A production company pulled a SanDisk 512GB Ultra SDXC card mid-copy, and afterwards half the footage wouldn’t open — scrambled file names, “format required” errors, clips that refused to play. The card’s exFAT file system had been left half-written, and the interrupted clips had lost the index that makes a video file playable. The flash was fine; we imaged it, rebuilt the file system, and reconstructed the broken clips.
A TV production company was offloading a day’s shoot from a SanDisk 512GB Ultra SDXC card when the card was removed before the copy had finished. Afterwards the card was a mess: some clips were missing, others wouldn’t open or play, file names showed as gibberish or blanks, and plugging it in produced “insert disk” or “format required” prompts. Disk Utility and Windows saw the card but couldn’t repair it. With an edit deadline looming they didn’t format it or let the tools ‘fix’ it — they sent it straight to us, which gave the footage the best possible chance.
Writing to a card isn’t a single instant action. A large SDXC card is formatted exFAT, and exFAT keeps several structures in step as data is written: the allocation bitmap that tracks which space is used, the File Allocation Table (FAT) that chains each file’s pieces together, and the directory entries that hold file names and starting points. When a card is pulled mid-write, those updates are left half-finished — a directory entry pointing nowhere, a FAT chain that stops abruptly, a bitmap that disagrees with reality — and the card can no longer present a coherent file system, which is why it reads as corrupt or asks to be formatted. Importantly, that’s damage to the index, not usually to the video data itself.
The clips that were mid-record when the transfer stopped had a second, subtler problem. An MP4 or MOV video file isn’t just a stream of pictures — it contains an index (in MP4/MOV terms, the ‘moov’ atom) that tells the player the codec, the frame rate, the duration and exactly where every frame sits in the file. Many cameras write that index last, when you stop recording and the file is finalised. Interrupt the process and you get a file that holds all — or nearly all — of the actual video data, but with no index to make sense of it. To a player it looks broken and won’t open, even though the footage is right there inside. Rebuilding that index is what brings the clip back.
Nothing was attempted on the original card. It was cloned sector by sector to healthy storage through a write blocker, using tools that read past the damaged areas, so the recovery worked on an exact copy and the card itself couldn’t be altered or worn further. A health check confirmed there was no physical damage — the NAND flash was intact — which meant this was a logical recovery: rebuild the file system and repair the files, all on the image.
Two jobs ran side by side. First, the exFAT structures were repaired on the image — the directory entries, FAT chains and allocation bitmap were reconciled so the intact clips reappeared with their names and could be copied off cleanly. Second, for the interrupted clips whose index was missing, we used file carving and header reconstruction: locating the raw MP4/MOV video data on the card, then rebuilding the missing ‘moov’ index by analysing the stream and using the camera’s known recording format — and a healthy reference clip from the same camera — as a template. That reunited the orphaned footage with a valid index, so editing software would recognise and play it. Where a clip had been genuinely truncated mid-frame, it was recovered up to the last complete, playable point.
Every recovered clip was tested for real — opened and played through in Adobe Premiere and Final Cut Pro, checked for full playback without dropped frames or glitches, and confirmed at the right resolution — before anything was signed off. The complete set, a 99% recovery, was delivered on a fresh external SSD so the edit could carry on without losing scenes. The advice we sent with it is worth repeating on any shoot: always eject a card before removing it, never keep the only copy of footage on the card it was shot on, and if a card does go unreadable, stop — don’t format it or let ‘repair’ run — because the footage is very often still there to be rebuilt.
Sector imaging through a write blocker with bad-area handling · exFAT repair (directory entries, FAT, allocation bitmap) · MP4/MOV file carving and ‘moov’ index reconstruction using a same-camera reference · playback verification in Premiere and Final Cut Pro. All work in-house at our Belfast lab.
Don’t format it or let the tools ‘repair’ it — the footage is usually still there. Send it in for a free, no-obligation diagnostic. We’ll tell you what can be recovered and put a fixed price in writing before any work starts, and on most jobs it’s no fix, no fee. We recover SD, microSD and CF cards for media professionals across the UK.
Usually not. Removing a card mid-write damages the file system’s index, not normally the video data, so the card reads as corrupt or asks to be formatted while the footage is still on it. Formatting is the one thing to avoid. Imaged and rebuilt properly, the intact clips come straight back and interrupted ones can often be reconstructed.
Clips interrupted mid-record often lose the index (the ‘moov’ atom in MP4/MOV) that a player needs, because the camera writes it when you stop recording. The video data is still there but unreadable without that index. By rebuilding the index from the raw stream and a reference clip from the same camera, the footage can usually be made to play again.
Better not to. Repair tools write to the card and can overwrite the very data and structures a proper recovery needs, and apps that run on the original risk making things worse. The safe approach is to stop using the card and have it imaged first, so all the work happens on a copy and the footage is preserved.