Re: [hylafax-users] Received Premature V.34 Termination

[Lee Howard <faxguy@xxxxxxxxxxxxxxxx>]

Hans Strickler wrote:

> We are seeing from a few different Fax machines a V.34 error "RECV 
> FAX: Failed to properly open V.34 primary channel"
>
>  
>
> How do I make Hylafax default to a more robust receiver?

Upgrade to current HylaFAX CVS HEAD (or wait for 4.2.2).  If problems 
continue disable V.34.

> May 31 17:50:14.92: [30322]: RECV send MCF (message confirmation)
>
> May 31 17:50:14.92: [30322]: <-- HDLC<3:FF C8 31>
>
> May 31 17:50:14.92: [30322]: <-- data [3]
>
> May 31 17:50:14.92: [30322]: <-- <3:FF 13 8C>
>
> May 31 17:50:14.92: [30322]: <-- data [2]
>
> May 31 17:50:14.92: [30322]: <-- <2:10 03>
>
> May 31 17:50:14.92: [30322]: MODEM input buffering enabled
>
> May 31 17:50:16.43: [30322]: --> <4:10 6B 10 79>
>
> May 31 17:50:16.43: [30322]: Primary channel selected
>
> May 31 17:50:53.06: [30322]: --> <2:10 04>
>
> May 31 17:50:53.06: [30322]: EOT received (end of transmission)
>
> May 31 17:50:53.06: [30322]: Received premature V.34 termination.

There were some changes made to this portion of code that will be found 
in 4.2.2.  Namely the timing of the input buffering.  After first 
testing that change (which was required to improve some non-V.34 
sessions on some non-V.34-capable modems) on V.34 sessions it appeared 
to have resolved a lot of issues with problematic V.34-sessions.  But, 
my analysis wasn't very scientific, and I still see these kinds of 
errors, so I don't know that it really did anything for V.34 ... or at 
least as significant of an improvement as I had once hoped.  The 
improvements in the testing scenario may have just been a coincidental 
fluke.

A V.34 receiver is very much at the mercy of the sender.  And, 
unfortunately, Agere doesn't give the receiving DTE much control over 
what little is even available to it per spec.  Most of the session 
control is handled by the modem and isn't much influenced by the DTE in 
cases like these.

So upgrade your HylaFAX code.  If that doesn't help then look at your 
lines and try to clean up any noise.  If that doesn't yield anything, 
then don't use V.34 and perhaps see if MultiTech can do anything here... 
although chances are good that the problem is a V.34-Fax thing more than 
it is a HylaFAX or a modem thing.

This is one reason why we have a "HasV34Trouble" indicator when sending 
faxes.  Some communication paths just cannot be reliably sustained with 
V.34.

Lee.


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