JPS63121370A - Signal reproducing system for magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To execute reproduction in which the occurrence of a V jitter is prevented by adding a correction pulse to a demodulation signal at the time of reproducing a video signal recorded in a field and not adding it at the time of reproducing the video signal recorded in a frame. CONSTITUTION:Magnetic heads 10A and 10B reproduce the video signals recorded in the field and the frame. An FM luminance signal YFM which is reproduced and separated by a filter 14 is inputted to an analog switch 22 directly through a limitter 18 or through a delay line 20. The switch 22 is alternately changed over on the side of contact points (a) and (b) per V when the field-recorded signal is reproduced, and it is changed over on the side of the contact point (a) when the frame-recorded signal is reproduced. The field- recorded signal is outputted through an FM demodulator 24, a synchronizing separation circuit 28, a correction pulse generation circuit 30 and an adder 26, and the frame-recorded signal is outputted without being added by other signal in the adder 26. Thus, reproduction in which the occurrence of the V jitter is prevented can be executed.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to No. ε reproduction method 2 of a magnetic recording and reproducing device that records a video signal on a recording medium such as a magnetic disk or reproduces a recorded video signal. In particular, the present invention relates to a signal reproducing method for a magnetic recording/reproducing apparatus that has two recording modes, field recording and frame recording, and reproduces video signals recorded in these two recording modes.

[Background of the invention]

It is well known that when constructing television images, so-called interlaced scanning is employed for horizontal scanning in order to reduce flickering to the eyes. In the case of the NTSC system, this interlaced scanning is a [2:1] interlaced scanning system. (2:1) In the interlaced scanning method, one screen (frame) is constructed by superimposing two coarse screens (fields) formed by one vertical scan. Therefore, the number of frame repetitions is 30 times per second, and the number of field repetitions is 60 times per second.In addition, odd and even fields are shifted by 0.5H with respect to the horizontal scanning period ([■)]. Become.

By the way, when recording video signals on a recording medium such as a magnetic tape or a magnetic disk, various recording methods are employed. Among these recording methods, a method has been proposed in which, for example, a video signal is separated into a luminance signal and a chroma signal, and each signal is subjected to certain signal processing and then subjected to FM modulation before being recorded on a magnetic recording medium or the like. There is.

In playback using this type of recording method, a frame signal is created from one type of field signal by scanning the same recorded portion twice, making use of the strong vertical correlation of the video signal.
A so-called field/frame conversion method is adopted. In this field/frame conversion method, it is not possible to convert the field signal into odd and even fields by simply repeating the same field signal. A through system) is formed, and by switching these every vertical scanning period (1), an odd field and an even field are obtained.

However, as mentioned above, the field signal is 0. When field/frame conversion is performed using the field/frame conversion method, which converts a 5H delayed signal and a non-delayed signal into frame signals by alternately selecting them every vertical scanning period, the resulting signal is displayed on the television screen. ■Shifter occurs in the reproduced image.

This V jitter is a deviation in the vertical direction (V direction) of an image having a width of l horizontal scanning line (IH) that is repeated at a field period on a television image. That is, the television image in this case is IH every field period (1/60 second).
The width varies up and down.

It is empirically known that this V jitter can be prevented from occurring by delaying the leading edge of the vertical synchronization signal included in the luminance signal by a period of 0.25H.

By the way, in a magnetic recording/reproducing device that records a video signal by selecting one of two recording modes, field recording and frame recording, field/frame conversion is performed only when reproducing a field-recorded video signal. Although it is necessary to take measures to prevent the occurrence of V jitter that occurs with field/frame conversion, these conversion processes are not necessary when playing frame-recorded video signals; There is no problem of this occurring.

[Purpose of the invention]

The present invention was made in view of these circumstances, and
In a signal reproducing method of a magnetic recording/reproducing device that has two recording modes, field recording and frame recording, and records a video signal by selecting one of these, the video signal can be reproduced according to the recording mode, and It is an object of the present invention to provide a signal reproducing method for a magnetic recording/reproducing apparatus that can prevent the occurrence of V jitter due to field/frame conversion when reproducing a video signal by field recording.

[Summary of the invention]

In order to achieve the above object, the present invention has two recording modes, field recording and frame recording, and when reproducing a field recorded video signal, the field signal that has been FM modulated and recorded on a magnetic recording medium is repeated. play,
The reproduced FM field signal is passed through a delay circuit whose delay time is 1/2 horizontal scanning period, and the FM field signal delayed by 1/2 horizontal scanning period and the undelayed FM field signal are separated.
A signal reproducing method for a magnetic recording and reproducing device that obtains a frame signal by alternately selecting a field signal and a field signal every vertical scanning period by switching a switch, and then performs field/frame conversion to demodulate the output signal of the switch. When reproducing a field-recorded video signal, a vertical synchronization signal is detected from the demodulated output, and a correction pulse is created based on the vertical synchronization signal to delay the leading edge of the vertical synchronization signal by a predetermined amount. , the correction pulse is added to the demodulated signal, and the correction pulse is not added to the demodulated signal when reproducing a frame-recorded video signal.

[Embodiments of the invention]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of a signal reproducing system of a magnetic recording/reproducing apparatus according to the present invention will be described below with reference to the accompanying drawings. FIG. 1 shows the configuration of a reproducing system of a magnetic recording/reproducing apparatus to which the present invention is applied. In the same figure, IOA, IOB
is a magnetic head that repeatedly reproduces field signals recorded on two adjacent tracks on a magnetic disk (not shown) which are arranged adjacent to each other. magnetic head IOA
, the field signals regenerated by IOB are outputted to filter 14.16 via amplifiers 12A, 12B and analog switch 32, respectively.
The signal is separated into the FM luminance signal YFa and the FM color signals C7 and C4. Here, the description of the color signal reproduction system will be omitted since it is not directly related to the gist of the present invention.

Incidentally, when the analog switch 32 reproduces the frame-recorded video signal, the control signal 5 is outputted by a control circuit (not shown) as shown in FIG. 2(B) (3).
The field signal (even field or odd field video signal) which is switched to the contact a and b sides alternately every 1■ by the WP(C) and reproduced by the magnetic head 10A and IOB is input to the filter 14, and the FM Only the luminance signal YFH is extracted.

Furthermore, when reproducing field-recorded video signals, the analog switch 32 always keeps the control signal SWP (C) at a high level, as shown in FIG. switched, magnetic head I
Only the field signal reproduced by the OA is sent to the amplifier 12.
A, filter 14.16 via analog switch 32
is output to.

After the amplitude fluctuation is removed by the limiter 18, the FM luminance signal Y is directly or connected to the 0.5H delay line 20.
The signal is input to the analog switch 22 via. The analog switch 22 is shown in FIG. 2 (A) (1) or the same figure (B
) (1”) Control signal SWP (Y) at the timing shown in
Switching control is performed between contacts a and b. In other words, when playing back video signals recorded in the field, the field/
Since it is necessary to perform frame conversion, analog switch 2
2 is controlled so as to alternately switch to the contact a and b sides every 1.times.2 at the timing shown in FIG. 2(A) (1) (this will be described later).

On the other hand, when reproducing a frame-recorded video signal, there is no need to perform field/frame conversion, so the control signal SWP (Y) becomes high level (see Figure 2 (B).
)(1)), the analog switch 22 remains switched to the contact a side.

Now, the frame signal obtained via the analog switch 22 is outputted to the outside via an FM demodulator 24 and an adder circuit 26.

When reproducing a frame-recorded video signal, field/frame conversion is not performed, so there is no need for means to prevent jitter associated with this. 26, the signal is output from the adding circuit 26 to the outside without being added to other signals.

On the other hand, when reproducing field-recorded video signals, in order to prevent the occurrence of jitter due to field/frame conversion, the leading edge of the vertical synchronization signal in the FM luminance signal is set by 0.25H. need to be delayed.

For this purpose, a synchronization separation circuit 28, a correction pulse generation circuit 30
is provided. Synchronization separation circuit 2nd is FM demodulator 24
The correction pulse generation circuit 30 extracts a composite synchronization signal from the demodulated output from the
．． This is a circuit that creates a correction pulse necessary to delay by 25H.

The analog switch 34 is a switch controlled by a control signal SWP (Z) output from a control circuit (not shown), and when reproducing a frame-recorded video signal, the field recording When reproducing the video signal, the contact is switched to the contact side (Fig. 2 (A) (2), (B) (2)).

In the above configuration, the operation when reproducing a field-recorded video signal will first be described. In this case, the analog switches 32 and 34 are switched to the contact a side.

The FM field signal repeatedly reproduced by the magnetic head IOA is amplified by the amplifier 12A and then output to the filter 14 via the analog switch 32. The filter 14 extracts the FM luminance signal Y□, and the limiter 18 removes amplitude fluctuations. Thereafter, field/frame conversion is performed under switching control of the analog switch 22. That is, for each vertical scanning period (IV), the through FM luminance signal 100 and the 0.5H delayed FM
1v period 51 (1v period 51 (
In the period 52 from the front equalization pulse section to the back equalization pulse section in Fig. 3 (C)), the through F
The input analog switch 22 is controlled so that the M, ti degree multiplication signal 100 is selected (Fig. 3(a), (b), (
C1).

Note that the third button indicating the switching timing of the analog switch 22
Figure (C) is the same as the signal shown in Figure 2 (A) < 1), and for convenience of explanation, the time axis is shown reduced compared to the other signals shown in Figure 3. For example, Periods 52 and 53 in FIG. 5C correspond to periods 60 and 61 in the FM luminance signal 102 shown in FIG. 1B.

Now, the frame signal 104 (or 106) (FIG. 3(d), (e)) obtained by switching the analog switch 22 is demodulated by the FM demodulator 24 and output to the adder circuit 26 and the sync separation circuit 28. be done. A composite synchronization signal is extracted by the synchronization separation circuit 28 from the FM demodulation output input to the synchronization separation circuit 28 and output to the correction pulse generation circuit 30.

The correction pulse creation circuit 30 creates a correction pulse based on the composite synchronization signal output from the synchronization separation circuit 28, and the correction pulse is output to the addition circuit 26 via the analog switch 34. As a result, the correction pulse is
6, the leading edge of the vertical synchronization signal is added to the luminance signal output from the FM demodulator 24, and the leading edge of the vertical synchronization signal is added to the luminance signal output from the FM demodulator 24 by the adding circuit 26.
A baseband luminance signal delayed by 25H is output.

Next, the configuration of the correction pulse generation circuit 30 is shown in FIG. In the figure, the correction pulse generation circuit 30 is the synchronization separation circuit 28.
The vertical synchronization signal is separated from the composite synchronization signal 110 (112) outputted from the composite synchronization signal 110 (112), and the vertical synchronization signal is predetermined! (for example, 0.25H) ■ Synchronous separation/delay circuit 3
02, a synchronization separation circuit 304 that separates the vertical synchronization signal from the composite synchronization signal, and an analog switch 312 whose switching is controlled by AND gates 308 and 310 and a switching pulse SWP (C) output from a control circuit (not shown). and an arithmetic circuit 306 consisting of.

In the above configuration, the composite synchronization signal outputted from the synchronization separation circuit 28 is a composite synchronization signal 110 obtained from the through multi-luminance signal and a composite synchronization signal 110 obtained from the through multi-luminance signal as shown in FIGS.
These composite synchronization signals 110.1 include a composite synchronization signal 112 obtained from a demodulated luminance signal delayed by 5H.
12, during the vertical retrace period T from the front equalization pulse to the back equalization pulse, the field/
Since the through FM luminance signal is selected during frame conversion, the output timings of the horizontal synchronization signal, equivalent pulse, and vertical synchronization signal are exactly the same.

■The synchronization M/delay circuit 302 separates the vertical synchronization signal from the composite synchronization signal 110 (or 112), inverts the vertical synchronization signal, and delays it by a predetermined amount, for example, 0°25H. It is output to the input terminal (Fig. 5(C)). ■The AND gate 308 takes the AND of the output signal of the synchronization #l/delay circuit 302 and the composite synchronization signal 110 (or 112), and the AND gate 308
The output signal (Fig. 5 (g), (h)) of AND gate 3
It is output to one input terminal of 10.

Further, the V synchronization separation circuit 304 separates the vertical synchronization signal from the composite synchronization signal 110 (or 112), and the AND gate 3
10 (FIG. 5(d)). In the AND gate 310, the output signal of the AND gate 308 and ■
An AND with the vertical synchronization signal output from the synchronization separation circuit 304 is performed (FIG. 5(i)). This and gate 3
The pulse signal obtained as the 10 output signal is output at a period of 1.5 times, that is, every time the field signal delayed by 0.58 and the through field signal are alternately output.

However, what is required as the correction pulse is only the pulse signal output from the AND gate 310 during the period in which the field signal delayed by 0.5H is output.

Therefore, the analog switch 312, which is switched and controlled by the switching pulse SWP (C) output at the timing shown in FIG. 5(e),
The pulse I word output from, that is, the correction pulse 11
6 is output to the adder 26. Here, the analog switch 312 is switched to the contact a side during a period in which a field signal delayed by 0.5H every 1 is output, and to the contact a side during a period in which a through field signal is output. In addition, the switching pulse SWP shown in <6) in the same figure
For convenience of explanation, the time axis of (C) is shown reduced compared to other signals.
).

The correction pulse 116 is added to the demodulated luminance signal output from the FM demodulator 24 by the adder 26, and the leading edge of the vertical synchronization signal ends up being the pulse width of the correction pulse (the shaded part in FIG. 5(j)). A baseband luminance signal delayed by 0°25H, which corresponds to , is obtained ((j) in the same figure).

Next, a specific circuit configuration example of the correction pulse generation circuit 30 is shown in FIG. 6, in which V synchronization i! The il/delay circuit 302 is composed of an integrating circuit made up of resistors R3 and R4, a variable resistor VR1, and capacitors C1, C2, and C3, and an amplification stage made up of a transistor Q2 and a resistor R5. The variable resistor VRI is configured to be able to adjust the delay amount of the vertical synchronization signal, and for example, the delay amount is set to a time corresponding to 0.25H as described above.

Also, the synchronous separation circuit 304 includes a diode D1, capacitors C5, C6, resistors R8, R9, RIO1Rll, R1
2. Consists of a variable resistor VR2, transistors Q4 and C5, and the arithmetic circuit 306 includes diodes D2 and D3.
, D4, resistors R13 and R14, and a transistor Q6. Here, diodes D2 and D3 are connected to AND gate 308, and transistor Q6 is connected to AND gate 308.
10 and analog switch 312 (Fig. 4)
. An emitter follower is configured by transistor Q1 and resistors R1 and R2, and transistor Q3 and resistors R6 and R7
and transistor Q3 constitute an amplification stage.

In the above configuration, the composite synchronization signal output from the synchronization separation circuit 28 is transmitted through the resistor R3 via the emitter follower described above.
, R4, variable resistance VRI and capacitors C1, C2, C
3, is integrated by the integrating circuit, is further amplified by the transistor Q2, and is output from the collector of the transistor Q2 (Fig. 5 (C)).
.

On the other hand, the composite synchronization signal outputted from the emitter of transistor Q1 (FIGS. 5(a) and (b)) is ANDed with the output signal outputted from the collector of transistor Q2 via diode D2 via diode D3. (Fig. 5 (g), (h)).

Further, the composite synchronization signal inputted to the V synchronization separation circuit 304 via the transistor Q3 of the amplification stage is integrated by an integrating circuit (with a small time constant) consisting of a diode D1 and a capacitor C5, and a signal almost synchronized with the vertical synchronization signal is obtained. The signal is extracted and output to the base of transistor Q6 via transistors Q4 and C5 of the amplification stage. This transistor Q6
The output signal of the V synchronization separation circuit 304, which is output at the pace of , is a signal obtained by inverting the signal shown in FIG.
becomes conductive, and when it is outputted through the transistor Q6, it is inverted and becomes the same signal as shown in FIG. 5(d). This signal is logically ANDed with the signal output via diodes D2 and D3, and a correction pulse 116 is obtained.

Next, the case of reproducing a frame-recorded video signal will be explained. In this case, the analog switch 32
As shown in Figure (B) (2), the contacts are alternately switched to the a and b sides for each IV. Odd field or even field video signals repeatedly reproduced by the magnetic heads IOA and IOB are output to filters 14 and 16 via amplifiers 12A and 12B, respectively. The filter 14 extracts the FM brightness signal Y8, and outputs the FM brightness signal YFH.
The amplitude fluctuation is removed by the limiter 18. Here, the analog switch 22 for performing field/frame conversion is always switched to the contact a side as shown in FIG. 2 (B) (2) when reproducing the frame-recorded video signal. The output signal of the limiter 18 is directly outputted to the FM demodulator 24, and after being demodulated by the FM demodulator 24, it is outputted to the addition circuit 26 and the synchronous separation circuit 28. In addition, the analog switch 34 for adding the correction pulse outputted by the correction pulse generation circuit 32 to the demodulation output outputted from the FM demodulator 24 when reproducing a field-recorded video signal is in the contact side in this state. switched and becomes grounded. Therefore, the demodulated output of the FM demodulator 24 is directly output to the outside via the adder circuit 26.

〔Effect of the invention〕

As explained above, the present invention has two recording modes, field recording and frame recording, and in a signal reproduction method of a magnetic recording and reproducing apparatus that performs field/frame conversion when reproducing a field-recorded video signal, field When reproducing a recorded video signal, a vertical synchronization signal is detected from the FM demodulation output, a correction pulse is created to delay the leading edge of the vertical synchronization signal by a predetermined amount based on the vertical synchronization signal, and the correction is performed. According to the present invention, since the pulse is added to the demodulated signal and the correction pulse is not added to the demodulated signal when reproducing the frame-recorded video signal, the present invention adds the correction pulse to the demodulated signal according to the recording mode. During playback and playback of video signals by field recording, it is possible to prevent the occurrence of jitter due to field/frame conversion.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing a schematic configuration of a reproducing system of a magnetic recording/reproducing apparatus to which the present invention is applied, and Fig. 2 shows the operating states of various analog switches used in the magnetic recording/reproducing apparatus shown in Fig. 1. 3 is a timing chart showing the operation of the reproducing system of the magnetic recording and reproducing apparatus shown in FIG. 1, FIG. 4 is a configuration diagram showing the schematic configuration of the correction pulse generation circuit in FIG. 1, and FIG. 4 is a timing chart showing the operation of the correction pulse generation circuit shown in FIG. 4, and FIG. 6 is a circuit diagram showing a specific example of the correction pulse generation circuit. 10A, IOB...magnetic head, 20.0.5
H delay line, 22.32.34...analog switch, 24...FM demodulator, 26...
-Addition circuit, 28...Synchronization separation circuit, 3o...
Correction pulse creation circuit.

Claims (1)

[Claims] It has two recording modes: field recording and frame recording, and when playing field recorded video signals, FM
The modulated field signal recorded on the magnetic recording medium is repeatedly reproduced, and the reproduced FM field signal is passed through a delay circuit whose delay time is 1/2 horizontal scanning period.
A frame signal is obtained by alternately selecting an FM field signal delayed by two horizontal scanning periods and an FM field signal not delayed by switching a switch every vertical scanning period, and then demodulating the output signal of the switch. In a signal reproducing method of a magnetic recording and reproducing device that performs field/frame conversion, when reproducing a field recorded video signal, a vertical synchronizing signal is detected from the demodulated output, and a vertical synchronizing signal is detected based on the vertical synchronizing signal. Create a correction pulse that delays the leading edge of the vertical synchronization signal by a predetermined amount, add the correction pulse to the demodulation signal, and add the correction pulse to the demodulation signal when reproducing the frame-recorded video signal. A signal reproducing method for a magnetic recording/reproducing device characterized by: