getusermedia constraints documentation
dictionary MediaTrackConstraintSet {
ConstrainULong width;
ConstrainULong height;
ConstrainDouble aspectRatio;
ConstrainDouble frameRate;
ConstrainDOMString facingMode;
ConstrainDOMString resizeMode;
ConstrainULong sampleRate;
ConstrainULong sampleSize;
ConstrainBoolean echoCancellation;
ConstrainBoolean autoGainControl;
ConstrainBoolean noiseSuppression;
ConstrainDouble latency;
ConstrainULong channelCount;
ConstrainDOMString deviceId;
ConstrainDOMString groupId;
};