Timothy Spear schrieb am 12.08.2018 um 18:42:
The primary reason I have converted from CR2 and JPEG to DNG was for
the inherit hash embedded in the file which can help prevent/notify
you of bit rot. Since I have previously experience with bit rot I
consider this worth it.
Which reminds me, I need to put in a new ticket issue to suggest a
validation function to dt which will store a hash for both the XMP and
the original image, and can run in a background process.
That's what I am doing currently with my .NEF and .ORF files:
https://www.bilddateien.de/fotografie/bildbearbeitung/foto-backup.html
Translation of the important part:
Checking data consistency
What does "data consistency check" mean?
For digital data, so-called checksums can be determined by
mathematical methods, which represent a kind of "fingerprint" for a
file. Changing the file, either by processing or by a data error that
has crept in over time, results in a change to the checksum.
If you now determine their respective checksums for all files to be
backed up and save them, you can check at any time later whether the
files are still in their original state. To do this, the checksums are
determined again and compared with the values originally calculated
and saved. Deviations indicate file errors.
prerequisites
On the basis of the "non destructive imaging" technique described
above, the consistency check results:
There are a lot of files in the camera raw formats, but possibly also
uncompressed in.tif, which take over the function of the analog
"negative" or "slide" as original files, can only be read and should
therefore not change anymore.
These - and only these - are the subject of the test!
And then there are at least as many of these xml files (2 edit
versions of the same image give 1 raw file and two xml files) in the
same folders, whose characteristic is the change.
Pictures and associated xml-files are typically located in year
folders and there in subordinate project folders.
The check (both the original generation of the checksums and the
subsequent comparisons) should be performed automatically by software.
Such a software results in a requirement profile:
Program with GUI (graphical user interface - no command line stress)
Recursive creation and checking in directory trees (subdirectories
are also searched)
Filtering of unwanted file types (here in the concrete example:
xmp (of Darktable), pp3 (of RawTherapee), ...)
possibly different hash functions (mathematical methods for
checksum determination) for selection (crc32 or md5)
if possible cross-platform software (there are versions for
Windows as well as Linux)
An example of a suitable software is Checksum Control.
Translated with www.DeepL.com/Translator
--
regards
Bernhard
https://www.bilddateien.de
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