On Jan 6, 2011, at 8:56 AM, Kevin P. Fleming wrote: > On 01/05/2011 08:12 PM, Thomas Rymes wrote: >> OK, after my last message about fax detection, I feel a bit better informed >> and able to press forward. I started looking into this because I was getting >> lots of false positive fax detection errors in the logs with faxdetect=both >> set in chan_dahdi.conf. >> >> Anyhow, I do not currently use fax detection, and we have a dedicated Fax >> DID on our PRI, so setting faxdetect=no works fine. Having said that, I >> would like to sort it out as I may want to use fax detection in the future. >> Unfortunately, I seem to be having odd results. I set faxdetect=incoming >> last night and restarted dahdi and asterisk. Since that time, we have >> received 17 faxes, but I only have three fax detections in my asterisk log, >> so far as I can tell: >> >> # grep -i fax /var/log/asterisk/full >> [Jan 5 05:53:39] NOTICE[6686] chan_dahdi.c: Fax detected, but no fax >> extension >> [Jan 5 10:24:27] NOTICE[11834] chan_dahdi.c: Fax detected, but no fax >> extension >> [Jan 5 11:48:52] NOTICE[13804] chan_dahdi.c: Fax detected, but no fax >> extension >> >> All three calls listed are indeed fax calls, and since there is no fax >> extension in that context, the call just proceeds along as if nothing >> happened (which is appropriate). >> >> My question is this: If I have received 17 faxes since enabling fax >> detection, shouldn't I see ~17 entries in the log? > > How are you delivering the inbound FAX calls to your FAX machine? If you are > sending them back out a DAHDI channel (to an FXS port on an analog card, for > example), then as soon as the two channels are bridged the audio never comes > up to Asterisk (under normal circumstances), it stays in DAHDI, so the > Asterisk DSP can't detect the CNG tone. If the FAX machine answers the > incoming call fairly quickly, there may not be any opportunity for the CNG to > be detected. In addition, you may not be even receiving any audio from the > calling FAX machine until you answer the incoming channel (depending on your > PRI provider). > > If you want to have the best chance to detect each incoming FAX using the > Asterisk DSP, you'll have to answer the incoming channel as soon as it hits > the dialplan, then wait 3 or 4 seconds, then send the call onwards to your > actual FAX machine. FAX detection is really expected to be used on calls that > would otherwise be answered by a non-FAX endpoint (IVR, voicemail, user with > a phone, etc.)
That does make sense: the incoming calls are directed to a FreePBX ring group consisting of three IAXModems handled by HylaFAX, and I am fairly certain that they answer the call nearly instantaneously. I do realize that the detection is really intended for non-dedicated lines; I'm just trying to ensure it works before I start using it. Thanks for the response. Tom -- _____________________________________________________________________ -- Bandwidth and Colocation Provided by http://www.api-digital.com -- New to Asterisk? Join us for a live introductory webinar every Thurs: http://www.asterisk.org/hello asterisk-users mailing list To UNSUBSCRIBE or update options visit: http://lists.digium.com/mailman/listinfo/asterisk-users
