Expanded functionality of modern cameras.
The use of digital signal processors (DSP) in the circuitry of modern analog cameras has made it possible not only to improve the quality of the formed image — namely, to increase clarity, sensitivity and dynamic budget — but also to implement a range of additional functions taking into account the specifics of the industry.
There are not many manufacturers of DSP for CCTV cameras in the world. First of all, these are, of course, electronic giants Sony, Panasonic, Samsung Techwin and Sharp. The processors produced by these companies are distributed all over the world and are used by numerous manufacturers of security cameras.
However, this does not mean that all cameras have the same characteristics. The developer is given the opportunity to play with each function, determine the limits of adjustment, refuse some parameter or, conversely, select it. However, the common features inherent in the features of a particular DSP are clearly visible.
The functionality of a modern analog camera with digital signal processing is so numerous that the thesis that an IP camera is the pinnacle of perfection can be criticized. Particularly impressive are the successes of some DSP developer companies that have begun the first attempts to implement analytical detectors in analog cameras. This can increase the intensity of competition between analog and digital systems, especially in connection with the current economic situation in the world.
OSD menu, motion detection, image stabilization, noise reduction, image inversion, compensation of «dead» pixels, image masking zones, titles, remote camera control interface RS-485 or via coaxial cable — this is far from a complete list of available functions that can be found in the specifications of a modern camera. This publication provides a description of the most common functions found in models of various manufacturers of television cameras.
On-Screen Display menu is a typical function of a modern camera with digital signal processing, which provides the ability to graphically display the parameters and settings of the camera. The OSD menu provides not only a convenient user interface, but also the ability to systematically configure many parameters, which is physically impossible to implement using dip switches.
The image inversion function (flip/mirror) allows you to turn the image over, change the sides — left/right or top/bottom. This function is useful when installing the camera on the ceiling in an inverted position and behind a moving car.
Digital zoom is not a useless function, despite the critical view of many experts. For PTZ cameras with a zoom lens, using this function provides an additional opportunity to better examine a small object (for example, a car number). Of course, within the framework of a reasonable magnification of 4-8 times. For stationary cameras, digital zoom is limited to 1.5-2 times and can be used to slightly correct the angle of view of an inaccurately selected lens. Of course, digital zoom entails a loss of image quality, but for a high-resolution camera (500-600 TVL), performing the task of viewing a relatively small area, the losses are not so critical.
Image Stabilization is a function designed to compensate for the movement of objects in the frame and improve image quality due to less blur. CCTV cameras usually use digital stabilization. This is a less expensive solution than optical stabilization with a stabilizing element in the optics. Of course, it is also less effective. In fact, electronic stabilization allows you to compensate for image blur at high shutter speeds. There are also algorithms for compensating for industrial frequency vibration when installing a camera on the walls of industrial buildings or transformer stations.
Privacy Masking is a function that appeared in television cameras several years ago and is supported by law in a number of European countries. The function allows you to create several opaque areas in the image and thereby hide private areas from the operator's eyes. Masking zones are primarily designed to protect privacy in a large city, where the proximity of houses and commercial buildings on which PTZ cameras with powerful optics are installed makes it easy to monitor residents. Zones can be two-dimensional and even three-dimensional, which allows you to hide any object as accurately as possible.
Compensation of «broken» pixels is a function that implements an algorithm for automatically calculating defective pixels of the camera matrix and replacing each of them with a signal from a neighboring pixel. The function requires a special procedure — the camera lens is closed, the algorithm for searching for non-working pixels is activated via the OSD menu (they can be seen on the monitor screen as white dots on a black background), and after a few seconds the image is already free of defects.
Peak Brightness Compensation or HLC (High Light Compensation) – this function solves the problem of suppressing peak brightness in the image. Bright light sources, such as car headlights, become gray, which allows you to see the license plate of a car entering the parking lot. Image noise reduction or SSNR (Samsung Signal Noise Reduction) is a function that allows you to reduce image noise in low light conditions. This function not only subjectively improves image quality at night, but also allows you to objectively increase the sensitivity of the camera. Image noise increases with the signal amplification in the camera as the illumination on the object decreases. The gain level is limited to 24–30 dB. At the same time, image noise is acceptable. In cameras with the SSNR function, the gain reaches 37 dB. At the same time, the sensitivity is maximum and the noise in the image remains subjectively acceptable.
Motion Detection — the motion detector function in a TV camera has appeared and disappeared in models from different manufacturers over the years. With the spread of digital recording systems, in which the video detector function is implemented for each channel, detectors in the camera were abandoned. But not for long. First, object tracking detectors appeared in rotating dome cameras, and now several manufacturers have announced the implementation of analytical detectors in analog cameras. We are talking about detectors of abandoned and moved objects, direction of movement and line crossing. How does the camera report an event? All via the same coaxial cable (Coaxitron protocol), twisted pair (RS-485) or by closing a contact built into the camera.
As noted above, the set of functional capabilities of a modern camera directly depends on the capabilities of the digital signal processor. Today, the determining factor in the competitive struggle between manufacturers is actually not the CCD matrix model, but the DSP. Therefore, processor development companies are able to take a leading position in the ranking of CCTV manufacturers and bring new opportunities to the industry and new technologies to television cameras.