Symptoms
When you play a video in Windows Media Player on a computer that is running Windows MultiPoint Server 2011, Windows Media Player displays a black screen instead of the expected video.
Cause
This issue occurs because some systems and applications exhibit instability when lots of stations simultaneously redirect video for decoding by the graphics processing unit (GPU). The number of stations required to cause this issue depends on your graphics subsystem and on the video decoding capabilities of your hardware.
Resolution
To resolve this issue, install the update rollup that is described in the following Microsoft Knowledge Base article:
2626067 Update Rollup 1.1 for Windows MultiPoint Server 2011
Registry information
Important This section, method, or task contains steps that tell you how to modify the registry. However, serious problems might occur if you modify the registry incorrectly. Therefore, make sure that you follow these steps carefully. For added protection, back up the registry before you modify it. Then, you can restore the registry if a problem occurs. For more information about how to back up and restore the registry, click the following article number to view the article in the Microsoft Knowledge Base:
322756 How to back up and restore the registry in WindowsYou can control the maximum number of stations that have redirected video by editing the registry. To do this, follow these steps:
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Click Start
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Locate and then click the following registry subkey:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows MultiPoint Server\
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On the Edit menu, point to New, and then click DWORD (32-bit) Value.
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Type MaxRedirectedVideoPlaybackSessions, and then press ENTER.
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Right-click MaxRedirectedVideoPlaybackSessions, and then click Modify.
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In the Value data box, enter the maximum number of sessions for which you want redirected video playback, and then click OK.
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Exit Registry Editor.
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Restart the computer.
Notes
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The value that you enter depends on the capabilities of your CPU, on your graphics subsystem, and on the video usage pattern of station users.
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You may have to test several values to determine the best choice for your system. We do not recommend that you set the value to support more than 12 sessions.
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If the registry key is not set when you apply the update rollup, it will use a default value of 12. Before the update rollup is installed, the value is unlimited and may exceed DirectX capabilities.
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If the registry key is set to 0, no stations will redirect video to the GPU.
More Information
If you decide not to redirect video on some of your stations, the stability of applications such as Windows Media Player can still be improved, but at the cost of increasing the CPU load of the computer. This behavior may result in slower system performance.
Note This setting does not apply to websites that feature Flash video playback. For example, this setting does not apply to Youtube.
For more information about software update terminology, click the following article number to view the article in the Microsoft Knowledge Base:
824684 Description of the standard terminology that is used to describe Microsoft software updatesThe third-party products that this article discusses are manufactured by companies that are independent of Microsoft. Microsoft makes no warranty, implied or otherwise, about the performance or reliability of these products.
