SPA3102: Choppy audio and low volume and soft dialtone

Unanswered Question
May 24th, 2010

I have 2 SPA3102s in 2 different countries connected via Pennytel.    Here's my setup

Country A (9Mbps Cable Connection)

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Country B (256+128 DSL connection)

Observations:

1. (A) Line 1 calling (B) Line 1: (A) hears (B) clearly.   (B) occasionally hears choppy audio from (A)

2. (A) Line 1 calling (B) PSTN, initiates a PSTN call at (B): PSTN dial tone is very soft, almost inaudible.    (A) hears (B) but is very soft.   (B) hears (A) but is very soft or choppy.

So it seems that (B)'s downstream audio is at times choppy regardless of call origin.

Network Jitter Level for both SPAs set to High; Jitter Buffer Adjustment set to Up and Down.

Tried to change codec to G729a for less bandwidth for PSTN line but read somewhere that PSTN calls always revert to G711, which it did. (then why allow me to change the codec...).

Appreciate any help...

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Alberto Montilla Wed, 05/26/2010 - 16:21

Dear Sir;

Make sure you use FW version 5.1.7 (available in cisco.com). Then if you are using VoIP, make sure you use G.729. This looks like a bandwidth issue, remember there is no quality of service over plain Internet.

Regards
Alberto

fcyy_cisco Thu, 05/27/2010 - 06:57

Hi Alberto,

Thanks for your reply and advice.   Isn't FW 5.1.7 an older firmware version?   Both my ATAs are using 5.1.10.    Is the older firmware version recommended over the newer one?   any particular reason why?

thanks

Alberto Montilla Tue, 06/01/2010 - 03:47

There is a bug related to codec handling on 5.1.10 which is not present in 5.1.7, would like to make sure this issue is not related to it.

regards

Alberto

fcyy_cisco Wed, 06/02/2010 - 07:42

Hi Alberto,

Thanks for your reply.   One thing puzzles me. Perhaps you could shed some light on it: in the country with the slow 256/128 connection, if it was really a bandwidth issue, I would expect the reverse.   That is, I should be hearing choppy audio from the other party, since the other party's upstream speed is only 128K.   Instead it is them who hears choppy audio from me, which presumably would be less likely considering their downstream is 256K.   I am puzzled as to why I hear them clearly when the upstream is slower than the downstream.

I wish there was a more deterministic way of troubleshooting this, instead of just fiddling with settings and seeing what happens after.   Like (and am guessing here) if the reason I'm getting choppy audio is that the audio packets at the other end is receiving packets too out of order, will there be a way to test that?   I would much prefer knowing what the probable causes are for a given symptom, then use some tool to test for that.   Does Cisco have some kind of analyzer tool or a more exhaustive troubleshooting guide?

Thanks

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