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Fix period, table lookup.

This commit is contained in:
Thomas Harte 2024-04-16 22:12:10 -04:00
parent c3d4d0ee38
commit 06fd91f002
1 changed files with 11 additions and 4 deletions
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15
Machines/Acorn/Archimedes/Sound.hpp
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@ -28,9 +28,16 @@ static constexpr std::array<int16_t, 256> generate_levels() {
// Bit 7 provides a sign.
for(size_t c = 0; c < 256; c++) {
const bool is_negative = c & 128;
const auto point = static_cast<int>(c & 0xf);
const auto chord = static_cast<int>((c >> 4) & 7);
// This is the VIDC1 rule.
// const bool is_negative = c & 128;
// const auto point = static_cast<int>(c & 0xf);
// const auto chord = static_cast<int>((c >> 4) & 7);
// VIDC2 rule, which seems to be effective. I've yet to spot the rule by which
// VIDC1/2 is detected.
const bool is_negative = c & 1;
const auto point = static_cast<int>((c >> 1) & 0xf);
const auto chord = static_cast<int>((c >> 5) & 7);
const int start = (1 << chord) - 1;
const int end = (chord == 7) ? 247 : ((start << 1) + 1);
@ -106,7 +113,7 @@ struct Sound: private SoundLevels {
// Apply user-programmed clock divider.
--divider_;
if(!divider_) {
divider_ = reload_;
divider_ = reload_ + 2;
// Grab a single byte from the FIFO.
const uint8_t raw = ram_[static_cast<std::size_t>(current_.start) + static_cast<std::size_t>(byte_)];