AudioContext: getOutputTimestamp() method

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 getOutputTimestamp() method 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

getOutputTimestamp()

Return value

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

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).

// Press the play button
playBtn.addEventListener("click", () => {
 // We can create the audioCtx as there has been some user action
 audioCtx ??= new AudioContext();
 source = new AudioBufferSourceNode(audioCtx);
 getData();
 source.start(0);
 playBtn.disabled = true;
 stopBtn.disabled = false;
 rAF = requestAnimationFrame(outputTimestamps);
});
// Press the stop button
stopBtn.addEventListener("click", () => {
 source.stop(0);
 playBtn.disabled = false;
 stopBtn.disabled = true;
 cancelAnimationFrame(rAF);
});
// Helper function to output timestamps
function outputTimestamps() {
 const ts = audioCtx.getOutputTimestamp();
 output.textContent = `Context time: ${ts.contextTime} | Performance time: ${ts.performanceTime}`;
 rAF = requestAnimationFrame(outputTimestamps); // Reregister itself
}