The MediaRecorder API (MediaStream Recording) aims to provide a really simple mechanism by which developers can record media streams from the user's input devices and instantly use them in web apps, rather than having to perform manual encoding operations on raw PCM data, etc., which would be required when using Navigator.getUserMedia() alone.
The clone() method of the MediaStream interface creates a duplicate of the MediaStream. This new MediaStream object has a new unique id and contains clones of every MediaStreamTrack contained by the MediaStream on which clone() was called.
The applyConstraints() method of the MediaStreamTrack interface applies a set of constraints to the track; these constraints let the Web site or app establish ideal values and acceptable ranges of values for the constrainable properties of the track, such as frame rate, dimensions, echo cancelation, and so forth.
The getConstraints() method of the MediaStreamTrack interface returns a MediaTrackConstraints object containing the set of constraints most recently established for the track using a prior call to applyConstraints(). These constraints indicate values and ranges of values that the Web site or application has specified are acceptable for the included constrainable properties.
The MediaTrackConstraints dictionary is used to describe a set of capabilities and the value or values each can take on. A constraints dictionary is passed into applyConstraints() to allow a script to establish a set of ideal values and/or preferred ranges of values for the track, and the most recently-requested set of custom constraints can be retrieved by calling getConstraints().
The MediaTrackSettings dictionary is used to return the current values configured for each of a MediaStreamTrack's settings. These values will adhere as closely as possible to any constraints previously set using applyConstraints(), and will adhere to the default constraints for any properties whose constraints haven't been changed, or whose customized constraints couldn't be matched.