[Asterisk-Dev] A pipe length tester for TDM400 cards

Kris Boutilier Kris.Boutilier at scrd.bc.ca
Fri Jun 17 14:43:38 MST 2005

> -----Original Message-----
> From: Steve Underwood [mailto:steveu at coppice.org]
> Sent: Friday, May 13, 2005 11:48 AM
> To: Asterisk Developers Mailing List
> Subject: [Asterisk-Dev] A pipe length tester for TDM400 cards
> Hi,
> I finally put together a simple program for testing what happens to the 
> pipe length out from software, through a TDM400 card, and back to 
> software again. I haven't done much with it yet, or really studied in 
> depth if there are pitfalls in what I have done. However, you 
> can grab 
> the current source from ftp://ftp.soft-switch.org/pub/sliptest.c, and 
> compile it with
>     gcc sliptest.c -lspandsp
> (which, obviously, means you need spandsp installed). When you run it, 
> you need to give it a parameter which is the channel number of a circuit 
> on a TDM400 card. Don't have anything plugged into the card. The 
> software listens to the echo of what it sends. When it runs, it lists 50 
> loop lengths per second. The loop lengths are measured in audio samples.

Steve, how plausible would it be to modify this code to run against Asterisk itself, to be able measure the effective endpath of an established channel? Ie. a call that has been placed (ast)<-[zap/PRI]->(pbx)<-(analog)->(handset). 

I have some digital cordless phones on my network and they're producing an acoustic echo inside the handset the tail length of which, presumably due to the cordless aspect, is longer than the 64ms hardware echo canceller I'm using between Asterisk and the PBX. What I'm thinking is that your model would allow me to measure conclusively how long the actual endpath is and thus be able to size a replacement echo canceller accordingly.

Any thoughts?

Kris Boutilier
Information Services Coordinator
Sunshine Coast Regional District

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