Quote:
Originally Posted by kovidgoyal
You might want to look at the list of mapping from numbers to attributes used in MOBI and EXTH headers the mapping in kfx might re-use that. There is a partial list in the mobileread wiki and a more complete list in the calibre source code.
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As far as I can tell KFX is not making use of the EXTH codes used by previous kindle formats. I tried to see if the EXTH values made sense as identifiers in the new format, but I haven't come across any overlap in defined EXTH codes and the KFX ids I see in use. I suspect that they deliberately chose the new values to not conflict.
The identifiers in use by KFX appear to be grouped into ranges. Values less than 100 relate to the DRM/voucher system used to protect the main book contents. Scattered ranges of values from 150 to about 500 seem to hold book metadata. And higher numbers appear to be dynamically assigned to individual book resources, such as images.
Of course I don't know what is inside the main KFX book file due to its encryption. EXTH codes might still be present there, but I doubt it. The bulk of the metadata appears to be placed in the auxiliary KFX files in the SDR directory.