[Asterisk-Users] Which Codec(s) to use..?

[Steven Critchfield]

On Thu, 2005-02-24 at 16:39 -0800, Richard J. Sears wrote:
> Hey Everyone,
> 
> I am playing around with my * box, and I have a few different phones
> hanging off it it right now.
> 
> I have a Cisco 7960 capable of g729, ulaw and alaw, I have a Cisco
> ATA186 with a Panasonic cordless phone attached to it, I have a Digum
> IAXy with a dumb analog phone attached to it, and I have a Linksys
> PAP2-NA with an AT&T 959 analog phone attached to it.
> 
> I also have several IAX2 connections, one to NuFone and one to another
> provider.
> 
> 
> My question revolves around which codec to use. I purchased 10 licenses
> of the g729 from Digum thinking it was the "best" since it costs money
> :-)
> 
> I have read the wiki on the codecs, but I did not find any real
> "practical" use suggestions, just info on the codecs and the bandwidth
> they used.
> 
> In several cases I am not worried about the bandwidth consumption as I
> control the connectivity (several phone are behind T1's or high speed
> DSL), one of the IAX connections is across my OC48, and several phones
> are sitting on my desktop on the lan connected to the * server.
> 
> So my question is this - if I am running g729, am I giving up quality
> for the sake of bandwidth conservation..? Should I use the codec that
> matches the greatest amount of bandwidth that I have available, or go
> with the codec that uses the least amount of bandwidth..?

g729 is the best for the least bandwidth. ulaw and alaw are PSTN quality
and lossless beyond the simple a/d conversion. 

The question is one of available bandwidth and number of concurrent
calls expected considered against other network traffic.

For instance, if you had just one phone call to transfer over that OC48
of yours and absolutely no other traffic was going to touch the line,
there wouldn't be a single codec to be ruled out. But on your DSL line
might start choking after 1 call if there is a large file transfer in
the small part of the DSL even while using g729.

So you just need to know what you can do to make sure your required
phone bandwidth isn 't encroached upon by other data and when necessary
compress your calls enough to make room for data.

-- 
Steven Critchfield <critch at basesys.com>