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

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

If this value is a number, the user agent will attempt to obtain media whose channel count is as close as possible to this number given the capabilities of the hardware and the other constraints specified. Otherwise, the value of this ConstrainULong will guide the user agent in its efforts to provide an exact match to the required channel count (if exact is specified or both min and max are provided and have the same value) or to a best-possible value.

The channel count is 1 for monaural sound, 2 for stereo, and so forth.

See the Constraint exerciser example.

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