[cups-devel] IPP backend bug

[Michael Sweet]

Johannes,

> On Sep 8, 2015, at 4:31 AM, Johannes Meixner <jsmeix at suse.de> wrote:
> ...
> It seems when printer-specific data is sent via IPP to CUPS
> there is no option for the ipp://... device URI to enforce
> "raw" printing for the receiving queue on the CUPS server,
> at least no such option is described for "IPP" in
> https://www.cups.org/documentation.php/doc-2.1/network.html

The issue is that for IPP we actually get to use MIME media types, and the filters in the PPD file specify what the final output type is.  We then try to match things up on the remote system, which is where the problems typically occur.  For example, if the local driver has a filter that specifies "application/vnd.hp-pcl" as the destination MIME media type but the server does not have that MIME media type defined/supported for its queue, we have to revert to "application/octet-stream" (auto-detect).

You can "fix" this with .types and .convs files on the server (to specify a "-" filter for the affected MIME media types to application/vnd.cups-raw) but ultimately you are better off letting the server do the filtering...

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Michael Sweet, Senior Printing System Engineer, PWG Chair