Repair a corrupted Hikvision CCTV video

Being honest about this matters, because Hikvision's formats are unusually messy. The recordings sitting on an NVR's disk are a proprietary format — often carried as an MPEG program stream and frequently encrypted "for security" — that plays only in Hikvision's VSPlayer or iVMS-4200. Even a file that lands on your USB stick with a .mp4 extension can actually be that non-standard stream in disguise, and some recorders use Hikvision's own H.264+ / H.265+ encoding, whose frames aren't self-contained. This tool does not decode any of that. If a whole, undamaged file only ever plays in VSPlayer, it isn't corrupt — it just needs converting to a real MP4 first (VSPlayer's Toolbox, or a remux, will do it).

What this tool does repair is a genuine, standard MP4 export — the kind you get when you choose MP4 output in iVMS-4200, the web UI, or the recorder's File › Video download — that came out broken. Inside a proper MP4 export the H.264 or H.265 video is indexed by a moov atom written at the end of the export. If the export was interrupted, that index is missing or truncated, and the container needs rebuilding — which is exactly the repairable case.

The failure is almost always in the writing of the export, not the original recording:

The USB drive was removed before it finished. Hikvision recorders show an "Export Completed" message for a reason — pull the drive (or lose power to the NVR) before it appears and the MP4's tail, including its moov index, is never written. You're left with valid frames and no map to them.

A download from iVMS-4200 or the web UI dropped. Remote playback downloads stream the clip over the network; a dropped connection, a closed laptop, or a stopped app mid-download truncates the file the same way.

The export crossed the 4 GB FAT32 limit. Long CCTV clips are big, and a USB drive formatted as FAT32 silently caps files at 4 GB — a lengthy export gets cut off at exactly that boundary. Re-exporting to an exFAT-formatted drive avoids it going forward, but the already-truncated file can often still be rebuilt from the portion that was written.

In each case the video that made it to disk is intact behind a broken or missing index. What can't be recovered is anything after the cut-off point — it was never exported.

Surveillance video is the last thing you want to hand to an anonymous repair server. It shows faces, number plates, your premises, staff, customers, and often the incident itself — an accident, a theft, an assault. That footage may become evidence in an insurance claim, a police report, or a courtroom, where chain of custody is everything: a clip that was copied onto a third party's servers, under terms you didn't write, is a clip whose integrity a lawyer can question.

Here the repair runs entirely in your browser. The exported MP4 is read from your disk, rebuilt in the tab, and saved back — nothing is transmitted, and you can prove it by opening your browser's Network tab and watching 0 bytes of the footage leave your machine. For CCTV that may end up in a legal or insurance process, that isn't a nicety; it's the whole point.