[asterisk-users] Improve voice quality on Asterisk + chan_capi + DIVA BRI

[Armin Schindler]

On Thu, 19 Apr 2007, Cosmin Prund wrote:
> Hello everyone!
> 
> I've got a Eicon Diva Server BRI card into my "*" box working just fine,
> but I wander if there's anything I can do to improve voice quality for
> my operators. I'm thinking something along the lines of "auto gain" and
> sudden noise suppression (like when you hit a fax machine or the other
> party accidently touches the dial pad on the phone).
> 
> Does one of Asterisk, chan_capi or the Diva driver have support for such
> functionality?

Sure, with the Dialogic (Eicon) DIVA Server card DSPs, you have the 
following possibilities:

1. Automatic Gain Control and Active Talker Evaluation in conference (by 
   default automatically activated with three or more parties)
2. Recording Stream Automatic Gain Control
3. Manual Control of Signal Level
4. Manual control of the signal pitch and/or bitrate (rate conversion)
5. Suppression of DTMF tones. This feature can be activated using adapter 
   configuration (for all calls) or on per call basis
   This is always good to activate this feature for operators to protect
   people from signals or in one gateway to prevent DTMF tones from passing 
   through gateway in band.
   The DTMF tones are suppressed in the way which will not affect the 
   quality of the voice signal in case voice signal and DTMF tones overlap.
6. Part 68 Voice Signal Limiter (Required in US, by default deactivated in 
   Europe). This protects the ears from "clicks" and too loud signals. This 
   feature can be activated using the configuration. This is good idea to 
   activate Part 68 voice signal limiter to protect the people. This is the 
   dynamic voice signal limiter in accordance with Part 68 of US 
   requirements.

The Part 68 Limiter, Audio Recording Automatic Gain Control (AGC of
received signal) and the DTMF Clamping (Suppression of DTMF tones) are
can be controlled using adapter configuration and do not require any
change in the application (but can be controlled on the per call basis
too, which is not implemented in chan-capi yet).


Armin