[asterisk-users] Too Few Fax Detections

[Thomas Rymes]

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?

Assuming the answer to that question is yes, what might be causing the system to not detect faxes on the other 14 calls?

Many thanks,

Tom