CCTV Systems – Digital and Network Recording Systems

Digital recording technology has progressed rapidly over the last few years from its humble beginnings. Advances in workstation and server hardware technologies have contributed to the boom in digital recording and its ancillary video streaming solutions.

Where before there was only one digital recording marketspace, now the market is segmenting into different qualities of hardware, encoding algorithms and recording definitions. Physical security managers have had to scale steep learning curves as their systems become integrated into their company IT infrastructures.

There's a lot of dis- and mis-information propagated by manufacturers and salespeople! Here's a 10 second rough guide to the differences.

CIF or Common Interchange Format is a measurement of resolution. CIF resolution(352x288 pixels) produces a horizontal resolution of 276 TVL, which roughly equates to old VCR 240 TVL playback quality. 2CIF (704 x 288 pixels) produces a resolution of 528 TVL which means that you can capture most of a standard high resolution 570 TVL camera's horizontal resolution. However, both CIF and 2CIF systems only use half of the normal vertical resolution, which does lead to loss of replay quality. 4CIF (704 x 576 pixels) gives the same 528 TVL as 2CIF, but uses the full normal vertical resolution. D1 (720 x 576 pixels) is referred to as 'broadcast quality', which basically means that your replay should match the quality of your live images. Mega-pixel cameras extend past the D1 boundaries. Read more in our mega-pixel pages.

Encoding algorithms are used to record and transmit video images both onto disk and across networks. The older 1st and 2nd generation systems use Motion JPEG or Wavelet compression systems. The newer machines use MPEG or H.264 compression. H.264 will save approximately 25% over MPEG-4 on busy CCTV scenes and approximately 50% on inactive scenes.

The quality of hardware used 'under the bonnet' is the hidden cost of DVR solutions. Video processing is computationally intensive, so the machine is working hard. The cheaper systems use workstation grade hard disks, non-redundant disk systems, single PSUs and poorly ventilated casings. They will also use video capture cards that pass most of the processing load back up to CPU on the main motherboard.

Mid level machines still only have 1 PSU but will have server grade disks, some form of redundant disk array and lots of ventilation! The video capture cards will often do some of the video processing on-board, which lightens the load on the main CPU. High end machines sound like they have exotic hardware, but it is just the same stuff an IT manager would normally specify for one of his own servers. This would include dual PSUs in case of a fuse popping of failure, some form of RAID hard disk array in case of disk failure and an industrialised casing with lots of ventilation. Click here for a brochure on our range of DVR systems.