Updated: June 10, 2010
Applies To: Windows 7, Windows Server 2008, Windows Server 2008 R2, Windows Vista
The Web Playlists extension for IIS 7 controls media delivery to clients and limits a client’s ability to seek or skip playlist media entries. Server administrators can enable or disable player seek/skip behavior by configuring fields in the playlist media entry. This feature exists as a Request Handler for the IIS pipeline. The actual playlist database is stored in separate Web playlist files (files that have .isx file name extensions).
When a user requests a playlist by clicking a link on a Web site page, the request for media assets referenced by the playlist is fulfilled in the following way:
The HTTP request is sent to the IIS request-processing pipeline, which authenticates and authorizes the request, and then passes it to the Web Playlists handler.
The Web Playlists handler processes the request and creates a user session. It then passes all request parameters to the Web Playlists provider.
The Web Playlists provider resolves any required Windows user processing (for example, impersonation credentials), and then retrieves the media assets referenced in the playlist for the Web Playlists handler.
The Web Playlists handler generates a GUID for the user session, creates obfuscated URLs (in .asx format) for each media asset referenced in the playlist, and then delivers each media asset as a bit stream in an HTTP response to the client.
As the client renders each media asset referenced by the playlist, the Web Playlists handler uses the user session to track how much content was viewed and to enforce playback constraints in the client's player, such as whether the client can skip within the currently playing asset (seek), skip to the next asset (skip forward), or start playing the previously played asset again from the beginning (skip backward).