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/*
* dxr3audio.c
*
* Copyright (C) 2009 Christian Gmeiner
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* This library 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
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*
*/
#include <string.h> // for memeset
#include <math.h> // for pow
#include <vdr/device.h> // for MAXVOLUME
#include "dxr3audio.h"
const static int AUDIO_STEREO = 0;
const static int AUDIO_MONO_LEFT = 1;
const static int AUDIO_MONO_RIGHT = 2;
iAudio::iAudio() : open(false), enabled(false), vol(0), audioChannel(0), digitalAudio(false)
{
memset(&curContext, 0, sizeof(SampleContext));
}
void iAudio::changeVolume(int16_t* pcmbuf, size_t size)
{
if (vol == 0) {
memset(pcmbuf, 0, size);
} else if (vol < MAXVOLUME) {
int factor = (int)(pow(10.0, -2.5 + 2.5*vol/256.0)*0x7FFF);
size = size / 2;
while (size > 0) {
register int32_t tmp = (int32_t)(*pcmbuf) * factor;
*pcmbuf = (int16_t) (tmp>>15);
pcmbuf++;
size--;
}
}
// respect audio channel setting
if (audioChannel == AUDIO_STEREO)
return;
if (audioChannel == AUDIO_MONO_RIGHT) {
for (unsigned int i = 0; i < size / sizeof(short); i++) {
if (!(i & 0x1))
pcmbuf[i] = pcmbuf[i+1];
}
} else if (audioChannel == AUDIO_MONO_LEFT) {
for (unsigned int i = 0; i < size / sizeof(short); i++) {
if ((i & 0x1))
pcmbuf[i] = pcmbuf[i-1];
}
}
}
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