Quote:
Originally Posted by theducks
Why do you have to ask the hard questions 
Some folk are touchy on file sizes sent to devices. IMHO the tweak should be at the device driver) level.
BUT! Isn't the result contingent on the Calibre stored cover? Should there be a (device driver) limiter that prevents trying to squeeze more out of an already less? |
Calibre doesn't upscale a cover. If the cover is smaller than the normal CC thumbnail size (320 x 320) it is sent as is. CC might upscale it, though.
And I agree with you -- I did it in the device driver.
Quote:
Originally Posted by PatNY
What I don't understand is that you seem to be saying that Calibre makes a thumbnail of a particular cover just once -- and then uses that single thumbnail both for its own internal use (cover browser etc.) and for sending to devices when exporting books. If that's the case, how come this particular cover (Mudbound) looks perfect in my Calibre interface (I can detect no compression artifacts at all) but it looks so splotchy in the book details page of CC? It's like night and day?
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No, I didn't say that. Calibre makes thumbnails all over the place and in varying sizes. Some examples are book details, cover grid, the cover in the book itself, thumbnails on the device, and cover view.
We are talking here about the thumbnail used on devices. These also can vary in size. Example, the "standard" for calibre is 68 x 68. Many devices use larger numbers. CC uses 320x320. We are also talking about the compression quality number. Calibre used 70 (.7) for device thumbs, which is quite highly compressed. It used higher numbers in other places, producing bigger thumb "files" (many are only in memory) with better quality.
My guess is that your huge covers are actually just slowing calibre down and buying you almost nothing. It will never be shown full size, so it is always being downscaled. The only advantage of keeping an original cover is to avoid multiple jpg compressions passes, because each one loses a little bit of quality.
Here are the sizes of the mudbound cover at various compression levels:
50: 9273, 70: 12558, 80: 15482, 85: 17802, 90: 28341, 95: 38352. We can see that switching from 70 to 90 makes the cover 2.4 times bigger. As such, roughly 18kb per book will transfer down to CC for each change, and up to calibre on each connect. This may be worth it for you, but it certainly won't be for many people. Fortunately people can set it how they want.