V

Varifocal lens

This type of lens has the capability of varying its focal length in order to zoom in on images. An auto iris feature is required in order to achieve this. Varifocal lenses are contrasted with fixed focal lenses, which are less expensive and often allows more light to pass through them at their set length, enabling better detection in low light circumstances.

Vertical resolution

The number of horizontal lines (or pixel rows) resolved in a picture is called the vertical resolution, and is determined by the television scanning method, be it NTSC, PAL, or some other format.

Vibration sensor

A device that activates when it detects vibrations in its detection zone, and then activates a specific surveillance camera is known as a vibration sensor.

Video amplifier

This device boosts the strength of a video signal.

Video compression

This technique (often a MPEG format) compresses video into lower bit rates for easier Internet transmission, often along narrower bandwidths. Video or audio is compressed to shrink file size, ensuring acceptable transfer speed. Compressed video can sometimes be of a noticeably lower quality, but still clear enough to be useful. AVC is the successor to MPEG as the new video compression standard.

Video distribution amplifier

This amplifier is able to boost signal strength and also to create multiple video signal outputs for delivery to many video devices.

Video intercom

Used at door entryways, this system utilizes audio and video for communication or movement control of people.

Video server

This is a device that accepts inputs from CCTV cameras using the PAL, composite video signal. It digitises the signal and then transmits images via a network, dialup or GSM connection. Advanced video servers have built-in video motion detection, and can buffer images while they are being uploaded to a remote server, where they are recorded.

Video streaming

Streaming video delivers compressed multimedia content over the Internet in a stream of packets. Viewers view the file as it downloads, instead of downloading the entire file first. Streaming video first initializes the transfer, and then buffers it. Bandwidth determines both picture quality and whether or not the viewed video catches up with the downloading content, which causes the video to stop. RealPlayer is one of the most popular free streaming video players available. Video streaming is commonly used for viewing live feeds from security cameras, with RTSP/RTP being the main streaming technology currently in use.

Video surveillance

This term refers to the use of CCTV and DVR to monitor secure sites, or portions thereof. Video Surveillance systems can start with a few as one camera. For systems using more than 16 cameras, enterprise video surveillance systems are preferable. The many terms defined in this glossary give an idea of the many options available for different security needs and situations. In today's professional world, Video Surveillance (often referred to as CCTV) is the most cost effective way to achieve loss prevention.