[Asterisk-Dev] Asterisk / OpenH323 Bearer-Capability

[Michael Procter]

> From: Aaron S. Joyner [mailto:asjoyner at intrex.net]
> Craig Southeren wrote:
> >On Thu, 02 Sep 2004 16:36:48 -0400
> >"Aaron S. Joyner" <asjoyner at intrex.net> wrote:
> >
> >>I'm currently using Asterisk, and working with a provider 
> to setup an 
> >>H.323 gateway connection.  In the process of setting up the H.323 
> >>connection, Asterisk (via OpenH323) is sending the wrong 
> >>Bearer-Capability, as seen here in the output of a call, 
> with "h.323 
> >>trace 4" set.
> >>
> >>>      IE: Bearer-Capability = {
> >>>        80 90 a5                                           ...
> >>>      }
> >>>      
> >>>
> >>If I understand it correctly, this is stating that Asterisk 
> is capable 
> >>of handling more than just data - that OpenH323 is fully capable of 
> >>passing video codecs, etc.  Unfortunately, I need to reduce 
> what I'm 
> >>advertising that I'm capable of doing - as it's confusing 
> the remote 
> >>end.  In a perfect world, I need it to say "80 90 a2" or "80 90 a3".
> >>    
> >>
> >
[...]

> Apparently the last octet in the Bearer-Capability actually 
> defines the user information layer 1 protocol.  Strangely,
> the setting A5 would seem to indicate synchronous (bit 7),
> in-band negotiation (bit 6), 
> recommending G.722 or G.725 7kHz audio (bits 5-1, neither of 
> which are 
> supported by Asterisk, OpenH323, or the remote Cisco end 
> we're talking 

No - you have mis-decoded the final octet.  Sync and negotiation
are only present in octet 5a - but there is no octet 5a in this
element, only unextended octets 3, 4 and 5.

You are right that you want 80 90 A3 or 80 90 A2 (A-Law and u-law
respectively), although I would strongly favour A-law wherever
possible to improve interoperability.

Don't forget that you can download 3 ITU specs for free, by
registering your email address...

Michael