2.1.1 [W3C-MEDIA-SOURCE] Section 2. MediaSource Object

V0001: The duration attribute is not unrestricted

The specification states:

 2. MediaSource Object
 The MediaSource object represents a source of media data for an HTMLMediaElement. It 
 keeps track of the readyState for this source as well as a list of SourceBuffer objects 
 that can be used to add media data to the presentation. ...
     interface MediaSource : EventTarget {
         attribute unrestricted double duration;
 2.1 Attributes 
     duration of type unrestricted double
         Allows the web application to set the presentation duration. The duration is 
         initially set to NaN when the MediaSource object is created.

EdgeHTML Mode

The duration attribute is not unrestricted.

        attribute double duration;