mirror of
https://github.com/libretro/Mesen.git
synced 2024-11-27 19:10:21 +00:00
099a1b3b44
-Fixed DMC $4011 write behavior -Fixed period for square channels -Removed blip_buffer & blip_synth. Replaced with blip_buf and SoundMixer - now have non-linear sound mixing. -Fixes all sound-related tests (apu_mixer (dmc, noise, square, triangle) and volume_tests
86 lines
2.1 KiB
C++
86 lines
2.1 KiB
C++
#pragma once
|
|
#include "stdafx.h"
|
|
#include "APU.h"
|
|
#include "IMemoryHandler.h"
|
|
#include "ApuEnvelope.h"
|
|
|
|
class NoiseChannel : public ApuEnvelope
|
|
{
|
|
private:
|
|
const vector<uint16_t> _noisePeriodLookupTableNtsc = { { 4, 8, 16, 32, 64, 96, 128, 160, 202, 254, 380, 508, 762, 1016, 2034, 4068 } };
|
|
const vector<uint16_t> _noisePeriodLookupTablePal = { { 4, 8, 14, 30, 60, 88, 118, 148, 188, 236, 354, 472, 708, 944, 1890, 3778 } };
|
|
|
|
//On power-up, the shift register is loaded with the value 1.
|
|
uint16_t _shiftRegister = 1;
|
|
bool _modeFlag = false;
|
|
|
|
bool IsMuted()
|
|
{
|
|
//The mixer receives the current envelope volume except when Bit 0 of the shift register is set, or The length counter is zero
|
|
return (_shiftRegister & 0x01) == 0x01;
|
|
}
|
|
|
|
protected:
|
|
void Clock()
|
|
{
|
|
//Feedback is calculated as the exclusive-OR of bit 0 and one other bit: bit 6 if Mode flag is set, otherwise bit 1.
|
|
uint16_t feedback = (_shiftRegister & 0x01) ^ ((_shiftRegister >> (_modeFlag ? 6 : 1)) & 0x01);
|
|
_shiftRegister >>= 1;
|
|
_shiftRegister |= (feedback << 14);
|
|
|
|
if(IsMuted()) {
|
|
AddOutput(0);
|
|
} else {
|
|
AddOutput(GetVolume());
|
|
}
|
|
}
|
|
|
|
public:
|
|
NoiseChannel(AudioChannel channel, SoundMixer* mixer) : ApuEnvelope(channel, mixer)
|
|
{
|
|
}
|
|
|
|
virtual void Reset(bool softReset)
|
|
{
|
|
ApuEnvelope::Reset(softReset);
|
|
|
|
_shiftRegister = 1;
|
|
_modeFlag = false;
|
|
}
|
|
|
|
virtual void StreamState(bool saving)
|
|
{
|
|
ApuEnvelope::StreamState(saving);
|
|
|
|
Stream<uint16_t>(_shiftRegister);
|
|
Stream<bool>(_modeFlag);
|
|
}
|
|
|
|
void GetMemoryRanges(MemoryRanges &ranges)
|
|
{
|
|
ranges.AddHandler(MemoryOperation::Write, 0x400C, 0x400F);
|
|
}
|
|
|
|
void WriteRAM(uint16_t addr, uint8_t value)
|
|
{
|
|
APU::StaticRun();
|
|
switch(addr & 0x03) {
|
|
case 0: //400C
|
|
InitializeLengthCounter((value & 0x20) == 0x20);
|
|
InitializeEnvelope(value);
|
|
break;
|
|
|
|
case 2: //400E
|
|
_period = (GetNesModel() == NesModel::NTSC ? _noisePeriodLookupTableNtsc : _noisePeriodLookupTablePal)[value & 0x0F] - 1;
|
|
_modeFlag = (value & 0x80) == 0x80;
|
|
break;
|
|
|
|
case 3: //400F
|
|
LoadLengthCounter(value >> 3);
|
|
|
|
//The envelope is also restarted.
|
|
ResetEnvelope();
|
|
break;
|
|
}
|
|
}
|
|
}; |