feat: add multithreaded rendering to the tracker side

The compiled player does not support multithreading, but with this,
users can already start composing songs with slightly less powerful
machines, even when targeting high-end machines.

Related to #199

tracker/player.go

@@ -5,7 +5,6 @@ import (
 	"fmt"
 	"math"
 	"slices"
-	"time"
 
 	"github.com/vsariola/sointu"
 	"github.com/vsariola/sointu/vm"
@@ -42,7 +41,8 @@ type (
 	PlayerStatus struct {
 		SongPos     sointu.SongPos         // the current position in the score
 		VoiceLevels [vm.MAX_VOICES]float32 // a level that can be used to visualize the volume of each voice
-		CPULoad     float64                // current CPU load of the player, used to adjust the render rate
+		NumThreads  int
+		CPULoad     [vm.MAX_THREADS]sointu.CPULoad // current CPU load of the player, used to adjust the render rate
 	}
 
 	// PlayerProcessContext is the context given to the player when processing
@@ -97,9 +97,6 @@ func NewPlayer(broker *Broker, synther sointu.Synther) *Player {
 // buffer. It is used to trigger and release notes during processing. The
 // context is also used to get the current BPM from the host.
 func (p *Player) Process(buffer sointu.AudioBuffer, context PlayerProcessContext) {
-	startTime := time.Now()
-	startFrame := p.frame
-
 	p.processMessages(context)
 	p.events.adjustTimes(p.frameDeltas, p.frame, p.frame+int64(len(buffer)))
 
@@ -127,12 +124,12 @@ func (p *Player) Process(buffer sointu.AudioBuffer, context PlayerProcessContext
 		if p.synth != nil {
 			rendered, timeAdvanced, err = p.synth.Render(buffer[:framesUntilEvent], timeUntilRowAdvance)
 			if err != nil {
-				p.synth = nil
+				p.destroySynth()
 				p.send(Alert{Message: fmt.Sprintf("synth.Render: %s", err.Error()), Priority: Error, Name: "PlayerCrash", Duration: defaultAlertDuration})
 			}
 			// for performance, we don't check for NaN of every sample, because typically NaNs propagate
 			if rendered > 0 && (isNaN(buffer[0][0]) || isNaN(buffer[0][1]) || isInf(buffer[0][0]) || isInf(buffer[0][1])) {
-				p.synth = nil
+				p.destroySynth()
 				p.send(Alert{Message: "Inf or NaN detected in synth output", Priority: Error, Name: "PlayerCrash", Duration: defaultAlertDuration})
 			}
 		} else {
@@ -164,17 +161,26 @@ func (p *Player) Process(buffer sointu.AudioBuffer, context PlayerProcessContext
 		}
 		// when the buffer is full, return
 		if len(buffer) == 0 {
-			p.updateCPULoad(time.Since(startTime), p.frame-startFrame)
+			if p.synth != nil {
+				p.status.NumThreads = p.synth.CPULoad(p.status.CPULoad[:])
+			}
 			p.send(nil)
 			return
 		}
 	}
 	// we were not able to fill the buffer with NUM_RENDER_TRIES attempts, destroy synth and throw an error
-	p.synth = nil
+	p.destroySynth()
 	p.events = p.events[:0] // clear events, so we don't try to process them again
 	p.SendAlert("PlayerCrash", fmt.Sprintf("synth did not fill the audio buffer even with %d render calls", numRenderTries), Error)
 }
 
+func (p *Player) destroySynth() {
+	if p.synth != nil {
+		p.synth.Close()
+		p.synth = nil
+	}
+}
+
 func (p *Player) advanceRow() {
 	if p.song.Score.Length == 0 || p.song.Score.RowsPerPattern == 0 {
 		return
@@ -227,7 +233,7 @@ loop:
 			switch m := msg.(type) {
 			case PanicMsg:
 				if m.bool {
-					p.synth = nil
+					p.destroySynth()
 				} else {
 					p.compileOrUpdateSynth()
 				}
@@ -283,7 +289,7 @@ loop:
 				}
 			case sointu.Synther:
 				p.synther = m
-				p.synth = nil
+				p.destroySynth()
 				p.compileOrUpdateSynth()
 			default:
 				// ignore unknown messages
@@ -355,7 +361,7 @@ func (p *Player) compileOrUpdateSynth() {
 	if p.synth != nil {
 		err := p.synth.Update(p.song.Patch, p.song.BPM)
 		if err != nil {
-			p.synth = nil
+			p.destroySynth()
 			p.SendAlert("PlayerCrash", fmt.Sprintf("synth.Update: %v", err), Error)
 			return
 		}
@@ -363,7 +369,7 @@ func (p *Player) compileOrUpdateSynth() {
 		var err error
 		p.synth, err = p.synther.Synth(p.song.Patch, p.song.BPM)
 		if err != nil {
-			p.synth = nil
+			p.destroySynth()
 			p.SendAlert("PlayerCrash", fmt.Sprintf("synther.Synth: %v", err), Error)
 			return
 		}
@@ -441,14 +447,3 @@ func (p *Player) processNoteEvent(ev NoteEvent) {
 	p.synth.Trigger(oldestVoice, ev.Note)
 	TrySend(p.broker.ToModel, MsgToModel{TriggerChannel: instrIndex + 1})
 }
-
-func (p *Player) updateCPULoad(duration time.Duration, frames int64) {
-	if frames <= 0 {
-		return // no frames rendered, so cannot compute CPU load
-	}
-	realtime := float64(duration) / 1e9
-	songtime := float64(frames) / 44100
-	newload := realtime / songtime
-	alpha := math.Exp(-songtime) // smoothing factor, time constant of 1 second
-	p.status.CPULoad = float64(p.status.CPULoad)*alpha + newload*(1-alpha)
-}