Device guide
Camera died while recording? How to recover the corrupted video
One famous thread called it "20 minutes of recording, 21.4 GB of heartbreak" — a Sony a7 III that died mid-take and left a giant MP4 no player would open. Whether it's a dead battery, a tripped power cable, or a Canon a6400-style thermal shutdown, the failure is identical across brands: the recording was never finalized. And that means it's usually fixable.
Quick answer: let the camera attempt its own repair first (card in, power on). If that fails, copy the file to a PC with a healthy clip shot at the same settings, and rebuild the index with reference-file repair. The file's size is good news — 21 GB on disk means 21 GB of frames survived.
Step 1: the camera's own repair
Reinsert the card into the same body and power on. Sony shows "Recovering data…", Canon and Panasonic have equivalents. This is the manufacturer's sanctioned fix for exactly this scenario and costs nothing. Two cautions: don't format when prompted (that message can appear alongside recovery), and if the camera itself won't power on, move straight to step 2.
Step 2: secure the files
- Copy the broken clip off the card — plus a healthy clip recorded at identical settings (same resolution, frame rate, codec/bitrate mode). Another take from the same shoot is ideal.
- Panasonic body? Look for an .mdt file — that IS your footage. Canon R-series crash? Look for a .DAT file, same idea.
- If most files on the card vanished, stop — that's file-system corruption. Run SD-recovery software on the card before anything else, and don't write to it.
Step 3: rebuild on the PC
- Stream copy first:
ffmpeg -i broken.mp4 -c copy fixed.mp4— cheap to try, occasionally sufficient. - Reference-file repair: the healthy same-settings clip becomes the structural template to rebuild the broken file's index — the method explained here. This is what works on the "hex detectives" cases where nothing will even open the file.
- Verify playback, audio sync, and duration before archiving. Expect to lose only the last seconds before power died.
Mind the file size. Pro camera files are huge — 20 GB+ for minutes of 4K. Online repair services cap uploads (commonly 5 GB) and charge after preview. Local repair has no size ceiling and your client footage stays on your machine.
Built for the 21 GB heartbreak file
StreamSalvage repairs any size locally — drop the broken clip and a reference take, preview the result free, pay $29 only if your footage comes back.
Download StreamSalvage for WindowsPreventing the next one
Overheat shutdowns: mind ambient temp, use dummy batteries/USB power for long takes, and on hot sets swap bodies before the thermal bar maxes. Power: replace aging batteries (they sag under 4K load while reading full), tape down power cables on interview sets, and remember dual-slot relay recording won't save you — power loss unfinalizes the file on both cards.
Frequently asked questions
My camera died while recording — is the footage lost?
Usually not. The video data was being written to the card continuously; what's missing is the index the camera writes when recording stops normally. A 21 GB file that won't play typically contains ~21 GB of intact frames waiting for a rebuilt index.
Should I let the camera try to repair the file first?
Yes. Put the card back in the same camera and power it on — Sony, Canon, and Panasonic bodies all detect unfinalized recordings and offer built-in repair ("Recovering data" / "Repairing file"). It's free and lossless when it works. Only move to PC repair if it fails.
How do I repair a huge Sony a7 III MP4 that won't play?
Copy the broken file plus a healthy clip shot at identical settings (same resolution, frame rate, codec — XAVC S bitrates matter) to your PC, then use reference-file repair to rebuild the index. Local tools handle 20+ GB files that online services can't accept.
What if almost all files vanished from the SD card after the camera died?
That's file-system damage, not just an unfinalized clip — the card's allocation table was corrupted mid-write. Stop using the card immediately and run SD-card recovery software to carve the files out first; then repair any recovered clips that won't play.