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mgba
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Start implementing channel 4

This commit is contained in:
Jeffrey Pfau 2013-10-18 01:21:44 -07:00
parent eac9dfb325
commit 7393351e27
2 changed files with 41 additions and 6 deletions
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44
src/gba/gba-audio.c
View File

@ -21,6 +21,7 @@ void GBAAudioInit(struct GBAAudio* audio) {
audio->nextCh2 = 0;
audio->nextCh3 = 0;
audio->nextCh4 = 0;
audio->ch4.sample = 0;
audio->eventDiff = 0;
audio->nextSample = 0;
audio->sampleRate = 0x8000;
@ -46,6 +47,8 @@ void GBAAudioDeinit(struct GBAAudio* audio) {
int32_t GBAAudioProcessEvents(struct GBAAudio* audio, int32_t cycles) {
audio->nextEvent -= cycles;
if (audio->nextEvent <= 0) {
audio->nextEvent = INT_MAX;
audio->nextCh1 -= audio->eventDiff;
audio->nextCh2 -= audio->eventDiff;
audio->nextCh3 -= audio->eventDiff;
@ -65,6 +68,9 @@ int32_t GBAAudioProcessEvents(struct GBAAudio* audio, int32_t cycles) {
if ((audio->ch4Right || audio->ch4Left) && audio->nextCh4 <= 0) {
audio->nextCh4 += _updateChannel4(&audio->ch4);
if (audio->nextCh4 < audio->nextEvent) {
audio->nextEvent = audio->nextCh4;
}
}
audio->nextSample -= audio->eventDiff;
@ -73,7 +79,9 @@ int32_t GBAAudioProcessEvents(struct GBAAudio* audio, int32_t cycles) {
audio->nextSample += audio->sampleInterval;
}
audio->nextEvent = audio->nextSample;
if (audio->nextSample < audio->nextEvent) {
audio->nextEvent = audio->nextSample;
}
audio->eventDiff = audio->nextEvent;
}
return audio->nextEvent;
@ -132,6 +140,14 @@ void GBAAudioWriteSOUND4CNT_LO(struct GBAAudio* audio, uint16_t value) {
void GBAAudioWriteSOUND4CNT_HI(struct GBAAudio* audio, uint16_t value) {
audio->ch4.control.packed = value;
if (audio->ch4.control.restart) {
if (audio->ch4.control.power) {
audio->ch4.lfsr = 0x40;
} else {
audio->ch4.lfsr = 0x4000;
}
audio->nextCh4 = 0;
}
}
void GBAAudioWriteSOUNDCNT_LO(struct GBAAudio* audio, uint16_t value) {
@ -200,27 +216,43 @@ static int32_t _updateChannel3(struct GBAAudioChannel3* ch) {
}
static int32_t _updateChannel4(struct GBAAudioChannel4* ch) {
return INT_MAX / 4;
int lsb = ch->lfsr & 1;
ch->sample = lsb * 0xFF - 0x80;
ch->lfsr >>= 1;
ch->lfsr ^= (lsb * 0x60) << (ch->control.power ? 0 : 8);
int timing = ch->control.ratio ? 2 * ch->control.ratio : 1;
timing <<= ch->control.frequency;
timing *= 32;
return timing;
}
static void _sample(struct GBAAudio* audio) {
int32_t sampleLeft = 0;
int32_t sampleRight = 0;
int psgShift = 2 - audio->volume;
if (audio->ch4Left) {
sampleLeft += audio->ch4.sample >> psgShift;
}
if (audio->ch4Right) {
sampleRight += audio->ch4.sample >> psgShift;
}
if (audio->chALeft) {
sampleLeft += audio->chA.sample;
sampleLeft += audio->chA.sample >> audio->volumeChA;
}
if (audio->chARight) {
sampleRight += audio->chA.sample;
sampleRight += audio->chA.sample >> audio->volumeChA;
}
if (audio->chBLeft) {
sampleLeft += audio->chB.sample;
sampleLeft += audio->chB.sample >> audio->volumeChB;
}
if (audio->chBRight) {
sampleRight += audio->chB.sample;
sampleRight += audio->chB.sample >> audio->volumeChB;
}
pthread_mutex_lock(&audio->bufferMutex);

3
src/gba/gba-audio.h
View File

@ -98,6 +98,9 @@ struct GBAAudioChannel4 {
};
uint16_t packed;
} control;
unsigned lfsr;
int8_t sample;
};
struct GBAAudioFIFO {