Hi, I had this same problem and I don't think it is related to mod_callcenter. I had also sent a post in regards to this here: http://lists.freeswitch.org/pipermail/freeswitch-users/2012-July/085552.html I figured that this generally happened when my caller leg was connected on G711ulaw and agent leg was connected on G722 codec. When both the caller leg and agent leg was same the recordings were clear. Can someone please confirm if this could be the problem !! --- Jayesh

Sounds like network connection. Can you try switching stations between a

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bad phone and a good phone. Maybe your network has bad ports or cables somewhere. I know for all cisco voip they recommend cat 6 cables.

It is definatelly not a network problem. The clients are connected to the same switch. I posted the log to see the difference. Observe "codec substitution" lines for bad clients. I don't know what this means to the system as why a substitution is done, but are not tried other codecs from client to compare.