公开(公告)号：CA2138301C

公开(公告)日：1998-12-15

申请号：CA2138301

申请日：1994-12-15

Applicant: IBM

Inventor： OTTESEN HAL HJALMAR ,  CUNNINGHAM EARL A ,  GREENBERG RICHARD ,  BROWN DANA HENRY ,  SMITH GORDON JAMES ,  VANLEEUWEN GEORGE WILLARD ,  BILLINGS RUSSELL ALLEN

IPC: G11B5/012 ,  G11B5/55 ,  G11B5/596 ,  G11B7/0037 ,  G11B19/20 ,  G11B19/247 ,  G11B20/12 ,  G11B21/00 ,  G11B21/02 ,  G11B21/04 ,  G11B27/00 ,  G11B27/10 ,  H04N7/173

Abstract: A disk drive stores multimedia data in long spiral data tracks. The tracks on opposite surfaces of the disk spiral in opposite directions, so that a track on one surface can be read as the actuator sweeps in, and a track on the opposite surfa ce can be read as the actuator sweeps out. Because the actuator only follows spiral tracks without performing long seek operations, the actuator motor can be reduce d in size and stresses on actuator bearings and other parts are reduced. Additiona lly, due to reduced disturbances associated with seeks, it is possible to follow trac ks more closely and therefore reduce the width of individual tracks. Further cost reductions are accomplished by spinning the disks at a slower speed and reducing the size of the spin motor accordingly. Finally, data density can be increased s imply because multimedia data does not require the same low error rate as conventional data. Preferably, a group of disk drives optimized for multimedia data is used t o form a video-on-demand system. Compressed, interleaved portions of a video presentation, such as a motion picture, are stored in blocks on the spiral track s. The drives read the blocks on one spiral track at a time from beginning to end, placing the data from these blocks in a set of buffers corresponding to differen t short time intervals. Video signals are output from the buffers. Any short time interval of the presentation can be accessed on demand by switching to the appropriate buffer.