[Conversion Output] KFX Output

[JSWolf]

Originally Posted by phossler

I've got 3.45 on my PC and haven't had any issues with it or the PI

I don't think 3.46 is out yet; at least I haven't gotten a 'New Release Is Available" popup

3.46 is available. I installed it yesterday.

[jhowell]

Originally Posted by carlone2

is it safe to install the latest version of Kindle Previewer 3.46 on a new pc?
Will KFX Output plugin continue to work?

Yes, Kindle Previewer 3.46 will work with the current release of the plugin.

[Terry Brown]

Okay, this is a weird one and may not be related to the KFX conversion at all, but I don't know a better place to start than here.

I am using Calibre 5.1.0, KFX Output 1.44.0, Kindle Previewer 3.45 on macOS Catalina, and a 2018 iPad Pro 12.9 with the latest version of the Kindle app.

I convert and side load KFX files to the Kindle app on the iPad. When viewed using Bookerly (but other fonts as well), there are quality issues. The density of the letters is inconsistent. Hard to describe, but there is a variability in the pixel density of different letters, as if the font were being resampled and averaged for display, and thereby losing information, for example. This causes some letters to appear darker, or perhaps different sizes than others. Very disconcerting on a Retina display.

If I instead use a .mobi file converted in Calibre, I do not see this issue. EPUB files viewed in iBooks do not show the issue. It is specific to the KFX format files.

I also do not see the issue on my iPhone 7. I have tried various fonts and font sizes, themes, etc, but still see the issue on the iPad.

I have attached a screen shot from the iPad. Assuming the resolution is good enough, take a look at the word 'that' in the first line of the right column. The 't' and the 'h' are larger and bolder than other letters.

Take a look at the word 'Narveduen' in the third line from the bottom of the right column. Here, the letters 'uen' at the end of the word are thinner than the others.

Interestingly, I do not see this on my iPhone 7.

Does any of this make any sense? Any ideas about what to try or where to go to get suggestions?

[jhowell]

Originally Posted by JSWolf

If I use Kindle Previewer to preview ePub or KF8 and they are converted to KFX, where is the KFX stored?

The Previewer actually produces KPF, which is a variant of KFX format. It has the same content as KFX except that it is stored in an SQLite database instead of a KFX container file.

The KPF is stored in whatever temp folder your system uses. You can export it to whatever location you like using the File, Export menu options of the Previewer.

[jhowell]

Originally Posted by phossler

I have a calibredb VBS script to copy my database epubs to a single folder in KFX format. Everything works fine unless there's a series. Then there's an extra space that comes from somewhere and messes up the titles in the Kindle index/home page.

The template that you provide in the "calibredb export" command only affects the filename produced. It has no impact on the metadata contained within the exported KFX file. That is controlled by "Preferences", "Metadata plugboards" in the calibre GUI.

Look at the plugboards settings and see if anything there can explain what you are experiencing. If you want to post what you have set there, I can take a look at it.

Originally Posted by phossler

I didn't know any way to view KFX metadata, so this was the best I could do

If you install the KFX Input plugin you can then view the metadata of KFX files using the calibre CLI command "ebook-meta".

[jhowell]

Originally Posted by Terry Brown

OI convert and side load KFX files to the Kindle app on the iPad. When viewed using Bookerly (but other fonts as well), there are quality issues. The density of the letters is inconsistent. Hard to describe, but there is a variability in the pixel density of different letters, as if the font were being resampled and averaged for display, and thereby losing information, for example. This causes some letters to appear darker, or perhaps different sizes than others. Very disconcerting on a Retina display.
...
Does any of this make any sense? Any ideas about what to try or where to go to get suggestions?

I have not noticed anything like that before. It may be a problem with the KFX renderer that only appears on some devices.

Do you have any books purchased from Amazon that exhibit the same behavior?

Could you try converting a public domain book, such as this edition of Frankenstein, and see if it exhibits the same problem?

[phossler]

Originally Posted by jhowell

The template that you provide in the "calibredb export" command only affects the filename produced. It has no impact on the metadata contained within the exported KFX file. That is controlled by "Preferences", "Metadata plugboards" in the calibre GUI.

Look at the plugboards settings and see if anything there can explain what you are experiencing. If you want to post what you have set there, I can take a look at it.

That was it!!

Yea, the calibredb export makes the correct (desired) filename, but I couldn't figure out why the KFX title was off

I didn't remember even having a metadata plugboard, but that was where my mistake was

Thanks for straightening me out

Life is good

If you install the KFX Input plugin you can then view the metadata of KFX files using the calibre CLI command "ebook-meta".

I'll have check that out also

[Terry Brown]

Originally Posted by jhowell

I have not noticed anything like that before. It may be a problem with the KFX renderer that only appears on some devices.

Do you have any books purchased from Amazon that exhibit the same behavior?

Could you try converting a public domain book, such as this edition of Frankenstein, and see if it exhibits the same problem?

I tried the Frankenstein book and it shows the problem. I also downloaded a free book from Amazon https://www.amazon.com/AGATHA-CHRIST...s%2C274&sr=8-4 and it also showed the problem.

Although I am certain that this is a new problem, I am not sure when it began. Some books show the problem, some don't. I checked the conversion dates of the books but found nothing suspicious with respect to version changes of the KFX plugin.

My suspicion is that this is a bug in the Kindle app, or perhaps iOS 14. all evidence indicates it is not a problem with the KFX plugin.

I'm not sure where to go from here.

[jhowell]

Originally Posted by Terry Brown

My suspicion is that this is a bug in the Kindle app, or perhaps iOS 14. all evidence indicates it is not a problem with the KFX plugin.

I'm not sure where to go from here.

The Kindle for iOS app was just updated to version 6.35. Perhaps that will make a difference.

Sorry, I don't have any other suggestions.

[Terry Brown]

Originally Posted by jhowell

The Kindle for iOS app was just updated to version 6.35. Perhaps that will make a difference.

Sorry, I don't have any other suggestions.

Just update. It makes no difference.

[jhowell]

Version 1.45.0 - 23 Oct 2020

Detect Kindle Previewer versions up to 3.47.

Support additional KFX features. (Fixes "Unknown com.amazon.yjconversion feature: reflow-style-13" and "Unknown com.amazon.yjconversion feature: yj_mixed_writing_mode-1")

[donmez]

Is there a way to set the compression value of JPEG compression? It looks like it's set way too high and it creates artifacts on images with text in it.

Also, thanks for this awesome plugin!

[JSWolf]

Originally Posted by donmez

Is there a way to set the compression value of JPEG compression? It looks like it's set way too high and it creates artifacts on images with text in it.

Also, thanks for this awesome plugin!

Set your output profile to Tablet. Calibre will not change the images in any way. If there are any changes, at that point, it's done by Kindle Preview.

[jhowell]

Originally Posted by donmez

Is there a way to set the compression value of JPEG compression? It looks like it's set way too high and it creates artifacts on images with text in it.

As JSWolf wrote the main thing that can reduce image quality is the setting of the "Output profile" which is found in the "Page setup" tab of the conversion dialog. A setting of "Tablet" disables image resizing.

The Kindle Previewer should leave JPEG images unchanged.

[gers1978]

Not had this error before:

calibre, version 5.4.2
ERROR: KFX conversion failed: <p><b>Cannot convert "Book name"
Conversion error: E24010: Hyperlink not resolved in toc (One possible reason
can be that the link points to a tag with style
display:none):/private/var/folders/8f/px1dqgxj2wlg9l51xhcpv22m0000gn/T/396782c4-6ed7-
4a12-a58d-527487f92122/cTemp/mTemp/mobi-n5lQ2o/OEBPS/Cover.xhtml#