Mobipocket Decoder Tool - Page 3

DaleDe · 02-10-2008, 07:54 PM

Quote:

Originally Posted by wallcraft

The mobidedrm tool does seem to allow Kindle AZW e-books to be read by MobiPocket Reader software and (all) MOBI e-books to be read on the Kindle.

However, it may not allow format shifting because the MOBI "exploder" mobi2html does not work on files that use "Mobipocket hufdif compression" (mobigen -c2). Most DRM-free MOBI files use simple compression, but it is unknown what fraction of DRM-laden files use hufdif.

It would probably be ok for mobi2html to add support for hufdif (particularly since there are some DRM-free MOBIs using it), but first someone has to work out how to decompress such files.

There are plenty of people including the author of FBReader that would like to have the answer to that question.

Dale

HarryT · 02-11-2008, 04:03 AM

Has anyone tried asking Mobi for a specification of the compression format?

kovidgoyal · 02-11-2008, 04:07 AM

I'd guess it would be some kind of huffman code, since that's optimal for data on which you have a good prior. See http://en.wikipedia.org/wiki/Huffman_coding

darkninja · 02-11-2008, 04:53 AM

If someone can provide me with mobipocket files that use the HuffDic compression scheme, I could attempt to write a decoder, assuming the compression format isn't too complicated and/or it would take too much time to figure out how it works.

Jaapjan · 02-11-2008, 05:02 AM

If you want to do such a thing then the easiest thing you can do is to get the free mobipocket creator from their website, generate a miniature book and compress it with various kinds including the c2 option so you can check how it proceeds from raw uncompressed to compressed state. Really, all you need you can download for free already.

tompe · 02-11-2008, 07:43 AM

Quote:

Originally Posted by HarryT

Has anyone tried asking Mobi for a specification of the compression format?

It was asked in

http://www.mobipocket.com/forum/view...=decompressing

by DMcCunney but no answer.

DMcCunney · 02-11-2008, 11:43 AM

Quote:

Originally Posted by HarryT

Has anyone tried asking Mobi for a specification of the compression format?

Yes, on their Creator forum. As expected, no response.
______
Dennis

tompe · 02-11-2008, 11:46 AM

Quote:

Originally Posted by DMcCunney

Yes, on their Creator forum. As expected, no response.
______
Dennis

I wonder why they could not have responded with just "No"?

TallMomof2 · 02-11-2008, 07:05 PM

Thank-you, DarkNinja for liberating my DRMed books! Even with the flu I feel like dancing!

darkninja · 02-12-2008, 01:35 PM

I wrote a decompressor for the new huffdic compressed files. Maybe this code can be incorporated into mobiperl?

Note. This program does not break any DRM encryption, so it's not illegal. It just decompresses files compressed with the new compression into a raw html file.

Thanks to Igor Skochinsky for the valuable assistance.

http://pastebin.com/m656dfbda

llasram · 02-12-2008, 02:41 PM

Quote:

Originally Posted by darkninja

I wrote a decompressor for the new huffdic compressed files.

Nice! However for the one from-the-wild compressed mobipocket book I have the trailing data-entries size calculation is obviously spurious (e.g. values like 251929435 bytes), which results in significant quantities of clipped text. Any chance you could take a second look at your algorithm / post details of how you derived the algorithm you do have?

joewandy · 02-12-2008, 10:15 PM

Quote:

Originally Posted by TallMomof2

Thank-you, DarkNinja for liberating my DRMed books! Even with the flu I feel like dancing!

Thanks from me too

Ironically for MobiPocket, this development would just result in more business from me as I would be less hesitant in buying more buying more Mobi books from now on.

darkninja · 02-13-2008, 01:31 PM

I made a blog!

http://darkreverser.wordpress.com/

Here you can read about my reversing!

badgoodDeb · 02-13-2008, 02:01 PM

Oooo - I see on your blog that you've also got an eReader to html converter. THAT one I'll have to go try! I have a *bunch* of eReader books, that I haven't all read yet and want to read on my Kindle.

mores · 02-13-2008, 05:45 PM

hmmmmmm ... what about protected eReader books?
There's a book I *really* want to read, but it's only available in pbook or eReader format. Could I buy it from eReader and then convert it to html? *ohpleaseohpleaseohplease*

EDIT: as I can see in another thread, your tool will do just that! excellent!

02-11-2008, 04:53 AM	#34
darkninja Member Posts: 12 Karma: 636 Join Date: Feb 2008 Device: none	Mobipocket HuffDic compression If someone can provide me with mobipocket files that use the HuffDic compression scheme, I could attempt to write a decoder, assuming the compression format isn't too complicated and/or it would take too much time to figure out how it works.

02-12-2008, 01:35 PM	#40
darkninja Member Posts: 12 Karma: 636 Join Date: Feb 2008 Device: none	I wrote a decompressor for the new huffdic compressed files. Maybe this code can be incorporated into mobiperl? Note. This program does not break any DRM encryption, so it's not illegal. It just decompresses files compressed with the new compression into a raw html file. Thanks to Igor Skochinsky for the valuable assistance. http://pastebin.com/m656dfbda Last edited by darkninja; 02-12-2008 at 06:51 PM.

02-13-2008, 05:45 PM	#45
mores Guru Posts: 834 Karma: 102419 Join Date: Sep 2007 Location: Vienna, Austria Device: iPhone	hmmmmmm ... what about protected eReader books? There's a book I really want to read, but it's only available in pbook or eReader format. Could I buy it from eReader and then convert it to html? ohpleaseohpleaseohplease EDIT: as I can see in another thread, your tool will do just that! excellent! Last edited by mores; 02-13-2008 at 05:55 PM.

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02-11-2008, 04:03 AM	#32
HarryT eBook Enthusiast Posts: 85,560 Karma: 93980341 Join Date: Nov 2006 Location: UK Device: Kindle Oasis 2, iPad Pro 10.5", iPhone 6	Has anyone tried asking Mobi for a specification of the compression format?

02-11-2008, 04:07 AM	#33
kovidgoyal creator of calibre Posts: 45,609 Karma: 28549044 Join Date: Oct 2006 Location: Mumbai, India Device: Various	I'd guess it would be some kind of huffman code, since that's optimal for data on which you have a good prior. See http://en.wikipedia.org/wiki/Huffman_coding

02-11-2008, 05:02 AM	#35
Jaapjan Avid reader Posts: 262 Karma: 132 Join Date: Mar 2005 Location: The Netherlands Device: HTC Touch Diamond, iLiad Book Edition	If you want to do such a thing then the easiest thing you can do is to get the free mobipocket creator from their website, generate a miniature book and compress it with various kinds including the c2 option so you can check how it proceeds from raw uncompressed to compressed state. Really, all you need you can download for free already.

02-11-2008, 07:05 PM	#39
TallMomof2 Kindlephilia Posts: 2,017 Karma: 1139255 Join Date: Nov 2007 Location: Snowpacolypse 2010 Device: Too many to count	Thank-you, DarkNinja for liberating my DRMed books! Even with the flu I feel like dancing!

02-13-2008, 01:31 PM	#43
darkninja Member Posts: 12 Karma: 636 Join Date: Feb 2008 Device: none	I made a blog! http://darkreverser.wordpress.com/ Here you can read about my reversing!

02-13-2008, 02:01 PM	#44
badgoodDeb Grand Sorcerer Posts: 8,574 Karma: 64462893 Join Date: Jan 2008 Location: Harrisburg outskirts Device: Palms, K1-4s, iPads, iPhones, KV, KO1	Oooo - I see on your blog that you've also got an eReader to html converter. THAT one I'll have to go try! I have a bunch of eReader books, that I haven't all read yet and want to read on my Kindle.

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