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Audio quality decreases during a conference call that is hosted on a Communications Server 2007 Audio/Video Conferencing Server when Communications Server 2007 clients report packet loss

Article ID: 957648 - View products that this article applies to.

SYMPTOMS

When one or more Microsoft Office Communications Server 2007 clients report packet loss, audio quality decreases during a conference call that is hosted on a Communications Server 2007 Audio/Video Conferencing Server.

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CAUSE

This problem occurs when the Forward Error Correction mechanism is turned on because of the audio packet loss. This causes corruption of the contributing source (CSRC) list. The CSRC list is used in the Communications Server 2007 Audio/Video Conferencing Server to mix the active speech sources in the conference. A corrupted CSRC list affects the audio mixing process and the overall quality of the audio in the conference call.

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RESOLUTION

To resolve this issue, follow these steps:

Install the update package for Communications Server 2007 Mediation Server that is described in the following Microsoft Knowledge Base article:
956829
(http://support.microsoft.com/kb/956829/ )
Description of the update package for Communications Server 2007 Mediation Server: October, 2008
Install the update package for Communications Server 2007 that is described in the following Microsoft Knowledge Base article on computers that have the A/V Conferencing Server role installed:
956831
(http://support.microsoft.com/kb/956831/ )
Description of the update package for Communications Server 2007 A/V Conferencing Server: October, 2008
Install the Live Meeting 2007 client update package that is described in the following Microsoft Knowledge Base article:
957491
(http://support.microsoft.com/kb/957491/ )
Description of the Windows-based Live Meeting 2007 client update package: October 10, 2008

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STATUS

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

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MORE INFORMATION

For more information about the components, about the protocol, and about the architecture of Communications Server, download the technical document on the following Microsoft Web site:

http://www.microsoft.com/downloads/details.aspx?familyid=959cb709-d81e-4dde-821f-0411dfcfc073

(http://www.microsoft.com/downloads/details.aspx?familyid=959cb709-d81e-4dde-821f-0411dfcfc073)

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