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Re: Does anyone know how to configure a Brother MFC-J5720DW with cups?

On Sun 13 Mar 2016 at 19:32:04 (+0000), Brian wrote:
> On Sat 12 Mar 2016 at 23:43:27 -0600, David Wright wrote:
> > On Sat 12 Mar 2016 at 09:56:37 (+0000), Brian wrote:
> > 
> > > The PDL of choice for AirPrint capable devices is PDF. A PDF document
> > > sent to an Airprint capable printer is converted to BUL (the Brother
> > > Unknown Language) as it would be if it was processed on a workstation by
> > > CUPS.
> > > 
> > > Note that this is a conversion, not an interpretation. An interpreter
> > > produces a raster image and this happens later when the RIP deals with
> > > BUL.
> > 
> > So you appear to be saying that what passes through the AirPrint wire
> > or wifi link is a PDF. The printer then converts it to BUL, then raster.
> The file type sent by Safari (say) from an iOS device is controlled by
> Apple. Observation shows it is PDF.

If you say so. I haven't observed anything as I don't have one
(neither iOS nor whatever is at the other end of the communication).

> > > The important word is "direct". The MFC-J5720DW doesn't have a  PDF
> > > interpreter. Hence the silence.
> > 
> > So if a PDF arrives by AirPrint, how does the MFC-J5720DW interpret it
> > if it doesn't have a PDF converter? (I am genuinely ignorant and confused.)
> I've said specifically it has a PDF converter. It must have; the printer
> does not understand PDF.

Once again, I don't understand this statement because I don't
understand your terminology...

My question with pronouns removed: "So if a PDF arrives by AirPrint,
how does the MFC-J5720DW printer interpret the PDF if the MFC-J5720DW
printer doesn't have a PDF converter?"

Your response AIUI with pronouns removed: "I've said specifically the
MFC-J5720DW printer has a PDF converter. The MFC-J5720DW printer must
have; the MFC-J5720DW printer does not understand PDF."

Is that what you mean to say? If not, couuld you replace the
appropriate nouns by different nouns.

> > I'm used to this:
> > 
> > Paper -> scanner -> PDF containing image -> [...wifi...] -> computer
> > 
> > where the PDF is really just a container with an image in it.
> > And then its converse (but not its inverse):
> > 
> > Computer PDF -> CUPS -[convert]-> BUL -> [...wifi...] -> BrotherPrinter -[RIP]-> paper
> > 
> > where the Computer PDF contains some postscript-like code mixed
> > in with fonts etc which has to be "converted".
> > 
> > So now with AirPrint we have:
> > 
> > Phone PDF -[no-driver]-> [...wifi...] -> AirPrint -[convert]-> BUL -[RIP]-> paper
> > 
> > Linux computer PDF -> CUPS -> [...wifi...] -> AirPrint -[convert]-> BUL -[RIP]-> paper
> That last line is not correct for using Debian CUPS with an iOS device.

That last line wasn't intended to represent my thinking on how an iOS
device would be handled. "Phone" is the iOS device, as shown in the
_previous_ line.

> The process is:
> iOS device -> CUPS (BUL out) -> Printer -> Print
> With CUPS the process is:
>             This is done by CUPS
> +------------------------------------------------+
> | Input file -> convert to PDF -> Convert to BUL | -> Printer does something
> +------------------------------------------------+
> Because the sending device is driverless all I am saying (I have no
> special insight) is that with Airprint we have:
>                                  Done on the printer
>                            +------------------------------------------+
> iOS device -> Sends PDF -> | Convert to BUL -> Printer does something |
>                            +------------------------------------------+
> One filtering stage has to be moved to the printer. I do not know how it
> is done but it reasonable to guess the same method which CUPS uses is 
> also used. What I am sure about is that there is no PDF interpreter on
> the printer. Brother already have the technology to convert from PDF to
> BUL and, as a practical point, an interpreter would raise the cost of
> production of the printer.
> Substitute PS, PCL, QPDL etc for BUL to see how other manufacturers 
> might deal with AirPrint.

None of your examples (the bits -> like -> this) have "AirPrint"
mentioned in them. I'm trying to learn from you what AirPrint is and
what it does. And yet your statements about it say things like
"The AirPrint facility handles a PDF (it has to)." and "Substitute PS,
PCL, QPDL etc for BUL to see how other manufacturers might deal with
AirPrint." which tell me nothing specifically about AirPrint.

> > but what does the backend of CUPS have to do? Why not just
> > cp ~/my-file.pdf dnssd://Brother%20Printer...
> > if you're not bothered about queueing/scheduling etc.
> The part played by what is in the Bonjour broadcasts is crucial to the
> whole thing working. Apart from the questionable use of cp, IPP is used
> for printing and is what is advertised in the broadcasts.

OK. I can see that CUPS has some work to do to find the printer with
whatever it uses (dnssd/avahi/bonjour/...). That part doesn't really
interest me in this discussion.

> The CUPS backend converts PDF to BUL.

Why bother? The AirPrint technology built into the MFC-J5720DW printer
can do that. Why can't CUPS send PDF down the wire to the printer,
thereby avoiding all the driver-crap? You've just said "The AirPrint
facility handles a PDF" (requoted above). Why not let it do so?

> But, as it happens, you do not
> need cupsd to print to an AirPrint printer.

OK. What's the minimum that you _do_ need? By minimum, I'm meaning
things like drivers; the things that linux users get tripped up by;
the things that make "perfectly functional" printers into doorstops.


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