[cups] Printing 2 copies on a double sided printer

[Johannes Meixner]

Hello,

only FYI some background information about what is called "copies":

There is no such thing as "printing copies".

There are several essentially different ways how one could get
the same content printed multiple times (vaguely called "copies"):

E.g. when printing 3 "copies" it can be done as follows:

# lp -d queue -n 3 file_to_print

(one print job where number of copies is only a print job parameter
  and then it depends on various conditions what exact behaviour
  that print job parameter results - a filter may produce multiple
  pages or the printer may do it or both so that one gets 9 pages)

versus

# lp -d queue file_to_print file_to_print file_to_print

(one print job with the content file as many times as number of copies
  which I consider as the most reliably way how one could get the same
  content printed multiple times for the price of more needed resources
  cf. RFC 1925 item 7a)

versus

# lp -d queue file_to_print
# lp -d queue file_to_print
# lp -d queue file_to_print

(as many separated print jobs as as number of copies where it can happen
  that other user's print jobs get in between so that the jobs from the
  other users appear in between in the whole printout plus maximum
  needed resources how to get the same content printed multiple times)

Those are the three essentially different ways how one could get
the same content printed multiple times (vaguely called "copies")
where each way could result different unexpected behaviour.

When the number of "copies" is only a print job parameter
one can get the same content printed N or N^2 or N^3 ... times
depending on how often that print job parameter is evaluated.

When one gets N^2 "copies" only with some kind of printer models
the reason is likely that first a CUPS filter makes copies
and then the printer itself also makes copies.

Inspect the PPD file of the printer /etc/cups/ppd/<queue>.ppd
if there are some kind of copies options therein and if yes
it may help to play around with that options in the PPD file.

Another issue related to "copies" is "collated copies":

Collated copies means that when printing more than one copy
of a multi-page document it will print all pages of each copy
before printing the next copy.

So the printed page numbers for printing 2 collated copies
of a 3 pages document are
1 2 3 1 2 3
versus printing 2 non collated copies of a 3 pages document
results the following printed page numbers
1 1 2 2 3 3

In particular cheap/weak printers that provide a built-in
copies functionality may support only non collated copies
(e.g. because of too little built-in memory to keep the whole
document to print it as a whole multiple times - but sufficient
built-in memory to print a single page multiple times).

Now put "duplex printing" on top of that and imagine the possible
outcomes when printing 2 collated copies of a 3 pages document
with duplex printing enabled.

One would expect to get this printout
1 and 2 on front side and back side of the first sheet of paper
3 on front side of the second sheet of paper
1 and 2 on front side and back side of the third sheet of paper
3 on front side of the fourth sheet of paper

But one may get that printout
1 and 2 on front side and back side of the first sheet of paper
3 and 1 on front side and back side of the second sheet of paper
2 and 3 on front side and back side of the third sheet of paper

Printing non collated copies with duplex printing enabled
does not make sense because one would get the first page
printed on front side and back side of the first sheet of paper.


On 2020-09-22 17:59, Axel Braun wrote:
> Am Dienstag, 22. September 2020, 17:26:59 CEST schrieb Helge Blischke:
>> > Am 22.09.2020 um 15:02 schrieb Axel Braun <axel.braun at gmx.de>:
>> >
>> > Am Dienstag, 22. September 2020, 10:16:29 CEST schrieb Till Kamppeter:
>> >> On 22/09/2020 10:10, Axel Braun wrote:
>> >>>> lpadmin -p <printer> -o cupsManualCopies=true
>> >>>> or
>> >>>> lpadmin -p <printer> -o default-cupsManualCopies=true
>> >>>>
>> >>>> where <printer> is the queue name of the printer in question.
>> >>>
>> >>> I tried
>> >>>
>> >>> lpadmin -p MFC9340CDW -o default-cupsManualCopies=true
>> >>>
>> >>> before printing from Okular, but that did not fix it.....
>> >>
>> >> It must be
>> >>
>> >> lpadmin -p MFC9340CDW -o cupsManualCopies-default=true
>> >
>> > Unfortunately this still give both copies on the same page.....
>> 
>> What does work in any case is to insert
>> 
>> *cupsManualCopies: True
>> 
>> in the printer’s PPD near the line beginning with *ColorDevice: xxx .
> 
> This hint was mentioned as well in the KDE bug, but did not change the
> behaviour either.

Kind Regards
Johannes Meixner
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