IFX Mail Archive: IFX> FW: Suggestions for draft-ietf-fax-ti

IFX Mail Archive: IFX> FW: Suggestions for draft-ietf-fax-ti

IFX> FW: Suggestions for draft-ietf-fax-tiff-fx-Extension-1-02.txt

From: McIntyre, Lloyd (Lloyd.McIntyre@pahv.xerox.com)
Date: Tue Jul 31 2001 - 17:18:23 EDT

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    Terry,
    Thanks for your review and comments.

    1. E1.2.1.3. New Fields, GlobalParametersIFD
    We do not believe there is much ambiguity as to which fields a reader needs
    to look for within the GlobalParametersIFD.
    First, the GlobalParametersIFD definition further restricts the fields by
    stating that the legal set is listed within TIFF-FX or a TIFF-FX extension.
    "Fields in the GlobalParametersIFD MAY be TIFF fields that are legal
     in any IFD. Only a limited number of fields are designated as
     belonging inside the GPIFD, and they are specifically mentioned by
     RFC XXXX or an extension when they do."

    Second, the "SHOULD" recommendation is considered very strong with potential
    interoperability consequences if ignored. It does, however, leave the door
    open for other actions should a compelling situation arise. The SharedData
    field is one example of a field that is required for proper interpretation
    of a data stream, yet it is located within the GlobalParametersIFD. If the
    TIFF-FX GlobalParametersIFD constraint were MUST rather than SHOULD, the
    TIFF-FX extension would not have been able to include SharedData.

    2. TIFF-FX Section 8.2.1 NewSubFileType fields
    The NewSubFileType field definition appears to be clear enough, as each
    SubIFD is NOT a page, so Bit 1 doesn't make sense on a SubIFD. A reader
    could ignore that bit if it appeared on a SubIFD, without changing the
    meaning of anything. As you have pointed out, the Section 8.4 rules do
    clarify this further.

    3. E1.4.5 Rules and Requirements for Images
    We agree with your clarification recommendations. The 5th sentence of Rule 8
    has being change to read:
    "When the image or coding parameters change between stripes in the
     foreground/Background/secondary mask layers these stripes SHALL
     be stored in separate single-stripped IFDs."

    4. E1.4.1 typos
    Done.

    Regards,
    Lloyd

    -----Original Message-----
    From: Terry Stewart [mailto:terryandlori@earthlink.net]
    Sent: Monday, July 30, 2001 1:00 AM
    To: ietf-fax@imc.org
    Subject: Suggestions for draft-ietf-fax-tiff-fx-Extension-1-02.txt

    Hi All,
     
      Below are suggestions for draft-ietf-fax-tiff-fx-Extension-1-02.txt.
     
    Terry Stewart
     
    ============================================================================
    ====
     
    E1.2.1.3. New Fields, GlobalParametersIFD Field:
     
    The current wording regarding the GlobalParametersIFD contains the sentence:
     
       "Required baseline fields should not be located in the
        GlobalParametersIFD, but should be in each image IFD."
     
    The "should" in this sentence appears to be a suggestion only and a TIFF
    writer could place required baseline fields in the GlobalParametersIFD
    and still be considered a valid TIFF-FX file. This means that TIFF-FX
    readers would need to handle the cases where TIFF-FX writers decided to
    ignore the suggestion and place required fields into the
    GlobalParametersIFD.
     
    It is ! my! understanding that the GlobalParametersIFD should never contain
    fields that would directly affect the rendered image (e.g. Photometric
    Interpretation, ImageWidth). Therefore, it would be better to enforce
    this by declaring that the GlobalParametersIFD must not contain required
    baseline fields.
     
       "Required baseline fields MUST NOT be located in the
        GlobalParametersIFD, but should be in each image IFD."
     
    This would remove ambiguity about the intended use of the
    GlobalParametersIFD
    and reduce the complexity of TIFF readers. Otherwise a tolerant TIFF reader

    would have to treat the GlobalParametersIFD as a type defaulting mechanism
    for
    required baseline TIFF fields since the GlobalParametersIFD would need to
    be checked when IFDs are missing required baseline fields.
     
    ============================================================================
    ====
     
    The definit! io! n for NewSubFileType in Section 8.2.1 is:
     
       NewSubFileType(254) = 16, 18. LONG
          For Profile M, the NewSubFileType field has two bits that are
          required. Bit 1 indicates a single page of a multi-page document
          and must be set for the Primary IFD; Bit 4 indicates the MRC imaging
          model as described in ITU-T Recommendation T.44 [T.44], and must be
          set for Primary IFDs and all MRC-specific child IFDs.
     
    This definition allows Bit 1 to be on for MRC-specific child IFDs. I believe

    the description in Section 8.4 "Rules and Requirements for Images" cla! ri!
    fies
    that the child IFDs must not set bit 1 on, but it would be clearer if
    the definition of NewSubFileType mentioned this as well:
     
     NewSubFileType(254) = 16, 18. LONG
          For Profile M, the NewSubFileType field has two bits that are
          required. Bit 1 indicates a single page of a multi-page document
          and must be set for the Primary IFD and MUST NOT be set for
          MRC-specific child IFDs; Bit 4 indicates the MRC imaging
          model as described in ITU-T Recommendation T.44 [T.44], and must be
          set for Primary IFDs and all MRC-specific chil! d ! IFDs.
     
    ============================================================================
    ====
    E1.4.5. Rules and Requirements for Images
     
    The current description of multi-stripped IFDs for non-Primary IFDs is
    currently described as follows:
     
       8. In MRC Internet Fax, each layer is transmitted as a sequence of
                 :
          single Primary IFD as a series of corresponding strips. Without
          constraint on coding parameter changes, all stripes of the
          foreground/Background/secondary mask layers SHALL be stored in
          separate single-stripped IFDs. These IFDs are referenced by the
     
                  :
      10. When there are no image and coding parameter changes be! tw! een
          stripes, a single multi-stripped IFD (i.e. each strip
          corresponding to a stripe) MAY be used to represent a multi-
          striped layer that! is not a Primary Mask layer.
     
    The phrase "Without constraint on coding parameters changes" in item 8
    wasn't very clear to me. Recommend clarifying this area of 8 with the
    following:
     
      8. In MRC Internet Fax, each layer is transmitted as a sequence of
              :
          single Primary IFD as a series of corresponding strips. When
          the image or coding parameters change between stripes in the
          foreground/Background/secondary mask layers these stripes SHALL
          be stored in separate single-stripped IFDs. These IFDs are
     ! &n! bsp; referenced by the ...
     
    ============================================================================
    ====
    Typos:
     
    E1.4.1 Introduction, last paragraph:
     
       "in-dept" should be "in-depth"
    ============================================================================
    ====



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