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Cisco Bug: CSCtb26941 - DSP: Echo cancellation tail changes mid-call, echo on single DSP channel

Last Modified

Feb 01, 2017

Products (1)

  • Cisco IOS

Known Affected Releases

12.4(11)T 12.4(15)T 12.4(22)T 12.4(25) 12.4(7)

Description (partial)

Symptoms: Intermittent echo on voice calls are experienced.  All calls 
through a particular DSP channel will experience echo.
   
Conditions: The symptom is observed when a DSP channel, or set of DSP 
channels, go into a bad state where they no longer cancel echo. The audio 
stream coming into the DSP will match exactly what is going out. This can be 
identified by the symptom that the echo-cancellation tail will vary during a 
call even when the tail is specified on the voice port. Values from 24ms to 
112ms have been observed for a single call which this issue occurs on. The  
<CmdBold>show call active voice echo-canceller summary<noCmdBold> command can 
be used to observe the echo cancellation tail, and the voice-port command 
<CmdBold>echo-cancel coverage<noCmdBold> can be used to statically set the echo
cancellation tail.
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Bug Details Include

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