2 * MDCT/IMDCT transforms
3 * Copyright (c) 2002 Fabrice Bellard
5 * This file is part of FFmpeg.
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.
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.
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
24 * @file libavcodec/mdct.c
25 * MDCT/IMDCT transforms.
28 // Generate a Kaiser-Bessel Derived Window.
29 #define BESSEL_I0_ITER 50 // default: 50 iterations of Bessel I0 approximation
30 av_cold
void ff_kbd_window_init(float *window
, float alpha
, int n
)
33 double sum
= 0.0, bessel
, tmp
;
34 double local_window
[n
];
35 double alpha2
= (alpha
* M_PI
/ n
) * (alpha
* M_PI
/ n
);
37 for (i
= 0; i
< n
; i
++) {
38 tmp
= i
* (n
- i
) * alpha2
;
40 for (j
= BESSEL_I0_ITER
; j
> 0; j
--)
41 bessel
= bessel
* tmp
/ (j
* j
) + 1;
43 local_window
[i
] = sum
;
47 for (i
= 0; i
< n
; i
++)
48 window
[i
] = sqrt(local_window
[i
] / sum
);
51 DECLARE_ALIGNED(16, float, ff_sine_32
[ 32]);
52 DECLARE_ALIGNED(16, float, ff_sine_64
[ 64]);
53 DECLARE_ALIGNED(16, float, ff_sine_128
[ 128]);
54 DECLARE_ALIGNED(16, float, ff_sine_256
[ 256]);
55 DECLARE_ALIGNED(16, float, ff_sine_512
[ 512]);
56 DECLARE_ALIGNED(16, float, ff_sine_1024
[1024]);
57 DECLARE_ALIGNED(16, float, ff_sine_2048
[2048]);
58 DECLARE_ALIGNED(16, float, ff_sine_4096
[4096]);
59 float * const ff_sine_windows
[] = {
60 NULL
, NULL
, NULL
, NULL
, NULL
, // unused
61 ff_sine_32
, ff_sine_64
,
62 ff_sine_128
, ff_sine_256
, ff_sine_512
, ff_sine_1024
, ff_sine_2048
, ff_sine_4096
65 // Generate a sine window.
66 av_cold
void ff_sine_window_init(float *window
, int n
) {
68 for(i
= 0; i
< n
; i
++)
69 window
[i
] = sinf((i
+ 0.5) * (M_PI
/ (2.0 * n
)));
73 * init MDCT or IMDCT computation.
75 av_cold
int ff_mdct_init(MDCTContext
*s
, int nbits
, int inverse
, double scale
)
80 memset(s
, 0, sizeof(*s
));
85 s
->tcos
= av_malloc(n4
* sizeof(FFTSample
));
88 s
->tsin
= av_malloc(n4
* sizeof(FFTSample
));
92 theta
= 1.0 / 8.0 + (scale
< 0 ? n4
: 0);
93 scale
= sqrt(fabs(scale
));
95 alpha
= 2 * M_PI
* (i
+ theta
) / n
;
96 s
->tcos
[i
] = -cos(alpha
) * scale
;
97 s
->tsin
[i
] = -sin(alpha
) * scale
;
99 if (ff_fft_init(&s
->fft
, s
->nbits
- 2, inverse
) < 0)
108 /* complex multiplication: p = a * b */
109 #define CMUL(pre, pim, are, aim, bre, bim) \
111 FFTSample _are = (are);\
112 FFTSample _aim = (aim);\
113 FFTSample _bre = (bre);\
114 FFTSample _bim = (bim);\
115 (pre) = _are * _bre - _aim * _bim;\
116 (pim) = _are * _bim + _aim * _bre;\
120 * Compute the middle half of the inverse MDCT of size N = 2^nbits,
121 * thus excluding the parts that can be derived by symmetry
122 * @param output N/2 samples
123 * @param input N/2 samples
125 void ff_imdct_half_c(MDCTContext
*s
, FFTSample
*output
, const FFTSample
*input
)
127 int k
, n8
, n4
, n2
, n
, j
;
128 const uint16_t *revtab
= s
->fft
.revtab
;
129 const FFTSample
*tcos
= s
->tcos
;
130 const FFTSample
*tsin
= s
->tsin
;
131 const FFTSample
*in1
, *in2
;
132 FFTComplex
*z
= (FFTComplex
*)output
;
141 in2
= input
+ n2
- 1;
142 for(k
= 0; k
< n4
; k
++) {
144 CMUL(z
[j
].re
, z
[j
].im
, *in2
, *in1
, tcos
[k
], tsin
[k
]);
148 ff_fft_calc(&s
->fft
, z
);
150 /* post rotation + reordering */
151 for(k
= 0; k
< n8
; k
++) {
152 FFTSample r0
, i0
, r1
, i1
;
153 CMUL(r0
, i1
, z
[n8
-k
-1].im
, z
[n8
-k
-1].re
, tsin
[n8
-k
-1], tcos
[n8
-k
-1]);
154 CMUL(r1
, i0
, z
[n8
+k
].im
, z
[n8
+k
].re
, tsin
[n8
+k
], tcos
[n8
+k
]);
163 * Compute inverse MDCT of size N = 2^nbits
164 * @param output N samples
165 * @param input N/2 samples
167 void ff_imdct_calc_c(MDCTContext
*s
, FFTSample
*output
, const FFTSample
*input
)
170 int n
= 1 << s
->nbits
;
174 ff_imdct_half_c(s
, output
+n4
, input
);
176 for(k
= 0; k
< n4
; k
++) {
177 output
[k
] = -output
[n2
-k
-1];
178 output
[n
-k
-1] = output
[n2
+k
];
183 * Compute MDCT of size N = 2^nbits
184 * @param input N samples
185 * @param out N/2 samples
187 void ff_mdct_calc_c(MDCTContext
*s
, FFTSample
*out
, const FFTSample
*input
)
189 int i
, j
, n
, n8
, n4
, n2
, n3
;
191 const uint16_t *revtab
= s
->fft
.revtab
;
192 const FFTSample
*tcos
= s
->tcos
;
193 const FFTSample
*tsin
= s
->tsin
;
194 FFTComplex
*x
= (FFTComplex
*)out
;
204 re
= -input
[2*i
+3*n4
] - input
[n3
-1-2*i
];
205 im
= -input
[n4
+2*i
] + input
[n4
-1-2*i
];
207 CMUL(x
[j
].re
, x
[j
].im
, re
, im
, -tcos
[i
], tsin
[i
]);
209 re
= input
[2*i
] - input
[n2
-1-2*i
];
210 im
= -(input
[n2
+2*i
] + input
[n
-1-2*i
]);
212 CMUL(x
[j
].re
, x
[j
].im
, re
, im
, -tcos
[n8
+ i
], tsin
[n8
+ i
]);
215 ff_fft_calc(&s
->fft
, x
);
219 FFTSample r0
, i0
, r1
, i1
;
220 CMUL(i1
, r0
, x
[n8
-i
-1].re
, x
[n8
-i
-1].im
, -tsin
[n8
-i
-1], -tcos
[n8
-i
-1]);
221 CMUL(i0
, r1
, x
[n8
+i
].re
, x
[n8
+i
].im
, -tsin
[n8
+i
], -tcos
[n8
+i
]);
229 av_cold
void ff_mdct_end(MDCTContext
*s
)