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Attempts an essentially-complete implementation of tone channels.

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This commit is contained in:
Thomas Harte 2021-06-26 23:39:59 -04:00
parent 90782d3c27
commit f8bb66d2a0
3 changed files with 49 additions and 22 deletions
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48
Machines/Enterprise/Dave.cpp
View File

@ -50,15 +50,35 @@ void Dave::set_sample_volume_range(int16_t range) {
}
void Dave::get_samples(std::size_t number_of_samples, int16_t *target) {
// Step 1: divide input clock to 125,000 Hz (?)
for(size_t c = 0; c < number_of_samples; c++) {
#define update_channel(x) \
if(!channels_[x].count) { \
channels_[x].output ^= true; \
channels_[x].count = channels_[x].reload; \
} else { \
--channels_[x].count; \
}
poly_state_[int(Channel::Distortion::FourBit)] = poly4_.next();
poly_state_[int(Channel::Distortion::FiveBit)] = poly5_.next();
poly_state_[int(Channel::Distortion::SevenBit)] = poly7_.next();
// TODO: substitute poly_state_[2] if polynomial substitution is in play.
#define update_channel(x) { \
auto output = channels_[x].output & 1; \
channels_[x].output <<= 1; \
if(!channels_[x].count) { \
channels_[x].count = channels_[x].reload; \
\
if(channels_[x].distortion == Channel::Distortion::None) \
output ^= 1; \
else \
output = poly_state_[int(channels_[x].distortion)]; \
\
if(channels_[x].high_pass && (channels_[(x+1)%3].output&3) == 2) { \
output = 0; \
} \
if(channels_[x].ring_modulate) { \
output = ~(output ^ channels_[(x+2)%3].output) & 1; \
} \
} else { \
--channels_[x].count; \
} \
channels_[x].output |= output; \
}
update_channel(0);
update_channel(1);
@ -69,16 +89,16 @@ void Dave::get_samples(std::size_t number_of_samples, int16_t *target) {
// Dumbest ever first attempt: sum channels.
target[(c << 1) + 0] =
volume_ * (
channels_[0].amplitude[0] * channels_[0].output +
channels_[1].amplitude[0] * channels_[1].output +
channels_[2].amplitude[0] * channels_[2].output
channels_[0].amplitude[0] * (channels_[0].output & 1) +
channels_[1].amplitude[0] * (channels_[1].output & 1) +
channels_[2].amplitude[0] * (channels_[2].output & 1)
);
target[(c << 1) + 1] =
volume_ * (
channels_[0].amplitude[1] * channels_[0].output +
channels_[1].amplitude[1] * channels_[1].output +
channels_[2].amplitude[1] * channels_[2].output
channels_[0].amplitude[1] * (channels_[0].output & 1) +
channels_[1].amplitude[1] * (channels_[1].output & 1) +
channels_[2].amplitude[1] * (channels_[2].output & 1)
);
}
}

17
Machines/Enterprise/Dave.hpp
View File

@ -41,27 +41,32 @@ class Dave: public Outputs::Speaker::SampleSource {
bool high_pass = false;
bool ring_modulate = false;
enum class Distortion {
None,
FourBit,
FiveBit,
SevenBit,
None = 0,
FourBit = 1,
FiveBit = 2,
SevenBit = 3,
} distortion = Distortion::None;
uint8_t amplitude[2]{};
// Current state.
uint16_t count = 0;
bool output = true;
int output = 0;
} channels_[3];
int16_t volume_ = 0;
// Various polynomials that contribute to audio generation.
// Polynomials that are always running.
Numeric::LFSRv<0xc> poly4_;
Numeric::LFSRv<0x14> poly5_;
Numeric::LFSRv<0x60> poly7_;
// The selectable, noise-related polynomial.
Numeric::LFSRv<0x110> poly9_;
Numeric::LFSRv<0x500> poly11_;
Numeric::LFSRv<0x6000> poly15_;
Numeric::LFSRv<0x12000> poly17_;
// Current state of the active polynomials.
uint8_t poly_state_[4];
};
}

6
Machines/Enterprise/Enterprise.cpp
View File

@ -210,7 +210,7 @@ template <bool has_disk_controller> class ConcreteMachine:
page<3>(0x00);
// Set up audio.
speaker_.set_input_rate(125000.0f); // TODO: a bigger number, and respect the programmable divider.
speaker_.set_input_rate(250000.0f); // TODO: a bigger number, and respect the programmable divider.
// Pass on any media.
insert_media(target.media);
@ -368,7 +368,9 @@ template <bool has_disk_controller> class ConcreteMachine:
}
inline void update_audio() {
speaker_.run_for(audio_queue_, time_since_audio_update_.divide_cycles(Cycles(32)));
// TODO: divide by only 8, letting Dave divide itself by a further 2 or 3
// as per its own register.
speaker_.run_for(audio_queue_, time_since_audio_update_.divide_cycles(Cycles(16)));
}
private: