Cisco 8961 Administration Manual page 305

Troubleshooting and Maintenance
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No speech path
Problem
One or more people on a call do not hear any audio.
Solution
When at least one person in a call does not receive audio, IP connectivity between phones is not established.
Check the configuration of routers and switches to ensure that IP connectivity is properly configured.
Choppy speech
Problem
A user complains of choppy speech on a call.
Cause
There may be a mismatch in the jitter configuration.
Solution
Check the AvgJtr and the MaxJtr statistics. A large variance between these statistics might indicate a problem
with jitter on the network or periodic high rates of network activity.
Poor Audio Quality with Calls That Route Outside Cisco Unified Communications Manager
Problem
Poor quality occurs with tandem audio encoding. Tandem encoding can occur when calls are made between
an IP Phone and a digital cellular phone, when a conference bridge is used, or in situations where IP-to-IP
calls are partially routed across the PSTN.
Cause
In these cases, use of voice codecs such as G.729 and iLBC may result in poor voice quality.
Solution
Use the G.729 and iLBC codecs only when absolutely necessary.
Video distorted or pixilated on Cisco Unified IP Phone 9951
Problem
The video on the Cisco Unified IP Phone 9951 appears distorted or pixilated and the phone is using a
100-BaseT/full duplex connection.
Cisco Unified IP Phone 8961, 9951, and 9971 Administration Guide for Cisco Unified Communications Manager 10.0
Camera, audio, and video problems
(SIP)
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