all repos — mgba @ c662b59e9942bfffd69ed6754cc334de86f89e63

mGBA Game Boy Advance Emulator

src/gb/audio.c (view raw)

   1/* Copyright (c) 2013-2016 Jeffrey Pfau
   2 *
   3 * This Source Code Form is subject to the terms of the Mozilla Public
   4 * License, v. 2.0. If a copy of the MPL was not distributed with this
   5 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   6#include "audio.h"
   7
   8#include "core/interface.h"
   9#include "core/sync.h"
  10#include "gb/gb.h"
  11#include "gb/serialize.h"
  12#include "gb/io.h"
  13
  14#ifdef _3DS
  15#define blip_add_delta blip_add_delta_fast
  16#endif
  17
  18#define FRAME_CYCLES (DMG_LR35902_FREQUENCY >> 9)
  19
  20const uint32_t DMG_LR35902_FREQUENCY = 0x400000;
  21static const int CLOCKS_PER_BLIP_FRAME = 0x1000;
  22static const unsigned BLIP_BUFFER_SIZE = 0x4000;
  23const int GB_AUDIO_VOLUME_MAX = 0x100;
  24
  25static bool _writeSweep(struct GBAudioSweep* sweep, uint8_t value);
  26static void _writeDuty(struct GBAudioEnvelope* envelope, uint8_t value);
  27static bool _writeEnvelope(struct GBAudioEnvelope* envelope, uint8_t value);
  28
  29static void _resetSweep(struct GBAudioSweep* sweep);
  30static bool _resetEnvelope(struct GBAudioEnvelope* sweep);
  31
  32static void _updateEnvelope(struct GBAudioEnvelope* envelope);
  33static void _updateEnvelopeDead(struct GBAudioEnvelope* envelope);
  34static bool _updateSweep(struct GBAudioSquareChannel* sweep, bool initial);
  35
  36static void _updateSquareSample(struct GBAudioSquareChannel* ch);
  37static int32_t _updateSquareChannel(struct GBAudioSquareChannel* ch);
  38
  39static void _updateFrame(struct mTiming* timing, void* user, uint32_t cyclesLate);
  40static void _updateChannel1(struct mTiming* timing, void* user, uint32_t cyclesLate);
  41static void _updateChannel2(struct mTiming* timing, void* user, uint32_t cyclesLate);
  42static void _updateChannel3(struct mTiming* timing, void* user, uint32_t cyclesLate);
  43static void _fadeChannel3(struct mTiming* timing, void* user, uint32_t cyclesLate);
  44static void _updateChannel4(struct mTiming* timing, void* user, uint32_t cyclesLate);
  45static void _sample(struct mTiming* timing, void* user, uint32_t cyclesLate);
  46
  47void GBAudioInit(struct GBAudio* audio, size_t samples, uint8_t* nr52, enum GBAudioStyle style) {
  48	audio->samples = samples;
  49	audio->left = blip_new(BLIP_BUFFER_SIZE);
  50	audio->right = blip_new(BLIP_BUFFER_SIZE);
  51	audio->clockRate = DMG_LR35902_FREQUENCY;
  52	// Guess too large; we hang producing extra samples if we guess too low
  53	blip_set_rates(audio->left, DMG_LR35902_FREQUENCY, 96000);
  54	blip_set_rates(audio->right, DMG_LR35902_FREQUENCY, 96000);
  55	audio->forceDisableCh[0] = false;
  56	audio->forceDisableCh[1] = false;
  57	audio->forceDisableCh[2] = false;
  58	audio->forceDisableCh[3] = false;
  59	audio->masterVolume = GB_AUDIO_VOLUME_MAX;
  60	audio->nr52 = nr52;
  61	audio->style = style;
  62	if (style == GB_AUDIO_GBA) {
  63		audio->timingFactor = 4;
  64	} else {
  65		audio->timingFactor = 1;
  66	}
  67
  68	audio->frameEvent.context = audio;
  69	audio->frameEvent.name = "GB Audio Frame Sequencer";
  70	audio->frameEvent.callback = _updateFrame;
  71	audio->frameEvent.priority = 0x10;
  72	audio->ch1Event.context = audio;
  73	audio->ch1Event.name = "GB Audio Channel 1";
  74	audio->ch1Event.callback = _updateChannel1;
  75	audio->ch1Event.priority = 0x11;
  76	audio->ch2Event.context = audio;
  77	audio->ch2Event.name = "GB Audio Channel 2";
  78	audio->ch2Event.callback = _updateChannel2;
  79	audio->ch2Event.priority = 0x12;
  80	audio->ch3Event.context = audio;
  81	audio->ch3Event.name = "GB Audio Channel 3";
  82	audio->ch3Event.callback = _updateChannel3;
  83	audio->ch3Event.priority = 0x13;
  84	audio->ch3Fade.context = audio;
  85	audio->ch3Fade.name = "GB Audio Channel 3 Memory";
  86	audio->ch3Fade.callback = _fadeChannel3;
  87	audio->ch3Fade.priority = 0x14;
  88	audio->ch4Event.context = audio;
  89	audio->ch4Event.name = "GB Audio Channel 4";
  90	audio->ch4Event.callback = _updateChannel4;
  91	audio->ch4Event.priority = 0x15;
  92	audio->sampleEvent.context = audio;
  93	audio->sampleEvent.name = "GB Audio Sample";
  94	audio->sampleEvent.callback = _sample;
  95	audio->ch1Event.priority = 0x18;
  96}
  97
  98void GBAudioDeinit(struct GBAudio* audio) {
  99	blip_delete(audio->left);
 100	blip_delete(audio->right);
 101}
 102
 103void GBAudioReset(struct GBAudio* audio) {
 104	mTimingDeschedule(audio->timing, &audio->frameEvent);
 105	mTimingDeschedule(audio->timing, &audio->ch1Event);
 106	mTimingDeschedule(audio->timing, &audio->ch2Event);
 107	mTimingDeschedule(audio->timing, &audio->ch3Event);
 108	mTimingDeschedule(audio->timing, &audio->ch3Fade);
 109	mTimingDeschedule(audio->timing, &audio->ch4Event);
 110	mTimingDeschedule(audio->timing, &audio->sampleEvent);
 111	mTimingSchedule(audio->timing, &audio->frameEvent, 0);
 112	if (audio->style != GB_AUDIO_GBA) {
 113		mTimingSchedule(audio->timing, &audio->sampleEvent, 0);
 114	}
 115	audio->ch1 = (struct GBAudioSquareChannel) { .envelope = { .dead = 2 } };
 116	audio->ch2 = (struct GBAudioSquareChannel) { .envelope = { .dead = 2 } };
 117	audio->ch3 = (struct GBAudioWaveChannel) { .bank = 0 };
 118	// TODO: DMG randomness
 119	audio->ch3.wavedata8[0] = 0x00;
 120	audio->ch3.wavedata8[1] = 0xFF;
 121	audio->ch3.wavedata8[2] = 0x00;
 122	audio->ch3.wavedata8[3] = 0xFF;
 123	audio->ch3.wavedata8[4] = 0x00;
 124	audio->ch3.wavedata8[5] = 0xFF;
 125	audio->ch3.wavedata8[6] = 0x00;
 126	audio->ch3.wavedata8[7] = 0xFF;
 127	audio->ch3.wavedata8[8] = 0x00;
 128	audio->ch3.wavedata8[9] = 0xFF;
 129	audio->ch3.wavedata8[10] = 0x00;
 130	audio->ch3.wavedata8[11] = 0xFF;
 131	audio->ch3.wavedata8[12] = 0x00;
 132	audio->ch3.wavedata8[13] = 0xFF;
 133	audio->ch3.wavedata8[14] = 0x00;
 134	audio->ch3.wavedata8[15] = 0xFF;
 135	audio->ch4 = (struct GBAudioNoiseChannel) { .envelope = { .dead = 2 } };
 136	audio->frame = 0;
 137	audio->sampleInterval = 128;
 138	audio->lastLeft = 0;
 139	audio->lastRight = 0;
 140	audio->clock = 0;
 141	audio->volumeRight = 0;
 142	audio->volumeLeft = 0;
 143	audio->ch1Right = false;
 144	audio->ch2Right = false;
 145	audio->ch3Right = false;
 146	audio->ch4Right = false;
 147	audio->ch1Left = false;
 148	audio->ch2Left = false;
 149	audio->ch3Left = false;
 150	audio->ch4Left = false;
 151	audio->playingCh1 = false;
 152	audio->playingCh2 = false;
 153	audio->playingCh3 = false;
 154	audio->playingCh4 = false;
 155}
 156
 157void GBAudioResizeBuffer(struct GBAudio* audio, size_t samples) {
 158	mCoreSyncLockAudio(audio->p->sync);
 159	audio->samples = samples;
 160	blip_clear(audio->left);
 161	blip_clear(audio->right);
 162	audio->clock = 0;
 163	mCoreSyncConsumeAudio(audio->p->sync);
 164}
 165
 166void GBAudioWriteNR10(struct GBAudio* audio, uint8_t value) {
 167	if (!_writeSweep(&audio->ch1.sweep, value)) {
 168		mTimingDeschedule(audio->timing, &audio->ch1Event);
 169		audio->playingCh1 = false;
 170		*audio->nr52 &= ~0x0001;
 171	}
 172}
 173
 174void GBAudioWriteNR11(struct GBAudio* audio, uint8_t value) {
 175	_writeDuty(&audio->ch1.envelope, value);
 176	audio->ch1.control.length = 64 - audio->ch1.envelope.length;
 177}
 178
 179void GBAudioWriteNR12(struct GBAudio* audio, uint8_t value) {
 180	if (!_writeEnvelope(&audio->ch1.envelope, value)) {
 181		mTimingDeschedule(audio->timing, &audio->ch1Event);
 182		audio->playingCh1 = false;
 183		*audio->nr52 &= ~0x0001;
 184	}
 185}
 186
 187void GBAudioWriteNR13(struct GBAudio* audio, uint8_t value) {
 188	audio->ch1.control.frequency &= 0x700;
 189	audio->ch1.control.frequency |= GBAudioRegisterControlGetFrequency(value);
 190}
 191
 192void GBAudioWriteNR14(struct GBAudio* audio, uint8_t value) {
 193	audio->ch1.control.frequency &= 0xFF;
 194	audio->ch1.control.frequency |= GBAudioRegisterControlGetFrequency(value << 8);
 195	bool wasStop = audio->ch1.control.stop;
 196	audio->ch1.control.stop = GBAudioRegisterControlGetStop(value << 8);
 197	if (!wasStop && audio->ch1.control.stop && audio->ch1.control.length && !(audio->frame & 1)) {
 198		--audio->ch1.control.length;
 199		if (audio->ch1.control.length == 0) {
 200			mTimingDeschedule(audio->timing, &audio->ch1Event);
 201			audio->playingCh1 = false;
 202		}
 203	}
 204	if (GBAudioRegisterControlIsRestart(value << 8)) {
 205		audio->playingCh1 = _resetEnvelope(&audio->ch1.envelope);
 206
 207		if (audio->playingCh1) {
 208			audio->ch1.control.hi = 0;
 209			_updateSquareSample(&audio->ch1);
 210		}
 211
 212		audio->ch1.sweep.realFrequency = audio->ch1.control.frequency;
 213		_resetSweep(&audio->ch1.sweep);
 214		if (audio->playingCh1 && audio->ch1.sweep.shift) {
 215			audio->playingCh1 = _updateSweep(&audio->ch1, true);
 216		}
 217		if (!audio->ch1.control.length) {
 218			audio->ch1.control.length = 64;
 219			if (audio->ch1.control.stop && !(audio->frame & 1)) {
 220				--audio->ch1.control.length;
 221			}
 222		}
 223		mTimingDeschedule(audio->timing, &audio->ch1Event);
 224		if (audio->playingCh1 && audio->ch1.envelope.dead != 2) {
 225			mTimingSchedule(audio->timing, &audio->ch1Event, 0);
 226		}
 227	}
 228	*audio->nr52 &= ~0x0001;
 229	*audio->nr52 |= audio->playingCh1;
 230}
 231
 232void GBAudioWriteNR21(struct GBAudio* audio, uint8_t value) {
 233	_writeDuty(&audio->ch2.envelope, value);
 234	audio->ch2.control.length = 64 - audio->ch2.envelope.length;
 235}
 236
 237void GBAudioWriteNR22(struct GBAudio* audio, uint8_t value) {
 238	if (!_writeEnvelope(&audio->ch2.envelope, value)) {
 239		mTimingDeschedule(audio->timing, &audio->ch2Event);
 240		audio->playingCh2 = false;
 241		*audio->nr52 &= ~0x0002;
 242	}
 243}
 244
 245void GBAudioWriteNR23(struct GBAudio* audio, uint8_t value) {
 246	audio->ch2.control.frequency &= 0x700;
 247	audio->ch2.control.frequency |= GBAudioRegisterControlGetFrequency(value);
 248}
 249
 250void GBAudioWriteNR24(struct GBAudio* audio, uint8_t value) {
 251	audio->ch2.control.frequency &= 0xFF;
 252	audio->ch2.control.frequency |= GBAudioRegisterControlGetFrequency(value << 8);
 253	bool wasStop = audio->ch2.control.stop;
 254	audio->ch2.control.stop = GBAudioRegisterControlGetStop(value << 8);
 255	if (!wasStop && audio->ch2.control.stop && audio->ch2.control.length && !(audio->frame & 1)) {
 256		--audio->ch2.control.length;
 257		if (audio->ch2.control.length == 0) {
 258			mTimingDeschedule(audio->timing, &audio->ch2Event);
 259			audio->playingCh2 = false;
 260		}
 261	}
 262	if (GBAudioRegisterControlIsRestart(value << 8)) {
 263		audio->playingCh2 = _resetEnvelope(&audio->ch2.envelope);
 264
 265		if (audio->playingCh2) {
 266			audio->ch2.control.hi = 0;
 267			_updateSquareSample(&audio->ch2);
 268		}
 269
 270		if (!audio->ch2.control.length) {
 271			audio->ch2.control.length = 64;
 272			if (audio->ch2.control.stop && !(audio->frame & 1)) {
 273				--audio->ch2.control.length;
 274			}
 275		}
 276		mTimingDeschedule(audio->timing, &audio->ch2Event);
 277		if (audio->playingCh2 && audio->ch2.envelope.dead != 2) {
 278			mTimingSchedule(audio->timing, &audio->ch2Event, 0);
 279		}
 280	}
 281	*audio->nr52 &= ~0x0002;
 282	*audio->nr52 |= audio->playingCh2 << 1;
 283}
 284
 285void GBAudioWriteNR30(struct GBAudio* audio, uint8_t value) {
 286	audio->ch3.enable = GBAudioRegisterBankGetEnable(value);
 287	if (!audio->ch3.enable) {
 288		audio->playingCh3 = false;
 289		*audio->nr52 &= ~0x0004;
 290	}
 291}
 292
 293void GBAudioWriteNR31(struct GBAudio* audio, uint8_t value) {
 294	audio->ch3.length = 256 - value;
 295}
 296
 297void GBAudioWriteNR32(struct GBAudio* audio, uint8_t value) {
 298	audio->ch3.volume = GBAudioRegisterBankVolumeGetVolumeGB(value);
 299}
 300
 301void GBAudioWriteNR33(struct GBAudio* audio, uint8_t value) {
 302	audio->ch3.rate &= 0x700;
 303	audio->ch3.rate |= GBAudioRegisterControlGetRate(value);
 304}
 305
 306void GBAudioWriteNR34(struct GBAudio* audio, uint8_t value) {
 307	audio->ch3.rate &= 0xFF;
 308	audio->ch3.rate |= GBAudioRegisterControlGetRate(value << 8);
 309	bool wasStop = audio->ch3.stop;
 310	audio->ch3.stop = GBAudioRegisterControlGetStop(value << 8);
 311	if (!wasStop && audio->ch3.stop && audio->ch3.length && !(audio->frame & 1)) {
 312		--audio->ch3.length;
 313		if (audio->ch3.length == 0) {
 314			audio->playingCh3 = false;
 315		}
 316	}
 317	bool wasEnable = audio->playingCh3;
 318	if (GBAudioRegisterControlIsRestart(value << 8)) {
 319		audio->playingCh3 = audio->ch3.enable;
 320		if (!audio->ch3.length) {
 321			audio->ch3.length = 256;
 322			if (audio->ch3.stop && !(audio->frame & 1)) {
 323				--audio->ch3.length;
 324			}
 325		}
 326
 327		if (audio->style == GB_AUDIO_DMG && wasEnable && audio->playingCh3 && audio->ch3.readable) {
 328			if (audio->ch3.window < 8) {
 329				audio->ch3.wavedata8[0] = audio->ch3.wavedata8[audio->ch3.window >> 1];
 330			} else {
 331				audio->ch3.wavedata8[0] = audio->ch3.wavedata8[((audio->ch3.window >> 1) & ~3)];
 332				audio->ch3.wavedata8[1] = audio->ch3.wavedata8[((audio->ch3.window >> 1) & ~3) + 1];
 333				audio->ch3.wavedata8[2] = audio->ch3.wavedata8[((audio->ch3.window >> 1) & ~3) + 2];
 334				audio->ch3.wavedata8[3] = audio->ch3.wavedata8[((audio->ch3.window >> 1) & ~3) + 3];
 335			}
 336		}
 337		audio->ch3.window = 0;
 338	}
 339	mTimingDeschedule(audio->timing, &audio->ch3Event);
 340	if (audio->playingCh3) {
 341		audio->ch3.readable = audio->style != GB_AUDIO_DMG;
 342		// TODO: Where does this cycle delay come from?
 343		mTimingSchedule(audio->timing, &audio->ch3Event, audio->timingFactor * 4 + 2 * (2048 - audio->ch3.rate));
 344	}
 345	*audio->nr52 &= ~0x0004;
 346	*audio->nr52 |= audio->playingCh3 << 2;
 347}
 348
 349void GBAudioWriteNR41(struct GBAudio* audio, uint8_t value) {
 350	_writeDuty(&audio->ch4.envelope, value);
 351	audio->ch4.length = 64 - audio->ch4.envelope.length;
 352}
 353
 354void GBAudioWriteNR42(struct GBAudio* audio, uint8_t value) {
 355	if (!_writeEnvelope(&audio->ch4.envelope, value)) {
 356		mTimingDeschedule(audio->timing, &audio->ch4Event);
 357		audio->playingCh4 = false;
 358		*audio->nr52 &= ~0x0008;
 359	}
 360}
 361
 362void GBAudioWriteNR43(struct GBAudio* audio, uint8_t value) {
 363	audio->ch4.ratio = GBAudioRegisterNoiseFeedbackGetRatio(value);
 364	audio->ch4.frequency = GBAudioRegisterNoiseFeedbackGetFrequency(value);
 365	audio->ch4.power = GBAudioRegisterNoiseFeedbackGetPower(value);
 366}
 367
 368void GBAudioWriteNR44(struct GBAudio* audio, uint8_t value) {
 369	bool wasStop = audio->ch4.stop;
 370	audio->ch4.stop = GBAudioRegisterNoiseControlGetStop(value);
 371	if (!wasStop && audio->ch4.stop && audio->ch4.length && !(audio->frame & 1)) {
 372		--audio->ch4.length;
 373		if (audio->ch4.length == 0) {
 374			mTimingDeschedule(audio->timing, &audio->ch4Event);
 375			audio->playingCh4 = false;
 376		}
 377	}
 378	if (GBAudioRegisterNoiseControlIsRestart(value)) {
 379		audio->playingCh4 = _resetEnvelope(&audio->ch4.envelope);
 380
 381		if (audio->ch4.power) {
 382			audio->ch4.lfsr = 0x40;
 383		} else {
 384			audio->ch4.lfsr = 0x4000;
 385		}
 386		if (!audio->ch4.length) {
 387			audio->ch4.length = 64;
 388			if (audio->ch4.stop && !(audio->frame & 1)) {
 389				--audio->ch4.length;
 390			}
 391		}
 392		mTimingDeschedule(audio->timing, &audio->ch4Event);
 393		if (audio->playingCh4 && audio->ch4.envelope.dead != 2) {
 394			mTimingSchedule(audio->timing, &audio->ch4Event, 0);
 395		}
 396	}
 397	*audio->nr52 &= ~0x0008;
 398	*audio->nr52 |= audio->playingCh4 << 3;
 399}
 400
 401void GBAudioWriteNR50(struct GBAudio* audio, uint8_t value) {
 402	audio->volumeRight = GBRegisterNR50GetVolumeRight(value);
 403	audio->volumeLeft = GBRegisterNR50GetVolumeLeft(value);
 404}
 405
 406void GBAudioWriteNR51(struct GBAudio* audio, uint8_t value) {
 407	audio->ch1Right = GBRegisterNR51GetCh1Right(value);
 408	audio->ch2Right = GBRegisterNR51GetCh2Right(value);
 409	audio->ch3Right = GBRegisterNR51GetCh3Right(value);
 410	audio->ch4Right = GBRegisterNR51GetCh4Right(value);
 411	audio->ch1Left = GBRegisterNR51GetCh1Left(value);
 412	audio->ch2Left = GBRegisterNR51GetCh2Left(value);
 413	audio->ch3Left = GBRegisterNR51GetCh3Left(value);
 414	audio->ch4Left = GBRegisterNR51GetCh4Left(value);
 415}
 416
 417void GBAudioWriteNR52(struct GBAudio* audio, uint8_t value) {
 418	bool wasEnable = audio->enable;
 419	audio->enable = GBAudioEnableGetEnable(value);
 420	if (!audio->enable) {
 421		audio->playingCh1 = 0;
 422		audio->playingCh2 = 0;
 423		audio->playingCh3 = 0;
 424		audio->playingCh4 = 0;
 425		GBAudioWriteNR10(audio, 0);
 426		GBAudioWriteNR12(audio, 0);
 427		GBAudioWriteNR13(audio, 0);
 428		GBAudioWriteNR14(audio, 0);
 429		GBAudioWriteNR22(audio, 0);
 430		GBAudioWriteNR23(audio, 0);
 431		GBAudioWriteNR24(audio, 0);
 432		GBAudioWriteNR30(audio, 0);
 433		GBAudioWriteNR32(audio, 0);
 434		GBAudioWriteNR33(audio, 0);
 435		GBAudioWriteNR34(audio, 0);
 436		GBAudioWriteNR42(audio, 0);
 437		GBAudioWriteNR43(audio, 0);
 438		GBAudioWriteNR44(audio, 0);
 439		GBAudioWriteNR50(audio, 0);
 440		GBAudioWriteNR51(audio, 0);
 441		if (audio->style != GB_AUDIO_DMG) {
 442			GBAudioWriteNR11(audio, 0);
 443			GBAudioWriteNR21(audio, 0);
 444			GBAudioWriteNR31(audio, 0);
 445			GBAudioWriteNR41(audio, 0);
 446		}
 447
 448		if (audio->p) {
 449			audio->p->memory.io[REG_NR10] = 0;
 450			audio->p->memory.io[REG_NR11] = 0;
 451			audio->p->memory.io[REG_NR12] = 0;
 452			audio->p->memory.io[REG_NR13] = 0;
 453			audio->p->memory.io[REG_NR14] = 0;
 454			audio->p->memory.io[REG_NR21] = 0;
 455			audio->p->memory.io[REG_NR22] = 0;
 456			audio->p->memory.io[REG_NR23] = 0;
 457			audio->p->memory.io[REG_NR24] = 0;
 458			audio->p->memory.io[REG_NR30] = 0;
 459			audio->p->memory.io[REG_NR31] = 0;
 460			audio->p->memory.io[REG_NR32] = 0;
 461			audio->p->memory.io[REG_NR33] = 0;
 462			audio->p->memory.io[REG_NR34] = 0;
 463			audio->p->memory.io[REG_NR42] = 0;
 464			audio->p->memory.io[REG_NR43] = 0;
 465			audio->p->memory.io[REG_NR44] = 0;
 466			audio->p->memory.io[REG_NR50] = 0;
 467			audio->p->memory.io[REG_NR51] = 0;
 468			if (audio->style != GB_AUDIO_DMG) {
 469				audio->p->memory.io[REG_NR11] = 0;
 470				audio->p->memory.io[REG_NR21] = 0;
 471				audio->p->memory.io[REG_NR31] = 0;
 472				audio->p->memory.io[REG_NR41] = 0;
 473			}
 474		}
 475		*audio->nr52 &= ~0x000F;
 476	} else if (!wasEnable) {
 477		audio->frame = 7;
 478	}
 479}
 480
 481void _updateFrame(struct mTiming* timing, void* user, uint32_t cyclesLate) {
 482	struct GBAudio* audio = user;
 483
 484	int frame = (audio->frame + 1) & 7;
 485	audio->frame = frame;
 486
 487	switch (frame) {
 488	case 2:
 489	case 6:
 490		if (audio->ch1.sweep.enable) {
 491			--audio->ch1.sweep.step;
 492			if (audio->ch1.sweep.step == 0) {
 493				audio->playingCh1 = _updateSweep(&audio->ch1, false);
 494				*audio->nr52 &= ~0x0001;
 495				*audio->nr52 |= audio->playingCh1;
 496			}
 497		}
 498		// Fall through
 499	case 0:
 500	case 4:
 501		if (audio->ch1.control.length && audio->ch1.control.stop) {
 502			--audio->ch1.control.length;
 503			if (audio->ch1.control.length == 0) {
 504				mTimingDeschedule(timing, &audio->ch1Event);
 505				audio->playingCh1 = 0;
 506				*audio->nr52 &= ~0x0001;
 507			}
 508		}
 509
 510		if (audio->ch2.control.length && audio->ch2.control.stop) {
 511			--audio->ch2.control.length;
 512			if (audio->ch2.control.length == 0) {
 513				mTimingDeschedule(timing, &audio->ch2Event);
 514				audio->playingCh2 = 0;
 515				*audio->nr52 &= ~0x0002;
 516			}
 517		}
 518
 519		if (audio->ch3.length && audio->ch3.stop) {
 520			--audio->ch3.length;
 521			if (audio->ch3.length == 0) {
 522				mTimingDeschedule(timing, &audio->ch3Event);
 523				audio->playingCh3 = 0;
 524				*audio->nr52 &= ~0x0004;
 525			}
 526		}
 527
 528		if (audio->ch4.length && audio->ch4.stop) {
 529			--audio->ch4.length;
 530			if (audio->ch4.length == 0) {
 531				mTimingDeschedule(timing, &audio->ch4Event);
 532				audio->playingCh4 = 0;
 533				*audio->nr52 &= ~0x0008;
 534			}
 535		}
 536		break;
 537	case 7:
 538		if (audio->playingCh1 && !audio->ch1.envelope.dead) {
 539			--audio->ch1.envelope.nextStep;
 540			if (audio->ch1.envelope.nextStep == 0) {
 541				_updateEnvelope(&audio->ch1.envelope);
 542				if (audio->ch1.envelope.dead == 2) {
 543					mTimingDeschedule(timing, &audio->ch1Event);
 544				}
 545				_updateSquareSample(&audio->ch1);
 546			}
 547		}
 548
 549		if (audio->playingCh2 && !audio->ch2.envelope.dead) {
 550			--audio->ch2.envelope.nextStep;
 551			if (audio->ch2.envelope.nextStep == 0) {
 552				_updateEnvelope(&audio->ch2.envelope);
 553				if (audio->ch2.envelope.dead == 2) {
 554					mTimingDeschedule(timing, &audio->ch2Event);
 555				}
 556				_updateSquareSample(&audio->ch1);
 557			}
 558		}
 559
 560		if (audio->playingCh4 && !audio->ch4.envelope.dead) {
 561			--audio->ch4.envelope.nextStep;
 562			if (audio->ch4.envelope.nextStep == 0) {
 563				int8_t sample = (audio->ch4.sample >> 7) * 0x8;
 564				_updateEnvelope(&audio->ch4.envelope);
 565				if (audio->ch4.envelope.dead == 2) {
 566					mTimingDeschedule(timing, &audio->ch4Event);
 567				}
 568				audio->ch4.sample = sample * audio->ch4.envelope.currentVolume;
 569			}
 570		}
 571		break;
 572	}
 573
 574	mTimingSchedule(timing, &audio->frameEvent, audio->timingFactor * FRAME_CYCLES - cyclesLate);
 575}
 576
 577void GBAudioSamplePSG(struct GBAudio* audio, int16_t* left, int16_t* right) {
 578	int sampleLeft = 0;
 579	int sampleRight = 0;
 580
 581	if (audio->playingCh1 && !audio->forceDisableCh[0]) {
 582		if (audio->ch1Left) {
 583			sampleLeft += audio->ch1.sample;
 584		}
 585
 586		if (audio->ch1Right) {
 587			sampleRight += audio->ch1.sample;
 588		}
 589	}
 590
 591	if (audio->playingCh2 && !audio->forceDisableCh[1]) {
 592		if (audio->ch2Left) {
 593			sampleLeft += audio->ch2.sample;
 594		}
 595
 596		if (audio->ch2Right) {
 597			sampleRight += audio->ch2.sample;
 598		}
 599	}
 600
 601	if (audio->playingCh3 && !audio->forceDisableCh[2]) {
 602		if (audio->ch3Left) {
 603			sampleLeft += audio->ch3.sample;
 604		}
 605
 606		if (audio->ch3Right) {
 607			sampleRight += audio->ch3.sample;
 608		}
 609	}
 610
 611	if (audio->playingCh4 && !audio->forceDisableCh[3]) {
 612		if (audio->ch4Left) {
 613			sampleLeft += audio->ch4.sample;
 614		}
 615
 616		if (audio->ch4Right) {
 617			sampleRight += audio->ch4.sample;
 618		}
 619	}
 620
 621	*left = sampleLeft * (1 + audio->volumeLeft);
 622	*right = sampleRight * (1 + audio->volumeRight);
 623}
 624
 625static void _sample(struct mTiming* timing, void* user, uint32_t cyclesLate) {
 626	struct GBAudio* audio = user;
 627	int16_t sampleLeft = 0;
 628	int16_t sampleRight = 0;
 629	GBAudioSamplePSG(audio, &sampleLeft, &sampleRight);
 630	sampleLeft = (sampleLeft * audio->masterVolume) >> 6;
 631	sampleRight = (sampleRight * audio->masterVolume) >> 6;
 632
 633	mCoreSyncLockAudio(audio->p->sync);
 634	unsigned produced;
 635	if ((size_t) blip_samples_avail(audio->left) < audio->samples) {
 636		blip_add_delta(audio->left, audio->clock, sampleLeft - audio->lastLeft);
 637		blip_add_delta(audio->right, audio->clock, sampleRight - audio->lastRight);
 638		audio->lastLeft = sampleLeft;
 639		audio->lastRight = sampleRight;
 640		audio->clock += audio->sampleInterval;
 641		if (audio->clock >= CLOCKS_PER_BLIP_FRAME) {
 642			blip_end_frame(audio->left, audio->clock);
 643			blip_end_frame(audio->right, audio->clock);
 644			audio->clock -= CLOCKS_PER_BLIP_FRAME;
 645		}
 646	}
 647	produced = blip_samples_avail(audio->left);
 648	if (audio->p->stream && audio->p->stream->postAudioFrame) {
 649		audio->p->stream->postAudioFrame(audio->p->stream, sampleLeft, sampleRight);
 650	}
 651	bool wait = produced >= audio->samples;
 652	mCoreSyncProduceAudio(audio->p->sync, wait);
 653
 654	if (wait && audio->p->stream && audio->p->stream->postAudioBuffer) {
 655		audio->p->stream->postAudioBuffer(audio->p->stream, audio->left, audio->right);
 656	}
 657	mTimingSchedule(timing, &audio->sampleEvent, audio->sampleInterval * audio->timingFactor - cyclesLate);
 658}
 659
 660bool _resetEnvelope(struct GBAudioEnvelope* envelope) {
 661	envelope->currentVolume = envelope->initialVolume;
 662	_updateEnvelopeDead(envelope);
 663	if (!envelope->dead) {
 664		envelope->nextStep = envelope->stepTime;
 665	}
 666	return envelope->initialVolume || envelope->direction;
 667}
 668
 669void _resetSweep(struct GBAudioSweep* sweep) {
 670	sweep->step = sweep->time;
 671	sweep->enable = (sweep->step != 8) || sweep->shift;
 672	sweep->occurred = false;
 673}
 674
 675bool _writeSweep(struct GBAudioSweep* sweep, uint8_t value) {
 676	sweep->shift = GBAudioRegisterSquareSweepGetShift(value);
 677	bool oldDirection = sweep->direction;
 678	sweep->direction = GBAudioRegisterSquareSweepGetDirection(value);
 679	bool on = true;
 680	if (sweep->occurred && oldDirection && !sweep->direction) {
 681		on = false;
 682	}
 683	sweep->occurred = false;
 684	sweep->time = GBAudioRegisterSquareSweepGetTime(value);
 685	if (!sweep->time) {
 686		sweep->time = 8;
 687	}
 688	return on;
 689}
 690
 691void _writeDuty(struct GBAudioEnvelope* envelope, uint8_t value) {
 692	envelope->length = GBAudioRegisterDutyGetLength(value);
 693	envelope->duty = GBAudioRegisterDutyGetDuty(value);
 694}
 695
 696bool _writeEnvelope(struct GBAudioEnvelope* envelope, uint8_t value) {
 697	envelope->stepTime = GBAudioRegisterSweepGetStepTime(value);
 698	envelope->direction = GBAudioRegisterSweepGetDirection(value);
 699	envelope->initialVolume = GBAudioRegisterSweepGetInitialVolume(value);
 700	_updateEnvelopeDead(envelope);
 701	envelope->nextStep = envelope->stepTime;
 702	return (envelope->initialVolume || envelope->direction) && envelope->dead != 2;
 703}
 704
 705static void _updateSquareSample(struct GBAudioSquareChannel* ch) {
 706	ch->sample = (ch->control.hi * ch->envelope.currentVolume - 8) * 0x10;
 707}
 708
 709static int32_t _updateSquareChannel(struct GBAudioSquareChannel* ch) {
 710	ch->control.hi = !ch->control.hi;
 711	_updateSquareSample(ch);
 712	int period = 4 * (2048 - ch->control.frequency);
 713	switch (ch->envelope.duty) {
 714	case 0:
 715		return ch->control.hi ? period : period * 7;
 716	case 1:
 717		return ch->control.hi ? period * 2 : period * 6;
 718	case 2:
 719		return period * 4;
 720	case 3:
 721		return ch->control.hi ? period * 6 : period * 2;
 722	default:
 723		// This should never be hit
 724		return period * 4;
 725	}
 726}
 727
 728static void _updateEnvelope(struct GBAudioEnvelope* envelope) {
 729	if (envelope->direction) {
 730		++envelope->currentVolume;
 731	} else {
 732		--envelope->currentVolume;
 733	}
 734	if (envelope->currentVolume >= 15) {
 735		envelope->currentVolume = 15;
 736		envelope->dead = 1;
 737	} else if (envelope->currentVolume <= 0) {
 738		envelope->currentVolume = 0;
 739		envelope->dead = 2;
 740	} else {
 741		envelope->nextStep = envelope->stepTime;
 742	}
 743}
 744
 745static void _updateEnvelopeDead(struct GBAudioEnvelope* envelope) {
 746	if (!envelope->stepTime) {
 747		envelope->dead = envelope->currentVolume ? 1 : 2;
 748	} else if (!envelope->direction && !envelope->currentVolume) {
 749		envelope->dead = 2;
 750	} else if (envelope->direction && envelope->currentVolume == 0xF) {
 751		envelope->dead = 1;
 752	} else {
 753		envelope->dead = 0;
 754	}
 755}
 756
 757static bool _updateSweep(struct GBAudioSquareChannel* ch, bool initial) {
 758	if (initial || ch->sweep.time != 8) {
 759		int frequency = ch->sweep.realFrequency;
 760		if (ch->sweep.direction) {
 761			frequency -= frequency >> ch->sweep.shift;
 762			if (!initial && frequency >= 0) {
 763				ch->control.frequency = frequency;
 764				ch->sweep.realFrequency = frequency;
 765			}
 766		} else {
 767			frequency += frequency >> ch->sweep.shift;
 768			if (frequency < 2048) {
 769				if (!initial && ch->sweep.shift) {
 770					ch->control.frequency = frequency;
 771					ch->sweep.realFrequency = frequency;
 772					if (!_updateSweep(ch, true)) {
 773						return false;
 774					}
 775				}
 776			} else {
 777				return false;
 778			}
 779		}
 780		ch->sweep.occurred = true;
 781	}
 782	ch->sweep.step = ch->sweep.time;
 783	return true;
 784}
 785
 786static void _updateChannel1(struct mTiming* timing, void* user, uint32_t cyclesLate) {
 787	struct GBAudio* audio = user;
 788	struct GBAudioSquareChannel* ch = &audio->ch1;
 789	int cycles = _updateSquareChannel(ch);
 790	mTimingSchedule(timing, &audio->ch1Event, audio->timingFactor * cycles - cyclesLate);
 791}
 792
 793static void _updateChannel2(struct mTiming* timing, void* user, uint32_t cyclesLate) {
 794	struct GBAudio* audio = user;
 795	struct GBAudioSquareChannel* ch = &audio->ch2;
 796	int cycles = _updateSquareChannel(ch);
 797	mTimingSchedule(timing, &audio->ch2Event, audio->timingFactor * cycles - cyclesLate);
 798}
 799
 800static void _updateChannel3(struct mTiming* timing, void* user, uint32_t cyclesLate) {
 801	struct GBAudio* audio = user;
 802	struct GBAudioWaveChannel* ch = &audio->ch3;
 803	int i;
 804	int volume;
 805	switch (ch->volume) {
 806	case 0:
 807		volume = 0;
 808		break;
 809	case 1:
 810		volume = 4;
 811		break;
 812	case 2:
 813		volume = 2;
 814		break;
 815	case 3:
 816		volume = 1;
 817		break;
 818	default:
 819		volume = 3;
 820		break;
 821	}
 822	int start;
 823	int end;
 824	switch (audio->style) {
 825	case GB_AUDIO_DMG:
 826	default:
 827		++ch->window;
 828		ch->window &= 0x1F;
 829		ch->sample = ch->wavedata8[ch->window >> 1];
 830		if (!(ch->window & 1)) {
 831			ch->sample >>= 4;
 832		}
 833		ch->sample &= 0xF;
 834		break;
 835	case GB_AUDIO_GBA:
 836		if (ch->size) {
 837			start = 7;
 838			end = 0;
 839		} else if (ch->bank) {
 840			start = 7;
 841			end = 4;
 842		} else {
 843			start = 3;
 844			end = 0;
 845		}
 846		uint32_t bitsCarry = ch->wavedata32[end] & 0x000000F0;
 847		uint32_t bits;
 848		for (i = start; i >= end; --i) {
 849			bits = ch->wavedata32[i] & 0x000000F0;
 850			ch->wavedata32[i] = ((ch->wavedata32[i] & 0x0F0F0F0F) << 4) | ((ch->wavedata32[i] & 0xF0F0F000) >> 12);
 851			ch->wavedata32[i] |= bitsCarry << 20;
 852			bitsCarry = bits;
 853		}
 854		ch->sample = bitsCarry >> 4;
 855		break;
 856	}
 857	ch->sample -= 8;
 858	ch->sample *= volume * 4;
 859	audio->ch3.readable = true;
 860	if (audio->style == GB_AUDIO_DMG) {
 861		mTimingSchedule(timing, &audio->ch3Fade, 2 - cyclesLate);
 862	}
 863	int cycles = 2 * (2048 - ch->rate);
 864	mTimingSchedule(timing, &audio->ch3Event, audio->timingFactor * cycles - cyclesLate);
 865}
 866static void _fadeChannel3(struct mTiming* timing, void* user, uint32_t cyclesLate) {
 867	UNUSED(timing);
 868	UNUSED(cyclesLate);
 869	struct GBAudio* audio = user;
 870	audio->ch3.readable = false;
 871}
 872
 873static void _updateChannel4(struct mTiming* timing, void* user, uint32_t cyclesLate) {
 874	struct GBAudio* audio = user;
 875	struct GBAudioNoiseChannel* ch = &audio->ch4;
 876
 877	int32_t baseCycles = ch->ratio ? 2 * ch->ratio : 1;
 878	baseCycles <<= ch->frequency;
 879	baseCycles *= 8 * audio->timingFactor;
 880	int32_t cycles = 0;
 881
 882	do {
 883		int lsb = ch->lfsr & 1;
 884		ch->sample = lsb * 0x10 - 0x8;
 885		ch->sample *= ch->envelope.currentVolume;
 886		ch->lfsr >>= 1;
 887		ch->lfsr ^= (lsb * 0x60) << (ch->power ? 0 : 8);
 888		cycles += baseCycles;
 889	} while (cycles < audio->sampleInterval);
 890	mTimingSchedule(timing, &audio->ch4Event, cycles - cyclesLate);
 891}
 892
 893void GBAudioPSGSerialize(const struct GBAudio* audio, struct GBSerializedPSGState* state, uint32_t* flagsOut) {
 894	uint32_t flags = 0;
 895	uint32_t ch1Flags = 0;
 896	uint32_t ch2Flags = 0;
 897	uint32_t ch4Flags = 0;
 898
 899	flags = GBSerializedAudioFlagsSetFrame(flags, audio->frame);
 900	STORE_32LE(audio->frameEvent.when - mTimingCurrentTime(audio->timing), 0, &state->ch1.nextFrame);
 901
 902	flags = GBSerializedAudioFlagsSetCh1Volume(flags, audio->ch1.envelope.currentVolume);
 903	flags = GBSerializedAudioFlagsSetCh1Dead(flags, audio->ch1.envelope.dead);
 904	flags = GBSerializedAudioFlagsSetCh1Hi(flags, audio->ch1.control.hi);
 905	flags = GBSerializedAudioFlagsSetCh1SweepEnabled(flags, audio->ch1.sweep.enable);
 906	flags = GBSerializedAudioFlagsSetCh1SweepOccurred(flags, audio->ch1.sweep.occurred);
 907	ch1Flags = GBSerializedAudioEnvelopeSetLength(ch1Flags, audio->ch1.control.length);
 908	ch1Flags = GBSerializedAudioEnvelopeSetNextStep(ch1Flags, audio->ch1.envelope.nextStep);
 909	ch1Flags = GBSerializedAudioEnvelopeSetFrequency(ch1Flags, audio->ch1.sweep.realFrequency);
 910	STORE_32LE(ch1Flags, 0, &state->ch1.envelope);
 911	STORE_32LE(audio->ch1Event.when - mTimingCurrentTime(audio->timing), 0, &state->ch1.nextEvent);
 912
 913	flags = GBSerializedAudioFlagsSetCh2Volume(flags, audio->ch2.envelope.currentVolume);
 914	flags = GBSerializedAudioFlagsSetCh2Dead(flags, audio->ch2.envelope.dead);
 915	flags = GBSerializedAudioFlagsSetCh2Hi(flags, audio->ch2.control.hi);
 916	ch2Flags = GBSerializedAudioEnvelopeSetLength(ch2Flags, audio->ch2.control.length);
 917	ch2Flags = GBSerializedAudioEnvelopeSetNextStep(ch2Flags, audio->ch2.envelope.nextStep);
 918	STORE_32LE(ch2Flags, 0, &state->ch2.envelope);
 919	STORE_32LE(audio->ch2Event.when - mTimingCurrentTime(audio->timing), 0, &state->ch2.nextEvent);
 920
 921	flags = GBSerializedAudioFlagsSetCh3Readable(flags, audio->ch3.readable);
 922	memcpy(state->ch3.wavebanks, audio->ch3.wavedata32, sizeof(state->ch3.wavebanks));
 923	STORE_16LE(audio->ch3.length, 0, &state->ch3.length);
 924	STORE_32LE(audio->ch3Event.when - mTimingCurrentTime(audio->timing), 0, &state->ch3.nextEvent);
 925	STORE_32LE(audio->ch3Fade.when - mTimingCurrentTime(audio->timing), 0, &state->ch1.nextCh3Fade);
 926
 927	flags = GBSerializedAudioFlagsSetCh4Volume(flags, audio->ch4.envelope.currentVolume);
 928	flags = GBSerializedAudioFlagsSetCh4Dead(flags, audio->ch4.envelope.dead);
 929	STORE_32LE(audio->ch4.lfsr, 0, &state->ch4.lfsr);
 930	ch4Flags = GBSerializedAudioEnvelopeSetLength(ch4Flags, audio->ch4.length);
 931	ch4Flags = GBSerializedAudioEnvelopeSetNextStep(ch4Flags, audio->ch4.envelope.nextStep);
 932	STORE_32LE(ch4Flags, 0, &state->ch4.envelope);
 933	STORE_32LE(audio->ch4Event.when - mTimingCurrentTime(audio->timing), 0, &state->ch4.nextEvent);
 934
 935	STORE_32LE(flags, 0, flagsOut);
 936}
 937
 938void GBAudioPSGDeserialize(struct GBAudio* audio, const struct GBSerializedPSGState* state, const uint32_t* flagsIn) {
 939	uint32_t flags;
 940	uint32_t ch1Flags = 0;
 941	uint32_t ch2Flags = 0;
 942	uint32_t ch4Flags = 0;
 943	uint32_t when;
 944
 945	audio->playingCh1 = !!(*audio->nr52 & 0x0001);
 946	audio->playingCh2 = !!(*audio->nr52 & 0x0002);
 947	audio->playingCh3 = !!(*audio->nr52 & 0x0004);
 948	audio->playingCh4 = !!(*audio->nr52 & 0x0008);
 949	audio->enable = GBAudioEnableGetEnable(*audio->nr52);
 950
 951	LOAD_32LE(flags, 0, flagsIn);
 952	LOAD_32LE(ch1Flags, 0, &state->ch1.envelope);
 953	audio->ch1.envelope.currentVolume = GBSerializedAudioFlagsGetCh1Volume(flags);
 954	audio->ch1.envelope.dead = GBSerializedAudioFlagsGetCh1Dead(flags);
 955	audio->ch1.control.hi = GBSerializedAudioFlagsGetCh1Hi(flags);
 956	audio->ch1.sweep.enable = GBSerializedAudioFlagsGetCh1SweepEnabled(flags);
 957	audio->ch1.sweep.occurred = GBSerializedAudioFlagsGetCh1SweepOccurred(flags);
 958	audio->ch1.control.length = GBSerializedAudioEnvelopeGetLength(ch1Flags);
 959	audio->ch1.envelope.nextStep = GBSerializedAudioEnvelopeGetNextStep(ch1Flags);
 960	audio->ch1.sweep.realFrequency = GBSerializedAudioEnvelopeGetFrequency(ch1Flags);
 961	LOAD_32LE(when, 0, &state->ch1.nextEvent);
 962	mTimingDeschedule(audio->timing, &audio->ch1Event);
 963	if (audio->ch1.envelope.dead < 2 && audio->playingCh1) {
 964		mTimingSchedule(audio->timing, &audio->ch1Event, when);
 965	}
 966
 967	LOAD_32LE(ch2Flags, 0, &state->ch2.envelope);
 968	audio->ch2.envelope.currentVolume = GBSerializedAudioFlagsGetCh2Volume(flags);
 969	audio->ch2.envelope.dead = GBSerializedAudioFlagsGetCh2Dead(flags);
 970	audio->ch2.control.hi = GBSerializedAudioFlagsGetCh2Hi(flags);
 971	audio->ch2.control.length = GBSerializedAudioEnvelopeGetLength(ch2Flags);
 972	audio->ch2.envelope.nextStep = GBSerializedAudioEnvelopeGetNextStep(ch2Flags);
 973	LOAD_32LE(when, 0, &state->ch2.nextEvent);
 974	mTimingDeschedule(audio->timing, &audio->ch2Event);
 975	if (audio->ch2.envelope.dead < 2 && audio->playingCh2) {
 976		mTimingSchedule(audio->timing, &audio->ch2Event, when);
 977	}
 978
 979	audio->ch3.readable = GBSerializedAudioFlagsGetCh3Readable(flags);
 980	// TODO: Big endian?
 981	memcpy(audio->ch3.wavedata32, state->ch3.wavebanks, sizeof(audio->ch3.wavedata32));
 982	LOAD_16LE(audio->ch3.length, 0, &state->ch3.length);
 983	LOAD_32LE(when, 0, &state->ch3.nextEvent);
 984	mTimingDeschedule(audio->timing, &audio->ch3Event);
 985	if (audio->playingCh3) {
 986		mTimingSchedule(audio->timing, &audio->ch3Event, when);
 987	}
 988	LOAD_32LE(when, 0, &state->ch1.nextCh3Fade);
 989	if (audio->ch3.readable && audio->style == GB_AUDIO_DMG) {
 990		mTimingSchedule(audio->timing, &audio->ch3Fade, when);
 991	}
 992
 993	LOAD_32LE(ch4Flags, 0, &state->ch4.envelope);
 994	audio->ch4.envelope.currentVolume = GBSerializedAudioFlagsGetCh4Volume(flags);
 995	audio->ch4.envelope.dead = GBSerializedAudioFlagsGetCh4Dead(flags);
 996	audio->ch4.length = GBSerializedAudioEnvelopeGetLength(ch4Flags);
 997	audio->ch4.envelope.nextStep = GBSerializedAudioEnvelopeGetNextStep(ch4Flags);
 998	LOAD_32LE(audio->ch4.lfsr, 0, &state->ch4.lfsr);
 999	LOAD_32LE(when, 0, &state->ch4.nextEvent);
1000	mTimingDeschedule(audio->timing, &audio->ch4Event);
1001	if (audio->ch4.envelope.dead < 2 && audio->playingCh4) {
1002		mTimingSchedule(audio->timing, &audio->ch4Event, when);
1003	}
1004}
1005
1006void GBAudioSerialize(const struct GBAudio* audio, struct GBSerializedState* state) {
1007	GBAudioPSGSerialize(audio, &state->audio.psg, &state->audio.flags);
1008	STORE_32LE(audio->sampleEvent.when - mTimingCurrentTime(audio->timing), 0, &state->audio.nextSample);
1009}
1010
1011void GBAudioDeserialize(struct GBAudio* audio, const struct GBSerializedState* state) {
1012	GBAudioPSGDeserialize(audio, &state->audio.psg, &state->audio.flags);
1013	uint32_t when;
1014	LOAD_32LE(when, 0, &state->audio.nextSample);
1015	mTimingDeschedule(audio->timing, &audio->sampleEvent);
1016	mTimingSchedule(audio->timing, &audio->sampleEvent, when);
1017}