[EPUB->MOBI] Calibre MOBI file Size too small

[Upamanyu Santra]

When I convert epub files into MOBI the file size decreases drastically (200 mb to 25 mb sometimes). In the case of normal books which mostly have text in them; it really does not matter. However, comic books or biology books where the high resolution images are necessary it ruins the entire book. I tried everything from changing output profile to Tablet in page setup to disable compression and do not convert all images to jpeg in MOBI output. Can someone please help.
Thanks in Advance

[Karellen]

Is there a reason you need MOBI?

[Upamanyu Santra]

Yes. As you know amazon has recently increased the maximum upload size to 200 mb. But If you upload a 200 mb epub they will convert it into prc and reduce the file size to even smaller files like 15 mb. Ironically the work around that I have found is to rename the MOBI file to epub and then upload them. This works without any problem and I can use them normally in my kindle and most importantly in my tablet. Hence the need for high quality MOBI files.

[kovidgoyal]

convert to azw3 instead

[Upamanyu Santra]

Originally Posted by kovidgoyal

convert to azw3 instead

Unfortunately did not work. Two issues.
1. Same size output as MOBI even after trying every option.
2. The changing extension to epub trick failed. I think they have some sort of setting to prevent anything in KF8 being uploaded.

[JSWolf]

Originally Posted by Upamanyu Santra

When I convert epub files into MOBI the file size decreases drastically (200 mb to 25 mb sometimes). In the case of normal books which mostly have text in them; it really does not matter. However, comic books or biology books where the high resolution images are necessary it ruins the entire book. I tried everything from changing output profile to Tablet in page setup to disable compression and do not convert all images to jpeg in MOBI output. Can someone please help.
Thanks in Advance

I think it's due to incorrect settings in calibre.

To fix this, go to Preferences > Common options > Page setup. Change Output profile to Tablet and Input profile to Default profile.

If you have these options set wrong, hi-res images will be reduced in resolution. A setting of Tablet does not change images at all.

[Upamanyu Santra]

Originally Posted by JSWolf

I think it's due to incorrect settings in calibre.

To fix this, go to Preferences > Common options > Page setup. Change Output profile to Tablet and Input profile to Default profile.

If you have these options set wrong, hi-res images will be reduced in resolution. A setting of Tablet does not change images at all.

Ok one interesting thing I found. I'm currently using version 6.19.1 installed in Windows 11 pc. I also have a backup USB with an older version of Calibre portable release 4.23.0. When I used it (portable version 4.23.0) the tablet setting it did produce a high quality MOBI file from the epub. So maybe there is a bug in this current version. Maybe kovid can take a look when he has time.

[kovidgoyal]

If you think there is a bug with conversion, provide the information asked for here: https://www.mobileread.com/forums/sh...d.php?t=186697

[JSWolf]

Originally Posted by Upamanyu Santra

Ok one interesting thing I found. I'm currently using version 6.19.1 installed in Windows 11 pc. I also have a backup USB with an older version of Calibre portable release 4.23.0. When I used it (portable version 4.23.0) the tablet setting it did produce a high quality MOBI file from the epub. So maybe there is a bug in this current version. Maybe kovid can take a look when he has time.

There is nothing wrong with 6.19.1 in converting ePub with hi-res graphics to Mobi.

Words of Radiance - Brandon Sanderson.epub 28,624,684
Words of Radiance - Brandon Sanderson.mobi 26,750,856

As you can see, a similar size. I checked the combined size of the images and they are both 23.8MB. So the images are not being changed.

[Upamanyu Santra]

Originally Posted by kovidgoyal

If you think there is a bug with conversion, provide the information asked for here: https://www.mobileread.com/forums/sh...d.php?t=186697

Created a bug report as you suggested.
https://bugs.launchpad.net/calibre/+bug/2023189

[Upamanyu Santra]

Originally Posted by JSWolf

There is nothing wrong with 6.19.1 in converting ePub with hi-res graphics to Mobi.

Words of Radiance - Brandon Sanderson.epub 28,624,684
Words of Radiance - Brandon Sanderson.mobi 26,750,856

As you can see, a similar size. I checked the combined size of the images and they are both 23.8MB. So the images are not being changed.

Here check this out.
Original epub 176 MB

Moderator Notice
Removed links to Copyrighted material (This new edition 2021). This is against MR rules. don't do it again.

-
6.19.1 mobi 31.6 MB
-
4.23.0 mobi 179 MB
-
If this is not a bug I don't know what is?

[JSWolf]

Originally Posted by Upamanyu Santra

Here check this out.
Original epub 176 MB

Removed links to Copyrighted material (This new edition 2021). This is against MR rules. don't do it again.
-
6.19.1 mobi 31.6 MB
-
4.23.0 mobi 179 MB
-
If this is not a bug I don't know what is?

Install the ScrambleEbook plugin in calibre and scramble this ePub. Then attach it here and I can test it.

[Upamanyu Santra]

Originally Posted by JSWolf

Install the ScrambleEbook plugin in calibre and scramble this ePub. Then attach it here and I can test it.

Don't worry Kovid with his usual promptness figured out the issue and fixed it. :-) So a big thanks to him and also a big thanks to you as well for you kind attention.