[edit: After posting this I may have answered my own question - see the following post].
Another question about the Calibre Viewer.
I notice that it will not open the _CyBook Gen3 User Guide_, instead returning an error message that the Book is protected by DRM.
This is an electronic document in Mobipocket .prc format which can be freely downloaded from the bookeen website.
As noted here
https://www.mobileread.com/forums/showthread.php?t=15960
http://bookeen.free.fr/bin/CybookGen...rGuide_1_0.prc
I would have thought that it can't be protected by normal mobipocket DRM, as it isn't locked to limited number of devices - I think that this same version of the User Guide can be read by any Cybook's customised version of the mobipocket reader, and by anyone's Windows Desktop/Notebook version of the Mobipocket Reader - (it can on the computers I have tried it on).
I was wondering if it might be in the high compression mobipocket file format, as described here
https://wiki.mobileread.com/wiki/MOBI
"However there is also a high compression version of this file format that compresses data to a larger degree in a proprietary manner. ... The higher compression mode is using a huffman coding scheme that has been called the Huff/cdic algorithm. For a description in python check huffdic.py available as part of the Calibre project. "
But the above suggests that Calibre does support books in that variant of the Mobipocket format, or am I misunderstanding the Wiki ?
To satisfy my curiosity, would someone expert at decoding the headers of Mobipcket fomat files say if the Cybook manual is actually compressed or DRMed, or just has wrong headers ?
And is this indeed a version of a mobipocket file that Calibre can't open,
or is Calibre wrongly saying it can't open it ?
Thanks
Martin.