[asterisk-bugs] [DAHDI-linux 0013562]: [patch] It's necessary to have low frequency filter for tx signal of DAHDI.

[Asterisk Bug Tracker]

A NOTE has been added to this issue. 
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http://bugs.digium.com/view.php?id=13562 
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Reported By:                biohumanoid
Assigned To:                
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Project:                    DAHDI-linux
Issue ID:                   13562
Category:                   dahdi (the module)
Reproducibility:            have not tried
Severity:                   feature
Priority:                   normal
Status:                     feedback
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Date Submitted:             2008-09-26 04:27 CDT
Last Modified:              2009-02-03 01:40 CST
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Summary:                    [patch] It's necessary to have low frequency filter
for tx signal of DAHDI.
Description: 
It's necessary to have low frequency filter for tx signal of DAHDI. 
Otherwise, low-frequency signal from IP can reach a leased line, and
return back with nonlinear distortions. This will break an echo canceller.

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 (0099319) biohumanoid (reporter) - 2009-02-03 01:40
 http://bugs.digium.com/view.php?id=13562#c99319 
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>Pinging original reporter.
Pong :-)

> Why would this be more appropriately done in the kernel as opposed to in
user space? Does the echo canceler state play into the high pass filter in
any way?

Ofcourse, The best place for HPF is user-space chan_zap (chan_dahdi).
But, what if you use hardware EC ? Maybe it already has HPF inside ?
In this case, we need one more flag for chan_dahdi (hpf=some_thresh_value
or hpf=off/on). 

Taking into account zaptel/asterisk have a lots of openned bugs, I think
so "BIG" asterisk patch will never be included.
So, I've made a "small" patch for zaptel.

If you will include HPF on RX/TX in chan_dahdi - I'll be more than just
happy. 

Issue History 
Date Modified    Username       Field                    Change               
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2009-02-03 01:40 biohumanoid    Note Added: 0099319                          
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