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In theory provides a full implementation of audio.

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Albeit seemingly ineffective.
This commit is contained in:
Thomas Harte 2019-06-01 15:44:29 -04:00
parent 17635da812
commit 5c08bb810e
3 changed files with 46 additions and 5 deletions
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45
Machines/Apple/Macintosh/Audio.cpp
View File

@ -11,7 +11,7 @@
using namespace Apple::Macintosh;
namespace {
const HalfCycles sample_length(704);
const std::size_t sample_length = 352;
}
Audio::Audio(Concurrency::DeferringAsyncTaskQueue &task_queue) : task_queue_(task_queue) {}
@ -52,13 +52,50 @@ bool Audio::is_zero_level() {
void Audio::set_sample_volume_range(std::int16_t range) {
// Some underflow here doesn't really matter.
volume_multiplier_ = range / 7;
volume_multiplier_ = range / (7 * 255);
}
void Audio::get_samples(std::size_t number_of_samples, int16_t *target) {
// TODO.
const auto write_pointer = sample_queue_.write_pointer.load();
auto read_pointer = sample_queue_.read_pointer.load();
// 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.
while(number_of_samples--) {
*target = volume_multiplier_ * int16_t(sample_queue_.buffer[read_pointer] * volume_ * enabled_mask_);
++target;
++subcycle_offset_;
if(subcycle_offset_ == sample_length) {
// printf("%d: %d\n", sample_queue_.buffer[read_pointer], volume_multiplier_ * sample_queue_.buffer[read_pointer] * volume_ * enabled_mask_);
subcycle_offset_ = 0;
const unsigned int next_read_pointer = (read_pointer + 1) % sample_queue_.buffer.size();
if(next_read_pointer != write_pointer) {
read_pointer = next_read_pointer;
}
}
}
sample_queue_.read_pointer.store(read_pointer);
}
void Audio::skip_samples(std::size_t number_of_samples) {
// TODO.
const auto write_pointer = sample_queue_.write_pointer.load();
auto read_pointer = sample_queue_.read_pointer.load();
// Number of samples that would be consumed is (number_of_samples + subcycle_offset_) / sample_length.
const unsigned int samples_passed = static_cast<unsigned int>((number_of_samples + subcycle_offset_) / sample_length);
subcycle_offset_ = (number_of_samples + subcycle_offset_) % sample_length;
// Get also number of samples available.
const unsigned int samples_available = static_cast<unsigned int>((write_pointer + sample_queue_.buffer.size() - read_pointer) % sample_queue_.buffer.size());
// Advance by whichever of those is the lower number.
const auto samples_to_consume = std::min(samples_available, samples_passed);
read_pointer = (read_pointer + samples_to_consume) % sample_queue_.buffer.size();
sample_queue_.read_pointer.store(read_pointer);
}

2
Machines/Apple/Macintosh/Audio.hpp
View File

@ -72,7 +72,7 @@ class Audio: public ::Outputs::Speaker::SampleSource {
std::int16_t volume_multiplier_ = 0;
HalfCycles subcycle_offset_;
std::size_t subcycle_offset_;
};
}

4
Machines/Apple/Macintosh/Macintosh.cpp
View File

@ -340,6 +340,10 @@ class ConcreteMachine:
if(port == Port::B && line == Line::Two) keyboard_.set_input(value);
}
void run_for(HalfCycles duration) {
audio_.time_since_update += duration;
}
private:
ConcreteMachine &machine_;
RealTimeClock &clock_;