Quote:
Oslec is an open source high performance line echo canceller. When used with Asterisk it works well on lines where the built-in Zaptel echo canceller fails. No tweaks like rxgain/txgain or fxotrain are required. Oslec is supplied as GPL licensed C source code and is free as in speech.
It seems like many Asterisk users have problems with echo, particularly on PSTN lines brought into the Asterisk box. I’ve even heard severe echo problems when using some commercial VoIP services (thankfully not recently, but in the early days of commercial VoIP, echo was a problem that had to be dealt with).
The big players tend to use hardware interface cards that have built-in hardware echo cancellation, but for the home or very small business user, those cards can be a bit pricey. OSLEC is a software solution that works very well, or so I’ve read, and it’s open source. The downside is that you have to be familiar enough with Linux to download, build, and install OSLEC, following the instructions on this page. It doesn’t look difficult (and bear in mind that Linux and I sometimes don’t get along very well, so if it doesn’t look hard to me, it’s probably a piece of cake to anyone who feels even slightly at home in a Linux environment).
Trixbox users can find installation instructions by going to this Trixbox forum page and scrolling down to the post by kerryg dated Thu, 07/19/2007 – 3:26pm, and the messages following that one. It appears that while it did not work for everyone who tried it (at least not on the first attempt), those who did get it to work are quite happy with the result.
Edit: If you have one or more Digium analog cards, you might prefer to use Digium’s High Performance Echo Canceler (HPEC) – see the first comment on this post for more information.
roderickm said
Digium’s High Performance Echo Canceler (HPEC) is available free of charge to customers of Digium analog cards. It’s the same algorithm used in the hardware echo canceler, only in software run on the host’s CPU. It’s not open sourced because it’s licensed from the patent holder, but the algorithm is G.168 compliant and sounds great. Check the HPEC README for more info: http://downloads.digium.com/pub/telephony/hpec/README
michigantelephone said
roderickm: The second paragraph in the README states:
I would assume that most people running non-Digium cards would probably prefer not to have to pay a per-channel fee to Digium in order to use their echo canceler, especially since that fee doesn’t entitle them to any support. Having said that, for those who have purchased one or more Digium cards, HPEC might indeed be a better option, so thank you for bringing it to our attention.
SureTeq’s Asterisk/Trixbox Blog » The wonders of echo cancellation troubleshooting « Michigan Telephone, VoIP and Broadband blog said
[...] Elastix, FreePBX, OSLEC, PBX in a Flash, Trixbox, VoIP In a previous post I mentioned OSLEC, the open source high performance line echo canceller. But if that wasn’t enough to make [...]
Trixbox CE 2.4 released « Michigan Telephone, VoIP and Broadband blog said
[...] is great – I have written about OSLEC in a previous post, and I’m happy to see that it’s starting to be used in various products including [...]
Luis Perez said
But what can you do when the echo is between the Asterisk and the VoIP phone (for example Polycom 330 or 550)?
We have had several clients where the connection between the Asterisk and the VoIP phone had echos. The PSTN user never hears the echo.
Thank you in advance.