The security industry continues to be challenged by ever increasing requirements for surveillance applications. Comprehensive security and surveillance strategies are including digital video surveillance as a first option in ever increasing numbers. These strategies are designed to provide users with better threat detection and prevention, a low cost of ownership, streamlined security operations and decreased liability.
Along with this increasing need for surveillance systems is the increased need to effectively manage and use the massive amount of recorded images that must now be stored. Security directors who would manage from a few to hundreds of cameras just a few years ago, must now provide security surveillance services that include several hundred to even thousands of cameras — all of which produce recorded images that must be stored and available on demand.
Traditional Video Surveillance
The classic CCTV implementation that is still in use in many locations has not changed dramatically since the invention of the video recorder. These systems have been used successfully for many years. The typical installation included analog CCTV cameras which had separate wires pulled to them for power and for transmitting images over proprietary wired coaxial connections to VHS video recorders. Add a monitor and the security guard can watch live video or watch playback on the VHS.
Larger implementations of these systems would have security guards watching an ever increasing number of monitors — each of which would present either a continuous image of the area under surveillance or it would “cycle” between several camera fields of view in a predetermined sequence. Practical limitations for the number of monitors effectively screened by a security officer began to drive innovation towards enhancing these systems. Multiplexers were added to these systems to allow the recording of several streams of video onto the same tape, yet separated into discrete viewable streams on playback. Tapes only had a few hours of recordable surface, so multiplexers were used to drop frames in the stream to create the notion of the time-lapse VCR to permit longer recording time coverage on the same tape — although it would do so by reducing the number of actual recorded images.
Many environments still use these systems — even though by today's standards, analog camera and tape systems have a number of limitations. These implementations need manual tape storage and re-use procedures to ensure that retention of the images was available. The process was tedious and prone to human error leading to misplaced or lost information. Video tapes have a limited life span and would need to be replaced often to ensure the quality of the images remained within acceptable tolerances. Keeping the recorders cleaned and serviced meant taking them out of service. Finally, the coaxial cables had limited effective distances which meant that these systems were deployed locally to the tape recorders and could not be transmitted between remote facilities.
The real bad news for users of these systems is that many of the manufacturers of tape systems have opted to discontinue making them as recently as 2005, which makes it imperative to consider alternatives as replacements, service and parts will soon become significantly more difficult to find.
The First Real Innovation: the DVR
Rapid development in video compression algorithms such as JPEG, MJPEG, MPEG and others coupled with lower data storage costs on digital media prompted the creation of the Digital Video Recorder, or DVR. DVR technology comes directly from the computer world using the same disk technology found in servers. Conceptually the DVR is quite similar to the TiVo system you may have connected to your television set at home, and it has several advantages over traditional tape systems.