[AsteriskBrasil] Fwd: [asterisk-users] FXOTUNE update

[Denis Galvão]

Para quem usa FXO.
--
Denis Galvão
AsteriskBrasil.org

Ajude a comunidade AsteriskBrasil.org, compre uma camiseta!
http://www.voipmania.com.br


Begin forwarded message:

> From: Matthew Fredrickson <creslin em digium.com>
> Date: 09 de janeiro de 2008 21h28min41s GMT-02:00
> To: Asterisk Users Mailing List - Non-Commercial Discussion  
> <asterisk-users em lists.digium.com>
> Subject: [asterisk-users] FXOTUNE update
> Reply-To: Asterisk Users Mailing List - Non-Commercial Discussion  
> <asterisk-users em lists.digium.com>
>
> Hey all,
>
>
> First of all, some background:
>
> Fxotune is a utility that is used to tune the hybrid on FXO modules
> For all of you with FXO modules out there, fxotune can help you adjust
> the analog and digital hybrid that is on the FXO interface and tune it
> so that it maximizes echo return loss.  This means that it will reduce
> your default echo which is received, and will help any echo cancellers
> on the line to do a better job.  If using one of the open source
> software echo cancellers, using fxotune can be the difference between
> having echo problems and not having echo problems.
>
> This is the update:
>
> I just committed a new version of fxotune which uses a better  
> technique
> for measuring echo return loss.  Before, there was a simple power
> calculation which was done on the samples that would indiscriminately
> check the power of all samples received.  This works well when the  
> line
> is silent, but if there are any sort of tones in the background or  
> noise
> due to noisy line conditions, this calculation can yield results which
> may improve things, but are not the best results.
>
> The new method involves using fourier analysis of the tones used in  
> the
> test reference which is sent out.  Using fourier analysis instead  
> of the
> power calculation, we can cut through any background noise which is  
> not
> related to our test sequence's set of tones, producing a much more
> accurate and noise immune calculation.
>
> If you have run fxotune before on your lines, I recommend you re- 
> run it
> with the updated version of the utility.  As of this moment, it is not
> yet in a released version of zaptel, but if you check out either  
> latest
> 1.2 or 1.4 branches, it will be there.  If you run fxotune with the -v
> option, it will tell you what the return loss it calculates for  
> each AC
> impedance and set of coefficient parameters in dB.
>
> In order to use the new analysis calculations, you do not need to pass
> any sort of special parameters to fxotune, it does the new analysis
> technique by default.
>
> Please let me know if you have any issues as well.  Thanks!
>
> -- 
> Matthew Fredrickson
> Software/Firmware Engineer
> Digium, Inc.
>
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