IP Video Builds on What You Know
Contrary to what might be perceived by all of the articles in security magazines, exhibitions at trade shows and talk within the security industry, less than 15 percent of video surveillance applications involve IP/digital video.
The reasons analog video still rules the market are obvious to those who work with different types of companies wanting to strengthen safety and security. First and foremost, there are many analog video systems installed that run on coax and, in many cases, their users are simply upgrading components. In other instances, security managers are leery of moving beyond what they already understand and currently works for them.
Many resellers, including dealers and integrators, are also uncomfortable with IP/digital surveillance. They see connectivity as a big issue. Plus, IP/digital video has some new vocabulary that needs explaining.
Hopefully, this article can provide a kind of portal into IP/digital video. It all begins with a basic understanding of what comprises a computer-based network.
Cat-5e Provides Infrastructure
An IP camera has its own IP address and built-in computing functions to handle network communication. It is best described as a combination camera/computer that connects to the network exactly like any other node. For the most part, that means you can forget the intricacies of most of our glossary’s definitions. You just need some training on how to piece them together.
The good news is that any major IP video provider will help you to do so. From training manuals, both print and electronic, to actual “hands-on,” “in-the-field” support, your IP video manufacturer should be there to guide you. Once you’ve done a couple of installations with the manufacturer’s help, you’ll be just as capable of configuring an IP/digital system as you are connecting a traditional analog CCTV system.
More good news is that almost all new construction projects include the laying of Cat-5e cabling, a desirable infrastructure for IP/digital systems of any and all types, including video. True IP-based digital surveillance includes cameras that use signal processing to send video streams over the LAN through a Cat-5e cable rather than a coax cable network. This provides greater bandwidth and standard TCP/IP communication.
Hold Onto That Analog Equipment
Integrators and end users want to be sure their system choices provide an upgrade path that is forward-compatible with a future of fully digital IP/digital architecture, without throwing out perfectly good analog equipment. To maximize the customer’s technology choices at the camera, the transmission system and the head-end, leading video systems suppliers are providing products that “connect the dots” between installed analog and digital equipment.
Leveraging UTP Cabling — Joining analog equipment to the digital future is facilitated by the adoption of unshielded twisted pair (UTP) cable as the transmission medium. In fact, most facilities already have UTP cable for their phones and datacom needs. If the customer has it, use it because there is a way to implement a cost-effective hybrid UTP system that gives customers the product choices they need. A UTP-based hybrid solution supports today’s cost-effective analog systems while providing the IP-ready cabling infrastructure when a switchover does occur.
For integrators that want to implement a digital-ready structured cabling system that easily supports a wide variety of existing analog products, a power-video-data (PVD) solution supports cameras. Integrators can deliver a high quality picture over the same infrastructure used by Ethernet datacom systems.
PVD products now let integrators standardize their structured cabling in accordance with EIA 568B wiring protocols, reduce installation time, and fully prepare the plant wiring for future digital systems when desired. The PVD solution provides a convenient, cost-conscious and future-proofed way to connect power, video and data from the camera to the control room.
Leveraging DVRs — The “middle of the road” of video surveillance is upgrading video by utilizing a DVR. A DVR system is not really fully IP-based, but is a step toward the more advanced IP technology. In actuality, a DVR system uses the same camera and structures for cabling as the older CCTV analog systems, but the old VCRs and multiplexers have been replaced with a DVR for storage of the data. The data is converted to digital so it can be stored on hard disks, but the quality of the images captured remains analog since this is how it originated.
In other words, analog signals are fed from the cameras to the DVR where they are converted into digital signals for storage and/or transmission over digital networks.
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 between 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 th
at 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.
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