Re: [hylafax-users] Incomplete fax reported as successful

[Lee Howard <faxguy@xxxxxxxxxxxxxxxx>]

Ole Kaas wrote:
> I have some fax jobs to a certain receiver which is reported as sent successfully. The receiver, however, claims that the received document is incomplete. Only a couple of inches can be seen. The receiving device is a Possio GSM fax mounted in a truck (they have several). It is only some of the jobs that fails in this way. To rule out any document conversion errors I have resent the docXXXXXX.ps from the archived jobs to our own fax number using sendfax from command line. The job goes through without problems. Faxing from other devices to the GSM fax also works.  
>
> Email+pdf => mail2fax => Hylafax 5.4.1(GS 8.72) => IAXmodem 1.2.0 => Asterisk 1.4.29 => wanpipe A104/V=42 => TDM

The receiver does not support V.17 and does not support ECM... so you'll 
necessarily end up sending them a fax that is not using ECM, and 
therefore there is no way to instruct the receiver exactly how much data 
was sent.

> Dec 06 09:57:43.42: [30262]: <-- [9:AT+FRH=3\r]
> Dec 06 09:57:44.90: [30262]: --> [7:CONNECT]
> Dec 06 09:57:46.30: [30262]: --> HDLC<8:FF C8 01 00 72 1E 7F B5>
> Dec 06 09:57:46.40: [30262]: --> [2:OK]
> Dec 06 09:57:46.40: [30262]: REMOTE best rate 9600 bit/s
> Dec 06 09:57:46.40: [30262]: REMOTE max A4 page width (215 mm)
> Dec 06 09:57:46.40: [30262]: REMOTE max unlimited page length
> Dec 06 09:57:46.40: [30262]: REMOTE best vres 7.7 line/mm
> Dec 06 09:57:46.40: [30262]: REMOTE format support: MH
> Dec 06 09:57:46.40: [30262]: REMOTE best 0 ms/scanline
> Dec 06 09:57:46.40: [30262]: USE 9600 bit/s
> Dec 06 09:57:46.40: [30262]: SEND file "docq/doc494648.ps;1c01"
> Dec 06 09:57:46.40: [30262]: USE A4 page width (215 mm)
> Dec 06 09:57:46.40: [30262]: USE unlimited page length
> Dec 06 09:57:46.40: [30262]: USE 7.7 line/mm
> Dec 06 09:57:46.40: [30262]: USE 1-D MH
> Dec 06 09:57:46.40: [30262]: USE 0 ms/scanline
....
> Dec 06 09:58:23.00: [30262]: SEND send EOP (no more pages or documents)
> Dec 06 09:58:23.00: [30262]: <-- [9:AT+FTH=3\r]
> Dec 06 09:58:23.02: [30262]: --> [7:CONNECT]
> Dec 06 09:58:23.02: [30262]: <-- HDLC<3:FF C8 F4>
> Dec 06 09:58:23.02: [30262]: <-- data [3]
> Dec 06 09:58:23.02: [30262]: <-- data [2]
> Dec 06 09:58:24.10: [30262]: --> [2:OK]
> Dec 06 09:58:24.10: [30262]: <-- [9:AT+FRH=3\r]
> Dec 06 09:58:25.88: [30262]: --> [7:CONNECT]
> Dec 06 09:58:27.22: [30262]: --> HDLC<5:FF C8 31 45 8F>
> Dec 06 09:58:27.34: [30262]: --> [2:OK]
> Dec 06 09:58:27.34: [30262]: SEND recv MCF (message confirmation)

The receiver confirmed the page receipt.  Therefore, it was a successful 
fax.  (Albeit the fax was non-ECM, and therefore the assurances of what 
that means are rather limited.)

The receiver could have looked for the RTC signal in the image data and 
used that as a basis on whether to signal MCF or RTN... but it did not.  
The receiver could have used the resolution and amount of data received 
to determine whether to signal MCF or  RTN... but it apparently did not.

So given that the receiver does not support ECM and is completely 
willing to confirm pages that are only partially received, the receiver 
should not be surprised when this happens.

The reason why this happened is probably due to premature carrier loss 
during Phase C.  In other words, the fax image data rides in a carrier 
signal.  The receiver will read data from the carrier to create the 
image until the carrier is lost.  At some point early-on in the 
communication of that image data there was a disturbance in the audio 
(possibly jitter) which caused the receiver to detect a carrier loss.  
It then waited patiently for the end-of-page signal, eventually heard 
it, and then confirmed page receipt.

So you could approach this in a couple different ways:  1) you could get 
the receiver to start supporting ECM somehow, or 2) you could figure out 
where the audio disturbance is and fix that.

Thanks,

Lee.


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