1 /*
2 * Opus encoder
3 * Copyright (c) 2017 Rostislav Pehlivanov <atomnuker@gmail.com>
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
22 #ifndef AVCODEC_OPUS_ENC_UTILS_H
23 #define AVCODEC_OPUS_ENC_UTILS_H
24
25 #include <math.h>
26 #include <string.h>
27
29
36
37 /* Fills the coefficients, returns 1 if filter will be unstable */
40 {
41 int unstable;
42 float c, cfreq, w0, k1, k2;
43
47 unstable = (cfreq <= 0.0f || cfreq >= 1.0f/4.0f);
48 } else {
50 cfreq = 0.5f -
c*f0/
fs;
51 unstable = (cfreq <= 3.0f/8.0f || cfreq >= 1.0f/2.0f);
52 }
53
54 w0 = tanf(
M_PI*cfreq);
55 k1 = 3.0f * w0;
56 k2 = 3.0f * w0;
57
58 s->a[0] = k2/(1.0f + k1 + k2);
59 s->a[1] = 2.0f *
s->a[0];
61 s->b[0] = 2.0f *
s->a[0] * (1.0f/k2 - 1.0f);
62 s->b[1] = 1.0f - (
s->a[0] +
s->a[1] +
s->a[2] +
s->b[0]);
63
67 }
68
69 return unstable;
70 }
71
74 {
77 }
78
80 {
86 s->y[0] =
s->a[0]*
s->x[0] +
s->a[1]*
s->x[1] +
s->a[2]*
s->x[2] +
s->b[0]*
s->y[1] +
s->b[1]*
s->y[2];
88 }
89
90 #endif /* AVCODEC_OPUS_ENC_UTILS_H */