1/* 2 * MDCT/IMDCT transforms 3 * Copyright (c) 2002 Fabrice Bellard 4 * 5 * This file is part of FFmpeg. 6 * 7 * FFmpeg 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 * FFmpeg 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 FFmpeg; if not, write to the Free Software 19 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA 20 */ 21#include "dsputil.h" 22 23/** 24 * @file libavcodec/mdct.c 25 * MDCT/IMDCT transforms. 26 */ 27 28// Generate a Kaiser-Bessel Derived Window. 29#define BESSEL_I0_ITER 50 // default: 50 iterations of Bessel I0 approximation 30av_cold void ff_kbd_window_init(float *window, float alpha, int n) 31{ 32 int i, j; 33 double sum = 0.0, bessel, tmp; 34 double local_window[n]; 35 double alpha2 = (alpha * M_PI / n) * (alpha * M_PI / n); 36 37 for (i = 0; i < n; i++) { 38 tmp = i * (n - i) * alpha2; 39 bessel = 1.0; 40 for (j = BESSEL_I0_ITER; j > 0; j--) 41 bessel = bessel * tmp / (j * j) + 1; 42 sum += bessel; 43 local_window[i] = sum; 44 } 45 46 sum++; 47 for (i = 0; i < n; i++) 48 window[i] = sqrt(local_window[i] / sum); 49} 50 51DECLARE_ALIGNED(16, float, ff_sine_128 [ 128]); 52DECLARE_ALIGNED(16, float, ff_sine_256 [ 256]); 53DECLARE_ALIGNED(16, float, ff_sine_512 [ 512]); 54DECLARE_ALIGNED(16, float, ff_sine_1024[1024]); 55DECLARE_ALIGNED(16, float, ff_sine_2048[2048]); 56DECLARE_ALIGNED(16, float, ff_sine_4096[4096]); 57float *ff_sine_windows[6] = { 58 ff_sine_128, ff_sine_256, ff_sine_512, ff_sine_1024, ff_sine_2048, ff_sine_4096 59}; 60 61// Generate a sine window. 62av_cold void ff_sine_window_init(float *window, int n) { 63 int i; 64 for(i = 0; i < n; i++) 65 window[i] = sinf((i + 0.5) * (M_PI / (2.0 * n))); 66} 67 68/** 69 * init MDCT or IMDCT computation. 70 */ 71av_cold int ff_mdct_init(MDCTContext *s, int nbits, int inverse) 72{ 73 int n, n4, i; 74 double alpha; 75 76 memset(s, 0, sizeof(*s)); 77 n = 1 << nbits; 78 s->nbits = nbits; 79 s->n = n; 80 n4 = n >> 2; 81 s->tcos = av_malloc(n4 * sizeof(FFTSample)); 82 if (!s->tcos) 83 goto fail; 84 s->tsin = av_malloc(n4 * sizeof(FFTSample)); 85 if (!s->tsin) 86 goto fail; 87 88 for(i=0;i<n4;i++) { 89 alpha = 2 * M_PI * (i + 1.0 / 8.0) / n; 90 s->tcos[i] = -cos(alpha); 91 s->tsin[i] = -sin(alpha); 92 } 93 if (ff_fft_init(&s->fft, s->nbits - 2, inverse) < 0) 94 goto fail; 95 return 0; 96 fail: 97 av_freep(&s->tcos); 98 av_freep(&s->tsin); 99 return -1; 100} 101 102/* complex multiplication: p = a * b */ 103#define CMUL(pre, pim, are, aim, bre, bim) \ 104{\ 105 FFTSample _are = (are);\ 106 FFTSample _aim = (aim);\ 107 FFTSample _bre = (bre);\ 108 FFTSample _bim = (bim);\ 109 (pre) = _are * _bre - _aim * _bim;\ 110 (pim) = _are * _bim + _aim * _bre;\ 111} 112 113/** 114 * Compute the middle half of the inverse MDCT of size N = 2^nbits, 115 * thus excluding the parts that can be derived by symmetry 116 * @param output N/2 samples 117 * @param input N/2 samples 118 */ 119void ff_imdct_half_c(MDCTContext *s, FFTSample *output, const FFTSample *input) 120{ 121 int k, n8, n4, n2, n, j; 122 const uint16_t *revtab = s->fft.revtab; 123 const FFTSample *tcos = s->tcos; 124 const FFTSample *tsin = s->tsin; 125 const FFTSample *in1, *in2; 126 FFTComplex *z = (FFTComplex *)output; 127 128 n = 1 << s->nbits; 129 n2 = n >> 1; 130 n4 = n >> 2; 131 n8 = n >> 3; 132 133 /* pre rotation */ 134 in1 = input; 135 in2 = input + n2 - 1; 136 for(k = 0; k < n4; k++) { 137 j=revtab[k]; 138 CMUL(z[j].re, z[j].im, *in2, *in1, tcos[k], tsin[k]); 139 in1 += 2; 140 in2 -= 2; 141 } 142 ff_fft_calc(&s->fft, z); 143 144 /* post rotation + reordering */ 145 output += n4; 146 for(k = 0; k < n8; k++) { 147 FFTSample r0, i0, r1, i1; 148 CMUL(r0, i1, z[n8-k-1].im, z[n8-k-1].re, tsin[n8-k-1], tcos[n8-k-1]); 149 CMUL(r1, i0, z[n8+k ].im, z[n8+k ].re, tsin[n8+k ], tcos[n8+k ]); 150 z[n8-k-1].re = r0; 151 z[n8-k-1].im = i0; 152 z[n8+k ].re = r1; 153 z[n8+k ].im = i1; 154 } 155} 156 157/** 158 * Compute inverse MDCT of size N = 2^nbits 159 * @param output N samples 160 * @param input N/2 samples 161 */ 162void ff_imdct_calc_c(MDCTContext *s, FFTSample *output, const FFTSample *input) 163{ 164 int k; 165 int n = 1 << s->nbits; 166 int n2 = n >> 1; 167 int n4 = n >> 2; 168 169 ff_imdct_half_c(s, output+n4, input); 170 171 for(k = 0; k < n4; k++) { 172 output[k] = -output[n2-k-1]; 173 output[n-k-1] = output[n2+k]; 174 } 175} 176 177/** 178 * Compute MDCT of size N = 2^nbits 179 * @param input N samples 180 * @param out N/2 samples 181 */ 182void ff_mdct_calc(MDCTContext *s, FFTSample *out, const FFTSample *input) 183{ 184 int i, j, n, n8, n4, n2, n3; 185 FFTSample re, im; 186 const uint16_t *revtab = s->fft.revtab; 187 const FFTSample *tcos = s->tcos; 188 const FFTSample *tsin = s->tsin; 189 FFTComplex *x = (FFTComplex *)out; 190 191 n = 1 << s->nbits; 192 n2 = n >> 1; 193 n4 = n >> 2; 194 n8 = n >> 3; 195 n3 = 3 * n4; 196 197 /* pre rotation */ 198 for(i=0;i<n8;i++) { 199 re = -input[2*i+3*n4] - input[n3-1-2*i]; 200 im = -input[n4+2*i] + input[n4-1-2*i]; 201 j = revtab[i]; 202 CMUL(x[j].re, x[j].im, re, im, -tcos[i], tsin[i]); 203 204 re = input[2*i] - input[n2-1-2*i]; 205 im = -(input[n2+2*i] + input[n-1-2*i]); 206 j = revtab[n8 + i]; 207 CMUL(x[j].re, x[j].im, re, im, -tcos[n8 + i], tsin[n8 + i]); 208 } 209 210 ff_fft_calc(&s->fft, x); 211 212 /* post rotation */ 213 for(i=0;i<n8;i++) { 214 FFTSample r0, i0, r1, i1; 215 CMUL(i1, r0, x[n8-i-1].re, x[n8-i-1].im, -tsin[n8-i-1], -tcos[n8-i-1]); 216 CMUL(i0, r1, x[n8+i ].re, x[n8+i ].im, -tsin[n8+i ], -tcos[n8+i ]); 217 x[n8-i-1].re = r0; 218 x[n8-i-1].im = i0; 219 x[n8+i ].re = r1; 220 x[n8+i ].im = i1; 221 } 222} 223 224av_cold void ff_mdct_end(MDCTContext *s) 225{ 226 av_freep(&s->tcos); 227 av_freep(&s->tsin); 228 ff_fft_end(&s->fft); 229} 230