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Adjusts the AY volume scale.

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Hopefully more accurately to model the real thing.
This commit is contained in:
Thomas Harte 2020-02-14 22:51:20 -05:00
parent 65e6c3a9fe
commit 6810a6ee58
1 changed files with 11 additions and 9 deletions
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20
Components/AY38910/AY38910.cpp
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@ -71,11 +71,13 @@ AY38910::AY38910(Personality personality, Concurrency::DeferringAsyncTaskQueue &
}
void AY38910::set_sample_volume_range(std::int16_t range) {
// set up volume lookup table
// Set up volume lookup table; the function below is based on a combination of the graph
// from the YM's datasheet, showing a clear power curve, and fitting that to observed
// values reported elsewhere.
const float max_volume = float(range) / 3.0f; // As there are three channels.
constexpr float root_two = 1.414213562373095f;
for(int v = 0; v < 32; v++) {
volumes_[v] = int(max_volume / powf(root_two, float(v ^ 0x1f) / 2.0f));
volumes_[v] = int(max_volume / powf(root_two, float(v ^ 0x1f) / 3.18f));
}
volumes_[0] = 0; // Tie level 0 to silence.
evaluate_output_volume();
@ -185,7 +187,7 @@ void AY38910::evaluate_output_volume() {
#undef channel_volume
// Mix additively.
output_volume_ = static_cast<int16_t>(
output_volume_ = int16_t(
volumes_[volumes[0]] * channel_levels[0] +
volumes_[volumes[1]] * channel_levels[1] +
volumes_[volumes[2]] * channel_levels[2]
@ -220,7 +222,7 @@ void AY38910::set_register_value(uint8_t value) {
int channel = selected_register >> 1;
if(selected_register & 1)
tone_periods_[channel] = (tone_periods_[channel] & 0xff) | static_cast<uint16_t>((value&0xf) << 8);
tone_periods_[channel] = (tone_periods_[channel] & 0xff) | uint16_t((value&0xf) << 8);
else
tone_periods_[channel] = (tone_periods_[channel] & ~0xff) | value;
}
@ -235,7 +237,7 @@ void AY38910::set_register_value(uint8_t value) {
break;
case 12:
envelope_period_ = (envelope_period_ & 0xff) | static_cast<int>(value << 8);
envelope_period_ = (envelope_period_ & 0xff) | int(value << 8);
break;
case 13:
@ -331,15 +333,15 @@ uint8_t AY38910::get_data_output() {
}
void AY38910::set_control_lines(ControlLines control_lines) {
switch(static_cast<int>(control_lines)) {
switch(int(control_lines)) {
default: control_state_ = Inactive; break;
case static_cast<int>(BDIR | BC2 | BC1):
case int(BDIR | BC2 | BC1):
case BDIR:
case BC1: control_state_ = LatchAddress; break;
case static_cast<int>(BC2 | BC1): control_state_ = Read; break;
case static_cast<int>(BDIR | BC2): control_state_ = Write; break;
case int(BC2 | BC1): control_state_ = Read; break;
case int(BDIR | BC2): control_state_ = Write; break;
}
update_bus();