Can I disable Calibre adding 50kb to epubs when sending to device?

[Zhaan]

I recently noticed that Calibre has started adding ~50kb to epubs when I send them to my Kobo Glo. I mainly use my reader to read fanfiction that I download as epubs from Archive of Our Own, the majority of them are <20kb and I download fairly large quantities of them, so this is suddenly eating up my space on the Kobo faster than I'd prefer.

I've been working my way back through the Calibre updates, and with the 2.58 release from June 17 a 10kb epub is still 10kb when it appears on the Kobo, but with the 2.59 release the same 10kb epub is now 63kb on the Kobo.

But that's where I'm stuck. I've spent the last couple of days trying to search the internet and reading the threads here, but I just don't understand enough to figure out what's going on. I'm assuming it's related to something in this part about epubs in the changelog from the 2.59 release? (or is something else going on?):

Edit Book: Add support for EPUB 3 to the Table of Contents tool. Now when editing EPUB 3 files using the tool will automatically generate both the EPUB 3 navigation document and the NCX table of contents for backwards compatibility.
EPUB Input: Implement reading of Table of Contents from EPUB 3 files that do not specify a fallback NCX ToC
EPUB metadata: When setting a cover image for an EPUB file that has no metadata cover image defined, add the new cover image as a pure metadata cover instead of aborting.

I'd be so very grateful if anyone had suggestions for how I could disable whatever's going on, or something? My current plan is to just use the 2.58 release indefinitely, but I'd rather find a solution if it's possible. Thanks!

[theducks]

Calibre only sends what you select

AFAIK the only Auto-send is for News (anything added with that tag)
do you have Preferences: Behavior: Automatically Send News... ticked

[PeterT]

Why not help the community out and explode the epubs on the device and your library and see what has changed, or even attach two files to you post so others can look?

[davidfor]

Zhaan: The change that does this is the last of the three you listed. With this, calibre is always adding a cover image into the book even if there currently isn't on. It might not get displayed on a page, but it is there for applications that look for it. In 2.60, an option was added to turn this off:

EPUB metadata: Add an option to disable adding of cover images to EPUB files that declare no cover image in their metadata (Preferences->Plugins->Customize the Set EPUB metadata plugin)

[Zhaan]

PeterT: Sorry, I'd explored the epubs to the best of my ability and they seemed completely identical so I forgot to mention it, but I'll remember to attach the files another time.

davidfor: Thank you so very much! I found the 'Set EPUB metadata' plugin, but then unfortunately when I click 'customize' I get an error message:

ValueError: unmatched '{' in format

calibre, version 2.62.0
ERROR: Unhandled exception: <b>ValueError</b>:unmatched '{' in format
calibre 2.62 [64bit] embedded-python: True is64bit: True
Windows-8-6.2.9200 Windows ('64bit', 'WindowsPE')
('Windows', '8', '6.2.9200')
Python 2.7.9
Windows: ('8', '6.2.9200', '', 'Multiprocessor Free')
Successfully initialized third party plugins: Quality Check (1, 9, 11)
Traceback (most recent call last):
File "site-packages\calibre\gui2\preferences\plugins.py", line 292, in customize_plugin
File "site-packages\calibre\gui2\preferences\plugins.py", line 359, in modify_plugin
File "site-packages\calibre\customize\__init__.py", line 263, in is_customizable
File "site-packages\calibre\customize\builtins.py", line 441, in customization_help
ValueError: unmatched '{' in format

which I'm assuming is some kind of bug? Or am I doing it wrong? But it feels much better to know what's going on, I'll keep working on it. Thanks again!

[kovidgoyal]

That looks like a bug in a translated string, switch your interface language to english and it should be fine. And let me know what the buggy language is.

[Zhaan]

Yes! It's working now, thank you so very much!

I've been using Swedish as my interface language.

[eschwartz]

A quick grep tells me it is probably the one in sv.po

#: /home/kovid/work/calibre/src/calibre/customize/builtins.py:439
#, python-brace-format
msgid ""
"Enter {0}{1}{2} below to have the EPUB metadata writer plugin not add cover "
"images to EPUB files that have no existing cover image."
msgstr "Ange {0 {1}{2} nedan för att få EPUB metadata författare tillägget att inte lägga till omslagsbilder till EPUB-filer som inte har någon befintlig omslagsbild."

EDIT: I have excellent timing today, it seems.