AudioWorkletGlobalScope: currentFrame property

Baseline Widely available

This feature is well established and works across many devices and browser versions. It’s been available across browsers since April 2021.

The read-only currentFrame property of the AudioWorkletGlobalScope interface returns an integer that represents the ever-increasing current sample-frame of the audio block being processed. It is incremented by 128 (the size of a render quantum) after the processing of each audio block.

Value

An integer number.

Examples

The AudioWorkletProcessor has access to the specific AudioWorkletGlobalScope properties:

js
// AudioWorkletProcessor defined in : test-processor.js
class TestProcessor extends AudioWorkletProcessor {
  constructor() {
    super();

    // Logs the current sample-frame and time at the moment of instantiation.
    // They are accessible from the AudioWorkletGlobalScope.
    console.log(currentFrame);
    console.log(currentTime);
  }

  // The process method is required - output silence,
  // which the outputs are already filled with.
  process(inputs, outputs, parameters) {
    return true;
  }
}

// Logs the sample rate, that is not going to change ever,
// because it's a read-only property of a BaseAudioContext
// and is set only during its instantiation.
console.log(sampleRate);

// You can declare any variables and use them in your processors
// for example it may be an ArrayBuffer with a wavetable.
const usefulVariable = 42;
console.log(usefulVariable);

registerProcessor("test-processor", TestProcessor);

The main script loads the processor, creates an instance of AudioWorkletNode, passes the name of the processor to it, and connects the node to an audio graph. We should see the output of console.log() calls in the console:

js
const audioContext = new AudioContext();
await audioContext.audioWorklet.addModule("test-processor.js");
const testNode = new AudioWorkletNode(audioContext, "test-processor");
testNode.connect(audioContext.destination);

Specifications

Specification
Web Audio API
# dom-audioworkletglobalscope-currentframe

Browser compatibility

BCD tables only load in the browser

See also