T38 to G711 fax


I’m new to Asterisk but trying my best.
I’m trying to connect my sip server to Genesys Cloud and the issu im having si that Genesys only supports faxes over T30/G711 and my providers supports only T38.

I have found T.38 Fax Gateway - Asterisk Project - Asterisk Project Wiki but I don’t know where to put it. I think it should go to extensions.conf, should i oncorporate it in the same context as extensions to Genesys? If yes is it just copy paste or do i have to change something in those 3 lines:
exten => 1,1,NoOp()
exten => 1,n,Set(FAXOPT(gateway)=yes)
exten => 1,n,Dial(SIP/mypeer,20)

Kindly asking for help

Your provider should not really care what you send in the audio stream. Sending fax can either be done in an “IP Telephony safe” way, using T38, or the old fashioned way, as plain audio.

The only configuration you need to make on your side, is to allow fallback if T38 negotiation fails, or disable T38 all together.

Not using T38 will ONLY work if using a codec like G711a/µ, or other more or less lossless codecs. If using GSM, Opus or similar, the audio stream will usually not pass the fax data through correctly.

Fax calls should be actually handled with line echo canceler disabled, so fax signal detection is needed.
From my experience G.711 faxing tends to be not reliable though - it works acceptably for some but failure rate varies.

Well, with the providers I work with, I’ve had more success using G.711, than T38, but I agree T38 should be preferred, if available.

Also, at least in my country, most phone networks today, are primarily IP links, doing signal processing only when you need to convert from IP to analogue connections. (And maybe SS7 interconnect links, but most interconnects are IP as well.)

That is why I want to enable t38 gateway to convert g711 from Genesys Pure Cloud to T38 on my asterisk server so i can send it to providers.

here is wat i came with for extensions.conf but it’s not working

exten => _[123456789]X.,1,NoOp(**** FAX DETECTED ****),Verbose(1,----->genesys out: exten: ${EXTEN})
same => n,Set(FAXOPT(gateway)=yes)
same => n,Dial(PJSIP/${TECHPREFIX}${EXTEN}@Opensips_5060,120)
same => n,Verbose({FAXOPT(statusstr)})
same => n,Hangup()

exten => _+[123456789]X.,1,Verbose(1,----->genesys out: exten: ${EXTEN})
same => n,Set(FAXOPT(gateway)=yes)
same => n,Dial(PJSIP/${TECHPREFIX}${EXTEN}@Opensips_5060,120)
same => n,Hangup()

This topic was automatically closed 30 days after the last reply. New replies are no longer allowed.