DVRs & VCRs For Your Business Needs

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All About DVRs - Digital Video Recorders & DVR Recording Technology

Just like cameras, DVRs come in different shapes and sizes. Below you will find lots of information on the many types of camera styles available from un, and in the marketplace.

1. A Brief History of Surveillance Video Recording Technology
2. Common DVR - Digital Video Recorder - Myths
3. What is a Security DVR?
4. PC-Based Vs. Non-PC-Based DVRs
5. All DVRs are Not Alike
6. Frames / Images Per Second
7. DVR Image Resolution
8. Video Quality Vis- -vis Frames-Per-Second
9. When Talking Data, Size Matters

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A Brief History of Surveillance Video Recording Technology

You will quickly learn that all DVR’s and surveillance solutions are not alike. Quality, performance and reliability vary widely. It’s not what the manufacturers and installers do tell you, rather what they omit. The object of this guide is to make sure the products and solutions you specify meet your required overall objectives.

Prior to the digital age surveillance video was recorded on videocassette recorders (VCR’s). Since videocassettes don’t store more then several hours of video on a traditional VCR, time lapse recorders were used. The time lapse recorder may record a single frame of video each second or even less, instead of 30 frames per second, which is live motion. With a single frame of video being recorded you only had to change the tape once every 4-5 days. The only problem there was:

• someone had to remember to change the tape when it ran out
• since only a single frame or less was recorded many times you missed details of an incident
• since the tape was recorded over and over the video quality became poor very quickly
• tapes would break and jam
• machines wore out quickly
• you had to go to the location to see the tape and could not do it remotely

Since you only wanted one video cassette recorder, the question was how am I going to record multiple cameras? After all, if I need 16 cameras was I going to have to buy 16 time lapse recorders? The answer was no. A piece of hardware known as a multiplexer or a quad was used, which would take all the video images and put them all on a single screen.

The quad or the multiplexer was a box with multiple video inputs on one side and a single video output on the other side. The problem there is imagine how small the images are and trying to see what happened, when an image takes up 1/16th of a screen; with no way to blow them up; good luck!

DVR technology for security began in the early-to-mid 90’s with mechanical-type devices. They typically were operated by remote controllers and buttons or dials on the DVR box itself. Easy to operate, their functions and keys were similar to a device users were already familiar with; the VCR. Unfortunately, due to technological limitations, early DVR’s were not reliable, had limited features, offered poor quality video recording and were not powerful enough or designed properly to provide solutions that could address managing large amounts of cameras and video. Customers required more capable and reliable systems, which resulted in the introduction of PC-based DVR’s.

The PC-based DVR brought enhanced features and were programmable, but the early models were plagued by inherent reliability problems and still did not have the requisite robustness in order to manage anything of substantial size.
Today, both PC based and non-PC based DVR’s and related solutions are much improved over their early predecessors. Considerable advances in digital video technology and equipment have opened as many doors to users as they present challenges and quality issues for manufacturers.

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Common DVR - Digital Video Recorder - Myths

Many people have the misconception that a PC-Based DVR is merely a PC with video capture (encoder) cards, display (decoder) cards and some off-the-shelf software. This explains the presence of hundreds of DVR and security companies that have literally sprung up overnight.

While these companies may hold themselves out to be “manufacturers” and security specialists - beware - few can deliver what they promise. In later chapters, we will discuss some of the “sleight of hands” to throw the unknowing off the track- in the quest of anything to make a sale.
At a recent security industry trade show we attended there were hundreds of exhibitor booths with DVR's on display. In fact, it was difficult to find a booth without one. Many possessed attractive literature and some phenomenal marketing claims. However, many were unable to provide a live demonstration of their equipment and just limited it to a “canned” and “controlled” demonstration. Others, when trying to show the features listed in their sales brochures upon specific request, experienced problems.

A true DVR, meant for security, is a sophisticated system composed of specialized hardware, software and sub-assemblies with built-in checks and balances. It all must work in unison to create a robust and reliable solution. There is no margin for error. Down-time costs money.

Building a DVR surveillance system requires a dedicated team of software and hardware engineers, programmers and system designers, plus support personnel. They take years to develop and go through extensive testing.

So when a salesman tells you how their company manufactures the product and is doing all these wonderful things and it’s a 2 or 3 person organization, well let’s just say it sounds a little hard to digest.

The fact is the majority of even the household names in the security business are ill equipped to manage the task. The obvious question is what seems to be the problem?

The obstacle for security companies is the mere fact that digital surveillance is an “IT” business. Information Technology is a world away from the culture that has been developed by these security companies, over decades. It is no longer analog cameras plugged into a VCR; rather, it’s IP, networking, fiber infrastructure, data management, encryption, security, firewalls, routers, bandwidth issues, etc.

It’s a completely different business and architecture that not in any way resembles the legacy analog technology. It requires different personnel, different skill sets, different cultures, etc. It’s the Flintstones© trying to operate in the Jetsons© age.

This may account for why 90% of the product peddled by the major security companies is nothing but private label solutions, to some extent, using third party technology. This explains the myriad of installation debacles prevalent over the last few years. When a problem arises, the reliance to resolve issues goes back to the true suppliers, which in many cases are half a world away in a foreign language.

This conundrum holds true on both sides of the fence. The surveillance buyer is ill equipped to understand the nuances and what expectations they should have. They are relying on the manufacturers to provide them with the appropriate information. Unfortunately, if the information is incorrect, how are you supposed to know?

Even professionals are confused as to what is and is not possible; what is and is not acceptable; what is coming down the road; and what technologies accomplish the goals required.

The amusing thing is sales people, installers and others from the old school are used to half day courses on learning a security product and often figure… ok, I will take a half day course in networking and PC’s and learn this stuff. It is much to their chagrin when they find out people attend school for years, just to learn the basics of IT.

When people approach us and ask can you teach me the basics in a morning session, our response is usually no problem and in the afternoon we can follow that up with a half day session on performing brain surgery.

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What is a Security DVR?

Unlike a VCR, the DVR has many advanced features and can also be operated and viewed remotely via local network (or even an Internet connection, which most regulators prohibit.) A Digital Video Recorder differs from a VCR in several important ways, some more obvious then others.

Instead of recording video and audio data to a tape, the DVR records to a computer’s hard drive or removable media such as a CD or DVD.

Computer hard drives (in DVR systems):

• Are more reliable (no tape jamming, degaussing or signal loss)
• Can store far more recorded material (weeks, months, years)
• Offer better video quality (tape wear causes signal loss)
• Are automated (no need to worry someone forgot to push the record button or change tapes)
• Protect data effectively
• Are automated (no need to worry someone forgot to push the record button or change tapes)

Negative aspects about cassette tapes (in VCR systems):

• Storage and individual tapes are bulky
• Video cassettes are vulnerable to loss of data
• Video cassettes have to be replaced frequently to maintain good quality
• Can easily be tampered with and data manipulated

There really isn’t much more of a choice any more, as the primary manufacturers of VCR’s have ceased production as of the end of 2005. Even videocassettes are becoming harder to locate.

Video and audio stored on a DVR can be:

• Accessed quickly and efficiently
• Viewed or retrieved locally or remotely
• Viewed simultaneously by multiple users
• Tied to alarm systems
• Authenticated for court admissibility

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PC-Based Vs. Non-PC-Based DVRs

One of the most frequently asked questions about DVR's is: Which is better a PC-Based or Non PC-Based DVR solution?

There isn't much that a non-PC based DVR solution cannot do today, which a PC-Based DVR can. The difference has more to do with the “footprint”. PC interfaces tend to be more user-friendly and less “mechanical.”

PC-Based DVR's tend to be more flexible and easier to manage. PC-Based solutions also tend to allow for upgrades of compression technology, which can be vital to the end user. Remember, in the IT world, you blink and they are onto the next technology.

Non-PC-based solutions tend to use “ASIC” (Application Specific Integrated Circuits) technology, which does not allow for upgrading of a technology platform, similar to your microwave oven. ASIC, is a chip that is custom designed for a specific application rather than a general-purpose, such as a microprocessor. ASIC, unlike an FPGA, has fixed functionality and is not re programmable.

In the PC environment, the latest technology utilizes DSP’s (digital signal processors). A DSP is a specialized digital microprocessor used to efficiently and rapidly perform calculations on digitized signals that were originally analog in form, such as audio and video. The big advantage of DSP lies in the programmability of the processor, allowing parameters to be easily changed.

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All DVRs are Not Alike

DVR's are not all alike. In fact, many are as dislike as automobiles. In the world of DVR's you can find the equivalent of a $10,000 Kia and a $100,000 Mercedes Benz plus everything in between. Both may be capable of getting you from point “A” to point “B” but that's where the similarities often end.

Using the vehicle analogy, if you buy a light weight truck it may be a fine vehicle for hauling small loads. But, if you load it up with 10,000 pounds of cargo and drive up and down hills all day you shouldn't expect a very long useful life out of the transmission or engine. It's not that it's a poor product, rather that's not what it was designed to do. Not unlike exotic and sophisticated foreign cars, many DVR's can be just as complex and temperamental.

Every ounce of computing power is critical. Digital video recording is a process intensive, multi-tasking application which can tax even the most robust systems. Along with processing power, a good DVR depends on equally robust related parts and assemblies. The famous saying in information technology is “you are only as fast and efficient as your slowest and weakest component.” If your system is not beefed up from end-to-end, from hardware to software, it will be underpowered, will under perform and it's going to break. Even worse, it simply will not deliver any reasonable quality or cause instability from the outset and probably never meet gaming requirements. I would not want to be the one that approved the purchase of a system that was just installed to only find out gaming has rejected it.

Unfortunately, there's no official consumer's guide to DVR's. It's difficult at best for most buyers to evaluate products on a fair comparison, or to even know; what are reasonable expectations.

Hobby and consumer class products often parade as commercial and business grade. Don't be fooled. You can buy a blender for your home for $25.00 but it is not the same as the $500.00 model at your local bar which may be responsible for making hundreds of perfect daiquiris and Margaritas every night, day-after-day.

Remember, surveillance you are either monitoring or recording 24/7 so that $25 blender equivalent won't do the job for very long, if at all.

Components become even more of an issue as you get into the large casino systems. Caveat emptor – let the buyer beware – all DVR's are not alike.

For buyers who do not have a lot of experience with DVR's, separating the quality from junk can be a daunting task. Often salesmen and brochures will conveniently fail to mention the things that their system won’t do. Often the buyer doesn't realize it until:

• The quality of the recorded video is poor under normal operating conditions.
• There is no ability to playback video in slow motion without distortion and choppiness.
• When you move the PTZ, the recorded video is blurry or blocky.
• You never looked at the video remotely over the network before you bought it and now you realize the remote video quality is sub-par at best.
• The recording and display speeds are not as promised.
• The number of days of storage is far less than specified.
• When you blow-up the video to full screen, the image is fuzzy.
• When you playback recorded video and freeze frames you see double.
• The DVR overheats itself as well as the room.
• The noise created by the system is deafening.
• The DVR’s are unstable and continue to reboot or shut down unexpectedly.
• You just decided to expand and purchased additional systems from the same company and they don't work with the old ones because the software or hardware is not compatible since they have no longer use the same supplier or technology platform.
• You can't practically control the DVR remotely from a workstation, as the way you
  thought it would operate.
• There is no way to burn disks of multiple cameras from different DVR’s on a single disk.
• There is no way to synchronize playback video from multiple DVR’s on a workstation.
• The networked video at the workstation is not real-time because its bandwidth intensive.
• Certain functions only work under limited or ideal conditions and render other
  features inoperable.
• There is no one – (at least locally) - to support the product that is technical

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Frames / Images Per Second

Let's give you a quick lesson in translation and calculation of video “speed” or “frame rates.”

Some manufacturers use different expressions when identifying the speed capabilities of their product. It will become increasingly apparent why this is misleading.

• Thirty (30) “frames-per-second”(abbreviated as “fps”) is “real-time,” ”real-motion” video in the NTSC (North America) video standard.
  
  
• Twenty-five (25) “frames-per-second”(abbreviated as “fps”) is “real-time,” ”real-motion” video in the PAL (International) standard.

This is not to be confused with “fields-per-second” (also abbreviated as “fps”). Unfortunately, two (2) fields equal one (1) frame. So when a manufacturer states “30 fps” on their literature are they talking fields or frames? Are they talking about each channel of video or total capacity of the system? Are they talking about the system limitation or the operating capability?

When comparing a DVR's fields (FPS), images (IPS) or frames-per-second (FPS); display, recording or playback performance claims; be careful to take into consideration all the factors that will apply to your particular application. Once again, manufacturers' claims may be based on “optimal” conditions and have little to do with reality and what you are trying to achieve. So always check to see if the total number of FPS/FPS/IPS quoted is for the entire DVR capture card or is it on a per channel basis. Is it for display and record? You simply have to test it anyway, as claims are just that; claims. Besides if you don’t the regulators will.

It’s kind of like the MPG sticker on a new car. Do you know anyone that ever got that kind of mileage? Not unless they were going downhill, in neutral, with a strong tail-wind!

Remember also what you are viewing live has nothing to do with the recorded quality, they are separate and distinct. So watching a live picture has little value, although if the live video is poor you are already in trouble.

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DVR Image Resolution

Image resolution describes the detail an image holds. The term applies equally to digital images, film images, and other types of images. Higher resolution means more image detail.

Image resolution can be measured in various ways. Resolution quantifies how close lines can be to each other and still be visibly resolved. Resolution units can be tied to physical sizes (e.g. lines per mm, lines per inch) or to the overall size of a picture (lines per picture height, also known simply as lines, or TV lines).

A television or raster image display with 525 scan lines makes a picture with somewhat less than 525 TV lines of resolution.

The term resolution is often used as a pixel count in digital imaging. But when the pixel counts are referred to as resolution, the convention is to describe the pixel resolution with the set of two positive integer numbers, where the first number is the number of pixel columns (width) and the second is the number of pixel rows (height), for example as 640 by 480.

Another popular convention is to cite resolution as the total number of pixels in the image, typically given as number of megapixels, which can be calculated by multiplying pixel columns by pixel rows and dividing by one million. Other conventions include describing pixels per length unit or pixels per area unit, such as pixels per inch or per square inch.

NONE OF THESE PIXEL RESOLUTIONS SUCH AS 704 X 480 OR 640 X 480 ARE RESOLUTIONS THAT DEFINE QUALITY, EVEN THOUGH THEY ARE WIDELY REFERRED TO AS SUCH; THEY MERELY SERVE AS UPPER BOUNDS ON IMAGE RESOLUTION.

A pixel (short for picture element, using the common abbreviation "pix" for "picture") is one of the many tiny dots that make up the representation of a picture in a computer's memory. Each such information element is not really a dot, nor a square, but an abstract sample. Pixels in an image can be reproduced at any size without the appearance of visible dots or squares; but in many contexts, they are reproduced as dots or squares and can be visibly distinct when not fine enough.

A pixel is not a little square. A pixel is generally thought of as the smallest complete sample of an image. The definition is highly context sensitive; for example, we can speak of printed pixels in a page, or pixels carried by electronic signals, or represented by digital values, or pixels on a display device, or pixels in a digital camera (photosensor elements). This list is not exhaustive, and depending on context there are several synonyms that are accurate in particular contexts. We can also speak of pixels in the abstract, or as a unit of measure, in particular when using pixels as a measure of resolution, e.g. 2400 pixels per inch, 640 pixels per line, or spaced 10 pixels apart.

The more pixels used to represent an image, the closer the result can resemble the original. The number of pixels in an image is sometimes called the resolution, though resolution has a more specific definition.

Confused and wondering why go through all this explanation? Well be prepared it only gets more confusing. But call us and we'll help you understand this.

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Video Quality Vis- -vis Frames-Per-Second

The number of frames per second has nothing to do with the image quality. While 30 frames per second is real time in NTSC, it is made up of 30 individual snapshots of sort. So while a video recorded at 5 frames-per-second has 1/6th the number of images, it does not have 1/6th the quality; it merely has fewer snapshots (that is of course if everything else is equal – such as bitrate, resolution, etc.) Remember, it is nothing but a succession of still images.

So why is there a need to record in real time? After all human beings don’t move that quickly, or do they? We are not recording speeding cars. One answer is from a prosecutorial standpoint, what happened in between, if you are not looking at the whole picture. If you are recording in real-time, there is no room for hypothecations by the defense lawyers. Further, a more detailed picture can make it easier to identify sleight-of-hand movements. You are also going to find that older technologies have trouble with slow motion and smooth playback under those conditions, so higher frame rates tend to compensate for some of the shortfalls, but not all. In reality unless it’s mission critical applications 5 frames per second is more than enough to accomplish the task, which is what many bank and institutions use; some even less.

A still shot from a recording at 30 FPS will look the same as one at 5 FPS

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When Talking Data, Size Matters

A file is a collection of data. File size refers to how much data is contained in this single unit of measure. The larger the file size, the more bandwidth (the amount of data that can be transmitted in a fixed amount of time) and computer resources are required to display, record and transfer a file.

Conversely, a smaller file, of the same amount of data, will use fewer computing resources, display and record more effectively and will transfer across networks more efficiently.

The size of a file of video data can be affected by image size (resolution), bitrate, motion, compression and various other factors, as previously discussed. Ultimately this can affect the amount of video you will be able to store on the DVR's hard drive and overall performance when viewing and recording multiple cameras simultaneously. As cautioned previously, beware of performance claims; they are usually referring to results achieved under the most optimal conditions.

As a rule, the higher the compression ratio, the smaller the file size. The smaller the file, the less sharp the image, the quicker the transmission speed, the less storage space and processing power required. Conversely, a lower compression ratio results in a larger file size, sharper image with a slower transmission speed and more storage space and processing power required.

A good way to understand compression is to think of the printer attached to your computer. If you print with a higher resolution the quality is better but it takes longer to print because:

• there is more processing power required
• more memory to buffer
• more dots per inch to process
• more ink (data) to lay down

Using a lower resolution which generates lower quality is faster because:

• there are fewer dots to process
• less memory to buffer
• less ink to lay down

This reverts back to a previous issue of speed claims. When they say your printer prints 20 pages per minute, it's usually not based on the highest resolution or with full pages of ink coverage, but the maximum possible on low resolution with the manufacturer's definition of “normal” print coverage. Again, like the MPG ratings!

The fact is, older compression technologies produce larger file sizes, since they are not as efficient as the newer technologies. Accordingly, they require more processing power, which begs the question; can it generate enough power to provide a working solution with such large file sizes? The answer in most cases is a resounding, no. This is why many manufacturers will use multiple pieces of hardware with fewer channels of video to try to compensate for the shortfalls.

Newer compression technologies can compress video more efficiently and therefore result in less power required across the board. This is why in many cases older technologies are more expensive then the latest; because the storage requirements can be as much as 3x greater, as well as the amount of equipment.

Large file sizes bring several interesting challenges for your DVR solution. One primary concern is the majority of DVR users want to be able to watch video remotely. So the video must be transmitted across a network. As such, bandwidth becomes a major concern and in some cases a mathematical improbability for older technologies.

We return to the garden hose analogy. If the garden hose can only accommodate one gallon of water per minute (e.g. your network connection) and you are trying to pump water from a source (e.g. the video data stream) which requires 3 gallons per minute we have ourselves a physics problem.

The water (video data) backs up (latency). Now let's add to the conundrum, what if you wanted to receive water from another source at the same time (video data from multiple DVR’s simultaneously) – the result is the throughput has been further cut. In terms of video what you end up with is chopped up and sometimes frozen images.

The bit rates below are for uncompressed color frames at 30 frames per second NTSC:

CIF 36.5 Mbps
2CIF 73.0Mbps
4CIF 146.0Mbps

What do these numbers mean? A single 4CIF uncompressed image is 146Mbps. Typical network cards can only accommodate a maximum of 100Mbps. Therefore, a single camera would ostensibly surpass the capacity of the network. So what happens when you have to transmit multiple cameras? The answer is, it cannot handle it. While there have been improvements in network cards which now approach Gigabit speeds (1000Mbps), there is still the issue of the capacity of the encoding and decoding cards. They simply cannot handle the task. The processing power is too great. Therefore, in order to transmit camera images compression technology is utilized.

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