Non-standard: This feature is non-standard and is not on a standards track. Do not use it on production sites facing the Web: it will not work for every user. There may also be large incompatibilities between implementations and the behavior may change in the future.
   msPlayToPreferredSourceUri is a read/write property which gets or sets the path to the preferred media source. This enables the PlayTo target device to stream the media content, which can be DRM protected, from a different location, such as a cloud media server. 
 This proprietary property is specific to Internet Explorer and Microsoft Edge.
 
ptr = object.msPlayToPreferredSourceUri;
 
 msPlayToPreferredSourceUri enables a PlayTo reference (a URI or URL) for streaming content on the PlayTo target device from a different location, such as a cloud media server. This enables web pages and Microsoft Store apps to play Digital Rights Management (DRM) protected content. The app specifies a preferred Uniform Resource Identifier (URI). This URI can point to a cloud based media server allowing streaming directly from the cloud, which can be DRM protected, instead of streaming content from the Windows machine which must be unprotected content. 
  A forward slash ("/") is appended to the URI string when it is sent over the network to a PlayTo device. This is done to conform to URI standards. 
 
  <video src="http://www.contoso.com/videos/video.mp4"
       msPlayToPreferredSourceUri="http://www.contoso.com/catalogid=1234" />
    var video = document.createElement('video');
  document.body.appendChild(video);
  video.src = "http://www.contoso.com/videos/video.mp4";
  video.msPlayToPreferredSourceUri = "http://www.contoso.com/catalogid=1234";