Analog Systems Fade Out, As IP Gathers Steam
Today, systems integrators have many more options to choose from when specifying a video system than were available just a few years ago. The range of applications that can be handled with today’s video products is much greater, which makes the selection of components more challenging.
Amid the claims of various manufacturers, it can be difficult to separate fact from hype in order to determine what is right for a given application. This article explores how to select the components to form a video system that is right for your client’s application, with particular emphasis on how digital differs from analog and the basics of Internet protocol (IP)-based solutions.
IP Cameras Still Only Comprise About 10% of New Sales
One of the most common discussions, and occasionally arguments, is whether to select analog camera or digital camera equipment. Interestingly, almost all video cameras available today contain digital imagers, making them digital in that sense at least. Combine that with the fact that almost every new recorder stores video data in digital form.
“The discussion around IP vs. analog really only refers to live video, because playback is invariably done digitally as the video has been digitized and compressed for storage, which means of course it is no longer analog video,” says Dr. Bob Banerjee, product marketing manager for Bosch Security Systems of Fairport, N.Y.
What the analog vs. digital debate is really about, then, is how the digital images from the camera’s imager are transported and how cameras are controlled.
The vast majority (more than 90 percent by most research) of cameras sold today are analog cameras, meaning their images are transmitted using analog methods. Typically, these cameras have a BNC connector to which a coaxial cable is connected. The image data transmitted over that cable is analog data, the original digital image having been converted to analog form in order to be transported. In many cases, telemetry data is mixed with the analog video signal for convenience.
The rest of the cameras sold are IP cameras, meaning their original digital images are transported as a series of TCP (transmission control protocol)/IP data packets using a data network connection. Telemetry data is also transmitted this way.
It might appear that not having to convert digital data to analog form in order to transport it out of the camera would result in a cost savings. Alas, this is not the case. Transporting video as a series of IP packets is more complex than doing so as an analog signal, and the digital signal processors (DSPs) or other CPU chips and software required more than consume any possible savings.
However, there are important differences in the performance and capabilities of analog and digital cameras that need to be considered when selecting what is best for a given situation. Among the most important of these are image quality, image size and flexibility.
Digital Images Include More Information Than Analog
Image quality refers to the information contained in an image and is a key difference between analog and digital video.
In analog video, all of the information in the image is displayed. A good way to conceptualize this is to imagine standing 3 feet from a 19-inch, standard definition (nondigital) TV screen. Then imagine standing 3 feet from the same image, but this time on a 36-inch screen. The smaller TV appears “sharper” because, although the information in both images is identical, the magnification is greater on the larger one.
Modern digital TV sets improve enlarged images after the fact using digital post-processing algorithms to enhance the appearance of the image as it is displayed. The amount of information in the pictures is identical to that of less enlarged images, however, continued enlargement simply adds distortion.
Unlike analog images, digital ones generally contain more information than is displayed. This makes it possible to enlarge them without losing information. The result is that, up to the limit of the resolution of the original image, enlargement of small details works without a lot of special post-processing. This means it is possible to zoom in on a digital picture and see more, whereas zooming in on the analog image simply distorts more.
When using surveillance video for identification, digital images can be more valuable because they actually contain more visual information, and thus more detail.
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