IP Video Builds on What You Know
Dealing With Image Degradation
However, in applications where analog is converted into digital one must be very careful of image degradation. That is because analog and digital use different video display methods. The signal coming from the analog cameras is interlaced while digital monitors and DVRs favor progressive scan.
Interlaced means the lines that make up the picture on the analog monitor are drawn in an alternating fashion. In the United States, first the even lines appear on the screen, and then the odd lines. During interlace display scanning the screen is refreshed in two top-to-bottom passes such that the lines scanned in one pass are positioned between the lines drawn in the previous pass.
Progressive scan means the lines that make up the monitor picture are displayed all at once in sequence. It renders all lines in a single top-to-bottom pass, which requires twice as much data per pass as interlaced scanning. 
Therefore, when moving from analog to digital, the video data format must be converted from one that is compatible with interlaced fields to one that provides progressive frames prior to rendering on a digital display. The process of translating received interlaced video signals into a progressive scan format for output and display on any digital display is called de-interlacing.
Properly processing the video from its native interlace form factor to high quality progressive-scan data is extremely important to the overall quality of the resulting image. Not only will any de-interlacing artifacts be visible, but they also increase the work that the codec must do to compress the image, resulting in lower quality at a given data rate.
The transformation is done in the DVR but not all DVRs are created equal. Before selecting one type of product over another, the user wants to literally see results. If the cameras are analog and the monitor is digital, de-interlacing creates a progressive scan at the DVR and passes it onto the digital monitor. However, when the user wants to get extended time out of the analog monitor, the progressive scan needs to be reconverted back to the interlacing method. This is the setting at which the image can get softened and uneven.
Sprinkling In Some Pixel Dust
The measurement of resolution (normally horizontal) in the analog world depends upon perceived differentiation be
tween lines on a standard NTSC or PAL (the two types of TV standards used in the world) resolution chart. This resolution depends upon how fast the electron beam can change its intensity as it traces the image.
In the digital world, the resolution is determined by the actual number of pixels that make up an image, measured in horizontal and vertical rows. The more pixels you have on an image, the more resolution you will have. The CCDs (charge coupled devices) used today are available in two resolutions. The lower resolution imager contains 510 horizontal rows and 484 vertical columns of pixels, or about 250,000 total pixels. The higher resolution imager contains 768 horizontal rows and 494 vertical columns of pixels, or about 380,000 total pixels.
The equivalence between the two methods of measurement can be accomplished by multiplying the number of horizontal rows of pixels by .75 to provide the equivalent lines of analog resolution. Thus, the typical analog resolution equivalence is 380 TVL for the 250,000 pixel (510 X .75 = 382.5) imager and 540 TVL for the 380,000 pixel imager (768 X .75 = 576).
Be Mindful of Monitor Choices
Obviously, the most important attribute is picture quality. Professional monitors provide advanced picture quality with SXGA (super extended graphics array) resolution greater than 1,000:1 contrast ratio, maximum of 5ms response time and minimum of 300 cd/m² brightness. They also feature a built-in durable power supply that provides continuous 24-hour operation as well as tempered glass, which protects the delicate LCD panels for long-life viewing.
Help your customers select a monitor that meets their current and future requirements. For instance many monitors have limited feature sets and lack the versatility to connect to the video devices in a system. Multiple video formats, such as composite, YC, VGA and looping outputs may be missing from a lower cost monitor.
Professional monitors incorporate a built-in de-interlacing function, which insists on a 3-D comb filter. The comb filter is designed to help correct detail and color loss that occurs when the video display renders the signal onto the screen by layering several versions of the image on top of one another. The comb filter is effective when displaying analog signals on the monitor.
Beating the Bandwidth Blues
One key advantage of IP-based video is the ability to use network infrastructure, providing adequate bandwidth and availability of switching and routing, rather than coaxial cabling. However, running bandwidth-intensive surveillance video over corporate data networks is a point of organizational contention, depending on the potential impact on network performance. If there is not enough bandwidth in the network to handle the high resolution network cameras, the results will be less than satisfactory.
Realizing the prospective growth of IP video, a group of video management companies are now creating software to help manage the capture and storage of video content. Likewise, video surveillance hardware manufacturers are working with them to assure that the transportation of IP images will yield clean, usable video. When migrating to IP video surveillance, the integrator will want to make certain the video hardware provides an agnostic software interface so the desired software can be used without compromise.
IP Holds the Key to Your Future
To be successful in the future, you will need to be able to deploy IP/digital video solutions. Indeed, there are specific markets — education, law enforcement, transportation, water treatment and new construction — that will now only specify IP/digital video solutions. Manufacturers are every bit as interested in selling IP/digital video to these markets as you are, so put them to work for you.
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