A floating address algorithm is proposed for reducing an average access time of an optical disk library required for exchanging the recording media. The exchanging method of this algorithm is simplified by group management of media access frequency. It is useful for image and video servers, whit the locality of access characteristics.

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In the compact-sized optical disc for video application, 135 minute or more recording time is required. However, current recording and coding techniques could not satisfying this purpose. On the other hand, variable bit rate coding gives ideal picture quality. We applied this scheme to the disc, and evaluated encoding, recording, playback and decoding. In this report, rate control method is discussed mainly. It gives constant visual quality and the data amount fitting in the disc capacity.

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RAID7^<TM> is a RAID (Redundant Arrays of Inexpensive Disks) system with characteristics all its own. Its characteristics is an "Asynchronous Data Transfer Architecture" which had been developed by Storage Computer Corporation in US at 1992. This paper describes that abstract regarding the RAID7^<TM>hardware & software architecture. The RAID7^<TM>may increase performance and decrease costs of storage device in VOD server system.

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New inter-track orthogonal coding for a high track density and multi-track recording is proposed. The new coding method is compared with a conventional NRZI by a computer simulation. The method is superior to the NRZI in terms of signal to noise ratio and bit error rate for white and jitter noises. Furthermore, the method can principally completely eliminate cross talks from adjacent tracks. An experimental result shows that it is possible to discriminate any track data from collectively read signals of multiple tracks. It is concluded that the new coding technique open the way to both high track density recording without guard-band nor azimuth and collective reading of multi-track channel signals.

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To analyze the coercivity reduction of very thin film longitudinal recording media, magnetic properties of CoCrTa/Cr thin films are studied at liquid helium temperature by SQUID susceptmeter. Following results are obtained, (1) media coercivity decreased by 30% for 80nm-magnetic layer and by 60% for 6nm-one because of thermal fluctuation. (2) crystallographic lattice disorders such as stacking fault exist in the initial layer of 10nm thickness. (3) Cr diffusion into the magnetic layer from the Cr-under layer is negligible. Reductions of crystallographic disorders as well as the reduction of the thermal fluctuation effect are needed to develop longitudinal recording media for high areal density recording.

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This paper describes a desirable nonlinear system, and the technical requirements and method of construction necessary to implement the nonlinear system in the news-center of a broadcasting station. Currently there is no standard for a digital compression recording system and the quality of picture for a nonlinear system. For broadcast use, there are still many issues to be solved including the development of large scale video server, a transmission system with little deterioration, a library system etc., Users and manufacturers must work together to design a nonlinear system for broadcast use.

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