[asterisk-users] Echo cancellation on DAHDI

[Vinícius Fontes]

----- "DHAVAL INDRODIYA" <dhaval.it01034 at gmail.com> escreveu:

> Hi,
> 
> Carlos
> 
> I checked dmesg on my server and i found following message
> 
> what is meaning for this ? i cant understand
> 
> VPM400: Not Present
> VPM450: echo cancellation for 128 channels
> VPM450: hardware DTMF disabled.
> VPM450: Present and operational servicing 4 span(s)
> 
> regards
> Dhaval

That means you have a VPM450 echo cancelling module attached to your digital board. All you need to do in order to activate echo cancelling is setting echocancel=yes on your chan_dahdi.conf.

After that you can check if the echo canceller is really enabled by triggering a "dahdi show channel X" on the Asterisk CLI. X should be a channel that's currently on a call. Here's an example:

stara*CLI> dahdi show channel 64
Channel: 64
File Descriptor: 77
Span: 3LI> 
Extension: 
Dialing: no
Context: pabx
Caller ID: 
Calling TON: 0
Caller ID name: 
Destroy: 0
InAlarm: 0 
Signalling Type: ISDN PRI
Radio: 0I> 
Owner: DAHDI/64-1
Real: DAHDI/64-1
Callwait: <None>
Threeway: <None>
Confno: -1
Propagated Conference: -1
Real in conference: 0
DSP: yes
Relax DTMF: no
Dialing/CallwaitCAS: 0/0
Default law: alaw
Fax Handled: no
Pulse phone: no
Echo Cancellation: 128 taps unless TDM bridged, currently ON
PRI Flags: Call 
PRI Logical Span: Implicit
Actual Confinfo: Num/0, Mode/0x0000
Actual Confmute: No
Hookstate (FXS only): Onhook


Of course, the interesting line to you is the "Echo Cancellation" one.