How do cups filters work

[raith at hlrs.de]

Can anybody give me a hint where I find documentation about
how the filtering works in CUPS step by step.

I defined a Nashuatec Postscript Printer (NRGD3545) using their PPD File in CUPS. On WINDOWS I use the driver they supply. If I send the printjob from WINDOWS I get the error message printed on the NRGD3545:

ERROR: undefined
OFFENDING COMMAND: @PJL

STACK:

I did the following testing:

1) Printed my documment to a file on Windows and used lpr to send this file to the the NRGD3545. Perfect printout!!
2) Stopped the NRGD3545 printer queue on the CUPS server and print the
same document to the CUPS server. Compare the queue file and the    Windows local file. No difference!! Use lpr to send the CUPS queue file
directly to the printer. Ups ERROR like obove. Use lpr -oraw instead.
Perfect printout. From CUPS error-log I can see that pstops is used to
print the file.


the file in question looks like:

%-12345X at PJL JOB
@PJL ENTER LANGUAGE = POSTSCRIPT
%!PS-Adobe-3.0
%%Title: Microsoft Word - Dokument1
%%Creator: PScript5.dll Version 5.2.2
%%CreationDate: 4/12/2005 15:23:43
%%BoundingBox: (atend)
%%DocumentNeededResources: (atend)
%%DocumentSuppliedResources: (atend)
%%DocumentData: Clean7Bit
%%TargetDevice: (NRG 3545/3518/3532 PS3) (3011.103) 2
%%LanguageLevel: 3
%%EndComments

the first char is 0x1E = escape

If I edit the queufile and delete the first two lines. Perfect
printout.

CUPS error-log says somewhere:

[Job 11] Page = 595x842; 12,12 to 583,830
D [12/Apr/2005:19:31:21 +0200] [Job 11] Skipping PJL header...
D [12/Apr/2005:19:31:21 +0200] [Job 11] slowcollate=0, slowduplex=0, sloworder=0
D [12/Apr/2005:19:31:21 +0200] [Job 11] 0 %%Title: Microsoft Word - Dokument1^M

It seems that this is not done properly. The filter does not work
how it is expected. As I do not know how these filters work or what
else happens I am stuck here. I hope that more experienced users can
help me or tell me where to find help.

regards

Dieter