Lucasfilm Ltd.

Curtis W Abbott

A method and system for recording and playing back from a bulk digital data storage medium having unequal access time, such as a rotating magnetic disk, data of a plurality of separate files, such as multi-channel sound information. Blocks of the digital data streams are stored in physically non-sequential scattered positions on a disk. The starting sectors of each recording track of the disk are not made the same but rather at least two different starting sectors are provided on alternating tracks in order to reduce the amount of access time between blocks of data. The blocks of data are read from the disk into a buffer memory in accordance with a disk read head scheduling technique that causes the next block of data with the shortest access time to be transferred unless there is an urgency to maintain balance in the various channels, in which case a block of data for the channel having the least buffered data is transferred next. This general criteria is altered under certain special circumstances, however, in order to take advantage of opportunities to read or write some other block of data without adding any access time, or to make sure that no channel runs out of buffered data. The technique allows the rate of data transfer to and from the disk to be maximized, considering the necessary limitation of buffer memory size and a desire in many cases to do transfers in real time, both reading and writing. The technique is especially advantageous when the data channels require editing by shifting their relative timing, often the case in multi-channel sound recording.

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San Rafael, CA, United States of America

Curtis W Abbott