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Clean up commentary.

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This commit is contained in:
Thomas Harte 2024-02-13 13:46:27 -05:00
parent 1bb82189e9
commit a3e104f8e2
2 changed files with 19 additions and 11 deletions
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23
Components/AY38910/AY38910.cpp
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@ -12,6 +12,15 @@
using namespace GI::AY38910;
// Note on dividers: 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.
// Therefore this class implements a divider of 4 and doubles the tone
// and noise periods. The envelope ticks along at the divide-by-four rate,
// but if this is an AY rather than a YM then its lowest bit is forced to 1,
// matching the YM datasheet's depiction of envelope level 31 as equal to
// programmatic volume 15, envelope level 29 as equal to programmatic 14, etc.
template <bool is_stereo>
AY38910SampleSource<is_stereo>::AY38910SampleSource(Personality personality, Concurrency::AsyncTaskQueue<false> &task_queue) : task_queue_(task_queue) {
// Don't use the low bit of the envelope position if this is an AY.
@ -101,15 +110,6 @@ void AY38910SampleSource<is_stereo>::set_output_mixing(float a_left, float b_lef
c_right_ = uint8_t(c_right * 255.0f);
}
// 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.
// Therefore this class implements a divider of 4 and doubles the tone
// and noise periods. The envelope ticks along at the divide-by-four rate,
// but if this is an AY rather than a YM then its lowest bit is forced to 1,
// matching the YM datasheet's depiction of envelope level 31 as equal to
// programmatic volume 15, envelope level 29 as equal to programmatic 14, etc.
template <bool is_stereo>
void AY38910SampleSource<is_stereo>::advance() {
const auto step_channel = [&](int c) {
@ -391,3 +391,8 @@ void AY38910SampleSource<is_stereo>::update_bus() {
// Ensure both mono and stereo versions of the AY are built.
template class GI::AY38910::AY38910SampleSource<true>;
template class GI::AY38910::AY38910SampleSource<false>;
// Perform an explicit instantiation of the BufferSource to hope for
// appropriate inlining of advance() and level().
template struct GI::AY38910::AY38910<true>;
template struct GI::AY38910::AY38910<false>;

7
Components/AY38910/AY38910.hpp
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@ -164,8 +164,11 @@ template <bool stereo> class AY38910SampleSource {
friend struct State;
};
/// Define a default AY to be the sample source with a master divider of 4;
/// real AYs have a divide-by-8 step built in but YMs have only a divide-by-4,
/// Defines a default AY to be the sample source with a master divider of 4;
/// real AYs have a divide-by-8 step built in but YMs apply only a divide by 4.
///
/// The implementation of AY38910SampleSource combines those two worlds
/// by always applying a divide by four and scaling other things as appropriate.
template <bool stereo> struct AY38910:
public AY38910SampleSource<stereo>,
public Outputs::Speaker::SampleSource<AY38910<stereo>, stereo, 4> {