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FFmpeg/libavcodec/mdct15.c
Rostislav Pehlivanov d2119f624d imdct15: rename to mdct15 and add a forward transform 
Handles strides (needed for Opus transients), does pre-reindexing and folding
without needing a copy.

Signed-off-by: Rostislav Pehlivanov <atomnuker@gmail.com>
2017-02-14 06:15:36 +00:00

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/*
* Copyright (c) 2013-2014 Mozilla Corporation
* Copyright (c) 2017 Rostislav Pehlivanov <atomnuker@gmail.com>
*
* This file is part of FFmpeg.
*
* FFmpeg is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* FFmpeg is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with FFmpeg; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
/**
* @file
* Celt non-power of 2 iMDCT
*/
#include <float.h>
#include <math.h>
#include <stddef.h>
#include "config.h"
#include "libavutil/attributes.h"
#include "libavutil/common.h"
#include "avfft.h"
#include "mdct15.h"
// complex c = a * b
#define CMUL3(cre, cim, are, aim, bre, bim) \
do { \
cre = are * bre - aim * bim; \
cim = are * bim + aim * bre; \
} while (0)
#define CMUL(c, a, b) CMUL3((c).re, (c).im, (a).re, (a).im, (b).re, (b).im)
av_cold void ff_mdct15_uninit(MDCT15Context **ps)
{
MDCT15Context *s = *ps;
if (!s)
return;
ff_fft_end(&s->ptwo_fft);
av_freep(&s->pfa_prereindex);
av_freep(&s->pfa_postreindex);
av_freep(&s->twiddle_exptab);
av_freep(&s->tmp);
av_freep(ps);
}
static void mdct15(MDCT15Context *s, float *dst, const float *src, ptrdiff_t stride);
static void imdct15_half(MDCT15Context *s, float *dst, const float *src,
ptrdiff_t stride, float scale);
static inline int init_pfa_reindex_tabs(MDCT15Context *s)
{
int i, j;
const int b_ptwo = s->ptwo_fft.nbits; /* Bits for the power of two FFTs */
const int l_ptwo = 1 << b_ptwo; /* Total length for the power of two FFTs */
const int inv_1 = l_ptwo << ((4 - b_ptwo) & 3); /* (2^b_ptwo)^-1 mod 15 */
const int inv_2 = 0xeeeeeeef & ((1U << b_ptwo) - 1); /* 15^-1 mod 2^b_ptwo */
s->pfa_prereindex = av_malloc(15 * l_ptwo * sizeof(*s->pfa_prereindex));
if (!s->pfa_prereindex)
return 1;
s->pfa_postreindex = av_malloc(15 * l_ptwo * sizeof(*s->pfa_postreindex));
if (!s->pfa_postreindex)
return 1;
/* Pre/Post-reindex */
for (i = 0; i < l_ptwo; i++) {
for (j = 0; j < 15; j++) {
const int q_pre = ((l_ptwo * j)/15 + i) >> b_ptwo;
const int q_post = (((j*inv_1)/15) + (i*inv_2)) >> b_ptwo;
const int k_pre = 15*i + ((j - q_pre*15) << b_ptwo);
const int k_post = i*inv_2*15 + j*inv_1 - 15*q_post*l_ptwo;
s->pfa_prereindex[i*15 + j] = k_pre;
s->pfa_postreindex[k_post] = l_ptwo*j + i;
}
}
return 0;
}
av_cold int ff_mdct15_init(MDCT15Context **ps, int inverse, int N, double scale)
{
MDCT15Context *s;
double alpha, theta;
int len2 = 15 * (1 << N);
int len = 2 * len2;
int i;
/* Tested and verified to work on everything in between */
if ((N < 2) || (N > 13))
return AVERROR(EINVAL);
s = av_mallocz(sizeof(*s));
if (!s)
return AVERROR(ENOMEM);
s->fft_n = N - 1;
s->len4 = len2 / 2;
s->len2 = len2;
s->inverse = inverse;
s->mdct = mdct15;
s->imdct_half = imdct15_half;
if (ff_fft_init(&s->ptwo_fft, N - 1, s->inverse) < 0)
goto fail;
if (init_pfa_reindex_tabs(s))
goto fail;
s->tmp = av_malloc_array(len, 2 * sizeof(*s->tmp));
if (!s->tmp)
goto fail;
s->twiddle_exptab = av_malloc_array(s->len4, sizeof(*s->twiddle_exptab));
if (!s->twiddle_exptab)
goto fail;
theta = 0.125f + (scale < 0 ? s->len4 : 0);
scale = sqrt(fabs(scale));
for (i = 0; i < s->len4; i++) {
alpha = 2 * M_PI * (i + theta) / len;
s->twiddle_exptab[i].re = cos(alpha) * scale;
s->twiddle_exptab[i].im = sin(alpha) * scale;
}
/* 15-point FFT exptab */
for (i = 0; i < 19; i++) {
if (i < 15) {
double theta = (2.0f * M_PI * i) / 15.0f;
if (!s->inverse)
theta *= -1;
s->exptab[i].re = cos(theta);
s->exptab[i].im = sin(theta);
} else { /* Wrap around to simplify fft15 */
s->exptab[i] = s->exptab[i - 15];
}
}
/* 5-point FFT exptab */
s->exptab[19].re = cos(2.0f * M_PI / 5.0f);
s->exptab[19].im = sin(2.0f * M_PI / 5.0f);
s->exptab[20].re = cos(1.0f * M_PI / 5.0f);
s->exptab[20].im = sin(1.0f * M_PI / 5.0f);
/* Invert the phase for an inverse transform, do nothing for a forward transform */
if (s->inverse) {
s->exptab[19].im *= -1;
s->exptab[20].im *= -1;
}
*ps = s;
return 0;
fail:
ff_mdct15_uninit(&s);
return AVERROR(ENOMEM);
}
/* Stride is hardcoded to 3 */
static inline void fft5(const FFTComplex exptab[2], FFTComplex *out,
const FFTComplex *in)
{
FFTComplex z0[4], t[6];
t[0].re = in[3].re + in[12].re;
t[0].im = in[3].im + in[12].im;
t[1].im = in[3].re - in[12].re;
t[1].re = in[3].im - in[12].im;
t[2].re = in[6].re + in[ 9].re;
t[2].im = in[6].im + in[ 9].im;
t[3].im = in[6].re - in[ 9].re;
t[3].re = in[6].im - in[ 9].im;
out[0].re = in[0].re + in[3].re + in[6].re + in[9].re + in[12].re;
out[0].im = in[0].im + in[3].im + in[6].im + in[9].im + in[12].im;
t[4].re = exptab[0].re * t[2].re - exptab[1].re * t[0].re;
t[4].im = exptab[0].re * t[2].im - exptab[1].re * t[0].im;
t[0].re = exptab[0].re * t[0].re - exptab[1].re * t[2].re;
t[0].im = exptab[0].re * t[0].im - exptab[1].re * t[2].im;
t[5].re = exptab[0].im * t[3].re - exptab[1].im * t[1].re;
t[5].im = exptab[0].im * t[3].im - exptab[1].im * t[1].im;
t[1].re = exptab[0].im * t[1].re + exptab[1].im * t[3].re;
t[1].im = exptab[0].im * t[1].im + exptab[1].im * t[3].im;
z0[0].re = t[0].re - t[1].re;
z0[0].im = t[0].im - t[1].im;
z0[1].re = t[4].re + t[5].re;
z0[1].im = t[4].im + t[5].im;
z0[2].re = t[4].re - t[5].re;
z0[2].im = t[4].im - t[5].im;
z0[3].re = t[0].re + t[1].re;
z0[3].im = t[0].im + t[1].im;
out[1].re = in[0].re + z0[3].re;
out[1].im = in[0].im + z0[0].im;
out[2].re = in[0].re + z0[2].re;
out[2].im = in[0].im + z0[1].im;
out[3].re = in[0].re + z0[1].re;
out[3].im = in[0].im + z0[2].im;
out[4].re = in[0].re + z0[0].re;
out[4].im = in[0].im + z0[3].im;
}
static void fft15(const FFTComplex exptab[22], FFTComplex *out, const FFTComplex *in, size_t stride)
{
int k;
FFTComplex tmp1[5], tmp2[5], tmp3[5];
fft5(exptab + 19, tmp1, in + 0);
fft5(exptab + 19, tmp2, in + 1);
fft5(exptab + 19, tmp3, in + 2);
for (k = 0; k < 5; k++) {
FFTComplex t[2];
CMUL(t[0], tmp2[k], exptab[k]);
CMUL(t[1], tmp3[k], exptab[2 * k]);
out[stride*k].re = tmp1[k].re + t[0].re + t[1].re;
out[stride*k].im = tmp1[k].im + t[0].im + t[1].im;
CMUL(t[0], tmp2[k], exptab[k + 5]);
CMUL(t[1], tmp3[k], exptab[2 * (k + 5)]);
out[stride*(k + 5)].re = tmp1[k].re + t[0].re + t[1].re;
out[stride*(k + 5)].im = tmp1[k].im + t[0].im + t[1].im;
CMUL(t[0], tmp2[k], exptab[k + 10]);
CMUL(t[1], tmp3[k], exptab[2 * k + 5]);
out[stride*(k + 10)].re = tmp1[k].re + t[0].re + t[1].re;
out[stride*(k + 10)].im = tmp1[k].im + t[0].im + t[1].im;
}
}
static void mdct15(MDCT15Context *s, float *dst, const float *src, ptrdiff_t stride)
{
int i, j;
const int len4 = s->len4, len3 = len4 * 3, len8 = len4 >> 1;
const int l_ptwo = 1 << s->ptwo_fft.nbits;
FFTComplex fft15in[15];
/* Folding and pre-reindexing */
for (i = 0; i < l_ptwo; i++) {
for (j = 0; j < 15; j++) {
float re, im;
const int k = s->pfa_prereindex[i*15 + j];
if (k < len8) {
re = -src[2*k+len3] - src[len3-1-2*k];
im = -src[len4+2*k] + src[len4-1-2*k];
} else {
re = src[2*k-len4] - src[1*len3-1-2*k];
im = -src[2*k+len4] - src[5*len4-1-2*k];
}
CMUL3(fft15in[j].re, fft15in[j].im, re, im, s->twiddle_exptab[k].re, -s->twiddle_exptab[k].im);
}
fft15(s->exptab, s->tmp + s->ptwo_fft.revtab[i], fft15in, l_ptwo);
}
/* Then a 15xN FFT (where N is a power of two) */
for (i = 0; i < 15; i++)
s->ptwo_fft.fft_calc(&s->ptwo_fft, s->tmp + l_ptwo*i);
/* Reindex again, apply twiddles and output */
for (i = 0; i < len8; i++) {
float re0, im0, re1, im1;
const int i0 = len8 + i, i1 = len8 - i - 1;
const int s0 = s->pfa_postreindex[i0], s1 = s->pfa_postreindex[i1];
CMUL3(im1, re0, s->tmp[s1].re, s->tmp[s1].im, s->twiddle_exptab[i1].im, s->twiddle_exptab[i1].re);
CMUL3(im0, re1, s->tmp[s0].re, s->tmp[s0].im, s->twiddle_exptab[i0].im, s->twiddle_exptab[i0].re);
dst[2*i1*stride ] = re0;
dst[2*i1*stride + stride] = im0;
dst[2*i0*stride ] = re1;
dst[2*i0*stride + stride] = im1;
}
}
static void imdct15_half(MDCT15Context *s, float *dst, const float *src,
ptrdiff_t stride, float scale)
{
FFTComplex fft15in[15];
FFTComplex *z = (FFTComplex *)dst;
int i, j, len8 = s->len4 >> 1, l_ptwo = 1 << s->ptwo_fft.nbits;
const float *in1 = src, *in2 = src + (s->len2 - 1) * stride;
/* Reindex input, putting it into a buffer and doing an Nx15 FFT */
for (i = 0; i < l_ptwo; i++) {
for (j = 0; j < 15; j++) {
const int k = s->pfa_prereindex[i*15 + j];
FFTComplex tmp = { *(in2 - 2*k*stride), *(in1 + 2*k*stride) };
CMUL(fft15in[j], tmp, s->twiddle_exptab[k]);
}
fft15(s->exptab, s->tmp + s->ptwo_fft.revtab[i], fft15in, l_ptwo);
}
/* Then a 15xN FFT (where N is a power of two) */
for (i = 0; i < 15; i++)
s->ptwo_fft.fft_calc(&s->ptwo_fft, s->tmp + l_ptwo*i);
/* Reindex again, apply twiddles and output */
for (i = 0; i < len8; i++) {
float re0, im0, re1, im1;
const int i0 = len8 + i, i1 = len8 - i - 1;
const int s0 = s->pfa_postreindex[i0], s1 = s->pfa_postreindex[i1];
CMUL3(re0, im1, s->tmp[s1].im, s->tmp[s1].re, s->twiddle_exptab[i1].im, s->twiddle_exptab[i1].re);
CMUL3(re1, im0, s->tmp[s0].im, s->tmp[s0].re, s->twiddle_exptab[i0].im, s->twiddle_exptab[i0].re);
z[i1].re = scale * re0;
z[i1].im = scale * im0;
z[i0].re = scale * re1;
z[i0].im = scale * im1;
}
}
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