Video Processing and Display Components

CCTV camera signals propagate through the video transmission system and through equipment at the security center or local monitoring point. In very simple configurations with only a few cameras and monitors, a hard-wired connection between each camera and console monitor is adequate. As the number of cameras increases, the need to add supplemental information to camera signals also increases. Psychological testing has demonstrated that the efficiency of console-operator assessment improves as the number of console monitors is reduced. The optimum number of monitors is between four and six. Effectiveness also is enhanced by alarm-correlated video. Major components of the video-processor system are the video switcher, the video-loss detector, the alarm-processor communication path, the master video-sync generator, video recorders, and monitors.

Video switchers are required when the number of cameras exceeds the number of console monitors or when a monitor must be capable of selecting video from one of many sources. Video switchers are capable of presenting any number of video images on various monitors, recorders, and similar equipment.

Video-loss detectors sense the integrity of incoming camera signals.

The alarm-annunciation and video-processor systems must be able to communicate rapidly. The alarm processor must send commands that cause the video switcher to select the camera appropriate for the sensor reporting an alarm. The video-processor system must report system tampering or failures (such as loss of video) to the alarm processor. Date-and-time synchronizing information needs to be passed between processors so that recorded video scenes and printed alarm logs are properly correlated.

Master video synchronization includes a crystal-controlled timing generator, distribution amplifiers, and a transmission link to each camera. This synchronization minimizes image rolling during switching functions.

Video recorders provide the means to record alarm-event scenes in real time for analysis later. A recorder typically receives its input through dedicated video-switcher outputs. To support playback, the recorder output is connected to a dedicated switcher input and must be compatible with the switcher-signal format. In addition, the recorder receives start commands from the switcher.

Video images can be stored on conventional videotape (typically VHS-format cassette tapes) or as digital images on a computer’s hard drive. The security products industry is pushing hard drive storage. That does not necessarily make it a better or more appropriate choice for your application.

Videotape tends to be stored for a predetermined period before being erased and reused. Each erasure and reuse degrades image quality because the recorder’s tape head contacts the tape when it is being used.

Some professional image enhancers believe that images are easier to enhance when they work from videotape than when they work from a computer’s hard drive. On the other hand, images stored on a computer’s hard drive can be indexed and retrieved more quickly than those stored on videotape. As with any other security product, precisely identify your expectations and needs before choosing the product that best meets your needs.

When determining whether to record all or just some video images, consider your facility’s needs. If video assessment figures significantly in the decisions about a security response, the answer is yes that you need to record all video images. Without recording and playback capability, you are relying on one or more persons who may or may not be looking intently at a particular monitor (or at any monitor) when a significant security event occurs.

The video monitor is an important component in the video system. If it is not large enough, important details may not be observed. If it is not properly maintained, image quality will be degraded. The monitors must be positioned properly for ease of viewing at the proper distance.

Video-processor equipment can append time and date information, video source or alarm zone identification, or programmable titles on monitors and recordings. The equipment must allow the operator to program the annotated information and dictate its position on the screen.

All video imagery components must be selected carefully and maintained properly to deliver usable video images. The cost of preventive maintenance and scheduled component replacement and upgrades must be considered when deciding whether to use video for physical security applications.