| 摘要 |
<p>PURPOSE: To record/reproduce digital video information relating to an NTSC signal and to record/reproduce analog video information also by recording or reproducing digital video information for one frame per 2.5 rotation of a rotary drum by means of 1st and 2nd magnetic head pairs by rotating the drum at 2nd rotational speed corresponding to 1.25 times the 1st rotational speed. CONSTITUTION: When a 3rd control signal 8c is in an SP mose or an EP mode for recording/reproducing analog video information, a frame pulse(FP) is selected and outputted, and in the case of D1 to D3 modes for recording/reproducing digital video information, an output signal from a 1/4 frequency dividing circuit 141 is selected and outputted. An output signal from a switch circuit 142 is supplied to one input of a PLL circuit 143, its phase is compared with the phase of a drum pulse(DP) supplied to the other input and synchronized with the rotary drum so that the rotation of the drum corresponds to one period of the pulse DP and a drum driving signal 13a is generated so as to synchronize both the phases. A saw tooth wave signal is generated based upon the output signal of the circuit 142, sampled and held by the drum pulse DP and filtered through a loop filter. Consequently the rotational period of the rotary drum coincides with a frame period, and in the case of the D1 to D3 modes, the rotational period coincides with 1.25 times the frame period.</p> |
