mirror of
https://github.com/libretro/Mesen.git
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227 lines
5.6 KiB
C++
227 lines
5.6 KiB
C++
#include "stdafx.h"
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#include "DeltaModulationChannel.h"
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#include "APU.h"
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#include "CPU.h"
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#include "Console.h"
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#include "MemoryManager.h"
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DeltaModulationChannel *DeltaModulationChannel::Instance = nullptr;
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DeltaModulationChannel::DeltaModulationChannel(AudioChannel channel, SoundMixer *mixer, MemoryManager* memoryManager) : BaseApuChannel(channel, mixer)
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{
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Instance = this;
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_memoryManager = memoryManager;
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}
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void DeltaModulationChannel::Reset(bool softReset)
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{
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BaseApuChannel::Reset(softReset);
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_sampleAddr = 0;
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_sampleLength = 0;
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_outputLevel = 0;
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_irqEnabled = false;
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_loopFlag = false;
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_currentAddr = 0;
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_bytesRemaining = 0;
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_readBuffer = 0;
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_bufferEmpty = true;
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_shiftRegister = 0;
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_bitsRemaining = 8;
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_silenceFlag = true;
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_needToRun = false;
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_lastValue4011 = 0;
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//Not sure if this is accurate, but it seems to make things better rather than worse (for dpcmletterbox)
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//"On the real thing, I think the power-on value is 428 (or the equivalent at least - it uses a linear feedback shift register), though only the even/oddness should matter for this test."
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_period = (GetNesModel() == NesModel::NTSC ? _dmcPeriodLookupTableNtsc : _dmcPeriodLookupTablePal)[0] - 1;
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//Make sure the DMC doesn't tick on the first cycle - this is part of what keeps Sprite/DMC DMA tests working while fixing dmc_pitch.
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_timer = _period;
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}
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void DeltaModulationChannel::InitSample()
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{
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_currentAddr = _sampleAddr;
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_bytesRemaining = _sampleLength;
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_needToRun = _bytesRemaining > 0;
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}
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void DeltaModulationChannel::StartDmcTransfer()
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{
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if(_bufferEmpty && _bytesRemaining > 0) {
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CPU::StartDmcTransfer();
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}
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}
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void DeltaModulationChannel::FillReadBuffer()
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{
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if(_bytesRemaining > 0) {
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_readBuffer = _memoryManager->Read(_currentAddr);
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_bufferEmpty = false;
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_currentAddr++;
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_bytesRemaining--;
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if(_bytesRemaining == 0) {
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_needToRun = false;
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if(_loopFlag) {
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//Looped sample should never set IRQ flag
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InitSample();
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} else if(_irqEnabled) {
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CPU::SetIRQSource(IRQSource::DMC);
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}
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}
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}
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}
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void DeltaModulationChannel::Clock()
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{
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if(!_silenceFlag) {
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if(_shiftRegister & 0x01) {
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if(_outputLevel <= 125) {
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_outputLevel += 2;
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}
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} else {
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if(_outputLevel >= 2) {
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_outputLevel -= 2;
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}
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}
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_shiftRegister >>= 1;
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}
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_bitsRemaining--;
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if(_bitsRemaining == 0) {
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_bitsRemaining = 8;
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if(_bufferEmpty) {
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_silenceFlag = true;
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} else {
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_silenceFlag = false;
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_shiftRegister = _readBuffer;
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_bufferEmpty = true;
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StartDmcTransfer();
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}
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}
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AddOutput(_outputLevel);
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}
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void DeltaModulationChannel::StreamState(bool saving)
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{
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BaseApuChannel::StreamState(saving);
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int32_t unused_enableOverclockCounter = 0;
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Stream(_sampleAddr, _sampleLength, _outputLevel, _irqEnabled, _loopFlag, _currentAddr, _bytesRemaining, _readBuffer, _bufferEmpty, _shiftRegister, _bitsRemaining, _silenceFlag, _needToRun, unused_enableOverclockCounter);
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}
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bool DeltaModulationChannel::IrqPending(uint32_t cyclesToRun)
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{
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if(_irqEnabled && _bytesRemaining > 0) {
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uint32_t cyclesToEmptyBuffer = (_bitsRemaining + (_bytesRemaining-1)* 8) * _period;
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if(cyclesToRun >= cyclesToEmptyBuffer) {
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return true;
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}
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}
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return false;
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}
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bool DeltaModulationChannel::GetStatus()
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{
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return _bytesRemaining > 0;
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}
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void DeltaModulationChannel::GetMemoryRanges(MemoryRanges &ranges)
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{
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ranges.AddHandler(MemoryOperation::Write, 0x4010, 0x4013);
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}
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void DeltaModulationChannel::WriteRAM(uint16_t addr, uint8_t value)
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{
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APU::StaticRun();
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switch(addr & 0x03) {
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case 0: //4010
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_irqEnabled = (value & 0x80) == 0x80;
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_loopFlag = (value & 0x40) == 0x40;
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//"The rate determines for how many CPU cycles happen between changes in the output level during automatic delta-encoded sample playback."
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//Because BaseApuChannel does not decrement when setting _timer, we need to actually set the value to 1 less than the lookup table
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_period = (GetNesModel() == NesModel::NTSC ? _dmcPeriodLookupTableNtsc : _dmcPeriodLookupTablePal)[value & 0x0F] - 1;
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if(!_irqEnabled) {
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CPU::ClearIRQSource(IRQSource::DMC);
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}
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break;
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case 1: { //4011
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uint8_t newValue = value & 0x7F;
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uint8_t previousLevel = _outputLevel;
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_outputLevel = newValue;
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if(EmulationSettings::CheckFlag(EmulationFlags::ReduceDmcPopping) && abs(_outputLevel - previousLevel) > 50) {
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//Reduce popping sounds for 4011 writes
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_outputLevel -= (_outputLevel - previousLevel) / 2;
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}
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//4011 applies new output right away, not on the timer's reload. This fixes bad DMC sound when playing through 4011.
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AddOutput(_outputLevel);
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if(_lastValue4011 != value && newValue > 0) {
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Console::SetNextFrameOverclockStatus(true);
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}
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_lastValue4011 = newValue;
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break;
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}
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case 2: //4012
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_sampleAddr = 0xC000 | ((uint32_t)value << 6);
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if(value > 0) {
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Console::SetNextFrameOverclockStatus(false);
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}
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break;
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case 3: //4013
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_sampleLength = (value << 4) | 0x0001;
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if(value > 0) {
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Console::SetNextFrameOverclockStatus(false);
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}
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break;
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}
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}
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void DeltaModulationChannel::SetEnabled(bool enabled)
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{
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if(!enabled) {
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_bytesRemaining = 0;
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_needToRun = false;
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} else if(_bytesRemaining == 0) {
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InitSample();
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StartDmcTransfer();
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}
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}
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bool DeltaModulationChannel::NeedToRun()
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{
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return _needToRun;
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}
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void DeltaModulationChannel::SetReadBuffer()
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{
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Instance->FillReadBuffer();
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}
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ApuDmcState DeltaModulationChannel::GetState()
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{
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ApuDmcState state;
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state.BytesRemaining = _bytesRemaining;
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state.IrqEnabled = _irqEnabled;
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state.Loop = _loopFlag;
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state.OutputVolume = _lastOutput;
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state.Period = _period;
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state.SampleRate = CPU::GetClockRate(GetNesModel()) / (_period + 1);
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state.SampleAddr = _sampleAddr;
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state.SampleLength = _sampleLength;
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return state;
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} |