Re: TIFF-F specification

[James Rafferty <71043.1114@xxxxxxxxxxxxxx>]

Larry,   

re:  Message text written by Larry Masinter 
># It appears there is a consensus on the IETF FAX list and at the IETF BOF 
># that we need a finite definition of TIFF-F that we can use (at least 
# initially) as the baseline format for fax in email messages.

>Calling something "consensus" doesn't make it so. 

>I say that it appears that there is a consensus on the IETF FAX list
>and at the IETF BOF that we need to define a "minimum baseline" that
>we might expect recipients to be able to deal with, but that in
>general we're willing to have that "minimum" be much more extensive
>than "TIFF-F". In particular, we've discussed the possibility that
>recipients be expected to understand

I heard support at the BOF for "TIFF-F" as a baseline (which covers most of what
the current fax  install base does:  i.e. convey fax image in MH, MR or MMR at
various resolutions (203 x 98 up to 400 x 400)).   

But I also heard support for being able to go beyond that, either using other
extensions to TIFF or other formats.  .  I for one would be quite disappointed
if the group standardized Tiff-f and declared the job of defining fax image
formats is done.    I would want a way to support all of the image file
compression methods available in T.30, but  would not want to require an
"Internet Fax" device to support the ones which are not in common use. 

> image/tiff with a wide variety of tags, resolution, colors
> multipart/mixed for sequential content in different formats
> image/gif and image/jpeg since they're so widespread on the Internet
> image/png because this is the next best standard for images
> text/plain since people want to send plain messages
> text/html since even little cellphones and PDAs can render it

I would add to the list:

image/SPIFF, since it supports bi-level JBIG and the JPEG profile (which
includes references to the CIELAB color space per T.42) which will be used in
color fax, multi-media conferencing (T.120 series, esp. T.126) and H.324
videophones.  

Having said that, the installed base of G3 fax devices only support MH, MR,
sometimes MMR image file formats and in a couple of new cases, bi-level JBIG
(T.82).     There is also some support for T.434 encapsulation of binary files,
but mostly only among computer fax devices for now.     The T.30 and T.4
recommendations for Group 3 fax also include support for some other formats such
as text, mixed image/text and some other binary file formats, none of which are
implemented in the installed base to my knowledge. 

So, if we focus on image file format, putting aside for the moment 1) transport
issues and 2) handling of binary files,  the main requirement to interact with
the installed base of G3 fax devices and applications is to support MH (and
optionally MR and/or MMR compression), for the most frequently used resolutions
and page sizes.  TIFF-F does this.  (comments continued below)


>While I don't think that there is consensus that the 'minimum
>baseline' include all of those options, I also don't think there is
>consensus that the 'minimum baseline' be nearly as restrictive as
>TIFF-F.

TIFF-F as specified in S.100 and VPIM can support either MH(default)  or MMR
(option), and supports nearly all of the ITU approved resolutions for fax.
Whether a proposed stds track TIFF-F  should be refined slightly to also support
MR compression and the rest of the ITU-T approved resolutions (i.e metric
equivalents to 200x400 and 400x400) seems a matter of fine tuning.   

So, TIFF-F as a baseline format for Internet fax does not seem too "restrictive"
with respect to its support for the bi-level (monochromatic) images used in G3
fax as it exists today.     That is what I see as its chief value, to support
what is in use in G3 fax today and build on lots of implementer experience with
TIFF-F among computer fax and other software developers.  

As work proceeds on a draft of TIFF-F,  the WG can evaluate how well TIFF-F
meets these kinds of needs and do fine tuning as necessary.  

However, TIFF-F is by definition a limited subset of TIFF that has been devised
for a specific purpose.    When you go beyond this scope, it is clear that other
file formats are needed.  

Regarding your suggestions on having support for additional richer formats like:
image/tiff (for color, etc), multi-part, image/gif, image/jpeg, I personally
really like the idea, but it moves well beyond what has been specified to date
as part of Group 3  fax.   

So, there is probably value in exploring the relationship between "fax as we
know it" and Internet fax, to address issues such as going beyond the current
fax formats as you have proposed.    I would suggest another thread for that.   

The results of the discussion should provide some good input for the file format
and terminology deliverables of the WG.  

James 

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