Mobileread
The difference between converting an .epub to .mobi in Kindlegen vs Kindle Previwer?
#1  Gregg Bell 10-28-2019, 08:06 PM
I have been using Linux computers until the last year or so when I bought a Windows computer also. So for years, I have been converting .epubs to .mobis in Kindlegen in the Linux terminal.

Lately I've been converting some .epubs to .mobis with the Kindle Previewer (version 3.34.0) on the Windows computer and I've noticed some substantial file size differences.

Eg. an .epub (file size 1.0 MB) converted to a .mobi in Kindlegen (Linux terminal) ends up with a file size of 1.0 MB

The same .epub converted to .mobi in Kindle Previewer (in Windows computer) results in a file size of 2.7MB

Ultimately I upload the .mobi to Kindle Direct Publishing.

So what accounts for the huge file size difference?

Is there any advantage to the Kindle Previewer version?

And should I be reconverting all my old ebooks made using Kindlegen by using Kindle Previewer?
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#2  jhowell 10-28-2019, 08:26 PM
Version 2.9 of kindlegen has been the latest one for many years and that is what is included in the Kindle Previewer.

A Master MOBI produced by kindlegen should be about three times the size of the source file since it contains the original source along with copies of the book in MOBI7 and KF8 formats.

It is very odd that your Linux kindlegen produces such a small file.
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#3  Gregg Bell 10-28-2019, 09:55 PM
Quote jhowell
Version 2.9 of kindlegen has been the latest one for many years and that is what is included in the Kindle Previewer.

A Master MOBI produced by kindlegen should be about three times the size of the source file since it contains the original source along with copies of the book in MOBI7 and KF8 formats.

It is very odd that your Linux kindlegen produces such a small file.
Thanks jhowell. I must've been looking at the epub file size (it was next to the mobi) becasue I just ran at test with that file and one other.

File one epub size: 6.4 MB
Kindlegen mobi: 8.1 MB
KP mobi: 8.6
KDP mobi (the mobi I downloaded from Kdp to test it): 8.6

File two epub size: 1.0 (this is the one I originally posted about)
Kindlegen mobi: 2.5MB (not 1.0)
KP mobi: 2.7
KDP mobi: 2.7

So KP does produce a slightly larger mobi than Kindlegen. I checked all my old ebooks and they're totally functional. I'm still a little curious about the slight file size difference if you want to venture a guess, and I assume it would be safest to go the KP route from now. Would you agree?
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#4  jhowell 10-28-2019, 10:10 PM
Quote Gregg Bell
I'm still a little curious about the slight file size difference if you want to venture a guess,
Without examining the files I can’t say for sure, but I suspect different compression of the file contents may account for the difference.

Quote Gregg Bell
and I assume it would be safest to go the KP route from now. Would you agree?
Yes, I agree.
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#5  j.p.s 10-29-2019, 11:12 AM
Quote Gregg Bell
Thanks jhowell. I must've been looking at the epub file size (it was next to the mobi) becasue I just ran at test with that file and one other.

File one epub size: 6.4 MB
Kindlegen mobi: 8.1 MB
KP mobi: 8.6
KDP mobi (the mobi I downloaded from Kdp to test it): 8.6

File two epub size: 1.0 (this is the one I originally posted about)
Kindlegen mobi: 2.5MB (not 1.0)
KP mobi: 2.7
KDP mobi: 2.7

So KP does produce a slightly larger mobi than Kindlegen. I checked all my old ebooks and they're totally functional. I'm still a little curious about the slight file size difference if you want to venture a guess, and I assume it would be safest to go the KP route from now. Would you agree?
You could run kindleunpack -d on the various mobi files and compare the assembled_text.dat files in the difference viewer of your choice.
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#6  Gregg Bell 10-29-2019, 11:19 PM
Quote jhowell
Without examining the files I can’t say for sure, but I suspect different compression of the file contents may account for the difference.



Yes, I agree.
Thanks jhowell. That's what I'll do (KP). Appreciate it.
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#7  Gregg Bell 10-29-2019, 11:22 PM
Quote j.p.s
You could run kindleunpack -d on the various mobi files and compare the assembled_text.dat files in the difference viewer of your choice.
Thanks j.p.s. I actually compared the two original files (I'm not very tech saavy) via converting the .mobis to .txt files and then comparing the .txts in a comparison tool and the texts anyway were identical.

Without the huge file size difference, I'm not worried about it anymore, and I'll just use KP from now on.
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