[Asterisk-Users] GSM v iLBC for low bandwidth connections

[Andrew Kohlsmith]

> I've been playing with GSM and iLBC over low bandwidth connections
> (central Asterisk box with 2mbps, to ADSL users on 512/256) and both
> seem to perform well. Based upon what I've read in the archives and
> at voip-info.org iLBC should perform a little better if packets are
> lost, than compared to GSM. Do you find this to be true in practice,
> or is GSM just as robust?

I believe that iLBC has better MOS in lossy environments than all other 
protocols, period.  I use it exclusively now with the VOIP providers I use 
for LD.

> Whilst I'm asking questions, in terms of sound quality would there be
> a significant benefit in switching to g.729?

I have had *zero* voice quality issues with iLBC.  I have had voice quality 
issues due to links that were full, but that's not iLBC's fault.  The only 
reason I can see using g.729 these days is for low-bandwidth interoperability 
with commercial VOIP equipment that doesn't use iLBC.  Seriously.  The 
difference between 11-13kbps for an iLBC conversation vs 8kbps for g.729 is 
negligable to me.  Maybe if you had a thousand calls pumping out your 
connection, but then again the $10k you spent on g.729 licenses can probably 
buy a slightly faster link.  :-)

Regards,
Andrew