opus_ifft(l->kfft[shift], (kiss_fft_cpx *)f2, (kiss_fft_cpx *)(out+(overlap>>1)));
opus_ifft_impl(l->kfft[shift], f2);
/* Post-rotate and de-shuffle from both ends of the buffer at once to make
it in-place. */
@ -263,15 +266,15 @@ void clt_mdct_backward(const mdct_lookup *l, kiss_fft_scalar *in, kiss_fft_scala
{
kiss_fft_scalar re, im, yr, yi;
kiss_twiddle_scalar t0, t1;
re = yp0[0];
im = yp0[1];
re = f2[i].r;
im = f2[i].i;
t0 = t[i<<shift];
t1 = t[(N4-i)<<shift];
/* We'd scale up by 2 here, but instead it's done when mixing the windows */
yr = S_MUL(re,t0) - S_MUL(im,t1);
yi = S_MUL(im,t0) + S_MUL(re,t1);
re = yp1[0];
im = yp1[1];
re = f2[N4-i-1].r;
im = f2[N4-i-1].i;
/* works because the cos is nearly one */
yp0[0] = -(yr - S_MUL(yi,sine));
yp1[1] = yi + S_MUL(yr,sine);

1
celt/tests/test_unit_dft.c
View file

@ -38,6 +38,7 @@
#include <stdio.h>
#define CELT_C
#define TEST_UNIT_DFT_C
#include "stack_alloc.h"
#include "kiss_fft.h"
#include "kiss_fft.c"