Images captured by close circuit cameras may be used for surveillance. Surveillance cameras in use are, basically, of two types, either analogue or digital camera. The latter can either be digital stills camera or digital video camera.
The video surveillance cameras namely of two types, the analogue cameras and digital cameras, are used. The analogue version records directly to a video tape recorder. This recorder records the images in analogue signals. To make the tape, which usually runs for three hours, record for twenty-four hours, the tape must roll very slowly, say not more than four frames a second. The issue here is that radical changes may occur within a second.
Though these analogue surveillance cameras can also be made to produce digital outputs, which can then be stored in the computer via video capture card, to which the camera is plugged. Even though these cards on a comparative scale may be economical, for continued surveillance the digital signals of the video is compressed 5:1, MPEG compression.
To record digital images, surveillance cameras of the digital video recorder (DVR) many be used. With suitable video recording software and use of a video, capture card, to a PC, its functionality remains similar. For medium to large cameras, on the contrary to PCs, gadgets with simpler maintenance and easier setup than PC solutions are used in majority of the DVRs. By broadcasting the footage, some these DVRs act like network cameras. If they simply broadcast without recording, they are termed as video servers, effectively converting analogue video to digital video.
Digital surveillance cameras output digital signals, avoiding the need for capture cards. From these signals, though compressed 5:1, upon further compression, give DVD quality. As compared to basic 5:1 compression digital video, DVD quality is marginally inferior. In any condition, owing to the fact that image chips of majority standard-definition video cameras are merely 320,000, the video quality tends to be poor.
Network surveillance cameras, irrespective of analogue or digital, have an integrated video server with an IP address, having capacity to stream videos, and in some cases, even audio. Being integrated devices, they do not produce analogue signals. They actually produce higher resolution output as in comparison to the analogue cameras. Network surveillance is a rather cheap mode of surveillance. All that is needed is a camera, a PC and some Ethernet wiring.
With high shutter speed of about a twenty-fifth of a second, it is possible to use digital still cameras as surveillance cameras. If set to take continuous pictures based on ,motion detection, the camera will not only take pictures of a person darting away by the side, but also his face will be captured. The photographs have to be pulled into the computer through a USB port. Else, there are no issues. All that is required is to put the camera on a wall bracket facing the desired direction.
Closed circuit television camera
