Hi!
I was trying to use G726-32 codec, but I had some issues with one of my voip providers, together with FreeSWITCH. The problem appears to be the way the G726-32 codec is defined in the SDP parameters:
INVITE sip:2010@192.168.1.120 SIP/2.0
Via: SIP/2.0/UDP 192.168.1.121:5060;branch=z9hG4bK-516e3ae8
From: 1000 <sip:1000@192.168.1.120>;tag=93ac26a9afdf598o0
To: <sip:2010@192.168.1.120>
Call-ID: 4845f852-c965f8d0@192.168.1.121
CSeq: 101 INVITE
Max-Forwards: 70
Contact: 1000 <sip:1000@192.168.1.121:5060>
Expires: 240
User-Agent: Linksys/PAP2T-5.1.6(LS)
Content-Length: 368
Allow: ACK, BYE, CANCEL, INFO, INVITE, NOTIFY, OPTIONS, REFER
Supported: x-sipura, replaces
Content-Type: application/sdp
v=0
o=- 20427387 20427387 IN IP4 192.168.1.121
s=-
c=IN IP4 192.168.1.121
t=0 0
m=audio 16454 RTP/AVP 2 0 8 96 97 100 101
a=rtpmap:2 G726-32/8000
According to RFC3551, payload type 2 above (in the m=audio and the a=rtpmap:2) is reserved.
Quote: '
Entries in Tables 4 and 5 with payload
type "dyn" have no static payload type assigned and are only used
with a dynamic payload type. Payload type 2 was assigned to G721 in
RFC 1890 and to its equivalent successor G726-32 in draft versions of
this specification, but its use is now deprecated and that static
payload type is marked reserved due to conflicting use for the
payload formats G726-32 and AAL2-G726-32
Thus the PAP2T should not use payload type 2 at all. I believe this is a fault in the firmware.
