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BetterRed · 03-02-2020, 05:57 AM

@stan999 - yonkunior has the nub of it, here's the unabridged version.

The metadata.opf files in book folders are there to facilitate rebuilding (restoring) of the library database if it gets corrupted somehow (metadata.db in library folder). I've been using calibre for nearly a decade and I never had to rebuild a database.

The metadata.opf file in book folders and the .opf files in epubs have similarities but they are not interchangeable and never will be.

IMO, unless you intend round-tripping Saved to disk formats back into a calibre library there is little point in saving the metadata.opf and/or the cover.jpg files with the saved format files. An exception might be if the format you're saving has no (or limited) embedded metadata - e.g. a MOBI or a CBZ.

The cover.jpgs are where calibre gets the images to display in Book details, Cover carousel and grid, Conversion dialogue, etc. Extracting images from format files or the database would make calibre appreciably slower.

BR

03-02-2020, 05:57 AM	#3
BetterRed null operator (he/him) Posts: 21,792 Karma: 30237628 Join Date: Mar 2012 Location: Sydney Australia Device: none	@stan999 - yonkunior has the nub of it, here's the unabridged version. The metadata.opf files in book folders are there to facilitate rebuilding (restoring) of the library database if it gets corrupted somehow (metadata.db in library folder). I've been using calibre for nearly a decade and I never had to rebuild a database. The metadata.opf file in book folders and the .opf files in epubs have similarities but they are not interchangeable and never will be. IMO, unless you intend round-tripping Saved to disk formats back into a calibre library there is little point in saving the metadata.opf and/or the cover.jpg files with the saved format files. An exception might be if the format you're saving has no (or limited) embedded metadata - e.g. a MOBI or a CBZ. The cover.jpgs are where calibre gets the images to display in Book details, Cover carousel and grid, Conversion dialogue, etc. Extracting images from format files or the database would make calibre appreciably slower. BR Last edited by BetterRed; 03-02-2020 at 08:48 AM.