Canonical Patch Research Articles

Interframe coding of feature descriptors for mobile augmented reality.

Streaming mobile augmented reality applications require both real-time recognition and tracking of objects of interest in a video sequence. Typically, local features are calculated from the gradients of a canonical patch around a keypoint in individual video frames. In this paper, we propose a temporally coherent keypoint detector and design efficient interframe predictive coding techniques for canonical patches, feature descriptors, and keypoint locations. In the proposed system, we strive to transmit each patch or its equivalent feature descriptor with as few bits as possible by modifying a previously transmitted patch or descriptor. Our solution enables server-based mobile augmented reality where a continuous stream of salient information, sufficient for image-based retrieval, and object localization, is sent at a bit-rate that is practical for today's wireless links and less than one-tenth of the bit-rate needed to stream the compressed video to the server.

INTERFRAME CODING OF CANONICAL PATCHES FOR LOW BIT-RATE MOBILE AUGMENTED REALITY

Local features are widely used for content-based image retrieval and augmented reality applications. Typically, feature descriptors are calculated from the gradients of a canonical patch around a repeatable keypoint in the image. In this paper, we propose a temporally coherent keypoint detector and design efficient interframe predictive coding techniques for canonical patches and keypoint locations. In the proposed system, we strive to transmit each patch with as few bits as possible by simply modifying a previously transmitted patch. This enables server-based mobile augmented reality where a continuous stream of salient information, sufficient for image-based retrieval and localization, can be sent over a wireless link at a low bit-rate. Experimental results show that our technique achieves a similar image matching performance at 1/15 of the bit-rate when compared to detecting keypoints independently frame-by-frame and allows performing streaming mobile augmented reality at low bit-rates of about 20–50 kbps, practical for today's wireless links.

A Generalized Edge Boundary Condition for Open Microstrip Structures

A generalized edge boundary condition (GEBC) relating the tangential magnetic field and the vertical electric field at the edge of an arbitrarily shaped microstrip patch on electrically thin substrate is developed. This boundary condition incorporates dynamical edge effects and coupling over the patch. Based on this boundary condition, commonly used microstrip patches can be accurately and efficiently analyzed. A perturbation approach yields simple expressions for the resonant frequencies and Q -factors of canonical patch shapes. Rectangular and circular microstrip patches are analyzed in detail and calculated results are compared with previously published theoretical and experimental results.