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376 lines
12 KiB
C++
376 lines
12 KiB
C++
//
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// Sound.cpp
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// Clock Signal
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//
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// Created by Thomas Harte on 04/11/2020.
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// Copyright © 2020 Thomas Harte. All rights reserved.
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//
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#include "Sound.hpp"
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#include <cassert>
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#include <cstdio>
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#include <numeric>
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// TODO: is it safe not to check for back-pressure in pending_stores_?
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using namespace Apple::IIgs::Sound;
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GLU::GLU(Concurrency::DeferringAsyncTaskQueue &audio_queue) : audio_queue_(audio_queue) {
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// Reset all pending stores.
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MemoryWrite disabled_write;
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disabled_write.enabled = false;
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for(int c = 0; c < StoreBufferSize; c++) {
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pending_stores_[c].store(disabled_write);
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}
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}
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void GLU::set_data(uint8_t data) {
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if(local_.control & 0x40) {
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// RAM access.
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local_.ram_[address_] = data;
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MemoryWrite write;
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write.enabled = true;
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write.address = address_;
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write.value = data;
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write.time = pending_store_write_time_;
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pending_stores_[pending_store_write_].store(write, std::memory_order::memory_order_release);
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pending_store_write_ = (pending_store_write_ + 1) % (StoreBufferSize - 1);
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} else {
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// Register access.
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const auto address = address_; // To make sure I don't inadvertently 'capture' address_.
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local_.set_register(address, data);
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audio_queue_.defer([this, address, data] () {
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remote_.set_register(address, data);
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});
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}
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if(local_.control & 0x20) {
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++address_;
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}
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}
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void GLU::EnsoniqState::set_register(uint16_t address, uint8_t value) {
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switch(address & 0xe0) {
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case 0x00:
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oscillators[address & 0x1f].velocity = uint16_t((oscillators[address & 0x1f].velocity & 0xff00) | (value << 0));
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break;
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case 0x20:
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oscillators[address & 0x1f].velocity = uint16_t((oscillators[address & 0x1f].velocity & 0x00ff) | (value << 8));
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break;
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case 0x40:
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oscillators[address & 0x1f].volume = value;
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break;
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case 0x60:
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/* Does setting the last sample make any sense? */
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break;
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case 0x80:
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oscillators[address & 0x1f].address = value;
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break;
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case 0xa0: {
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oscillators[address & 0x1f].control = value;
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// Halt + M0 => reset position.
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if((oscillators[address & 0x1f].control & 0x3) == 3) {
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oscillators[address & 0x1f].control |= 1;
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}
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} break;
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case 0xc0:
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oscillators[address & 0x1f].table_size = value;
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// The most-significant bit that should be used is 16 + (value & 7).
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oscillators[address & 0x1f].overflow_mask = ~(0xffffff >> (7 - (value & 7)));
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break;
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default:
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switch(address & 0xff) {
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case 0xe0:
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/* Does setting the interrupt register really make any sense? */
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break;
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case 0xe1:
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oscillator_count = 1 + ((value >> 1) & 31);
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break;
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case 0xe2:
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/* Writing to the analogue to digital input definitely makes no sense. */
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break;
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}
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break;
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}
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}
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uint8_t GLU::get_data() {
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const auto address = address_;
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if(local_.control & 0x20) {
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++address_;
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}
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switch(address & 0xe0) {
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case 0x00: return local_.oscillators[address & 0x1f].velocity & 0xff;
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case 0x20: return local_.oscillators[address & 0x1f].velocity >> 8;;
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case 0x40: return local_.oscillators[address & 0x1f].volume;
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case 0x60: return local_.oscillators[address & 0x1f].sample(local_.ram_); // i.e. look up what the sample was on demand.
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case 0x80: return local_.oscillators[address & 0x1f].address;
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case 0xa0: return local_.oscillators[address & 0x1f].control;
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case 0xc0: return local_.oscillators[address & 0x1f].table_size;
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default:
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switch(address & 0xff) {
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case 0xe0: {
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// Find the first enabled oscillator that is signalling an interrupt and has interrupts enabled.
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for(int c = 0; c < local_.oscillator_count; c++) {
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if(local_.oscillators[c].interrupt_request && (local_.oscillators[c].control & 0x08)) {
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local_.oscillators[c].interrupt_request = false;
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return uint8_t(0x41 | (c << 1));
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}
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}
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// No interrupt found.
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return 0xc1;
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} break;
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case 0xe1: return uint8_t((local_.oscillator_count - 1) << 1); // TODO: should other bits be 0 or 1?
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case 0xe2: return 128; // Input audio. Unimplemented!
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}
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break;
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}
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return 0;
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}
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bool GLU::get_interrupt_line() {
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// Return @c true if any oscillator currently has its interrupt request
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// set, and has interrupts enabled.
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for(int c = 0; c < local_.oscillator_count; c++) {
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if(local_.oscillators[c].interrupt_request && (local_.oscillators[c].control & 0x08)) {
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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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// MARK: - Time entry points.
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void GLU::run_for(Cycles cycles) {
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// Update local state, without generating audio.
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skip_audio(local_, cycles.as<size_t>());
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// Update the timestamp for memory writes;
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pending_store_write_time_ += cycles.as<uint32_t>();
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}
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void GLU::get_samples(std::size_t number_of_samples, std::int16_t *target) {
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// Update remote state, generating audio.
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generate_audio(number_of_samples, target);
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}
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void GLU::skip_samples(const std::size_t number_of_samples) {
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// Update remote state, without generating audio.
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skip_audio(remote_, number_of_samples);
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// Apply any pending stores.
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std::atomic_thread_fence(std::memory_order::memory_order_acquire);
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const uint32_t final_time = pending_store_read_time_ + uint32_t(number_of_samples);
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while(true) {
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auto next_store = pending_stores_[pending_store_read_].load(std::memory_order::memory_order_acquire);
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if(!next_store.enabled) break;
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if(next_store.time >= final_time) break;
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remote_.ram_[next_store.address] = next_store.value;
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next_store.enabled = false;
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pending_stores_[pending_store_read_].store(next_store, std::memory_order::memory_order_relaxed);
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pending_store_read_ = (pending_store_read_ + 1) & (StoreBufferSize - 1);
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}
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}
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void GLU::set_sample_volume_range(std::int16_t range) {
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output_range_ = range;
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}
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// MARK: - Interface boilerplate.
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void GLU::set_control(uint8_t control) {
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local_.control = control;
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audio_queue_.defer([this, control] () {
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remote_.control = control;
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});
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}
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uint8_t GLU::get_control() {
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return local_.control;
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}
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void GLU::set_address_low(uint8_t low) {
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address_ = uint16_t((address_ & 0xff00) | low);
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}
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uint8_t GLU::get_address_low() {
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return address_ & 0xff;
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}
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void GLU::set_address_high(uint8_t high) {
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address_ = uint16_t((high << 8) | (address_ & 0x00ff));
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}
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uint8_t GLU::get_address_high() {
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return address_ >> 8;
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}
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// MARK: - Update logic.
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Cycles GLU::get_next_sequence_point() const {
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uint32_t result = std::numeric_limits<decltype(result)>::max();
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for(int c = 0; c < local_.oscillator_count; c++) {
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// Don't do anything for halted oscillators, or for oscillators that can't hit stops.
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if((local_.oscillators[c].control&3) != 2) {
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continue;
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}
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// Determine how many cycles until a stop is hit and update the pending result
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// if this is the new soonest-to-expire oscillator.
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const auto first_overflow_value = (local_.oscillators[c].overflow_mask - 1) << 1;
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const auto time_until_stop = (first_overflow_value - local_.oscillators[c].position + local_.oscillators[c].velocity - 1) / local_.oscillators[c].velocity;
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result = std::min(result, time_until_stop);
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}
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return Cycles(result);
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}
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void GLU::skip_audio(EnsoniqState &state, size_t number_of_samples) {
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// Just advance all oscillator pointers and check for interrupts.
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// If a read occurs to the current-output level, generate it then.
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for(int c = 0; c < state.oscillator_count; c++) {
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// Don't do anything for halted oscillators.
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if(state.oscillators[c].control&1) continue;
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// Update phase.
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state.oscillators[c].position += state.oscillators[c].velocity * number_of_samples;
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// Check for stops, and any interrupts that therefore flow.
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if((state.oscillators[c].control & 2) && (state.oscillators[c].position & state.oscillators[c].overflow_mask)) {
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// Apply halt, set interrupt request flag.
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state.oscillators[c].position = 0;
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state.oscillators[c].control |= 1;
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state.oscillators[c].interrupt_request = true;
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}
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}
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}
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void GLU::generate_audio(size_t number_of_samples, std::int16_t *target) {
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auto next_store = pending_stores_[pending_store_read_].load(std::memory_order::memory_order_acquire);
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uint8_t next_amplitude = 255;
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for(size_t sample = 0; sample < number_of_samples; sample++) {
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// TODO: there's a bit of a hack here where it is assumed that the input clock has been
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// divided in advance. Real hardware divides by 8, I think?
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// Seed output as 0.
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int output = 0;
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// Apply phase updates to all enabled oscillators.
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for(int c = 0; c < remote_.oscillator_count; c++) {
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// Don't do anything for halted oscillators.
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if(remote_.oscillators[c].control&1) continue;
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remote_.oscillators[c].position += remote_.oscillators[c].velocity;
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// Test for a new halting event.
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switch(remote_.oscillators[c].control & 6) {
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case 0: // Free-run mode; don't truncate the position at all, in case the
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// accumulator bits in use changes.
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output += remote_.oscillators[c].output(remote_.ram_);
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break;
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case 2: // One-shot mode; check for end of run. Otherwise update sample.
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if(remote_.oscillators[c].position & remote_.oscillators[c].overflow_mask) {
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remote_.oscillators[c].position = 0;
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remote_.oscillators[c].control |= 1;
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}
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break;
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case 4: // Sync/AM mode.
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if(c&1) {
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// Oscillator is odd-numbered; it will amplitude-modulate the next voice.
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next_amplitude = remote_.oscillators[c].sample(remote_.ram_);
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continue;
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} else {
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// Oscillator is even-numbered; it will 'sync' to the even voice, i.e. any
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// time it wraps around, it will reset the next oscillator.
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if(remote_.oscillators[c].position & remote_.oscillators[c].overflow_mask) {
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remote_.oscillators[c].position &= remote_.oscillators[c].overflow_mask;
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remote_.oscillators[c+1].position = 0;
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}
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}
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break;
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case 6: // Swap mode; possibly trigger partner, and update sample.
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// Per tech note #11: "Whenever a swap occurs from a higher-numbered
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// oscillator to a lower-numbered one, the output signal from the corresponding
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// generator temporarily falls to the zero-crossing level (silence)"
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if(remote_.oscillators[c].position & remote_.oscillators[c].overflow_mask) {
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remote_.oscillators[c].control |= 1;
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remote_.oscillators[c].position = 0;
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remote_.oscillators[c^1].control &= ~1;
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}
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break;
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}
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// Don't add output for newly-halted oscillators.
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if(remote_.oscillators[c].control&1) continue;
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// Append new output.
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output += (remote_.oscillators[c].output(remote_.ram_) * next_amplitude) / 255;
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next_amplitude = 255;
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}
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// Maximum total output was 32 channels times a 16-bit range. Map that down.
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// TODO: dynamic total volume?
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target[sample] = (output * output_range_) >> 20;
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// Apply any RAM writes that interleave here.
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++pending_store_read_time_;
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if(!next_store.enabled) continue;
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if(next_store.time != pending_store_read_time_) continue;
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remote_.ram_[next_store.address] = next_store.value;
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next_store.enabled = false;
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pending_stores_[pending_store_read_].store(next_store, std::memory_order::memory_order_relaxed);
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pending_store_read_ = (pending_store_read_ + 1) & (StoreBufferSize - 1);
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}
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}
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uint8_t GLU::EnsoniqState::Oscillator::sample(uint8_t *ram) {
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// Determines how many you'd have to shift a 16-bit pointer to the right for,
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// in order to hit only the position-supplied bits.
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const int pointer_shift = 8 - ((table_size >> 3) & 7);
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// Table size mask should be 0x8000 for the largest table size, and 0xff00 for
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// the smallest.
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const uint16_t table_size_mask = 0xffff >> pointer_shift;
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// The pointer should use (at most) 15 bits; starting with bit 1 for resolution 0
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// and starting at bit 8 for resolution 7.
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const uint16_t table_pointer = uint16_t(position >> ((table_size&7) + pointer_shift));
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// The full pointer is composed of the bits of the programmed address not touched by
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// the table pointer, plus the table pointer.
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const uint16_t sample_address = ((address << 8) & ~table_size_mask) | (table_pointer & table_size_mask);
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// Ignored here: bit 6 should select between RAM banks. But for now this is IIgs-centric,
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// and that has only one bank of RAM.
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return ram[sample_address];
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}
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int16_t GLU::EnsoniqState::Oscillator::output(uint8_t *ram) {
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const auto level = sample(ram);
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// "An oscillator will halt when a zero is encountered in its waveform table."
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// TODO: only if in free-run mode, I think? Or?
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if(!level) {
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control |= 1;
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return 0;
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}
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// Samples are unsigned 8-bit; do the proper work to make volume work correctly.
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return int8_t(level ^ 128) * volume;
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}
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