API Reference

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API Reference / BpmAnalyzer

Class: BpmAnalyzer

Defined in: core/bpm-analyzer.ts:89

Real-time BPM analyzer with typed event listeners.

This class wraps an AudioWorkletNode and provides a clean, type-safe API for analyzing beats per minute in real-time audio streams.

Remarks

This class extends native EventTarget to provide typed event listeners with full TypeScript autocomplete support. It implements the AudioNode interface for seamless integration into Web Audio API graphs.

Examples

Basic Usage

const audioContext = new AudioContext();
const bpmAnalyzer = await createRealtimeBpmAnalyzer(audioContext);

// Listen for BPM events with full type safety
bpmAnalyzer.on('bpm', (data) => {
  console.log('Current BPM:', data.bpm[0].tempo);
});

bpmAnalyzer.on('bpmStable', (data) => {
  console.log('Stable BPM:', data.bpm[0].tempo);
  console.log('Confidence:', data.bpm[0].count);
});

// Connect to audio source - use .node for audio connections
const source = audioContext.createMediaElementSource(audioElement);
source.connect(bpmAnalyzer.node);
bpmAnalyzer.node.connect(audioContext.destination);

One-time Listeners

analyzer.once('bpmStable', (data) => {
  console.log('First stable detection:', data.bpm[0].tempo);
  // This listener will be automatically removed after firing
});

Removing Listeners

// Store handler reference for cleanup
const handleBPM = (event) => {
  console.log('BPM:', event.detail.bpm);
};

// Add listener using native EventTarget API
analyzer.addEventListener('bpm', handleBPM);

// Remove with same reference
analyzer.removeEventListener('bpm', handleBPM);

Controlling the Analyzer

// Reset the analyzer state
analyzer.reset();

// Stop analysis
analyzer.stop();

// Disconnect from audio graph
analyzer.disconnect();

Extends

• EventTarget

Accessors

context

Get Signature

get context(): BaseAudioContext;

Defined in: core/bpm-analyzer.ts:339

Get the audio context associated with this analyzer

Returns

BaseAudioContext

---

numberOfInputs

Get Signature

get numberOfInputs(): number;

Defined in: core/bpm-analyzer.ts:346

Get the number of inputs

Returns

number

---

numberOfOutputs

Get Signature

get numberOfOutputs(): number;

Defined in: core/bpm-analyzer.ts:353

Get the number of outputs

Returns

number

---

channelCount

Get Signature

get channelCount(): number;

Defined in: core/bpm-analyzer.ts:360

Get the channel count

Returns

number

Set Signature

set channelCount(value): void;

Defined in: core/bpm-analyzer.ts:364

Parameters

Parameter	Type
value	number

Returns

void

---

channelCountMode

Get Signature

get channelCountMode(): ChannelCountMode;

Defined in: core/bpm-analyzer.ts:371

Get the channel count mode

Returns

ChannelCountMode

Set Signature

set channelCountMode(value): void;

Defined in: core/bpm-analyzer.ts:375

Parameters

Parameter	Type
value	ChannelCountMode

Returns

void

---

channelInterpretation

Get Signature

get channelInterpretation(): ChannelInterpretation;

Defined in: core/bpm-analyzer.ts:382

Get the channel interpretation

Returns

ChannelInterpretation

Set Signature

set channelInterpretation(value): void;

Defined in: core/bpm-analyzer.ts:386

Parameters

Parameter	Type
value	ChannelInterpretation

Returns

void

Constructors

Constructor

new BpmAnalyzer(workletNode): BpmAnalyzer;

Defined in: core/bpm-analyzer.ts:102

Creates a new BpmAnalyzer instance

Parameters

Parameter	Type	Description
workletNode	AudioWorkletNode	The AudioWorkletNode to wrap

Returns

BpmAnalyzer

Overrides

EventTarget.constructor

Methods

reset()

reset(): void;

Defined in: core/bpm-analyzer.ts:122

Reset the analyzer state to start fresh analysis

Returns

void

Remarks

This clears all internal state including detected peaks and intervals, allowing the analyzer to start analyzing as if it were newly created.

Example

// When switching to a different audio source
audioElement.src = 'new-song.mp3';
analyzer.reset();

---

stop()

stop(): void;

Defined in: core/bpm-analyzer.ts:138

Stop the analyzer

Returns

void

Remarks

This stops the analysis and resets the internal state. The analyzer will no longer emit events until analysis is restarted.

Example

analyzer.stop();

---

on()

on<K>(event, listener): void;

Defined in: core/bpm-analyzer.ts:155

Add an event listener for a specific event type

Type Parameters

Type Parameter
K extends keyof BpmAnalyzerEventMap

Parameters

Parameter	Type	Description
event	K	The event name to listen for
listener	(data) => void	The callback function to invoke when the event is emitted

Returns

void

Example

analyzer.on('bpm', (data) => {
  console.log('Current BPM:', data.bpm[0].tempo);
});

---

once()

once<K>(event, listener): void;

Defined in: core/bpm-analyzer.ts:179

Add a one-time event listener that will be removed after being called once

Type Parameters

Type Parameter
K extends keyof BpmAnalyzerEventMap

Parameters

Parameter	Type	Description
event	K	The event name to listen for
listener	(data) => void	The callback function to invoke when the event is emitted

Returns

void

Example

analyzer.once('bpmStable', (data) => {
  console.log('First stable BPM detected:', data.bpm[0].tempo);
});

---

connect()

Call Signature

connect(
   destinationNode, 
   outputIndex?, 
   inputIndex?
): AudioNode;

Defined in: core/bpm-analyzer.ts:204

Connect the analyzer to an audio destination

Parameters

Parameter	Type	Description
destinationNode	AudioNode	The destination node to connect to
outputIndex?	number	The output index (default: 0)
inputIndex?	number	The input index on the destination (default: 0)

Returns

AudioNode

The destination node for chaining

Example

analyzer.connect(audioContext.destination);

Call Signature

connect(destinationParameter, outputIndex?): void;

Defined in: core/bpm-analyzer.ts:209

Connect the analyzer to an audio destination

Parameters

Parameter	Type	Description
destinationParameter	AudioParam	-
outputIndex?	number	The output index (default: 0)

Returns

void

The destination node for chaining

Example

analyzer.connect(audioContext.destination);

---

disconnect()

Call Signature

disconnect(
   destinationNode?, 
   outputIndex?, 
   inputIndex?
): void;

Defined in: core/bpm-analyzer.ts:238

Disconnect the analyzer from all destinations or a specific destination

Parameters

Parameter	Type	Description
destinationNode?	AudioNode	Optional destination node to disconnect from
outputIndex?	number	The output index (default: 0)
inputIndex?	number	The input index on the destination (default: 0)

Returns

void

Example

// Disconnect from all destinations
analyzer.disconnect();

// Disconnect from a specific destination
analyzer.disconnect(audioContext.destination);

Call Signature

disconnect(destinationParameter?, outputIndex?): void;

Defined in: core/bpm-analyzer.ts:243

Disconnect the analyzer from all destinations or a specific destination

Parameters

Parameter	Type	Description
destinationParameter?	AudioParam	-
outputIndex?	number	The output index (default: 0)

Returns

void

Example

// Disconnect from all destinations
analyzer.disconnect();

// Disconnect from a specific destination
analyzer.disconnect(audioContext.destination);

Properties

Property	Modifier	Type	Description	Defined in
node	readonly	AudioWorkletNode	The underlying AudioWorkletNode Remarks Exposed for advanced use cases. Most users should interact with the BpmAnalyzer API instead of directly accessing the worklet node.	core/bpm-analyzer.ts:96