provider sends ACK to FS

sip phone sends 200OK (to the UPDATE) with sdp (G729 + te) to FS

At this point I have a bidirectional g711a rtp stream on the external profile. Instead on the internal profile i receive g729 from the phone but FS does not send any G729 stream to the phone.

I have run some tests: if i don't have G711a codec as 1st choice in the incoming INVITE, the audio is ok; both the provider and the phone support both G711a and G729, but sip phone always answer ONLY with its preferred codec (in this test, G729).

Generally speaking, if sip phone's preferred codec is different from the first codec in the incoming INVITE from the provider, i have the issue. Since the codec mix and order from the provider is not known, i cannot configure the sip phone accordingly.

On both external and internal profiles i have:

FS logfile presents an error (loglevel: INFO, privacy data screened with *):

922bb07e-8dce-4416-9073-52db21a8a432 2019-05-09 17:27:59.997037 [NOTICE] switch_channel.c:1104 New Channel sofia/external/********@******.net [922bb07e-8dce-4416-9073-52db21a8a432]
922bb07e-8dce-4416-9073-52db21a8a432 2019-05-09 17:27:59.997037 [INFO] mod_dialplan_xml.c:637 Processing ******* <*******>->************ in context public
922bb07e-8dce-4416-9073-52db21a8a432 2019-05-09 17:28:00.037033 [NOTICE] switch_ivr.c:2172 Transfer sofia/external/ ********@******.net to XML[6000@************]
922bb07e-8dce-4416-9073-52db21a8a432 2019-05-09 17:28:00.037033 [INFO] mod_dialplan_xml.c:637 Processing  ******** < ******** >->6000 in context  ************
[...]
fb16ac80-17f5-451b-a8ee-d22a135afc51 2019-05-09 17:28:00.197034 [NOTICE] switch_channel.c:1104 New Channel sofia/internal-bs/6000@192.168.50.119:5064 [fb16ac80-17f5-451b-a8ee-d22a135afc51]
[...]
2019-05-09 17:28:00.277039 [INFO] sofia.c:1279 sofia/internal-bs/6000@192.168.50.119:5064 Update Callee ID to "6000 6000" <6000>
fb16ac80-17f5-451b-a8ee-d22a135afc51 2019-05-09 17:28:00.277039 [NOTICE] sofia.c:7156 Ring-Ready sofia/internal-bs/6000@192.168.50.119:5064!
922bb07e-8dce-4416-9073-52db21a8a432 2019-05-09 17:28:00.277039 [INFO] switch_ivr_originate.c:1215 Sending early media
922bb07e-8dce-4416-9073-52db21a8a432 2019-05-09 17:28:00.277039 [NOTICE] sofia_media.c:92 Pre-Answer sofia/external/********@******.net!
[...]
fb16ac80-17f5-451b-a8ee-d22a135afc51 2019-05-09 17:28:03.497034 [NOTICE] sofia.c:8167 Channel [sofia/internal-bs/6000@192.168.50.119:5064] has been answered
922bb07e-8dce-4416-9073-52db21a8a432 2019-05-09 17:28:03.497034 [NOTICE] switch_ivr_originate.c:3632 Channel [sofia/external/********@******.net] has been answered
fb16ac80-17f5-451b-a8ee-d22a135afc51 2019-05-09 17:28:03.577036 [ERR] sofia.c:8020 Codec Error! v=0
fb16ac80-17f5-451b-a8ee-d22a135afc51 o=- 1027803 1027804 IN IP4 192.168.50.119
fb16ac80-17f5-451b-a8ee-d22a135afc51 s=-
fb16ac80-17f5-451b-a8ee-d22a135afc51 c=IN IP4 192.168.50.119
fb16ac80-17f5-451b-a8ee-d22a135afc51 t=0 0
fb16ac80-17f5-451b-a8ee-d22a135afc51 m=audio 25546 RTP/AVP 18 101
fb16ac80-17f5-451b-a8ee-d22a135afc51 a=rtpmap:18 G729/8000
fb16ac80-17f5-451b-a8ee-d22a135afc51 a=fmtp:18 annexb=no
fb16ac80-17f5-451b-a8ee-d22a135afc51 a=rtpmap:101 telephone-event/8000
fb16ac80-17f5-451b-a8ee-d22a135afc51 a=fmtp:101 0-15
fb16ac80-17f5-451b-a8ee-d22a135afc51 a=ptime:20
fb16ac80-17f5-451b-a8ee-d22a135afc51

Matching packets time and logfile time, the "sofia.c:8020 Codec Error!" matches the sip phone 200OK answer to the UPDATE message.

I tried to navigate the sofia.c code but i can't actually figure out what's happening.

Please note that on a FS 1.4.9 setup (with a, i would say, "identical" configuration) this works, i.e. a bidirectional g729 stream is estabilished on the FS<->phone leg, also with identical signalling.

I am wondering if there is any config parameter that should be edited/added/removed on the 1.6.x compared to the 1.4.x configuration.

Btw, G729 commercial codec is active and running on both systems.

Any hint is appreciated and, if needed i can post more data/log/tests.