Checksum-verified card offload
The most expensive footage on a production is the footage you cannot re-shoot. Getting it off the camera cards safely is the DIT's quiet responsibility, and the rule underneath it is simple: a copy you have not verified is not a backup. This guide explains what verified copying means, why checksums matter, what an MHL is, and the discipline that lets you call a card safe to format.
The short version: copy to more than one drive, checksum-verify every file, keep the MHL as proof, and only then format the card. No single unverified copy is ever enough.
Why drag-and-drop fails silently
When you drag files from a card to a drive, nothing confirms the copy is complete and correct. A dropped bit, a flaky cable, a nearly-full disk or a sleep event can corrupt a file while the copy appears to finish cleanly. You find out only when someone opens the shot — and by then the card may already be back in the camera, wiped.
What checksum verification is
A checksum is a short fingerprint calculated from a file's actual contents (with algorithms like xxHash or MD5). Verified copying calculates the fingerprint at the source, writes the file, then reads it back and calculates it again. If the two match, the copy is proven bit-for-bit identical. If they don't, you know immediately — while you can still do something about it.
Redundancy: more than one copy
Verification proves a copy is good; redundancy protects against a drive dying. The standard on set is at least two copies on separate drives — often a working drive and a backup, sometimes a third for the vault — each independently verified. A card's footage should exist, proven, in more than one place before anyone thinks about reformatting.
MHL: the proof and the paper trail
A Media Hash List (MHL) is a small XML file that records the checksum of every file in a transfer, with timestamps. It is both the evidence that a copy was verified and a chain-of-custody record — the document editorial, post and insurers can trust that the footage handed over is exactly what the camera recorded.
The "safe to format" discipline
Formatting a card is irreversible, so it earns a hard rule: a card is safe to format only once its footage exists as verified copies on more than one drive, with the MHL written. Treat "safe to format" as a state the software confirms — not a judgement call made under time pressure at the cart.
Doing it without the anxiety
Good offload software makes the safe path the easy one: copy to several destinations at once, verify every file by checksum, write the MHL and reels automatically, and only then mark a card safe to format. That is exactly what Olycen is built to do — one click from card to safety, with the proof written as ASC MHL.
Verify before you format. The card is the only original until the copy is proven. Prove it, twice, then wipe.
One click from card to safety.
Olycen copies every file to multiple drives with checksum verification, writes the proof as ASC MHL, and only calls a card safe to format once every copy is proven. In closed beta on macOS.