DJI or GoPro video won't open? The footage is probably still there

First: let the camera try

Both DJI and GoPro can repair a cut-off file on their own, and sometimes that's all it takes.

• GoPro: put the card back in the same camera and switch it on. If the camera found a damaged file, a repair icon appears on the screen (on older models: SOS). Press any button, and the camera repairs it. Sometimes the last few seconds of the video are lost, and that's fine.
• DJI: put the card back in the camera or drone, switch it on, and wait about half a minute. According to DJI's manual, the camera tries to restore the file itself.

How you know it worked: the file opens in a player and plays to the end. If not, carry on.

Before the steps: did the file arrive complete?

If the file reached you by download, WeTransfer, Drive sync or through the DJI app, and not straight off the card, compare its size with the original. A smaller file, or one that stops at exactly a round number of megabytes, arrived incomplete, and no program builds that. Ask for the file from the card itself.

What to do, step by step

1. Copy everything to the computer. The broken file, and while you're at it a healthy clip from the same card. From now on work only on the copies. The card stays aside.
2. Prepare a “sample clip”. A healthy recording from the same camera at exactly the settings the broken file was shot with: same resolution (4K, say), same frames per second (25, 50 or 100), same recording quality, and the same compression type (H.264 or HEVC; both exist in the DJI and GoPro menus). Simplest: a clip you shot the same day, just before or after the broken one, without changing settings in between. The clip you copied from the card usually fits. If there isn't one, put a card in the camera, lens cap on, and record 30 seconds.
3. Run a free program called untrunc. It takes the map from the healthy clip and builds a new one for the broken file. Download it here (Windows. A normal program with buttons, nothing to type). On the page that opens, download untrunc_x64.zip, unzip it, and run untrunc-gui.exe (not untrunc.exe, which is the version without the window). It handles DJI and GoPro. Pick the sample clip, pick the broken file, and run. If the file that comes out won't open, run it once more, that happens. How you know it worked: a new MP4 appears, and it opens in a player.
4. Check the whole file, not just the start. The length should match what you shot. Scrub to five or six points along the video, especially near the end. At each one stop, play a few seconds, and check the picture moves smoothly and the lips match the speech. If the picture jumps or the sound drifts: the sample clip doesn't match closely enough. Find a closer match and run again. Don't switch programs.

Why it happens to these cameras in particular

Action cameras and drones tend to shut off mid-recording more than regular cameras: a small battery that runs out, overheating that shuts the camera down to protect itself, a slow memory card that can't keep up with 4K, or a drone landing on an empty battery. In all of these the file's map never gets written, and the file is left full size and mapless. That is exactly the situation that can be repaired.

Two real cases, in both directions: the tool was tested on a healthy Osmo Action clip whose map was removed and rebuilt from another clip from the same camera, and the result came out identical to the original. And a DJI file that arrived by download was 88 percent empty, and no program could save that one. The difference between the two is the size check above.

Short answers

• The camera didn't offer to repair, and no icon appeared? That happens, mostly when the card was taken out before the camera was switched on again. Go straight to the steps above: the result is the same.
• Do I need technical knowledge for this? No. The program works like any other: open it, pick two files, press a button. Nothing to type.
• The drone file came through the app, not from the card? Usually it's a reduced copy, and sometimes a partial one. The full file is on the card in the drone, and that's the one to work with.

If you're stuck

If the file is big, if the second run also came out jittery, or you just don't have the head for this right now, send me a link to the file and to a healthy clip from the same camera. I first check whether the footage is actually in the file and tell you where you stand. That check is free. If there's something to recover and you want to go ahead, you get a price for the file. You pay, and then the work starts. And if I couldn't recover it, you get your money back, all of it or part of it, depending on the result.

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Prefer email? avihaiteram@gmail.com

More short guides on the same problem

• Sony .RSV file won't open
• “moov atom not found”
• 0xc00d36c4 “This file isn't playable”
• Premiere: “inconsistency in the file structure”
• VLC “can't recognize the input's format”
• untrunc didn't work?
• The full guide: what happened, what not to do, the three cases