[Asterisk-Users] Codec audio quality comparisons?

[Jeff Heath]

The quality measurement you're looking for is Mean Opinion Score (MOS). 
It's an ITU standard for measuring call clarity.  Google codec MOS and
one of the first links to come up will be a Cisco technical note.  It's
not a comprehensive list, but it's pretty good.  

MOS is a scale from 1 to 5 with 5 being the best.  Really, the scale is
1 to 4.5 (but that's a long explanation).  Here are some codec MOS
scores:

codec	MOS	delay (msec)
G.711	4.1	0.75
G.729	3.92	10

the difference between 4.1 and 3.92 is significant and so is the 10 msec
delay.  

Jeff Heath


On Thu, 2005-03-31 at 02:04, Scott Bussinger wrote:
> I've seen lots of comparisons between the various codecs with respect to
> bandwidth requirements, but are there any comparisons with respect to
> quality?
> 
> I'm currently using ulaw internally and gsm to connect to my ITSP, but
> should I be using different codecs to get better sound? Could someone who's
> played with all of them rank them in order of quality or point me to
> somewhere that's got a comprehensive comparison?
> 
> For example, is it worth paying money for g.729 licenses for my users?
> Should I be hounding my ITSP to support SPEEX? Is g.711 absolutely the best
> possible sound given the bandwidth it uses?
> 
> Just to be clear, I'm calling highest quality the least noise and hiss,
> fewest sound anomolies, least echo effects, and least delay.
> 
> Thanks!
> 
> 
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