A closed circuit television camera ( CCTV camera ) can produce images or recordings for surveillance or other personal purposes. The camera can be either a video camera, or a digital stills camera. Walter Bruch is the inventor of CCTV cameras.
Video Closed-circuit television camera
Kamera video
Video cameras are either analog or digital, meaning that they work on the basis of sending analog or digital signals to storage devices such as video cassette recorders or desktop computers or laptop computers.
Analogue
Can record directly to a video tape recorder that can record analog signals as images. If an analog signal is recorded to the tape, then the tape must travel at a very slow speed to operate continuously. This is because to allow a three hour recording to run for 24 hours, it must be set to run on a slow time base, typically around four frames per second. In one second, the camera scene can change dramatically. For example, if the distance is divided into four parts, ie four frames or "snapshots" in time, then each frame always looks like blurry, except the subject remains relatively silent.
Analog signals can also be converted into digital signals to allow recordings to be stored on the PC as digital recordings. In this case the analog video camera must be plugged directly into the video capture card on the computer, and the card then converts the analog signal to digital. These cards are relatively inexpensive, but inevitably the resulting digital signal is compressed 5: 1 (MPEG compression) so that video recording can be stored continuously.
Another way to store recordings on non-analog media is through the use of a digital video recorder (DVR). Such devices are similar in function to PC with the capture card and the appropriate video recording software. Unlike PCs, most DVRs designed for CCTV use are embedded devices that require less maintenance and simpler settings than PC-based solutions, for medium to large analog cameras.
Some DVRs also enable digital broadcasting of video signals, thus acting like network cameras. If a device allows video broadcasting, but does not record it, it is called a video server. This device effectively converts the analog camera (or any analog video signal) into a network TV.
Digital
These cameras do not require video capture cards because they work using digital signals that can be stored directly to the 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 of 5: 1, with video quality slightly lower than 5: 1 at best , and can be adjusted for the amount of space to be retrieved compared to the required or desired image quality). The highest picture quality of DVDs is only slightly lower than the 5: 1 basic DV compression quality.
Storing uncompressed digital recordings requires enormous hard drive space, and several hours of uncompressed video can quickly fill the hard drive. Uncompressed vacation recordings may look fine but can not run continuous uncompressed quality footage. Therefore, motion detection is sometimes used as an adjacent work solution for recording in uncompressed quality.
However, in any situation where standard definition video cameras are used, the quality will be bad because the maximum pixel resolution of the image chip in most of these devices is 320,000 pixels (analog quality is measured in TV channels but the result is the same); they generally capture the horizontal and vertical line planes and combine them together to create a single frame; the maximum image frequency is usually 30 frames per second.
Nevertheless, multi-megapixel IP-CCTV cameras come on the market. Still quite expensive, but they can capture video images at resolutions 1, 2, 3, 5 and even up to 11 Mpix. Unlike analog cameras, details such as license plates are easy to read. At 11 Mpix, forensic quality images are made where each hand on a person can be distinguished. Due to the higher resolution available with this type of camera, they can be set to cover a large area where usually some analog cameras will be required.
The largest digital CCTV camera in the world is the ST 205 CCTV camera enhanced by TelView on July 10, 2011. It measures 1.7 meters x 4.56m x 1.6m and has a sensitivity of 0.01 lux.
Network
An IP camera or network camera is an analog or digital video camera, plus an embedded video server that has an IP address, capable of streaming video (and sometimes, even audio).
Since network cameras are embedded devices, and no need to issue analog signals, higher resolution of closed circuit CCTV television cameras is possible. Typical analogue CCTV cameras have PAL (768ÃÆ'â € "576 pixels) or NTSC (720ÃÆ'â €" 480 pixels), while network cameras may have VGAs (640ÃÆ'â € "480 pixels), SVGA (800ÃÆ'â €" 600 pixels) or quad-VGA (1280ÃÆ'â € "960 pixels, also referred to as" megapixel "resolution).
The analog or digital camera connected to the video server acts as a network camera, but the image size is limited to the video camera standard. However, optics (lens and image sensor), not video resolution, are components that determine image quality.
Network cameras can be used for very cheap surveillance solutions (requires one network camera, multiple Ethernet cables, and one PC), or to replace all CCTV installations (the camera becomes a network camera, a tape recorder becomes a DVR, and a CCTV monitor becomes a computer with a TFT screen and specialized software. Digital video manufacturers claim that converting a CCTV installation into a digital video installation is basically better).
There has been much debate about the benefits and price-for-performance of Network cameras compared to analog cameras. Many in the CCTV industry claim that many analog cameras can outperform network cameras at lower prices.
Maps Closed-circuit television camera
Digital photo camera
The pixel resolution of the current model easily reaches 10 million pixels. Some point and shooting models such as those produced by Canon or Nikon boast a resolution of more than 20 million pixels.
At this resolution, and with a high shutter speed like 1/125 seconds, it is possible to take continuous jpg images or detect motions that will not only capture anyone who passes through the camera scene, but even the faces of those who drive. then.
These cameras can be plugged into a USB port of any computer (most of them now have USB capabilities) and images can be taken from any camera scene. All that is required is for the camera to be mounted on the wall bracket and pointing in the desired direction.
Modern digital still cameras can take 500 kb photos in 1 second, and these photos are then automatically downloaded by camera software directly to a computer for storage as a timed and dated JPEG file. The pictures themselves do not need to be stored long on the computer. If the computer is connected to the Internet, then images can be automatically uploaded to other computers anywhere in the world, such as and when images are taken.
Users do not need to lift a finger except by simply plugging in the camera and directing it in the desired direction. The direction could easily be a road outside the house, or the entrance to a bank or underground station.
Digital cameras are still being built with built-in wireless connectivity, so no USB cables are required; images are only transmitted wirelessly through wall or ceiling to computer.
See also
- Closed circuit television
- Frame rate
- Video compression
- Video quality
- Ownership DVR
- Network camera
- Trail Camera - A special outdoor Digital Camera that operates on battery and saves detected images to SDCARD
References
Source of the article : Wikipedia
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