CCTV in the real world: designing systems for people who use them: Sometimes experts get so caught up in the features and buzzwords that they forget an important element in any CCTV system: the people who use them.
Aug 1, 1997 12:00 PM, Robert D. Grossman
We all live in the real world, but few of us actually work there. Think of that the next time you push a door that you should have pulled to open, try to unwrap the cellophane from a new compact disc, or fill out a form by writing above the line you should have written below.
Some of the most usable systems I have ever seen were put together by people who said over and over again, "I don't know anything about this, but shouldn't we ." and then came up with a suggestion based on the specific application and common sense, not years of experience. Conversely, I have seen the same mistakes repeated over and over again by the "experts."
This article will discuss two aspects of CCTV: the elements of CCTV systems design that many of us don't think of but annoy the people who use our systems day in and day out, and some of the high-tech features and buzzwords, and what type of user benefits from each.
How today's CCTV user was born To understand where a design can go wrong, it is important to step back and look at the evolution of the closed circuit television (CCTV), consumer electronics and entertainment industries. Although they are not a combination we ordinarily put together, there are several interesting parallels that brought us to where we are today.
The original CCTV systems were built using equipment intended for other uses, primarily broadcast or industrial television. Cameras were large, expensive and power hungry and required frequent maintenance. Tubes had to be changed every 12 to 18 months, and the heat the units generated allowed this fledgling industry to look upon service calls as a continuing and lucrative revenue stream. Only the well-to-do purchased video surveillance systems, as the cost of buying and maintaining this equipment would otherwise cost more than the items to be protected.
In the mid-1960s, CCTV started to evolve as an industry. Donald Horn, who eventually formed Vicon, short for Video Control, in 1967, tinkered in his garage and invented the scanner, or motorized pan-tilt device, which allowed a camera to see in many directions, and the motorized lens, allowing remote control of zoom, focus and iris adjustment. These inventions reduced the number of cameras required to cover an area.
In the consumer electronics market, video rentals and the amateur videographer were coming on the scene. VCRs changed from a pricey luxury to a necessity, and inexpensive CCD cameras were married to lightweight portable VCRs, creating the camcorder. Suddenly there was a mass market for products that had previously only been enjoyed by the well-heeled. The dramatic reductions in price and improvements in quality continue today, with mass merchandisers selling do-it-yourself CCTV systems at the low end and major suppliers offering an ever-increasing array of features, bells and whistles at the high end.
At the same time, broadcast television and movies were becoming more and more sophisticated. Cable television became a household word in the mid-1970s with an easing of restrictions and increasing availability. Further programming and audience growth came in the early 1980s, when the government moved to deregulate the industry. The plethora of channels available raised the bar in terms of expectations for video quality.
>From this melting pot step today's CCTV users. They are not intimidated by buttons and will happily press them all day long. Crisp, clear video images are taken for granted, as are time-shifting and reviewing videotapes. The available choices in equipment increase daily as the prices continue to drop. And, if this wasn't enough of a challenge, the blinking clocks on the front of their home VCRs are a testament to their unwillingness to read manuals. This video boom has created a generation of people with expectations a penchant for instant gratification.
The importance of a plan In looking at our users and the events that conspired to create them, we must recognize the tremendous variety of situations in which they can be found. CCTV today does not always mean the double-naught spy material of James Bond or the vast sums of treasure found in a vault. It can mean a single camera in a convenience store, a traffic control system on the interstate, a system for viewing license plates at a toll booth or guiding airplanes into gates, the high-tech systems found in prisons, casinos and nuclear power plants, or anything in between. The more thought that is given to the intended use of the system, the closer we get to having the system function perfectly for that application.
Whatever the use, several common elements must be addressed. I divide a system into three categories regardless of size: system viewing and control, device selection and placement, and event documentation. They are equally important to each application and, to complicate the issue, all of them must be addressed simultaneously.
System control The most critical information needed for a system design is not what will be covered, how many cameras or any of the other obvious questions. It is simply, "How will the system be used?" Selection of devices, numbers of monitors, recording methods - all of these issues depend on the intended usage of the equipment. It makes no sense to tape things that will never be played back, install pan-tilt cameras that will never be moved, or provide monitors that no one will look at. The operation of the equipment is the driving force behind the selection of the equipment and yet is often ignored.
I always try to see whether the system will be used for surveillance or security. Although these terms are often used interchangeably, I define them as follows: security watches things; surveillance watches people. If you ha ve cameras in a warehouse and you are looking to see why you are coming up short on widgets every month, you are using a security CCTV system. If you need to keep an eye on Mike Tully, the infamous widget collector, you are performing surveillance. Surveillance systems rely more on control of devices; security systems typically have more fixed cameras and recorders for later review and examination. Although a system may be designed to perform both functions or have certain areas leaning toward one method or the other, a system designed strictly for surveillance will perform poorly for security and vice-versa.
To determine the intended usage, ask some pointed questions. How will the system be usedWill operators be specially trainedWill the console be manned at all timesHow important is the unattended recording of certain camerasFor an easy, seat-of-the-pants method of determining system functionality, see the sidebar, "The Surveillance vs. Security Quiz." Once the intended purpose has been determined, the environment may be designed to handle that functionality.
Security Security systems often rely on unattended recording. Because an operator may be called away at any given moment, the ability to go back and see the "tale of the tape" is critical. Systems left unattended are strictly security systems. They are also characterized by more fixed than movable cameras and frequently rely on many monitors with the intent that operators may see something out of a corner of their eyes.
A security system will have more automation than a surveillance system. Cameras with associated alarms may automatically pop up on assigned monitors. Monitors can often page through a sequence of related images (one monitor may show egress points while another shows hallways). Integration with other systems, such as access control and intercom, are more prevalent here.
Operators on security systems are rarely dedicated to CCTV functions. CCTV functions may be part of their duties or a slot on the schedule rotation. They are less familiar with the equipment and rely more on identification labels, graphical user interfaces and other ease-of-use features. On smaller systems, turnover may be high or system control may be as time permits.
When designing these systems, keep in mind that the videotape is of primary concern and operational features are secondary. They are looking to view an event after the fact and will rarely catch anyone in the act. The "wall of monitors" approach so familiar to appliance store aficionados is often effective; the operator is looking for change rather than function and can spot things amiss from the corner of an eye. PTZ devices are often used as backup, and today's domes with on-board alarm processing are effective at acquiring a target automatically when events occur.
Integration with other subsystems must be accompanied by the appropriate titling and annunciation. If not, operators may think they did something wrong when the picture suddenly changes and "fix" the system so it doesn't happen again.
A byproduct of this type of system is the tinkerer. There is always at least one operator who takes a keen interest in the inner workings of the equipment and seeks to further customize it. This may seem like a lifesaver in that someone will actually read the manuals and be able to perform routine programming or system maintenance. However, this presumes that ability matches desire; otherwise that individual can be responsible for all sorts of bizarre and unpredictable system behavior. I have seen the tinkerer lock all users out of the system by deleting passwords, wipe out all programming, change the date format so March 1 becomes January 3 (MM/DD/YY changed to DD/MM/YY) and a host of other harmless and not-so-harmless puzzlers. A well-documented system configuration printout is critical in this application.
Surveillance Surveillance systems are as concerned with how it happened as they are with what happened. They generally are looking for deviations from established procedures; when they see them, they watch further to see what is going on behind the scenes. Fewer monitors are used, and screen size is generally larger. Pan-tilt devices are more prevalent, with the overwhelming choice being the discreet dome, to prevent subjects from knowing they are being watched.
Surveillance operators are generally dedicated to CCTV work and do not wear as many hats. They may not use as many features in the system as security operators, but the ones they use are accessed continuously. When you design for this application, performance, speed and reliability are critical. Videotape is used as backup and support but is not the only tool in the arsenal. The ease-of-use features are often dismissed as distractions; constant usage of the system breeds such familiarity that they are simply not needed.
Device selection and placement Moving into the second of the three categories, the interaction between the three design areas becomes more apparent. With the selection of devices we also must consider the way they will be viewed, controlled and recorded. If the system is to be unmanned for the most part, with a heavy reliance on recorded material, pan-tilt-zoom devices make little sense. Left to performing pre-programmed tours, they will invariably be pointing the wrong way when something happens. Many units will acquire targets rapidly, but all are limited to only being one place at a time. Fixed vs. moving is one of the first decisions to be made and will vary from camera to camera, room to room, and job to job.
With cameras, color vs. black and white is an easier decision. Monochrome cameras still offer better low-light response and a sharper picture, dollar for dollar. Many applications will not permit color; sodium vapor lights used in parking lots and garages cast an orange hue that will render any color information useless. Rooms with two strong light sources - sunlight through a window and bright fluorescent lighting - will not allow a color camera to accurately white-balance.
Color, on the other hand, aids tremendously in identification of people and objects. Sometimes these added visual cues can be more hindrance than help. During a major incident at a well-known casino, I once watched surveillance operators describing a suspect to security guards attempting to apprehend him. The tan jacket, blue patterned shirt and blue jeans were all accurately described, and after much confusion ("that jacket was gray, not tan") the suspect was apprehended. What amazed me at the time was that no one even mentioned the eye patch the suspect was wearing, a clue that would have been less prone to personal interpretation.
Although the color vs. monochrome debate is still an area of strong personal preference for end users, the trend is toward color. Careful consideration of environmental factors will prevent your choice from becoming a mistake.
I am amazed at how many projects are installed without the use of camera housings. In my opinion, without exception a camera should always be in a housing. Cost should not be a factor; if the project warrants a camera, it should warrant a housing. If the price is particularly sensitive, you can use one of many low-cost units on the market. A housing makes the system look better, protects the camera, hides the fact that a camera is missing if it has been pulled for service or maintenance, and makes sabotage much more difficult and time consuming. Although this is always the first sacrifice to budget constraints, it is one that I try my best not to make.
Event documentation As with device selection, the manner in which the system will be operated determines the method to be used. If the intention is to log events for later review, it makes little sense to have a camera that is not going to be recorded. And if no one will ever play the tape, why have the cameras (or recording) at all?
When the decision is made to record an event, carefully consider how that will be done. There are many ways to accomplish this task, and many successful designs rely on a combination of technologies to meet their needs. As we review various recording methods, VHS is used as an example because of the overwhelming support and market share of this form factor. For a commentary on the state of digital video recording, see the sidebar "Digital Recording - Will Tomorrow Ever Come?"
To capture a moving image, the best alternative from a quality perspective today is always 1:1 recording (each camera has its own VCR), real-time (the VCR is continuously recording full-motion video) and high-resolution (S-VHS or equivalent). Anything else involves a sacrifice; because almost all systems consider expense and physical space, we wind up making a lot of sacrifices.
The first sacrifice is usually resolution or picture quality. For whatever reason, VHS is the standard despite a 40% loss in picture quality out of the box. VHS has the advantage of being less expensive and more readily available, although if the higher resolution format had been accepted by the consumer market, this would not be the case.
When we depart from 1:1 recording, we have two alternatives: screen division (or quads), and time division multiplexing. With screen division multiplexing, a quad divides the screen into four quarters (or quadrants) and places a separate, full-motion picture in each. This method provides several benefits: the space required is reduced because you have four cameras on one tape, review is easier because no decoding is required to play back the image, and the full range of motion is available. Drawbacks include loss of picture quality and the limitation of only four cameras on a tape. Some quads advertise recording of eight cameras, but beware; only four are recorded at a time, with the unit alternating between a "page" showing the first four and a second page showing cameras 5 through 8. The net effect is a loss of both time and resolution, or the worst of all possible worlds.
With time division multiplexing, a multiplexer distributes multiple cameras into the full-motion video stream of 30 frames per second (fps), placing one camera in each frame. The result would be a jumble of flashing images when viewed on a standard player, but this system reassembles each camera's image on playback with a decoder. Depending on the number of cameras recorded, the effect is either close to full-motion video or resembles the stop-action motion familiar to silent movie fans. Benefits include a tremendous reduction in tape storage, with the industry standard being up to 16 cameras per unit (some specialty units record more, but they usually require synchronization of camera signals, an expensive proposition), and full-resolution video. Many units offer digital manipulation of the picture with freeze frame, digital zoom and multiple camera displays common. (See figure 1.) The drawback is playback compatibility; a tape must be decoded to be viewed, and units made by different manufacturers are usually not compatible. You also lose fluid motion, which can be minimized by reducing the number of cameras fed to each multiplexer (three cameras are recorded at 10 fps; 15 are recorded at 2 fps) and by units that increase the refresh rate (frequency at which a frame is recorded) based on motion or external alarms. Time division multiplexing combined with 24-hour real-time or time-lapse recording requires further compromises to the refresh rate.
Now we further complicate the sacrificial process by tossing another variable into the pot: the tape speed and format at which the image is recorded. Here we split into four more categories: real-time, 24-hour real time, time-lapse and event driven.
Real-time records 30 fps, includes the three commonly available VHS speeds and allows eight hours on a tape using T-160 cassettes (most manufacturers recommend using six-hour T-120 tapes). This should always be the method of choice unless circumstances do not permit tape changes (i.e. a system left unattended for extended periods).
24-hour real-time is a newer format that reduces the refresh rate to 20 fps and the tape speed to allow 24 hours of quasi-full-motion video on a T-160 cassette. Newer units are available that allow as much as 40 hours of continuous recording. Tape wear is higher, playback compatibility is an issue, and some people complain of a flickering image (our eye is used to 30 fps). Many consider this better than time-lapse, but if the expectation is real-time, most will be disappointed by the quality.
Time-lapse is a method of pausing the VCR between recorded frames, spacing out the recording to allow as much as 960 hours (40 days) on a standard T-120 cassette. At the slowest speeds with long intervals, the recorded image will resemble a series of still images rather than a moving sequence of events.
Event-driven recording is a way of combining full-motion video with tape conservation. A VCR begins recording, usually in real-time full-motion, when an event is triggered (i.e. contact closure). This method is often combined with time-lapse to allow a logging recording to be sped up to full motion when something happens. Many people prefer this method because a tape may contain only actual events rather than long spans of empty hallways and rooms. Disadvantages are the difficulty in predicting when the tape needs to be changed (depends on the number of events recorded), and the fact that anything leading up to the triggered event is not captured. This problem often means valuable evidence is lost; in the case of someone breaking into an office, we may miss all the footage of the person's face as he looks through the window, but capture his back leaving the room once he is through.
Synchronized titling A final note in the design and selection of recording systems: pay attention to the time and date display. Many industrial VCRs have an internal time-date-title generator that superimposes the time over the on-screen image. If you are using more than one VCR, do not use this internal clock. Virtually every major CCTV system's house manufacturer has an external product to provide synchronized time and date for multiple VCRs. These will provide the same time and date generated by the surveillance system or will function as standalone equipment.
One of the main reasons for making a video recording is to provide evidence for a legal proceeding. With the VCRs independently generated clock, the subject being viewed can walk from one room (VCR A) to another (VCR B) and, according to the tapes, arrive before he left. In some cases, he may arrive hours or even days before! If your intent is to gather evidence, this is usually worthless. Be sure to do what is required so your material will hold up in court.
Putting it all together One of my pet peeves is that too many people do 95% of a good job. The software industry has a saying that the first 95% of the job takes 95% of the time allotted, and the last 5% takes the other 95%! Sometimes it seems that the work never ends, and if you don't stay on top of it, it never will. I have never had customers thank me for the 300 cameras that are working, but they will tell me about the three that aren't.
I think of the last 5% of the job in two ways. There are things that must be done to clear the punchlist, and there are the little details that make a system useful and differentiate your business from the competition. Punchlist items must be done if you want to get paid and they won't go away. If you ignore them, you can forget about all the hours you put in; your reference from the customer won't mention the fine job you did but will dwell on the missing fill panels, scratched faceplate, and the one VCR that eats tapes.
Little details will make your design work well. Do the overhead lights cause a reflected glare on the monitor screensWas the air conditioning system sized properlyAre there worklights behind the racks and extra outlets for soldering ironsDid you leave space for equipment expansionAlthough these aren't your responsibility, you are the only person who could have brought them all together and prevented a problem.
Designing a system that is effective and fun to use is both frustrating and rewarding. I recently went back to one of the first major casino systems I designed. I had not been there to see it in more than four years and was surprised to see how little it had changed. Some monitors had been moved and equipment had been added. I remembered working shifts as an operator while the final punchlist items were being resolved and making changes based on the feedback I received. The things I learned helped me with numerous designs; the fact that I was welcomed and not cursed as the designer of this original system showed that I must have done something right.
This article defines the difference between security and surveillance CCTV systems by stating that security watches things; surveillance watches people. To quickly determine which type of system you are working on, try the following quiz. Score 1 point for each yes answer; if your score is below 5, you are interested strictly in security; 5 to 8 indicates a system that may serve both functions; above 8 means big brother will be watching all.
o - Yes - o - No - The system will be manned at all times.
o - Yes - o - No - Operators will have a good understanding of the proper way to perform work being observed.
o - Yes - o - No - Operators will maintain accurate written logs of any events they observe.
o - Yes - o - No - Tapes being recorded will be spot-checked occasionally to see if anything suspicious has happened.
o - Yes - o - No - Viewing activity is the primary concern. There will be few if any functions for the operator to perform that will distract them from this focus.
o - Yes - o - No - Operators will not be rotated in and out of other assignments.
o - Yes - o - No - Operators will be discouraged from fraternizing with other employees.
o - Yes - o - No - Operators will be asked not to discuss their work responsibilities with other employees, friends or the media.
o - Yes - o - No - An operator will require a period of training and experience before becoming effective in the position.
o - Yes - o - No - It is more effective for an operator to concentrate on a few monitors than to casually observe activity on many.
"But what," asks your customer, "about digital recording Isn't that the next big thing?" Well, yes and no. Not today, but a distinct possibility in the future. Digital recording has two things going for it: quality and accessibility. The medium (digital) is not subject to the anomalies that plague analog tape: dropouts, stretch, humidity, mechanical failure, generational loss, to name a few. The jury is out on the reliability of digital media. Although steps can be taken to improve redundancy, the hard-drive recording systems used today do occasionally crash, and when they do, they have the potential of instantly vaporizing your trail of evidence. Video resolution can be higher, although if that were a burning priority, S-VHS would not be relegated to the niche status that it has become. And to be able to instantly recall an event without scanning through hours of footage is appealing to most people.
So what are the problemsWell, the three that come to mind are cost, cost and cost. Once again, the consumer market drives us. Until a format is accepted and popularized, the cost is prohibitive. One manufacturer of digital video recording systems was talking up the benefits of its system costing roughly $9,000 per channel of video. "We have no competitors," it exclaimed. Although prices continue to fall, in today's market, this company has a serious competitor: a VCR costing as little as $250, along with a shelf of tapes.
As the sophistication of high-end CCTV systems continues to grow, integration with other systems and equipment becomes a major consideration. With features comes complexity, sometimes resulting in systems that are unreliable and difficult to use. It is important to stop and look at functionality as well as specifications, and to separate the myths from the reality.
Let's take a look at some of these technologies and review their value in the real world. A lot of beneficial new toys are available, and hype surrounds them all. By understanding the applications for, alternatives to, and drawbacks of these new technologies, you will be better able to design and implement system solutions that work.
A strong house needs a good foundation Features are rarely added to systems on a whim. No one has ever come to you and said, "I have money to spend. What do you have for me?" You will either be asked to provide a specific technology, or more likely be given a wish list of desired functionality and asked to plug in the pieces that will make it work. Sometimes these will be an integrated package from the ground up; in many cases they will be added on to the existing system. In either case, be sure to kick the tires before going on a long trip.
The base system is critical to the success of the peripheral functions, but this point is often forgotten until it is too late. If a change must be made, bite the bullet up front rather than figuring out the cheapest way to do things and experiencing the back-end support nightmares that come from a poorly implemented design. If your system will use a high-level interface with other computers feeding information upon which your system is to act, be sure it is up to the challenge. For example, many older CCTV system designs use a single microprocessor for all functions. If an add-on will increase the amount of alarms to which the system must respond, the added burden may slow down existing functionality. You will be the unlucky sacrificial lamb, as the system was working fine before you started mucking around! In my experience, you are better off recommending system replacement or refusing to bid the project if there is a danger of degrading the existing functionality.
Communications Any device added to or included with a system must have a way of communicating with other components. This is generally done in one of two ways. Low-level communications refers to a contact closure or other dedicated trigger to signal an event. High-level communications refers to a dedicated link or data path between two computers. This is generally an RS-232 serial line and is usually handled by means of an ASCII data stream.
As an example, let's say that we want to report a door alarm to the CCTV system, and that all door alarms are currently run through the access control system. With a low-level interface, a second dry contact closure from the door contact is fed to a collector box somewhere in the building. When the door is opened, the contact closure is fed to both systems simultaneously, and each one reacts accordingly. The big advantage of this method is that the failure of one system has no impact on the other. The disadvantage is considerable; twice the wiring often means twice the cost, and a large number of doors are messy and expensive in terms of installation.
A high-level interface is much cleaner and simpler once the software issues
have been resolved. When the door is opened, it triggers the access control
system only. That system then sends a data stream to the CCTV system. (On a
Vicon switch, the ASCII stream
A further caveat to computer control of a system: You are better off
sending an alarm and letting the CCTV system respond than sending the
actual event. In the example listed above, there are two possibilities.
First, the access control system can send alarm 17 (
With all of this integration at the CPU level, care must be given to avoid a single point of failure at the system CPU. To avoid this, several CCTV manufacturers offer hot-standby switching, or a means of automatically substituting a backup processor for the primary one in the event of a failure. Although the intent is the same, these differ widely in implementation. The best systems handle communications between the main and backup CPUs so that both always remain synchronized. If the main CPU fails, the backup CPU is switched on-line automatically; when the main CPU is repaired or replaced, the backup CPU tests it, updates it and switches control back to it. A less sophisticated system acts as a "Y" cord, sending all commands to both CPUs simultaneously. When one fails, the other one is switched on-line. When the failed unit is repaired, it must be manually reprogrammed before being put back on line, allowing easy entry of the "oops" factor.
The graphical user interface At one time, the graphical user interface, or GUI, was the focus of all CCTV manufacturers' marketing efforts. Today, most manufacturers have them and they are - as they should be - another tool to be used where appropriate. A GUI is a computer-based (PC in all but one instance) means of controlling the system, usually by means of clicking icons on a map-based representation of the installation.
GUIs have instant appeal at the systems purchase level. They are sexy, high-tech and easy to understand, and almost everyone who sees them likes them. If an operator wants to see the camera in the third-floor lobby, he clicks on the building, then the map of the third floor, and finally the icon depicting the lobby camera. This, according to the people who write GUIs, is much simpler than pressing 71 and the CAMERA button on a keyboard. The operator no longer has to remember camera numbers, and anyone can control the system with little training or experience.
This argument works very well for many applications and falls short in others. A GUI is great in an area where there is high turnover, limited training and not a lot of concentration. As the operator gets comfortable with it, the GUI may become a limiting factor; they can improve to a point but no further. There comes a time when it is faster to enter the camera number, once you learn it, than to continuously click around maps. A GUI will get you from zero to 30 mph in no time at all, but you'll never exceed the speed limit in this fashion.
GUIs are also difficult to design and expensive to maintain in the case of frequent system changes. Someone who knows what she is doing must program them, and few dealers or end users have the manpower or inclination to dedicate a person to the task. As a result, many of them are only partially implemented, and others are outdated because the system evolution is not reflected in the software.
Digital intrusion detection It is ironic that one of the most useful, affordable and innovative tools available to a CCTV user is also the least used and understood. The company that I work for makes a digital intrusion detector, as do several others. We find that when we take the time to explain what it does and demonstrate the features, people immediately think of a thousand uses. As with life insurance, this is a product that is never bought unless it is sold - no one asks for one but everyone wants one.
The digital intrusion detector works by dividing a video image into rectangular blocks or cells that are stored as a reference image. Each block may be further divided into pixels, with high-end units splitting the image into more than 16,000 of these segments. The referenced image in memory is updated at a frequency set by the user, who also defines the detection zone. Detection takes place only in the exact area desired. Movement in the rest of the scene cannot trigger a false alarm if the camera and lens are properly set up. When a video level difference is detected, the sensitivity level setting determines whether an alarm should be generated. The alarm event then passes through software analysis to determine the object size and duration of event. If the alarm event passes through all evaluations, an alarm signal is generated by the system.
Because these units can be extremely sensitive and accurate, they are versatile. One common usage is known as museum mode, with an object of interest, such as a painting, being selected in a fixed shot of the room. People can walk in front of it, wave their hands, turn lights on and off and point to it without any ill effect. The moment the painting is removed from the wall (affecting the entire detection zone for a set duration) an alarm is triggered. Several museums and private art collections are effectively protected in this manner.
Virtual control rooms The idea of splitting one monitor into sections and letting it function as several dates back to the quad. However, the advent of inexpensive LCD projectors and the multiscreen displays on digital multiplexers have brought a whole new twist to the idea. A plain white wall can now become a bank of monitors, with no tubes to replace and minimal wiring. And, at the touch of a button, the configuration can be rearranged or an image can be instantly blown up to full screen. Digital zoom allows even further magnification of the image, and the effect becomes that of the viewscreen on the starship Enterprise. Try doing that with 16 rack-mounted 9 inch (229 mm) monitors!
The concept is simple. Dedicated switch outputs or individual cameras are fed to a digital multiplexer. The output of the multiplexer feeds a large monitor or LCD projector (rear-projection televisions do not work well because of the propensity of an image to burn into the three CRTs). By changing the mode of the multiplexer via the front panel or a remote control, the images may be resized, relocated or otherwise manipulated on the screen. Originally designed for gaming applications, this design is used in several casinos, hospitals and other facilities around the country.
The only drawback is that with today's technologies the best multiplexers on the market do not refresh each section of the screen in real-time. Since each section updates sequentially, the range of motion for each image is sometimes jerky or sporadic. In actual operation, some people prefer this method because it serves to accentuate movement and smaller details become more noticeable.
Image enhancement One catchall phrase bandied about by end users is image enhancement. Hollywood movies show the local policeman pulling a full-color face shot of a criminal out of a white shot of a football stadium, and end users want to do that too. The good news is that many of the tools exist to do this; the bad news is the time it takes to master them. An alternative is to put together several components to give the desired functionality.
Tape playback - The single biggest improvement that can be made is to provide a professional or prosumer (a hybrid combination of professional and consumer) VCR. This may offer a jog-shuttle wheel with precise control of transport functions. It will help with the input source quality, providing a better chance for everything downstream.
Time-base correction - Again, the prosumer line offers equipment that will stabilize the image and reduce generational loss when dubbing. Although this feature may be included in a high-end VCR, the better ones are purchased as a stand-alone unit. A time-base corrector will correct color shift and reduce tape dropout as well.
Image magnification - Many multiplexers provide digital zoom and freeze frame of an image. Most offer 2X magnification, with 12X being the most powerful currently available. These units allow the user to electronically pan, tilt, and zoom a fixed camera or tape playback. Be sure and look for a unit that processes both fields of a frame to create the image; many sample only one field and repeat it, sacrificing half of the resolution. This becomes more apparent as the picture is magnified; garbage in, garbage out.
PC with video capture board - Now we're getting into serious tinkering. If the staff is in place to go through the high learning curve, many commercially available software packages are available that will turn a relatively inexpensive multimedia PC into a graphics workstation. Be aware that it is difficult if not impossible to work magic on full-motion images; limit your wonders to the cleanup of individual frames. Also, no amount of technical proficiency will let the operator work at the speed of the movie stars. Forgive them their added time - they can't fly or conquer aliens either.
As the technologies continue to evolve, the marketing and salesmanship of many features will continue to blaze the trail. With each new "next great thing," we must make sure to understand the limits and capabilities before putting these products in front of our customers. Although many people profess to wanting the latest and greatest, everyone wants their system to work as advertised. And that concept is not likely to become outdated.
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