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Binary diffs: real-world differencing?

From: Daniel Griscom <griscom_at_suitable.com>
Date: 2006-02-03 16:24:06 CET

I'm looking into Subversion, and since I do a lot of multimedia work
I'm especially interested in its ability to do binary diffs. But I'm
wondering: has anyone documented how well this reduces
traffic/storage with different types of real-world files? For
instance:

- Change a small region of a JPEG file, and a much larger region may
actually change

- Change a few lines of code, and a compiled executable's internal
pointers and code locations may completely change

- Change a few pixels of a GIF file with LZW compression may mean
that different pixel strings are represented by different keys,
changing the whole file

- Changing a small portion of an MSWord document may (for all I know)
change the whole file

- Adding or removing a single file from a ZIP archive may (again)
change the compression keys, thus substantially changing the data.

This leaves me wondering whether every time I change a binary file
SVN will spend a long time carefully comparing the old and new
versions, only to throw up its hands and copy the entire new file
into the repository.

So, has anyone documented how well different types of binary files
are differenced? If not, is there a way I can easily test it myself,
perhaps with a command-line executable that takes two files and
outputs a "binary difference" file?

Thanks,
Dan

-- 
Daniel T. Griscom             griscom@suitable.com
Suitable Systems              http://www.suitable.com/
1 Centre Street, Suite 204    (781) 665-0053
Wakefield, MA  01880-2400
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Received on Fri Feb 3 16:26:28 2006

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