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No audio when connected to Unity

Unanswered Question
Feb 10th, 2003
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Hello Cisco,

I have a question, Our customer is running Unity 3.1 Build 3.1(5) When connected to Unity I show a connection on the phone with no audio from the attendent. I checked port status and notice my connection. The features on my phone work normal with no problems. I'm able to leave a message also. Any suggestions would be appreciated. Thanks!

Brian DeLuca

Redrock Communications

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Overall Rating: 5 (1 ratings)
b.deluca Mon, 02/10/2003 - 15:43
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Here's an update while I'm connected to Unity I noticed on the call statistics I have a TxCnt but no RxCnt. Thanks!


b.deluca Wed, 02/12/2003 - 10:52
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Hello Cisco,

I wanted to inform you the problem was When Cisco Unity transcodes wave formats, it uses Microsoft Windows ACM (Audio Compression

Manager) to call into the third-party G.729a codec. When multiple threads call into the Windows ACM

function AcmStreamConvert() at the same time, they can conflict with one another and generate errors,

causing callers to hear dead air or the reorder tone. Restarting the Cisco Unity server clears the

corruption in Windows ACM temporarily, but it does not prevent the problem from reoccurring.

An application-level workaround, an optional registry setting, makes Windows ACM globally

thread-safe. To enable the registry setting, do the procedure, To enable the

ForceGlobalAcmThreadSafety registry setting.

A good indication are errors logged in the Application log in the Event Viewer listing Component Miu: Thread 0x had a Failure on Port X in AvWav.

Thanks again for your help!

Brian DeLuca

Redrock Communications

Las Vegas

kechambe Wed, 02/12/2003 - 11:16
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Yeah there is a defect in 3.1(5) where ACM thread safety is disabled:


There was a field alert on it a while back:


It's fixed and will be in 3.1(6) code. Also in 3.1(6) and 4.0(1) we move to a new g.729a codec all together which adds stability.



kechambe Mon, 02/10/2003 - 16:55
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This is most likely a routing issue of some sort. The voice is transported using RTP/UDP. Since it is not connect oriented it is possible to have one-way voice. Do you have a router between the phone and Unity? Do all phones have the problem? Can you ping the phone from Unity?

A sniffer trace is your best tool to get to the root of these types of issues.

Hope that helps,



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