[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. 
====================================================================== 
https://issues.asterisk.org/view.php?id=13562 
====================================================================== 
Reported By:                biohumanoid
Assigned To:                sruffell
====================================================================== 
Project:                    DAHDI-linux
Issue ID:                   13562
Category:                   dahdi (the module)
Reproducibility:            have not tried
Severity:                   feature
Priority:                   normal
Status:                     confirmed
====================================================================== 
Date Submitted:             2008-09-26 04:27 CDT
Last Modified:              2009-06-02 02:06 CDT
====================================================================== 
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.

====================================================================== 

---------------------------------------------------------------------- 
 (0105874) biohumanoid (reporter) - 2009-06-02 02:06
 https://issues.asterisk.org/view.php?id=13562#c105874 
---------------------------------------------------------------------- 
Is there any action on including TX HPF ?

I've just updated the patches on HPF (dated by 2009-06-02) for dahdi
2.2.0-rc4.

Now, HPF take action in dahdi_chan_write. So, it will process audio data
from userspace (from VoIP), and will not affect TDM to TDM data.

Please, read http://www.rowetel.com/blog/?p=33 article "Fun with Soft
Phones".
If you will call from VoIP to PSTN (using OSLEC) - you will hear the
problem, when you will say "pineapple".
I wonder, how do you call... HPEC isn't the only echo canceller (I think
it have HPF included)...

I haven't included a new feature in dahdi_echocan_features, but it should
be. 

Issue History 
Date Modified    Username       Field                    Change               
====================================================================== 
2009-06-02 02:06 biohumanoid    Note Added: 0105874                          
======================================================================