You randomly hear audio from another terminal server session when you play audio in a terminal server session that is hosted on server that is running Windows Server 2008

Consider the following scenario:

• On a server that is running Windows Server 2008, you install the Terminal Services server role.
• On this server, you enabled the audio redirection feature.
• Users create terminal server sessions to this server.
• Users play audio or video in these terminal server sessions.

In this scenario, a user may randomly hear audio that is being played in another terminal server session when the server is under heavy stress.

This issue occurs because of a race condition in the Remote Desktop Protocol (RDP) audio endpoint module (Rdpendp.dll).

Before the RDP audio endpoint module sends audio, the module converts the audio into a different format to save bandwidth. A temporary buffer is used to compress the audio. However, all terminal server sessions share this temporary buffer. Therefore, the temporary buffer may be written to by multiple terminal server sessions at the same time.

For example, terminal server session 1 and terminal server session 2 compress audio at the same time. Session 1 fills the buffer, and then session 2 overwrites the buffer before the compressed audio is sent out. Therefore, session 1 may hear the audio from session 2.

Note Most of the time, the RDP audio endpoint module can compress the audio, and then send it before another session overwrites the buffer. However, as the system load increases, this problem occurs more frequently.

Hotfix information

A supported hotfix is available from Microsoft. However, this hotfix is intended to correct only the problem that is described in this article. Apply this hotfix only to systems that are experiencing the problem described in this article. This hotfix might receive additional testing. Therefore, if you are not severely affected by this problem, we recommend that you wait for the next software update that contains this hotfix.

If the hotfix is available for download, there is a "Hotfix download available" section at the top of this Knowledge Base article. If this section does not appear, contact Microsoft Customer Service and Support to obtain the hotfix.

Note If additional issues occur or if any troubleshooting is required, you might have to create a separate service request. The usual support costs will apply to additional support questions and issues that do not qualify for this specific hotfix. For a complete list of Microsoft Customer Service and Support telephone numbers or to create a separate service request, visit the following Microsoft Web site: Note The "Hotfix download available" form displays the languages for which the hotfix is available. If you do not see your language, it is because a hotfix is not available for that language.

Important Windows Vista and Windows Server 2008 hotfixes are included in the same packages. However, only one of these products may be listed on the Hotfix Request page. To request the hotfix package that applies to both Windows Vista and Windows Server 2008, just select the product that is listed on the page.

Prerequisites

To apply this hotfix, the computer must be running one of the following operating systems:

• Windows Server 2008
• Windows Server 2008 Service Pack 2 (SP2)

Additionally, the computer must have the Terminal Services server role installed.

Restart requirement

You do not have to restart the computer after you apply this hotfix.

Registry information

To use one of the hotfixes in this package, you do not have to make any changes to the registry.

File information

The English version of this hotfix has the file attributes (or later file attributes) that are listed in the following table. The dates and times for these files are listed in Coordinated Universal Time (UTC). When you view the file information, it is converted to local time. To find the difference between UTC and local time, use the Time Zone tab in the Date and Time item in Control Panel.

Windows Server 2008 file information note

• The MANIFEST files (.manifest) and the MUM files (.mum) that are installed for each environment are listed separately. MUM and MANIFEST files, and the associated security catalog (.cat) files, are critical to maintaining the state of the updated component. The security catalog files (attributes not listed) are signed with a Microsoft digital signature.

For all supported x86-based versions of Windows Server 2008

For all supported x86-based versions of Windows Server 2008 SP2

For all supported x64-based versions of Windows Server 2008

For all supported x64-based versions of Windows Server 2008 SP2

Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.

Additional file information for Windows Server 2008

Additional files for all supported x86-based versions of Windows Server 2008

Additional files for all supported x64-based versions of Windows Server 2008