Megapixel

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July 20, 2010

Simplifying Video Coverage

Posted by Doug Marman under Cameras, Megapixel, PTZ cameras, Video analytics
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Technology can make our lives a lot easier and a lot more complex at the same time.

For example, we never had to worry in the past about how much coverage we could get from a camera. No one used to mention pixels-per-foot (or per meter) ten years ago. Why? Because when we wanted to see up close, we used PTZ (pan-tilt-zoom) cameras to zoom right in on the person’s face or their license plate. With 20X zoom, you had all the detail you needed.

But PTZ cameras need someone driving them to get those close-ups. Megapixel cameras offer the ability to have a fixed camera that can record enough detail. You can zoom in later, or in real time, without moving the camera.

In many cases, that is a lot better. Unfortunately, there just aren’t enough pixels to do all the zooming we do with a PTZ camera. You need 400-600 million pixels to get the same 360 degrees of coverage with 20X zoom that you get with a PTZ camera. That’s 100X more than even the large 5 megapixel cameras sold today.

So, we need to figure out how much coverage we can get with megapixel cameras. Life just got more complex.

John Honovich provided a great service to integrators with the testing he did to show how many pixels per foot you need to get good detection. See his article here:

http://ipvideomarket.info/report/pixels_surveillance_video_test

However, as he points out, you can’t reduce it down to one single number. It depends on many factors.

But here are a few rules to make this simpler.

First, remember this important fact: There is a big difference between general surveillance and trying to recognize a person’s face or their license plate.

Facial and license plate recognition require about 10X – 20X as many pixels per foot, and you need special lighting, plus a number of other factors to keep in mind. Studies have shown that even close up pictures of someone who has changed their hair color or beard is hard to confirm for certain. But it requires less resolution to recognize someone you know. This makes recognition m0re difficult to design for, especially if you want to use the evidence in court cases where jurors never know the people in the videos.

General surveillance, however, where you are only trying to detect if people are in the area, or how many people there are, is much simpler. John’s study shows that 5-12 pixels per foot should be enough. Our testing at VideoIQ shows that our video analytics match this number, which means that our analytics are just about the same in their ability to recognize people in an area as people watching a monitor.

Actually, our analytics might be slightly better, since we recommend that 5-8 pixels per foot for most conditions. This means that if people are too small to see, or the lighting is too dim to see them on a monitor, then video analytics are probably not going to accurately detect them either.

Not all analytics technologies are this accurate. Some require more resolution. More importantly most analytics systems don’t analyze all the pixels. You will find that systems generally scale the video resolution down to minimize processing power for analytics, so be sure to check the actual resolution they are analyzing.

A good second rule of thumb here is: Good video analytics require about the same pixels per foot for accurate detection as humans watching a monitor.

To make life simpler, also remember this: Horizontal pixels determine coverage.

This means that knowing how many pixels are on the horizontal axis, and knowing the pixels per foot for good detection, you can calculate the coverage of a camera. This simplifies estimates. Below are some standard resolutions calculated, based on 5-8 pixels per foot for general surveillance:

CIF (357 horizontal pixels) . . . . . . . . . . . . 45 – 70 feet of coverage

D1 or 4CIF (704 horizontal pixels)  . . . . . 90 – 140 feet of coverage

1.2 MP (1,280 horizontal pixels) . . . . . . . 160 – 250 feet of coverage

1080p (1,920 horizontal pixels) . . . . . . . 240 – 380 feet of coverage

3.1 MP (2,048 horizontal pixels) . . . . . . . 250 – 400 feet of coverage

5 MP (2,592 horizontal pixels) . . . . . . . .  320 – 510 feel of coverage

What is surprising is that the above numbers are true no matter what focal length lens you use!

A 3 mm lens will give you good detection up to about 100 feet away, while a 10 mm lens will work to around 300 feet (for a D1 resolution camera), but in both cases you still have the same horizontal coverage. So, you can copy the above numbers and use them for your planning estimates.

A couple things to keep in mind:

  1. Interlaced video reduces horizontal resolution. The latest studies I have seen suggest a 25% reduction in horizontal resolution. So, be sure to reduce coverage numbers when cameras are using interlaced video (1080i means it is interlaced, while 1080p is progressive, and almost all analog cameras use interlaced video).
  2. You need lenses with the capability of capturing the full resolution of the imager, or you aren’t going to get the full horizontal coverage. This, unfortunately, is a common problem with many megapixel cameras shipping today.

A few interesting observations emerge from the above chart:

  • Even though a 1080p camera only has 2.1 megapixels, it has virtually the same horizontal coverage as a 3.1 MP camera. That’s because of the 16:9 aspect ratio of HD video.
  • A 1080p camera has almost 3X as much coverage as a standard resolution camera (D1 or VGA), but a 5 MP camera only has about 30% more coverage than a 1080p (and you will only get 30% added coverage if you have a true, high quality, 5 MP lens).

You can see why 1080p looks like the resolution that the industry seems to be moving towards.

Even though there seem to be  way too many resolutions of megapixel cameras to choose from, and way too many numbers to keep in mind, things are getting simpler.

 

May 17, 2010

As the PTZ Camera Turns

Posted by Doug Marman under Cameras, Megapixel, PTZ cameras, Remote Monitoring, Video analytics, VideoIQ
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The world of pan, tilt, zoom security cameras has changed. Megapixel cameras and video analytics are shifting the role of PTZs.

PTZ cameras were once king of the hill. They represented the best possible technology you could get; giving you the ability to see in every direction  and zoom into the smallest details.

Companies like Pelco, Vicon and Kalatel, to name a few, started their businesses by producing high quality pan, tilt, zoom cameras. They rode the wave, as PTZs defined video surveillance, and grew into leading video companies.

But the problem is that all the power and benefits PTZs deliver are only gained when a person is sitting there actively panning, tilting and zooming. With only a few percent of cameras being actively monitored, and only a few percent of those being watched at one time, there is no one at the helm more than 99% of the time.

The other disadvantage of PTZs is that the moment you’ve zoomed in to see a license plate or to get a close-up of a person’s face, you lose the ability to see everything else. You can easily miss something more important.

If you want to look across a site, PTZs are valuable tools. But if they are sitting there, not being actively driven most of the time, they are expensive cameras. That’s why many PTZs are set for continuous tours, where they move from one preset location to another, auto-panning. This also partly overcomes the problem with missing things when it is zoomed into one area. They move from one point to another to cover a wider area. This allows one expensive camera to cover the whole area. That’s the hope, anyway.

However, belts, gears and motors don’t last long when the PTZ is set for continuous tours. The best quality models need replacement parts every year, when set for auto-panning. Cheaper model PTZs wear out even faster. When that one expensive camera fails at the site, you’ve now got nothing.

Megapixel cameras have taken a big chunk out of the once powerful PTZ. No motors, belts or gears to wear out. Even when you zoom in, you can still keep on recording the whole scene, so you won’t miss anything. This is ideal for recorded video. Megapixel cameras don’t give you anywhere near the full zoom capability of PTZs. You are limited to about 3X-8X for a megapixel zoom, not the 20x-30x you get with a PTZ, but in many cases that’s fine.  And, you can buy two megapixel cameras for the price of one PTZ.

Video analytics are also changing the world of PTZs. The applications where PTZs are most important – were live monitoring is needed – that’s exactly where video analytics provide the biggest bang. They enable security personnel to monitor far more cameras much more effectively, by proactively popping up cameras when the analytics see potential threats.

Why not use video analytics with PTZ cameras? You can, and we sell such systems all the time. But if you want to be sure you are going to catch an intruder, you can’t have that PTZ panning all over the place. Fixed cameras are the only way to assure you never miss a threat.

For example, let’s say you have a site where you want one PTZ camera to auto-tour across four different preset locations. The PTZ would move to one preset, watch for some time and then move on to the next. How much time will the camera spend watching any one area? Less than 25% of the time! That means more than 75% of the time you have no visibility on what is happening. With more than four presets, it is even worse. That’s a huge blind spot in your protection!

The alternative: You can put up 3-4 cameras with video analytics built-in for about the same cost as a PTZ camera with analytics, and you won’t have yearly replacement costs for the motors, belts and gears. Most importantly, the analytics won’t miss what is happening – so you get much better security. In fact, it is the only way to go, when you need surefire protection.

In other words, fixed, non-moving cameras with analytics now give the best site awareness. With active video analysis doing the watching for you, it is better to have more fixed smart cameras than a panning PTZ.

So, the new king of the hill is a megapixel camera with analytics built-in. This gives you zoom, a wide area of coverage that is never missed, and analytics to detect potential threats so that you know which camera to be looking at.

Even better, add a PTZ camera at the site if you want the ability to zoom in for a close-up. That’s where the PTZ excels. It’s a tool for extreme close-ups. This combination system has persistent protection because the megapixel cameras continue watching the areas they are trying to protect. They never look the wrong direction. Plus, the analytics watch for threats continuously, even when no one is watching the monitors.

The PTZ will be around for a long time and still plays an important role in surveillance. However, it is not quite as important as it once was. It once was king. Now it is a good soldier. The world has changed for PTZs.

 

April 2, 2010

True Megapixel Analytics Have Arrived

Posted by Doug Marman under Cameras, Edge Storage, Megapixel, Video analytics, Video storage, VideoIQ
[17] Comments 

We put on the first demonstration of true megapixel analytics in the industry at our ISC West booth last week.

It was eye-catching. Lots of people stood there staring at the analytics detecting people, cars, trucks, motorcycles, sailboats, speedboats, etc. Here’s a picture:

Unfortunately, this blog can’t show the full resolution or video, which you really need to see to appreciate how incredible it looks.

When I say this is the first public display of “true megapixel analytics” I mean the resolution being analyzed is megapixel. There have been cameras with megapixel video that have had analytics processing before. CoVi is a good example, may they rest in peace. They sold a 1 MP camera that ran ObjectVideo analytics. However, the resolution of the analytics was only CIF (320 x 240 pixels), which gave hardly any detection range. It was silly to put CIF analytics on a megapixel camera.

Why hasn’t anyone ever demonstrated megapixel analytics before? Because of the sheer processing power that other technologies need to do this.

VideoIQ’s technology is different. We need about 1/8th the amount of processing power compared to other high quality analytics systems. So, we can run the whole thing in one of the popular low cost DSP processors. But all other analytics technologies need a lot more horsepower.

For example, ObjectVideo on their web site claims they can run up to 4CIF resolution video in the same DSP chip we are using. However, in most cases the users of OV onboard are only running CIF resolution, because there are serious limitations running 4CIF, such as only being able to have one rule running at a time and a limited number of objects that can be detected.

IOimage uses two DSP processors in their cameras to get high quality and avoid compromising detection.

The camera we demonstrated was a 1080p camera, which is 1920 x 1080 pixels. We demonstrated it live at the show, with the analytics all running in the camera. It provides 3X the horizontal coverage of a standard resolution camera, and more than 2X the anaytics detection distance.

For other technologies to run 1080p analytics, they would need more than 6 times as much processing power, compared to 4CIF video. That would mean 6 DSP chips, or some very expensive high end DSP chips.

If you try to run this on a server or a PC, you would need a full dual core processor to run one camera. So, you can see why it’s never been shown before. It is impractical for other technologies.

The other industry first we showed is something we call IQTrack. It uses the video analytics to automatically track and zoom on objects in the field of view. Here’s a picture:

This is different from PTZ camera tracking. If you look at the lower left of the picture, you will see that the whole field of view is still being recorded and it shows where in the scene you are zoomed into. So, you can always go back later and pick another part of the video to look into.

The other unique thing is, if many people are in the area, you can click on one person and it will zoom in on and track just that one person. That’s never been shown before either.

Watching it, you can immediately see that there is no comparison between watching video that is automatically zooming and tracking on important objects, versus static video cameras. It pulls your eyes to exactly what is important. I think this is going to be very popular for megapixel cameras.

The 1080p cameras we sold will also be the first cameras to ship with a new imager from Sony that has some amazing low light performance. We are still testing it, but it looks to be 2X-4X better than any other multi-megapixel imagers used in the security industry.

And of course, the camera we showed included a hard drive so that you can store 1-2 months of high quality 1080p video. This solves the bandwidth problem for megapixel cameras, since it needs no bandwidth to record, and eliminates the need for external storage in most cases.

Now that true megapixel analytics have arrived, I think it is going to set the standard, and I think it offers incredible visual value to megapixel cameras, even if you don’t want the analytics for detecting alarms.

 

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