Fixing panning so it's on the correct channels

Author: Jason Crawford

mixing/mixbuffer.go

@@ -30,15 +30,8 @@ type MixBuffer []ChannelMixBuffer
 func (m *MixBuffer) C() (chan<- SampleMixIn, func()) {
 	ch := make(chan SampleMixIn, 32)
 	go func() {
-	outerLoop:
-		for {
-			select {
-			case d, ok := <-ch:
-				if !ok {
-					break outerLoop
-				}
-				m.MixInSample(d)
-			}
+		for d := range ch {
+			m.MixInSample(d)
 		}
 	}()
 	return ch, func() {
@@ -86,7 +79,7 @@ func (m *MixBuffer) ToRenderData(samples int, bitsPerSample int, mixerVolume vol
 		for _, buf := range *m {
 			v := buf[i] * mixerVolume
 			val := v.ToSample(bitsPerSample)
-			binary.Write(writer, binary.LittleEndian, val)
+			_ = binary.Write(writer, binary.LittleEndian, val) // lint
 		}
 	}
 	return writer.Bytes()
@@ -138,7 +131,7 @@ func (m *MixBuffer) ToRenderDataWithBufs(outBuffers [][]byte, samples int, bitsP
 				pos += 4
 			default:
 				writer := &bytes.Buffer{}
-				binary.Write(writer, binary.LittleEndian, val)
+				_ = binary.Write(writer, binary.LittleEndian, val) // lint
 				pos += copy(out[pos:], writer.Bytes())
 			}
 		}

mixing/panmixer.go

@@ -43,9 +43,13 @@ type panMixerStereo struct {
 
 func (p panMixerStereo) GetMixingMatrix(pan panning.Position) volume.Matrix {
 	pangle := float64(pan.Angle)
-	d := volume.Volume(pan.Distance)
-	l := d * volume.Volume(math.Cos(pangle))
-	r := d * volume.Volume(math.Sin(pangle))
+	s, c := math.Sincos(pangle)
+	var d volume.Volume
+	if pan.Distance > 0 {
+		d = 1 / volume.Volume(pan.Distance*pan.Distance)
+	}
+	l := d * volume.Volume(s)
+	r := d * volume.Volume(c)
 	return volume.Matrix{l, r}
 }
 
@@ -59,11 +63,16 @@ type panMixerQuad struct {
 
 func (p panMixerQuad) GetMixingMatrix(pan panning.Position) volume.Matrix {
 	pangle := float64(pan.Angle)
-	d := volume.Volume(pan.Distance)
-	lf := d * volume.Volume(math.Cos(pangle))
-	rf := d * volume.Volume(math.Sin(pangle))
-	lr := d * volume.Volume(math.Sin(pangle+math.Pi/2.0))
-	rr := d * volume.Volume(math.Cos(pangle-math.Pi/2.0))
+	sf, cf := math.Sincos(pangle)
+	sr, cr := math.Sin(pangle+math.Pi/2.0), math.Cos(pangle-math.Pi/2.0)
+	var d volume.Volume
+	if pan.Distance > 0 {
+		d = 1 / volume.Volume(pan.Distance*pan.Distance)
+	}
+	lf := d * volume.Volume(sf)
+	rf := d * volume.Volume(cf)
+	lr := d * volume.Volume(cr)
+	rr := d * volume.Volume(sr)
 	return volume.Matrix{lf, rf, lr, rr}
 }