JPS5952593B2 - magnetic recording and playback method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic recording and reproducing method for sequentially recording and reproducing one field of video signals as a recording locus inclined with respect to the longitudinal direction of a magnetic tape using a rotating magnetic head.

FIG. 1 shows a recording tape recorded at normal speed.

1 is an audio track, 2 is a video track, and 3 is a control track.

Also, one video track usually has one field (
Although 262.5H) minutes are recorded, it is expressed as 7H for ease of explanation and understanding. As shown in FIG. 1, the horizontal synchronizing signals recorded at the position corresponding to ■I are aligned perpendicularly to video track 2, and the video head passes through different tracks during playback. In this case, H cracking can be prevented because the continuity of the horizontal synchronization signal is maintained, but since the horizontal synchronization signals of adjacent units are different from each other, the reproduced image is misaligned. In Figure 1, the IH is shifted, but l
/2 inch EiAJ standard, there is a shift of 4H. Therefore, if the recorded tape shown in Figure 1 is played back at normal speed, the video head will accurately trace the video track 2, and as shown in Figure 2 (4 is the image area, 5 is the vertical synchronization signal area).
A complete signal of 7H as shown in Figure 1 can be obtained, but if played back at low speed, one field will only contain 6H in any case of A, B, C, or D in Figure 1 <(EiAJ
In the case of 4H disappears), the IH signal disappears. Therefore, at low speeds, the video head moves to A and B in Figure 1.
, C, and D, the reproduced image differs from that in FIG. 2 and changes as shown in A, B, C, and D in FIG. 3.
That is, when the video head passes through the middle of two adjacent tracks, a bead or noise occurs, and the vertical phase of the image differs on both sides of the bead (or noise).
Also, when changing from C to D (when the video track on which the vertical synchronization signal is played back changes), the phase of the vertical synchronization signal shifts, so even if a still image is recorded, the playback image will not match the video head. As the video track is moved, the reproduced picture fluctuates in the vertical direction.<0 The present invention seeks to provide a reproduction method in which this "fluttering" is reduced.

Hereinafter, the present invention will be explained based on FIGS. 4 and 5.

In FIG. 4, 6 is a flip-flop that is triggered by the output detected by the rotation of the video rotating head, and the output {Figure 5} and the reproduced video signal {Figure 5} are connected.
Figure A} has a phase relationship as shown in Figure 5. Further, the output port of the flip-flop 6 has a waveform as shown in FIG. On the other hand, demodulation circuit 12
Video track noise of the video output demodulated by {
N1 to N5} in FIG.
1 is reset triggered. Therefore, the output of the flip-flop 11 is as shown in FIG. Furthermore, the output H of the flip-flop 1 and the output H of the differentiating circuit 7 are ANDed by the AND circuit 1.
5, the output shown in FIG. 5 is obtained, and the AND
The charging/discharging circuit 16 is operated by the output of the circuit 15, and the fifth
The output shown in the figure is obtained, and the delay amount of the mono multivibrator 17 is modulated by the output. In the fourth configuration example, the delay amount of the mono-multivibrator 17 is normally about 1.
vertical period (16.6 ms), and the delay amount becomes shorter if output t is applied, so mono multivibrator 1
7 delayed edges are shaped by the waveform shaping circuit 18. That is, the output of the waveform shaping circuit 18 undergoes phase modulation when the video inter-track noise N crosses the vertical synchronizing signal (N3→N4). Therefore, by mixing the output A of the waveform shaping circuit 18 with the video output A in the mixing circuit 19, vertical synchronization of the monitor television is achieved as shown in FIG. Therefore, the "fluttering" in the vertical direction of the reproduced picture shown in FIG. 3 can be reduced by phase modulating the vertical synchronizing signal as shown in FIG. When playing back a video magnetic tape recorded in modulates the phase of the reproduced vertical synchronization signal,
It is possible to suppress the flapping that occurs on the screen.

[Brief explanation of the drawing]

Figure 1 is a diagram of a recording tape to explain the disadvantages of the conventional method.
2 and 3 are explanatory diagrams for explaining the above-mentioned disadvantages, and FIG. 4 is a block diagram showing an embodiment of the method of the present invention.
FIG. 5 is an output signal waveform diagram of each part in FIG. 4. 6, 11...flip flop, 7, 8...
...Differential circuit, 9,10...Diode, 1
2... Demodulation circuit, 13... Noise detector, 14... Pulse amplifier, 15...
AND circuit, 16...Charging/discharging circuit, 17...
... Mono multivibrator, 18 ... Waveform shaping circuit, 19 ... Mixing circuit.

Claims (1)

[Claims] 1 A magnetic recording and reproducing method in which a rotating magnetic head sequentially records and reproduces one field of video signals as a recording trajectory inclined with respect to the longitudinal direction of the magnetic tape, in which video magnetic tape recorded at normal tape speed is Modulates the phase of the playback vertical synchronization signal depending on the relative position of the noise signal generated when the rotating video head passes between adjacent video tracks and the vertical synchronization signal of the playback video signal when playing back at a tape speed different from the tape speed. A magnetic recording and reproducing method characterized by reducing and eliminating sudden changes in vertical synchronization signals.