Aligning windows of live video from an imprecise pan-tilt-zoom camera into a remote panoramic display for remote nature observation

Abstract

A pan-tilt-zoom (PTZ) robotic camera can provide a detailed live video of selected areas of interest within a large potential viewing field. The selective coverage is ideal for nature observation applications where power and bandwidth are often limited. To provide the spatial context for human observers, it is desirable to insert the live video into a large spherical panoramic display representing the entire viewing field. Accurate alignment of the video stream within the panoramic display is difficult due to imprecise pan-tilt values and rapid changes in camera configurations. Common image alignment algorithms are computationally expensive for real time applications. We are interested in designing algorithms that fit low power computation platform and hence can be implemented inside the PTZ camera in the future. We present a sampling-based constant-time image alignment algorithm based on spherical projection and projection-invariant selective sampling that accurately registers paired images at 100 frames per second on a simulated embedded platform. The alignment accuracy actually is better than existing methods when high rotational difference is involved. Experiments suggest that the new alignment algorithm is faster than existing algorithms by 1,471.6 times when aligning a six-mega-pixel image pair. © 2009 Springer-Verlag.