the media stream source is the api responsible for enabling adaptive streaming of media. adaptive streaming allows the player application to choose the bit rate of the media based on available client bandwidth and central processing unit (cpu) resources. media stream source allows the developer to specify a custom method of retrieving media data, the only requirement being that the final video and audio streams be presented to silverlight runtime in a format that silverlight can decode (vc-1, h.264, wma, mp3, etc.). this allows extensible support for otherwise natively unsupported file formats (i.e. mp4, matroska, ogg), protocols (i.e. shoutcast) and delivery methods (i.e. adaptive streaming, peer-to-peer (p2p)). microsoft first publicly showcased media stream source by powering the nbc olympics website with their own implementation of adaptive streaming.