An Internet Protocol to Arms

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. 

Capturing Fluid Motion Digitally Demands More Electronics Power
When video motion is considered, however, the choice is less obvious. Analog videotape systems generally record at the rate of 30 fps (frames per second). This rate is identical to that of a broadcast television image and represents a rate at which the human brain easily perceives the image stream as fluid motion. Take the rate much below 24 fps and one begins to see the gaps in the motion similar to an old silent film. 

While the technology for transmitting 30 fps analog video has been with us for decades, the transmission of fluid motion digital images is much more recent — and much more demanding. Whereas analog images are sampled and transmitted, digital images are compressed and transmitted. The process of sampling is lossy, meaning a lot of video information is lost. The act of compressing the image retains a lot more information, but it also requires more complicated electronics, more time and produces a larger data stream. 

The cost of the electronics involved has been coming down rapidly, mostly due to the demands of consumers and consumer broadcast equipment. The amount of data required to represent an image has also been reduced somewhat due to the introduction of better compression algorithms — the mathematics involved in fitting a large amount of information into a small space. 

The pesky problem that remains, though, is digital image streams have to be moved from the camera to the display unit and stored on a digital medium, such as a hard disk. The larger the image, the more bandwidth is required to transmit and store it. 

IP-Based Systems Tend to Eat Up a Lot of Network Bandwidth
Once the video image is sampled (analog) or compressed (digital), the task of getting it from the source to the destination begins. When working with analog video, that destination is usually not very far from the source because analog signals decay as transmission distance increases. To combat this, a number of methods exist to digitize the analog stream and transmit the video over digital connections. Fiber-optic digital connections that can carry large amounts of video work this way.

Digital cameras do the work of converting video to digital at the source, reducing the amount of equipment required. Digital cameras equipped with IP connectivity further take the digital data and put it into TCP/IP packets suitable for transmission over shared data networks along with other types of data. Because the data is digital and in a commonly recognized form, it can be easily transmitted, retransmitted and stored without loss of content. 

The richness of the information contained in digital images, however, comes at the cost of bandwidth. In practical terms, when comparing analog and digital video for an application, image size (and, hence, bandwidth) is the major issue. Banerjee notes, “Bandwidth is the single most precious commodity.” This is true, he observes, not only because higher bandwidth connections cost more, but also because the resulting images require more storage space. 

Whereas the video systems introduced to the security industry in the 1970s used a fixed amount of tape for a fixed amount of time, determining h
ow much storage is required by your digital video system is not so easy. “Tweaking color saturation, low-pass noise filters, avoiding AGC [automatic gain control] in low light and vibration all have a major impact on bandwidth, and hence the amount of storage required,” says Banerjee. As a result, digital video takes up a lot of space, typically gigabytes per day per camera, in order to get the same frame rates as analog.

Challenges of Moving Digital Data on Hardwired, Wireless Networks

The size of digital video brings up two issues: how to move it around and where to put it. To get an idea of the actual numbers involved, a single IP camera running continuously at 30 fps will consume 37GB of storage per day and will use around 4Mbps of bandwidth for a CIF (common intermediate format; 320 X 240 pixels) image at medium compression.

Most common IP networks are capable of 100Mbps, so if one had eight cameras on the network about a third of the available bandwidth would go to simply getting images from the cameras to the recorder. This does not count actually displaying the data, which would add another 4MB per camera.

Of course, one advantage of IP video is that it is independent of the type of network you’re using. That means one could just as easily connect a camera over a wireless network as a wired one. The rub is because typical wireless standards provide bandwidths of around 1⁄20th of what common wired networks carry.

Applications in which it is really advantageous to use wireless networks or otherwise conserve bandwidth often drop the frame rate from 30 fps to something around 5 fps. This rate is generally good enough for security video, even though you wouldn’t want to watch a movie that way. At 5 fps, the bandwidth consumption drops to around 0.6Mbps, or just about the capability of a 56K 802.11g wireless connection.

To have two wireless cameras on the same wireless network, it would be necessary to again halve the frame rate, reduce the frame size or increase the compression. It is this fundamental arithmetic that guides when wireless networks are used to carry video.

The big restriction on wireless network speed is the availability of frequencies over which to transmit the data. The FCC has carved out a limited range of these frequencies for wireless data transmission. On the other hand, new standards for wired gigabit Ethernet have multiplied the capacity of those IP networks tenfold. Moving IP video over a network with gigabit capacity easily handles the eightcamera example above.

Fortunately, IP networking makes it easy to mix wired and wireless networks. The wireless bridges to perform that job can be found in retail stores for around $60 per end point. One of the beautiful things about IP video is that consumer demand for networking components has driven the cost way down – something security integrators can take advantage of when designing systems.

Another issue that cannot be overlooked when running video over a wireless network is how to secure the data from unauthorized access. Initial security measures put in place to secure data traveling over 802.11, or WiFi, wireless networks included wired equivalent privacy or WEP keys. WEP keys are passwords ranging in complexity from 64 to 256-bit encryption that permit devices to receive and translate encrypted data as it is transmitted over a wireless network.

However, as Mariann McDonagh, vice president of Global Marketing for Denver-based Verint Systems Inc., points out, the WEP method left wireless networks somewhat vulnerable to breaches, which necessitated the introduction of a stouter alternative.

“WEP keys have illustrated weaknesses, which has brought about a new standard in wireless security called WPA2,” says McDonagh. “Devices that support WPA2 security measures eliminate the weaknesses inherent in WEP encryption methods and are suitable for use in sensitive wireless video security applications.”

Digital Video Can Be Unwieldy To Store

Wired or wireless, once the video is transmitted from the camera source to the recorder, it is initially stored on a hard disk. Terabytes (1,000 gigabytes) of storage are now available for a reasonable price, but at 30 fps and low to moderate compression, the CIF-sized images for a single camera can be stored for only 30 days. Make that 10 cameras, and you only have three days of storage.

Of course, that number can be increased by cutting the frame rate and increasing the compression (and thereby lowering the image quality). If recording only when there is actual motion in the video frame (say 5 percent of the time), things get much, much better. But whether it takes a day or a month to fill up a hard disk, when that disk is full the user must decide to either lose the data or copy it elsewhere.

The common practice with videotapes was to simply have a large stack of them. With digital video, though, the removable media (like CDs and DVDs) only hold a fraction of what the original disk stored. This means that the only logical place to put stored video data for archive is on another hard disk. Eventually, though, this method becomes unwieldy, and it becomes necessary to only save the video surrounding important events and throw the rest away.

The same issue occurs with videotapes, except tapes are much less expensive than hard disks.

Analog Cameras Still Offer Some Benefits, Shouldn’t Be Overlooked

Analog cameras have some special advantages of their own. In the current market, there is often a price advantage to analog cameras that results from the technology’s relative simplicity. And because they’ve been around so long, there are many more models of analog cameras on the market.

Michael Davis, director of Boulder, Colo.-based Electronics Line USA, says, “There is not yet the diversity of IP cameras as there is for analog. Integrated cameras such as mini-domes and bullet styles are very popular in the analog market. Specialty cameras such as wide dynamic range or extreme low light also are not readily available in the IP market as of yet.”

Also, the skill level required of the installer is generally less in an analog system than in a digital networked one. “Many integrators are accustomed to pulling RG59 and only touching a network cable when plugging in the DVR,” adds Davis. “There is a learning curve to tackle, no doubt.”

Analog recordings are also deterministic in that all video frames are of the same size. And as Banerjee pointed out, there is a variety of factors that influence the size of a digital video frame.

Contrasting DVRs, NVRs and Hybrid Recording Solutions

DVRs take analog camera streams, digitize them and store the result on hard disks. Network video recorders (NVRs) take the already-digital output from digital cameras and store it, also on hard disks. The difference is where the digitizing takes place, which we have seen influences the amount of information in the video frames.

Often, DVRs can be attached to networks to gain many of the advantages of digital cameras while maintaining the advantages of analog units. However, according to Electronics Line’s Davis, “Though the processing power in today’s DVRs is growing at a terrific rate, the demands we are placing on DVRs to compress and store video, audio and data, as well as analyze and report locally and remotely, is becoming a bigger and bigger task.”

One of the most exciting advances to hit the video market recently is the hybrid recorder. Hybrids are part DVR (they accept analog cameras) and part NVR (they accept digital video streams as well). Hybrids are appealing to integrators because they are free to select camera types based on what is most appropriate for the application. “In many cases,” says Davis, “a hybrid system of both analog and IP can g
ive you the best of both worlds.”

Hybrids are now available from a number of manufacturers and still more have announced intent to offer them. The downside of hybrids is that they generally support IP cameras from a limited number of manufacturers, although one of the newer units from JVC embeds Milestone Systems’ software, giving it a large library of IP camera types.

Slowly, Surely Security Is Becoming an IP World

As you can see, there are many important points to consider when selecting the right equipment and properly configuring it to optimally serve an IP-based video surveillance application. For an overview, please see the guidance table at left.

Ultimately, the benefits of being able to utilize network infrastructure, geographic independence and flexibility of implementation will be the driving force behind adoption of the technology. Add to that, IP systems are increasing in adoption as standards for communication and interoperability that originate in the IT world merge with the physical security world. Also, third-generation (3G) network appliances that are browser-operated (a comfortable and familiar format for end users) are becoming more common in the security industry.

The market is ripe for installers who are prepared to adapt their skills to an IP model. While the products and skills integral to an analog world are not on the verge of being obsolete, those who adapt to IP will flourish while those who stall run the risk of being out of touch with the market.

Looking ahead just a few years, security products will be networked, applications will be more robust, installers will know the IP space as well as they do analog today, and sales volumes and profits across the IP model will increase. “Ultimately, the IP model is more customizable and expandable,” adds Davis.

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