MediaTrackConstraints: channelCount property
  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.
Value
  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.
Examples
See the Constraint exerciser example.
Specifications
| Specification | 
|---|
| Media Capture and Streams # dom-mediatrackconstraintset-channelcount | 
Browser compatibility
BCD tables only load in the browser