SIP phone fun

Wanted a local dial in number that would ring on my laptop. Went with Pennytel as their untimed international calls (8c) sounded good. Getting it to work ended up being much harder than it should have and took $20 of landline calls to my DID number.

The basic problem was that my outgoing audio was not heard by a caller to my DID number. It wasn’t a port problem nor an audio hardware problem; the voicemail system could hear me fine, (determined after a lot of wasted calls).

Their tech support guy was responsive and I went through the process of trying a number of SIP clients (he preferred X-Lite) on a couple of XP computers with different audio hardware.

A couple of colleagues had the same problem under XP but one got it working on a hardware SIP phone. I tried a complete WinXP reinstall. No dice, even with a totally fresh install.
Finally had a breakthrough when I discovered it worked fine on my Win2K computers. This eliminated a local network/router/ISP problem.
I used Ethereal to capture packets during a test call; data was flowing in both directions. Sent the data to Pennytel and their tech support (Antony) came back with the solution; try with just the G711 ALaw codec enabled. I tried this in Bria and it came good. Seems something in XP breaks that codec when using it with Pennytel!  You’d think they would have known about this.

EDIT April 2009: Nearly 2 years later and I’ve been using Pennytel using my SPA3102 ATA. Now I’m wanting to have Bria available on my laptop again. I installed version 2.5, the very latest and again had outgoing audio problems on incoming PT calls.

Using settings->Audio Codecs I just left G711-alaw in there but it didn’t help. Then I checked the “when negotiating audio codecs, accept the first codec offered”. Its all good now.

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