5 Essential Components of Digital Video
Bandwidth and Video CompressionBandwidth limitations dictate how much video data can be exchanged between the transmitter and receiver in a given application. Like a pig in a python, networks slowly and stubbornly digest large amounts of data, such as that created by digital video. To make it a little easier to swallow, the data is compressed into a variety of formats. Which format to use is determined by the nature of the application, equipment and connectivity.
"The entire reason digital recording becomes an option is due to compression," says Greg Bernardo, product management specialist, Vicon Industries, Hauppauge, N.Y. "Early bouts with digital recording were limited by their large file sizes, which limited how long you could record. Ever-improving compression algorithms have produced much greater storage."
Compression methods can be one of the most relevant factors in selecting a video system.
"Compression is simply the reduction in size of the raw data in order to save storage space or transmission time, because uncompressed video takes up a lot of space. All practical commercial CCTV systems compress the original video images before storing them or transmitting them - and the method of compression and the way in which it is applied is one of the relevant factors in choosing a digital CCTV system," says Nicola O'Dwyer, marketing manager, Dedicated Micros, Chantilly, Va. "Most digital CCTV manufacturers use industry standard compression formats such as JPEG, MPEG, H.261, H.320 and Wavelets."
These standards can be differentiated by "conditional refresh" and "full frame refresh" formats. Conditional formats like MPEG, H.261 and H.320 provide the smallest amount of video data, where storage and transmission are priorities. On the other hand, full frame compression formats, such as JPEG and Wavelets, are usually used when image quality and integrity is more important than reducing data quantities.
"Selecting a compression format is effectively a compromise based on the factors that are most important to a specific application or project," O'Dwyer says. "Conditional formats will use less disk space for a given period of video and should offer faster video transmission over a network. Full frame formats will use more disk space but should offer better image quality and more predictable and consistent performance."
Others stress the need to explain what the compression algorithms actually do. "Everyone claims that they have the superior compression algorithm. But should the customer care? As long as the resulting picture quality is acceptable and the resulting file size allows the necessary storage time, the customer does not really care if it's MPEG, JPEG, Wavelet or Disney Magic," says Olaf Kreutz, digital video systems product manager at Pelco, Clovis, Calif. "What is important is to explain that different compression algorithms will have different effects."
Recording and StorageSelecting the right digital video recorder (DVR) for the application, as well as installing and calibrating multiple video inputs are important steps. These will determine how the data is received, recorded and interpreted. Then the data needs to be stored - an essential and complex component of digital video systems that can be very application-specific.
"Digital multiplex recorders offer the same core functions as traditional multiplexer systems in that they offer an efficient means to record and view multiple cameras," O'Dwyer says. "In addition, digital recording systems deliver instant access to recorded data, the ability to easily copy images on to inexpensive, portable computer storage such as CD ROM or Zip, and the ability to transmit live and recorded pictures over standard computer networks, making CCTV video available to a wider audience."
Bernardo adds, "Most digital recorders record to internal hard drives for their primary storage. How long a recorder can store video before overwriting the oldest recording is determined by the size of the available hard drive storage. As long as the recordings are on the hard drive, an operator is afforded instant access to recorded video."
In addition, there are other factors to look at. "It's important to consider how many days of video the customer will want to be able to review," says Roger Shuman, Integral Technologies, Indianapolis. "This will affect the size of the hard drive for the system, and the customer may wish to look into other archiving options."
Capacity is another consideration, O'Dwyer notes. "Capacity is based on the following decisions: what quality image is required, what speed of recording is required and what is the update rate required for each camera, and how much time do you want to store? Once you have decided on the capacity required by the application, you will need to make a trade-off between cost and accessibility of the video data. Generally, the more immediate the data access, the more expensive the system."
Image ResolutionMany customers are particular about image resolution, and different projects require different levels of picture quality. Digital video data does not degrade like traditional videotape, so maintaining image integrity is not as crucial. Original image quality, however, is important to establishing integrity.
"Watch out for the resolution at which the image-compressor outputs images," says Evelyn Redtree, marketing manager, Applied Integration Corp., Tucson, Ariz. "Some image-compression schemes select only a portion of that frame of pixels for storage, achieving video compression by throwing away vast amounts of important visual data. Some deliver a resolution of 360 by 240 pixels, only 25 percent of the incoming image-feed from the video camera. Some deliver even smaller resolutions - as small as the size of a postage stamp. This is great for storage and transmission, but a judge and jury might have a difficult time using it.
"Make sure the output resolution of the digital video server meets your evidentiary specifications," she stresses.
"While a higher frame rate will produce a smoother video image or stream, lower rates are much more efficient," Shuman says. "We have found that a rate of one to four images per second is fast enough for most customers to assess events. A select few industries, like casinos and locations counting large amounts of money, may have need for a faster frame rate. The image quality can be varied on all digital recorders. The higher the image quality, the larger the image size and the more storage it will require. Video quality is very subjective. A 20K image may look good enough for one customer and the next may require 30K."
Another thing to be aware of is image rates. "Image capture rate does not necessarily apply to the overall image capture rate," Kreutz says. "Needless to say, if you want to capture 16 cameras at three images/sec. each, the DVR should have a minimum overall capture rate of 48 images/sec. More importantly, make sure you only capture those images that you really need. Rarely does one need the same image-record rate for all cameras. A system that does not offer adjustable image rates and various modes such as video motion detection will result in a hard drive requirement that is many times that of a more flexible system."
Software: Video Motion or Activity DetectionModifying software is an effective way to customize projects for the individual needs of customers and the demands of different applications. In many ways software applications are the brains that command digital video systems. One essential software application is video motion or activity detection.
"This is a must for hard drive management," says Cam Crawford, marketing development manager for Radionics' Vision CCTV line. "Make sure this is a full feature section such as video masking, pixel sensitivity, movement sensitivity, and frame rate adjustability. Video masking is the ability to cut out or eliminate a part of the video frame from the video activity detection. Pixel sensitivity is how much changes before the computer recognizes it as a change, and movement is how far something has to go before the computer starts recording. Once the computer starts recording the frame rate must be adjustable per camera. There are a lot of DVRs that claim they have video motion, but you are stuck with full frame motion and no adjustments."
Shuman adds, "The digital video recorder should have integrated video motion detection. The motion detection should have the ability to mask areas as well as adjust sensitivity.
"For instance, a camera set up in a parking lot with a road in the background will constantly trigger motion detectors on many digital CCTV systems. A good system will easily allow the user to mask certain areas of a screen to focus on the primary areas. In addition, even the best system will require some fine-tuning to maximize efficiency. The security professional should regularly look over the camera view and consider how to best use the masking functions to achieve this. Equally important, the dealer should inform the user ahead of time that some fine-tuning might be necessary."
There are other things to be cautious of. "Video motion detection should be an option in any system. Just be aware that the amount of motion detected will affect the storage (retention) time of the HDD and be prepared to deal with shorter retention times when the location gets busy," Kreutz says.
Networking/TransmissionWANs. LANs. The Internet. Networking can be complex and confusing, so connectivity specs are extremely important. An in-house information technology (IT) specialist can also be helpful.
"The security professional must make sure that the system he orders has the communications capabilities the customer needs," Redtree says. "The customer might use a telephone line, Ethernet line, or fiber optic line to connect his digital video surveillance system to remote users' personal computers. When ordering the system, be sure to specify the communication capabilities desired. If he plans to use a dial-up telephone connection to his digital video surveillance system, he will need to have a modem as part of his system." Also, those customers that request TCP/IP protocol to transmit over WANs, LANs or the Internet will also need factory-installed networking cards, which require proper configuration.
"When transmitted digital video reaches its destination, the hardware and software of the receiving computer must be compatible with that of the transmitting digital video server. This compatibility is the digital video surveillance system manufacturer's responsibility. The security professional should investigate how this is accomplished at the video transmission destination," Redtree adds.
"If the video will be accessed on a network, it is important to know how the video will be used," Shuman says. "Will the user be utilizing the system to view live video or will he be using it to search for specific events? It's also important to make sure that the system can view live or recorded video while still recording. Consequently, if the security professional plans to use the system over a network, it is critical to get someone involved from the company with a working knowledge of the network at hand.
"Most companies have at least one IT professional on staff. A good security professional will get the IT staff involved early in the process in order to deal with the network issues before time-consuming problems arise. For example, using a digital video surveillance system over a network will require static
IP addresses that the IT professional will
need to provide. The installer should not wait until he or she is onsite to get this necessary information," Shuman says.
SIDEBAR: Advantage: FiberTo meet larger bandwidth demands, dealers may want to consider using fiber optic technology for fast, efficient video transport. The need for longer cabling applications, as well as better image quality, is reason enough to consider fiber for your next install.
Fiber optic video transmission offers a number of benefits, the most common being increased video transmission distance with little or no loss of signal quality when compared with coaxial cable. Ranges to 60 kilometers are not uncommon. Another benefit is the electrical isolation that fiber provides for grounding and lightning related problems. Because of its low attenuation and signal quality, fiber allows for much longer intervals of signal transmission than metallic-based systems. It requires fewer repeaters over a given distance than copper wire to keep a signal from deteriorating. Fiber optic cable can support much higher data rates and at greater distances than coaxial cable, making it ideal for transmission of series digital data.
Looking at the Benefits
Fiber is also non-conductive and non-corrosive. It is highly immune to electromagnetic interference (EMI), which makes it a viable choice in areas of high radio frequency (RF) and EMI interference. Fiber transmission equipment offers cost-effective ways to combine many video and data signals on a single fiber, thus reducing the cost of a transmission system from both an equipment- and installation-cost point of view.
"With the growing trend toward the integration of CCTV, alarm and access control systems, security professionals should view fiber as the only transmission solution for complex systems. The integration of video, voice and data will continue to present bandwidth demands that can only be satisfied with fiber optic transmission systems," says Jack Fernandes, president and CEO, American Fibertek, Inc., Somerset, N.J.
Fiber carries some burden of misconception in that is believed to be out-of-the-budget expensive.
"Higher-quality video transmission techniques at lower cost has made fiber a more attractive solution in many applications,"says Mike Girton, senior applications engineer, Optelecom, Gaithersburg, Md. "New digital methods of transmitting 4, 8 and even 32 channels of video on one fiber at near broadcast quality have been developed. Pricing on these products is below the cost of copper techniques and older analog fiber methods. The trend is more video, more data, more flexibility on existing fiber."
In the security market, fiber is used typically when coax becomes too expensive to do the same job, or cannot do it at all. It is not related to the size of the application, but more to the specifics of a given system configuration. All vendors tend to solve problems with the least expensive solution. If standard copper connections methods are not suitable for a given application, fiber is the next choice, Girton explains. Also, fiber is relatively easy to install and is very durable. "The biggest myth with fiber is that you need to be a sophisticated installer to terminate the fiber or put connectors on the end. As the termination equipment becomes easier to use, it is as almost as simple as putting on a coaxial connector," says Andy Acquarulo, president and senior engineer, International Fiber Systems, Newtown, Conn.
New system management hardware and software permits one person to manage and troubleshoot the entire fiber system from one location, reducing the resources necessary to troubleshoot and repair problems.
SIDEBAR: The Age of Digital Video SurveillanceThe complexity of remote video security systems has deterred many potential customers. They require at least one time-lapse recorder, a duplex multiplexer, individual joystick controls for each PTZ (pan/tilt/zoom) camera location, a matrix controller for multiple camera locations, POTS or ISDN remote video surveillance, monitors, LAN and WAN computer connections, and more cables and wires than anyone would want. The good news? All this has changed.
Delta Surveillance, a security and surveillance firm headquartered in Memphis, Tenn., offers a digital video surveillance unit that incorporates the above items plus more into a single box. The unit is manufactured by Dallmeier and distributed by ELMO, the exclusive U.S. importer and distributor of Dallmeier HD (hard drive) recorders. According to David Robinson of Delta, this system "replaces multiple time-lapse recorders, a full-featured duplex color multiplexer with camera motion detection alarm features, POTS or ISDN, LAN and WAN connections as well as matrix camera controls such as multi-point PTZ camera controls." As if this weren't enough, according to Robinson, the system "greatly reduces the cost and amount of labor needed for installation."
Prior to distributing the system, ELMO approached Delta and asked them to run it through every test they could think of. The idea was for Delta to identify problems and make suggestions about how the unit could be improved. After a month-long series of tests, Delta concluded that the unit worked flawlessly.
So what does a system such as this cost? According to Delta, their Eagle Watch Network Digital Surveillance system costs less than a single mid-priced 96-hour time-lapse VHS recorder, a color 16-camera duplex multiplexer, and the least expensive 16-camera remote surveillance equipment on the market. What's more the digital recorder supports up to 18 cameras - two more than standard 16-camera systems. This means that the system can have two more cameras without the substantial expense of the additional matrix required with 16-camera systems.
With digital video recorders, there is no tape to rewind, change, purchase or stock. Recording goes directly onto the hard drive. If the system has more than one internal hard drive, uninterrupted recording is possible. When one drive is filled, recording instantly goes to the second drive, and then the third. Recording and viewing can take place simultaneously - there are no gaps. "Hot swappable" hard drives can be changed even while the unit is running.
SIDEBAR: 7 Qualities to Look for In a Digital Video Systems Supplier1 - The system must be easy for customers to use. "A combination of hardware and software features that enhance user's operation, viewing, storage and retrieval with the system are imperative to create additional, future sales and eliminate call-backs," says Darren Nicholson, national marketing manager, Kalatel, Corvallis, Ore.
2 - The system must be easy to install. Do different components within the system mix and match with each other, allowing the dealer to create specific systems for specific needs? Are instructions for implementation easy to follow? Does the provider offer support and guidance on new software and hardware? Nicholson asks.
3 - The system must be easily modified and upgraded. Does the system provide the modularity, flexibility and scalability to start small and grow easily in the future? "You do not want to be pulling out old equipment to add new options and capabilities."
4 - The system must integrate with other major brands. "You cannot afford to be tied to a proprietary system. Dealers need to be able to integrate the system across lines. Perhaps the customer will acquire another company with another system. Dealers don't want to have to pull equipment to integrate the company. Dealers need to be able to take advantage of the latest and best new products or pricing. Cross-company integration allows this," Nicholson states.
5 - system should be digital or have the capability of going digital. "That's where the market is going," he notes.
6 - The provider should have professional marketing materials and provide pre-sales support. "Dealers want to propose their solutions in a professional manner. Does the provider offer specifications guides, colorful literature that an end-user not conversant in surveillance systems can understand, a Web site that is easy to migrate and people that will provide guidance on the products and solutions to offer, if wanted? Are deliveries on time? Does the provider promote only those products that are available to ship now?"
7 - You will need after-sales support. "If something goes wrong, will the provider back you up, help with troubleshooting and honor warranties? Likewise, does your provider consistently introduce a slew of new opportunities, both in products and programs, which will help you sell additional solutions to your present customers?" Nicholson questions.
SIDEBAR: Why Do Digital?There are four primary components which differentiate digital recorders from VCRs, video professionals say.
The first component is image quality. "The quality of digitally recorded images is determined by the image's compression ratio, spatial resolution, compression format and color traits. The digital image can be easily enhanced and reproduced without sacrificing the quality," says Charlie Mannix, vice president of product development, Integral Technologies Inc., Indianapolis.
Memory is the second component. "Digital recorders store video on an internal hard drive, just like that found in a personal computer. For example, a digital recorder with a 100 gigabyte (GB) hard drive can store more video than a 25GB," Mannix says.
However, the video can be archived to another tape medium if necessary.
The third component that differentiates the digital recorder is its activity detection capability. "Research shows that it's very unusual for a business environment to have more than 20 percent motion throughout a day. For example, in a 24-hr. grocery store, customers may be in the snack isle on average three minutes every hour. While a time-lapse VCR would record all 24 hr., the digital system would record only the 72 min. of activity. By default, activity and/or alarm-based digital recording only captures footage that is useful to the CCTV user," he notes.
The final component - and perhaps the single most important asset - is a search mechanism. Because a digital recording system can be set to record only when motion or an alarm occurs, the hard drive's valuable storage capacity is not wasted on hours of inactivity. As a result, searches are completed in minimal time, Mannix says.
"For example, a multiplexed time-lapse tape may require more than 15 hr. of searching to locate one desired frame. In contrast, a digital system may locate the same image in about 30 sec. In addition, the digital system tells the user the exact time that the event occurred.
"Because digital systems offer searching convenience, users are able to investigate incidents ranging from minor to major. With traditional video recording, users commonly face the dilemma of deciding whether minor incidents are worth the research time that is required. As a result, some small crimes may go undetected or unreported," Mannix says.
"Comparing the storage capacity of time-lapse VCRs to the new digital recorders is truly like comparing simple addition to algebra," he adds.