Mesen/Core/DeltaModulationChannel.cpp

227 lines
5.6 KiB
C++

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