MeetMe voice quality (echo)

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Aug 12th, 2010
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We have an old Cisco CallManager 4.1(3) cluster (pub and sub) that we use to run a multi-customer VOIP service.  We have a problem where one customer (Cisco phones are a T1 hop away from CM and PRI gateways) has echo during MeetMe conferences.  All parties hear it, including those at the customer site and those who are on the PSTN and who talk through a PRI gateway, then through a 1 Gbps switch network to CM.  This is the only situation where there has been an echo problem for a LOOOONG time, probably 4 years. I don't know right now how many participants are in the MeetMe conference.  All transcoding is done in CallManager.  Win2000 Pub and Sub have 2 GB of RAM, % RAM util runs at a steady 45%.  CPU, disk I/O. memory paging all look very healthy all the time.

The same customer site has no echo or voice quality problems during normal calls, even when their T1 connecting to the data center where CM and gateways are is pegged at 100% utilization.

Is that version of CallManager not good at echo-cancellation?  Should I be using hardware on the network for handling the transcoding of MeetMe conferences?


Matt Woodling

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Tracy Larson Thu, 08/12/2010 - 15:52
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Have you tried upgrading the firmware in the phones? Certain older versions had bugs similar to this.

matt.woodling Thu, 08/12/2010 - 22:08
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The bugs you're referring to were specific to MeetMe?  Our problem is happening only during MeetMe conferences and all participants hear the echo, even those who are on PSTN phones.

Tracy Larson Fri, 08/13/2010 - 05:24
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The bugs had to do with conferencing of any kind. We had a bug once when on speaker phone when calls came from anything except cell phones echo would appear. The bug we hit wasnt specific to the problem we had but upgrading the 50 phones' firmware took care of the issue. So if your problem is with MeetMe only, i am not saying the upgrade will cure your issue but I am saying that a bug can emcompass much more than what is stated in the actual bug ID.

matt.woodling Fri, 08/13/2010 - 08:59
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Thanks for the info, Tracy.  I'm starting to think this problem is caused by one or more of the conference participants having a significant acoustic echo problem.  Here are a couple of references describing the problem and possible causes:

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