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Originally Posted by jackie_w
The kepub page count is not too bad as long as you set 'Display progress for: Entire book'. It seems to be consistent cross other Kobo eink devices, regardless of screen-size, font, line-spacing etc.
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Between the Kobo ereaders it works well.
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Not consistent with other eink brands or 3rd-party Android reading apps, though, where the Adobe page count is the only real contender for epubs.
I'd really like to know what algorithm Kobo use. Have you ever been able to delve deep enough into the firmware to find out more?
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I've never looked. I originally assumed it was similar to the Adobe algorithm. It could be exactly that as, from memory, it produces higher numbers than for the equivalent epub. All the extra spans should mean page count using that. But, after a quick experiment, it appears to be based on the word count.
What I did was to put two copies of an epub on my Glo. One I named with the extension .kepub.epub so that it would be opened with the kepub render but not have the no spans. So, both copies were identical. When I opened them, the epub version showed 230 pages and the kepub viewer showed 256.
Because I know the kepub viewer calculates word counts for each chapter to use for the chapter graph, I have wondered if the word count was used for the full book page count. So, I went into the database and for the pseudo-kepub version, changed all the word counts to 10. When I opened the book, it had 40 pages. And the bars in the graph were all the same size.
That tells me the kepub full-book page count is from the word count. But, I don't know what the calculation is. After my fiddling, the total word count is 390. 390/40 means 9 words per page. Far to small. But there are 40 records for the book with zero (the title page) or more words. That I think explains the page count.
The unadulterated version has 79184 words (77242 words according to the Count Pages plugin). That would be 309 words per page. A quick search on the web suggests between 250 and 300 words per page for a paperback. And as they probably calculating pages per chapter and adding them up, 300 sounds a likely number. And setting the word counts to 300, I still have 40 pages. But, I set one copy to 301 words, and another to 600. And I had 40 and 79 pages. A bit more experimentation, and it looks like the change is between 475 and 500 words per chapter to go from 40 to 79 pages. But, 750 is still 79 pages, and 800 words per chapter gives 118 pages (cover plus three pages per chapter). There is an inconsistency there, so either it is not a straight number of words per page (possible), or I made a mistake in my testing (probably).
In any case, the full-book page count for kepubs is looks to be based on the word count. Somehow.
For completeness, the page count for the same book in other ways:
- calibre viewer: 447
- Count Pages - ADE algorithm: 230
- Count Pages - Paragraphs (APNX Accurate) : 265
- Kobo store - 280
- The kepub from the store - 256 (same as the epub when treated as a kepub!)
- Goodreads - 240 (Paperback and Kindle. Other editions don't have a page count)
@cabal2000: The above was done because of @jackie_w question and my curiosity (I suspect someone knew exactly what would happen). But, it demonstrates why I am asking how you know what is wrong. And without that, we can't say how to fix it.
Now, I might go and read. And try not to count the words on the screen.