MPD
pcm_mix.h
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1 /*
2  * Copyright (C) 2003-2010 The Music Player Daemon Project
3  * http://www.musicpd.org
4  *
5  * This program is free software; you can redistribute it and/or modify
6  * it under the terms of the GNU General Public License as published by
7  * the Free Software Foundation; either version 2 of the License, or
8  * (at your option) any later version.
9  *
10  * This program is distributed in the hope that it will be useful,
11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13  * GNU General Public License for more details.
14  *
15  * You should have received a copy of the GNU General Public License along
16  * with this program; if not, write to the Free Software Foundation, Inc.,
17  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
18  */
19 
20 #ifndef PCM_MIX_H
21 #define PCM_MIX_H
22 
23 #include <stddef.h>
24 
25 struct audio_format;
26 
27 /*
28  * Linearly mixes two PCM buffers. Both must have the same length and
29  * the same audio format. The formula is:
30  *
31  * s1 := s1 * portion1 + s2 * (1 - portion1)
32  *
33  * @param buffer1 the first PCM buffer, and the destination buffer
34  * @param buffer2 the second PCM buffer
35  * @param size the size of both buffers in bytes
36  * @param format the audio format of both buffers
37  * @param portion1 a number between 0.0 and 1.0 specifying the portion
38  * of the first buffer in the mix; portion2 = (1.0 - portion1). The value
39  * NaN is used by the MixRamp code to specify that simple addition is required.
40  */
41 void
42 pcm_mix(void *buffer1, const void *buffer2, size_t size,
43  const struct audio_format *format, float portion1);
44 
45 #endif