A CCTV is a Closed Circuit Television. It is a system of video cameras, monitors, wired/wireless network, data network/storage hardware in closed network circuit. This system monitors the activity in any internal or external premises. The CCTV system are designed for security and monitoring.
What is an Analog Camera?
In Analog Camera light is converted to analog signals which is sent to Digital Video recorder (DVR). The DVR converts Analog signal to Digital Signal. This digital signal is then compressed by DVR and send to Storage and the Router. The router forwards the packet to Internet and Internal LAN. From LAN/Internet signals are sent for Live View at user end. The camera uses RG59 co-axial cables to connect to DVRs.
Flow for the Analog Camera setup is as follows :-
Light -> Camera -> Analog Signal -> DVR -> Digital Signal -> Compression -> Network (Router) & Storage (Playbacks) -> Monitors (Live)
All camera signal here are sent as one stream using single IP address.
What is an IP Camera?
In IP Camera the camera itself converts the Analog signal to Digital Signal. This digital signal is then sent to Network Video Recorder (NVR) via a POE (Power over Ethernet) switch. The NVR compresses and streams the signal to Storage devices and the Router. The router forwards the packet to Internet and Internal LAN. From LAN/Internet signals are sent for Live View at user end. IP Camera uses Ethernet cable to connect to other devices.
Since the camera itself outputs digital signals the result is a higher resolution than AHD Camera. It has higher brightness, stable images, sharp and system is more power efficient.
The image are crisp and does not distorts even when viewing at far distance from DVR/NVR. While images from AHD varies with distance DVR.
Flow Flow for the IP Camera setup is as follows :-
Light -> Camera -> Digital Signal -> PoE Switch/Ethernet cable -> NVR -> Compression -> Network (Router) & Storage (Playbacks) -> Monitors (Live)
The surface size of the camera sensors in any CCTV camera can be 1/2 inch, 1/3 inch, 1/4 inch or 1/8 inch.
What are DC BNC Connectors?
These provide CCTV cable connection to AHD Camera and also supplies power. This is also called as RG59 connectors.
What is HD CVI Camera?
HD CVI stands from HD Composite Video Interface. It uses coaxial cable for long distance HD transmission and supports upto 4K UHD. It can stream 4 signals – Audio, Video, Data and Power over one coaxial cable. The co-axial cable used here is RG6. RG6 is higher copper gauge cable with high insulation for high bandwidth and high frequency signals.
What is difference between various cables or transmission media for CCTV?
CCTV system uses any of the below cables from transmission of signal depending on the camera. It may use Ethernet for IP Camera. RG59 is heavily marketed for partial co-axial cable for transmission in limited space or internal premises. RG6 is complete co-axial cable for open premises and long distance viewing.
As can be seen HD CVI RG6 cables are better for long distance high resolution images. While RG59 can provide 4K upto 500 meters. IP Camera has limited range of maximum 450 meters.
What are HD TVI mode?
It stands for HD Transport Video Interface. This supports 1080p HD transmission over 500 meter using RG59 co-axial cables. But the maximum resolution is only 2.1 MP. It is an old technology in CCTV.
What is CVBS Signal?
CVBS stands for Composite Video Baseband Signal. It is used for analog video tansmission without audio. The video is 480*570 standard format PAL, NTSC. This results in very poor image quality. CVBS produces conventional analog signal through BNC Connection.
So in terms of resolution HDCVI > AHD > HDTVI > CVBS.
What are the resolutions in AHD/IP Cameras?
Below table gives the entire resolution ranges in AHD or IP Camera :-
Field of View is Height * Width (H * W) for monitors by CCTV Cameras.
Depth of Field (DoF) is a selection zone in the field of view.
Focal Length determines the field of view (H*W)
Varifocal length is adjustable focal length which can zoom and see clear images.
What are PTZ Camera?
A PTZ camera is Pan, Tilt or Zoom. These heavy camera for external monitoring.
Pan -> Horizontal Movement Left or Right
Tilt -> Vertical Movement up or Down
Zoom -> Varifocal Adjustment. It is used for Motion Detection trigger.
What are the technologies used in modern CCTV Cameras?
- 3D DNR – 3D Digital Noise reduction is used mostly for night and dim lit conditions. Without DNR images are distroted and overlapping in dim light. With DNR images are distortion free and sharp. 3D DNR reduces noise on basis of previous subsequent frames. It is good for image clarity.
2. 2D DNR – It is a noise reduction technology on basis of previous individual frame. This feature is good for VMD. Video Motion Detection (VMD) is controlled by Video Recorder.
3. CMOS stands for Complimentary Metal Oxide Semiconductor. It is the main photodiaode sensor in the camera that captures light.
Earlier CCD sensor was used. CCD moves electrons across the chip. This consumes high power. But it produces high quality images with high light sensitivity less noise.
In CMOS, each pixel has dedicated transistor that connects to CMOS Sensor. In this setup electrons are wasted in the transistors. This produces lower image quality. With time and enhancement images are now at par with CCD Camera.
Other benefits includes that CMOS is much cheaper while CCD require special machines that results in higher costs.
4. BLC – Backlight Compensation – It is a setting that allows to choose area which should be exposed instead of the default position.
5. HLC – Highlight compensation – This reduces brighter part of the image which is over exposed.
6. WDR – When camera has 2 image sensors. They capture same scene at different exposures. Both are adjusted for better results.
7. AWB – Automatic White Balance – adjusts the color temperature to match the light available.
8. AGC – Automatic Gain Function. Under low light condition noise is reduced for sharper images.
9. uPnP – Universal Plug and Play.
10. ICR – Infrared Cut Removable Filter. This filter is in place at day to block infrared light and capture clear images. At night this is removed for surveillance in low light condition.
What are Progressive and Interlaced Scanning in CCTV Camera?
CCTV images are formed by sequence of pixel lines scanned and displayed in one of two ways – Progressive or Interlaced.
In Interlaced Images odd and even lines are created at 25/30 frames per second. This is CCD device exclusive.
In Progressive scans, both CCD and CMOS cameras can be used. It obtains values from each pixel and scans them consequently to complete the picture. So it scans 1st, 2nd, 3rd lines…etc until entire frame is scaned. It then combines them to image.
Thus, Interlaced used for smoother images in TV. While Progressive scanning used in Machine Vision for sharper images.
What is Video Compression used in DVR and NVR – H.265 and H.264?
Video Compression uses HEVC. HEVC is High Efficient Video Coding. H265 was launched in 2013. It uses 4K stream especially in Netflix, Amazon.
AVC is Advanced Video Coding. It was released in 2003 under H.264.
Both the HEVC and AVC produce same image quality. But the difference lies in compression. Thus, H.265 uses lesser space than H.264. H.264 workds on 16*16 pixels. But, H.265 can work on 64*64 pixel.
Minimum requirement of H.265 is Windows 10 and Intel 6th Generation.
Industry is working on H.266 -> VVC – Versatile Video Coding. This is proposed to give 50% higher compression than HEVC.
H.265+ or H.264+ both lowers the bandwidth required. So, less RAM is consumed and less network bandwidth used.
In H.264+, bandwidth usage is reduced by 20-40% which average to 30%.
While, in H.265+ bandwidth is reduced by 30-50% which averages to around 40%.
Buy best Networking, CCTV and Desktop products online in India here at networkitstore.in