Security Camera Systems 101Eugenio Pizarro
So, here are the basics…
Video cameras are either analogue or digital, which means that they work on the basis of sending analogue or digital signals to a storage device such as a video tape recorder or desktop computer or laptop computer.
I. Analogue / DVR
Analogue basically means that you can record straight to a video tape recorder which are able to record analogue signals as pictures. Analogue signals can also be converted into a digital signal to enable the recordings to be stored on a PC as digital recordings. In that case the analogue video camera must be plugged directly into a video capture card in the computer, and the card then converts the analogue signal to digital. These cards are relatively cheap, but inevitably the resulting digital signals are compressed 5:1 (MPEG compression) in order for the video recordings to be saved on a continuous basis.
Another way to store recordings on a non-analogue media is through the use of a digital video recorder (DVR). Such a device is similar in functionality to a PC with a capture card and appropriate video recording software. Unlike PCs, most DVRs designed for CCTV purposes are embedded devices that require less maintenance and simpler setup than a PC-based solution, for a medium to large number of analogue cameras.
Some DVRs also allow digital broadcasting of the video signal, thus acting like a network camera. If a device does allow broadcasting of the video, but does not record it, then it’s called a video server. These devices effectively turn any analogue camera (or any analogue video signal) into a network TV.
Digital cameras do not require a video capture card because they work using a digital signal which can be saved directly to a computer. The signal is compressed 5:1, but DVD quality can be achieved with more compression (MPEG-2 is standard for DVD-video, and has a higher compression ratio than 5:1, with a slightly lower video quality than 5:1 at best, and is adjustable for the amount of space to be taken up versus the quality of picture needed or desired). The highest picture quality of DVD is only slightly lower than the quality of basic 5:1-compression DV.
Saving uncompressed digital recordings takes up an enormous amount of hard drive space, and a few hours of uncompressed video could quickly fill up a hard drive. Holiday uncompressed recordings may look fine but one could not run uncompressed quality recordings on a continuous basis. Motion detection is therefore sometimes used as a work around solution to record in uncompressed quality. However, in any situation where standard-definition video cameras are used, the quality is going to be poor because the maximum pixel resolution of the image chips in most of these devices is 320,000 pixels (analogue quality is measured in TV lines but the results are the same); they generally capture horizontal and vertical fields of lines and blend them together to make a single frame; the maximum frame rate is normally 30 frames per second.
Network IP Cameras
IP cameras or network cameras are analogue or digital video cameras, plus an embedded video server having an IP address, capable of streaming the video (and sometimes, even audio).
Because network cameras are embedded devices, and do not need to output an analogue signal, resolutions higher than closed-circuit television ‘CCTV’ analogue cameras are possible. A typical analogue CCTV camera has a PAL (768×576 pixels) or NTSC (720×480 pixels), whereas network cameras may have VGA (640×480 pixels), SVGA (800×600 pixels) or quad-VGA (1280×960 pixels, also referred to as “megapixel”) resolutions.
An analogue or digital camera connected to a video server acts as a network camera, but the image size is restricted to that of the video standard of the camera. However, optics (lenses and image sensors), not video resolution, are the components that determine the image quality.
Network cameras can be used for very cheap surveillance solutions (requiring one network camera, some Ethernet cabling, and one PC), or to replace entire CCTV installations (cameras become network cameras, tape recorders become DVRs, and CCTV monitors become computers with TFT screens and specialised software. Digital video manufacturers claim that turning CCTV installations into digital video installations is inherently better).
What is an IP Camera?
An Internet protocol camera, or IP camera, is a type of digital video camera commonly employed for surveillance, and which, unlike analog closed circuit television (CCTV) cameras, can send and receive data via a computer network and the Internet. Although most cameras that do this are webcams, the term “IP camera” or “netcam” is usually applied only to those used for surveillance.
There are two kinds of IP cameras:
- Centralized IP cameras, which require a central network video recorder (NVR) to handle the recording, video and alarm management.
- Decentralized IP cameras, which do not require a central NVR, as the cameras have recording function built-in and can thus record directly to any standard storage media, such as SD cards, NAS (network-attached storage) or a PC/server.
IP cameras may differ from one another in features and functions, video encoding (compression) schemes, available network protocols, and the API to be used by video management software.
Advantages of IP Cameras
IP cameras are widely considered as the wave of the future for security camera surveillance systems. IP cameras differ from previous generation analog cameras which transmitted video signals as a voltage, instead IP camera images are sent using the transmission and security features of the TCP/IP protocol, which provides numerous benefits:
- Two-way audio via a single network cable allows users to listen to and speak to the subject of the video
- The use of a Wi-Fi or wireless network.
- Distributed intelligence such as video analytics can be placed in the camera itself allowing the camera to analyze images.
- Transmission of commands for PTZ (pan, tilt, zoom) cameras via a single network.
- Secure data transmission through encryption and authentication methods such as WPA, WPA2, TKIP, AES.
- Remote accessibility, which allows live video from selected cameras to be viewed from any computer, mobile smartphones and other devices (with sufficient access privileges).
- PoE Power over Ethernet to supply power through the ethernet cable and operate without a dedicated power supply.