[asterisk-users] G.722 over ISDN PRI/BRI

[Matthew Fredrickson]

Simon Hyde wrote:
> Hi,
> 
> G.722 is heavily used by Broadcasters worldwide for wideband voice 
> communications over ISDN. I'd like to be able to receive these G.722 over ISDN 
> calls into an Asterisk exchange (with mostly a view to routing the calls to a 
> Voicemail box where material can be recorded). I have been examining source 
> code for the 3 different ISDN Channels in Asterisk and they all seem to be hard-
> codec to aLaw/uLaw G.711. It looks as though chan_capi *might* support bridging 
> of G.722 data from one ISDN port to another, but not routing to any other 
> source/transcoding/passing to voicemail.
> 
> So I guess my question is, am I correct in the belief that all Asterisk's ISDN 
> channels currently don't support anything other than G.711? How easy would it 
> be to extend one of the ISDN channels to support G.722?

Your belief is correct.  Right now, the ISDN channels (at least in 
chan_zap) G.711 is the only voice codec that is supported.  I'm not sure 
what is going to be necessary to get G.722 working there.  If it's as 
simple as changing the bearer capability, the chan_zap work on top of 
that should be fairly easy.

If you have to implement any of the H.* specs to get it working, that 
will be a bit more trouble.

-- 
Matthew Fredrickson
Software/Firmware Engineer
Digium, Inc.