KOReader EPUB opening speed

[_kind_le]

Since I'm having connection issue Kobo <--> macOS and just don't want to restart my laptop or play with cables/type-c hubs each time - I got KOreader installed on my Clara BW in order to use its wireless sync feature with my Calibre library. After loading books some of them had no covers but I was able to resolve that by long pressing on book and selecting "Refresh cached book information".

The main problem I'm facing is one of my books can't be opened (as I thought before). It just hangs and you need to reboot device. To debug that I exported the book from Calibre and realized that it also hangs there while showing "Copying files and writing metadata...". It takes roughly 5-7 min. to finish the process. When doing export of EPUB only - it's blazing fast.

So I tried to go further and check books md5s (per thread where people were complaining about wireless connection to Calibre results in broken files), that was a dead end since md5 of epub saved from Calibre and one that Calibre pushes to device are different. And looks like it's not only true for that particular book. Idk, maybe different filesystems on host OS and device might make that discrapancy.

As final test I installed and used epubcheck tool to validate epub file, here's what I've got:

epubcheck 11_22_63\ S\ King\ \(93\).epub

Validating using EPUB version 2.0.1 rules.
ERROR(NCX-001): 11_22_63\ S\ King\ \(93\).epub/OEBPS/toc.ncx(-1,-1): NCX identifier ("FB2BookID") does not match OPF identifier ("urn:uuid:cc321c08-44af-4ecb-82eb-1b95cb3715db").

Check finished with errors
Messages: 0 fatals / 1 error / 0 warnings / 0 infos

EPUBCheck completed

But another book from the same author/vendor has that error +1 more and works just fine.

So on my last try I didn't want to restart the device and just left it, not sure how long it took but the book was finally opened.

Any advice on what else I can check/tweak? Because Calibre epub viewer/editor opens it, Books app can read it without any issues - I'm running out of ideas what to check next.

[Frenzie]

If you see the same issue after running it through ScrambleEbook, share that.

https://www.mobileread.com/forums/sh...d.php?t=267998

[_kind_le]

Yeah, same problem with the scrambled book. Also this new one version has more epubcheck errors:

ERROR(RSC-007): 11_22_63_scrambled.epub/OEBPS/Text/about.xhtml(28,3): Referenced resource "OEBPS/Fonts/LiberationSerif-BoldItalic.ttf" could not be found in the EPUB.

Check finished with errors
Messages: 0 fatals / 3077 errors / 0 warnings / 0 infos

and cyrillic was replaced with english:



But anyway, Calibre export time is the same (very long and CPU consuming) if select "Save to disk" while "Save only EPUB format to disk" is fast. KOreader is trying to open it for... ~10 minutes already, progress bar is almost in the middle right now.

[Frenzie]

I meant share the scrambled file so the cause can be investigated.

But on average the cause is excessive[1] HTML/CSS.

[1] Diplomatic term.

[JSWolf]

Originally Posted by Frenzie

I meant share the scrambled file so the cause can be investigated.

But on average the cause is excessive[1] HTML/CSS.

[1] Diplomatic term.

I've seen some eBooks with over 100 excess CSS classes. The problem is that a lot of publishers use a house CSS which contains everything they've used. I always remove excess CSS before the ePub going on my Libra 2.

[_kind_le]

Originally Posted by Frenzie

I meant share the scrambled file so the cause can be investigated.

But on average the cause is excessive[1] HTML/CSS.

[1] Diplomatic term.

Oops, I misunderstood you.
Here is a file book_scrambled.tar.bz2

[_kind_le]

Originally Posted by JSWolf

I've seen some eBooks with over 100 excess CSS classes. The problem is that a lot of publishers use a house CSS which contains everything they've used. I always remove excess CSS before the ePub going on my Libra 2.

Which software you're using to modify books? Since I'm not a pro in editing, it will be a challenge for me to find "excess CSS" unless there is some good manual for that

[jonnyl]

Calibre has a built-in 'Polish books' feature which will remove unused CSS. I ran your book through it and it did an impressive job:

### Removing unused CSS rules
Removed 23754 unused CSS style rules
Removed 3813 unused CSS selectors
No unused stylesheets found

It also reduced the filesize by about 400k. HOWEVER, it didn't make opening it in KOReader any faster. I wonder what else might be causing the extreme lag?

There is an easy fix for opening it quickly, though: Convert the book from epub to epub in Calibre. It will then open instantly.

Or alternatively, if you ever don't have access to Calibre, you can long-press on the file in KOReader and select Open with... MuPDF. You won't be able to change fonts, use style tweaks, etc., but it will open without delay.

[mergen3107]

Then probably some images are either too big or not quite compatible with eink framebuffer. Ideal specs is grayscale 8-bit.

One can use scripts from this section for manga:
http://koreader.rocks/user_guide/#L1-manga

[mergen3107]

Extract all images, process them, and put back into the book, replacing originals

[Ebookus]

where can one find said polish feature?

[JSWolf]

Originally Posted by _kind_le

Oops, I misunderstood you.
Here is a file Attachment 221447

You'd be best to post the eBook as just an ePub instead of making anyone who wants to look at it jump through hoops to get the ePub.

[mergen3107]

Originally Posted by Ebookus

where can one find said polish feature?

I believe it is in Editor (Edit a book) window in calibre

[jonnyl]

No, you need to manually add it to your Toolbar (or any other menu of your choice) by going to Preferences > Toolsbars & menus.

[JSWolf]

Select the eBook in calibre and then press T on the keyboard to edit the eBook.