I have by entering id=-1 in the codec page discovered that the only codecs working are pcma and pcmu, they happen to be the most data intensive codecs. Has anyone managed to use any others such as ilbc, for the record I am using pbxes.org, thanks

The Maemo client should normally also offer iLBC and G.729, what codecs are supported on the other side? See also bug 8609 for details on how to enable speex and some relevant discussion.