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/*
* 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
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