2 * WMA compatible decoder
3 * Copyright (c) 2002 The FFmpeg Project.
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
24 /*these are the sin and cos rotations used by the MDCT*/
26 /*accessed too infrequently to give much speedup in IRAM*/
28 int32_t *tcosarray[5], *tsinarray[5];
29 int32_t tcos0[1024], tcos1[512], tcos2[256], tcos3[128], tcos4[64];
30 int32_t tsin0[1024], tsin1[512], tsin2[256], tsin3[128], tsin4[64];
32 uint16_t revtab0[1024];
35 * init MDCT or IMDCT computation.
37 int ff_mdct_init(MDCTContext *s, int nbits, int inverse)
41 memset(s, 0, sizeof(*s));
42 n = 1 << nbits; /* nbits ranges from 12 to 8 inclusive */
46 s->tcos = tcosarray[12-nbits];
47 s->tsin = tsinarray[12-nbits];
50 int32_t ip = itofix32(i) + 0x2000;
53 /*I can't remember why this works, but it seems
54 to agree for ~24 bits, maybe more!*/
55 s->tsin[i] = - fsincos(ip<<16, &(s->tcos[i]));
59 (&s->fft)->nbits = nbits-2;
60 (&s->fft)->inverse = inverse;
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,
76 int k, n8, n4, n2, n, j,scale;
77 const int32_t *tcos = s->tcos;
78 const int32_t *tsin = s->tsin;
79 const int32_t *in1, *in2;
80 FFTComplex *z1 = (FFTComplex *)output;
81 FFTComplex *z2 = (FFTComplex *)input;
82 int revtabshift = 12 - s->nbits;
94 for(k = 0; k < n4; k++)
96 j=revtab0[k<<revtabshift];
97 CMUL(&z1[j].re, &z1[j].im, *in2, *in1, tcos[k], tsin[k]);
102 scale = fft_calc_unscaled(&s->fft, z1);
104 /* post rotation + reordering */
105 for(k = 0; k < n4; k++)
107 CMUL(&z2[k].re, &z2[k].im, (z1[k].re), (z1[k].im), tcos[k], tsin[k]);
110 for(k = 0; k < n8; k++)
112 int32_t r1,r2,r3,r4,r1n,r2n,r3n;
123 output[n2-1-2*k] = r1;
126 output[n2-1-2*k-1] = r2n;
128 output[n2 + 2*k]= r3n;
129 output[n-1- 2*k]= r3n;
131 output[n2 + 2*k+1]= r4;
132 output[n-2 - 2 * k] = r4;
138 int mdct_init_global(void)
142 /* although seemingly degenerate, these cannot actually be merged together without
143 a substantial increase in error which is unjustified by the tiny memory savings*/
145 tcosarray[0] = tcos0; tcosarray[1] = tcos1; tcosarray[2] = tcos2; tcosarray[3] = tcos3;tcosarray[4] = tcos4;
146 tsinarray[0] = tsin0; tsinarray[1] = tsin1; tsinarray[2] = tsin2; tsinarray[3] = tsin3;tsinarray[4] = tsin4;
148 /* init the MDCT bit reverse table here rather then in fft_init */
150 for(i=0;i<1024;i++) /*hard coded to a 2048 bit rotation*/
151 { /*smaller sizes can reuse the largest*/
155 m |= ((i >> j) & 1) << (10-j-1);