1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
|
/*
* MDCT/IMDCT transforms
* Copyright (c) 2002 Fabrice Bellard.
*
* This file is part of FFmpeg.
*
* FFmpeg is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* FFmpeg is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with FFmpeg; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
#include "dsputil.h"
/**
* @file mdct.c
* MDCT/IMDCT transforms.
*/
// Generate a Kaiser-Bessel Derived Window.
#define BESSEL_I0_ITER 50 // default: 50 iterations of Bessel I0 approximation
void ff_kbd_window_init(float *window, float alpha, int n)
{
int i, j;
double sum = 0.0, bessel, tmp;
double local_window[n];
double alpha2 = (alpha * M_PI / n) * (alpha * M_PI / n);
for (i = 0; i < n; i++) {
tmp = i * (n - i) * alpha2;
bessel = 1.0;
for (j = BESSEL_I0_ITER; j > 0; j--)
bessel = bessel * tmp / (j * j) + 1;
sum += bessel;
local_window[i] = sum;
}
sum++;
for (i = 0; i < n; i++)
window[i] = sqrt(local_window[i] / sum);
}
// Generate a sine window.
void ff_sine_window_init(float *window, int n) {
int i;
for(i = 0; i < n; i++)
window[i] = sin((i + 0.5) / (2 * n) * M_PI);
}
/**
* init MDCT or IMDCT computation.
*/
int ff_mdct_init(MDCTContext *s, int nbits, int inverse)
{
int n, n4, i;
double alpha;
memset(s, 0, sizeof(*s));
n = 1 << nbits;
s->nbits = nbits;
s->n = n;
n4 = n >> 2;
s->tcos = av_malloc(n4 * sizeof(FFTSample));
if (!s->tcos)
goto fail;
s->tsin = av_malloc(n4 * sizeof(FFTSample));
if (!s->tsin)
goto fail;
for(i=0;i<n4;i++) {
alpha = 2 * M_PI * (i + 1.0 / 8.0) / n;
s->tcos[i] = -cos(alpha);
s->tsin[i] = -sin(alpha);
}
if (ff_fft_init(&s->fft, s->nbits - 2, inverse) < 0)
goto fail;
return 0;
fail:
av_freep(&s->tcos);
av_freep(&s->tsin);
return -1;
}
/* complex multiplication: p = a * b */
#define CMUL(pre, pim, are, aim, bre, bim) \
{\
double _are = (are);\
double _aim = (aim);\
double _bre = (bre);\
double _bim = (bim);\
(pre) = _are * _bre - _aim * _bim;\
(pim) = _are * _bim + _aim * _bre;\
}
/**
* Compute the middle half of the inverse MDCT of size N = 2^nbits,
* thus excluding the parts that can be derived by symmetry
* @param output N/2 samples
* @param input N/2 samples
*/
void ff_imdct_half(MDCTContext *s, FFTSample *output, const FFTSample *input)
{
int k, n8, n4, n2, n, j;
const uint16_t *revtab = s->fft.revtab;
const FFTSample *tcos = s->tcos;
const FFTSample *tsin = s->tsin;
const FFTSample *in1, *in2;
FFTComplex *z = (FFTComplex *)output;
n = 1 << s->nbits;
n2 = n >> 1;
n4 = n >> 2;
n8 = n >> 3;
/* pre rotation */
in1 = input;
in2 = input + n2 - 1;
for(k = 0; k < n4; k++) {
j=revtab[k];
CMUL(z[j].re, z[j].im, *in2, *in1, tcos[k], tsin[k]);
in1 += 2;
in2 -= 2;
}
ff_fft_calc(&s->fft, z);
/* post rotation + reordering */
output += n4;
for(k = 0; k < n8; k++) {
FFTSample r0, i0, r1, i1;
CMUL(r0, i1, z[n8-k-1].im, z[n8-k-1].re, tsin[n8-k-1], tcos[n8-k-1]);
CMUL(r1, i0, z[n8+k ].im, z[n8+k ].re, tsin[n8+k ], tcos[n8+k ]);
z[n8-k-1].re = r0;
z[n8-k-1].im = i0;
z[n8+k ].re = r1;
z[n8+k ].im = i1;
}
}
/**
* Compute inverse MDCT of size N = 2^nbits
* @param output N samples
* @param input N/2 samples
* @param tmp N/2 samples
*/
void ff_imdct_calc(MDCTContext *s, FFTSample *output,
const FFTSample *input, FFTSample *tmp)
{
int k;
int n = 1 << s->nbits;
int n2 = n >> 1;
int n4 = n >> 2;
ff_imdct_half(s, output+n4, input);
for(k = 0; k < n4; k++) {
output[k] = -output[n2-k-1];
output[n-k-1] = output[n2+k];
}
}
/**
* Compute MDCT of size N = 2^nbits
* @param input N samples
* @param out N/2 samples
* @param tmp temporary storage of N/2 samples
*/
void ff_mdct_calc(MDCTContext *s, FFTSample *out,
const FFTSample *input, FFTSample *tmp)
{
int i, j, n, n8, n4, n2, n3;
FFTSample re, im, re1, im1;
const uint16_t *revtab = s->fft.revtab;
const FFTSample *tcos = s->tcos;
const FFTSample *tsin = s->tsin;
FFTComplex *x = (FFTComplex *)out;
n = 1 << s->nbits;
n2 = n >> 1;
n4 = n >> 2;
n8 = n >> 3;
n3 = 3 * n4;
/* pre rotation */
for(i=0;i<n8;i++) {
re = -input[2*i+3*n4] - input[n3-1-2*i];
im = -input[n4+2*i] + input[n4-1-2*i];
j = revtab[i];
CMUL(x[j].re, x[j].im, re, im, -tcos[i], tsin[i]);
re = input[2*i] - input[n2-1-2*i];
im = -(input[n2+2*i] + input[n-1-2*i]);
j = revtab[n8 + i];
CMUL(x[j].re, x[j].im, re, im, -tcos[n8 + i], tsin[n8 + i]);
}
ff_fft_calc(&s->fft, x);
/* post rotation */
for(i=0;i<n8;i++) {
FFTSample r0, i0, r1, i1;
CMUL(i1, r0, x[n8-i-1].re, x[n8-i-1].im, -tsin[n8-i-1], -tcos[n8-i-1]);
CMUL(i0, r1, x[n8+i ].re, x[n8+i ].im, -tsin[n8+i ], -tcos[n8+i ]);
x[n8-i-1].re = r0;
x[n8-i-1].im = i0;
x[n8+i ].re = r1;
x[n8+i ].im = i1;
}
}
void ff_mdct_end(MDCTContext *s)
{
av_freep(&s->tcos);
av_freep(&s->tsin);
ff_fft_end(&s->fft);
}
|
