Recording 71
16.8 Data Handling
Transferring recorded material from the original media should never be done using a simple file copy.
There are different software solutions available that will copy a file to one or several destinations and
perform a checksum calculation, comparing the material on the original media to the copies, to provide
a minimum effort safety check of data integrity. We strongly recommend using copy software and tools
with checksum calculation and verification. Checksum files should be calculated and generated as
sidecard files at the first copy process.
There are many types of checksums, all with the same purpose: safe and fast copy at the same time.
For example, the ‘MHL (Media Hash List)’. It’s an XML based file with a fixed structure, which always
contains the following information:
Creator Info
Name
Username
Hostname
Tool
Start date
Finishing date
hash
Path to file
File size in bytes
Last modification of the file
xxhash (calculated)
hash date
The ‘creator info’ is placed at the beginning of every ‘MHL’ checksum file. The rest of the ‘MHL’
file contains every single file incl. the xxhash value, which was calculated at the copy & checksum
generation process.
Changing a file or some values inside the ‘MHL’ checksum file results in an error during the checksum
verify process. Checksums should always be generated during the offload of the original camera
negative and should remain next to the files until the final backup process. We strongly recommend a
copy and checksum workflow from beginning (e.g. On-Set) to end (e.g. final LTO backup).
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