A while back, I posted an item on the Media Center Sandbox blog that described how to directly launch Windows Media Center and have it navigate to a specific experience using some command line parameters available within the Windows Media Center Shell application.  Since then, several folks have asked me about those command line parameters and whether there were more.

The specific problem that most people noted was that the command line ehshell.exe /directmedia:tv navigates to the Recorded TV gallery and not to Live TV.  Unfortunately, there is not a command line parameter that allows direct navigation to Live TV.

However, there is another mechanism that can be used to launch Windows Media Center and browse to a specific experience, including Live TV.  I'm going to describe the algorithm in words here:

1. Call the Win32 FindWindow API and pass in Media Center Tray Applet for the class name and NULL for the window name
2. If the FindWindow API returns NULL, display an error and exit
3. Call the Win32 RegisterWindowMessage API, pass in Media Center Navigate To Page and save the result
4. Call the Win32 SendMessageTimeout API and pass in the window returned in step 2, the message registered in step 3, and as the WPARAM and LPARAM, the desired values from the tables listed below
5. If the SendMessageTimeout API returns 0, the browse failed

WPARAM values to use for browsing

• WPARAM = 0: Windows Media Center Start Menu
• WPARAM = 1: Live TV
• WPARAM = 2: TV Guide
• WPARAM = 3: My TV
• WPARAM = 4: Recorded TV
• WPARAM = 5: My Music
• WPARAM = 6: My Photos
• WPARAM = 7: Scheduled Recordings
• WPARAM = 8: My Videos
• WPARAM = 9: Radio
• WPARAM = 12: Online Spotlight (this value is only availabe in Update Rollup 2 for Windows XP Media Center Edition 2005 and later)
• WPARAM = 13: Extensibility application (this value is only availabe in Update Rollup 2 for Windows XP Media Center Edition 2005 and later)

LPARAM values to use for browsing

• LPARAM = 0: Start Windows Media Center in the last used state (full-screen or windowed)
• LPARAM = 1: Start Windows Media Center full-screen

Notes:

This algorithm works regardless of whether the Windows Media Center UI is currently running. It also correctly handles bringing the Windows Media Center UI to the foreground.  This is the only officially supported method of browsing to the Windows Media Center UI from an external application.  This mechanism was first made available in Windows XP Media Center Edition 2004.

New values might be added to the WPARAM and LPARAM tables with new versions of Windows Media Center.

I've also created a sample Win32 application that implements the above algorithm.  You can find more information about that sample application and download the source code and the executable from this blog post.

<update date="1/14/2009"> Added a link to the sample application that I created to demonstrate how to implement this algorithm. </update>