The MediaTrackConstraints dictionary's autoGainControl property is a ConstrainBoolean describing the requested or mandatory constraints placed upon the value of the autoGainControl constrainable property.

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

Automatic gain control is typically a feature provided by microphones, although it can be provided by other input sources as well.

If this value is a simple true or false, the user agent will attempt to obtain media with automatic gain control enabled or disabled as specified, if possible, but will not fail if this can't be done. If, instead, the value is given as an object with an exact field, that field's Boolean value indicates a required setting for the automatic gain control feature; if it can't be met, then the request will result in an error.

See the Constraint exerciser example.

• Media Capture and Streams API
• Capabilities, constraints, and settings
• MediaTrackConstraints
• MediaDevices.getSupportedConstraints()
• MediaTrackSupportedConstraints
• MediaStreamTrack