Merge pull request #5 from sinshu/reverb

Add reverb and chorus.

meltysynth/chorus.go

@@ -0,0 +1,114 @@
+package meltysynth
+
+import "math"
+
+type chorus struct {
+	bufferL []float32
+	bufferR []float32
+
+	delayTable []float32
+
+	bufferIndexL int
+	bufferIndexR int
+
+	delayTableIndexL int
+	delayTableIndexR int
+}
+
+func newChorus(sampleRate int32, delay float64, depth float64, frequency float64) *chorus {
+	c := &chorus{}
+
+	c.bufferL = make([]float32, int(float64(sampleRate)*(delay+depth))+2)
+	c.bufferR = make([]float32, int(float64(sampleRate)*(delay+depth))+2)
+
+	c.delayTable = make([]float32, int(math.Round(float64(sampleRate)/frequency)))
+	delayTableLength := len(c.delayTable)
+	for t := 0; t < delayTableLength; t++ {
+		phase := 2 * math.Pi * float64(t) / float64(delayTableLength)
+		c.delayTable[t] = float32(float64(sampleRate) * (delay + depth*math.Sin(phase)))
+	}
+
+	c.bufferIndexL = 0
+	c.bufferIndexR = 0
+
+	c.delayTableIndexL = 0
+	c.delayTableIndexR = delayTableLength / 4
+
+	return c
+}
+
+func (c *chorus) process(inputLeft []float32, intputRight []float32, outputLeft []float32, outputRight []float32) {
+	bufferLength := len(c.bufferL)
+	delayTableLength := len(c.delayTable)
+	inputLength := len(inputLeft)
+
+	for t := 0; t < inputLength; t++ {
+		position := float64(c.bufferIndexL) - float64(c.delayTable[c.delayTableIndexL])
+		if position < 0.0 {
+			position += float64(bufferLength)
+		}
+
+		index1 := int(position)
+		index2 := index1 + 1
+
+		if index2 == bufferLength {
+			index2 = 0
+		}
+
+		x1 := float64(c.bufferL[index1])
+		x2 := float64(c.bufferL[index2])
+		a := position - float64(index1)
+		outputLeft[t] = float32(x1 + a*(x2-x1))
+
+		c.bufferL[c.bufferIndexL] = inputLeft[t]
+		c.bufferIndexL++
+		if c.bufferIndexL == bufferLength {
+			c.bufferIndexL = 0
+		}
+
+		c.delayTableIndexL++
+		if c.delayTableIndexL == delayTableLength {
+			c.delayTableIndexL = 0
+		}
+	}
+
+	for t := 0; t < inputLength; t++ {
+		position := float64(c.bufferIndexR) - float64(c.delayTable[c.delayTableIndexR])
+		if position < 0.0 {
+			position += float64(bufferLength)
+		}
+
+		index1 := int(position)
+		index2 := index1 + 1
+
+		if index2 == bufferLength {
+			index2 = 0
+		}
+
+		x1 := float64(c.bufferR[index1])
+		x2 := float64(c.bufferR[index2])
+		a := position - float64(index1)
+		outputRight[t] = float32(x1 + a*(x2-x1))
+
+		c.bufferR[c.bufferIndexR] = intputRight[t]
+		c.bufferIndexR++
+		if c.bufferIndexR == bufferLength {
+			c.bufferIndexR = 0
+		}
+
+		c.delayTableIndexR++
+		if c.delayTableIndexR == delayTableLength {
+			c.delayTableIndexR = 0
+		}
+	}
+}
+
+func (c *chorus) mute() {
+	bufferLength := len(c.bufferL)
+	for t := 0; t < bufferLength; t++ {
+		c.bufferL[t] = 0
+	}
+	for t := 0; t < bufferLength; t++ {
+		c.bufferR[t] = 0
+	}
+}