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Old 01-11-2020, 08:15 AM   #14
jxall began at the beginning.
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Posts: 34
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Join Date: Jan 2020
Device: Kobo Clara HD (patched-100% kepubs); Calibre 4 (Win10)
OK, I just conducted some tests.
  1. I downloaded the .epub and the .kepub.epub editions of David Copperfield from Standard Book website. I'll call these files E and KE.
  2. I copied-pasted E and KE to the Kobo main folder.
  3. I duplicated the original E file, added it to Calibre library, and converted it to .kepub.epub via KoboTouchExtended and sent it to Kobo. I'll call this file E>KE.
  4. I duplicated the original KE file and added it to Calibre. Calibre detected it as an epub, so I had to convert it to .kepub.epub via KoboTouchExtended and send it to the device. I'll call this file KE>(E)>KE.
  5. I duplicated the original KE file, shortened its name to .kepub, added it to Calibre library and sent it to Kobo (no KoboTouchExtended conversion took place). I'll call this file K.

[Please note that in KoboTouchExtended driver I ticked "Cleanup ePub markup" and "Hyphenate Files". I have always kept those configurations like that because the developer himself prefers them to be ticked.]

Then I opened all these files on my Kobo one after another. I didn't change font and any other settings - and started to take pictures to them. Then I used the pictures to visually compare the formatting of the same bunch of pages.

Here are the comparative results:
  • The text from E - as it happens with any epub file - looks a lot bigger than the text from kepub files, using the same nominal font size.
  • KE and K are identical.
  • E>KE and KE>(E)>KE are identical between themselves, but they have a noticeably different formatting from KE and K, taking up more lines per page.

So, Standard Books kepubs are indeed optimized and they do require the manual editing .kepub.epub > .kepub) in order to work in a Calibre library. I guess I'll really a tool to do that in big scale.

Many thanks @JSWolf and @DNSB for the help.

Originally Posted by davidfor View Post
Not at the moment. KoboTouchExtended generates kepubs when sending books to the device. kepubify is really about doing the same thing. But the author has state he will add an option to generate the name as .kepub.

Why would it? Kepubs are only used by Kobo ereaders. There is very little reason to keep a copy of them in the library. If you do get one from elsewhere with the extension as .kepub.epub, then it can safely be treated as an epub for just about everything.

And calibre is designed to be extensible using plugins. All the necessary plugins to support kepubs for those who want to store them exist. Just install them. The only issue is you need to drop the .epub from the name.
Thanks for pointing out about the upcoming feature in Kepubify.

Even if I do understand the general sense of your answer, kepubs have been around for a while. AZW3 are Amazon-specific files just like KEPUBS are Kobo-specific files, so - considering that both formats have been around for many years now - why do AZW3 files have native support and KEPUBs don't?

Kobo is the 2nd most popular producer after all. And as I have shown, it is very useful for backup-restore / practical reasons to have Standard Books' native kepubs in Calibre library instead of epubs in my library.

Couldn't you try to normalize this situation through your plugins? (Allow Calibre to recognize .kepub.epub files just like .kepub files?
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