JPH0523028Y2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to a magnetic reproducing device, which switches and extracts a reproduction signal with a high reproduction level among the reproduction signals of adjacent magnetic heads having mutually opposite azimuths.
The present invention relates to a magnetic reproduction device suitable for obtaining reproduced images without noise bars.

Prior Art The present applicant previously proposed a device which prevents the generation of noise bars and head switching noise even during special playback in Japanese Patent Application No. 58-87363 entitled ``Magnetic Playback Device''.

The magnetic reproducing apparatus described above has two sets of magnetic heads 2a, 2b and 3a, 3b provided at rotation angle positions of 180 degrees on the circumference of a rotary drum 1 shown in FIG. 2A. As shown in B and C of the same figure, magnetic heads 2a and 2
b is a wide head for normal video recording and reproduction, and has opposite azimuths to each other, and magnetic heads 3a and 3b
are narrow widths for recording and reproducing video over long periods of time, and have opposite azimuths to each other. Further, the adjacent magnetic heads 2a and 3a, 2b and 3b are spaced apart by a distance corresponding to, for example, 1H, and have opposite azimuths.

Reproduction signals of the magnetic heads 2a, 2b, 3a, 3b are transmitted to terminals 5a, 5b, 6a, 6b shown in the third figure.
preamplifiers 7a, 7b, 8a,
After being amplified by each of the switches 8b, the signals are supplied to the switches 9 and 10, respectively. Switches 9 and 10 select terminal a during, for example, a high level period of the head switching pulse that enters terminal 11, and select terminal b during a low level period to output reproduction signals from magnetic heads 5a and 6a or 5b and 6b. Take it out. The signals taken out from the switches 9 and 10 are the terminals a and b of the switch 12.
It is supplied to each of the detectors 13 and 14 as well as to the detectors 13 and 14 respectively. The detectors 13 and 14 each perform envelope detection of the supplied signal, and the detected voltage proportional to the reproduction level obtained here is detected by the comparator 1.
5 and compared. The comparator 15 generates a signal (switching signal) that is low level when the detected voltage of the detector 13 is high and high level when it is low, and outputs the signal to the data terminal D of the D-type flip-flop 16.
supply to. A horizontal synchronizing signal separated from the reproduced signal is supplied to the clock terminal CK of the flip-flop 16 via the terminal 17, and the flip-flop 16 inverts the output signal of the comparator 15 so that head switching noise is not displayed on the display screen. This output signal is synchronized with the timing of the horizontal synchronization signal, and this output signal is
is supplied to the control terminal of The switch 12 selects the signal from the switch 9 that enters the terminal a when the signal supplied to the control terminal is at a low level, and selects the signal from the switch 10 that enters the terminal b when the signal is at a high level. Connect the retrieved playback signal to terminal 1.
8 to the subsequent demodulation circuit.

For example, image track patterns T 1 , T ₂ , T ₃ , . . . in units of one field as shown by solid lines in FIG. 4 are recorded on the tape by the magnetic heads 2a and _2b .
When reproducing at triple speed, magnetic heads 2a and 3a scan portions I ₁ and I ₂ shown by broken lines, and magnetic heads 2b and 3b scan portions ₁ and ₂ shown by broken lines. If part I ₁ above is scanned, the third
From the terminal 18 shown in the figure, first, the reproduced signal of track T1 by the magnetic head _2a is outputted, then the reproduced signal of track _T2 by the magnetic head 3a is outputted, and then the reproduced signal of track _T3 by the magnetic head 2a is outputted.
A playback signal is output.

Problems to be Solved by the Invention In the circuit shown in FIG. 3, the switch 12 is switched in synchronization with the horizontal synchronizing signal to prevent switching noise occurring within the screen.
However, there is a risk that the horizontal synchronization signal that enters the terminal 17 may be mixed into the reproduced signal as noise, and
There was a problem in that the presence of switching noise during the horizontal synchronization period caused circuit malfunction.

Therefore, an object of the present invention is to provide a magnetic reproducing device that solves the above problems by using a control signal generation circuit and a muting circuit.

Means for Solving the Problems In the present invention, in order to solve the above problems, a plurality of playback signals reproduced from a plurality of recorded video tracks formed on a recording medium are switched and taken out respectively. In a magnetic reproducing device that performs dropout compensation by replacing the luminance signal demodulated from the reproduced signal with a luminance signal 1H (H is a horizontal scanning period) earlier when a dropout occurs in the reproduced signal, including the switching time of a plurality of reproduced signals. A muting circuit for forcibly muting the attached reproduction signal for a predetermined period and a dropout compensation circuit compensating for dropout based on the output signal of the muting circuit are provided.

Function: In the present invention, forced muting is performed on the extracted reproduced signal, and the dropout of the luminance signal due to the mutating is compensated for using the existing dropout compensation circuit. Therefore, there is no need to use a horizontal synchronization signal.

Example The outline of this example is to reduce the switching noise that occurs when switching between multiple playback signals played from multiple recorded video tracks and the noise bar during special playback, and to suppress the switching noise that occurs when switching between multiple playback signals that are played back from multiple recorded video tracks and the noise bar during special playback. The solution is to perform dropout compensation by muting the .

FIG. 1 shows a block diagram of an embodiment of the device of the present invention. In the figure, the same parts as in FIG. 3 are given the same reference numerals, and their explanations will be omitted. Recording track patterns T ₁ , T ₂ , T ₃ , etc. shown by solid lines in FIG. 4 are scanned in the order of parts I ₁ , ₁ , I ₂ , ₂ shown by broken lines 3
During double speed playback, the output signal of switch 9 shown in FIG. 1 changes as shown in FIG. 5A (T ₁ ,
T ₃ indicates the reproduced portion of tracks T ₁ and T ₃ respectively),
Further, the output reproduction signal of the switch 10 changes as shown in FIG. 5B ( _T2 indicates the reproduction portion of track _T2 ). Therefore, the detected voltages of the detectors 15 and 16 are as shown in C and D in the figure, and the comparator 15 outputs a signal with a waveform as shown in E in the figure.

The output signal of the comparator 15 is supplied to a control signal generation circuit 21 comprised of a delay circuit 20 and a monostable multivibrator. The delay circuit 20 delays the output signal of the comparator 15 by several microseconds to produce the switching signal shown in FIG. 5F, and supplies this to the control terminal of the switch 12. The control signal generation circuit 21 is the comparator 1
A pulse signal (control signal) as shown in FIG. 5G is generated by being triggered by the rising and falling edges of the output signal No. 5 and has a rising pulse width of about 10 μsec, and is supplied to the control terminal of the switch 22. Switch 12 is connected to terminal a of switch 22, which is a muting circuit.
A reproduced signal selected and extracted is supplied to the terminal b, and the terminal b is grounded. The switch 22 selects the reproduced signal at the terminal a when the signal supplied from the control signal generation circuit 21 is at a low level, and selects the terminal b when the signal is at a high level to forcibly mute the reproduced signal at the terminal a. As a result, a reproduced signal as shown in FIG. 5H is taken out from the switch 22.

That is, the reproduction signal is forcibly muted during a predetermined period including the switching time of the switching signal shown in FIG. F when the level of the reproduction signal is relatively low.

Here, the reproduction signal taken out from the switch 12 is supplied to a carrier color signal reproduction circuit (not shown).
The reproduction signal shown in FIG. 5H taken out from the switch 22 is supplied to an equalizer circuit 27 constituting an existing FM luminance signal reproduction circuit. A high-pass filter is provided at the first stage of the equalizer circuit 27, and the FM-modulated luminance signal (hereinafter referred to as "FM luminance signal") in the reproduced signal is extracted.
The frequency characteristics of the luminance signal are corrected and output. The output FM brightness signal of the equalizer circuit 27 is
The level is adjusted by the AGC circuit 23 and the signal is supplied to the dropout detector 24, where the presence or absence of a dropout in the FM luminance signal is detected.For example, a detection signal that becomes high level only when there is a dropout is generated, and the detection signal is sent to the switches 25 and 26, respectively. is supplied to the control terminal of By the way, the reproduced signal is as shown in FIG.
Since the dropout detector is forcibly muted in accordance with the switching timing of 2, even if there is no dropout in the reproduced signal input to the terminals 5a to 6b, the dropout detector will generate a detection signal corresponding to the pulse signal shown in FIG. 5G. Occur.

Also, FM passing through the dropout detector 24
The luminance signal is supplied to terminal a of switch 25.
The switch 25 selects terminal a when the control terminal is at low level, and selects terminal b when the control terminal is at high level. The FM brightness signal taken out from the switch 25 is branched into two, one of which is amplitude limited by a limiter 28 and then FM demodulated by an FM demodulator 29 to become a brightness signal, which is passed through a low-pass filter 30 and sent to terminal a of the switch 26. Supplied. The other FM brightness signal is delayed by 1H in the 1H delay circuit 31 and sent to switch 2.
The signal is supplied to the terminal b of the switch 26, the amplitude is limited by the limiter 32, the FM demodulation is performed by the FM demodulator 33 into a luminance signal, and the signal is passed through the low-pass filter 34 to the switch 26.
is supplied to terminal b of. A dropout compensation circuit is constituted by the dropout detector 24, switches 25, 26, 1H delay circuit, etc. When the control terminal is at low level, that is, when dropout is not detected, the switch 26 is connected to the terminal a.
is selected to extract the luminance signal from the low-pass filter 30, and when the level is high, that is, when dropout is detected, select terminal b to extract the luminance signal delayed by 1H from the low-pass filter 34. Output from terminal 35.

In other words, the high level period of the pulse signal shown in FIG. 5G corresponding to the switching of switch 12 is
The luminance signal from 1H ago is output from the terminal 35 in place of the luminance signal currently being reproduced. switch 26
Switching is also performed during the horizontal scanning period, but here the switching is of the demodulated luminance signal, so the switched FM luminance signal is
The pulsed head switching noise that occurs when FM demodulation does not occur.

As described above, the device of the present invention can prevent the occurrence of noise bars and head switching noise during special playback without using a horizontal synchronization signal.
There is no possibility that the horizontal synchronization signal will be mixed into the reproduced signal as noise. Furthermore, since the dropout compensation circuit conventionally provided in the FM luminance signal reproducing circuit is used, the circuit configuration is simple with few additional circuits.

Effects of the Invention As described above, the magnetic reproducing device according to the present invention has a muting circuit that mutes the reproduced signal during a predetermined period including the switching time of the switching signal, so the noise bar during special reproduction can be reduced without using a horizontal synchronization signal. It also has features such as being able to prevent the occurrence of head switching noise, eliminating the risk of a horizontal synchronization signal being mixed into the reproduced signal, and having a simple circuit configuration.

[Brief explanation of drawings]

FIG. 1 is a block system diagram of an embodiment of the device of the present invention, FIG. 2 is a diagram for explaining the magnetic head used in the device of the present invention, FIG. 3 is a block system diagram of an example of a conventional device, and FIG. The figure is a diagram for explaining the recorded video track pattern of the tape reproduced by the device of the present invention and its scanning, and FIG. 5 is a signal waveform diagram of each part of the device shown in FIG. 2a, 2b, 3a, 3b...magnetic head, 1
2, 22, 25, 26...Switch, 13, 14
... Wave detector, 15 ... Comparator, 20 ... Delay circuit, 21 ... Control signal generation circuit, 24 ... Dropout detector, 31 ... 1H delay circuit.

Claims (1)

[Claims for Utility Model Registration] A method for switching and extracting a plurality of reproduction signals reproduced from a plurality of recorded video tracks formed on a recording medium, and demodulating the reproduction signal from the reproduction signal when a dropout occurs in the extracted reproduction signal. In a magnetic reproducing device that performs drop-out compensation by replacing a luminance signal obtained by 1H (H is a horizontal scanning period) earlier with a luminance signal from 1H (H is a horizontal scanning period), the extracted reproduction signal is forcibly used for a predetermined period including the switching time of the plurality of reproduction signals. 1. A magnetic reproducing device comprising: a muting circuit for mutating; and a dropout compensation circuit for compensating for dropout based on an output signal of the muting circuit.