mirror of
https://github.com/libretro/scummvm.git
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147 lines
3.5 KiB
C++
147 lines
3.5 KiB
C++
/* ScummVM - Graphic Adventure Engine
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*
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* ScummVM is the legal property of its developers, whose names
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* are too numerous to list here. Please refer to the COPYRIGHT
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* file distributed with this source distribution.
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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 3 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
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*
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*/
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#include "common/system.h"
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#include "audio/mixer.h"
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#include "adl/sound.h"
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namespace Adl {
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// Generic PC-speaker synth
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// This produces more accurate frequencies than Audio::PCSpeaker, but only
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// does square waves.
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class Speaker {
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public:
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Speaker(int sampleRate);
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void startTone(double freq);
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void stopTone();
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void generateSamples(int16 *buffer, int numSamples);
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private:
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int _rate;
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frac_t _halfWaveLen, _halfWaveRem;
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int16 _curSample;
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};
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Speaker::Speaker(int sampleRate) :
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_rate(sampleRate),
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_halfWaveLen(0),
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_halfWaveRem(0),
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_curSample(32767) { }
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void Speaker::startTone(double freq) {
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_halfWaveLen = _halfWaveRem = doubleToFrac(_rate / freq / 2);
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if (_halfWaveLen < (frac_t)FRAC_ONE) {
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// Tone out of range at this sample rate
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stopTone();
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}
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}
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void Speaker::stopTone() {
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_halfWaveLen = 0;
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}
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void Speaker::generateSamples(int16 *buffer, int numSamples) {
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if (_halfWaveLen == 0) {
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// Silence
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memset(buffer, 0, numSamples * sizeof(int16));
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return;
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}
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int offset = 0;
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while (offset < numSamples) {
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if (_halfWaveRem >= 0 && _halfWaveRem < (frac_t)FRAC_ONE) {
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// Rising/falling edge
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// Switch level
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_curSample = ~_curSample;
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// Use transition point fraction for current sample value
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buffer[offset++] = _halfWaveRem ^ _curSample;
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// Compute next transition point
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_halfWaveRem += _halfWaveLen - FRAC_ONE;
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} else {
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// Low/high level
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// Generate as many samples as we can
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const int samples = MIN(numSamples - offset, (int)fracToInt(_halfWaveRem));
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Common::fill(buffer + offset, buffer + offset + samples, _curSample);
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offset += samples;
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// Count down to level transition point
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_halfWaveRem -= intToFrac(samples);
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}
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}
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}
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Sound::Sound(const Tones &tones) :
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_tones(tones),
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_toneIndex(0),
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_samplesRem(0) {
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_rate = g_system->getMixer()->getOutputRate();
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_speaker = new Speaker(_rate);
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}
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Sound::~Sound() {
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delete _speaker;
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}
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bool Sound::endOfData() const {
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return _samplesRem == 0 && _toneIndex == _tones.size();
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}
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int Sound::readBuffer(int16 *buffer, const int numSamples) {
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int offset = 0;
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while (offset < numSamples) {
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if (_samplesRem == 0) {
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// Set up next tone
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if (_toneIndex == _tones.size()) {
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// No more tones
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return offset;
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}
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if (_tones[_toneIndex].freq == 0.0)
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_speaker->stopTone();
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else
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_speaker->startTone(_tones[_toneIndex].freq);
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// Compute length of tone
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_samplesRem = _rate * _tones[_toneIndex++].len / 1000;
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}
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// Generate as many samples as we can
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const int samples = MIN(numSamples - offset, _samplesRem);
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_speaker->generateSamples(buffer + offset, samples);
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_samplesRem -= samples;
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offset += samples;
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}
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return numSamples;
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}
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} // End of namespace Adl
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