Megapixels and Math

For the better part of a year, women in certain sections of Brooklyn, NY dreaded the walk home from the subway. A pervert was on the loose, sneaking up from behind, grabbing and groping them. Although he’d been caught on a surveillance camera and the video broadcast on all the local news stations, he remained at large. Viewers could see a youngish man in a black hoodie approaching and attacking but no one came forth to identify him.  The problem was that the quality of the video made it hard to make out the attacker’s face. In a black hoodie and jeans, he could have been any one of thousands, no make that millions of youths.

This was because the camera that captured the incident was a low-cost surveillance camera a  bodega owner had mounted on the entrance to his store, an  inexpensive analog cameras with low resolution and slow frame rate,  probably meant more to deter hold-ups than to give high resolution detail. The culprit was eventually arrested but a megapixel camera would have captured his face in clearer detail and resulted in an earlier arrest. A megapixel camera would also serve the bodega owner better should he ever be robbed.

What is a megapixel? A megapixel is one million pixels. So maybe the question should be what is a pixel?

A pixel is generally thought of as the smallest single component of a digital image, a single point in a graphic image. The word itself is taken from pix meaning pictures and element, short for picture element.         
The way a digital camera creates this copy of a color picture is with a CCD chip behind the lens, constructed with a grid of many tiny light-sensitive cells, or sensors, arranged to divide the total picture area into rows and columns of a huge number of very tiny subareas or light or pixels. The quality of an image, its resolution is dependent how many pixels are displayed and conversely the number of pixels depends on the size of the sensor. If a user wants to see facial features or license plate numbers, megapixel cameras will capture the most detail.

Typical Megapixel Camera Resolutions

Megapixels	Resolution	Total Pixels
1.3	1,280x1,024	1,310,720
2	1,600x1,200	1,920,000
3	2,048x1,536	3,145,728
5	2,592x1,944	5,038,848

To clarify things (no pun intended), let’s take a look at the “lowest” resolution camera in the table. It packs a frame with 1,280 x 1,024 pixels for a total of 1,310,720 pixels or to phrase it differently 1.3 megapixels. The highest non-megapixel camera a D1 using NTSC standards delivers 720x486 pixels per frame for a total of 349,920 pixels, 73 percent less pixels than the 1.3 mega. Not only does the megapixel camera offer finer detail than a non-megapixel but, with the use of the right software and web browser, it can also cover a wider field with the digital zoom feature. Higher resolution and greater coverage seems like a win/win situation. By minimizing the number of cameras he needs, a business owner can lower his costs without compromising his surveillance.
There is something else larger business owners contemplating IP camera networks should consider. The clarity of detail is dependent on the grid size of the camera’s image sensor: the denser the grid, the smaller the pixel ,the smaller the pixel, the higher the total pixel count of the frame. Yes, this results in better resolution but it also requires more bandwidth and increases storage requirements. And that is where compression comes in.
Video compressing is the process of reducing and removing redundant video data so that a video file can be transmitted using the least amount of bandwidth and stored using the least amount of bytes. An algorithm is applied to the source video to compress (encode) it and for viewing, the inverse algorithm is applied to (decode) produce a video that shows virtually the same content as the original source video. A pair of algorithms that work together is called a video codec (encoder/decoder). In   networks where some analog cameras are installed, a video encoder must be installed as well but in most IP networks the encoder is embedded in the IP camera
In order to insure compatibility and scalability (the ability to add more cameras) a codec must fit a standard. Different video compression standards use different methods to reduce data, resulting in different bit rates (transmission speeds), different latencies (the time it takes to compress, send, and decompress) and different quality of the viewed video. Different designers can use different tools to implement compression (encoding) and this is fine as long as the output meets the standard so that it can be decoded.
The different standards used are Motion JPEG, MPEG-4 part 2, and H.264.Within these standards lie different levels or degrees of capability to limit performance, bandwidth and memory requirements. The higher the resolution, the higher the level required. However for now it is sufficient to remember that each standard uses its own  algorithms. Thus  a MPEG-4 encoder will work with a MPEG-4 decoder but it will not work with a H.264 decoder, since it uses a different algorithm, and vice versa.
In our next entry we will explore features such as HD, PTZ capability, low light resolution, and the part software plays. Meanwhile if you are considering a  megapixel or any other type of surveillance camera, contact Kintronics at 800-431-1658 for information and sales. www.kintronics.com.

Solve the Access Control Problem: RFID +AVI = EZ AX-S

In the time you spent figuring out what the equation in the title means, The Tagmaster access control system could have verified the ID tag mounted in your car window and raised the entry arm to the parking lot.

 In case you’re still decoding, the answer is Radio Frequency Identification plus Automatic Vehicle Identification equals easy access. 

RFID is a tracking and identification solution using a wireless no-contact radio system to transfer data from a tag attached to an object for purposes of automatic identification. Unlike the ubiquitous barcode with its machine-readable parallel bars that store binary code, TFID tags have read and write capabilities. Thus data stored on them can be changed, updated, and locked. Another difference between the two is that while a bar code can only be read within line of sight, the RFID tag contains electronically stored information that can be read from yards away.

RFID when it was introduced in 1970, like any new technology, proved to be too expensive for wide usage. The transportation industry was among the first to adopt RFID tags, using them to to track large items, like cows, railroad cars and airline luggage, that were shipped over long distances. Mass production and time have lowered the cost and many business sectors have adopted its usage. The auto industry makes use of RFID tags to track the progress of an automobile through the assembly line. Pharmaceutical companies track drugs through their warehouses. Retail stores have adopted the technology to track inventory for stocking and marketing purposes. And it has become quite commonplace for employers to issue RFID tags in the form of access cards for entry to gated parking areas. This brings us back to the equation involving RFID and AVI.

TagMaster, a Swedish public company was a pioneer in the development of long-range identification systems uses radio frequency identification to identify vehicles at long distances with accuracy and speed. They have used the technology to effect secure and non-intrusive vehicle access control. At its most basic, a system is composed of a tag which holds the bearer’s unique identification data and a reader which can transfer the data for verification against a data base. Let’s take a look at one configuration.

The Reader

The LR-3, specially designed for parking applications, is a long range reader that operates on a 2.45 GHz radio wave frequency. It can identify ID tags as far away as ten feet. Thanks to its compact size it can be mounted on a pole or directly on the lane. The LR-3 requires a power supply ranging from 10 to 28V, and can be easily integrated into an existing access control systems using standard interfaces.

The ID tag

The ParkTag is partnered with the LR-3 for parking applications and operates on the same 2.45GHz frequency. When placed in the provided WinFix holder sleeve the tag’s information is read by the LR-3 as the vehicle approaches a lowered barrier or closed gate, and if verified, the driver gains access without ever taking her hands off the steering wheel or coming to a full stop. The ParkTag has a predictable three year life.

Tagmaster also has a solution for employees needing access to locked buildings and high security areas after they have parked their cars. 

 The CombiTag offers long range RFID enabled vehicle access as well as short-range personal access when installed with a selectable proximity solution such as HID’s IClass technology. The driver drives in to the parking facility with the CombiTag in place, then, once he has gained entrance takes it out of theWinFix holder on the windshield to use as a badge to enter any locked building or high security area whose entry doors are equipped with a proximity reader. There is no need to fish in purses or jacket pockets at the last moment.

If you are interested in finding out more about long range identification and access control feel free to call Kintronics at 800-431-1658 or visit is at www.kintronics.com

Analog Cameras vs IP Cameras: The Evolution of Resolution

Today we take a look at how your choice of an IP-based system of digital cameras or a CCTV system of analog cameras will impact the resolution of your surveillance video. 

Historically resolution was understood to mean limiting resolution or “the point at which adjacent elements of an image cease to be distinguished.” But the introduction of digital thickened the plot. For  our purposes, when we refer to a camera as being analog or digital we will be referring to the type of transmission it uses to send video to a computer or storage device: 

§  Analog transmission takes the video signal and modulates it into a continuous signal, amplifying its strength or varying its frequency then transmits it through coaxial cables to a security station for viewing on a PC or recording.  Upon reaching its destination, the wave is converted back to the original video signal. The term analog stems from the fact that the variations in the carrier wave are similar or analogous to that of the video signal itself.

In analog the term horizontal lines of resolution is important in understanding the clarity of an image. Horizontal resolution cannot be looked at without considering vertical resolution.  Horizontal resolution defines the capability of the system to resolve vertical lines thus affecting the clarity of an image on the screen. The vertical resolution is fixed by the standards defined by NTSC (525) or PAL (625 lines).  The terms originated with television and the test pattern below harks back to the good old days of TV. 

Engineers add converging vertical lines until they reach the point where the lines can no longer be distinguished one from another. This is called the measured resolution point. At this point the maximum resolution of the TV has been reached. Because the lines are stacked from left to right, the number of discernible lines across on the screen is called the horizontal resolution. This is expressed in a ratio. A television system with a 4:3 aspect ratio expresses the number of distinct vertical lines, alternately black and white which can be satisfactorily resolved in three quarters the width of a television screen.

Like TV, analog cameras use horizontal resolution as a measure of clarity, and since today’s cameras adhere to  established standards, the same number of scanned vertical lines is always transmitted depending on NTSC or PAL standard used. However, several factors impede the ability to display them as transmitted:

• The camera electronics
• The transmission
• The reception and reproduction of the picture
• The storage and re-processing of the picture.

Any of these can result in distortion, “noise”, or loss of clarity. But in the world of analog that is just a matter of fact, similar to pre-cable days when TV viewers  had little choice but to live with  interference, ghost images, and other vagaries associated with rabbit ear or roof antennas.

 As cable did for television, digital transformed viewing capability in IP cameras.

§  In digital transmission the signal is converted to binary form. Each sequence of numbers represents the color or brightness of a frame. Throughout its transmission, the signal retains this information  and  when it arrives at its destination, the computer or server takes all those 1’s and 0’s and reassembles them  back to the original frame. Digital as a term refers to this use of numbers code

A digital signal knows what it should be when it reaches the end of transmission and can correct any transmission errors that may have occurred. This translates into clearer, distortion-free images. Another advantage is that digital technology takes up a lot less space than analog with the result that a lot more 1’s and 0’s can fit into the same file that analog would use.

Each frame equates to one digital picture file and the more 1’s and 0’s, in that frame, the more information contained. While analog cameras measure resolution in terms of lines, digital technology measures it in units called pixels. The more detail and clarity captured, the more pixels used. Cameras capable of capturing detailed images are called megapixel cameras.

As with analog, horizontal and vertical fields are captured and blended together to make a single frame. Here too, the resolution is expressed in a ratio. In ascending order of clarity, the standard resolutions are

·         VGA (640x480 pixels),

·         SVGA (800x600 pixels) and

·         XGA (1024 x 768 pixels).

Obviously, the more pixels it contains, the larger the file. And here we run into the need for compression, a nice tidy break point if ever there was one!

In a future post we will discuss pixels, megapixel cameras, what they are capable of capturing, how the information is stored, and how the necessary compression translates to frames per second.