Data Handling & Checksums
Essential knowledge
Essential knowledge
Transferring recorded material from the original media should never be done using a simple file copy. There are different software and hardware 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 different types of checksums, which are all meant for the same:
Safe and fast copy at the same time.
For example, there’s a checksum file called ‘MHL (Media Hash List)’. The structure of the file is fixed. It’s an XML based file which always contains the following information:
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).
The price for copy tools ranges from free to several thousand dollars, depending on the convenience and ease of use of the solution: