| 摘要 |
PURPOSE:To obtain a fine reproduced picture by a magnetic recording and reproducing device that provides variable-speed reproduction, by generating a false synchronizing signal by generating pulses of fixed width at a point of time of head start or at a point of time delayed by a fixed phase. CONSTITUTION:The phase of a false synchronizing signal to be added in variable- speed reproduction depends upon the value and increase or decrease direction of the envelope of a frequency-modulated reproduced signal. When the ratio of the value of the envelope at the head start point to its maximum is denoted as (k) (0<=k<=1) and the slanting H shift between adjacent tracks is denoted as alphaH, the phase of false synchronizing signal (e) based upon the point fixed-phase behind the head start should be set to (1-K)alphaH. Then, pulses (e) are generated in anticipation of a shift in vertical synchronizing signal between the head start and tracks, so that a flicker of a screen can be prevented. |
