MediaTrackConstraints: latency property
Limited availability
This feature is not Baseline because it does not work in some of the most widely-used browsers.
The MediaTrackConstraints dictionary's
latency property is a ConstrainDouble
describing the requested or mandatory constraints placed upon the value of the
latency constrainable property.
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 ConstrainDouble describing the acceptable or required value(s) for an
audio track's latency, with values specified in seconds. In audio processing, latency is
the time between the start of processing (when sound occurs in the real world, or is
generated by a hardware device) and the data being made available to the next step in
the audio input or output process. In most cases, low latency is desirable for
performance and user experience purposes, but when power consumption is a concern, or
delays are otherwise acceptable, higher latency might be acceptable.
If this property's value is a number, the user agent will attempt to obtain media whose
latency tends to be as close as possible to this number given the capabilities of the
hardware and the other constraints specified. Otherwise, the value of this
ConstrainDouble will guide the user agent in its efforts to provide an
exact match to the required latency (if exact is specified or both
min and max are provided and have the same value) or to a
best-possible value.
Note: Latency is always prone to some variation due to hardware usage demands, network constraints, and so forth, so even in an "exact" match, some variation should be expected.
Examples
See the Constraint exerciser example.
Specifications
| Specification |
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| Media Capture and Streams # dom-mediatrackconstraintset-latency |
Browser compatibility
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latency constraint
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Legend
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- Full support
- Full support
- No support
- No support
- See implementation notes.