MediaTrackSettings: latency property

Limited availability

This feature is not Baseline because it does not work in some of the most widely-used browsers.

The MediaTrackSettings dictionary's latency property is a double-precision floating-point number indicating the estimated latency (specified in seconds) of the MediaStreamTrack as currently configured. This lets you determine what value was selected to comply with your specified constraints for this property's value as described in the MediaTrackConstraints.latency property you provided when calling either getUserMedia() or MediaStreamTrack.applyConstraints().

This is, of course, an approximation, since latency can vary for many reasons including CPU, transmission, and storage overhead.

If needed, you can determine whether or not this constraint is supported by checking the value of MediaTrackSupportedConstraints.latency as returned by a call to MediaDevices.getSupportedConstraints(). However, typically this is unnecessary since browsers will ignore any constraints they're unfamiliar with.

Because RTP doesn't include this information, tracks associated with a WebRTC RTCPeerConnection will never include this property.

Value

A double-precision floating-point number indicating the estimated latency, in seconds, of the audio track as currently configured.

Examples

See the Constraint exerciser example.

Specifications

Specification
Media Capture and Streams
# dom-mediatrackconstraintset-latency

Browser compatibility

desktop mobile
Chrome
Edge
Firefox
Opera
Safari
Chrome Android
Firefox for Android
Opera Android
Safari on iOS
Samsung Internet
WebView Android
WebView on iOS
latency constraint
Chrome – Full support
Chrome 59 (Release date: 2017-06-05)
footnote Full support
Edge – Full support
Edge 79 (Release date: 2020-01-15)
footnote Full support
Firefox – Full support
Firefox 50 (Release date: 2016-11-15)
footnote Full support
Opera – Full support
Opera 46 (Release date: 2017-06-22)
footnote Full support
Safari – No support
Safari
footnote
footnote See bug 169871
Chrome Android – Full support
Chrome Android 59 (Release date: 2017-06-06)
footnote Full support
Firefox for Android – Full support
Firefox for Android 50 (Release date: 2016-11-15)
footnote Full support
Opera Android – Full support
Opera Android 43 (Release date: 2017-09-27)
footnote Full support
Safari on iOS – No support
Safari on iOS
footnote
footnote See bug 169871
Samsung Internet – Full support
Samsung Internet 7 (Release date: 2018-03-16)
footnote Full support
WebView Android – Full support
WebView Android 59 (Release date: 2017-06-06)
footnote Full support
WebView on iOS – No support
WebView on iOS
footnote
footnote See bug 169871

Legend

Tip: you can click/tap on a cell for more information.

Full support
Full support
No support
No support
See implementation notes.

See also