Unknown RTP codec 100 received / T.38 / asterfax


After some troubles to install txfax/rxfax correctly,It’s working… But I have an error “Unknown RTP codec 100 received”, I see on google/digium/voip-info that’s due to the T.38, and I tried to read the digium post, but I don’t understand how to fix that.

I use asterisk 1.2.15
asterfax-1.1-freeb4.i386 (rpm)

That’s when I’m trying to send a fax to my fax connected on my sipura (local), with ./call.sh localfax.cal in /usr/lib/asterfax/test/call…/

If you can help me, thank you in advance.
And thanks for your job.



(PS : sorry for my english)

call.sh by default


Channel: SIP/1001
MaxRetries: 0
WaitTime: 20
Priority: 1
Application: txfax
Context: from-sip

in asterisk :


-- Attempting call on SIP/1001 for application txfax(/usr/lib/asterfax/test/attachments/testpage.pdf|caller|debug) (Retry 1)
   > Channel SIP/1001-09cc8b20 was answered.
   > Launching txfax(/usr/lib/asterfax/test/attachments/testpage.pdf|caller|debug) on SIP/1001-09cc8b20

Feb 28 15:00:35 NOTICE[3267]: rtp.c:576 ast_rtp_read: Unknown RTP codec 100 received
Feb 28 15:00:44 NOTICE[3267]: pbx_spool.c:279 attempt_thread: Call completed to SIP/1001

Ok this should open the stock rtp.c file near (just above I think) the codec list
what codec is 100???

nano +680 /usr/src/asterisk/rtp.c

If you see the codec you wish to use (say it is 101) just clone 101 to 100 just above 101 and rebuild asterisk.
Or try to find out why the codec failed…