path: root/libavfilter/window_func.c (plain)
blob: acf1b20847ca26ad96ec470ee16042eb0238aa1f

1	/*
2	* Copyright (c) 2015 Paul B Mahol
3	*
4	* This file is part of FFmpeg.
5	*
6	* FFmpeg is free software; you can redistribute it and/or
7	* modify it under the terms of the GNU Lesser General Public
8	* License as published by the Free Software Foundation; either
9	* version 2.1 of the License, or (at your option) any later version.
10	*
11	* FFmpeg is distributed in the hope that it will be useful,
12	* but WITHOUT ANY WARRANTY; without even the implied warranty of
13	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14	* Lesser General Public License for more details.
15	*
16	* You should have received a copy of the GNU Lesser General Public
17	* License along with FFmpeg; if not, write to the Free Software
18	* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
19	*/
20
21	#include <math.h>
22
23	#include "libavutil/avassert.h"
24	#include "window_func.h"
25
26	void ff_generate_window_func(float *lut, int N, int win_func, float *overlap)
27	{
28	int n;
29
30	switch (win_func) {
31	case WFUNC_RECT:
32	for (n = 0; n < N; n++)
33	lut[n] = 1.;
34	*overlap = 0.;
35	break;
36	case WFUNC_BARTLETT:
37	for (n = 0; n < N; n++)
38	lut[n] = 1.-fabs((n-(N-1)/2.)/((N-1)/2.));
39	*overlap = 0.5;
40	break;
41	case WFUNC_HANNING:
42	for (n = 0; n < N; n++)
43	lut[n] = .5*(1-cos(2*M_PI*n/(N-1)));
44	*overlap = 0.5;
45	break;
46	case WFUNC_HAMMING:
47	for (n = 0; n < N; n++)
48	lut[n] = .54-.46*cos(2*M_PI*n/(N-1));
49	*overlap = 0.5;
50	break;
51	case WFUNC_BLACKMAN:
52	for (n = 0; n < N; n++)
53	lut[n] = .42659-.49656*cos(2*M_PI*n/(N-1))+.076849*cos(4*M_PI*n/(N-1));
54	*overlap = 0.661;
55	break;
56	case WFUNC_WELCH:
57	for (n = 0; n < N; n++)
58	lut[n] = 1.-(n-(N-1)/2.)/((N-1)/2.)*(n-(N-1)/2.)/((N-1)/2.);
59	*overlap = 0.293;
60	break;
61	case WFUNC_FLATTOP:
62	for (n = 0; n < N; n++)
63	lut[n] = 1.-1.985844164102*cos( 2*M_PI*n/(N-1))+1.791176438506*cos( 4*M_PI*n/(N-1))-
64	1.282075284005*cos( 6*M_PI*n/(N-1))+0.667777530266*cos( 8*M_PI*n/(N-1))-
65	0.240160796576*cos(10*M_PI*n/(N-1))+0.056656381764*cos(12*M_PI*n/(N-1))-
66	0.008134974479*cos(14*M_PI*n/(N-1))+0.000624544650*cos(16*M_PI*n/(N-1))-
67	0.000019808998*cos(18*M_PI*n/(N-1))+0.000000132974*cos(20*M_PI*n/(N-1));
68	*overlap = 0.841;
69	break;
70	case WFUNC_BHARRIS:
71	for (n = 0; n < N; n++)
72	lut[n] = 0.35875-0.48829*cos(2*M_PI*n/(N-1))+0.14128*cos(4*M_PI*n/(N-1))-0.01168*cos(6*M_PI*n/(N-1));
73	*overlap = 0.661;
74	break;
75	case WFUNC_BNUTTALL:
76	for (n = 0; n < N; n++)
77	lut[n] = 0.3635819-0.4891775*cos(2*M_PI*n/(N-1))+0.1365995*cos(4*M_PI*n/(N-1))-0.0106411*cos(6*M_PI*n/(N-1));
78	*overlap = 0.661;
79	break;
80	case WFUNC_BHANN:
81	for (n = 0; n < N; n++)
82	lut[n] = 0.62-0.48*fabs(n/(double)(N-1)-.5)-0.38*cos(2*M_PI*n/(N-1));
83	*overlap = 0.5;
84	break;
85	case WFUNC_SINE:
86	for (n = 0; n < N; n++)
87	lut[n] = sin(M_PI*n/(N-1));
88	*overlap = 0.75;
89	break;
90	case WFUNC_NUTTALL:
91	for (n = 0; n < N; n++)
92	lut[n] = 0.355768-0.487396*cos(2*M_PI*n/(N-1))+0.144232*cos(4*M_PI*n/(N-1))-0.012604*cos(6*M_PI*n/(N-1));
93	*overlap = 0.663;
94	break;
95	case WFUNC_LANCZOS:
96	#define SINC(x) (!(x)) ? 1 : sin(M_PI * (x))/(M_PI * (x));
97	for (n = 0; n < N; n++)
98	lut[n] = SINC((2.*n)/(N-1)-1);
99	*overlap = 0.75;
100	break;
101	case WFUNC_GAUSS:
102	#define SQR(x) ((x)*(x))
103	for (n = 0; n < N; n++)
104	lut[n] = exp(-0.5 * SQR((n-(N-1)/2)/(0.4*(N-1)/2.f)));
105	*overlap = 0.75;
106	break;
107	case WFUNC_TUKEY:
108	for (n = 0; n < N; n++) {
109	float M = (N-1)/2.;
110
111	if (FFABS(n - M) >= 0.3 * M) {
112	lut[n] = 0.5 * (1 + cos((M_PI*(FFABS(n - M) - 0.3 * M))/((1 - 0.3) * M)));
113	} else {
114	lut[n] = 1;
115	}
116	}
117	*overlap = 0.33;
118	break;
119	case WFUNC_DOLPH: {
120	double b = cosh(7.6009022095419887 / (N-1)), sum, t, c, norm = 0;
121	int j;
122	for (c = 1 - 1 / (b*b), n = (N-1) / 2; n >= 0; --n) {
123	for (sum = !n, b = t = j = 1; j <= n && sum != t; b *= (n-j) * (1./j), ++j)
124	t = sum, sum += (b *= c * (N - n - j) * (1./j));
125	sum /= (N - 1 - n), sum /= (norm = norm ? norm : sum);
126	lut[n] = sum;
127	lut[N - 1 - n] = sum;
128	}
129	*overlap = 0.5;}
130	break;
131	case WFUNC_CAUCHY:
132	for (n = 0; n < N; n++) {
133	double x = 2 * ((n / (double)(N - 1)) - .5);
134
135	if (x <= -.5 || x >= .5) {
136	lut[n] = 0;
137	} else {
138	lut[n] = FFMIN(1, fabs(1/(1+4*16*x*x)));
139	}
140	}
141	*overlap = 0.75;
142	break;
143	case WFUNC_PARZEN:
144	for (n = 0; n < N; n++) {
145	double x = 2 * ((n / (double)(N - 1)) - .5);
146
147	if (x > 0.25 && x <= 0.5) {
148	lut[n] = -2 * powf(-1 + 2 * x, 3);
149	} else if (x >= -.5 && x < -.25) {
150	lut[n] = 2 * powf(1 + 2 * x, 3);
151	} else if (x >= -.25 && x < 0) {
152	lut[n] = 1 - 24 * x * x - 48 * x * x * x;
153	} else if (x >= 0 && x <= .25) {
154	lut[n] = 1 - 24 * x * x + 48 * x * x * x;
155	} else {
156	lut[n] = 0;
157	}
158	}
159	*overlap = 0.75;
160	break;
161	case WFUNC_POISSON:
162	for (n = 0; n < N; n++) {
163	double x = 2 * ((n / (double)(N - 1)) - .5);
164
165	if (x >= 0 && x <= .5) {
166	lut[n] = exp(-6*x);
167	} else if (x < 0 && x >= -.5) {
168	lut[n] = exp(6*x);
169	} else {
170	lut[n] = 0;
171	}
172	}
173	*overlap = 0.75;
174	break;
175	default:
176	av_assert0(0);
177	}
178	}
179