When does Calibre change ebooks, and why are...?

[derangedhermit]

If I update metadata in an epub in Calibre, is that update immediately applied to the metadata in the epub itself, or is the epub unchanged and the update kept somewhere else until some later time, like "Write to disk' or "Send to Device"?

What about when I download or otherwise change covers? Is the old cover immediately deleted from the epub, or is it retained and the new one marked as an update and stored separately for later? Furthermore, does changing covers actually change what Calibre thinks is the old cover, or is something else going on?

When is a "conversion" (e.g. epub-epub) required to get changes to stick?

Also, the default for writing epubs outside the Calibre library is to have a separate cover page file and a separate ?OPX (some other) file. Epubs don't need these as external files - why is it the default, and what is lost if you set Calibre to just write out the standard epub (zip) file alone?

Last, what specific settings are needed to prevent Calibre from adding its own html (or modifying the existing html) on import, conversion, and export (output)?

I could at least partly answer some of these by exploration, but maybe the answers will be useful to a few other Calibre users.

(I have read what seemed the relevant parts of the help files before asking.)

Thanks,
Lee

[DoctorOhh]

Originally Posted by derangedhermit

If I update metadata in an epub in Calibre, is that update immediately applied to the metadata in the epub itself, or is the epub unchanged and the update kept somewhere else until some later time, like "Write to disk' or "Send to Device"?

Changes are only embedded in the epub upon the book being exported from the library using Send to Device, Save to Disk, email, or content server.

Originally Posted by derangedhermit

What about when I download or otherwise change covers? Is the old cover immediately deleted from the epub, or is it retained and the new one marked as an update and stored separately for later? Furthermore, does changing covers actually change what Calibre thinks is the old cover, or is something else going on?

The cover is the same as any other metadata and is only updated when the book is exported from the library. Sometimes though a book will not have a proper cover identified in it and exporting the book will not update the cover.

Originally Posted by derangedhermit

When is a "conversion" (e.g. epub-epub) required to get changes to stick?

Never, but if for some reason the cover does not "stick" you would be best served by using the Modify ePub Plugin to update the cover.

Originally Posted by derangedhermit

Epubs don't need these as external files - why is it the default, and what is lost if you set Calibre to just write out the standard epub (zip) file alone?

Nothing is lost.

Originally Posted by derangedhermit

Last, what specific settings are needed to prevent Calibre from adding its own html (or modifying the existing html) on import, conversion, and export (output)?

It is probably best to learn about the conversion process by reading this section of the manual.

[BetterRed]

Originally Posted by DoctorOhh

Changes are only embedded in the epub upon the book being exported from the library using ... Save to Disk ...

Save to Disk will embed the latest metadata & cover in the exported ePub, but it doesn't embed the latest metadata & cover in the ePub in the calibre library folder. Well not here at least, it could be I missed a setting - that's happened before, more than once

I don't use Send to Device or Email often, but I think they're the same, never used Content Server so I can't speak to it.

I think the only way to update the ePub in the calibre library folder is to do a conversion, or use the Modify plugin (IMO this is better).

Before I discovered the Modify plugin I was saving to disk, copying that epub back to the library folder, and deleting the save to disk copy

I would like a setting where I could designate a format for auto-update when metadata or cover is changed. I'd like it to be independent of the "Preferred Output Format" setting, because I sometimes 'play around' with that. The default would be None, if the designated format is absent then 'carry on regardless'

BR

[DoctorOhh]

Originally Posted by BetterRed

Save to Disk will embed the latest metadata & cover in the exported ePub, but it doesn't embed the latest metadata & cover in the ePub in the calibre library folder.

Correct, that's what "embedded in the epub upon the book being exported" means, but I guess it could have been said clearer.

Originally Posted by BetterRed

I think the only way to update the ePub in the calibre library folder is to do a conversion, or use the Modify plugin (IMO this is better).

Correct again. Thanks for clarifying this for the folks looking in.

[derangedhermit]

So the ebooks are kept internally in the state they were originally after the "Add books" (or "Get books" I suppose) operation?

There is a statement in the General Discussions forum ("genres" thread) that to get a cover updated for download to device, you have to do a conversion (or use a plugin) - that just "Send to device" doesn't do it (unlike other metadata). I'd like to know for sure since on my last downloads, the cover I got from straight download to the Nook from B&N was different for a number of books from the cover I got by downloading to PC - adding to Calibre (no epub-epub conversion) - sending to device (the same Nook). I'm not sure what's happening there.

My settings are as close to "do nothing" on input, output and epub file type as I can make them. I made these settings changes before adding any books into a new, empty library, to try to avoid all the calibre html and css that got added the first time I tried to build a Calibre library.

[Adoby]

To update the actual contents of a ebook is expensive. It requires the computer to make a copy of the book, unzip it, change the metadata, zip it and finally replace the original copy.

When you are fixing metadata, perhaps in bulk, the metadata may be changed several times. It would slow down Calibre a lot if the actual books had to be changed every time the metadata is updated. Instead most of the changes are only stored in a separate database file that is much quicker and easier to change.

This is why the metadata inside the book only is updated when the book is converted, saved to disc or sent to device.

It is possible to manually request that Calibre update the metadata inside ePub books, using the plugin "Modify ePub".

[derangedhermit]

I've no problem with calibre waiting to update the book. I just want to understand, so I can sort out what I'm doing that causes apparent discrepancies.