a22b17b2c1
In hardware, the audio from the 2A03 APU pins go through an inverted preamp using one of the 74HCU04 inverter chips in the motherboard. Though this may be cost-effective on Nintendo's part, the signals on the hex inverter chip can interfere with one another, especially on the audio. This can be heard as a buzz or a high pitched whine. The only known signals to interfere with the audio so far is: - /A13, the inverted signal of PPU A13 going into the cartridge connector. - /OE1, Output enable for controller reads, though this is only found present on the RF Famicom.
41 lines
No EOL
742 B
C++
41 lines
No EOL
742 B
C++
#pragma once
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#include "stdafx.h"
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#include "Snapshotable.h"
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#include "APU.h"
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#include "BaseExpansionAudio.h"
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#include "Console.h"
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#include <array>
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class InvA13Audio : public BaseExpansionAudio
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{
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private:
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int8_t _currentOutput;
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int8_t _lastOutput;
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void UpdateOutputLevel()
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{
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if (_currentOutput != _lastOutput) {
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_console->GetApu()->AddExpansionAudioDelta(AudioChannel::InvA13, _currentOutput - _lastOutput);
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_lastOutput = _currentOutput;
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}
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}
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protected:
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void StreamState(bool saving) override
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{
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}
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void ClockAudio() override
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{
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_currentOutput = _console->_InvA13;
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UpdateOutputLevel();
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}
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public:
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InvA13Audio(shared_ptr<Console> console) : BaseExpansionAudio(console)
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{
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_lastOutput = 0;
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_currentOutput = 0;
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}
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}; |