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Voice Quality Issue ,,

Hello colleagues,

This is maybe the weirdest issue I ever dealt with ,

so we are an enterprise that has more than 10 branches "small ones" most of them connected with an E1 link .

all branches use the same one gateway that is connected to the PSTN with an E1 PRI link . anyway my problem is that only one branch and not any other, face a voice quality issue that is when an ip phone user at that particular branch initiates a call to the  PSTN the PSTN phone hears the IP phone user but the IP phone user cant hear more than some noise.  note that if the user recieves a call from PSTN voice works two-way with no issues.

Thanks For your time

2 REPLIES
Cisco Employee

Voice Quality Issue ,,

This sounds like Inbound and Outbound calls from Branch to PSTN are taking different paths. An outout "Show voip RTP connection" and "Show voice call stat" from PSTN GW for both working (PSTN Inbound) and Non-working (PSTN Inbound) should be good to start with.

Also, please share the running confguration.

- Basant

Voice Quality Issue ,,

Hi Yaarub,

Are the IP Phones registered to CUCM or CME ?

What is the exact call flow ? (include all devices in the path) for eg: IP Phone -- CUCM -- H323 / MGCP / SIP -- GW - PSTN

Is the issue intermittent ? or happens with each and every call.

What changed from software / hardware perspective before the issue occurred ?

You can get a PCM capture to quickly check if the inbound audio from PSTN is fine. The below link details about the PCM capture procedures

http://www.cisco.com/c/en/us/support/docs/voice/h323/116078-technologies-technote-commandreference-00.html#anc8

You would get a .dat file. You will have to decode this file and thre will be three streams.

"sin" contains audio received from the PSTN going towards IP, before the DSP does any processing.

"sout" contains audio received from the PSTN going towards IP, after the DSP processes the audio. Things like echo cancellation and input gain adjustments are visible here.

"rin" contains audio received from IP going towards the PSTN.

You can open a TAC case to get the capture decoded and analyzed or use any online tool (I'm not very sure if there's one). In TAC we use an internal tool.

Regards,

Gagarin

Regards, Gagarin Please rate all helpful posts.
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