By Bronwen Parsons
Security: Watch Out!Engineering
These days there's a security camera watching our every move. Instead of debating the ethical issues of this constant surveillance, however, (see Comment page 6) the security industry in Canada is muc...
These days there’s a security camera watching our every move. Instead of debating the ethical issues of this constant surveillance, however, (see Comment page 6) the security industry in Canada is much more interested in discussing new technologies that will help them to watch us more closely.
At the Canadian Alarm and Security Association (CANASA) International Security Conference and Exposition in Toronto last October 17-18 one of the most popular sessions was a panel discussion entitled “What’s Hot,” on the topic of file storage. This is a pressing problem facing security companies — what to do with the hours of recorded images that one day (but probably never) may be needed for legal purposes.
With digital recorders “compression” is the answer. Wavelet compression uses an intelligent algorithm to take frequencies that are important to the human eye. DCT (discrete cosine transform) technology has been around longer. Michael Afheldt of Ademco Video explained that people often refer to it by the compression standards, which are JPEG, MPEG, H.261 and H.263.
With any kind of compression, Afheldt said, you trade off size for quality: the plainer the image, the less data it needs. Wavelet and some DCT systems use motion detection to decide when to record. That means static images of a blank wall compress well, whereas the motion differentials recorded at a busy location such as a supermarket check-out can need 10 times as much file storage capacity.
Most building owners first ask for the capacity to record images in real time for 30 days, said Afheldt, which means recording 60 images per second. However, he said, most systems work well taking six to 10 images per second. Also wide angle views need fewer frames to capture the same view.
The legality of video surveillance images came up for discussion among several panelists. Courts are increasingly using video tape for evidence — the Rodney King beating in Los Angeles and the Paul Bernardo murders in Ontario — being among the most famous cases. The problem is how to verify that the video has not been doctored. Encryption and watermarking are the answer with digital recording.
Digital discs are preserved better than VHS tapes which are damaged by stretching and heat. As well, digital technology doesn’t need massive amounts of bandwidth, which is important when the images are being transmitted to a remote monitoring station. Live video is a “bandwidth hog,” said one panelist.
Searching for recorded events is a lot easier with digital recorders because the operator can simply click the date and time and retrieve an image in seconds. With VHS tape the user has to go through the unwieldy rewind/fast forward routine. JAZ and ZIP discs hold up to two gigabytes of data, DVD will hold four gigabytes, but the mother lode is RAID (redundant array of inexpensive discs) which stores data on multiple hard drives in interleaved stripes.
In a different session Larry Doan of Extreme CCTV Surveillance showed some of the most advanced video recording cameras on the market. The British Columbia company founded by Jack Gin, a professional engineer, sells cameras with integrated infrared night-time viewing, technology that is already common in the U.K. Doan turned out the lights in the seminar room and showed the audience how easy it is for the camera to “see” in darkness with the technology. When the even more penetrating Forward Looking Infrared Radar (FLIR) systems come available, security staff will even be able to detect activity behind walls.