Subject: Re: [Fax] Comments on ietf-fax-feature-schema-04.txt

From: Graham Klyne <[email-masked]>
Date: Mon, 04 Jan 1999 18:36:20 +0000

James,

<excerpt>

At 11:31 29/12/98 -0500, James  Rafferty wrote: 

<excerpt><fontfamily><param>Courier</param>3.7 Image coding

  Feature tag name    Legal values

  ----------------    ------------

  image-file-         TIFF-S

 structure           TIFF-F

                     TIFF-J

                     TIFF-C

                     TIFF-L

                     TIFF-M

                     (may be extended by further registrations,

                     to cover non-TIFF image file structures)

  image-coding        MH

                     MR

                     MMR

                     JBIG

                     JPEG

                     (may be extended by further registrations)

  image-coding-       JBIG-T85    (bi-level, per ITU T.85)

  constraint          JBIG-T43    (multi-level, per ITU T.43)

                     JPEG-T4E    (per ITU T.4, Annex E)

                     (may be extended by further registrations)

  JBIG-stripe-size    <<Integer>

  image-interleave    Stripe

                     Plane

  color-subsampling   "1:1:1"     (no color subsampling)

                     "4:1:1"     (4:1:1 color subsampling)

 MRC-mode            <<Integer> (0..7)   (per ITU T.44 [15])

</fontfamily></excerpt><fontfamily><param>Courier</param> 
MRC-max-stripe-size <<Integer>

There are quite a few options here and not too much guidance on how to
use them.   Should we include some kind of text in this section which
provides a small amount of guidance and a pointer to the examples such
as:  

 "For most applications, specification of the image-file-structure tag
and its values alone does not provide sufficient granularity to precisely
describe the image coding capabilities of a recipient.   Implementors
should provide sufficient  detail

so that it is clear values of these feature tags are supported and which
are not.  (See examples in section 4.)"

<excerpt>

</excerpt></fontfamily></excerpt><<<<<<<<

I have added the following (Does it provide the level of guidance you
seek?):

  NOTE: there are many image coding options here, 

  and not all are required in all circumstances.

  Specification of the image-file-structure tag 

  value alone is not normally sufficient to 

  describe the capabilities of a recipient.  A 

  general rule is that sufficient detail should 

  be provided to exclude any unsupported 

  features.

  For extended Internet fax, image-file-structure 

  and image-coding should always be specified, 

  together with additional values described above 

  as needed to clearly indicate which feature tag 

  values are supported and which are not.  (See 

  also the examples in section 4.)

#g

------------

Graham Klyne

([email-masked])

---

From: James Rafferty <[email-masked]>
Date: Tue, 05 Jan 1999 10:05:41 -0500

At 06:36 PM 1/4/99 +0000, Graham Klyne wrote: 
>
> James, 
>
>
>>
>> There are quite a few options here and not too much guidance on how to use
>> them.   Should we include some kind of text in this section which
provides a
>> small amount of guidance and a pointer to the examples such as:  
>>
>> "For most applications, specification of the image-file-structure tag and
>> its values alone does not provide sufficient granularity to precisely
should
>> provide sufficient  detail 
are
>> not.  (See examples in section 4.)" 
>>
>
> <<<< 
>
>   also the examples in section 4.) 

Yes, this kind of guidance is what I believe is needed.    

James

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