How to fix CCTV and DVR footage that will not play

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

Most CCTV, DVR and NVR footage that "won't play" is not corrupted at all: it is exported in the recorder's own format (such as .dav, .264, .h264, .grec or a proprietary stream named .mp4) that only the manufacturer's player or converter understands. Install the vendor's player or re-export as standard MP4/AVI from the recorder. Only when the export really is a standard MP4 or MOV with H.264 or H.265, and it was cut off during export or copying, can its index be rebuilt with a reference exported from the same recorder. You can check which case you have with a free test in the FixMP4 repair tool.

Identify the format first

Open the file in VLC and look at Tools, Codec Information, or use MediaInfo. If MediaInfo reports "MPEG-PS" or cannot identify the container while the extension says .mp4, it is a vendor stream, not a corrupted MP4.

Getting a playable export

1. Use the recorder's export function and choose standard MP4 (or AVI) if the menu offers it. Many NVRs and web interfaces have a format option under Playback, Export or Backup.
2. Install the vendor's player for the native format. It usually also offers "convert to MP4" or "save as AVI".
3. Export to a freshly formatted USB stick, FAT32 or exFAT depending on the recorder, and wait until the recorder reports completion before unplugging it.
4. Keep the original recorder data until the copy has been verified, especially if the footage is evidence; recorders overwrite in a loop.

When repair does apply

If the recorder exported a genuine MP4 or MOV and the export was interrupted (USB stick removed early, power cut, network export timed out), the file is missing its moov atom index. That is the case FixMP4 handles:

1. Export a short, complete clip from the same camera channel on the same recorder with the same export settings to use as a reference.
2. Open the repair tool, add the broken export and the reference.
3. Check the free preview for the time range you need, then export with a subscription.

Cloud-camera apps (Ring, Arlo, Wyze, Eufy, Reolink) normally save standard MP4 clips; an interrupted download of one of those is also repairable, though downloading it again is usually easier.

What cannot be fixed this way

• Overwritten footage: once the recorder has looped over a time range, the video is gone.
• Vendor-encrypted exports without the password or vendor tool.
• H.265+ / Smart codecs played back in tools that do not support them; these are a codec support issue in the player, not file corruption. (Exports of such streams as standard H.265 MP4 are supported.)
• Damaged recorder hard drives: use a data recovery service; do not keep the DVR running.

How the index rebuild works

FixMP4 reads the broken MP4's media data directly from your disk, finds each H.264 or HEVC frame by its NAL unit structure, takes stream parameters from your reference export, rebuilds timing and keyframes, and writes a new index. Frames are not re-encoded, so time stamps burned into the picture and image detail are exactly as recorded. Nothing is uploaded, which matters for footage of people and property.

Evidence considerations

Keep the recorder's original data and the original export unchanged, and keep repaired copies separately with a note of how they were produced. Many police forces and insurers prefer the native export plus the vendor player; ask what they accept. This is general information, not legal advice.

Reading the result

A good repair plays smoothly with the recorder's time stamp overlay advancing normally. If the time stamp jumps, the recorder may have recorded on motion only, which is normal. Blocky frames throughout mean the reference export used different settings, for example main stream versus sub stream; export the reference from the same stream type. A short freeze followed by normal playback indicates damaged data in the export at that point.

Common mistakes

• Treating a .dav or Hikvision stream as a broken MP4 and running generic repair tools on it.
• Unplugging the USB stick before the recorder finished writing.
• Exporting a huge time range in one go to a slow stick; export the minutes you need instead.
• Leaving the recorder running after an incident, so the footage is overwritten.

Prevention

• Configure the recorder to export standard MP4 by default if it can.
• Test exporting a clip before you need it, so you know the steps.
• Check the recorder's retention period and disk health regularly.

Related guides

• Fix dashcam video
• "File is not supported" errors
• "Invalid data found when processing input"
• All device guides

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