i've used it in the past. I never got oslec to work right. first it didnt load the modules without error. Then when i did get it to load, it wouldn't unload the module. I had to reboot the box just to get the dahdi modules to release.

I ran it on a TDM400 when the hpec first came out. Worked fine till i was given a beta TDM800 with echo cancellation card.

p.s. oslec only does 32ms (128 taps), but hpec can do as much as 1024 taps.

just make sure you have enough cpu power to do it.

I've also tried Octasic a very long time ago, but it kept on locking up my system. The company acknowledged the problem but by the time they got around to fixing it, I had already written them off and moved on to something else. I don't know anyone who's tried it.
FSD

Octasic is who licensed HPEC to digium. Its also the software on the 2 port and 4 port PRI hardware echo cancellation modules. IMO the octasic echo can modules vastly out perform the others.

There are several solutions for server side echo cancellations that supports more than 1024 taps. Some are HW based (like VQA from Ditech) and others are software based (like PBXMate from SoliCall).

I think more than 1024 taps would be way too annoying since the audio is delayed in order to cancel out the echo. 1024 taps is 128ms. You start introducing more delay than that and its going to sound like a satellite call where you keep stepping on each other as they are talking.

When different VoIP networks are connecting there is usually a delay of few hundred ms - depending on the quality of the networks and the connection between them. The above mentioned products simply help you get rid of echo that is very disturbing in these scenarios. They DO NOT add delay.

this sounds like snakeoil to me, chan_dahdi.so is the only module that uses echo cancellation. Now you are making suggested claims that it will magically remove echo on a voip call between peers when chan_sip.so has no hooks for echo cancellation. Do you have any sort of capture analysis that proves that not only do the modules customize chan_sip.so but also has an effect on echo?

technically speaking you cant even get echo on a purely voip connection anyway.. as there is a different path for sending and receiving, the two never ride the same copper the way 2-wire analog does. About the only sort of echo you can get over pure voip is acoustical echo. I am assuming you are actually referring to a scenario of

local voip -> pstn -> pstn -> local voip

I am talking about external product (not part of the PBX). So NO CHANGE is made to the PBX and its internal components like the chan_sip.so.

The audio is streaming via these products and they take care of the echo cancellation.

And yes, in VoIP the problem is usually acoustic echo.

so from a ballpark price standpoint what sort of investment price are we talking for this media gateway?

I have no idea. Neither of them publish prices on their sites.

that usually means 50K-60K

I have just seen that SoliCall has released a personal version of their enterprise level PBXMate. This sounds like an interesting entry level solution for audio quality improvement.