[asterisk-users] Any idea what causes "Oooh, got a frame with format of g729 on channel 'PJSIP/121-000001d2' when we're sending 'ulaw', switching to match"

[Dan Cropp]

The PJSIP endpoint is configured for ulaw only.  Not sure how or why we are seeing the g729 on calls for this endpoint.

Would this be a case that asterisk detects the rtp stream is g729 even though it's negotiated as ulaw?
Why would asterisk change the format to g729 when disallow = all and allow = ulaw are the endpoint settings?

[121]
type = endpoint
context = IS
transport = transport1
aors = 121
accountcode = 2
dtmf_mode = inband
device_state_busy_at = 96
force_rport = no
identify_by = username,ip
disallow = all
allow = ulaw
from_user = 121
acl = acl1

[10/03 11:29:34.240] DEBUG[21414][C-00000226] chan_pjsip.c: Oooh, got a frame with format of g729 on channel 'PJSIP/121-000001d2' when we're sending 'ulaw', switching to match


INVITE sip:2197 at XXX.XXX.XXX.XXX:5060 SIP/2.0
Via: SIP/2.0/UDP YYY.YYY.YYY.YYY:5060;branch=z9hG4bKxqyYl2Jg84158000
To: <sip:2197@ XXX.XXX.XXX.XXX <sip:2197 at 192.168.11.176> >
From: <sip:STUFF at YYY.YYY.YYY.YYY <sip:STUFF at YYY.YYY.YYY.YYY%20> >;tag=I0n4X7KK
Contact: <sip:STUFF @YYY.YYY.YYY.YYY:5060<sip:STUFF%20 at YYY.YYY.YYY.YYY:5060>>
Call-ID: OlrmFuyOq-0000-@ YYY.YYY.YYY.YYY <mailto:OlrmFuyOq-0000- at 192.168.10.213>
CSeq: 2223 INVITE
Max-Forwards: 70
Allow: INVITE,ACK,CANCEL,BYE,OPTIONS,REFER,NOTIFY
Supported: replaces
Content-Type: application/sdp
Content-Length: 335

v=0
o=- 11264000 11264000 IN IP4 YYY.YYY.YYY.YYY
s=-
c=IN IP4 192.168.10.213
t=0 0
m=audio 32768 RTP/AVP 0 2 8 18 110 120 100
a=rtpmap:0 PCMU/8000
a=rtpmap:2 G726-32/8000
a=rtpmap:8 PCMA/8000
a=rtpmap:18 G729/8000
a=rtpmap:110 G723/5300
a=rtpmap:120 G723/6300
a=rtpmap:100 telephone-event/8000
a=fmtp:100 0-15
a=sendrecv

Send
SIP/2.0 200 OK
Via: SIP/2.0/UDP YYY.YYY.YYY.YYY:5060;received=YYY.YYY.YYY.YYY;branch=z9hG4bKxqyYl2Jg84158000
Call-ID: OlrmFuyOq-0000- at YYY.YYY.YYY.YYY <mailto:OlrmFuyOq-0000- at YYY.YYY.YYY.YYY%20>
From: <sip:STUFF at YYY.YYY.YYY.YYY >;tag=I0n4X7KK
To: <sip:2197 at XXX.XXX.XXX.XXX <sip:2197 at XXX.XXX.XXX.XXX%20> >;tag=b4134118-08f4-4dbc-a145-573d04438092
CSeq: 2223 INVITE
Server: Asterisk PBX 13.20.0
Allow: OPTIONS, SUBSCRIBE, NOTIFY, PUBLISH, INVITE, ACK, BYE, CANCEL, UPDATE, PRACK, REGISTER, REFER, MESSAGE
Contact: <sip:YYY.YYY.YYY.YYY:5060>
Supported: 100rel, timer, replaces, norefersub
Content-Type: application/sdp
Content-Length:   181

v=0
o=- 11264000 11264002 IN IP4 YYY.YYY.YYY.YYY
s=Asterisk
c=IN IP4 192.168.11.176
t=0 0
m=audio 18380 RTP/AVP 0
a=rtpmap:0 PCMU/8000
a=ptime:20
a=maxptime:150
a=sendrecv


Receive
ACK sip:XXX.XXX.XXX.XXX:5060 SIP/2.0
Via: SIP/2.0/UDP YYY.YYY.YYY.YYY:5060;branch=z9hG4bKCIJuiRuH8415a000
To: <sip:2197@ XXX.XXX.XXX.XXX <sip:2197 at 192.168.11.176> >;tag=b4134118-08f4-4dbc-a145-573d04438092
From: <sip:STUFF@ YYY.YYY.YYY.YYY <sip:STUFF@%20YYY.YYY.YYY.YYY%20> >;tag=I0n4X7KK
Max-Forwards: 70
Call-ID: OlrmFuyOq-0000- at YYY.YYY.YYY.YYY<mailto:OlrmFuyOq-0000- at YYY.YYY.YYY.YYY>
CSeq: 2223 ACK


Asterisk debugging outputs the following.
[10/03 11:29:34.240] DEBUG[21414][C-00000226] chan_pjsip.c: Oooh, got a frame with format of g729 on channel 'PJSIP/121-000001d2' when we're sending 'ulaw', switching to match
[10/03 11:29:34.240] DEBUG[21414][C-00000226] channel.c: Channel PJSIP/121-000001d2 setting write format path: ulaw -> g729
[10/03 11:29:34.240] DEBUG[21414][C-00000226] channel.c: Channel PJSIP/121-000001d2 setting read format path: ulaw -> g729
[10/03 11:29:34.240] DEBUG[21414][C-00000226] channel.c: Channel PJSIP/121-000001d2 setting read format path: g729 -> g729

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