Working with WTV Files
Windows Media Center takes advantage of the Stream Buffer Engine (SBE), which enables an application to seek, pause, and record a live video stream without interrupting the stream. Transitions between live and recorded content are seamless. Currently, the SBE supports MPEG-2 video and audio using MPEG-1 Layer II or Dolby Digital AC-3 (ATSC A/52), at capture rates of up to 30 megabits per second (Mbps). When Windows Media Center records a television show, the audio and video elementary streams are encrypted. The SBE then writes the file to a directory (by default, to \Users\public\Recorded TV\) as a file with the .wtv extension.
Previous versions of Windows Media Center recorded TV files using the .dvr-ms format. Windows 7 provides a utility to convert .wtv files to .dvr-ms to support those applications that were designed to work with the.dvr-ms format. To use this utility, right-click a .wtv file in Windows Explorer and select Convert to .dvr-ms Format, or use the \Windows\ehome\WTVConverter.exe utility at the command line for batch operations.
The ability to access .wtv files depends on the copy protection policy set by the content owner and/or broadcaster. Windows Media Center determines the copy protection policy by reading the broadcaster's copy protection flag (CGMS-A). If the content owner and/or broadcaster has set the policy to protect the content, playback is restricted to the Windows Media Center PC used to record the content.
For information about playing and editing .wtv files in DirectShow, see Consumption of a WTV file in DirectShow on the MSDN web site.