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Diffstat (limited to 'engines/adl/sound.cpp')
-rw-r--r-- | engines/adl/sound.cpp | 144 |
1 files changed, 144 insertions, 0 deletions
diff --git a/engines/adl/sound.cpp b/engines/adl/sound.cpp new file mode 100644 index 0000000000..17f4955a12 --- /dev/null +++ b/engines/adl/sound.cpp @@ -0,0 +1,144 @@ +/* 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_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_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 |