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
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 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_128
[ 128]);
52 DECLARE_ALIGNED(16, float, ff_sine_256
[ 256]);
53 DECLARE_ALIGNED(16, float, ff_sine_512
[ 512]);
54 DECLARE_ALIGNED(16, float, ff_sine_1024
[1024]);
55 DECLARE_ALIGNED(16, float, ff_sine_2048
[2048]);
56 float *ff_sine_windows
[5] = {
57 ff_sine_128
, ff_sine_256
, ff_sine_512
, ff_sine_1024
, ff_sine_2048
,
60 // Generate a sine window.
61 void ff_sine_window_init(float *window
, int n
) {
63 for(i
= 0; i
< n
; i
++)
64 window
[i
] = sinf((i
+ 0.5) * (M_PI
/ (2.0 * n
)));
68 * init MDCT or IMDCT computation.
70 int ff_mdct_init(MDCTContext
*s
, int nbits
, int inverse
)
75 memset(s
, 0, sizeof(*s
));
80 s
->tcos
= av_malloc(n4
* sizeof(FFTSample
));
83 s
->tsin
= av_malloc(n4
* sizeof(FFTSample
));
88 alpha
= 2 * M_PI
* (i
+ 1.0 / 8.0) / n
;
89 s
->tcos
[i
] = -cos(alpha
);
90 s
->tsin
[i
] = -sin(alpha
);
92 if (ff_fft_init(&s
->fft
, s
->nbits
- 2, inverse
) < 0)
101 /* complex multiplication: p = a * b */
102 #define CMUL(pre, pim, are, aim, bre, bim) \
104 FFTSample _are = (are);\
105 FFTSample _aim = (aim);\
106 FFTSample _bre = (bre);\
107 FFTSample _bim = (bim);\
108 (pre) = _are * _bre - _aim * _bim;\
109 (pim) = _are * _bim + _aim * _bre;\
113 * Compute the middle half of the inverse MDCT of size N = 2^nbits,
114 * thus excluding the parts that can be derived by symmetry
115 * @param output N/2 samples
116 * @param input N/2 samples
118 void ff_imdct_half_c(MDCTContext
*s
, FFTSample
*output
, const FFTSample
*input
)
120 int k
, n8
, n4
, n2
, n
, j
;
121 const uint16_t *revtab
= s
->fft
.revtab
;
122 const FFTSample
*tcos
= s
->tcos
;
123 const FFTSample
*tsin
= s
->tsin
;
124 const FFTSample
*in1
, *in2
;
125 FFTComplex
*z
= (FFTComplex
*)output
;
134 in2
= input
+ n2
- 1;
135 for(k
= 0; k
< n4
; k
++) {
137 CMUL(z
[j
].re
, z
[j
].im
, *in2
, *in1
, tcos
[k
], tsin
[k
]);
141 ff_fft_calc(&s
->fft
, z
);
143 /* post rotation + reordering */
145 for(k
= 0; k
< n8
; k
++) {
146 FFTSample r0
, i0
, r1
, i1
;
147 CMUL(r0
, i1
, z
[n8
-k
-1].im
, z
[n8
-k
-1].re
, tsin
[n8
-k
-1], tcos
[n8
-k
-1]);
148 CMUL(r1
, i0
, z
[n8
+k
].im
, z
[n8
+k
].re
, tsin
[n8
+k
], tcos
[n8
+k
]);
157 * Compute inverse MDCT of size N = 2^nbits
158 * @param output N samples
159 * @param input N/2 samples
160 * @param tmp N/2 samples
162 void ff_imdct_calc_c(MDCTContext
*s
, FFTSample
*output
, const FFTSample
*input
)
165 int n
= 1 << s
->nbits
;
169 ff_imdct_half_c(s
, output
+n4
, input
);
171 for(k
= 0; k
< n4
; k
++) {
172 output
[k
] = -output
[n2
-k
-1];
173 output
[n
-k
-1] = output
[n2
+k
];
178 * Compute MDCT of size N = 2^nbits
179 * @param input N samples
180 * @param out N/2 samples
181 * @param tmp temporary storage of N/2 samples
183 void ff_mdct_calc(MDCTContext
*s
, FFTSample
*out
, const FFTSample
*input
)
185 int i
, j
, n
, n8
, n4
, n2
, n3
;
187 const uint16_t *revtab
= s
->fft
.revtab
;
188 const FFTSample
*tcos
= s
->tcos
;
189 const FFTSample
*tsin
= s
->tsin
;
190 FFTComplex
*x
= (FFTComplex
*)out
;
200 re
= -input
[2*i
+3*n4
] - input
[n3
-1-2*i
];
201 im
= -input
[n4
+2*i
] + input
[n4
-1-2*i
];
203 CMUL(x
[j
].re
, x
[j
].im
, re
, im
, -tcos
[i
], tsin
[i
]);
205 re
= input
[2*i
] - input
[n2
-1-2*i
];
206 im
= -(input
[n2
+2*i
] + input
[n
-1-2*i
]);
208 CMUL(x
[j
].re
, x
[j
].im
, re
, im
, -tcos
[n8
+ i
], tsin
[n8
+ i
]);
211 ff_fft_calc(&s
->fft
, x
);
215 FFTSample r0
, i0
, r1
, i1
;
216 CMUL(i1
, r0
, x
[n8
-i
-1].re
, x
[n8
-i
-1].im
, -tsin
[n8
-i
-1], -tcos
[n8
-i
-1]);
217 CMUL(i0
, r1
, x
[n8
+i
].re
, x
[n8
+i
].im
, -tsin
[n8
+i
], -tcos
[n8
+i
]);
225 void ff_mdct_end(MDCTContext
*s
)