fix(synth): ensure we end playback fast at end of loops and songs

packages/alphatab/src/synth/AlphaSynth.ts

@@ -1,29 +1,38 @@
+import {
+    EventEmitter,
+    EventEmitterOfT,
+    type IEventEmitter,
+    type IEventEmitterOfT
+} from '@coderline/alphatab/EventEmitter';
+import { ByteBuffer } from '@coderline/alphatab/io/ByteBuffer';
+import { Logger } from '@coderline/alphatab/Logger';
+import type { LogLevel } from '@coderline/alphatab/LogLevel';
+import type { MidiEvent, MidiEventType } from '@coderline/alphatab/midi/MidiEvent';
 import type { MidiFile } from '@coderline/alphatab/midi/MidiFile';
+import { MidiUtils } from '@coderline/alphatab/midi/MidiUtils';
+import { ModelUtils } from '@coderline/alphatab/model/ModelUtils';
+import type { Score } from '@coderline/alphatab/model/Score';
+import { Queue } from '@coderline/alphatab/synth/ds/Queue';
 import type { BackingTrackSyncPoint, IAlphaSynth } from '@coderline/alphatab/synth/IAlphaSynth';
+import {
+    AudioExportChunk,
+    type AudioExportOptions,
+    type IAudioExporter
+} from '@coderline/alphatab/synth/IAudioExporter';
+import type { IAudioSampleSynthesizer } from '@coderline/alphatab/synth/IAudioSampleSynthesizer';
 import type { ISynthOutput } from '@coderline/alphatab/synth/ISynthOutput';
+import { MidiEventsPlayedEventArgs } from '@coderline/alphatab/synth/MidiEventsPlayedEventArgs';
 import { MidiFileSequencer } from '@coderline/alphatab/synth/MidiFileSequencer';
 import type { PlaybackRange } from '@coderline/alphatab/synth/PlaybackRange';
+import { PlaybackRangeChangedEventArgs } from '@coderline/alphatab/synth/PlaybackRangeChangedEventArgs';
 import { PlayerState } from '@coderline/alphatab/synth/PlayerState';
 import { PlayerStateChangedEventArgs } from '@coderline/alphatab/synth/PlayerStateChangedEventArgs';
 import { PositionChangedEventArgs } from '@coderline/alphatab/synth/PositionChangedEventArgs';
 import { Hydra } from '@coderline/alphatab/synth/soundfont/Hydra';
-import { TinySoundFont } from '@coderline/alphatab/synth/synthesis/TinySoundFont';
-import { EventEmitter, type IEventEmitter, type IEventEmitterOfT, EventEmitterOfT } from '@coderline/alphatab/EventEmitter';
-import { ByteBuffer } from '@coderline/alphatab/io/ByteBuffer';
-import { Logger } from '@coderline/alphatab/Logger';
-import type { LogLevel } from '@coderline/alphatab/LogLevel';
 import { SynthConstants } from '@coderline/alphatab/synth/SynthConstants';
-import type { SynthEvent } from '@coderline/alphatab/synth/synthesis/SynthEvent';
-import { Queue } from '@coderline/alphatab/synth/ds/Queue';
-import { MidiEventsPlayedEventArgs } from '@coderline/alphatab/synth/MidiEventsPlayedEventArgs';
-import type { MidiEvent, MidiEventType } from '@coderline/alphatab/midi/MidiEvent';
-import { PlaybackRangeChangedEventArgs } from '@coderline/alphatab/synth/PlaybackRangeChangedEventArgs';
-import { ModelUtils } from '@coderline/alphatab/model/ModelUtils';
-import type { Score } from '@coderline/alphatab/model/Score';
-import type { IAudioSampleSynthesizer } from '@coderline/alphatab/synth/IAudioSampleSynthesizer';
-import { AudioExportChunk, type IAudioExporter, type AudioExportOptions } from '@coderline/alphatab/synth/IAudioExporter';
 import type { Preset } from '@coderline/alphatab/synth/synthesis/Preset';
-import { MidiUtils } from '@coderline/alphatab/midi/MidiUtils';
+import type { SynthEvent } from '@coderline/alphatab/synth/synthesis/SynthEvent';
+import { TinySoundFont } from '@coderline/alphatab/synth/synthesis/TinySoundFont';
 
 /**
  * This is the base class for synthesizer components which can be used to
@@ -284,6 +293,20 @@ export class AlphaSynthBase implements IAlphaSynth {
             }
             this._notPlayedSamples += samples.length;
             this.output.addSamples(samples);
+
+
+            // if the sequencer finished, we instantly force a noteOff on all 
+            // voices to complete playback and stop voices fast. 
+            // Doing this in the samplePlayed callback is too late as we might
+            // continue generating audio for long-release notes (especially percussion like cymbals)
+
+            // we still have checkForFinish which takes care of the counterpart
+            // on the sample played area to ensure we seek back. 
+            // but thanks to this code we ensure the output will complete fast as we won't 
+            // be adding more samples beside a 0.1s ramp-down
+            if (this.sequencer.isFinished) {
+                this.synthesizer.noteOffAll(true);
+            }
         } else {
             // Tell output that there is no data left for it.
             const samples: Float32Array = new Float32Array(0);

packages/alphatab/src/synth/SynthConstants.ts

@@ -35,4 +35,9 @@ export class SynthConstants {
 
     public static readonly MicroBufferCount: number = 32;
     public static readonly MicroBufferSize: number = 64;
+
+    /**
+     * approximately -60 dB, which is inaudible to humans
+     */
+    public static readonly AudibleLevelThreshold: number = 1e-3;
 }

packages/alphatab/src/synth/synthesis/Voice.ts

@@ -213,20 +213,19 @@ export class Voice {
                 noteGain = SynthHelper.decibelsToGain(this.noteGainDb + this.modLfo.level * tmpModLfoToVolume);
             }
 
-            gainMono = noteGain * this.ampEnv.level;
+            // Update EG.
+            this.ampEnv.process(blockSamples, f.outSampleRate);
+            if (updateModEnv) {
+                this.modEnv.process(blockSamples, f.outSampleRate);
+            }
 
+            gainMono = noteGain * this.ampEnv.level;
             if (isMuted) {
                 gainMono = 0;
             } else {
                 gainMono *= this.mixVolume;
             }
 
-            // Update EG.
-            this.ampEnv.process(blockSamples, f.outSampleRate);
-            if (updateModEnv) {
-                this.modEnv.process(blockSamples, f.outSampleRate);
-            }
-
             // Update LFOs.
             if (updateModLFO) {
                 this.modLfo.process(blockSamples);
@@ -321,7 +320,15 @@ export class Voice {
                     break;
             }
 
-            if (tmpSourceSamplePosition >= tmpSampleEndDbl || this.ampEnv.segment === VoiceEnvelopeSegment.Done) {
+            const inaudible =
+                this.ampEnv.segment === VoiceEnvelopeSegment.Release &&
+                Math.abs(gainMono) < SynthConstants.AudibleLevelThreshold;
+            if (
+                tmpSourceSamplePosition >= tmpSampleEndDbl ||
+                this.ampEnv.segment === VoiceEnvelopeSegment.Done ||
+                // Check if voice is inaudible during release to terminate early
+                inaudible
+            ) {
                 this.kill();
                 return;
             }