How to repair a corrupted dashcam video

By the FixMP4 engineering team · Updated October 9, 2026 · Tested on real H.264, HEVC and AAC recordings

To repair a corrupted dashcam video, first stop the camera from overwriting the card (switch it off and remove the card), copy the whole card to a computer, and check the Event or Locked folder. If the clip you need is an MP4 or MOV with H.264 or H.265 video that will not play, rebuild its index using another intact clip from the same camera channel as the reference. Dashcams that record AVI or MPEG-TS files need different tools; FixMP4 tells you straight away which case you have. The repair tool runs in your browser and shows a free preview.

Before anything else: stop the loop

Dashcams record in a loop and delete the oldest clips when the card is full. Every minute the camera keeps running after an incident can overwrite footage, including a broken clip you could have repaired. Turn the camera off or unplug it as soon as it is safe, remove the card and do not put it back until you have a copy.

Where to look on the card

Sort clips by time and look at the files around the incident. The last clip before power was lost is the one most likely to be broken.

Check the format

Look at an intact clip with VLC (Tools, Codec Information) or MediaInfo:

Popular brands such as Viofo, Nextbase, Garmin, BlackVue, Thinkware, 70mai and Vantrue mostly use MP4 or MOV with H.264 or HEVC, but check your own model: some record TS by default and some let you choose.

Why the clip broke

The camera writes the frames continuously and writes the file index, the moov atom, when each clip ends. If power is cut first (engine off on cameras without enough capacitor reserve, a crash that unplugs the cable, a fuse that blows), the index is missing. Worn-out cards are the other major cause: dashcams overwrite their cards constantly, and a card that is a year or two old may be failing. See why recordings get corrupted.

Rebuild the clip

1. Open the repair tool.
2. Add the broken clip and an intact clip from the same channel (front for front, rear for rear). Clips minutes apart on the same card are perfect references because the settings are identical.
3. Watch the free preview and confirm the moment you need is there.
4. Export with a subscription.

What you get back

• The video up to the moment power was lost, which normally includes the impact itself.
• AAC audio if the camera records it.
• Not restored: GPS and speed overlays stored inside the lost index or as an embedded data track. Separate GPS log files on the card are unaffected, and some dashcams burn the speed and time into the picture, which survives.

Evidence handling

If the footage may be used for insurance or a police report, keep the original card and the original broken file unmodified, and keep the repaired copy separately with a note of how it was made. An index rebuild does not alter video frames; it creates a new table describing where they are. Record the dashcam model, its clock offset and when you removed the card. Ask your insurer what format they accept. This is general information, not legal advice.

How the rebuild works

FixMP4 reads the clip's media data directly from your disk, finds every H.264 or HEVC frame by its NAL unit structure, parses AAC audio frames to measure them, and writes a new index with frame sizes, positions, timing and keyframes. The stream description comes from the reference clip. Nothing is uploaded, which matters for footage of other people and number plates.

Partial recoveries

A clip that plays for a while and then freezes, or shows a burst of blocks, has damaged data on the card. Frames after the damage are recovered once the next keyframe arrives, but the damaged frames cannot be recreated. Check the other channel and any cloud event upload your dashcam app may have made; connected dashcams often upload short event clips when the G-sensor triggers.

Common mistakes

• Putting the card back into the dashcam to "check" it, which restarts loop recording.
• Using a rear-camera clip as the reference for a front-camera file; the resolutions differ.
• Formatting the card on a computer when it asks, which can destroy the unfinished clip.

Prevention

• Use a high-endurance card and replace it every 12 to 24 months.
• Format in the dashcam every few weeks.
• Prefer supercapacitor models, and hardwire kits that give the camera time to close the clip.
• Lock important clips immediately with the emergency button.
• Check now and then that clips actually play.

Related guides

• Fix CCTV and DVR footage
• MP4 is 0 bytes
• Repair corrupted video
• All device guides

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