flexfax: Please help me understand encoding

["Mau, Jonathan" <Jonathan.Mau@nrc.ca>]

Greetings:

I have been playing with HylaFAX on and off for some of months now.
Recently, I have been doing more intensive testing and am puzzled by how the
compression/encoding works.  Some things lead me to believe that the modem
does the encoding.  For example from the Multitech document "Class 2 Fax
Developer's Kit" page 23 indicates that 2-D MR and 2-D MMR are not
supported.  But then some things indicate that HylaFAX does the encoding.
For example, from man page HYLAFAX(5F) "Documents are automatically
converted to TIFF/F documents prior to transmission according to the
capabilities of the remote fascimile machine:  maximum page width and
length, ability to handle 2-D encoded data, ...".

Of the 15 or so numbers I have used for testing, all but 2 list their
capabilities as "supports2DEncoding:yes", yet all the completed email
messages indicate that 1-D encoding was used.  (This is not quite true, a
few pages were noted to have used 2-D, but that was a month ago and the
modems used then are not the same as the ones I am using now.)  The config
man page indicates that Use2D defaults to yes and I have not explicitly set
it otherwise anywhere.   So why is 2-D compression not being used?  I am
sending test documents at 196lines/inch vertical resolution pages in about
1.5 minutes/page (granted, these are busy pages) and feel that 2-D encoding
would improve this time greatly.

What am I missing?

Thanks for all tips

Jonathan