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Adds optional stereo output for the AY.

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The real chip provides the three tone channels as separate outputs, so a variety of different mixings can exist.
This commit is contained in:
Thomas Harte
2020-02-15 18:09:17 -05:00
parent e02d109864
commit 89d6b85b83
2 changed files with 85 additions and 14 deletions
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Components/AY38910/AY38910.cpp
+61 -12
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@@ -84,10 +84,33 @@ void AY38910::set_sample_volume_range(std::int16_t range) {
for(int v = 31; v >= 0; --v) {
volumes_[v] -= volumes_[0];
}
evaluate_output_volume();
if(is_stereo_) {
evaluate_output_volume<true>();
} else {
evaluate_output_volume<false>();
}
}
void AY38910::set_output_mixing(bool is_stereo, float a_left, float b_left, float c_left, float a_right, float b_right, float c_right) {
is_stereo_ = is_stereo;
a_left_ = uint8_t(a_left * 255.0f);
b_left_ = uint8_t(b_left * 255.0f);
c_left_ = uint8_t(c_left * 255.0f);
a_right_ = uint8_t(a_right * 255.0f);
b_right_ = uint8_t(b_right * 255.0f);
c_right_ = uint8_t(c_right * 255.0f);
}
void AY38910::get_samples(std::size_t number_of_samples, int16_t *target) {
if(is_stereo_) {
get_samples<true>(number_of_samples, target);
} else {
get_samples<false>(number_of_samples, target);
}
}
template <bool is_stereo> void AY38910::get_samples(std::size_t number_of_samples, int16_t *target) {
// Note on structure below: the real AY has a built-in divider of 8
// prior to applying its tone and noise dividers. But the YM fills the
// same total periods for noise and tone with double-precision envelopes.
@@ -99,7 +122,11 @@ void AY38910::get_samples(std::size_t number_of_samples, int16_t *target) {
std::size_t c = 0;
while((master_divider_&3) && c < number_of_samples) {
target[c] = output_volume_;
if constexpr (is_stereo) {
reinterpret_cast<uint32_t *>(target)[c] = output_volume_;
} else {
target[c] = output_volume_;
}
master_divider_++;
c++;
}
@@ -138,10 +165,14 @@ void AY38910::get_samples(std::size_t number_of_samples, int16_t *target) {
if(envelope_position_ == 64) envelope_position_ = envelope_overflow_masks_[output_registers_[13]];
}
evaluate_output_volume();
evaluate_output_volume<is_stereo>();
for(int ic = 0; ic < 4 && c < number_of_samples; ic++) {
target[c] = output_volume_;
if constexpr (is_stereo) {
reinterpret_cast<uint32_t *>(target)[c] = output_volume_;
} else {
target[c] = output_volume_;
}
c++;
master_divider_++;
}
@@ -150,7 +181,7 @@ void AY38910::get_samples(std::size_t number_of_samples, int16_t *target) {
master_divider_ &= 3;
}
void AY38910::evaluate_output_volume() {
template <bool is_stereo> void AY38910::evaluate_output_volume() {
int envelope_volume = envelope_shapes_[output_registers_[13]][envelope_position_ | envelope_position_mask_];
// The output level for a channel is:
@@ -190,12 +221,26 @@ void AY38910::evaluate_output_volume() {
};
#undef channel_volume
// Mix additively.
output_volume_ = int16_t(
volumes_[volumes[0]] * channel_levels[0] +
volumes_[volumes[1]] * channel_levels[1] +
volumes_[volumes[2]] * channel_levels[2]
);
// Mix additively, weighting if in stereo.
if constexpr (is_stereo) {
int16_t *const volumes = reinterpret_cast<int16_t *>(&output_volume_);
volumes[0] = int16_t((
volumes_[volumes[0]] * channel_levels[0] * a_left_ +
volumes_[volumes[1]] * channel_levels[1] * b_left_ +
volumes_[volumes[2]] * channel_levels[2] * c_left_
) >> 8);
volumes[1] = int16_t((
volumes_[volumes[0]] * channel_levels[0] * a_right_ +
volumes_[volumes[1]] * channel_levels[1] * b_right_ +
volumes_[volumes[2]] * channel_levels[2] * c_right_
) >> 8);
} else {
output_volume_ = int16_t(
volumes_[volumes[0]] * channel_levels[0] +
volumes_[volumes[1]] * channel_levels[1] +
volumes_[volumes[2]] * channel_levels[2]
);
}
}
bool AY38910::is_zero_level() {
@@ -252,7 +297,11 @@ void AY38910::set_register_value(uint8_t value) {
// Store a copy of the current register within the storage used by the audio generation
// thread, and apply any changes to output volume.
output_registers_[selected_register] = masked_value;
evaluate_output_volume();
if(is_stereo_) {
evaluate_output_volume<true>();
} else {
evaluate_output_volume<false>();
}
});
}