AudioContext.getOutputTimestamp() - Web APIs 编辑

The getOutputTimestamp() property of the AudioContext interface returns a new AudioTimestamp object containing two audio timestamp values relating to the current audio context.

The two values are as follows:

• AudioTimestamp.contextTime: The time of the sample frame currently being rendered by the audio output device (i.e., output audio stream position), in the same units and origin as the context's AudioContext.currentTime. Basically, this is the time after the audio context was first created.
• AudioTimestamp.performanceTime: An estimation of the moment when the sample frame corresponding to the stored contextTime value was rendered by the audio output device, in the same units and origin as performance.now(). This is the time after the document containing the audio context was first rendered.

Syntax

var timestamp = AudioContext.getOutputTimestamp()

Parameters

None.

Returns

An AudioTimestamp object, which has the following properties.

• contextTime: A point in the time coordinate system of the currentTime for the BaseAudioContext; the time after the audio context was first created.
• performanceTime: A point in the time coordinate system of a Performance interface; the time after the document containing the audio context was first rendered

Examples

In the following code we start to play an audio file after a play button is clicked, and start off a requestAnimationFrame loop running, which constantly outputs the contextTime and performanceTime.

You can see full code of this example at output-timestamp (see it live also).

play.addEventListener('click', () => {
  if(!audioCtx) {
    audioCtx = new window.AudioContext();
  }

  getData();
  source.start(0);
  play.setAttribute('disabled', 'disabled');

  rAF = requestAnimationFrame(outputTimestamps);
});

stop.addEventListener('click', () => {
  source.stop(0);
  play.removeAttribute('disabled');
  cancelAnimationFrame(rAF);
});

// function to output timestamps

function outputTimestamps() {
  let ts = audioCtx.getOutputTimestamp()
  console.log('Context time: ' + ts.contextTime + ' | Performance time: ' + ts.performanceTime);
  rAF = requestAnimationFrame(outputTimestamps);
}

Specifications

Browser Compatibility

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