Need help Decompressing Arithmetic JPEGs

Need help Decompressing Arithmetic JPEGs

Post by sorethum » Wed, 21 Jun 2006 04:40:59

So I had an old DBX file full of old Outlook Express images, and for
some resaon it crashed. So I had to use OutlookEX Recovery from

And now, instead of finding that hte Jpeg Headers are destroyed, what
the REAL problem is that all the images were Arithmetically Compressed!
Oy gevalt.

I found , which is Guido's C
code to be used with the JPEG source code,

but as far as compiling and etc goes, I'm a computer n00b. I know I
should only use them for 'evaluation' purposes, so you don't have to
talk to me about legality here (and neither will I publish anything),

but could somebody give me some easy step-by-step "how to" guide for
compiling Guido's code with the JPEG group's program for the
decompression of my old Jpeg images? (And since I have 388 old
e-mails, I'm going to hope there's a way of doing it by batch, too!)

Thanks, I appreciate this!

Need help Decompressing Arithmetic JPEGs

Post by Guido Voll » Wed, 21 Jun 2006 16:37:00

There is a ready patched version for original (QM) A/C JPEG available here:

This is a slightly updated version towards v7 release of my enhanced library
available in the Jpegcrop source archive from .
The file structure is simplified regarding DCT and Huffman modules, and the
scaling restrictions for floating point are removed.
The QM A/C support will be removed for the v7 release in favor of the new
Q15 mode (ITU-T Recommendation T.851).

Note if you are under Windows, you can also use the Jpegcrop program to
transcode arithmetic coded JPEGs losslessly to Huffman or vice versa.

Guido Vollbeding
Organizer Independent JPEG Group


Need help Decompressing Arithmetic JPEGs

Post by sorethum » Thu, 22 Jun 2006 02:47:08

Thanks. I found the JPEGCrop on your website, saved it to my disk.
If I'm supposed to be able to open Arithmetic JPEG files easily with
JPEGCrop, then it must be my Jpeg files that are corrupt.. and probably
not 'arithmetic' like Photoshop guessed.

What a difficult problem. Thanks for the help, Guido. It's a shame I
wo'nt figure out why I can't open these jpegs ever. ^^;;


Need help Decompressing Arithmetic JPEGs

Post by cypherswip » Thu, 29 Jun 2006 01:36:43

You should post one or more of them so that someone else can take a
look and try to figure out the problem.