Re: Reverse-engineering CD printing on the Epson R300

   From: James Cort <jim@xxxxxxxxxxxxxxxx>
   Date: Tue, 20 Jul 2004 13:04:16 +0000

   I have finally got a Windows box, a Linux box, Epson's CD printing software 
   and a Stylus Photo R300 all in one room, and have taken a quick peek with 
   hexedit.

   This situation can persist indefinitely if needs be.

   I've got 3 sample printouts - one with black text, one with coloured text 
and 
   one with a picture background covering the whole CD. They are at:

   http://www.whitepost.pwp.blueyonder.co.uk/printcd_picture_background
     (look out, this one's about 13MB)
   http://www.whitepost.pwp.blueyonder.co.uk/printcd_text_black
   http://www.whitepost.pwp.blueyonder.co.uk/printcd_text_multicolour

   I can confirm Robert's observation - there is an SN instruction
   near the top of the file which appears significant. Changes to this
   instruction cause the printer to print absolutely nothing at all.

   Understanding it that closely for CD printing may not be too
   important, however, as it doesn't seem to vary much between very
   different prints.  Between 0x98 (start of SN instruction) and
   0x145, all three files are identical.  I doubt the whole 173 bytes
   are related to the SN instruction, though I daresay anything's
   possible.

The "SN" is followed by two bytes (little endian short) counting the
number of bytes following that are part of the command.  So for
example

SN 3 0

would be followed by 3 more bytes of payload.  Again, the escputil
command that's part of Gimp-Print is your friend, much more useful
than hexedit.  SN in particular seems to be somewhat of a catchall
command.

I would expect that all prints to CD's using the same parameters (BW
vs. color selected, for example) would use the same extended SN
command.  However, different choices of margin, print speed, and so
forth would likely cause variations in the command, which may be
significant.

-- 
Robert Krawitz                                     <rlk@xxxxxxxxxxxx>

Tall Clubs International  --  http://www.tall.org/ or 1-888-IM-TALL-2
Member of the League for Programming Freedom -- mail lpf@xxxxxxxxxxxx
Project lead for Gimp Print   --    http://gimp-print.sourceforge.net

"Linux doesn't dictate how I work, I dictate how Linux works."
--Eric Crampton


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