[Freeswitch-users] Blog post about SIP

[Kristian Kielhofner]

On Sun, Jun 17, 2012 at 6:44 AM, Steve Underwood <steveu at coppice.org> wrote:
> I thought the only Cisco products which did this were the ones which
> started as Linksys/Sipura products. The usual G.729 problem with real
> Cisco products is G.729 with the bits packed in the opposite order to
> the RFC. This isn't an error. Cisco implemented G.729 in RTP before
> there was a standard, and the packing order they chose just happened to
> be the opposite of the standard. Of course, modern Cisco kit implements
> the standard order, but they can still do the opposite order for
> backwards compatibility with their own kit. Sometimes you still meet
> systems configured to use that, and G.729 calls produce a horrible noise.

You are generally correct, however, some of the rtmpap G729a craziness
seems to have moved to "Cisco proper".  I've seen IOS-powered media
gateways and CallManager express systems put G729a in the rtpmap. With
how much that hardware interacts with the current line of rebadged
Sipura/Linksys phones I can't say I'm completely surprised.

-- 
Kristian Kielhofner