PBX extension 100 available codecs
G.711 u-law
G729
Phone SPA942 latest firmware 6.1.5(a)
G729
G711 u-law
all in and out calls will fail. it will not negitiate down the list of available codecs.
Yes, sure will fail. That because asterisk will negotiate G.711 ulaw in the extension 100 call leg then will negotiate G.729 in the SPA942 call leg, this require G.711<->G.729 trascoding so the call can't be established if G.729 is not available in asterisk.
The codec priority has been working long ago.
Elastix, Trixbox. PIAF can all do this.
Example is Asterisk 1.6.2.10, it works no problem.
Hard to believe, no configuration can change the core asterisk features... using the exact same codec priorities above the call will contitue to fail everytime G.729 isn't available. What you're asking for is a typical SIP proxy feature but unfortunately Asterisk does not implement a proxy.
Not convinced yet? Here is a quote from a Digium developer (Kevin P. Fleming):
You are looking for a SIP proxy; Asterisk is not a SIP proxy, and no
amount of configuration will convince it to act like one.
Asterisk never “sends along” re-INVITEs, because the two channels
involved in an Asterisk “call” are distinct. If the codecs are
mismatched between the two call legs, Asterisk will try to transcode them.
The ‘directrtpsetup’ feature is still marked *experimental*, and that is
primarily because it defeats much of Asterisk’s normal behavior; in
addition, there a quite a few normal, working call scenarios for which
it will fail… so it’s there, but if you use it, you can expect
difficulties.