apps/codecs/libwmapro/mdct.c

   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
  22 #include <stdlib.h>
  23 #include <string.h>
  24 #include "libavutil/common.h"
  25 #include "libavutil/mathematics.h"
  26 #include "fft.h"
  27
  28 /**
  29  * @file libavcodec/mdct.c
  30  * MDCT/IMDCT transforms.
  31  */
  32
  33 // Generate a Kaiser-Bessel Derived Window.
  34 #define BESSEL_I0_ITER 50 // default: 50 iterations of Bessel I0 approximation
  35 av_cold void ff_kbd_window_init(float *window, float alpha, int n)
  36 {
  37    int i, j;
  38    double sum = 0.0, bessel, tmp;
  39    double local_window[n];
  40    double alpha2 = (alpha * M_PI / n) * (alpha * M_PI / n);
  41
  42    for (i = 0; i < n; i++) {
  43        tmp = i * (n - i) * alpha2;
  44        bessel = 1.0;
  45        for (j = BESSEL_I0_ITER; j > 0; j--)
  46            bessel = bessel * tmp / (j * j) + 1;
  47        sum += bessel;
  48        local_window[i] = sum;
  49    }
  50
  51    sum++;
  52    for (i = 0; i < n; i++)
  53        window[i] = sqrt(local_window[i] / sum);
  54 }
  55
  56 #include "mdct_tablegen.h"
  57
  58 /**
  59  * init MDCT or IMDCT computation.
  60  */
  61 av_cold int ff_mdct_init(FFTContext *s, int nbits, int inverse, double scale)
  62 {
  63     int n, n4, i;
  64     double alpha, theta;
  65     int tstep;
  66
  67     memset(s, 0, sizeof(*s));
  68     n = 1 << nbits;
  69     s->mdct_bits = nbits;
  70     s->mdct_size = n;
  71     n4 = n >> 2;
  72     s->permutation = FF_MDCT_PERM_NONE;
  73
  74     if (ff_fft_init(s, s->mdct_bits - 2, inverse) < 0)
  75         goto fail;
  76
  77     s->tcos = av_malloc(n/2 * sizeof(FFTSample));
  78     if (!s->tcos)
  79         goto fail;
  80
  81     switch (s->permutation) {
  82     case FF_MDCT_PERM_NONE:
  83         s->tsin = s->tcos + n4;
  84         tstep = 1;
  85         break;
  86     case FF_MDCT_PERM_INTERLEAVE:
  87         s->tsin = s->tcos + 1;
  88         tstep = 2;
  89         break;
  90     default:
  91         goto fail;
  92     }
  93
  94     theta = 1.0 / 8.0 + (scale < 0 ? n4 : 0);
  95     scale = sqrt(fabs(scale));
  96     for(i=0;i<n4;i++) {
  97         alpha = 2 * M_PI * (i + theta) / n;
  98         s->tcos[i*tstep] = -cos(alpha) * scale;
  99         s->tsin[i*tstep] = -sin(alpha) * scale;
 100     }
 101     return 0;
 102  fail:
 103     ff_mdct_end(s);
 104     return -1;
 105 }
 106
 107 /* complex multiplication: p = a * b */
 108 #define CMUL(pre, pim, are, aim, bre, bim) \
 109 {\
 110     FFTSample _are = (are);\
 111     FFTSample _aim = (aim);\
 112     FFTSample _bre = (bre);\
 113     FFTSample _bim = (bim);\
 114     (pre) = _are * _bre - _aim * _bim;\
 115     (pim) = _are * _bim + _aim * _bre;\
 116 }
 117
 118 /**
 119  * Compute the middle half of the inverse MDCT of size N = 2^nbits,
 120  * thus excluding the parts that can be derived by symmetry
 121  * @param output N/2 samples
 122  * @param input N/2 samples
 123  */
 124 void ff_imdct_half_c(FFTContext *s, FFTSample *output, const FFTSample *input)
 125 {
 126     int k, n8, n4, n2, n, j;
 127     const uint16_t *revtab = s->revtab;
 128     const FFTSample *tcos = s->tcos;
 129     const FFTSample *tsin = s->tsin;
 130     const FFTSample *in1, *in2;
 131     FFTComplex *z = (FFTComplex *)output;
 132
 133     n = 1 << s->mdct_bits;
 134     n2 = n >> 1;
 135     n4 = n >> 2;
 136     n8 = n >> 3;
 137
 138     /* pre rotation */
 139     in1 = input;
 140     in2 = input + n2 - 1;
 141     for(k = 0; k < n4; k++) {
 142         j=revtab[k];
 143         CMUL(z[j].re, z[j].im, *in2, *in1, tcos[k], tsin[k]);
 144         in1 += 2;
 145         in2 -= 2;
 146     }
 147     ff_fft_calc(s, z);
 148
 149     /* post rotation + reordering */
 150     for(k = 0; k < n8; k++) {
 151         FFTSample r0, i0, r1, i1;
 152         CMUL(r0, i1, z[n8-k-1].im, z[n8-k-1].re, tsin[n8-k-1], tcos[n8-k-1]);
 153         CMUL(r1, i0, z[n8+k  ].im, z[n8+k  ].re, tsin[n8+k  ], tcos[n8+k  ]);
 154         z[n8-k-1].re = r0;
 155         z[n8-k-1].im = i0;
 156         z[n8+k  ].re = r1;
 157         z[n8+k  ].im = i1;
 158     }
 159 }
 160
 161 /**
 162  * Compute inverse MDCT of size N = 2^nbits
 163  * @param output N samples
 164  * @param input N/2 samples
 165  */
 166 void ff_imdct_calc_c(FFTContext *s, FFTSample *output, const FFTSample *input)
 167 {
 168     int k;
 169     int n = 1 << s->mdct_bits;
 170     int n2 = n >> 1;
 171     int n4 = n >> 2;
 172
 173     ff_imdct_half_c(s, output+n4, input);
 174
 175     for(k = 0; k < n4; k++) {
 176         output[k] = -output[n2-k-1];
 177         output[n-k-1] = output[n2+k];
 178     }
 179 }
 180
 181 /**
 182  * Compute MDCT of size N = 2^nbits
 183  * @param input N samples
 184  * @param out N/2 samples
 185  */
 186 void ff_mdct_calc_c(FFTContext *s, FFTSample *out, const FFTSample *input)
 187 {
 188     int i, j, n, n8, n4, n2, n3;
 189     FFTSample re, im;
 190     const uint16_t *revtab = s->revtab;
 191     const FFTSample *tcos = s->tcos;
 192     const FFTSample *tsin = s->tsin;
 193     FFTComplex *x = (FFTComplex *)out;
 194
 195     n = 1 << s->mdct_bits;
 196     n2 = n >> 1;
 197     n4 = n >> 2;
 198     n8 = n >> 3;
 199     n3 = 3 * n4;
 200
 201     /* pre rotation */
 202     for(i=0;i<n8;i++) {
 203         re = -input[2*i+3*n4] - input[n3-1-2*i];
 204         im = -input[n4+2*i] + input[n4-1-2*i];
 205         j = revtab[i];
 206         CMUL(x[j].re, x[j].im, re, im, -tcos[i], tsin[i]);
 207
 208         re = input[2*i] - input[n2-1-2*i];
 209         im = -(input[n2+2*i] + input[n-1-2*i]);
 210         j = revtab[n8 + i];
 211         CMUL(x[j].re, x[j].im, re, im, -tcos[n8 + i], tsin[n8 + i]);
 212     }
 213
 214     ff_fft_calc(s, x);
 215
 216     /* post rotation */
 217     for(i=0;i<n8;i++) {
 218         FFTSample r0, i0, r1, i1;
 219         CMUL(i1, r0, x[n8-i-1].re, x[n8-i-1].im, -tsin[n8-i-1], -tcos[n8-i-1]);
 220         CMUL(i0, r1, x[n8+i  ].re, x[n8+i  ].im, -tsin[n8+i  ], -tcos[n8+i  ]);
 221         x[n8-i-1].re = r0;
 222         x[n8-i-1].im = i0;
 223         x[n8+i  ].re = r1;
 224         x[n8+i  ].im = i1;
 225     }
 226 }
 227
 228 av_cold void ff_mdct_end(FFTContext *s)
 229 {
 230     av_freep(&s->tcos);
 231     ff_fft_end(s);
 232 }