Sixteen Channels on a Surveillance Recorder

The decode

The defining fact is that surveillance recorders use their own format, not a normal filesystem. A CCTV recorder does not save each clip as a file the way a computer does. It writes video from all its channels as a continuous stream in a proprietary structure designed for constant recording and overwriting — Dahua's own scheme here. So a drive pulled from such a recorder does not present browsable video files; it holds the recorder's format, which must be understood and parsed to extract footage. That is the core of the job, and it is what distinguishes surveillance recovery from ordinary file recovery.

Two questions are answered in order: is the drive healthy, and can the format be read. First the hardware — the drive is a standard hard disk and can fail like any other, so its health is checked and, if there is a fault, addressed and the drive imaged before anything else. Then the format — the proprietary recording is parsed from that image to reconstruct the footage. A drive can have both a hardware fault and a format to decode, and each is handled in turn.

Reconstructing footage means turning a continuous stream into usable, time-indexed video. The recorder stores video as an interleaved stream from sixteen channels; recovery separates that back into per-channel footage, indexed by time, so specific cameras and periods can be found. Where the recorder's own structures are intact, this follows its format directly; where they are damaged, the video frames are carved and reassembled by their patterns. The output is footage that can actually be viewed, not a raw stream.

Everything is done on an image, which protects a possibly-overwriting system. Surveillance recorders continuously overwrite the oldest footage, so the drive should not be left running in the recorder once the needed footage exists. It is imaged and all reconstruction happens on the copy, so no further recording can overwrite what is being recovered, and the format analysis can be exhaustive without risk.

The honest prognosis rests on drive health and how much footage remains. If the drive is healthy or its fault is addressable, and the needed footage has not yet been overwritten by the recorder's normal cycle, recovery and export to a standard format is very achievable. The genuine limits are a severe drive fault, or footage already overwritten before the drive was pulled — established at assessment, with what is recoverable and viewable confirmed before any charge.

On the bench

Drive health was first assessed on PC-3000 UDMA and the drive imaged under a hardware write-blocker on DeepSpar Disk Imager where a hardware fault was present. The recorder's proprietary filesystem and video stream were analysed on the image, the continuous recording parsed into per-channel, time-indexed footage, and frames carved and reassembled where the recorder's structures were damaged. The recovered footage was validated by playback and exported to a standard viewable format.

The outcome

Drive health addressed, the proprietary recording parsed and reconstructed into viewable per-channel footage, and the video exported to a standard format. The diagnostic costs nothing and completes within two working days of arrival, and the quote is one fixed written figure with VAT already in it; opening a drive is invasive work, so 50% of the quote is payable upfront to cover donor parts and lab time, with the rest owed only if the data comes back. The decode: a CCTV recorder writes a continuous proprietary stream, not files — so recovering footage means decoding the recorder's format, not reading a filesystem. Parsed properly, the sixteen channels come back as viewable, time-indexed video.

Our case files are written up from genuine enquiries our lab has handled for customers across Swansea and South Wales, anonymised to protect client confidentiality. Each one describes the diagnostic and recovery approach our engineers apply to that fault, using the equipment listed.