1/*
2 * MDCT/IMDCT transforms
3 * Copyright (c) 2002 Fabrice Bellard
4 *
5 * This file is part of FFmpeg.
6 *
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.
11 *
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.
16 *
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
20 */
21#include "dsputil.h"
22
23/**
24 * @file libavcodec/mdct.c
25 * MDCT/IMDCT transforms.
26 */
27
28// Generate a Kaiser-Bessel Derived Window.
29#define BESSEL_I0_ITER 50 // default: 50 iterations of Bessel I0 approximation
30av_cold void ff_kbd_window_init(float *window, float alpha, int n)
31{
32   int i, j;
33   double sum = 0.0, bessel, tmp;
34   double local_window[n];
35   double alpha2 = (alpha * M_PI / n) * (alpha * M_PI / n);
36
37   for (i = 0; i < n; i++) {
38       tmp = i * (n - i) * alpha2;
39       bessel = 1.0;
40       for (j = BESSEL_I0_ITER; j > 0; j--)
41           bessel = bessel * tmp / (j * j) + 1;
42       sum += bessel;
43       local_window[i] = sum;
44   }
45
46   sum++;
47   for (i = 0; i < n; i++)
48       window[i] = sqrt(local_window[i] / sum);
49}
50
51DECLARE_ALIGNED(16, float, ff_sine_128 [ 128]);
52DECLARE_ALIGNED(16, float, ff_sine_256 [ 256]);
53DECLARE_ALIGNED(16, float, ff_sine_512 [ 512]);
54DECLARE_ALIGNED(16, float, ff_sine_1024[1024]);
55DECLARE_ALIGNED(16, float, ff_sine_2048[2048]);
56DECLARE_ALIGNED(16, float, ff_sine_4096[4096]);
57float *ff_sine_windows[6] = {
58    ff_sine_128, ff_sine_256, ff_sine_512, ff_sine_1024, ff_sine_2048, ff_sine_4096
59};
60
61// Generate a sine window.
62av_cold void ff_sine_window_init(float *window, int n) {
63    int i;
64    for(i = 0; i < n; i++)
65        window[i] = sinf((i + 0.5) * (M_PI / (2.0 * n)));
66}
67
68/**
69 * init MDCT or IMDCT computation.
70 */
71av_cold int ff_mdct_init(MDCTContext *s, int nbits, int inverse)
72{
73    int n, n4, i;
74    double alpha;
75
76    memset(s, 0, sizeof(*s));
77    n = 1 << nbits;
78    s->nbits = nbits;
79    s->n = n;
80    n4 = n >> 2;
81    s->tcos = av_malloc(n4 * sizeof(FFTSample));
82    if (!s->tcos)
83        goto fail;
84    s->tsin = av_malloc(n4 * sizeof(FFTSample));
85    if (!s->tsin)
86        goto fail;
87
88    for(i=0;i<n4;i++) {
89        alpha = 2 * M_PI * (i + 1.0 / 8.0) / n;
90        s->tcos[i] = -cos(alpha);
91        s->tsin[i] = -sin(alpha);
92    }
93    if (ff_fft_init(&s->fft, s->nbits - 2, inverse) < 0)
94        goto fail;
95    return 0;
96 fail:
97    av_freep(&s->tcos);
98    av_freep(&s->tsin);
99    return -1;
100}
101
102/* complex multiplication: p = a * b */
103#define CMUL(pre, pim, are, aim, bre, bim) \
104{\
105    FFTSample _are = (are);\
106    FFTSample _aim = (aim);\
107    FFTSample _bre = (bre);\
108    FFTSample _bim = (bim);\
109    (pre) = _are * _bre - _aim * _bim;\
110    (pim) = _are * _bim + _aim * _bre;\
111}
112
113/**
114 * Compute the middle half of the inverse MDCT of size N = 2^nbits,
115 * thus excluding the parts that can be derived by symmetry
116 * @param output N/2 samples
117 * @param input N/2 samples
118 */
119void ff_imdct_half_c(MDCTContext *s, FFTSample *output, const FFTSample *input)
120{
121    int k, n8, n4, n2, n, j;
122    const uint16_t *revtab = s->fft.revtab;
123    const FFTSample *tcos = s->tcos;
124    const FFTSample *tsin = s->tsin;
125    const FFTSample *in1, *in2;
126    FFTComplex *z = (FFTComplex *)output;
127
128    n = 1 << s->nbits;
129    n2 = n >> 1;
130    n4 = n >> 2;
131    n8 = n >> 3;
132
133    /* pre rotation */
134    in1 = input;
135    in2 = input + n2 - 1;
136    for(k = 0; k < n4; k++) {
137        j=revtab[k];
138        CMUL(z[j].re, z[j].im, *in2, *in1, tcos[k], tsin[k]);
139        in1 += 2;
140        in2 -= 2;
141    }
142    ff_fft_calc(&s->fft, z);
143
144    /* post rotation + reordering */
145    output += n4;
146    for(k = 0; k < n8; k++) {
147        FFTSample r0, i0, r1, i1;
148        CMUL(r0, i1, z[n8-k-1].im, z[n8-k-1].re, tsin[n8-k-1], tcos[n8-k-1]);
149        CMUL(r1, i0, z[n8+k  ].im, z[n8+k  ].re, tsin[n8+k  ], tcos[n8+k  ]);
150        z[n8-k-1].re = r0;
151        z[n8-k-1].im = i0;
152        z[n8+k  ].re = r1;
153        z[n8+k  ].im = i1;
154    }
155}
156
157/**
158 * Compute inverse MDCT of size N = 2^nbits
159 * @param output N samples
160 * @param input N/2 samples
161 */
162void ff_imdct_calc_c(MDCTContext *s, FFTSample *output, const FFTSample *input)
163{
164    int k;
165    int n = 1 << s->nbits;
166    int n2 = n >> 1;
167    int n4 = n >> 2;
168
169    ff_imdct_half_c(s, output+n4, input);
170
171    for(k = 0; k < n4; k++) {
172        output[k] = -output[n2-k-1];
173        output[n-k-1] = output[n2+k];
174    }
175}
176
177/**
178 * Compute MDCT of size N = 2^nbits
179 * @param input N samples
180 * @param out N/2 samples
181 */
182void ff_mdct_calc(MDCTContext *s, FFTSample *out, const FFTSample *input)
183{
184    int i, j, n, n8, n4, n2, n3;
185    FFTSample re, im;
186    const uint16_t *revtab = s->fft.revtab;
187    const FFTSample *tcos = s->tcos;
188    const FFTSample *tsin = s->tsin;
189    FFTComplex *x = (FFTComplex *)out;
190
191    n = 1 << s->nbits;
192    n2 = n >> 1;
193    n4 = n >> 2;
194    n8 = n >> 3;
195    n3 = 3 * n4;
196
197    /* pre rotation */
198    for(i=0;i<n8;i++) {
199        re = -input[2*i+3*n4] - input[n3-1-2*i];
200        im = -input[n4+2*i] + input[n4-1-2*i];
201        j = revtab[i];
202        CMUL(x[j].re, x[j].im, re, im, -tcos[i], tsin[i]);
203
204        re = input[2*i] - input[n2-1-2*i];
205        im = -(input[n2+2*i] + input[n-1-2*i]);
206        j = revtab[n8 + i];
207        CMUL(x[j].re, x[j].im, re, im, -tcos[n8 + i], tsin[n8 + i]);
208    }
209
210    ff_fft_calc(&s->fft, x);
211
212    /* post rotation */
213    for(i=0;i<n8;i++) {
214        FFTSample r0, i0, r1, i1;
215        CMUL(i1, r0, x[n8-i-1].re, x[n8-i-1].im, -tsin[n8-i-1], -tcos[n8-i-1]);
216        CMUL(i0, r1, x[n8+i  ].re, x[n8+i  ].im, -tsin[n8+i  ], -tcos[n8+i  ]);
217        x[n8-i-1].re = r0;
218        x[n8-i-1].im = i0;
219        x[n8+i  ].re = r1;
220        x[n8+i  ].im = i1;
221    }
222}
223
224av_cold void ff_mdct_end(MDCTContext *s)
225{
226    av_freep(&s->tcos);
227    av_freep(&s->tsin);
228    ff_fft_end(&s->fft);
229}
230