mirror of
https://github.com/TomHarte/CLK.git
synced 2024-07-26 11:29:09 +00:00
80 lines
2.3 KiB
C++
80 lines
2.3 KiB
C++
//
|
|
// Audio.cpp
|
|
// Clock Signal
|
|
//
|
|
// Created by Thomas Harte on 31/05/2019.
|
|
// Copyright © 2019 Thomas Harte. All rights reserved.
|
|
//
|
|
|
|
#include "Audio.hpp"
|
|
|
|
using namespace Apple::Macintosh;
|
|
|
|
namespace {
|
|
|
|
// The sample_length is coupled with the clock rate selected within the Macintosh proper.
|
|
const std::size_t sample_length = 352 / 2;
|
|
|
|
}
|
|
|
|
Audio::Audio(Concurrency::DeferringAsyncTaskQueue &task_queue) : task_queue_(task_queue) {}
|
|
|
|
// MARK: - Inputs
|
|
|
|
void Audio::post_sample(uint8_t sample) {
|
|
// Store sample directly indexed by current write pointer; this ensures that collected samples
|
|
// directly map to volume and enabled/disabled states.
|
|
sample_queue_.buffer[sample_queue_.write_pointer] = sample;
|
|
sample_queue_.write_pointer = (sample_queue_.write_pointer + 1) % sample_queue_.buffer.size();
|
|
}
|
|
|
|
void Audio::set_volume(int volume) {
|
|
// Do nothing if the volume hasn't changed.
|
|
if(posted_volume_ == volume) return;
|
|
posted_volume_ = volume;
|
|
|
|
// Post the volume change as a deferred event.
|
|
task_queue_.defer([=] () {
|
|
volume_ = volume;
|
|
});
|
|
}
|
|
|
|
void Audio::set_enabled(bool on) {
|
|
// Do nothing if the mask hasn't changed.
|
|
if(posted_enable_mask_ == int(on)) return;
|
|
posted_enable_mask_ = int(on);
|
|
|
|
// Post the enabled mask change as a deferred event.
|
|
task_queue_.defer([=] () {
|
|
enabled_mask_ = int(on);
|
|
});
|
|
}
|
|
|
|
// MARK: - Output generation
|
|
|
|
bool Audio::is_zero_level() {
|
|
return !volume_ || !enabled_mask_;
|
|
}
|
|
|
|
void Audio::set_sample_volume_range(std::int16_t range) {
|
|
// Some underflow here doesn't really matter.
|
|
volume_multiplier_ = range / (7 * 255);
|
|
}
|
|
|
|
void Audio::get_samples(std::size_t number_of_samples, int16_t *target) {
|
|
// TODO: the implementation below acts as if the hardware uses pulse-amplitude modulation;
|
|
// in fact it uses pulse-width modulation. But the scale for pulses isn't specified, so
|
|
// that's something to return to.
|
|
|
|
// TODO: temporary implementation. Very inefficient. Replace.
|
|
for(std::size_t sample = 0; sample < number_of_samples; ++sample) {
|
|
target[sample] = volume_multiplier_ * int16_t(sample_queue_.buffer[sample_queue_.read_pointer] * volume_ * enabled_mask_);
|
|
++subcycle_offset_;
|
|
|
|
if(subcycle_offset_ == sample_length) {
|
|
subcycle_offset_ = 0;
|
|
sample_queue_.read_pointer = (sample_queue_.read_pointer + 1) % sample_queue_.buffer.size();
|
|
}
|
|
}
|
|
}
|