[IPP] Discussion on IPP FaxOut

[IPP] Discussion on IPP FaxOut

[IPP] Discussion on IPP FaxOut

Michael Sweet msweet at apple.com
Thu May 30 14:56:56 UTC 2013


Since we are in PWG Last Call, these would be great as last call comments, but my responses are inline...

On May 30, 2013, at 10:40 AM, "Petrie, Glen" <glen.petrie at eitc.epson.com> wrote:
> All,
> I have not had the cycles to review the IPP-FaxOut specification until now and was greatly surprised at the some of the requirements and specification.  
> For example "IPP FaxOut Jobs MUST be retained for a minimum of 300 seconds"

Job history in order for the client to know the disposition of the job (there are already legal requirements for retaining fax history longer than this anyways)

> , "Printers [IPP FaxOut Service???] MUST support scaling and color space conversion of document data to match the negotiated facsimile image format at the job processing time"

If the IPP Printer reports color fax support, the client may send a color document to fax.  But if the receiver does not support color fax we want the IPP Printer to send it B&W unless ipp-attribute-fidelity and print-color-mode are specified to force color fax.

> , and "Imaging Devices [IPP FaxOut Services???] that can only stream print jobs to a single destination URI MUST support retransmission of the current page".  

Retransmission of the current page is a basic fax protocol requirement; all MFDs I know of can buffer at least 1 page of fax data, and most buffer a lot more...

> There are many of these types of requirements that appear to be Client and/or the Imaging Devices "product/implementation design specifications" and not what I expected to be API interfaces capability and job submission specifications.

We did have a lot of discussion about that last year, which resulted in all of the language to support low-end MFDs that could only buffer a single page and could not handle full retransmission.

> For instance, the IPP FaxOut Service should be provide capability on "Job Retention times supported", "Fax Scaling Supported", "Color Spaces Conversion Supported" and "Retransmission Supported" versus this specification setting device and client design and implementation requirements for these capabilities.

As I mentioned above, legal requirements for fax vary but basically all of them require a retained job history far longer/larger than 300 seconds (5 minutes).

The Printer reports its supported scaling/colorspace conversion capability by reporting whether it supports color and what PWG Raster resolutions and types it supports.  And a fax-capable MFD already has to support scaling (to the negotiated resolution) and probably dithering and colorspace conversions from its scanner.

> An example of the simplest fax out would be something like "no-cover, single-sheet, one-recipient, (jpeg) image – to – fax binary CCITT Encoding, no-retry, no-job-hold-after".  Anything beyond that should be based on the capability of the specific IPP FaxOut Service implementation and/or the Client implementation but independent of a "MUST" requirement of the PWG / IPP FaxOut Service specification.   However, the PWG / IPP FaxOut Service specification must define how capability information is specified.

The only required format is PWG Raster, which has several attributes that describe the supported resolutions and color spaces.

Michael Sweet, Senior Printing System Engineer, PWG Chair

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