PTZ Camera Window Blanking via Coordinate Mapping
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Solution Overview
Problem
Current surveillance PTZ camera systems fail to maintain privacy masks effectively when the camera's position changes, as traditional systems only redraw the mask when the camera becomes stationary, and are limited in handling multiple private areas and shapes.
Innovation Solution
A window-blanking feature that maps pixels on the image plane to a world coordinate system, allowing for accurate blocking of designated private areas during camera movements by pre-computing and storing conversion look-up tables, and supporting multiple polygon shapes through interpolation, enabling continuous privacy zone maintenance regardless of camera state changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional systems only redraw the privacy mask when the camera becomes stationary, then the system complexity is reduced, but the privacy protection reliability deteriorates as private areas are revealed during camera movement
Solution Approach 1:
The system pre-computes and stores conversion look-up tables mapping pixel coordinates to world coordinates and vice versa. This preliminary preparation enables real-time privacy zone tracking during camera movements without complex runtime calculations, resolving the contradiction between reliability and complexity
Solution Approach 2:
The patent replaces traditional mechanical/redrawing-based privacy mask updates with a computational approach using pre-computed look-up tables and coordinate transformations. This substitution enables continuous privacy protection during PTZ movements while maintaining system efficiency
2Manufacturing precision
If the system uses pre-computed look-up tables for coordinate mapping, then the manufacturing precision of privacy zone masking is improved, but the device complexity increases due to additional computation and storage requirements
Solution Approach 1:
The system pre-computes conversion look-up tables during system initialization or setup phases, storing coordinate mappings that enable precise privacy zone positioning during actual operation. This separates the complex computation from real-time operation, achieving precision without runtime complexity
Solution Approach 2:
The patent creates a virtual copy of the world coordinate system mapped to the image coordinate system through look-up tables. This virtual mapping enables precise privacy zone definition in world coordinates while the actual masking operates on image coordinates, decoupling precision requirements from processing complexity
3Adaptability or versatility
If traditional systems are limited to fewer than eight rectangular privacy areas, then the device complexity is reduced, but the adaptability deteriorates as the system cannot handle multiple polygon shapes and areas
Solution Approach 1:
The system divides complex polygonal privacy zones into manageable vertex-based definitions, where each privacy area is specified by a sequence of vertex coordinates. This segmentation enables arbitrary polygon shapes while maintaining computational tractability through vertex-by-vertex processing
Solution Approach 2:
The patent creates a universal privacy zone definition system that handles both rectangular and polygonal shapes through a single vertex-based interface. The same coordinate mapping and look-up table mechanisms that work for simple rectangles also handle complex polygons, achieving versatility without proportionally increasing complexity
Data Source
AI summary
Network cameras employing advanced video analytics are increasingly being used in both public and private settings. Unlike fixed surveillance cameras, pan/tilt/zoom cameras provide a dynamic field-of-view. Some regions within a given field-of-view can be designated as private and may not be recorded. A window-blanking feature, according to an embodiment of the invention, enables an ability to block out defined portions of the video where a privacy zone may otherwise appear. Through use of the embodiment, consistent privacy is provided during dynamic surveillance to ensure compliance with privacy regulations or contractual arrangements relating to use of a surveillance camera having a privacy zone within the given field-of-view.