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Summary:ASTERISK-17677: SIP faxdetect does not work when using g729 codec
Reporter:Niccolò Belli (darkbasic)Labels:
Date Opened:2011-04-12 08:10:55Date Closed:2011-06-07 14:04:59
Priority:MinorRegression?No
Status:Closed/CompleteComponents:General
Versions:1.8.3 Frequency of
Occurrence
Related
Issues:
Environment:Attachments:( 0) log.txt
( 1) log-with-debug.txt
Description:I am using T.38 termination with Eutelia provider, I can receive faxes flawlessly using g729, but fax detection does not work with g729 (it works when using alaw).

I get this WARNING: Inband DTMF is not supported on codec g729. Use RFC2833

I attached full log.

****** ADDITIONAL INFORMATION ******

sip.conf

[general]
t38pt_udptl=yes,fec,maxdatagram=400

[eutelia]
language=it
type=peer
host=voip.eutelia.it
username=my-eutelia-number
fromuser=my-eutelia-number
secret=my-secret
qualify=yes ;ping per controllo stato
directmedia=no ;asterisk viene sempre usato come media proxy
dtmfmode = rfc2833
insecure=invite,port
context=eutelia-in
t38pt_udptl=yes,fec,maxdatagram=400
faxdetect = yes
disallow=all
allow=g729
;allow=alaw



extensions.conf

[eutelia-in]
exten => my-eutelia-number,1,Answer()
same => n,Dial(SIP/159)

exten => fax,1,Set(FAXFILE=/var/spool/asterisk/fax/prova5.tif)
same => n,ReceiveFAX(${FAXFILE})
Comments:By: Leif Madsen (lmadsen) 2011-04-12 08:17:47

The message you're receiving is telling you exactly what the problem is. You can't use inband DTMF with codecs other than G.711.
By: Niccolò Belli (darkbasic) 2011-04-12 08:25:59

As you can see from my sip.conf I am using dtmfmode = rfc2833
By: David Woolley (davidw) 2011-04-12 08:27:05

Asterisk is behaving perfectly reasonably. As you mentioned T.38, you will not be using G.729 for the actual faxes, and it wouldn't work if you did.  Asterisk is perfectly correct in saying that inband tone detection is not a reasonable expectation for G.729.

I think the only bug here is a misleading error message.  It's probably looking for fax calling tones, not for DTMF, and therefore can't take advantage of RFC 2833.

I think you need to take this to a support channel.
By: Niccolò Belli (darkbasic) 2011-04-12 11:16:46

I'm sorry, I forgot to enable debug in logger.conf. Here is a new log.
By: Leif Madsen (lmadsen) 2011-04-13 09:05:12

<mnicholson> leifmadsen, on 19103 g729 usage will break CNG based fax detection (tone based detection). T.38 reinvite detection should still work.

<mnicholson> and btw, you can fax while g729 is enabled, as long as you use T.38, which is what he is doing.  If he is able to send faxes over g729, then he is doing magic.
By: Leif Madsen (lmadsen) 2011-04-13 09:05:45

Based on the feedback I have seen, I don't consider this a bug. Please move this discussion to the asterisk-users mailing list. Thanks!