2 * MDCT/IMDCT transforms
3 * Copyright (c) 2002 Fabrice Bellard.
5 * This library is free software; you can redistribute it and/or
6 * modify it under the terms of the GNU Lesser General Public
7 * License as published by the Free Software Foundation; either
8 * version 2 of the License, or (at your option) any later version.
10 * This library is distributed in the hope that it will be useful,
11 * but WITHOUT ANY WARRANTY; without even the implied warranty of
12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 * Lesser General Public License for more details.
15 * You should have received a copy of the GNU Lesser General Public
16 * License along with this library; if not, write to the Free Software
17 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
22 * init MDCT or IMDCT computation
24 int ff_mdct_init(MDCTContext *s, int nbits, int inverse)
29 memset(s, 0, sizeof(*s));
34 s->tcos = malloc(n4 * sizeof(FFTSample));
37 s->tsin = malloc(n4 * sizeof(FFTSample));
42 alpha = 2 * M_PI * (i + 1.0 / 8.0) / n;
43 s->tcos[i] = -cos(alpha);
44 s->tsin[i] = -sin(alpha);
46 if (fft_init(&s->fft, s->nbits - 2, inverse) < 0)
55 /* complex multiplication: p = a * b */
56 #define CMUL(pre, pim, are, aim, bre, bim) \
62 (pre) = _are * _bre - _aim * _bim;\
63 (pim) = _are * _bim + _aim * _bre;\
67 * Compute inverse MDCT of size N = 2^nbits
68 * @param output N samples
69 * @param input N/2 samples
70 * @param tmp N/2 samples
72 void ff_imdct_calc(MDCTContext *s, FFTSample *output,
73 const FFTSample *input, FFTSample *tmp)
75 int k, n8, n4, n2, n, j;
76 const uint16_t *revtab = s->fft.revtab;
77 const FFTSample *tcos = s->tcos;
78 const FFTSample *tsin = s->tsin;
79 const FFTSample *in1, *in2;
80 FFTComplex *z = (FFTComplex *)tmp;
90 for(k = 0; k < n4; k++) {
92 CMUL(z[j].re, z[j].im, *in2, *in1, tcos[k], tsin[k]);
98 /* post rotation + reordering */
100 for(k = 0; k < n4; k++) {
101 CMUL(z[k].re, z[k].im, z[k].re, z[k].im, tcos[k], tsin[k]);
103 for(k = 0; k < n8; k++) {
104 output[2*k] = -z[n8 + k].im;
105 output[n2-1-2*k] = z[n8 + k].im;
107 output[2*k+1] = z[n8-1-k].re;
108 output[n2-1-2*k-1] = -z[n8-1-k].re;
110 output[n2 + 2*k]=-z[k+n8].re;
111 output[n-1- 2*k]=-z[k+n8].re;
113 output[n2 + 2*k+1]=z[n8-k-1].im;
114 output[n-2 - 2 * k] = z[n8-k-1].im;
119 * Compute MDCT of size N = 2^nbits
120 * @param input N samples
121 * @param out N/2 samples
122 * @param tmp temporary storage of N/2 samples
124 void ff_mdct_calc(MDCTContext *s, FFTSample *out,
125 const FFTSample *input, FFTSample *tmp)
127 int i, j, n, n8, n4, n2, n3;
128 FFTSample re, im, re1, im1;
129 const uint16_t *revtab = s->fft.revtab;
130 const FFTSample *tcos = s->tcos;
131 const FFTSample *tsin = s->tsin;
132 FFTComplex *x = (FFTComplex *)tmp;
142 re = -input[2*i+3*n4] - input[n3-1-2*i];
143 im = -input[n4+2*i] + input[n4-1-2*i];
145 CMUL(x[j].re, x[j].im, re, im, -tcos[i], tsin[i]);
147 re = input[2*i] - input[n2-1-2*i];
148 im = -(input[n2+2*i] + input[n-1-2*i]);
150 CMUL(x[j].re, x[j].im, re, im, -tcos[n8 + i], tsin[n8 + i]);
153 fft_calc(&s->fft, x);
159 CMUL(re1, im1, re, im, -tsin[i], -tcos[i]);
165 void ff_mdct_end(MDCTContext *s)