Video motion detection (VMD) is rapidly changing how security professionals use video. The term "motion detection" as it is applied to digital video is ambiguous. It can refer to capabilities ranging from simple activity detection to the search of massive databases to pre-empt serious incidents. Therefore, if you desire to implement a VMD system, you have much to consider.
How Video Motion Detection Works
When a video image is converted to data in a digital format, the image information becomes a stored digital value. This digital value changes as the video image, the source of the data, changes. Complex algorithms (a series of analytical steps) analyze the changing digital values to recognize patterns. Some vendors call this video content analysis. Since these algorithms are a software function, they are programmed into chips and boards that can be installed in cameras, stand-alone modules, digital video recorders and dedicated computer processors. VMD is also available as software for installation in off-the-shelf computers.
The complexity of these products varies greatly. The IP cameras provide a separate output on basic activity detection, while the PC-based software and modules provide graphic identification of the identified movement, user-selectable monitored areas, compensation for environmental movement, and a host of other features.
The table on page 28 lists several products and the systems on which they operate. It is not intended to compare apples to apples; it simply shows the variety of equipment upon which VMD can reside.
Available VMD Features
Because VMD terminology is not standardized, the vendor-supplied product information can be less than concise. Selecting the appropriate VMD approach requires understanding the features available, and understanding requires study.
Basic motion detection typically recognizes any type of motion in the video field. A single output then activates automatic call-up to the monitor screens of surveillance personnel or initiates automatic DVR recording. The video call-up is no longer limited to cabled CCTV systems, but can be transmitted via the Internet or wirelessly. Many basic DVRs can search and retrieve records of movement or activity on their stored hard drives. These features are often found on off-the-shelf equipment, are economical, and have limited applications. Advanced VMD products enhance the concepts of basic motion detection and can, when properly applied and operated, provide innovative, effective solutions to security issues. Most of these features result from elaborate algorithms that search out detailed movement patterns and only activate a system response under very specific conditions. Capabilities include:
- Intruder Identification: Identifying unauthorized humans in specified areas of the field of view.
- Environmental Compensation: Recognizing and ignoring wind-blown debris, animals, background traffic, etc.
- Counting: Recognizing a quantity of a particular object moving or activity performed.
- Directional Identification: Ignoring objects moving in one direction, while alarming for objects moving in unauthorized directions.
- Item Recognition: Activating when specific user-selected items are removed from, placed in, or passed through the field of view.
- Subject Tracking: Highlighting and following a specific person or item as it moves about the field of view, or from the field of view of one camera to another.
- Multiple Subject Tracking: Highlighting and following multiple persons or items simultaneously as they move about the field of view, or from the field of view of one camera to another.