Re: [hylafax-users] large multiport systems

[Lee Howard <faxguy@xxxxxxxxxxxxxxxx>]

On 2003.08.26 10:24 Darren Nickerson wrote:

> I may be wrong here Lee, but my research tells me you should look for
> another culrprit if you're looking to improve your V.34 broadcast
> performance.

I have suspicions that V.8 handshaking functions slightly different 
when using digital equipment than when using analog equipment.  The 
only equipment of which I am aware that supports V.34 faxing with 
analog equipment comes from either MultiTech or BrookTrout.  As HylaFAX 
(open source) only supports the former, I have no reason to blame the 
increase in handshaking time when V.8 is attempted (either by the 
receiver, by the sender, or by both) on the manufacturer's 
implementation.  When HylaFAX truly supports Class 1.0 then maybe I'll 
be in a position to draw conclusions that way.  In any case, the 
increase in handshaking time of which I have spoken is "only" on the 
order of 1-3 seconds per call.  Almost any significant amount of image 
data will easily offset this delay.  I was wrong in concluding 
otherwise.

The other culprit of which you speak is ECM protocol.

Usage of V.34 requires the usage of ECM protocol.  ECM protocol 
actively strives for perfect image quality.  Non-ECM protocol only 
strives for near-perfect quality, depending upong the copy-quality 
settings of the receiver.  So the likelihood that retransmission of 
image data (due to PPR) will occur in an ECM fax is much greater than 
the likelihood that retransmission of image data (due to RTN) will 
occur in a non-ECM fax.

It is inaccurate and misleading to compare ECM faxing against non-ECM 
faxing (or vice-versa) due to this difference in goals.

I've seen lots of marketing material out there (propaganda?) that tries 
to sell people on purchasing new hardware, software, or both because 
making that investment into V.34 and MMR-supporting equipment will "pay 
for itself over time in toll savings and necessary lines".  This is 
only always true if we are only considering ECM faxing.  It is only 
sometimes true (and in my experience, more often it is untrue) when 
also considering non-ECM faxing.

A fax sent without ECM at 14400 bps with MR compression can, when 
enough noise exists to put image quality less than perfect but still 
"near-perfect" (and this is a very common situation), be sent faster 
than a fax sent at 33600 bps with MMR compression (with requisite ECM, 
of course) because with ECM faxing image data had to be resent, 
sometimes repeatedly, to acheive perfect image quality while non-ECM 
faxing completed successfully without image data retransmission.

I suspect that most people are going to find the value in ECM faxing to 
be worth it.  However, I also suspect that there are going to be some 
people, particularly bulk faxers, which will think otherwise - because 
in non-ECM faxing if the receiver sends MCF rather than RTN, that means 
that the image quality was "good enough" for them... and the "savings" 
of not using ECM is better spent sending more faxes out.

Lee.

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