The Truth about Fisheye

The Truth about Fisheye

Dewarping and how to use it

As most in the video surveillance industry know, traditional video surveillance cameras have an inherent flaw: blind spots. For example, if a fixed field-ofview camera is pointed left and an incident occurs on the right, then the camera is useless. So, couldn’t we just double or triple the number of cameras used in every cafeteria and parking lot in order to capture every angle? Sure, but then users are forced to incur extra hardware costs, installation costs, software licensing and added maintenance expenses.

With demand for comprehensive security increasing—while corresponding budgets decrease or stay the same—that is not a practical solution. This is why Sentry360 has made obtaining an affordable, true, 360-degree-view a technology that is accessible to the masses. Looking at a pure fisheye image might be a novel perspective, but when it comes to a security professional investigating, it becomes something to decipher. A 360° fisheye allows the curved fisheye affect to become corrected, like looking at a normal camera through a process called dewarping; however, this is only half the battle. Let’s put this into context relative to the current state of the market. 

The Market

There has been a big boom in the past few years with manufacturers producing cameras with fisheye lenses. The reality is that many of these products came to market to fill a gap in said manufacturer’s product-line, which often times is an imitation not an innovation. Many in the 360-degree sector believe that all they have to do to achieve full coverage is attach a fisheye lens to an IP video camera and—voila!—they will receive full coverage. Not so. If you don’t have the ability to first dewarp then allow full PTZ in live and recorded 360-degree fisheye images, then the result is a product that may be misleading to an end-user.

The majority of these recent entrants to the fisheye market do allow dewarping through a common DSP chip manufacturer Ambarella, but there’s a catch: The user must dewarp the stream incamera coming into the VMS which is typically 20 to 30 percent of the overall fisheye, leaving 70 to 80 percent unrecorded. To reduce blind spots, the user can repeat this process, adding multiple dewarped streams from the camera at different angles, but this could, in some cases, increase bandwidth and storage, or add software licenses and increase power consumption from the camera. Throughout this restricted process, it eliminates the ability to PTZ the dewarped single stream view in recorded video, which should ultimately be the sole purpose for choosing this breed of technology.

The following will help users understand best practices, positioning and applications for this technology with one common goal: to capture the largest amount of information with the least amount of cameras (sensors) from a single vantage point.

The Application: Ceiling Mount with 360° Technology

This is the North, South, East and West approach—with everything in between. 360°cameras are designed to capture a full half of circle and to be mounted on the ceiling looking straight down so it can capture, record and reproduce corrected perspective PTZ windows in recorded or live video. The optimization of the Sentry360 dewarping technology reduces the amount of total single field-of-view cameras you will need to cover heavy traffic or open areas within schools, banks, retail, assembly lines, busses, trains, airports and more.

The DOs:

  1. Mount in a ceiling using a surfacemount mini dome or flush-mount (discreet accessory) with a drop ceiling.
  2. Make a clear decision at what radius image quality is needed. Think detection vs. identification. Results will vary depending on how high the camera is mounted and how far away the subject is from the camera.
  3. Plan for evenly distributed lighting. If part of environment is poorly lit that section of the image will be affected.

The DON’Ts:

  1. Do not mount the 360°camera in a corner. This reduces its effective coverage. Ensure the camera is mounted in intersections or heavy traffic areas in open spaces.
  2. Because it’s a 5MP sensor, do not expect that a dewarped section will be that same resolution. A single dewarped view can be, depending on what native resolution of the camera, VGA or less, based on how much the user digitally zooms.

The Application: Wall Mount with 180°

This is taking the fisheye and wall mounting it for a desired 180° viewing angle (east to west). As opposed to stitching multiple sensors, for this application, the fisheye is displayed in one full panoramic view in your VMS of choice. Users can then digitally zoom into this view for a more detailed perspective. Because of the use of a fisheye and to minimize distortion, the best portions of the image are sectioned off for display, and eliminate the unimportant sections such as the sky, for example. The panoramic view is intended to be an overview shot and will provide users a camera reduction solution with a single installation point. Applications include sides of buildings and parking lots, retail checkout counters, stairwells, hallways (T intersections) and bus/train platforms.

The DOs:

  1. Ensure the 180 is mounted in the middle of the environment, centralizing its perspective view to evenly distribute  the image quality throughout the panoramic image.
  2. Make a clear decision on what mounting height as this effects the overall pixel density of the image. 
  3. For higher mounting, ensure that the 180 has the ability to point downward, either with the outdoor housing or mini-dome lens gimbal, as not to record unnecessary information such as clouds or the ceiling.

The DON’Ts:

  1. Do not mount the camera where large obstructions can cause blind-spots.
  2. Do not use this as a replacement for optically-zoomed PTZ for license plate capture. The 180-degree, panoramic view is designed to be an overview scene.

The Application: Table, Counter, Floor and Vehicle 360° Technology

This is using the 360° with a completely different algorithm that we’ve named “InVerted360°,” and could even call for applications users haven’t been thinking about.  When mounting the camera on a surface, table, counter or floor looking upward, the perspective changes. In a conference room, for example, you can navigate to the speaker or presenter and interact with others in the meeting room while being on a remote connection. In a retail or cash counting application by mounting or embedding the camera in the counter, users get a closer, more interactive perspective. It even has applications in gaming tables for blackjack or poker to have a table-level perspective of the full interaction between players and dealers.

To deliver the full functionality of 360° fisheye technology, Sentry360 has developed a software development kit (SDK) customized for VMS developers and NVR manufacturers. IP video surveillance has evolved into an ecosystem that allows the users to choose best-in-breed technologies to create a full, customized solution for the end-user, based on their application. Over the years, we were forced to adapt our SDK to work within a variety of different software environments, languages and operating systems.  To date, we feel that our SDK is the most integrated, flexible and customizable, enabling the future of this technology to not be limited. We boast that our SDK works with any operating system and software platform/language, and is ready to scale with any resolution as fisheye lenses improve and Ultra-HD becomes more common place.

The Sentry360 SDK has given security providers the tools necessary to record and display the full 360° fisheye image, and then in live or playback, correct the view for a full retrospective PTZ in all directions. The point of 360 is to enable that PTZ experience with the ability of hindsight in full 360 degrees, all while providing full situational awareness.

With nearly 30 technology integrations to date, Sentry360 has laid the ground work to optimize the future of this technology and has laid a path for future quality improvements for scaling in resolution and compression while opening the door to new applications.

This article originally appeared in the December 2014 issue of Security Today.

About the Author

Thomas Carnevale is the president of Sentry 360.

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