82 lines
2.0 KiB
C
82 lines
2.0 KiB
C
/*
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* Copyright (C) 2003-2011 The Music Player Daemon Project
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* http://www.musicpd.org
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License along
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* with this program; if not, write to the Free Software Foundation, Inc.,
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* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
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*/
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#ifndef PCM_VOLUME_H
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#define PCM_VOLUME_H
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#include "pcm_prng.h"
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#include "audio_format.h"
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#include <stdint.h>
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#include <stdbool.h>
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enum {
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/** this value means "100% volume" */
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PCM_VOLUME_1 = 1024,
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};
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struct audio_format;
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/**
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* Converts a float value (0.0 = silence, 1.0 = 100% volume) to an
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* integer volume value (1000 = 100%).
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*/
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static inline int
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pcm_float_to_volume(float volume)
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{
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return volume * PCM_VOLUME_1 + 0.5;
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}
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static inline float
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pcm_volume_to_float(int volume)
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{
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return (float)volume / (float)PCM_VOLUME_1;
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}
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/**
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* Returns the next volume dithering number, between -511 and +511.
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* This number is taken from a global PRNG, see pcm_prng().
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*/
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static inline int
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pcm_volume_dither(void)
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{
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static unsigned long state;
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uint32_t r;
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r = state = pcm_prng(state);
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return (r & 511) - ((r >> 9) & 511);
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}
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/**
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* Adjust the volume of the specified PCM buffer.
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*
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* @param buffer the PCM buffer
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* @param length the length of the PCM buffer
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* @param format the sample format of the PCM buffer
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* @param volume the volume between 0 and #PCM_VOLUME_1
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* @return true on success, false if the audio format is not supported
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*/
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bool
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pcm_volume(void *buffer, size_t length,
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enum sample_format format,
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int volume);
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#endif
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