View Full Version : standard on page numbers?


log
01-20-2012, 04:25 PM
Just wondering if there was anything in the epub standard regarding how page numbers are calculated? I've noticed on some epub readers page numbers are the same, while others do not.

For example the same epub has the same page numbers on the following readers:

Sony Reader PRS-T1
Aldiko for Android (phone and tablet)
Adobe Digital Editions (Windows)

Although the same epub has different page numbers on:

Calibre (Windows)
fbreader (Windows)

HarryT
01-20-2012, 04:28 PM
The first group of devices all use Adobe's ADE firmware to display ePub files. This computes pseudo page-numbers using the same algorithm on all devices.

Jellby
01-20-2012, 05:14 PM
There is no standard, there are no "page numbers" in the epub specification. Each software is free to compute (or not) and display (or not) the page numbers in whatever way it sees fit. Some, like Adobe, assign fixed page numbers based on the size of the file; others try to calculate the actual number of screenfuls a given file is going to require in a particular font size and device; others have the option of mapping the page numbers to mimic some paper edition...

HarryT
01-20-2012, 05:17 PM
There is no standard, there are no "page numbers" in the epub specification. Each software is free to compute (or not) and display (or not) the page numbers in whatever way it sees fit. Some, like Adobe, assign fixed page numbers based on the size of the file; others try to calculate the actual number of screenfuls a given file is going to require in a particular font size and device; others have the option of mapping the page numbers to mimic some paper edition...

Is the page map not a part of the ePub standard? I thought that this allowed pages to be assigned to an ePub file to correspond to a printed addition, as can now also be done in Kindle books.

DaleDe
01-20-2012, 08:39 PM
Is the page map not a part of the ePub standard? I thought that this allowed pages to be assigned to an ePub file to correspond to a printed addition, as can now also be done in Kindle books.

There is an Adobe extension but it is not part of ePub. The TOC.ncx file can have a page map in it. This will be allowed but ePub does not support it although Daisy does.

Dale

HarryT
01-21-2012, 04:29 AM
Thanks for the clarification, Dale.

DaleDe
01-21-2012, 01:50 PM
Thanks for the clarification, Dale.
It would have been nice to have the page map supported but instead ePub 3 moves away from the toc.ncx file entirely. Kindle can use the page map as well as the Adobe extension I believe to translate to their apnx file.

huebi
01-22-2012, 07:59 AM
When page map is not available in the document, Adobe Digital Editions will synthesize a page-map based on the document content. The approach used is the following:
Determine a compressed byte length of each resource which is referenced in the spine, subtracting any known encryption overhead (IV size)
Assume that there is a page for each 1024 bytes…

log
01-22-2012, 09:55 PM
Good to know, thanks everyone.