EPUB metadata not read on Kobo devices

[SunshineFish]

I've developed a library to create epub files from collections of images (source code at https://github.com/Aftnet/CPubLib if anyone's interested).

The files generated are epub3 compliant (validator passes them) and so far work as they should on
- Edge on Windows 10
- iOS and macOS's Books app
- Lithium on Android
- Kobo app on Android

Kobo devices however ignore some metadata: cover and, more importantly, chapters index.

Is this a known issue with Kobo ereaders? Any chance of getting them to fix it?

If anyone wants to test for themselves, here (https://drive.google.com/open?id=12e...Fgg75qQuRBe1ZI) is a sample. It has a cover and a chapter for each page.

P.S. For those asking why bother making this vs just using CBZ/CBR, those formats are not supported by native (as in, built into the OS) apps on any platform and they do not have metadata, making organization a pain on Kobo devices.

[davidfor]

I don't see any issues with the metadata or cover. When I sideloaded the book, the metadata was read and the cover is the first page. Kobo is only handling the comments, publisher, title and author. It doesn't read the tags. The ToC didn't work. I think that is because it is an epub3 and there is no NCX to fallback to.

Sideloading as a kepub (rename to use ".kepub.epub" as the extension) and it all works. The kepub renderer handles epub3 better than the RMSDK based renderer used for epubs.

Another difference in the epub and kepub handling is the cover. For epubs, Kobo renders the first page of the book and uses that. For kepubs, it looks for an image with the appropriate properties in the OPF. The yellow image with the word "Cover" has these properties.

If you want to use CBR/CBZ and you use calibre, my Kobo Utilities plugin can set all the metadata correctly once the book has been imported on the device. It will do this for any book format. You send the book to the device, disconnect and let the import happen. Then connect and use the plugin.

[Terisa de morgan]

Too late to answer (better answer over this message)

[jcn363]

cover -> You don't mark any file as cover (usualy the first one, but...).
Calibre's solution:

Spoiler:

    <item href="0b393e09-d459-4110-8060-6b13a25c539c.xhtml" id="p_0b393e09-d459-4110-8060-6b13a25c539c" media-type="application/xhtml+xml" properties="calibre:title-page"/>

chapters index -> You don't create a toc.ncx as davidfor said before.
display: flex; -> consider adding -webkit-display: flex;
object-fit: contain; -> perhaps object-fit: cover;?
I like Calibre's solution:

Spoiler:

 <div style="page-break-before:always; page-break-after:always; page-break-inside:avoid">

      <svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" version="1.1" width="100%" height="100%" viewBox="0 0 420 600" preserveAspectRatio="xMidYMid meet">
        <image width="420" height="600" xlink:href="64798ac2-16c4-4c81-9414-85953e2b8e0b.png"/>
      </svg>

    </div>

I prefer rotated images. Two-scale images are pretty... well, I dislike them.
Good luck.

[SunshineFish]

You guys are seriously awesome.

I'm going to give your solutions a shot as soon as I can.

A couple of questions for jcn363

Originally Posted by jcn363

properties="calibre:title-page"

How does that help? That is definitely not part of the epub standard.

Originally Posted by jcn363

You don't create a toc.ncx

I thought toc.ncx was deprecated in epub3 and one was meant to use nav.xhtml instead. Wrong?

Finally, what are two-scale images? You mean images with a modified aspect ratio from their native one (stretched)?

[davidfor]

Originally Posted by kaworu1986

You guys are seriously awesome.

I'm going to give your solutions a shot as soon as I can.

A couple of questions for jcn363



How does that help? That is definitely not part of the epub standard.

Actually, it is part of the epub standard. They are flexible in how things are represented in properties. Some are general properties, and others are in specific namespaces. This is a calibre property. Everything else will probably ignore it. From my understanding, what you have defined is correct for epub3. The following defines which is the cover image:

properties="cover-image"

I thought toc.ncx was deprecated in epub3 and one was meant to use nav.xhtml instead. Wrong?

The toc.ncx is deprecated in epub3, but, is still supported for backwards compatibility. There are still plenty of epub2 only devices and apps out there that need it. The RMSDK based epub renderer in the Kobo devices is one of them.

[jcn363]

Originally Posted by kaworu1986

You guys are seriously awesome.

I'm going to give your solutions a shot as soon as I can.

A couple of questions for jcn363



How does that help? That is definitely not part of the epub standard.



I thought toc.ncx was deprecated in epub3 and one was meant to use nav.xhtml instead. Wrong?

Finally, what are two-scale images? You mean images with a modified aspect ratio from their native one (stretched)?

The first part is answered by David.
The second one. Two-scale image is an image with two different scales, one for horizontal and a different one for vertical. I mean, I like proportionality.
Good luck.