fix

pkg/gba/apu.go

@@ -54,7 +54,8 @@ const (
 	SAMP_CYCLES              = (CPU_FREQ_HZ / SND_FREQUENCY)
 	BUFF_SAMPLES             = ((SND_SAMPLES) * 16 * 2)
 	BUFF_SAMPLES_MSK         = ((BUFF_SAMPLES) - 1)
-	SAMPLE_TIME      float64 = 1.0 / 32768
+	SAMPLE_TIME      float64 = 1.0 / SND_FREQUENCY
+	STREAM_LEN               = ((SND_SAMPLES) * 16 * 2 * 2)
 )
 
 const (
@@ -86,9 +87,9 @@ type SoundChan struct {
 }
 
 func newAPU() *APU {
-	stream = make([]byte, BUFF_SAMPLES)
+	stream = make([]byte, STREAM_LEN)
 
-	context, err := oto.NewContext(SND_FREQUENCY, 2, 2, BUFF_SAMPLES)
+	context, err := oto.NewContext(SND_FREQUENCY, 2, 2, STREAM_LEN)
 	if err != nil {
 		panic(err)
 	}
@@ -283,7 +284,7 @@ func (g *GBA) waveSample() int8 {
 		g.apu.chans[2].samples -= cycleSamples
 
 		waveSamples--
-		if waveSamples > 0 {
+		if waveSamples != 0 {
 			wavePosition = (wavePosition + 1) & 0b0011_1111
 		} else {
 			g.waveReset()
@@ -311,9 +312,9 @@ func (g *GBA) waveSample() int8 {
 	}
 
 	if samp >= 0 {
-		return int8(int16(samp) * PSG_MAX / 7)
+		return int8(float64(samp) / 7 * PSG_MAX)
 	}
-	return int8(int16(samp) * PSG_MIN / (-8))
+	return int8(float64(samp) / (-8) * PSG_MIN)
 }
 
 func (g *GBA) noiseSample() int8 {
@@ -323,12 +324,12 @@ func (g *GBA) noiseSample() int8 {
 
 	cnth := g._getRAM(ram.SOUND4CNT_H) // ctrl
 
-	// Actual frequency in Hertz
-	freqDiv, freqRsh := float64(cnth&0x7), float64((cnth>>4)&0xf)
-	if freqDiv == 0 {
-		freqDiv = 1 / 2
+	// Actual frequency in Hertz (524288 / r / 2^(s+1))
+	r, s := float64(cnth&0x7), float64((cnth>>4)&0xf)
+	if r == 0 {
+		r = 0.5
 	}
-	frequency := (524288 / freqDiv) / math.Pow(2, freqRsh+1)
+	frequency := (524288 / r) / math.Pow(2, s+1)
 
 	cntl := g._getRAM(ram.SOUND4CNT_L) // env
 	// Full length of the generated wave (if enabled) in seconds
@@ -422,7 +423,7 @@ var sndBuffer [BUFF_SAMPLES]int16
 var stream []byte
 
 func (g *GBA) soundMix() {
-	for i := 0; i < BUFF_SAMPLES; i += 4 {
+	for i := 0; i < STREAM_LEN; i += 4 {
 		snd := sndBuffer[sndCurPlay&BUFF_SAMPLES_MSK] << 6
 		stream[i+0], stream[i+1] = byte(snd), byte(snd>>8)
 		sndCurPlay++
@@ -432,7 +433,12 @@ func (g *GBA) soundMix() {
 	}
 
 	// Avoid desync between the Play cursor and the Write cursor
-	sndCurPlay += uint32(int32(sndCurWrite-sndCurPlay)>>8) & ^uint32(1)
+	delta := (int32(sndCurWrite-sndCurPlay) >> 8) - (int32(sndCurWrite-sndCurPlay)>>8)%2
+	if delta >= 0 {
+		sndCurPlay += uint32(delta)
+	} else {
+		sndCurPlay -= uint32(-delta)
+	}
 }
 
 var (
@@ -478,6 +484,9 @@ func (g *GBA) fifoALoad() {
 	for i := byte(0); i < fifoALen; i++ {
 		fifoA[i] = fifoA[i+1]
 	}
+	for i := fifoALen; i < 0x20; i++ {
+		fifoA[i] = 0
+	}
 }
 
 func (g *GBA) fifoBLoad() {
@@ -491,6 +500,9 @@ func (g *GBA) fifoBLoad() {
 	for i := byte(0); i < fifoBLen; i++ {
 		fifoB[i] = fifoB[i+1]
 	}
+	for i := fifoBLen; i < 0x20; i++ {
+		fifoB[i] = 0
+	}
 }
 
 var (