Cover thumbnails for Kindle not being generated

[London Rain]

Hi,

I wondered why some of my books transfered to my Kindle Paperwhite showed no covers on the device but most did.

I use Calibre's send to device feature (via USB) and as format I always chose AZW3. I also made sure that the "Enable sharing of book content option" is ticked for mobi and AZW3.

As far as I understand the user manual Calibre should then create a cover image thumbnail and place it into the Kindle's system\thumbnails folder.

See: https://manual.calibre-ebook.com/faq...droid-ipad-etc

However during the sending of the file sometimes no new image file is being generated in the Kindle's thumbnails folder. For most books a new thumbnail is placed there and the Kindle shows the cover correctly.

Any ideas on this? Any logging I could enable to investigate?

I'm using the latest version of Calibre.

Tim

[kovidgoyal]

You can run calibre in debug mode (right click the rpeferences button and choose start in debug mode) that should have logging about why thumbnail generation failed.

[London Rain]

I've compared a debug log of a book where the thumbnail was generated with one where it wasn't. The only difference I can spot is the usage of an ASIN that looks like a GUID.

Please see both logs here.

No cover generated:

Job: 4 Ein Buch auf das Gerät hochladen: Wolkenschloss started
Device using plugboard azw3 KINDLE2 [[u'{series}{series_index:0>2s| - | - }{title}', u'title']]
Setting metadata in: Wolkenschloss at: C:\Users\TIMDIE~1\AppData\Local\Temp\calibre_h5tg6 x\4ba3iycaltmpfmt.azw3
DEBUG: 41.4 USBMS: uploading 1 books
C:\Program Files (x86)\Calibre2\app\pylib.zip\dateutil\parser.py:60 1: UnicodeWarning: Unicode equal comparison failed to convert both arguments to Unicode - interpreting them as being unequal
APNX META: guid: 4adebe5f
APNX META: ASIN:
APNX META: CDE: EBOK
APNX META: format: MOBI_8
APNX META: Name: Wolkenschloss
APNX Content Header: {"contentGuid":"4adebe5f","asin":"","cdeType":"EBO K","format":"MOBI_8","fileRevisionId":"1","acr":"W olkenschloss"}
DEBUG: 42.4 USBMS: finished uploading 1 books
DeviceJob: 4 Ein Buch auf das Gerät hochladen: Wolkenschloss done, calling callback
DEBUG: 42.4 USBMS: adding metadata for 1 books
DEBUG: 42.4 USBMS: finished adding metadata
DeviceJob: set_books_in_library: books to process= 80
DeviceJob: set_books_in_library finished: time= 0.0019998550415
DeviceJob: 4 Ein Buch auf das Gerät hochladen: Wolkenschloss callback returned
Job: 5 Metadaten zum Gerät senden started
DEBUG: 42.7 USBMS: starting sync_booklists
Job: 4 Ein Buch auf das Gerät hochladen: Wolkenschloss finished
Keine Details verfügbar.
DEBUG: 43.4 USBMS: finished sync_booklists
DeviceJob: 5 Metadaten zum Gerät senden done, calling callback
DeviceJob: 5 Metadaten zum Gerät senden callback returned
Job: 5 Metadaten zum Gerät senden finished
Keine Details verfügbar.

Cover generated:

Job: 4 Ein Buch auf das Gerät hochladen: Die Flüsse von London started
Device using plugboard azw3 KINDLE2 [[u'{series}{series_index:0>2s| - | - }{title}', u'title']]
Setting metadata in: Die Flüsse von London at: C:\Users\TIMDIE~1\AppData\Local\Temp\calibre_7vbhv u\z0butbcaltmpfmt.azw3
DEBUG: 7.1 USBMS: uploading 1 books
C:\Program Files (x86)\Calibre2\app\pylib.zip\dateutil\parser.py:60 1: UnicodeWarning: Unicode equal comparison failed to convert both arguments to Unicode - interpreting them as being unequal
APNX META: guid: bccdfa7f
APNX META: ASIN: 200f22d1-32c9-4d7d-9f87-5c4a8a08ebe7
APNX META: CDE: EBOK
APNX META: format: MOBI_8
APNX META: Name: Die_Flusse_von_London
APNX Content Header: {"contentGuid":"bccdfa7f","asin":"200f22d1-32c9-4d7d-9f87-5c4a8a08ebe7","cdeType":"EBOK","format":"MOBI_8","fileRevision Id":"1","acr":"Die_Flusse_von_London"}
DEBUG: 7.9 USBMS: finished uploading 1 books
DeviceJob: 4 Ein Buch auf das Gerät hochladen: Die Flüsse von London done, calling callback
DEBUG: 7.9 USBMS: adding metadata for 1 books
DEBUG: 7.9 USBMS: finished adding metadata
DeviceJob: set_books_in_library: books to process= 80
DeviceJob: set_books_in_library finished: time= 0.00300002098083
DeviceJob: 4 Ein Buch auf das Gerät hochladen: Die Flüsse von London callback returned
Job: 5 Metadaten zum Gerät senden started
DEBUG: 8.1 USBMS: starting sync_booklists
DEBUG: 8.8 USBMS: finished sync_booklists
DeviceJob: 5 Metadaten zum Gerät senden done, calling callback
DeviceJob: 5 Metadaten zum Gerät senden callback returned
Job: 4 Ein Buch auf das Gerät hochladen: Die Flüsse von London finished
Keine Details verfügbar.
Job: 5 Metadaten zum Gerät senden finished
Keine Details verfügbar.

Edit:
The GUID I marked red also seems to be the crucial part of the cover thumbnail file name. So it seems to be needed to do a match between the book's meta data ASIN and the cover image filename? But why is it being ommited in the first case?

[kovidgoyal]

Do a mobi to mobi conversion and you will be fine. The conversion will insert an asin for you.

[London Rain]

Currently I only have an EPUB version of that book. And shouldn't it generate a random GUID ASIN if it is being converted to AZW3 and "Enable sharing of book content option" is checked in AZW3 conversion options?

[theducks]

Originally Posted by London Rain

Currently I only have an EPUB version of that book. And shouldn't it generate a random GUID ASIN if it is being converted to AZW3 and "Enable sharing of book content option" is checked in AZW3 conversion options?

NO , you are confusing that with UUID
ASIN is an Amazon assigned (catalog) number

[London Rain]

Ah, thanks!

So in short: For the mechanism to generate a matching thumbnail cover to work, it's absolutely mandatory to have an ASIN in the book's metadata? Is there a way to search for books without one?

[sammayor]

The Quality Check plugin can find missing ASIN in mobi files.
It also has Fix option for adding ASIN to the mobi files.