[Freeswitch-users] codec negotiation weirdness

[Brian J. Tarricone]

Hi all,

I'm experiencing some strange behavior with codec negotiation.  I'm
using the default early negotiation, and I'm setting
inbound-codec-negotiation to "scrooge" so FS will always have the
final word on what codec is used.  (I've also tried "greedy" with the
same results.  "generous" does not meet my needs, unfortunately.)

I'm setting inbound-codec-prefs to the following:

opus at 48000h@20i,isac at 32000h@30i,speex at 16000h@20i,speex at 8000h@20i,PCMU

However, I'm seeing FS select PCMU for a client that advertises both
isac/32k and PCMU.  The relevant portion of the FS log is below.

2013-02-16 01:45:06.947647 [DEBUG] sofia.c:5589 Remote SDP:
v=0
o=- 1772524861 1772524861 IN IP4 10.70.209.126
s=-
c=IN IP4 10.70.209.126
t=0 0
m=audio 57178 RTP/AVP 103 104 0 8 106 105 13 126
c=IN IP4 10.70.209.126
a=rtpmap:103 ISAC/16000
a=rtpmap:104 ISAC/32000
a=rtpmap:0 PCMU/8000
a=rtpmap:8 PCMA/8000
a=rtpmap:106 CN/32000
a=rtpmap:105 CN/16000
a=rtpmap:13 CN/8000
a=rtpmap:126 telephone-event/8000

2013-02-16 01:45:06.947647 [DEBUG] sofia_glue.c:5139 Audio Codec
Compare [ISAC:103:16000:30:0]/[opus:116:48000:20:32000]
2013-02-16 01:45:06.947647 [DEBUG] sofia_glue.c:5139 Audio Codec
Compare [ISAC:104:32000:30:0]/[opus:116:48000:20:32000]
2013-02-16 01:45:06.947647 [DEBUG] sofia_glue.c:5139 Audio Codec
Compare [PCMU:0:8000:20:64000]/[opus:116:48000:20:32000]
2013-02-16 01:45:06.947647 [DEBUG] sofia_glue.c:5139 Audio Codec
Compare [PCMA:8:8000:20:64000]/[opus:116:48000:20:32000]
2013-02-16 01:45:06.947647 [DEBUG] sofia_glue.c:5139 Audio Codec
Compare [CN:106:32000:20:0]/[opus:116:48000:20:32000]
2013-02-16 01:45:06.947647 [DEBUG] sofia_glue.c:5139 Audio Codec
Compare [CN:105:16000:20:0]/[opus:116:48000:20:32000]
2013-02-16 01:45:06.947647 [DEBUG] sofia_glue.c:5139 Audio Codec
Compare [CN:13:8000:20:0]/[opus:116:48000:20:32000]
2013-02-16 01:45:06.947647 [DEBUG] sofia_glue.c:5139 Audio Codec
Compare [telephone-event:126:8000:20:0]/[opus:116:48000:20:32000]
2013-02-16 01:45:06.947647 [DEBUG] sofia_glue.c:5268 Set 2833 dtmf
send/recv payload to 126
2013-02-16 01:45:06.947647 [DEBUG] sofia_glue.c:5139 Audio Codec
Compare [ISAC:103:16000:30:0]/[SPEEX:99:16000:20:42200]
2013-02-16 01:45:06.947647 [DEBUG] sofia_glue.c:5139 Audio Codec
Compare [ISAC:104:32000:30:0]/[SPEEX:99:16000:20:42200]
2013-02-16 01:45:06.947647 [DEBUG] sofia_glue.c:5139 Audio Codec
Compare [PCMU:0:8000:20:64000]/[SPEEX:99:16000:20:42200]
2013-02-16 01:45:06.947647 [DEBUG] sofia_glue.c:5139 Audio Codec
Compare [PCMA:8:8000:20:64000]/[SPEEX:99:16000:20:42200]
2013-02-16 01:45:06.947647 [DEBUG] sofia_glue.c:5139 Audio Codec
Compare [CN:106:32000:20:0]/[SPEEX:99:16000:20:42200]
2013-02-16 01:45:06.947647 [DEBUG] sofia_glue.c:5139 Audio Codec
Compare [CN:105:16000:20:0]/[SPEEX:99:16000:20:42200]
2013-02-16 01:45:06.947647 [DEBUG] sofia_glue.c:5139 Audio Codec
Compare [CN:13:8000:20:0]/[SPEEX:99:16000:20:42200]
2013-02-16 01:45:06.947647 [DEBUG] sofia_glue.c:5139 Audio Codec
Compare [telephone-event:126:8000:20:0]/[SPEEX:99:16000:20:42200]
2013-02-16 01:45:06.947647 [DEBUG] sofia_glue.c:5268 Set 2833 dtmf
send/recv payload to 126
2013-02-16 01:45:06.947647 [DEBUG] sofia_glue.c:5139 Audio Codec
Compare [ISAC:103:16000:30:0]/[SPEEX:99:8000:20:24600]
2013-02-16 01:45:06.947647 [DEBUG] sofia_glue.c:5139 Audio Codec
Compare [ISAC:104:32000:30:0]/[SPEEX:99:8000:20:24600]
2013-02-16 01:45:06.947647 [DEBUG] sofia_glue.c:5139 Audio Codec
Compare [PCMU:0:8000:20:64000]/[SPEEX:99:8000:20:24600]
2013-02-16 01:45:06.947647 [DEBUG] sofia_glue.c:5139 Audio Codec
Compare [PCMA:8:8000:20:64000]/[SPEEX:99:8000:20:24600]
2013-02-16 01:45:06.947647 [DEBUG] sofia_glue.c:5139 Audio Codec
Compare [CN:106:32000:20:0]/[SPEEX:99:8000:20:24600]
2013-02-16 01:45:06.947647 [DEBUG] sofia_glue.c:5139 Audio Codec
Compare [CN:105:16000:20:0]/[SPEEX:99:8000:20:24600]
2013-02-16 01:45:06.947647 [DEBUG] sofia_glue.c:5139 Audio Codec
Compare [CN:13:8000:20:0]/[SPEEX:99:8000:20:24600]
2013-02-16 01:45:06.947647 [DEBUG] sofia_glue.c:5139 Audio Codec
Compare [telephone-event:126:8000:20:0]/[SPEEX:99:8000:20:24600]
2013-02-16 01:45:06.947647 [DEBUG] sofia_glue.c:5268 Set 2833 dtmf
send/recv payload to 126
2013-02-16 01:45:06.947647 [DEBUG] sofia_glue.c:5139 Audio Codec
Compare [ISAC:103:16000:30:0]/[PCMU:0:8000:20:64000]
2013-02-16 01:45:06.947647 [DEBUG] sofia_glue.c:5139 Audio Codec
Compare [ISAC:104:32000:30:0]/[PCMU:0:8000:20:64000]
2013-02-16 01:45:06.947647 [DEBUG] sofia_glue.c:5139 Audio Codec
Compare [PCMU:0:8000:20:64000]/[PCMU:0:8000:20:64000]
2013-02-16 01:45:06.947647 [DEBUG] sofia_glue.c:5161 Bah HUMBUG!
Sticking with PCMU at 8000h@20i

As you can see, it first compares all offered codecs against opus/48k,
next skips isac completely, then goes to speex/16k, speex/8k, and
PCMU, and eventually grudgingly accepts PCMU.

Interestingly, if I drop opus from the list, and leave the rest as-is,
it does select isac/32k, but weirdly:

2013-02-16 01:51:10.691314 [DEBUG] sofia_glue.c:5139 Audio Codec
Compare [ISAC:103:16000:30:0]/[isac:99:32000:30:160000]
2013-02-16 01:51:10.691314 [DEBUG] sofia_glue.c:5161 Bah HUMBUG!
Sticking with isac at 32000h@30i

It picks isac/32k after only examining the isac/16k line in the SDP,
before it even gets to isac/32k.  (In fact those are the only 2 lines
after the SDP is printed; it makes the decision after making just one
comparison.)

Any ideas?  Am I just misunderstanding how this works?

Thanks,
Brian