ffmpeg/libavcodec/mdct_template.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 #include "fft-internal.h"
  28
  29 /**
  30  * @file
  31  * MDCT/IMDCT transforms.
  32  */
  33
  34 #if FFT_FLOAT
  35 #   define RSCALE(x) (x)
  36 #else
  37 #if FFT_FIXED_32
  38 #   define RSCALE(x) (((x) + 32) >> 6)
  39 #else /* FFT_FIXED_32 */
  40 #   define RSCALE(x) ((x) >> 1)
  41 #endif /* FFT_FIXED_32 */
  42 #endif
  43
  44 /**
  45  * init MDCT or IMDCT computation.
  46  */
  47 av_cold int ff_mdct_init(FFTContext *s, int nbits, int inverse, double scale)
  48 {
  49     int n, n4, i;
  50     double alpha, theta;
  51     int tstep;
  52
  53     memset(s, 0, sizeof(*s));
  54     n = 1 << nbits;
  55     s->mdct_bits = nbits;
  56     s->mdct_size = n;
  57     n4 = n >> 2;
  58     s->mdct_permutation = FF_MDCT_PERM_NONE;
  59
  60     if (ff_fft_init(s, s->mdct_bits - 2, inverse) < 0)
  61         goto fail;
  62
  63     s->tcos = av_malloc_array(n/2, sizeof(FFTSample));
  64     if (!s->tcos)
  65         goto fail;
  66
  67     switch (s->mdct_permutation) {
  68     case FF_MDCT_PERM_NONE:
  69         s->tsin = s->tcos + n4;
  70         tstep = 1;
  71         break;
  72     case FF_MDCT_PERM_INTERLEAVE:
  73         s->tsin = s->tcos + 1;
  74         tstep = 2;
  75         break;
  76     default:
  77         goto fail;
  78     }
  79
  80     theta = 1.0 / 8.0 + (scale < 0 ? n4 : 0);
  81     scale = sqrt(fabs(scale));
  82     for(i=0;i<n4;i++) {
  83         alpha = 2 * M_PI * (i + theta) / n;
  84         s->tcos[i*tstep] = FIX15(-cos(alpha) * scale);
  85         s->tsin[i*tstep] = FIX15(-sin(alpha) * scale);
  86     }
  87     return 0;
  88  fail:
  89     ff_mdct_end(s);
  90     return -1;
  91 }
  92
  93 /**
  94  * Compute the middle half of the inverse MDCT of size N = 2^nbits,
  95  * thus excluding the parts that can be derived by symmetry
  96  * @param output N/2 samples
  97  * @param input N/2 samples
  98  */
  99 void ff_imdct_half_c(FFTContext *s, FFTSample *output, const FFTSample *input)
 100 {
 101     int k, n8, n4, n2, n, j;
 102     const uint16_t *revtab = s->revtab;
 103     const FFTSample *tcos = s->tcos;
 104     const FFTSample *tsin = s->tsin;
 105     const FFTSample *in1, *in2;
 106     FFTComplex *z = (FFTComplex *)output;
 107
 108     n = 1 << s->mdct_bits;
 109     n2 = n >> 1;
 110     n4 = n >> 2;
 111     n8 = n >> 3;
 112
 113     /* pre rotation */
 114     in1 = input;
 115     in2 = input + n2 - 1;
 116     for(k = 0; k < n4; k++) {
 117         j=revtab[k];
 118         CMUL(z[j].re, z[j].im, *in2, *in1, tcos[k], tsin[k]);
 119         in1 += 2;
 120         in2 -= 2;
 121     }
 122     s->fft_calc(s, z);
 123
 124     /* post rotation + reordering */
 125     for(k = 0; k < n8; k++) {
 126         FFTSample r0, i0, r1, i1;
 127         CMUL(r0, i1, z[n8-k-1].im, z[n8-k-1].re, tsin[n8-k-1], tcos[n8-k-1]);
 128         CMUL(r1, i0, z[n8+k  ].im, z[n8+k  ].re, tsin[n8+k  ], tcos[n8+k  ]);
 129         z[n8-k-1].re = r0;
 130         z[n8-k-1].im = i0;
 131         z[n8+k  ].re = r1;
 132         z[n8+k  ].im = i1;
 133     }
 134 }
 135
 136 /**
 137  * Compute inverse MDCT of size N = 2^nbits
 138  * @param output N samples
 139  * @param input N/2 samples
 140  */
 141 void ff_imdct_calc_c(FFTContext *s, FFTSample *output, const FFTSample *input)
 142 {
 143     int k;
 144     int n = 1 << s->mdct_bits;
 145     int n2 = n >> 1;
 146     int n4 = n >> 2;
 147
 148     ff_imdct_half_c(s, output+n4, input);
 149
 150     for(k = 0; k < n4; k++) {
 151         output[k] = -output[n2-k-1];
 152         output[n-k-1] = output[n2+k];
 153     }
 154 }
 155
 156 /**
 157  * Compute MDCT of size N = 2^nbits
 158  * @param input N samples
 159  * @param out N/2 samples
 160  */
 161 void ff_mdct_calc_c(FFTContext *s, FFTSample *out, const FFTSample *input)
 162 {
 163     int i, j, n, n8, n4, n2, n3;
 164     FFTDouble re, im;
 165     const uint16_t *revtab = s->revtab;
 166     const FFTSample *tcos = s->tcos;
 167     const FFTSample *tsin = s->tsin;
 168     FFTComplex *x = (FFTComplex *)out;
 169
 170     n = 1 << s->mdct_bits;
 171     n2 = n >> 1;
 172     n4 = n >> 2;
 173     n8 = n >> 3;
 174     n3 = 3 * n4;
 175
 176     /* pre rotation */
 177     for(i=0;i<n8;i++) {
 178         re = RSCALE(-input[2*i+n3] - input[n3-1-2*i]);
 179         im = RSCALE(-input[n4+2*i] + input[n4-1-2*i]);
 180         j = revtab[i];
 181         CMUL(x[j].re, x[j].im, re, im, -tcos[i], tsin[i]);
 182
 183         re = RSCALE( input[2*i]    - input[n2-1-2*i]);
 184         im = RSCALE(-input[n2+2*i] - input[ n-1-2*i]);
 185         j = revtab[n8 + i];
 186         CMUL(x[j].re, x[j].im, re, im, -tcos[n8 + i], tsin[n8 + i]);
 187     }
 188
 189     s->fft_calc(s, x);
 190
 191     /* post rotation */
 192     for(i=0;i<n8;i++) {
 193         FFTSample r0, i0, r1, i1;
 194         CMUL(i1, r0, x[n8-i-1].re, x[n8-i-1].im, -tsin[n8-i-1], -tcos[n8-i-1]);
 195         CMUL(i0, r1, x[n8+i  ].re, x[n8+i  ].im, -tsin[n8+i  ], -tcos[n8+i  ]);
 196         x[n8-i-1].re = r0;
 197         x[n8-i-1].im = i0;
 198         x[n8+i  ].re = r1;
 199         x[n8+i  ].im = i1;
 200     }
 201 }
 202
 203 av_cold void ff_mdct_end(FFTContext *s)
 204 {
 205     av_freep(&s->tcos);
 206     ff_fft_end(s);
 207 }