refactor(tracker): split Volume to PeakVolume and AverageVolume

tracker/gioui/songpanel.go

@@ -218,6 +218,6 @@ func (t *Tracker) layoutSongOptions(gtx C) D {
 			gtx.Constraints.Min = image.Pt(0, 0)
 			return recordBtnStyle.Layout(gtx)
 		}),
-		layout.Rigid(VuMeter{Volume: t.lastVolume, Range: 100}.Layout),
+		layout.Rigid(VuMeter{AverageVolume: t.lastAvgVolume, PeakVolume: t.lastPeakVolume, Range: 100}.Layout),
 	)
 }

tracker/gioui/tracker.go

@@ -55,7 +55,8 @@ type Tracker struct {
 	TrackEditor           *TrackEditor
 	Explorer              *explorer.Explorer
 
-	lastVolume tracker.Volume
+	lastAvgVolume  tracker.Volume
+	lastPeakVolume tracker.Volume
 
 	wavFilePath              string
 	quitChannel              chan struct{}
@@ -198,7 +199,8 @@ mainloop:
 			if err, ok := e.Inner.(tracker.PlayerVolumeErrorMessage); ok {
 				t.Alert.Update(err.Error(), Warning, time.Second*3)
 			}
-			t.lastVolume = e.Volume
+			t.lastAvgVolume = e.AverageVolume
+			t.lastPeakVolume = e.PeakVolume
 			t.InstrumentEditor.voiceStates = e.VoiceStates
 			t.ProcessPlayerMessage(e)
 			w.Invalidate()

tracker/gioui/vumeter.go

@@ -11,7 +11,8 @@ import (
 )
 
 type VuMeter struct {
-	Volume tracker.Volume
+	AverageVolume tracker.Volume
+	PeakVolume    tracker.Volume
 	Range         float32
 }
 
@@ -20,7 +21,7 @@ func (v VuMeter) Layout(gtx C) D {
 	gtx.Constraints.Max.Y = gtx.Dp(unit.Dp(12))
 	height := gtx.Dp(unit.Dp(6))
 	for j := 0; j < 2; j++ {
-		value := float32(v.Volume.Average[j]) + v.Range
+		value := float32(v.AverageVolume[j]) + v.Range
 		if value > 0 {
 			x := int(value/v.Range*float32(gtx.Constraints.Max.X) + 0.5)
 			if x > gtx.Constraints.Max.X {
@@ -28,7 +29,7 @@ func (v VuMeter) Layout(gtx C) D {
 			}
 			paint.FillShape(gtx.Ops, mediumEmphasisTextColor, clip.Rect(image.Rect(0, 0, x, height)).Op())
 		}
-		valueMax := float32(v.Volume.Peak[j]) + v.Range
+		valueMax := float32(v.PeakVolume[j]) + v.Range
 		if valueMax > 0 {
 			color := white
 			if valueMax >= v.Range {

tracker/player.go

@@ -21,7 +21,8 @@ type (
 		samplesSinceEvent []int
 		samplesPerRow     int
 		bpm               int
-		volume            Volume
+		avgVolumeMeter    VolumeAnalyzer
+		peakVolumeMeter   VolumeAnalyzer
 		voiceStates       [vm.MAX_VOICES]float32
 
 		recording            bool
@@ -59,7 +60,8 @@ type (
 	// Volume and SongRow are transmitted so frequently that they are treated specially, to avoid boxing. All the
 	// rest messages can be boxed to interface{}
 	PlayerMessage struct {
-		Volume      Volume
+		AverageVolume Volume
+		PeakVolume    Volume
 		SongRow       SongRow
 		VoiceStates   [vm.MAX_VOICES]float32
 		Inner         interface{}
@@ -90,7 +92,8 @@ func NewPlayer(synther sointu.Synther, playerMessages chan<- PlayerMessage, mode
 		playerMessages:  playerMessages,
 		modelMessages:   modelMessages,
 		synther:         synther,
-		volume:         Volume{Average: [2]float64{1e-9, 1e-9}, Peak: [2]float64{1e-9, 1e-9}},
+		avgVolumeMeter:  VolumeAnalyzer{Attack: 0.3, Release: 0.3, Min: -100, Max: 20},
+		peakVolumeMeter: VolumeAnalyzer{Attack: 1e-4, Release: 1, Min: -100, Max: 20},
 	}
 	return p
 }
@@ -170,11 +173,15 @@ func (p *Player) Process(buffer sointu.AudioBuffer, context PlayerProcessContext
 		}
 		// when the buffer is full, return
 		if len(buffer) == 0 {
-			err := p.volume.Analyze(oldBuffer, 0.3, 1e-4, 1, -100, 20)
+			err := p.avgVolumeMeter.Update(oldBuffer)
+			err2 := p.peakVolumeMeter.Update(oldBuffer)
 			var msg interface{}
 			if err != nil {
 				msg = PlayerVolumeErrorMessage{err}
 			}
+			if err2 != nil {
+				msg = PlayerVolumeErrorMessage{err}
+			}
 			p.trySend(msg)
 			return
 		}
@@ -323,7 +330,7 @@ func (p *Player) compileOrUpdateSynth() {
 // all sends from player are always non-blocking, to ensure that the player thread cannot end up in a dead-lock
 func (p *Player) trySend(message interface{}) {
 	select {
-	case p.playerMessages <- PlayerMessage{Volume: p.volume, SongRow: p.position, VoiceStates: p.voiceStates, Inner: message}:
+	case p.playerMessages <- PlayerMessage{AverageVolume: p.avgVolumeMeter.Level, PeakVolume: p.peakVolumeMeter.Level, SongRow: p.position, VoiceStates: p.voiceStates, Inner: message}:
 	default:
 	}
 }

tracker/volume.go

@@ -7,53 +7,61 @@ import (
 	"github.com/vsariola/sointu"
 )
 
-// Volume represents an average and peak volume measurement, in decibels. 0 dB =
+type (
-// signal level of +-1.
+	Volume [2]float64
-type Volume struct {
-	Average [2]float64
-	Peak    [2]float64
-}
 
-// Analyze updates Average and Peak fields, by analyzing the given buffer.
+	// VolumeAnalyzer measures the volume in an AudioBuffer, in decibels relative to
+	// full scale (0 dB = signal level of +-1)
+	VolumeAnalyzer struct {
+		Level   Volume  // current volume level of left and right channels
+		Attack  float64 // attack time constant in seconds
+		Release float64 // release time constant in seconds
+		Min     float64 // minimum volume in decibels
+		Max     float64 // maximum volume in decibels
+	}
+)
+
+var nanError = errors.New("NaN detected in master output")
+
+// Update updates the Level field, by analyzing the given buffer.
 //
 // Internally, it first converts the signal to decibels (0 dB = +-1). Then, the
 // average volume level is computed by smoothing the decibel values with a
-// exponentially decaying average, with a time constant tau (in seconds).
+// exponentially decaying average, with a time constant Attack (in seconds) if
-// Typical value could be 0.3 (seconds).
+// the decibel value is greater than current level and time constant Decay (in
+// seconds) if the decibel value is less than current level.
 //
-// Peak volume detection is similar exponential smoothing, but the time
+// Typical time constants for average level detection would be 0.3 seconds for
-// constants for attack and release are different. Generally attack << release.
+// both attack and release. For peak level detection, attack could be 1.5e-3 and
-// Typical values could be attack 1.5e-3 and release 1.5 (seconds)
+// release 1.5 (seconds)
 //
-// minVolume and maxVolume are hard limits in decibels to prevent negative
+// MinVolume and MaxVolume are hard limits in decibels to prevent negative
 // infinities for volumes
-func (v *Volume) Analyze(buffer sointu.AudioBuffer, tau float64, attack float64, release float64, minVolume float64, maxVolume float64) error {
+func (v *VolumeAnalyzer) Update(buffer sointu.AudioBuffer) (err error) {
-	alpha := 1 - math.Exp(-1.0/(tau*44100)) // from https://en.wikipedia.org/wiki/Exponential_smoothing
+	// from https://en.wikipedia.org/wiki/Exponential_smoothing
-	alphaAttack := 1 - math.Exp(-1.0/(attack*44100))
+	alphaAttack := 1 - math.Exp(-1.0/(v.Attack*44100))
-	alphaRelease := 1 - math.Exp(-1.0/(release*44100))
+	alphaRelease := 1 - math.Exp(-1.0/(v.Release*44100))
-	var err error
 	for j := 0; j < 2; j++ {
 		for i := 0; i < len(buffer); i++ {
 			sample2 := float64(buffer[i][j] * buffer[i][j])
 			if math.IsNaN(sample2) {
 				if err == nil {
-					err = errors.New("NaN detected in master output")
+					err = nanError
 				}
 				continue
 			}
-			dB := 10 * math.Log10(float64(sample2))
+			dB := 10 * math.Log10(sample2)
-			if dB < minVolume || math.IsNaN(dB) {
+			if dB < v.Min || math.IsNaN(dB) {
-				dB = minVolume
+				dB = v.Min
 			}
-			if dB > maxVolume {
+			if dB > v.Max {
-				dB = maxVolume
+				dB = v.Max
 			}
-			v.Average[j] += (dB - v.Average[j]) * alpha
+			a := alphaAttack
-			alphaPeak := alphaAttack
+			if dB < v.Level[j] {
-			if dB < v.Peak[j] {
+				a = alphaRelease
-				alphaPeak = alphaRelease
 			}
-			v.Peak[j] += (dB - v.Peak[j]) * alphaPeak
+			v.Level[j] += (dB - v.Level[j]) * a
 		}
 	}
 	return err