on 11 Sep 2004 20:55:03 -0000

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Re: [PLUG] corrupt jpeg

On Sat, Sep 11, 2004 at 04:40:36PM -0400, Jeff Abrahamson wrote:
> On Sat, Sep 11, 2004 at 04:20:17PM -0400, Alexander Birch wrote:


> But part of the context you trimmed showed that the byte change was
> from 0xF5 to 0x95.  (I didn't verify but took the original poster's
> word for it.)  That means a high bit was lost, but other high bits
> were not lost.  The file was long enough that a single bit error is
> not so easily explained.  (Recall that only *one* bit in the whole
> file changed.)
> Here's that diff output from the original message:
> > 0063060 ea55 29fd f004 83c0 3fb2 f93a 899e f529
> > 0063060 ea55 29fd f004 83c0 3fb2 f93a 899e 9529
> I wonder if that bit error checksums the same.  It would be
> interesting to check the checksumming routines in whatever file
> transfer program was used to see if the two files look identical to
> it.  Such things are possible with very (very) low probability.
> You then said:
> > This is yet another reason not to use windows.
> ...or another reason not to use linux.  Or just to avoid anything
> that's different. ;-)
> -- 
>  Jeff


Excellent idea.  I ran cksum and md5sum and both are unique for 
each file.  The files were originally part of a tar.gz file.  
The problem is that they extracted fine back in '99 or '00 when 
I unpacked them.  They just "aged" poorly.

# cksum Now-Is-Calling-1.entropy.jpg 
1438987976 29147 Now-Is-Calling-1.entropy.jpg
# cksum Now-Is-Calling-1.original.jpg 
1435228423 29147 Now-Is-Calling-1.original.jpg

# md5sum Now-Is-Calling-1.entropy.jpg 
9d30ba34b124a19e7f3bf880e7c08b74  Now-Is-Calling-1.entropy.jpg
# md5sum Now-Is-Calling-1.original.jpg 
35ed7cd5dac4b73d2cc9fe6f05aa5193  Now-Is-Calling-1.original.jpg

#  Eric Lucas
#     "Oh, I have slipped the surly bond of earth
#      And danced the skies on laughter-silvered wings...
#                             -- John Gillespie Magee Jr.
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