A few questions about metadata and conversion

[sun surfer]

1-Once you change metadata do you need to convert the file to make it stick?

2-Why do identifiers change/revert when you convert?

3-If you have two or more file formats of a book does calibre edit the metadata together or separately?

[eschwartz]

1. No. Metadata is updated at the following times:
   • Conversion. All current library metadata is embedded into the converted book. Metadata embedded in the conversion source ebook is totally ignored.
   • Embed Metadata and Polish book. All metadata that can be updated will be embedded into the library copies. (You can choose to restrict this to specific formats.) Certain types of metadata are not supported by certain formats -- notably, only EPUB and AZW3 support updating covers.
   • Send to device, Send to email, and Save to disk. ^^Ditto for the exported books, except plugboards, if configured, are applied.
   • Edit E-Book by default updates books when saving, following the same rules as Embed Metatdata/Polish book. But most people don't ever use this anyway.
2. Identifiers, like any other metadata, are derived from the library metadata. The only exception I can think of is mobi-asin, which is derived from a mobi header. That header can be set from the amazon|asin|mobi-asin identifier using the Quality Check plugin, which can be useful for things like goodreads/store linking on-device.
3. See #1

[sun surfer]

Thanks again, eschwartz.

Originally Posted by eschwartz

Conversion. All current library metadata is embedded into the converted book. Metadata embedded in the conversion source ebook is totally ignored.

So, for instance, if you change the metadata with an epub, then convert to mobi, the mobi will contain the metadata you changed but the epub won't?

If one book has different formats with different metadata, how can you look at the embedded metadata in the different formats?

Embed Metadata and Polish book. All metadata that can be updated will be embedded into the library copies. (You can choose to restrict this to specific formats.) Certain types of metadata are not supported by certain formats -- notably, only EPUB and AZW3 support updating covers.

This sounds like what I need, and I've found and added them to the toolbar now. It seems like I can use this so I won't have to convert to embed changed metadata.

Send to device, Send to email, and Save to disk. ^^Ditto for the exported books, except plugboards, if configured, are applied.

If I use say send to device will it only embed on the copy being sent or will it also embed on the calibre file?

Identifiers, like any other metadata, are derived from the library metadata. The only exception I can think of is mobi-asin, which is derived from a mobi header. That header can be set from the amazon|asin|mobi-asin identifier using the Quality Check plugin, which can be useful for things like goodreads/store linking on-device.

Here's what's happening with the identifiers- When I download metadata it often provides various identifiers like amazon, etc. However, when I convert, even though the other metadata I'd changed embeds, the identifiers don't and change back to what they were before I'd downloaded metadata (in other words, it erases the ones that had been added).

At least, this seems to be the case. I tested it all by converting, manually moving the new file to a non-calibre location, deleting the book from calibre and adding the new file to calibre as a new book then checking the metadata.

[eschwartz]

Originally Posted by sun surfer

Thanks again, eschwartz.

Sure thing, fire away all you want.

So, for instance, if you change the metadata with an epub, then convert to mobi, the mobi will contain the metadata you changed but the epub won't?

Correct. In fact, it would be more correct to say you changed the metadata for the book record, not the EPUB attached to the book record.

If one book has different formats with different metadata, how can you look at the embedded metadata in the different formats?

You can look at the metadata a couple ways.

You can use the command-line tool `ebook-meta`, but I think we'll skip that one.
You can edit the book (if EPUB or AZW3) and look at the OPF. In XML. I think we'll skip that one too.

Winner:
You can open the book in the calibre ebook-viewer (View --> Choose format), and use the toolbar option "Show book metadata".
You can also just use Embed metadata to make sure it's up to date.

This sounds like what I need, and I've found and added them to the toolbar now. It seems like I can use this so I won't have to convert to embed changed metadata.

That is what it was created for.

If I use say send to device will it only embed on the copy being sent or will it also embed on the calibre file?

Just the copy that was exported.

Here's what's happening with the identifiers- When I download metadata it often provides various identifiers like amazon, etc. However, when I convert, even though the other metadata I'd changed embeds, the identifiers don't and change back to what they were before I'd downloaded metadata (in other words, it erases the ones that had been added).

At least, this seems to be the case. I tested it all by converting, manually moving the new file to a non-calibre location, deleting the book from calibre and adding the new file to calibre as a new book then checking the metadata.

On second thought, I believe identifiers is one of the things MOBI/AZW3 just doesn't really support.
EPUB, on the other hand, supports arbitrary custom metadata types.

Was this an AZW3?

[sun surfer]

Originally Posted by eschwartz

Correct. In fact, it would be more correct to say you changed the metadata for the book record, not the EPUB attached to the book record.

If you are changing the metadata for the book record it sounds like it should change it for all formats of that book but it doesn't so what am I missing here?

You can look at the metadata a couple ways.

You can use the command-line tool `ebook-meta`, but I think we'll skip that one.
You can edit the book (if EPUB or AZW3) and look at the OPF. In XML. I think we'll skip that one too.

Winner:
You can open the book in the calibre ebook-viewer (View --> Choose format), and use the toolbar option "Show book metadata".
You can also just use Embed metadata to make sure it's up to date.

Yes, the winner is more up my alley, thanks.

On second thought, I believe identifiers is one of the things MOBI/AZW3 just doesn't really support.
EPUB, on the other hand, supports arbitrary custom metadata types.

Was this an AZW3?

Yep. That's probably it then. It only seems to keep isbn and mobi-asin and deletes the rest, even the Amazon identifier. The Quality Check plug-in that you suggested will embed the Amazon identifier though, if I've already added it to the metadata, as the mobi-asin.

[eschwartz]

Originally Posted by sun surfer

If you are changing the metadata for the book record it sounds like it should change it for all formats of that book but it doesn't so what am I missing here?

The book record is *just* a row in the calibre library database. It records the metadata that you see in the main GUI, as well as the location and type of any ebook files you have for that book.
You can have a book record without any formats, you know.


When you Edit Metadata in calibre, the database is updated... but Kovid Goyal does not believe that the attached files should be updated as well.
Rationale: don't touch the ebook files, and you won't mess them up if you need the actual original files sometime down the line.

When a file is copied out of calibre, and you will need to read the file with something other than calibre, then at that point you need the updated metadata. But modifying the files can wait until then.


Embed Metadata is the tool used if one wishes to break that assumption... which is usually safe. But you don't really need to bother unless you will be accessing the books through the filesystem.
And that should only happen in limited circumstances, for example if you use calibre2opds (in my signature) or sync your library to dropbox and want to download a book on your phone/tablet through the Dropbox app.
The rest of the time, calibre can handle sending a book to where it is needed.

[sun surfer]

That explains a lot. Thanks eschwartz!