Date: Thu, 8 Nov 2007 22:43:47 +0100 From: Hans Petter Selasky <hselasky@c2i.net> To: freebsd-isdn@freebsd.org Subject: Re: echo cancellation / suppression in chan_capi & isdn4bsd by HPS Message-ID: <200711082243.48348.hselasky@c2i.net> In-Reply-To: <d3dd0e360711070747xa3a77faw1c7cb8656fc796da@mail.gmail.com> References: <d3dd0e360711070747xa3a77faw1c7cb8656fc796da@mail.gmail.com>
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Hi Michael, On Wednesday 07 November 2007, Michael Iedema wrote: > Greetings everyone, > > I'm trying to understand what options are available to me regarding > echo cancellation and suppression in chan_capi and isdn4bsd from HPS > (http://www.turbocat.net/~hselasky/isdn4bsd/). > > Great software, just trying to understand it a bit more thoroughly. > > In the chan_capi code, I see references to: > - echo cancellation in hardware > - echo cancellation in software > - echo suppression in software > > I understand the chan_capi options to mean: > - echocancel - activates hardware echo cancellation if it is > available or software echo cancellation in the i4b driver if it is > not. > - echosquelch - activates some "light" echo cancellation in the > chan_capi code itself The "echocancelold" can just be ignored. It is not used within I4B. > - echocancelold - must be activated for older cards not supporting the > new echo cancellation method > - echotail - echo can tap count > > Here's what I'm still not clear on: > - What do the g164, g165 and force options cause on the "echocancel" line? Try google. Setting these does not affect anything currently. > - Are the echocancel/echosquelch options smart enough to only be > activated if the "better" of the two is already activated? No. > - Is there a way to tell if a card needs "echocancelold" to be set? You don't need to set it. > - What is the value range for "echotail"? (32, 64, 128, 256?) Currently has no effect. It should set the number of samples or milliseconds that the echo cancel filter should cover. --HPS
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