Who select the codec in a Inbound Call

[Onorio]

Hi,

I have a doubt about who select the codec in an incoming call through a Sip Trunk. The PBX or the Service provider?
I thought it has a Service provider thing, but after seeing the Monitor I am not sure.
This is the message from the service provider in a incoming call:

12:40:35 184173936mS SIP Rx: UDP SBC:5060 -> PBX:5060
INVITE
Call-ID:
CSeq: 1 INVITE
Max-Forwards: 68
Contact:
Date: Wed, 8 Jul 2015 12:40:36 GMT
Allow: INVITE, ACK, BYE, CANCEL, UPDATE, PRACK, OPTIONS
Supported: 100rel
Accept: application/sdp, application/isup, application/xml
Content-Type: application/sdp
Content-Length: 230
v=0
o=- 2441876578 0 IN IP4
s=-
c=IN IP4
t=0 0
m=audio 7772 RTP/AVP 18 8 101
a=fmtp:18 annexb=no
a=rtpmap:101 telephone-event/8000
a=fmtp:101 0-15
a=sendrecv
a=sqn:0
a=cdsc: 1 image udptl t38

And the response from the PBX is:

12:40:35 184173942mS SIP Tx: UDP PBX:5060 -> SBC:5060
SIP/2.0 200 OK
Via: SIP/2.0/UDP
Allow: INVITE,ACK,CANCEL,OPTIONS,BYE,INFO,NOTIFY,UPDATE
Supported: timer,100rel
Server: IP Office 9.1.2.0 build 91
To:
Content-Type: application/sdp
Content-Length: 222
v=0
o=UserA 1605171005 825336894 IN IP4
s=Session SDP
c=IN IP4
t=0 0
m=audio 46184 RTP/AVP 18 101
a=rtpmap:18 G729/8000
a=fmtp:18 annexb=no
a=rtpmap:101 telephone-event/8000
a=fmtp:101 0-15

So it look like is the PBX in the response the one who is selecting the codec G729. Is that right?
Thanks

 

[sizbut]

Fairly standard that the target of the call gets to say which codec to use. The caller only gets to indicate what they support in order of preference.

Stuck in a never ending cycle of file copying.

 

[Onorio]

So, it means in an outbound call the codec is selected by the Service provider and in an incoming call by the PBX?
I thought it was totally the opposite, how wrong I was.
Thanks