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Merge pull request #721 from TomHarte/AYZero

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Ensures programmatic AY volume level 0 is completely off.
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Thomas Harte 2020-01-05 22:50:42 -05:00 committed by GitHub
commit cdb31b1c2b
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1 changed files with 12 additions and 1 deletions
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13
Components/AY38910/AY38910.cpp
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@ -77,6 +77,7 @@ void AY38910::set_sample_volume_range(std::int16_t range) {
for(int v = 0; v < 32; v++) {
volumes_[v] = int(max_volume / powf(root_two, float(v ^ 0x1f) / 2.0f));
}
volumes_[0] = 0; // Tie level 0 to silence.
evaluate_output_volume();
}
@ -161,10 +162,20 @@ void AY38910::evaluate_output_volume() {
};
#undef level
// This remapping table seeks to map 'channel volumes', i.e. the levels produced from the
// 16-step progammatic volumes set per channel to 'envelope volumes', i.e. the 32-step
// volumes that are produced by the envelope generators (on a YM at least). My reading of
// the data sheet is that '0' is still off, but 15 should be as loud as peak envelope. So
// I've thrown in the discontinuity at the low end, where it'll be very quiet.
const int channel_volumes[] = {
0, 3, 5, 7, 9, 11, 13, 15, 17, 19, 21, 23, 25, 27, 29, 31
};
static_assert(sizeof(channel_volumes) == 16*sizeof(int));
// Channel volume is a simple selection: if the bit at 0x10 is set, use the envelope volume; otherwise use the lower four bits,
// mapped to the range 1–31 in case this is a YM.
#define channel_volume(c) \
((output_registers_[c] >> 4)&1) * envelope_volume + (((output_registers_[c] >> 4)&1)^1) * (((output_registers_[c]&0xf) << 1) + 1)
((output_registers_[c] >> 4)&1) * envelope_volume + (((output_registers_[c] >> 4)&1)^1) * channel_volumes[output_registers_[c]&0xf]
const int volumes[3] = {
channel_volume(8),