Abstract: A data stream is recorded and reproduced and a recording medium for the same are adapted to record in a control track an identification mark for identifying a specific track within a unit of plural tracks by superposing the identification mark upon a control pulse. A magnetic head travels along a predetermined path in the unit of plural tracks during a high-speed playback operation by phase-locking a rotational phase signal of a cylinder with a divided signal of the control pulse having a specific phase according to the reproduced identification mark.

Abstract: A predictor (20) and a learning device (20) are newly provided to a conventional speed controlling system for a rotating body, according to the present invention. The predictor predicts an instantaneous speed error on the basis of a plurality of speed errors to enable elimination of a phase delay due to sampling. The learning device is effective to remove torque ripple components of a motor on the basis of the speed errors. As a result, it is possible to expand a speed controlling region of the motor and to decrease irregularlity in rotation of the motor to a great extent. The predictor solely makes it possible to obtain a present accurate rate of change of data previously sampled from a plurality of sampled data, whereby a phase delay due to digital processes may be prevented.