[Asterisk-Users] Compare to Skype

[mgraves at mstvp.com]

> -------- Original Message --------
> 
> Skype uses iLBC codec, which has great jitter compensation.  IIRC, the
> newer SIP channels of * are supposed to have the same capabilities, but
> I have not tested.  I really do not like Skype (prefer FWD), but I must
> say, over satellite, etc, they provide quality..  All about the codec in
> this case..


Errr...no...this is wrong. 

Skype uses ISAC from Global IP Sound. iLBC is something different see
http://www.globalipsound.com/solutions/solutions_Codecs.php

One of the reasons Skype sounds good is that its a closed system and so
can leverage a wideband codec. Instead of the normal 8khz sample rate
it uses 16khz. That makes for clearer sound. Since ISAC is a
proprietary relative of iLBC its jitter compensation is also very good.

My understanding is that Asterisk cannot presently use any wideband
codecs as it is hard coded to the 8khz sample rate at its core.
Adapting Asterisk to wideband capability has been discussed but will be
a huge amount of work. Further, only if you know that the calls will
stay wideband end-to-end will the benefits of wideband be apparent.
That means no PSTN segments.

Michael Graves
mgraves at mstvp.com