The Journal of the Institute of Television Engineers of Japan

Image processing techniques have been applied for analyzing the reasons for collisions among skiers in a ski area. The skiers images used are taken from analog video tapes recorded at Takamagahara ski area in Nagano Prefecture. These images digitized in the size of 128 × 128 and quantized into 256 gray levels. Skiers images are extracted from images sampled every 1/6 seconds. The optimal threshold level for segmenting the skiers image is calculated using the step by step method. The projected future position of skiers is calculated from the relation between the past and present positions. Procedures for extracting skiers images are as follows : (1) Divide an image into meaningful regions. (2) Label the segmented regions. (3) Reject all regions except for skiers. (4) Calculate the skiers' center of gravity. (5) Find the locus of skiers' movement. (6) Detect skiers' collisions. By these procedures, good results for detecting skiers' collisions can be obtained.

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Field receiving tests for direct broadcasting satellites (DBS) are carried out with a car-mounted mobile receiving system. This system is developed for the first time. The tests are conducted on a car driven along expressways and ordinary roads in Tokyo and its surrourding suburbs. They proved by measuring receivable time duration rates from large amounts of data that the system receives DBS programs well while the car is being driven. The tests also show that frequent interruptions to the DBS wave by obstacles during car operation can, for the most part, be avoided with a space diversity reception method, using two or more systems together.

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In this paper a study on interpolation curves for displaying road networks is described. Several conditions of interpolation curves which are required to display road networks are introduced in chapter two. A Butland curve that can display road networks is described in chapter three. In chapter four, a method to select control points for curves already drawn is proposed, and the Butland curve is compared with straight line approximated curves, Lagrange curves and Spline curves. In chapter five, several experimental results show that a Butland curve is one of the best interpolation curves for displaying road networks.

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A new coding method called DANCE (DPCM Audio Near-Instantaneous Compressing and Expanding) is developed. It enables the transmission of four sound channels with MUSE system HDTV, of which the transmission capacity is smaller than that of the conventional Japanese satellite for TV broadcasting. Two different mode systems (mode A and mode B) are provided accoording to various types of programs. A quantized 15-bit signal is reduced to 8-bits in mode A, and a 16-bits signal to 11-bits in mode B. The sound quality of mode B is nearly equal to that of a Compact Disc's. After compressing the sound signal, independent data and error correction codes are added. The resulting sound transmission rate is 1.35 Mb/s. The serial sound bit stream is shuffled by a bit-interleaving technique to avoid the influence of burst errors. It is then converted to a ternary code. and time-compressed to multiplex into the vertical blanking period of a MUSE signal. Experimental transmission tests through a DBS, relay satellites, and CATV networks are conducted, and they show satisfactory performance.

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