1/* 2 * MDCT/IMDCT transforms 3 * Copyright (c) 2002 Fabrice Bellard 4 * 5 * This file is part of Libav. 6 * 7 * Libav is free software; you can redistribute it and/or 8 * modify it under the terms of the GNU Lesser General Public 9 * License as published by the Free Software Foundation; either 10 * version 2.1 of the License, or (at your option) any later version. 11 * 12 * Libav is distributed in the hope that it will be useful, 13 * but WITHOUT ANY WARRANTY; without even the implied warranty of 14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 15 * Lesser General Public License for more details. 16 * 17 * You should have received a copy of the GNU Lesser General Public 18 * License along with Libav; if not, write to the Free Software 19 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA 20 */ 21 22#include <stdlib.h> 23#include <string.h> 24#include "libavutil/common.h" 25#include "libavutil/mathematics.h" 26#include "fft.h" 27#include "fft-internal.h" 28 29/** 30 * @file 31 * MDCT/IMDCT transforms. 32 */ 33 34#if CONFIG_FFT_FLOAT 35# define RSCALE(x) (x) 36#else 37# define RSCALE(x) ((x) >> 1) 38#endif 39 40/** 41 * init MDCT or IMDCT computation. 42 */ 43av_cold int ff_mdct_init(FFTContext *s, int nbits, int inverse, double scale) 44{ 45 int n, n4, i; 46 double alpha, theta; 47 int tstep; 48 49 memset(s, 0, sizeof(*s)); 50 n = 1 << nbits; 51 s->mdct_bits = nbits; 52 s->mdct_size = n; 53 n4 = n >> 2; 54 s->mdct_permutation = FF_MDCT_PERM_NONE; 55 56 if (ff_fft_init(s, s->mdct_bits - 2, inverse) < 0) 57 goto fail; 58 59 s->tcos = av_malloc(n/2 * sizeof(FFTSample)); 60 if (!s->tcos) 61 goto fail; 62 63 switch (s->mdct_permutation) { 64 case FF_MDCT_PERM_NONE: 65 s->tsin = s->tcos + n4; 66 tstep = 1; 67 break; 68 case FF_MDCT_PERM_INTERLEAVE: 69 s->tsin = s->tcos + 1; 70 tstep = 2; 71 break; 72 default: 73 goto fail; 74 } 75 76 theta = 1.0 / 8.0 + (scale < 0 ? n4 : 0); 77 scale = sqrt(fabs(scale)); 78 for(i=0;i<n4;i++) { 79 alpha = 2 * M_PI * (i + theta) / n; 80 s->tcos[i*tstep] = FIX15(-cos(alpha) * scale); 81 s->tsin[i*tstep] = FIX15(-sin(alpha) * scale); 82 } 83 return 0; 84 fail: 85 ff_mdct_end(s); 86 return -1; 87} 88 89/** 90 * Compute the middle half of the inverse MDCT of size N = 2^nbits, 91 * thus excluding the parts that can be derived by symmetry 92 * @param output N/2 samples 93 * @param input N/2 samples 94 */ 95void ff_imdct_half_c(FFTContext *s, FFTSample *output, const FFTSample *input) 96{ 97 int k, n8, n4, n2, n, j; 98 const uint16_t *revtab = s->revtab; 99 const FFTSample *tcos = s->tcos; 100 const FFTSample *tsin = s->tsin; 101 const FFTSample *in1, *in2; 102 FFTComplex *z = (FFTComplex *)output; 103 104 n = 1 << s->mdct_bits; 105 n2 = n >> 1; 106 n4 = n >> 2; 107 n8 = n >> 3; 108 109 /* pre rotation */ 110 in1 = input; 111 in2 = input + n2 - 1; 112 for(k = 0; k < n4; k++) { 113 j=revtab[k]; 114 CMUL(z[j].re, z[j].im, *in2, *in1, tcos[k], tsin[k]); 115 in1 += 2; 116 in2 -= 2; 117 } 118 s->fft_calc(s, z); 119 120 /* post rotation + reordering */ 121 for(k = 0; k < n8; k++) { 122 FFTSample r0, i0, r1, i1; 123 CMUL(r0, i1, z[n8-k-1].im, z[n8-k-1].re, tsin[n8-k-1], tcos[n8-k-1]); 124 CMUL(r1, i0, z[n8+k ].im, z[n8+k ].re, tsin[n8+k ], tcos[n8+k ]); 125 z[n8-k-1].re = r0; 126 z[n8-k-1].im = i0; 127 z[n8+k ].re = r1; 128 z[n8+k ].im = i1; 129 } 130} 131 132/** 133 * Compute inverse MDCT of size N = 2^nbits 134 * @param output N samples 135 * @param input N/2 samples 136 */ 137void ff_imdct_calc_c(FFTContext *s, FFTSample *output, const FFTSample *input) 138{ 139 int k; 140 int n = 1 << s->mdct_bits; 141 int n2 = n >> 1; 142 int n4 = n >> 2; 143 144 ff_imdct_half_c(s, output+n4, input); 145 146 for(k = 0; k < n4; k++) { 147 output[k] = -output[n2-k-1]; 148 output[n-k-1] = output[n2+k]; 149 } 150} 151 152/** 153 * Compute MDCT of size N = 2^nbits 154 * @param input N samples 155 * @param out N/2 samples 156 */ 157void ff_mdct_calc_c(FFTContext *s, FFTSample *out, const FFTSample *input) 158{ 159 int i, j, n, n8, n4, n2, n3; 160 FFTDouble re, im; 161 const uint16_t *revtab = s->revtab; 162 const FFTSample *tcos = s->tcos; 163 const FFTSample *tsin = s->tsin; 164 FFTComplex *x = (FFTComplex *)out; 165 166 n = 1 << s->mdct_bits; 167 n2 = n >> 1; 168 n4 = n >> 2; 169 n8 = n >> 3; 170 n3 = 3 * n4; 171 172 /* pre rotation */ 173 for(i=0;i<n8;i++) { 174 re = RSCALE(-input[2*i+n3] - input[n3-1-2*i]); 175 im = RSCALE(-input[n4+2*i] + input[n4-1-2*i]); 176 j = revtab[i]; 177 CMUL(x[j].re, x[j].im, re, im, -tcos[i], tsin[i]); 178 179 re = RSCALE( input[2*i] - input[n2-1-2*i]); 180 im = RSCALE(-input[n2+2*i] - input[ n-1-2*i]); 181 j = revtab[n8 + i]; 182 CMUL(x[j].re, x[j].im, re, im, -tcos[n8 + i], tsin[n8 + i]); 183 } 184 185 s->fft_calc(s, x); 186 187 /* post rotation */ 188 for(i=0;i<n8;i++) { 189 FFTSample r0, i0, r1, i1; 190 CMUL(i1, r0, x[n8-i-1].re, x[n8-i-1].im, -tsin[n8-i-1], -tcos[n8-i-1]); 191 CMUL(i0, r1, x[n8+i ].re, x[n8+i ].im, -tsin[n8+i ], -tcos[n8+i ]); 192 x[n8-i-1].re = r0; 193 x[n8-i-1].im = i0; 194 x[n8+i ].re = r1; 195 x[n8+i ].im = i1; 196 } 197} 198 199av_cold void ff_mdct_end(FFTContext *s) 200{ 201 av_freep(&s->tcos); 202 ff_fft_end(s); 203} 204