| 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 | } |