Sometimes it doesn't take much to render an otherwise perfect video stream practically worthless. Gusts of wind tearing at a surveillance camera can make it shake or vibrate enough to make images come out as useless blur. A heavy truck, or a train, passing close by can have similar consequences. Most viewers will find it tiring and irritating to watch even a short video clip if it is constantly shaking or wobbling.
A number of different techniques have been developed to cope with the problem, with varying degrees of success. However, the introduction of efficient and affordable gyroscopes in combination with cutting-edge software programming has accelerated the process towards robust, real-time image stabilization.
Vibration impact on video output Improvements in video quality have, somewhat paradoxically, made the problem with blurry images more apparent. Increasing pixel density, higher resolution and more powerful zooms have not only made cameras more sensitive to vibrations but have simultaneously made viewers more susceptible and prone to noticing them.
Naturally, operators and integrators are aware of these challenges and are trying to address them. Vibration may, for instance, be reduced by choosing sturdier mounts or less exposed locations for the installation.
Image stabilization not only brings great improvements in the surveillance operator's working conditions by providing smooth, comfortable live viewing at all times, but also makes an entire video surveillance system more versatile and cost efficient by making better use of each camera's potential, for example by maintaining image quality in zoom shots when vibrations otherwise may have affected the video quality.
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At left: A snapshot from a video frame without Electronic Image Stabilization.
At right: Electronic Image Stabilization is activated. Above images demonstrate how Electronic Image Stabilization equalizes the motions from frame to frame resulting in stable motion video.
Benefits and applications in video surveillance
A surveillance camera mounted in an exposed location such as on a high pole or a street sign near a busy road, can be shaken by winds or passing traffic, which will blur the video. Electronic Image Stabilization works excellent regardless of camera lens type. When using a powerful telescopic zoom which zooms in on a distant object, the field of view becomes narrower and any shake or tremble will be amplified in the camera – and the amplitude of the shake will increase proportionally to the amount of zoom used. For a standard lens the challenges can be equivalent, if the camera is mounted in an environment with a high level of vibration. Regardless, image stabilization should be regarded as a prerequisite, so the cameras can be used optimally also in all kinds of circumstances.
Having cameras that are less sensitive to vibrations also makes installation more flexible and allows for multiple mounting options. In the prerequisite end, fewer cameras may be needed to satisfy surveillance requirements.
Further, stabilized images will save bandwidth use and storage space. Advanced video compression formats, such as H.264, are based on motion compensation. In short, this method uses the image of a single frame as a baseline and then only saves information about changes in the picture. A well stabilized image will contain comparatively less movement and thus require less bandwidth and storage.
For operators monitoring the video, Electronic Image Stabilization will make an important difference. Not only will the video material quality be improved, making it easier to see details and use the material to take action or make further analyses. It will also make the time in front of the monitoring screen more comfortable, eliminating fatiguing issues resulting from watching a blurry or vibrating video image.
Today, shakes and vibrations reflect on the results from most of the analytic applications available. However, using Electronic Image Stabilization could have positive effects. For instance, Video motion detection (VMD) is a way of defining activity in a scene by analyzing image data and differences in a series of images, a feature that can be built into a network video product or made available with video management software. Shakes and vibration increases the risk for false alarm, but can be amended by using Electronic Image Stabilization.
Finally, a perhaps less obvious advantage of image stabilization is that privacy masking can be made more precise. On a camera without any stabilization system, the effects of possible shakes and vibrations would have to be compensated by increasing the masked of area in the image.
Making efficient video stabilization affordable
Hardware and software development are making efficient video stabilization techniques affordable for an ever-increasing range of network cameras. This progress not only secures smooth, comfortable video monitoring in real time. It also enhances image usability, improves camera operability, makes installation more flexible and finally, improves the overall cost efficiency of a network camera surveillance system.