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SUMMARYThe "shape-from-contour method" reconstructs the 3D shape of the surface of an object by extracting its contour from each of a series of successive images of the object. This can be realized by using a CCD camera, and is a relatively accurate method of obtaining environmental information. However, to obtain an accurate result, many images must be processed. Therefore, it is important to select the images depending on their effect on the final result, particularly for high-speed processing.This paper proposes an adaptive image selection (AISE) method which depends on the required accuracy. The method has been applied to objects having various cross-sectional shapes. The errors in shape reconstruction and the number of images required in the conventional method and the proposed method are compared. The experimental results show that the proposed method requires fewer images than the conventional method, particularly when the surface curvature of the object has large variation. The theoretical relationship between the accuracy of the reconstructed shape and the number of images required is also derived.

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SUMMARYIn the audiovisual handling of content coded by MPEG-2 transmitted over various kinds of networks such as the Internet or LAN, transformation of coding bit rates or transcoding is necessary. The simplest transcoding method is that of decoding MPEG-2 completely and then reencoding it at a lower bit rate. However, real-time processing of this method on a commonly used PC is difficult since the level of operations or the computational complexity for coding is high. However, if using the before-transformation coding information decreases the computational complexity, real-time transformation (transcoding) by software becomes possible. In this study, the Trampeg software transcoder (transcoder for MPEG-2) capable of real-time transcoding MPEG-2 with high quality has been developed. The applications, design guidelines, and processing algorithms of Trampeg are presented in this paper. The results of evaluation for operation of the system over a real PC have verified that an MPEG-2 system stream input via a network can be transcoded in real time and the transcoded low-rate stream can be transmitted directly to a streaming server.