JPH0220180A - magnetic recording and reproducing device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a magnetic recording and reproducing device for recording and reproducing video signals of the NTSC system, PAL system, etc.

(Prior Art) FIG. 2 is a block diagram of a reproducing system of a conventional magnetic recording/reproducing apparatus. A magnetic head 1 reproduces a modulated signal recorded on a magnetic tape and supplies it to a demodulation circuit 2 and a dropout detector 3. In demodulation circuit 2, limiter-1FM
Processing such as demodulation and de-emphasis is performed to obtain a reproduced video signal. On the other hand, in dropout detector 3,
Drop-out 1- detection is performed, and when a trop-out 1- occurs, a dropout pulse is output, and is supplied to the time axis correction circuit 4 in the memory block A together with the reproduced video signal output from the demodulation circuit 2. The dropout detector 3 outputs a ``high'' level signal when there is no dropout, and a downward pulse signal that is low level during the dropout period when a dropout occurs.

The time axis correction circuit 4 and dropout correction circuit 5 of the memory block A are of digital type.

The reproduced video signal and dropout pulse are generated by a write clock (
W-CK), write start pulse (W'-8TAR
T), and is written into the memory in the time axis correction circuit 4 under the control of the reproduction V pulse (PB-VP). The signals written to the memory are the read clock (R-CK) generated by the 5YNC & timing generation circuit 7, the read start path/L/S (R-9TART), and the base $V path/L/X (
R-VP), and a signal without time axis fluctuation is obtained. The time-base corrected signal is supplied to a dropout correction circuit 5, subjected to dropout correction, digital-to-analog converted (D/A), and supplied to a blanking circuit 8. The blanking circuit 8 performs blanking using the blanking signal from the 5YNC & timing generation circuit 7 so that the horizontal blanking period and the vertical blanking period conform to the video signal standard. A composite sync is added to the blanked reproduced video signal by a 5YNC adding circuit 9, and the reproduced video signal is outputted to an output terminal 10.

With the above-mentioned single circuit configuration, the height of the magnetic head is controlled using a piezoelectric element during variable-speed playback when the tape speed is 1/2 or 2 times, so that it is always on-track to the video track (dynamic tracking). Operation) A magnetic recording and reproducing device that obtains a reproduction screen without noise bars is known [Television Society Technical Report 9, No. 14.
VR70-2, p, 7 (1985)).

Figure 3 is a diagram explaining the tracing of the magnetic head during double speed playback, where a is the magnetic tape, b and c are the video tracks traced during normal speed playback, and b is the first track attached every 180 degrees. ．． The first of the second magnetic heads
In the magnetic head shown in FIG. 1, C is the trace by the second magnetic head, and the broken line section d is the trace by the first magnetic head when the height of the magnetic head is not controlled.

During double-speed playback, the height of the first magnetic head is controlled so that it tracks onto video track b from the trace position indicated by the broken line d, but not all of the signals recorded on video track b are played back. The time required to trace the broken line part d, that is, on the track b, the point e
At this point, head switching is performed on the second magnetic head. This means that the signal from point e to the top of track b is not reproduced. The signal missing period (unreproduced period) is α (the number of offset lines between adjacent tracks). Note that signal loss occurs when the tape speed is faster than the normal speed. The missing portion of the signal cannot be detected by the Drosopau 1 to the detector 3.

(Problem to be Solved by the Invention) However, in the circuit configuration shown in FIG. 1, when the tape speed is faster than the normal speed, the first magnetic head
Since the video signal for one field is not reproduced and the head is switched to the second magnetic head with the signal missing, the reproduced video signal output to the output terminal is not reproduced at the end of the first field. has the problem that the signal of the second field is mixed with the signal of the first field at the end of the second field and reproduced.

Furthermore, the larger α8 is, the more video signals are mixed.

In view of the above, the present invention has been developed so that even when performing a dynamic 1-racking operation at a tape speed higher than the normal speed, each field of the output reproduced video signal is not mixed with video signals of other fields. An object of the present invention is to provide a magnetic recording/reproducing device for reproduction.

(Means for Solving the Problems) The present invention provides means for generating a signal indicating a missing period of a video signal caused by head switching during a dynamic tracking operation when the tape speed is higher than the normal speed, and a signal indicating the missing period. Means for adding a signal to a dropout pulse is provided, and the dropout period of the video signal is supplied to the memory as dropout information to perform dropout correction.

(Function) According to the present invention, with the above-described configuration, the dropout period of the video signal caused by head switching during the dynamic tracking operation is supplied to the memory as dropout information, so that the dropout is corrected in the memory section. Therefore, even if the number of signal lines reproduced by one magnetic head is less than the number of lines for one field, the video signal of the same field is corrected in the memory section, so the video signal between each field can be corrected. There is no contamination.

(Embodiment) FIG. 1 shows a block diagram of a magnetic recording/reproducing apparatus according to an embodiment of the present invention. In Figure 1, 11
12 is an input terminal for a head switching signal; 12 is a dropout period signal generator that generates a signal at a high level during a signal dropout period caused by head switching during dynamic tracking operation; 14 is a Nant gate, 15 is an AND gate, and the same numbers are given to those that operate in the same way as the conventional example. The operation will be explained. Fig. 4 is a waveform diagram for explaining the embodiment, in which f is a head switching signal and g is a signal indicating a signal drop period.

The missing period signal generation circuit 12 receives the head switching signal from the terminal 11 (FIG. 4f) and the reproduced 2F signal (PB 2
．． fm: pulse signal with twice the horizontal frequency), from the edge of the head switching signal to PB 2f
, l signals to form a pulse signal having a width of approximately α8. The pulse signal is a signal indicating a missing period of the video signal, and is a waveform diagram shown in FIG. 4K. The signal indicating the missing period of the video signal is supplied to the NAND gate 14, performs NAND with the signal from the terminal 13 that becomes "high" level during dynamic tracking during variable speed reproduction, and is supplied to the NAND gate 1-15. . A dropout signal from the dropout detector 3 is supplied to one terminal of the AND gate 15, and the output signal of the AND gate 1-15 is added to the dropout signal during dynamic tracking operation during variable speed playback. A signal indicating the signal loss period is added and output. At normal speed, only the signal is output to drop controller 1, and memory block A
The signal is supplied to the time axis correction circuit 4 inside. Memory block A
The demodulated video signal from the demodulation circuit 2 supplied to the field is corrected for dropout by the output signal from the AND gate 15, and during the period when the video signal is missing, it is corrected by the video signal of the same field. This eliminates the mixing of video signals.

The other circuit portions operate in the same manner as in the conventional example, so explanations will be omitted.

As described above, according to this embodiment, the missing period signal generation circuit is provided, and the head switching signal and P B -25
A signal indicating a missing period of the video signal having a pulse width of approximately α8 minutes from the point where the head switch is performed is generated with the u signal, and the signal indicating the missing period is dropped when dynamic tracking is performed during variable speed playback. By adding it to the signal and supplying it to the memory, the missing part of the video signal that occurs due to head switching is corrected by the video signal of the same field.

In this embodiment, a signal having a pulse width of approximately The rising edge of the vertical synchronizing signal is detected and the rising edge of the vertical sync signal is detected from the point where head switching occurs.
A signal in which L remains at the "high" level during the period up to the edge may be output as a signal indicating the missing period of the video signal.

(Effects of the Invention) As explained above, according to the present invention, during the dynamic tracking operation of variable speed playback, the missing period of the video signal caused by head switching is corrected by the video signal of the same field, and the video signal of the other field is compensated for by the video signal of the same field. Contamination is eliminated, and the practical effect is great.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of a magnetic recording/reproducing apparatus according to an embodiment of the present invention, Fig. 2 is a block diagram of a conventional magnetic recording/reproducing apparatus, and Fig. 3 is a trace of a magnetic head during double speed reproduction. The operation diagram to be described, FIG. 4, is a waveform diagram to explain the embodiment. l2 Missing period signal generation circuit. Nant Gate, Ant Game-1-0

Claims (1)

[Claims] When the tape speed is at a speed other than the normal speed, the height of the magnetic head is controlled to keep it on track with the video track to obtain a reproduced video signal without noise bars. Means for generating a signal indicating a period of missing video signal caused by head switching during playback, and means for adding the signal indicating the missing period to a dropout pulse are provided, and the missing period of the video signal is supplied to the memory as dropout information. A magnetic recording and reproducing device characterized in that it performs dropout correction.