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/* Copyright (C) 2003, 2004, 2005, 2006, 2008, 2009 Dean Beeler, Jerome Fisher
* Copyright (C) 2011, 2012, 2013, 2014 Dean Beeler, Jerome Fisher, Sergey V. Mikayev
*
* This program 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 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 Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#ifndef MT32EMU_LA32_WAVE_GENERATOR_H
#define MT32EMU_LA32_WAVE_GENERATOR_H
namespace MT32Emu {
/**
* LA32WaveGenerator is aimed to represent the exact model of LA32 wave generator.
* The output square wave is created by adding high / low linear segments in-between
* the rising and falling cosine segments. Basically, it�s very similar to the phase distortion synthesis.
* Behaviour of a true resonance filter is emulated by adding decaying sine wave.
* The beginning and the ending of the resonant sine is multiplied by a cosine window.
* To synthesise sawtooth waves, the resulting square wave is multiplied by synchronous cosine wave.
*/
class LA32WaveGenerator {
//***************************************************************************
// The local copy of partial parameters below
//***************************************************************************
bool active;
// True means the resulting square wave is to be multiplied by the synchronous cosine
bool sawtoothWaveform;
// Logarithmic amp of the wave generator
Bit32u amp;
// Logarithmic frequency of the resulting wave
Bit16u pitch;
// Values in range [1..31]
// Value 1 correspong to the minimum resonance
Bit8u resonance;
// Processed value in range [0..255]
// Values in range [0..128] have no effect and the resulting wave remains symmetrical
// Value 255 corresponds to the maximum possible asymmetric of the resulting wave
Bit8u pulseWidth;
// Composed of the base cutoff in range [78..178] left-shifted by 18 bits and the TVF modifier
Bit32u cutoffVal;
// Logarithmic PCM sample start address
const Bit16s *pcmWaveAddress;
// Logarithmic PCM sample length
Bit32u pcmWaveLength;
// true for looped logarithmic PCM samples
bool pcmWaveLooped;
// false for slave PCM partials in the structures with the ring modulation
bool pcmWaveInterpolated;
//***************************************************************************
// Internal variables below
//***************************************************************************
float wavePos;
float lastFreq;
float pcmPosition;
float getPCMSample(unsigned int position);
public:
// Initialise the WG engine for generation of synth partial samples and set up the invariant parameters
void initSynth(const bool sawtoothWaveform, const Bit8u pulseWidth, const Bit8u resonance);
// Initialise the WG engine for generation of PCM partial samples and set up the invariant parameters
void initPCM(const Bit16s * const pcmWaveAddress, const Bit32u pcmWaveLength, const bool pcmWaveLooped, const bool pcmWaveInterpolated);
// Update parameters with respect to TVP, TVA and TVF, and generate next sample
float generateNextSample(const Bit32u amp, const Bit16u pitch, const Bit32u cutoff);
// Deactivate the WG engine
void deactivate();
// Return active state of the WG engine
bool isActive() const;
// Return true if the WG engine generates PCM wave samples
bool isPCMWave() const;
};
// LA32PartialPair contains a structure of two partials being mixed / ring modulated
class LA32PartialPair {
LA32WaveGenerator master;
LA32WaveGenerator slave;
bool ringModulated;
bool mixed;
float masterOutputSample;
float slaveOutputSample;
public:
enum PairType {
MASTER,
SLAVE
};
// ringModulated should be set to false for the structures with mixing or stereo output
// ringModulated should be set to true for the structures with ring modulation
// mixed is used for the structures with ring modulation and indicates whether the master partial output is mixed to the ring modulator output
void init(const bool ringModulated, const bool mixed);
// Initialise the WG engine for generation of synth partial samples and set up the invariant parameters
void initSynth(const PairType master, const bool sawtoothWaveform, const Bit8u pulseWidth, const Bit8u resonance);
// Initialise the WG engine for generation of PCM partial samples and set up the invariant parameters
void initPCM(const PairType master, const Bit16s * const pcmWaveAddress, const Bit32u pcmWaveLength, const bool pcmWaveLooped);
// Update parameters with respect to TVP, TVA and TVF, and generate next sample
void generateNextSample(const PairType master, const Bit32u amp, const Bit16u pitch, const Bit32u cutoff);
// Perform mixing / ring modulation and return the result
float nextOutSample();
// Deactivate the WG engine
void deactivate(const PairType master);
// Return active state of the WG engine
bool isActive(const PairType master) const;
};
} // namespace MT32Emu
#endif // #ifndef MT32EMU_LA32_WAVE_GENERATOR_H
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