2 * MDCT/IMDCT transforms
3 * Copyright (c) 2002 Fabrice Bellard
5 * This file is part of Libav.
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.
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.
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
24 #include "libavutil/common.h"
25 #include "libavutil/mathematics.h"
27 #include "fft-internal.h"
31 * MDCT/IMDCT transforms.
35 # define RSCALE(x) (x)
37 # define RSCALE(x) ((x) >> 1)
41 * init MDCT or IMDCT computation.
43 av_cold int ff_mdct_init(FFTContext *s, int nbits, int inverse, double scale)
49 memset(s, 0, sizeof(*s));
54 s->mdct_permutation = FF_MDCT_PERM_NONE;
56 if (ff_fft_init(s, s->mdct_bits - 2, inverse) < 0)
59 s->imdct_calc = ff_imdct_calc_c;
60 s->imdct_half = ff_imdct_half_c;
61 s->mdct_calc = ff_mdct_calc_c;
65 ff_mdct_init_aarch64(s);
72 s->mdct_calcw = s->mdct_calc;
74 s->mdct_calcw = ff_mdct_calcw_c;
76 ff_mdct_fixed_init_arm(s);
79 s->tcos = av_malloc(n/2 * sizeof(FFTSample));
83 switch (s->mdct_permutation) {
84 case FF_MDCT_PERM_NONE:
85 s->tsin = s->tcos + n4;
88 case FF_MDCT_PERM_INTERLEAVE:
89 s->tsin = s->tcos + 1;
96 theta = 1.0 / 8.0 + (scale < 0 ? n4 : 0);
97 scale = sqrt(fabs(scale));
99 alpha = 2 * M_PI * (i + theta) / n;
100 s->tcos[i*tstep] = FIX15(-cos(alpha) * scale);
101 s->tsin[i*tstep] = FIX15(-sin(alpha) * scale);
110 * Compute the middle half of the inverse MDCT of size N = 2^nbits,
111 * thus excluding the parts that can be derived by symmetry
112 * @param output N/2 samples
113 * @param input N/2 samples
115 void ff_imdct_half_c(FFTContext *s, FFTSample *output, const FFTSample *input)
117 int k, n8, n4, n2, n, j;
118 const uint16_t *revtab = s->revtab;
119 const FFTSample *tcos = s->tcos;
120 const FFTSample *tsin = s->tsin;
121 const FFTSample *in1, *in2;
122 FFTComplex *z = (FFTComplex *)output;
124 n = 1 << s->mdct_bits;
131 in2 = input + n2 - 1;
132 for(k = 0; k < n4; k++) {
134 CMUL(z[j].re, z[j].im, *in2, *in1, tcos[k], tsin[k]);
140 /* post rotation + reordering */
141 for(k = 0; k < n8; k++) {
142 FFTSample r0, i0, r1, i1;
143 CMUL(r0, i1, z[n8-k-1].im, z[n8-k-1].re, tsin[n8-k-1], tcos[n8-k-1]);
144 CMUL(r1, i0, z[n8+k ].im, z[n8+k ].re, tsin[n8+k ], tcos[n8+k ]);
153 * Compute inverse MDCT of size N = 2^nbits
154 * @param output N samples
155 * @param input N/2 samples
157 void ff_imdct_calc_c(FFTContext *s, FFTSample *output, const FFTSample *input)
160 int n = 1 << s->mdct_bits;
164 ff_imdct_half_c(s, output+n4, input);
166 for(k = 0; k < n4; k++) {
167 output[k] = -output[n2-k-1];
168 output[n-k-1] = output[n2+k];
173 * Compute MDCT of size N = 2^nbits
174 * @param input N samples
175 * @param out N/2 samples
177 void ff_mdct_calc_c(FFTContext *s, FFTSample *out, const FFTSample *input)
179 int i, j, n, n8, n4, n2, n3;
181 const uint16_t *revtab = s->revtab;
182 const FFTSample *tcos = s->tcos;
183 const FFTSample *tsin = s->tsin;
184 FFTComplex *x = (FFTComplex *)out;
186 n = 1 << s->mdct_bits;
194 re = RSCALE(-input[2*i+n3] - input[n3-1-2*i]);
195 im = RSCALE(-input[n4+2*i] + input[n4-1-2*i]);
197 CMUL(x[j].re, x[j].im, re, im, -tcos[i], tsin[i]);
199 re = RSCALE( input[2*i] - input[n2-1-2*i]);
200 im = RSCALE(-input[n2+2*i] - input[ n-1-2*i]);
202 CMUL(x[j].re, x[j].im, re, im, -tcos[n8 + i], tsin[n8 + i]);
209 FFTSample r0, i0, r1, i1;
210 CMUL(i1, r0, x[n8-i-1].re, x[n8-i-1].im, -tsin[n8-i-1], -tcos[n8-i-1]);
211 CMUL(i0, r1, x[n8+i ].re, x[n8+i ].im, -tsin[n8+i ], -tcos[n8+i ]);
219 av_cold void ff_mdct_end(FFTContext *s)