GB Audio: Refactor and improve audio emulation
Jeffrey Pfau jeffrey@endrift.com
Thu, 22 Dec 2016 00:12:47 -0800
3 files changed,
115 insertions(+),
106 deletions(-)
M
src/gb/audio.c
→
src/gb/audio.c
@@ -22,16 +22,22 @@ static const int CLOCKS_PER_BLIP_FRAME = 0x1000;
static const unsigned BLIP_BUFFER_SIZE = 0x4000; const int GB_AUDIO_VOLUME_MAX = 0x100; +static bool _writeSweep(struct GBAudioSweep* sweep, uint8_t value); static void _writeDuty(struct GBAudioEnvelope* envelope, uint8_t value); -static bool _writeSweep(struct GBAudioEnvelope* envelope, uint8_t value); -static int32_t _updateSquareChannel(struct GBAudioSquareControl* envelope, int duty); +static bool _writeEnvelope(struct GBAudioEnvelope* envelope, uint8_t value); + +static void _resetSweep(struct GBAudioSweep* sweep); +static bool _resetEnvelope(struct GBAudioEnvelope* sweep); + static void _updateEnvelope(struct GBAudioEnvelope* envelope); static void _updateEnvelopeDead(struct GBAudioEnvelope* envelope); -static bool _updateSweep(struct GBAudioChannel1* ch, bool initial); -static int32_t _updateChannel1(struct GBAudioChannel1* ch); -static int32_t _updateChannel2(struct GBAudioChannel2* ch); -static int32_t _updateChannel3(struct GBAudioChannel3* ch, enum GBAudioStyle style); -static int32_t _updateChannel4(struct GBAudioChannel4* ch); +static bool _updateSweep(struct GBAudioSquareChannel* sweep, bool initial); + +static void _updateSquareSample(struct GBAudioSquareChannel* ch); +static int32_t _updateSquareChannel(struct GBAudioSquareChannel* ch); +static int32_t _updateWaveChannel(struct GBAudioWaveChannel* ch, enum GBAudioStyle style); +static int32_t _updateNoiseChannel(struct GBAudioNoiseChannel* ch); + static void _sample(struct GBAudio* audio, int32_t cycles); static void _scheduleEvent(struct GBAudio* audio);@@ -64,10 +70,10 @@ audio->nextCh2 = 0;
audio->nextCh3 = 0; audio->fadeCh3 = 0; audio->nextCh4 = 0; - audio->ch1 = (struct GBAudioChannel1) { .envelope = { .dead = 2 } }; - audio->ch2 = (struct GBAudioChannel2) { .envelope = { .dead = 2 } }; - audio->ch3 = (struct GBAudioChannel3) { .bank = 0 }; - audio->ch4 = (struct GBAudioChannel4) { .envelope = { .dead = 2 } }; + audio->ch1 = (struct GBAudioSquareChannel) { .envelope = { .dead = 2 } }; + audio->ch2 = (struct GBAudioSquareChannel) { .envelope = { .dead = 2 } }; + audio->ch3 = (struct GBAudioWaveChannel) { .bank = 0 }; + audio->ch4 = (struct GBAudioNoiseChannel) { .envelope = { .dead = 2 } }; audio->eventDiff = 0; audio->nextFrame = 0; audio->frame = 0;@@ -102,18 +108,10 @@ mCoreSyncConsumeAudio(audio->p->sync);
} void GBAudioWriteNR10(struct GBAudio* audio, uint8_t value) { - audio->ch1.shift = GBAudioRegisterSquareSweepGetShift(value); - bool oldDirection = audio->ch1.direction; - audio->ch1.direction = GBAudioRegisterSquareSweepGetDirection(value); - if (audio->ch1.sweepOccurred && oldDirection && !audio->ch1.direction) { + if (!_writeSweep(&audio->ch1.sweep, value)) { audio->playingCh1 = false; *audio->nr52 &= ~0x0001; } - audio->ch1.sweepOccurred = false; - audio->ch1.time = GBAudioRegisterSquareSweepGetTime(value); - if (!audio->ch1.time) { - audio->ch1.time = 8; - } } void GBAudioWriteNR11(struct GBAudio* audio, uint8_t value) {@@ -122,7 +120,7 @@ audio->ch1.control.length = 64 - audio->ch1.envelope.length;
} void GBAudioWriteNR12(struct GBAudio* audio, uint8_t value) { - if (!_writeSweep(&audio->ch1.envelope, value)) { + if (!_writeEnvelope(&audio->ch1.envelope, value)) { audio->playingCh1 = false; *audio->nr52 &= ~0x0001; }@@ -145,23 +143,21 @@ audio->playingCh1 = false;
} } if (GBAudioRegisterControlIsRestart(value << 8)) { - audio->playingCh1 = audio->ch1.envelope.initialVolume || audio->ch1.envelope.direction; - audio->ch1.envelope.currentVolume = audio->ch1.envelope.initialVolume; + audio->playingCh1 = _resetEnvelope(&audio->ch1.envelope); _updateEnvelopeDead(&audio->ch1.envelope); if (audio->nextEvent == INT_MAX) { audio->eventDiff = 0; } if (audio->playingCh1) { - audio->ch1.control.hi = !audio->ch1.control.hi; + audio->ch1.control.hi = 0; + _updateSquareSample(&audio->ch1); } audio->nextCh1 = audio->eventDiff; - audio->ch1.realFrequency = audio->ch1.control.frequency; - audio->ch1.sweepStep = audio->ch1.time; - audio->ch1.sweepEnable = (audio->ch1.sweepStep != 8) || audio->ch1.shift; - audio->ch1.sweepOccurred = false; - if (audio->playingCh1 && audio->ch1.shift) { + audio->ch1.sweep.realFrequency = audio->ch1.control.frequency; + _resetSweep(&audio->ch1.sweep); + if (audio->playingCh1 && audio->ch1.sweep.shift) { audio->playingCh1 = _updateSweep(&audio->ch1, true); } if (!audio->ch1.control.length) {@@ -182,7 +178,7 @@ audio->ch2.control.length = 64 - audio->ch2.envelope.length;
} void GBAudioWriteNR22(struct GBAudio* audio, uint8_t value) { - if (!_writeSweep(&audio->ch2.envelope, value)) { + if (!_writeEnvelope(&audio->ch2.envelope, value)) { audio->playingCh2 = false; *audio->nr52 &= ~0x0002; }@@ -205,23 +201,24 @@ audio->playingCh2 = false;
} } if (GBAudioRegisterControlIsRestart(value << 8)) { - audio->playingCh2 = audio->ch2.envelope.initialVolume || audio->ch2.envelope.direction; - audio->ch2.envelope.currentVolume = audio->ch2.envelope.initialVolume; + audio->playingCh2 = _resetEnvelope(&audio->ch2.envelope); _updateEnvelopeDead(&audio->ch2.envelope); if (audio->nextEvent == INT_MAX) { audio->eventDiff = 0; } if (audio->playingCh2) { - audio->ch2.control.hi = !audio->ch2.control.hi; + audio->ch2.control.hi = 0; + _updateSquareSample(&audio->ch2); } - audio->nextCh2 = audio->eventDiff; + if (!audio->ch2.control.length) { audio->ch2.control.length = 64; if (audio->ch2.control.stop && !(audio->frame & 1)) { --audio->ch2.control.length; } } + audio->nextCh2 = audio->eventDiff; _scheduleEvent(audio); } *audio->nr52 &= ~0x0002;@@ -301,7 +298,7 @@ audio->ch4.length = 64 - audio->ch4.envelope.length;
} void GBAudioWriteNR42(struct GBAudio* audio, uint8_t value) { - if (!_writeSweep(&audio->ch4.envelope, value)) { + if (!_writeEnvelope(&audio->ch4.envelope, value)) { audio->playingCh4 = false; *audio->nr52 &= ~0x0008; }@@ -453,22 +450,21 @@ audio->nextCh1 -= audio->eventDiff;
if (!audio->ch1.envelope.dead && frame == 7) { --audio->ch1.envelope.nextStep; if (audio->ch1.envelope.nextStep == 0) { - int8_t sample = audio->ch1.control.hi * 0x10 - 0x8; _updateEnvelope(&audio->ch1.envelope); - audio->ch1.sample = sample * audio->ch1.envelope.currentVolume; + _updateSquareSample(&audio->ch1); } } - if (audio->ch1.sweepEnable && (frame & 3) == 2) { - --audio->ch1.sweepStep; - if (audio->ch1.sweepStep == 0) { + if (audio->ch1.sweep.enable && (frame & 3) == 2) { + --audio->ch1.sweep.step; + if (audio->ch1.sweep.step == 0) { audio->playingCh1 = _updateSweep(&audio->ch1, false); } } if (audio->ch1.envelope.dead != 2) { if (audio->nextCh1 <= 0) { - audio->nextCh1 += _updateChannel1(&audio->ch1); + audio->nextCh1 += _updateSquareChannel(&audio->ch1); } if (audio->nextCh1 < audio->nextEvent) { audio->nextEvent = audio->nextCh1;@@ -488,15 +484,14 @@ audio->nextCh2 -= audio->eventDiff;
if (!audio->ch2.envelope.dead && frame == 7) { --audio->ch2.envelope.nextStep; if (audio->ch2.envelope.nextStep == 0) { - int8_t sample = audio->ch2.control.hi * 0x10 - 0x8; _updateEnvelope(&audio->ch2.envelope); - audio->ch2.sample = sample * audio->ch2.envelope.currentVolume; + _updateSquareSample(&audio->ch2); } } if (audio->ch2.envelope.dead != 2) { if (audio->nextCh2 <= 0) { - audio->nextCh2 += _updateChannel2(&audio->ch2); + audio->nextCh2 += _updateSquareChannel(&audio->ch2); } if (audio->nextCh2 < audio->nextEvent) { audio->nextEvent = audio->nextCh2;@@ -522,7 +517,7 @@ if (audio->nextCh3 <= 0) {
if (audio->style == GB_AUDIO_DMG) { audio->fadeCh3 = audio->nextCh3 + 2; } - audio->nextCh3 += _updateChannel3(&audio->ch3, audio->style); + audio->nextCh3 += _updateWaveChannel(&audio->ch3, audio->style); audio->ch3.readable = true; } if (audio->fadeCh3 < audio->nextEvent) {@@ -588,7 +583,7 @@ int sampleRight = 0;
if (audio->ch4.envelope.dead != 2) { while (audio->nextCh4 <= 0) { - audio->nextCh4 += _updateChannel4(&audio->ch4); + audio->nextCh4 += _updateNoiseChannel(&audio->ch4); } if (audio->nextCh4 < audio->nextEvent) { audio->nextEvent = audio->nextCh4;@@ -672,12 +667,40 @@ audio->p->stream->postAudioBuffer(audio->p->stream, audio->left, audio->right);
} } +bool _resetEnvelope(struct GBAudioEnvelope* envelope) { + envelope->currentVolume = envelope->initialVolume; + _updateEnvelopeDead(envelope); + return envelope->initialVolume || envelope->direction; +} + +void _resetSweep(struct GBAudioSweep* sweep) { + sweep->step = sweep->time; + sweep->enable = (sweep->step != 8) || sweep->shift; + sweep->occurred = false; +} + +bool _writeSweep(struct GBAudioSweep* sweep, uint8_t value) { + sweep->shift = GBAudioRegisterSquareSweepGetShift(value); + bool oldDirection = sweep->direction; + sweep->direction = GBAudioRegisterSquareSweepGetDirection(value); + bool on = true; + if (sweep->occurred && oldDirection && !sweep->direction) { + on = false; + } + sweep->occurred = false; + sweep->time = GBAudioRegisterSquareSweepGetTime(value); + if (!sweep->time) { + sweep->time = 8; + } + return on; +} + void _writeDuty(struct GBAudioEnvelope* envelope, uint8_t value) { envelope->length = GBAudioRegisterDutyGetLength(value); envelope->duty = GBAudioRegisterDutyGetDuty(value); } -bool _writeSweep(struct GBAudioEnvelope* envelope, uint8_t value) { +bool _writeEnvelope(struct GBAudioEnvelope* envelope, uint8_t value) { envelope->stepTime = GBAudioRegisterSweepGetStepTime(value); envelope->direction = GBAudioRegisterSweepGetDirection(value); envelope->initialVolume = GBAudioRegisterSweepGetInitialVolume(value);@@ -686,18 +709,23 @@ envelope->nextStep = envelope->stepTime;
return envelope->initialVolume || envelope->direction; } -static int32_t _updateSquareChannel(struct GBAudioSquareControl* control, int duty) { - control->hi = !control->hi; - int period = 4 * (2048 - control->frequency); - switch (duty) { +static void _updateSquareSample(struct GBAudioSquareChannel* ch) { + ch->sample = (ch->control.hi * ch->envelope.currentVolume - 8) * 0x10; +} + +static int32_t _updateSquareChannel(struct GBAudioSquareChannel* ch) { + ch->control.hi = !ch->control.hi; + _updateSquareSample(ch); + int period = 4 * (2048 - ch->control.frequency); + switch (ch->envelope.duty) { case 0: - return control->hi ? period : period * 7; + return ch->control.hi ? period : period * 7; case 1: - return control->hi ? period * 2 : period * 6; + return ch->control.hi ? period * 2 : period * 6; case 2: return period * 4; case 3: - return control->hi ? period * 6 : period * 2; + return ch->control.hi ? period * 6 : period * 2; default: // This should never be hit return period * 4;@@ -722,9 +750,7 @@ }
} static void _updateEnvelopeDead(struct GBAudioEnvelope* envelope) { - if (envelope->stepTime == 0) { - envelope->dead = envelope->currentVolume ? 1 : 2; - } else if (!envelope->direction && !envelope->currentVolume) { + if (!envelope->direction && !envelope->currentVolume) { envelope->dead = 2; } else if (envelope->direction && envelope->currentVolume == 0xF) { envelope->dead = 1;@@ -733,21 +759,21 @@ envelope->dead = 0;
} } -static bool _updateSweep(struct GBAudioChannel1* ch, bool initial) { - if (initial || ch->time != 8) { - int frequency = ch->realFrequency; - if (ch->direction) { - frequency -= frequency >> ch->shift; +static bool _updateSweep(struct GBAudioSquareChannel* ch, bool initial) { + if (initial || ch->sweep.time != 8) { + int frequency = ch->sweep.realFrequency; + if (ch->sweep.direction) { + frequency -= frequency >> ch->sweep.shift; if (!initial && frequency >= 0) { ch->control.frequency = frequency; - ch->realFrequency = frequency; + ch->sweep.realFrequency = frequency; } } else { - frequency += frequency >> ch->shift; + frequency += frequency >> ch->sweep.shift; if (frequency < 2048) { - if (!initial && ch->shift) { + if (!initial && ch->sweep.shift) { ch->control.frequency = frequency; - ch->realFrequency = frequency; + ch->sweep.realFrequency = frequency; if (!_updateSweep(ch, true)) { return false; }@@ -756,27 +782,13 @@ } else {
return false; } } - ch->sweepOccurred = true; + ch->sweep.occurred = true; } - ch->sweepStep = ch->time; + ch->sweep.step = ch->sweep.time; return true; } -static int32_t _updateChannel1(struct GBAudioChannel1* ch) { - int timing = _updateSquareChannel(&ch->control, ch->envelope.duty); - ch->sample = ch->control.hi * 0x10 - 0x8; - ch->sample *= ch->envelope.currentVolume; - return timing; -} - -static int32_t _updateChannel2(struct GBAudioChannel2* ch) { - int timing = _updateSquareChannel(&ch->control, ch->envelope.duty); - ch->sample = ch->control.hi * 0x10 - 0x8; - ch->sample *= ch->envelope.currentVolume; - return timing; -} - -static int32_t _updateChannel3(struct GBAudioChannel3* ch, enum GBAudioStyle style) { +static int32_t _updateWaveChannel(struct GBAudioWaveChannel* ch, enum GBAudioStyle style) { int i; int volume; switch (ch->volume) {@@ -836,7 +848,7 @@ ch->sample *= volume * 4;
return 2 * (2048 - ch->rate); } -static int32_t _updateChannel4(struct GBAudioChannel4* ch) { +static int32_t _updateNoiseChannel(struct GBAudioNoiseChannel* ch) { int lsb = ch->lfsr & 1; ch->sample = lsb * 0x10 - 0x8; ch->sample *= ch->envelope.currentVolume;@@ -869,11 +881,11 @@
flags = GBSerializedAudioFlagsSetCh1Volume(flags, audio->ch1.envelope.currentVolume); flags = GBSerializedAudioFlagsSetCh1Dead(flags, audio->ch1.envelope.dead); flags = GBSerializedAudioFlagsSetCh1Hi(flags, audio->ch1.control.hi); - flags = GBSerializedAudioFlagsSetCh1SweepEnabled(flags, audio->ch1.sweepEnable); - flags = GBSerializedAudioFlagsSetCh1SweepOccurred(flags, audio->ch1.sweepOccurred); + flags = GBSerializedAudioFlagsSetCh1SweepEnabled(flags, audio->ch1.sweep.enable); + flags = GBSerializedAudioFlagsSetCh1SweepOccurred(flags, audio->ch1.sweep.occurred); ch1Flags = GBSerializedAudioEnvelopeSetLength(ch1Flags, audio->ch1.control.length); ch1Flags = GBSerializedAudioEnvelopeSetNextStep(ch1Flags, audio->ch1.envelope.nextStep); - ch1Flags = GBSerializedAudioEnvelopeSetFrequency(ch1Flags, audio->ch1.realFrequency); + ch1Flags = GBSerializedAudioEnvelopeSetFrequency(ch1Flags, audio->ch1.sweep.realFrequency); STORE_32LE(ch1Flags, 0, &state->ch1.envelope); STORE_32LE(audio->nextFrame, 0, &state->ch1.nextFrame); STORE_32LE(audio->nextCh1, 0, &state->ch1.nextEvent);@@ -919,11 +931,11 @@ LOAD_32LE(ch1Flags, 0, &state->ch1.envelope);
audio->ch1.envelope.currentVolume = GBSerializedAudioFlagsGetCh1Volume(flags); audio->ch1.envelope.dead = GBSerializedAudioFlagsGetCh1Dead(flags); audio->ch1.control.hi = GBSerializedAudioFlagsGetCh1Hi(flags); - audio->ch1.sweepEnable = GBSerializedAudioFlagsGetCh1SweepEnabled(flags); - audio->ch1.sweepOccurred = GBSerializedAudioFlagsGetCh1SweepOccurred(flags); + audio->ch1.sweep.enable = GBSerializedAudioFlagsGetCh1SweepEnabled(flags); + audio->ch1.sweep.occurred = GBSerializedAudioFlagsGetCh1SweepOccurred(flags); audio->ch1.control.length = GBSerializedAudioEnvelopeGetLength(ch1Flags); audio->ch1.envelope.nextStep = GBSerializedAudioEnvelopeGetNextStep(ch1Flags); - audio->ch1.realFrequency = GBSerializedAudioEnvelopeGetFrequency(ch1Flags); + audio->ch1.sweep.realFrequency = GBSerializedAudioEnvelopeGetFrequency(ch1Flags); LOAD_32LE(audio->nextFrame, 0, &state->ch1.nextFrame); LOAD_32LE(audio->nextCh1, 0, &state->ch1.nextEvent);@@ -966,4 +978,3 @@ LOAD_32LE(audio->nextEvent, 0, &state->audio.nextEvent);
LOAD_32LE(audio->eventDiff, 0, &state->audio.eventDiff); LOAD_32LE(audio->nextSample, 0, &state->audio.nextSample); } -
M
src/gb/audio.h
→
src/gb/audio.h
@@ -88,27 +88,24 @@ bool stop;
int hi; }; -struct GBAudioChannel1 { +struct GBAudioSweep { int shift; int time; - int sweepStep; + int step; bool direction; - bool sweepEnable; - bool sweepOccurred; + bool enable; + bool occurred; int realFrequency; - - struct GBAudioEnvelope envelope; - struct GBAudioSquareControl control; - int8_t sample; }; -struct GBAudioChannel2 { +struct GBAudioSquareChannel { + struct GBAudioSweep sweep; struct GBAudioEnvelope envelope; struct GBAudioSquareControl control; int8_t sample; }; -struct GBAudioChannel3 { +struct GBAudioWaveChannel { bool size; bool bank; bool enable;@@ -128,7 +125,7 @@ };
int8_t sample; }; -struct GBAudioChannel4 { +struct GBAudioNoiseChannel { struct GBAudioEnvelope envelope; int ratio;@@ -150,10 +147,10 @@ };
struct GBAudio { struct GB* p; - struct GBAudioChannel1 ch1; - struct GBAudioChannel2 ch2; - struct GBAudioChannel3 ch3; - struct GBAudioChannel4 ch4; + struct GBAudioSquareChannel ch1; + struct GBAudioSquareChannel ch2; + struct GBAudioWaveChannel ch3; + struct GBAudioNoiseChannel ch4; blip_t* left; blip_t* right;