src/pcm_mix.h

   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