[cisco-voip] Codecs

[Ryan Ratliff]

All you ever needed to know about codecs (doc id 7934):
http://www.cisco.com/en/US/tech/tk652/tk698/ 
technologies_tech_note09186a0080094ae2.shtml

Region configuration guide for CM 3.3(3):
http://www.cisco.com/en/US/products/sw/voicesw/ps556/ 
products_administration_guide_chapter09186a0080181a2c.html

To answer your questions in short g.729 is a low bandwidth codec.  If  
your calls between clusters are going over a WAN then that is why they  
are configured for g.729 vs g.711.

The parameter in CM that decides what codec to use is Region.  Since  
Regions are configured per Device Pool and not per device you can think  
of the Device Pool as being what decides the codec to be used for a  
call between any two given devices.

The next question I expect will be "what are locations used for then?".  
  See below.
http://www.cisco.com/en/US/products/sw/voicesw/ps556/ 
products_administration_guide_chapter09186a0080181a2b.html

Your calls to the PSTN going out as both g.729 and g.711 are probably  
hitting different route patterns that in turn send them out different  
gateways.  It's possible you are doing some kind of toll bypass that  
sends one of those calls over the wan to either the other CM cluster or  
directly to a gateway there.  You'll have to confirm this with whoever  
set up your CM.

-Ryan
On Jan 28, 2005, at 12:31 AM, Anthony Mendoza wrote:

> G711u vs. G729.
>
> I noticed G711u being used when I was doing a call between two  
> different
> handsets registered on 2 different clusters.  Is the G711u more
> efficient than G729 in terms of bandwidth vs. quality?  Also, an odd
> thing I noticed was when I hit 9 on one call (to get an outside line)  
> it
> used 729, and on another call (hitting 9) it used G711u.  Any ideas why
> that would be different on a call by call basis?
>
> Something I noticed is that the Trunk I have configured is in my
> "Location" for my local phones in our office.  Does this setting  
> control
> which codec is used when doing intercluster trunk calls?
>
> --
> Anthony Mendoza
>
>
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