ShotlyWhy a plain copy is not enough
Dragging a card to your drive in Finder or File Explorer copies the files, but nothing checks the result. A loose cable, a tired card reader, a drive that fills up or a card pulled out too early can leave a file incomplete or damaged. The copy looks fine in the folder, and you find out in the edit, after the card has been formatted and reused.
Verifying means reading every copied file back from the drive and comparing it with the original on the card. If the two match, the copy is good.
What a checksum is
A checksum is a short code calculated from the contents of a file. The same contents always give the same checksum, and a single changed byte gives a different one. Comparing the checksum of the file on the card with the checksum of the copy tells you whether they are identical.
Common checksum types for footage are xxHash64, MD5 and SHA1. xxHash64 is fast enough to check large video files without slowing the offload down.
An MHL file (Media Hash List) lists every file in an offload with its checksum. It is a common format in film and TV production: whoever gets the drive next, an editor, an assistant or a post house, can use it to confirm that nothing changed along the way.
A routine that works on set
- Copy the whole card. Keep the folders and the small sidecar files the camera writes next to the clips, such as XML and metadata files. Editing software uses them for timecode, clip names and relinking.
- Give it a place. Use one folder per client and per shoot, and one folder per card inside it, named after the camera and numbered in order.
- Check every file. Compare each copy with the card by checksum, not by file size and not by looking at thumbnails.
- Make a second copy. Copy to a second drive and check that one too. A rule many studios follow: three copies, on at least two different drives, with one kept somewhere else.
- Keep the log. Save a transfer log and an MHL file with each offload, so you can show later what was copied, when, and that it matched.
- Format in the camera. Once every file is checked on two drives, format the card in the camera that will use it next. Camera makers recommend this over formatting on a computer.
A folder structure that stays the same for every job makes all of this easier to check at a glance:
When clips were renamed
Comparing by name stops working as soon as someone renames a file. A clip called C0042.MP4 on the card might be hero_shot_final.mp4 on your drive. A name check calls it missing, so you copy it twice, or you trust a different file with the same name. Comparing by content, with a checksum, recognises the clip whatever it is called.
Several cards at once
On a busy day you might come back with a cinema camera card, a drone card and an action camera card. Copy them side by side if your drives can keep up, but give each card its own folder and check each one on its own. A card is only done when every file on it is checked.
How Shotly does this
Shotly is a small app for Mac and Windows built around this routine. Plug in a card and it shows how many files aren't on your working drive yet, matched by content. Pick the client and the shoot, and Shotly:
- copies the whole card into the shoot, in a roll folder named after the camera, or keeps the card's own folder structure if you prefer;
- reads every file back and compares its xxHash64 checksum with the card;
- mirrors every copy to a second drive if you add one, checked on both;
- writes a transfer log and an MHL file into the shoot's _Logs folder;
- turns its ring green when every file is checked, so you know the card is safe to format.
It costs €3, paid once, with no subscription and no account.