/* * Copyright (C) 2003-2010 The Music Player Daemon Project * http://www.musicpd.org * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation; either version 2 of the License, or * (at your option) any later version. * * This program is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU General Public License for more details. * * You should have received a copy of the GNU General Public License along * with this program; if not, write to the Free Software Foundation, Inc., * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA. */ #ifndef PCM_VOLUME_H #define PCM_VOLUME_H #include "pcm_prng.h" #include <stdint.h> #include <stdbool.h> enum { /** this value means "100% volume" */ PCM_VOLUME_1 = 1024, }; struct audio_format; /** * Converts a float value (0.0 = silence, 1.0 = 100% volume) to an * integer volume value (1000 = 100%). */ static inline int pcm_float_to_volume(float volume) { return volume * PCM_VOLUME_1 + 0.5; } /** * Returns the next volume dithering number, between -511 and +511. * This number is taken from a global PRNG, see pcm_prng(). */ static inline int pcm_volume_dither(void) { static unsigned long state; uint32_t r; r = state = pcm_prng(state); return (r & 511) - ((r >> 9) & 511); } /** * Adjust the volume of the specified PCM buffer. * * @param buffer the PCM buffer * @param length the length of the PCM buffer * @param format the audio format of the PCM buffer * @param volume the volume between 0 and #PCM_VOLUME_1 * @return true on success, false if the audio format is not supported */ bool pcm_volume(void *buffer, int length, const struct audio_format *format, int volume); #endif