Image stabilizers: Utilizing DSP for more advanced, scalable stabilization algorithms

Yet some end users often swallow that cost simply because the alternative can be more expensive. For example, an intricate shot on a movie set could cost hundreds of thousands of dollars to recreate if the first take can't be used because it turned out to be too shaky.

Of course, not every end user can justify that expense. So what's needed is a solution that can scale from the low end to the high end, with no trade-offs along the way in terms of price and performance. That's a tall order, but meeting it creates a huge market opportunity. For example, besides applications such as broadcast, cinema and consumer cameras, the technology also could be used in verticals such as government and security.

To understand why it's such a challenge, consider the two fundamental variables. First, there are frequently multiple people in close proximity of each other in a single frame, so the system must be able to differentiate between each of them.

Second, there are often abrupt changes in luminance when the iris suddenly opens or closes while video is being recorded. These abrupt changes create what's known as "luminance imparity" between successive frames, which makes it complex to match frames. In low-light conditions, the limits of the field of view within a frame could change significantly due to a camera's auto-exposure feature. And if the application requires long-range zoom, that adds vibration and jerkiness, which means more work for the stabilizer.

The Level 1 (L1) metric -- which the industry uses for comparing frames -- also frequently introduces jerkiness or other anomalies, compounding the problem. And if the camera is handheld, airborne, mounted on a moving platform or mounted atop a tall building -- as many TV station "city cams" are -- there's even more jerkiness.

These environmentally induced anomalies are a major problem in one of today's fast-growing video applications: traffic cameras, deployed by municipalities and transportation departments to assist with traffic management. These cameras often are mounted on poles, so they're exposed to the wind, which causes vibration. Others are mounted on bridges, whose steel framework transfers the vibrations of passing vehicles to the cameras. Traffic cameras typically have zoom lenses, which compound the problem by turning even small vibrations into major jerks in the video. As a result, superior yet affordable image-stabilization features are a powerful market differentiator for camera vendors that target applications such as city cams and traffic cams. Figure 1 shows the improved image clarity that a stabilizer can provide in applications such as traffic cameras.


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Figure 1: Traffic camera without a stabilizer and with a stabilizer

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