mirror of https://github.com/bsnes-emu/bsnes.git
59 lines
1.7 KiB
C++
59 lines
1.7 KiB
C++
auto DSP::envelopeRun(Voice& v) -> void {
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int envelope = v.envelope;
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if(v.envelopeMode == EnvelopeRelease) { //60%
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envelope -= 0x8;
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if(envelope < 0) envelope = 0;
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v.envelope = envelope;
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return;
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}
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int rate;
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int envelopeData = VREG(ADSR1);
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if(state._adsr0 & 0x80) { //99% ADSR
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if(v.envelopeMode >= EnvelopeDecay) { //99%
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envelope--;
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envelope -= envelope >> 8;
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rate = envelopeData & 0x1f;
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if(v.envelopeMode == EnvelopeDecay) { //1%
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rate = ((state._adsr0 >> 3) & 0x0e) + 0x10;
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}
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} else { //env_attack
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rate = ((state._adsr0 & 0x0f) << 1) + 1;
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envelope += rate < 31 ? 0x20 : 0x400;
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}
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} else { //GAIN
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envelopeData = VREG(GAIN);
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int mode = envelopeData >> 5;
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if(mode < 4) { //direct
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envelope = envelopeData << 4;
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rate = 31;
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} else {
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rate = envelopeData & 0x1f;
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if(mode == 4) { //4: linear decrease
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envelope -= 0x20;
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} else if(mode < 6) { //5: exponential decrease
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envelope--;
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envelope -= envelope >> 8;
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} else { //6, 7: linear increase
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envelope += 0x20;
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if(mode > 6 && (uint)v.hiddenEnvelope >= 0x600) {
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envelope += 0x8 - 0x20; //7: two-slope linear increase
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}
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}
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}
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}
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//sustain level
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if((envelope >> 8) == (envelopeData >> 5) && v.envelopeMode == EnvelopeDecay) v.envelopeMode = EnvelopeSustain;
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v.hiddenEnvelope = envelope;
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//uint cast because linear decrease underflowing also triggers this
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if((uint)envelope > 0x7ff) {
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envelope = (envelope < 0 ? 0 : 0x7ff);
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if(v.envelopeMode == EnvelopeAttack) v.envelopeMode = EnvelopeDecay;
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}
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if(counterPoll(rate)) v.envelope = envelope;
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}
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