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The AudioContext() constructor creates a new AudioContext object which represents an audio-processing graph, built from audio modules linked together, each represented by an AudioNode.

Syntax

var audioCtx = new AudioContext();
var audioCtx = new AudioContext(options);

Parameters

options Optional
An object based on the AudioContextOptions dictionary that contains zero or more optional properties to configure the new context. Available properties are as follows:
latencyHint Optional
The type of playback that the context will be used for, as a value from the AudioContextLatencyCategory enum or a double-precision floating-point value indicating the preferred maximum latency of the context in seconds. The user agent may or may not choose to meet this request; check the value of AudioContext.baseLatency to determine the true latency after creating the context.
sampleRate Optional
The sampleRate to be used by the AudioContext, specified in samples per second. The value may be any value supported by AudioBuffer. If not specified, the preferred sample rate for the context's output device is used by default.

Return value

The newly constructed AudioContext instance.

Exceptions

NotSupportedError
The specified sampleRate isn't supported by the context.

Usage notes

The specification doesn't go into a lot of detail about things like how many audio contexts a user agent should support, or minimum or maximum latency requirements (if any), so these details can vary from browser to browser. Be sure to check the values if they matter to you.

In particular, the specification doesn't indicate a maximum or minimum number of audio contexts that must be able to be open at the same time, so this is left up to the browser implementations to decide.

Google Chrome

Per-tab audio context limitation in Chrome

Google Chrome only supports up to six audio contexts per tab at a time, because each context spawns a new thread. This limitation is intended to help protect overhead problems that could arise if too many audio contexts are created (along with their threads). If you try to create more than six contexts, AudioContext() will throw a DOMException with the message "The number of hardware contexts provided (6) is greater than or equal to the maximum bound (6)".

You should try to reuse existing contexts rather than creating a new one for each sound you play, and be sure to call close() on each context as you finish using it. Once close()'s Promise is resolved, it's safe to create a new context.

Non-standard exceptions in Chrome

If the value of the latencyHint  property isn't valid, Chrome throws a TypeError exception with the message "The provided value '...' is not a valid enum value of type AudioContextLatencyCategory".

Example

This example creates a new AudioContext for interactive audio (optimizing for latency) and a sample rate of 44.1kHz.

var AudioContext = window.AudioContext || window.webkitAudioContext;

var audioCtx = new AudioContext({
  latencyHint: 'interactive',
  sampleRate: 44100,
});

Specifications

Specification Status Comment
Web Audio API
The definition of 'AudioContext()' in that specification.
Working Draft Initial definition.

Browser compatibility

FeatureChromeEdgeFirefoxInternet ExplorerOperaSafari
Basic support551 2 Yes25 No42 Yes webkit
latencyHint option60 No No No47 ?
sampleRate option No3 No No No No ?
FeatureAndroid webviewChrome for AndroidEdge mobileFirefox for AndroidOpera AndroidiOS SafariSamsung Internet
Basic support55551 2 ?2542 ?6.0
latencyHint option6060 ? No47 ? No
sampleRate option ? ? ? ? ? ? No

1. Each tab is limited to 6 audio contexts in Chrome; attempting to create more will throw a DOMException. For details see Per-tab audio context limitation in Chrome.

2. If latencyHint isn't valid, Chrome throws a TypeError exception. See Non-standard exceptions in Chrome for details.

3. See issue 432248 for Chrome support.

See also

Étiquettes et contributeurs liés au document

Dernière mise à jour par : Sheppy,