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/* ScummVM - Graphic Adventure Engine
*
* ScummVM is the legal property of its developers, whose names
* are too numerous to list here. Please refer to the COPYRIGHT
* file distributed with this source distribution.
*
* 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.
*
*/
#include "common/system.h"
#include "audio/mixer.h"
#include "adl/sound.h"
namespace Adl {
// Generic PC-speaker synth
// This produces more accurate frequencies than Audio::PCSpeaker, but only
// does square waves.
class Speaker {
public:
Speaker(int sampleRate);
void startTone(double freq);
void stopTone();
void generateSamples(int16 *buffer, int numSamples);
private:
int _rate;
frac_t _halfWaveLen, _halfWaveRem;
int16 _curSample;
};
Speaker::Speaker(int sampleRate) :
_rate(sampleRate),
_curSample(32767) {
stopTone();
}
void Speaker::startTone(double freq) {
_halfWaveLen = _halfWaveRem = doubleToFrac(_rate / freq / 2);
if (_halfWaveLen < (frac_t)FRAC_ONE) {
// Tone out of range at this sample rate
stopTone();
}
}
void Speaker::stopTone() {
_halfWaveLen = 0;
_halfWaveRem = intToFrac(32767);
}
void Speaker::generateSamples(int16 *buffer, int numSamples) {
int offset = 0;
while (offset < numSamples) {
if (_halfWaveRem >= 0 && _halfWaveRem < (frac_t)FRAC_ONE) {
// Rising/falling edge
// Switch level
_curSample = ~_curSample;
// Use transition point fraction for current sample value
buffer[offset++] = _halfWaveRem ^ _curSample;
// Compute next transition point
_halfWaveRem += _halfWaveLen - FRAC_ONE;
} else {
// Low/high level (incl. silence)
// Generate as many samples as we can
const int samples = MIN(numSamples - offset, (int)fracToInt(_halfWaveRem));
Common::fill(buffer + offset, buffer + offset + samples, _curSample);
offset += samples;
// Count down to level transition point, unless we're playing silence
if (_halfWaveLen > 0)
_halfWaveRem -= intToFrac(samples);
}
}
}
Sound::Sound(const Tones &tones) :
_tones(tones),
_toneIndex(0),
_samplesRem(0) {
_rate = g_system->getMixer()->getOutputRate();
_speaker = new Speaker(_rate);
}
Sound::~Sound() {
delete _speaker;
}
bool Sound::endOfData() const {
return _samplesRem == 0 && _toneIndex == _tones.size();
}
int Sound::readBuffer(int16 *buffer, const int numSamples) {
int offset = 0;
while (offset < numSamples) {
if (_samplesRem == 0) {
// Set up next tone
if (_toneIndex == _tones.size()) {
// No more tones
return offset;
}
if (_tones[_toneIndex].freq == 0.0)
_speaker->stopTone();
else
_speaker->startTone(_tones[_toneIndex].freq);
// Compute length of tone
_samplesRem = _rate * _tones[_toneIndex++].len / 1000;
}
// Generate as many samples as we can
const int samples = MIN(numSamples - offset, _samplesRem);
_speaker->generateSamples(buffer + offset, samples);
_samplesRem -= samples;
offset += samples;
}
return numSamples;
}
} // End of namespace Adl
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