A year ago I was musing over the fact that despite there being quite a number of phones today that can do SIP over Wi-Fi, non are Wide Band AMR capable for superior sound quality. Quite a waste as without network based transcoders between the two parties there's no legacy technology to overcome and implementation is straight forward. Looks like Nokia might have changed that without making a big fuss about it:
When I recently traced the Wi-Fi SIP interaction of my new Nokia E75 (for details how this is done see here), I noticed that it announces that it's WB-AMR capable in a SIP invite message. A closer look at Forum Nokia confirmed this. Unfortunately I am missing a counterpart to try it out with but that might just be a matter of time. While my SIP provider Sipgate puts a proxy in the speech path of every call, it is capable of different codecs, as I've seen both G.711 and AMR run over it. So with a bit of luck, WB-AMR might work as well. I'll keep you posted. In the meantime, here's the E75's Session Description part of the Invite message:
Session Initiation Protocol
Request-Line: INVITE sip:+xxxxxxxxxxxxx@sipgate.de SIP/2.0
Message Header
Message Body
Session Description Protocol
Session Description Protocol Version (v): 0
Owner/Creator, Session Id (o): xxxxx xxxxx xxxxx IN IP4 192.168.xxx.xxx
Session Name (s): –
Connection Information (c): IN IP4 192.168.xxx.xxx
Time Description, active time (t): 0 0
Media Description, name and address (m): audio 49152 RTP/AVP 100 96 0 8 97 18 98 13
Media Attribute (a): sendrecv
Media Attribute (a): rtpmap:100 AMR-WB/16000
Media Attribute (a): ptime:20
Media Attribute (a): maxptime:200
Media Attribute (a): fmtp:100 mode-change-period=2; mode-change-neighbor=1
Media Attribute (a): rtpmap:96 AMR/8000
Media Attribute (a): fmtp:96 mode-set=0,1,2,3,4,5,6,7; mode-change-neighbor=1
Media Attribute (a): rtpmap:0 PCMU/8000
Media Attribute (a): rtpmap:8 PCMA/8000
Media Attribute (a): rtpmap:97 iLBC/8000
Media Attribute (a): rtpmap:18 G729/8000
Media Attribute (a): fmtp:18 annexb=no
Media Attribute (a): rtpmap:98 telephone-event/8000
Media Attribute (a): fmtp:98 0-15
Media Attribute (a): rtpmap:13 CN/8000