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'sAudioContext.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 storedcontextTime
value was rendered by the audio output device, in the same units and origin asperformance.now()
. This is the time after the document containing the audio context was first rendered.
Syntax
js
getOutputTimestamp()
Parameters
None.
Return value
An AudioTimestamp
object, which has the following properties.
-
contextTime
: A point in the time coordinate system of thecurrentTime
for theBaseAudioContext
; the time after the audio context was first created. -
performanceTime
: A point in the time coordinate system of aPerformance
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).
js
// Press the play button
playBtn.addEventListener("click", () => {
// We can create the audioCtx as there has been some user action
if (!audioCtx) {
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
}
Specifications
Specification |
---|
Web Audio API # dom-audiocontext-getoutputtimestamp |
Browser compatibility
BCD tables only load in the browser