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Switch to PWM implementation, with noise.

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This commit is contained in:
Thomas Harte
2025-01-08 22:09:42 -05:00
parent 65307186dc
commit e1ae65b6d1
1 changed files with 69 additions and 45 deletions
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Machines/Commodore/Plus4/Audio.hpp
+69 -45
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@@ -13,14 +13,6 @@
namespace Commodore::Plus4 {
// PAL: / 160 i.e. 5*32
// NTSC: / 128 i.e. 4*32
// 111860.78125 = NTSC
// 110840.46875 = PAL
//
class Audio: public Outputs::Speaker::BufferSource<Audio, false> {
public:
Audio(Concurrency::AsyncTaskQueue<false> &audio_queue) :
@@ -28,64 +20,94 @@ public:
template <Outputs::Speaker::Action action>
void apply_samples(std::size_t size, Outputs::Speaker::MonoSample *const target) {
const auto count_frequency = [&](int index) {
++counts_[index];
if(counts_[index] == (frequencies_[index] ^ 1023) * frequency_multiplier_) {
states_[index] ^= 1;
counts_[index] = 0;
} else if(counts_[index] == 1024 * frequency_multiplier_) {
counts_[index] = 0;
// Divide by frequency_multiplier_ and multiply by 8 to get the "8Mhz clock".
// Each 32-window cycle of that clock is a single complete tick of the audio engine.
const auto update_channel = [&](int channel) {
if(sound_dc_ || channels_[channel].count == 0x3ff) {
channels_[channel].count = (channels_[channel].frequency + 1) & 0x3ff;
} else {
++channels_[channel].count;
if(channels_[channel].count == 0x3ff) {
channels_[channel].state ^= 1;
}
}
channels_[channel].pwm_count = 0;
};
if(sound_dc_) {
Outputs::Speaker::fill<action>(target, target + size, Outputs::Speaker::MonoSample(volume_ * 2));
} else {
// TODO: noise generation.
const auto update_noise = [&] {
noise_ <<= 1;
noise_ |= 1 ^ (noise_ >> 7) ^ (noise_ >> 5) ^ (noise_ >> 4) ^ (noise_ >> 1);
};
for(size_t c = 0; c < size; c++) {
count_frequency(0);
count_frequency(1);
for(size_t c = 0; c < size; c++) {
subcycle_ = (subcycle_ + 1) & 31;
Outputs::Speaker::apply<action>(
target[c],
Outputs::Speaker::MonoSample(
(
((states_[0] & masks_[0]) * external_volume_) +
((states_[1] & masks_[1]) * external_volume_)
) * volume_
));
if(subcycle_ == 0) update_channel(0);
if(subcycle_ == 16) {
update_channel(1);
update_noise();
}
++ channels_[0].pwm_count;
++ channels_[1].pwm_count;
if(sound_dc_) {
channels_[0].state = 0;
channels_[1].state = 0;
noise_ = 0;
}
target[c] =
external_volume_ * (
((channels_[0].pwm_count < volume_) & channels_[0].enabled & ~channels_[0].state) |
((channels_[1].pwm_count < volume_) &
(
(channels_[1].enabled & ~channels_[1].state) |
(sound2_noise_on_ & noise_ & 1)
)
)
);
}
r_ += size;
}
void set_sample_volume_range(const std::int16_t range) {
external_volume_ = range / (2 * 9); // Two channels and nine output levels.
external_volume_ = range; // / (2 * 9); // Two channels and nine output levels.
}
bool is_zero_level() const {
return !(masks_[0] || masks_[1] || sound2_noise_on_) || !volume_;
return !(channels_[0].enabled || channels_[1].enabled || sound2_noise_on_) || !volume_;
}
template <int channel> void set_frequency_low(uint8_t value) {
audio_queue_.enqueue([this, value] {
frequencies_[channel] = (frequencies_[channel] & 0xff00) | value;
channels_[channel].frequency = (channels_[channel].frequency & 0xff00) | value;
});
}
template <int channel> void set_frequency_high(uint8_t value) {
audio_queue_.enqueue([this, value] {
frequencies_[channel] = (frequencies_[channel] & 0x00ff) | ((value&3) << 8);
channels_[channel].frequency = (channels_[channel].frequency & 0x00ff) | ((value&3) << 8);
});
}
void set_control(const uint8_t value) {
audio_queue_.enqueue([this, value] {
switch(value & 0xf) {
case 0: volume_ = 31; break;
case 1: volume_ = 30; break;
case 2: volume_ = 28; break;
case 3: volume_ = 26; break;
case 4: volume_ = 24; break;
case 5: volume_ = 22; break;
case 6: volume_ = 20; break;
case 7: volume_ = 18; break;
default: volume_ = 16; break;
}
volume_ = std::min(value & 0xf, 8); // Only nine volumes are available.
masks_[0] = (value & 0x10) ? 1 : 0;
masks_[1] = (value & 0x20) ? 1 : 0;
channels_[0].enabled = (value & 0x10) ? 1 : 0;
channels_[1].enabled = (value & 0x20) ? 1 : 0;
sound2_noise_on_ = (value & 0x40) && !(value & 0x20);
sound_dc_ = value & 0x80;
@@ -104,18 +126,20 @@ private:
// Audio-thread state.
int16_t external_volume_ = 0;
int frequencies_[2]{};
int frequency_multiplier_ = 5;
int counts_[2]{};
int states_[2]{};
int masks_[2]{};
int subcycle_ = 0;
struct Channel {
int frequency = 0;
int count = 0;
int pwm_count = 0;
int state = 0;
int enabled = 0;
} channels_[2];
uint8_t noise_ = 0;
bool sound2_noise_on_ = false;
bool sound_dc_ = false;
int volume_ = 0;
int r_ = 0;
};
}