grumpycoders/pcsx-redux
1
0
Fork 0
mirror of https://github.com/grumpycoders/pcsx-redux.git synced 2026-10-12 02:15:13 +00:00
Code Issues Packages Projects Releases Wiki Activity

Merge pull request #2265 from rixnobis/adsr-rate-cap

Browse Source 
spu: cap the ADSR rate at shift 26, and freeze all-ones rates
This commit is contained in:
Rix
2026-10-10 15:00:31 -07:00
committed by GitHub
parent ce2e4d5e8f 939ee03fac
commit 1277e9527d
1 changed files with 22 additions and 1 deletions
Download Patch File Download Diff File Expand all files Collapse all files
src/spu/adsr.cc
+22 -1
View File
@@ -37,8 +37,15 @@ namespace EnvelopeTables {
// steps: a phase counts samples in the fraction accumulator up to
// denominator[rate], then steps the level by numerator_increase[rate] (rising)
// or numerator_decrease[rate] (falling, negative).
// The hardware adds 0x8000 >> (shift - 11) to its step counter each sample and clamps
// that increment to at least 1, so every shift from 26 up steps once per 32768 samples
// (psx-spx: "a rate of 0x76 behaves like 0x6A").
constexpr int kMaxEffectiveShift = 26;
struct DenominatorGenerator {
static consteval int32_t calculateValue(std::size_t rate) { return (rate < 48) ? 1 : (1 << ((rate >> 2) - 11)); }
static consteval int32_t calculateValue(std::size_t rate) {
const int shift = static_cast<int>(rate >> 2);
return (rate < 48) ? 1 : (1 << (std::min(shift, kMaxEffectiveShift) - 11));
}
};
struct NumeratorIncreaseGenerator {
@@ -56,6 +63,10 @@ struct NumeratorDecreaseGenerator {
constexpr auto denominator = PCSX::generateTable<128, DenominatorGenerator>();
constexpr auto numerator_increase = PCSX::generateTable<128, NumeratorIncreaseGenerator>();
constexpr auto numerator_decrease = PCSX::generateTable<128, NumeratorDecreaseGenerator>();
static_assert(denominator.data[0x6a] == 32768);
static_assert(denominator.data[0x76] == denominator.data[0x6a]);
static_assert(denominator.data[0x7c] == 32768);
} // namespace EnvelopeTables
namespace {
@@ -71,6 +82,10 @@ constexpr int32_t kSustainLevelMask = 0xf; // ...compared against the 0..15
// (val & 0x7f00) >> 8, sustain is (val & 0x1fc0) >> 6), so the knee's rate-step lands past the
// end of the 128-entry tables on the slowest rates. Saturate instead of reading off the end.
constexpr int kMaxRateIndex = 127;
// A rate field of all ones (step and shift bits together) never steps. That is 0x7f for
// attack and sustain and 0x1f for release, tested on the register value before the knee.
constexpr int kFrozenRate = 0x7f;
constexpr int kFrozenCoarseRate = 0x1f;
} // namespace
// Write the freshly computed envelope state back and return the full 15-bit
@@ -93,6 +108,8 @@ int PCSX::SPU::AdsrEnvelope::Attack() {
int32_t envelopeVolFraction = m_adsrx.get<exEnvelopeVolF>().value;
const bool exponential = m_adsrx.get<exAttackModeExp>().value != 0;
if (rateIndex == kFrozenRate) return commit(envelopeVol, envelopeVolFraction);
// Past the knee the exponential attack curve flattens to a slower rate.
if (exponential && envelopeVol >= kExponentialKnee) {
rateIndex = std::min(rateIndex + kExponentialKneeRateStep, kMaxRateIndex);
@@ -139,6 +156,8 @@ int PCSX::SPU::AdsrEnvelope::Sustain() {
const bool exponential = m_adsrx.get<exSustainModeExp>().value != 0;
const bool increase = m_adsrx.get<exSustainIncrease>().value != 0;
if (rateIndex == kFrozenRate) return commit(envelopeVol, envelopeVolFraction);
if (increase) {
// Past the knee the exponential rise flattens to a slower rate.
if (exponential && envelopeVol >= kExponentialKnee) {
@@ -171,6 +190,8 @@ int PCSX::SPU::AdsrEnvelope::Release(bool &channelOn) {
int32_t envelopeVolFraction = m_adsrx.get<exEnvelopeVolF>().value;
const bool exponential = m_adsrx.get<exReleaseModeExp>().value != 0;
if (m_adsrx.get<exReleaseRate>().value == kFrozenCoarseRate) return commit(envelopeVol, envelopeVolFraction);
if (++envelopeVolFraction >= EnvelopeTables::denominator.data[rateIndex]) {
envelopeVolFraction = 0;
envelopeVol += exponential ? (EnvelopeTables::numerator_decrease.data[rateIndex] * envelopeVol) >>