JPS603263B2 - Color video signal recording and reproducing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a color video signal recording and reproducing method having a reproduction color signal phase inversion circuit for obtaining a color signal having a normal phase when reproducing a color signal recorded on a recording medium such as a magnetic tape. It is related to the device.

In simple VTRs, the image quality of the reproduced screen deteriorates due to the so-called crosstalk phenomenon in which the head picks up recording signals from adjacent tracks during reproduction, and this must be prevented.

For this reason, some methods provide a gap called a guard band between recording tracks, but high-density recording methods that eliminate this guard band are currently becoming mainstream. In the latter case, since the recording frequency is high, the crosstalk of the luminance signal is solved by setting the two head gaps at an angle called the azimuth angle so that the angle differs between adjacent tracks. Crosstalk cannot be removed by changing the azimuth angle because its recording frequency is low. Therefore, it is removed by phase manipulation and comb filters during recording and playback. The configuration of this comb filter is shown in FIG. 1 is an input terminal, 2 is an output terminal, and 3 is a delay element having a delay time of one horizontal period.

In this filter, due to the action of the delay element 3, the sum of the signal of a certain horizontal period (hereinafter referred to as day) and the input signal of one horizontal period (IH) before appears in the output. Therefore, by controlling the phase of that input, the phase of the reproduced color signal component of the main track is aligned, and the phase of the crosstalk component of the adjacent track is reversed for each IH, so that the crosstalk component is canceled.
Only the re-output error signal of the main track appears at the output. An example of performing such an operation will be specifically described below. In a certain field V, input a comb filter with horizontal period Hn.
Let it be expressed as (1).

Here, An is a reproduced signal component from the main track, Bn is a reproduced crosstalk component from an adjacent track, and the arrow represents the phase of the burst signal component. (→ is o
o, ↑9bi...) Current horizontal period ratio, day,, day 2, day 3...
...Assume that the phase relationship of the input to the time comb filter is as follows by phase manipulation. Therefore, since An=An+1 and Bn=Bn+1, the day and hour outputs are as follows.

friend.

Ten ears. Similarly, the output for 10 friends, 10 mins, 3 secrets, day 2, day 3, etc. is as follows.

Therefore, crosstalk component Bn is removed. However, although it is sufficient that the phases of the main track signals input to the comb filter are always the same, they may shift when switching fields. In reality, if it is up to 900 degrees, it will be corrected by the APC system, but if it is more than that, that is, the phase shift is 1800 degrees, the APC system will correct it.
It cannot be corrected with a PC system. As a result, a screen with normal hue cannot be obtained, so a circuit is added to invert the input signal of the comb filter. FIG. 2 shows an example of a phase control section including this reproduction phase inversion circuit.
In FIG. 2, 4 is a playback signal input terminal, 5 is a converter, 6 is a 3.58 MHz band pass filter, 7 is a comb filter, 8 is a 4.21 MHz band pass filter, 9 is a converter, 10 is 3. Isomisaki ZV. C. 0, 1
1 is a 40-day 4-phase logic circuit, 1 2 is an ID detection circuit, 1 3 is 3. 14 is a burst gate circuit, and 15 is an output terminal. The color signal is recorded using a low-frequency conversion recording method, and in this example, the color signal is converted from 3.5 to 40.
It is recorded by converting it to 62 Hz (262 Hz, where 2 is the horizontal scanning frequency), but in the CH-1 track, the phase is advanced by 900 for each IH, and in the CH-12 track, the phase is advanced by 900 for each IH. It is recorded with a delay of 900. Therefore, during playback, we return to the original 3.58MHz and at the same time manipulate the phase.
A phase-related signal such as the '21 formula is
You must make a donation to the son. Converter 5 and filter 6 do this. Party evening 5 is 4.
Approximately 21M (=40〆 day 13.5Kitsuneyamaz) was supplied,
This 4.21MHz has a phase of 9 for each IH on CH-1.
When reproducing 00-advanced CH-2, the delay is delayed by 90 degrees for each IH, and the frequency is converted by this, and only the signal of 3 Isomisaki Z is extracted by the filter 6. 4.
This is a method of advancing or delaying the phase of 21MHz by 900 for each IH, but this 4.21MHz is 3. Spot MHzV. C. Converter 9 and filter 8
Therefore, it is actually a four-phase logic circuit 11.
The phase of 40 days is delayed by 900 for each IH on CH-1, and advanced by 900 on CH-2.

The above situation is shown in FIG. In the figure, a is 40 days, and phase b of the output signal of the four-phase logic circuit 11 is 3 Isomisaki ZV.
．． C. 0.10, c is the phase of the input 4.21 MHz signal of the converter 5, d is the phase of the 40 day reproduction color signal burst, e is the phase of the input burst signal of the comb filter 7, "Maso This is the phase of the output burst signal.In addition, in d and e, the upper row shows the main track reproduction signal, and the lower row shows the phase of the stalk.In FIG. As I pointed out earlier, this is corrected by the ID detection circuits 1 2 and 2 shown in Figure 2.
3. Spotted MHz reference oscillator 1 3, burst gate circuit 1
It is 4. The burst gate circuit 14 takes out the burst signal from the output of the comb filter 7, and the m detection circuit 12
supply to. This m detection circuit 12 is 3. The phase of the signal from the irregular MHz reference oscillator 13 and the & phase of the signal from the burst gate circuit 14 are compared, and in one day the phase difference is ±18.
00, the pulse called m pulse will be 4 on the next day.
The voltage is applied to the phase logic circuit 11. and by this 4
phase. The logic circuit 11 inverts the phase of the 40th day's signal output on that day. (For this reason, the output for 40 days is IH
Since it is determined whether the clock lags or advances by 900 every day, all outputs for subsequent days will be reversed. ) Due to this inversion operation of the 40-day signal, the output of the comb filter is also inverted, and the state in which the phase returns to normal is shown by the dashed arrow in FIG.

Here, it is assumed that the inversion of the comb filter output at the time of Ho is detected, and the ID pulse is added at day and time. As described above, the four-phase logic circuit 11 shown in FIG. 2 plays an important role in phase manipulation, and a specific example of this circuit is shown in FIG.

Also, the 5th section explains how this circuit outputs a 4-phase signal on the 40th by raising the waveform phase of each part.
It is a diagram. In FIG. 4, 16 is an input terminal for horizontal synchronizing pulses, 17 is an input terminal for field switching signals, and 18 is an input terminal for field switching signals.
, 19 is the input terminal of the 40〆H signal, and the input terminal 19 has 9
A 40 day signal with an advanced 00 phase is applied. 20 is m
The pulse input terminal 21 is an output terminal for a 4-phase 40-day signal.

In addition, in FIG. 5, 16, 21 to 30 are the signal waveforms 21, 2 at the terminals and lines with the same symbols shown in FIG.
5 to 29 represent the phase of the 40th day by the direction of the arrow, and the box indicates that there is no signal on the 40th day between them and the potential is at a low level. As you can see from Figure 5,
In CH-1, the phase of the 40 day output 21 is delayed by 90 degrees for each IH, and when the ID pulse 20 is added, the phase is reversed on that day. Further, in CH-2, the phase of the 40-day output advances by 900 for each IH, and as in CH-1, phase inversion occurs due to the ID pulse. In this way, crosstalk between adjacent tracks is removed by a phase manipulation system including a phase inversion circuit using m-pulses and a comb filter, but when the field is switched as shown in Figure 6, the phase of the main track signal is m pulses are generated in the phase of adjacent crosstalk.

Figure 6 shows the phase of the burst signal input to the comb filter during each horizontal period before and after a certain field switching point A-A. Expressed as H5 foundation, the comb filter output is
is next to [4}, and no ID pulse will be generated the next day.

&25, day, and time are before and after the field connection, so we do not consider them, but if we consider the filter output at 2 o'clock on the day, we get the following. Ana, ten heads. Jugen 20 ears = 2 '51 In this way, the output is in the opposite phase to that before field switching, so an ID pulse is generated at ratio time, and the output at that time is x 20 every 20 + ears = 3 '61 Since the crosstalk component is output and the phase is also reversed, an ID pulse is generated, and on day 4, every 30 tiles = 30 x 40 beans = every
[71 is output.

And since the ID pulse occurs at 5 o'clock on the day, every 4 o'clock 4 o'clock
Ten friends 50 ears = Tai 5 '81.

In the case shown in FIG. 6, the main track signal is not reproduced in a normal phase, which causes color unevenness, color disappearance, and color change in the upper part of the screen. This phenomenon occurs not only in the system shown in Figure 2, which performs phase manipulation, but also in systems that perform phase manipulation in some way during recording and playback, and use a comb filter to remove crosstalk in the reproduced color signal. there is a possibility. SUMMARY OF THE INVENTION An object of the present invention is to provide a color video signal recording and reproducing apparatus which eliminates the above-mentioned drawbacks of the prior art and can always obtain a reproduced color signal with a normal phase.

A feature of the present invention is that when an ID pulse is generated in a certain horizontal period and the phase of the reproduced color signal is inverted, the ID pulse supplied in the next horizontal period is ignored, and a phase inversion prevention circuit is provided that does not cause phase inversion. It is to have.

With this phase reversal prevention circuit, the sixth
At the time of field switching as shown in the figure, phase reversal does not occur even if the ID pulse occurs at 4 o'clock on the day, so
10Z 4 10 ears = 4 '9) appears in the output of the comb filter, and the output at 5 o'clock on the day becomes 5 o'clock, 10 times, 5 f ears = 5 00, which is a normal output with a constant phase.

In this manner, this phase reversal prevention circuit can improve problems such as color fading, color unevenness, and color change in the upper part of the screen, which have been problems in the prior art. It has been explained that in the system example shown in FIG. 2, the phase inversion of the reproduced color signal by the ID pulse is performed by inverting the output of the phantom phase logic circuit 11.

Therefore, in order to embody the present invention, if a phase inversion occurs in this circuit in a certain horizontal period, the inversion may not occur even if an ID pulse is supplied in the next horizontal period. This is the ID in the 40 days 4-phase logic circuit shown in Figure 4.
This can be realized by adding a monostable multipipulator with a pulse width of 1 day (T<2/day) between the pulse input terminal 20 and the clock terminal of the D flip-flop 31. Figure 7 shows the main part. In the figure, numeral 34 is a monostable multipipulator. When the ID pulse 20 as shown in FIG.
At that time, the four-phase output 21' is as shown in FIG. 5.

Looking at the difference between 21 and 21' in the figure, it is clear that in CH-2, the phase inversion of the 21' output does not occur due to the second m pulse, and the effect of preventing phase inversion is realized. On the other hand, instead of the monostable multipipulator 34, a phase reversal prevention circuit with the same characteristics can be realized by using two stages of D flip-flops as shown in Fig. 8, and this circuit does not require external pins as an internal circuit of the IC. Therefore, it is advantageous.

In the figure, 21 is a 40-day four-phase output, and 35 is a horizontal synchronizing pulse input terminal. FIG. 9 shows the signal waveforms of the terminals and lines 21, 36 to 39 of FIG. 8 and the lines 32, 33 of FIG. 7 when the same ID pulse is applied. Here, the D flip-flop 40 is the output Q of the D flip-flop 41.
Clearing is assumed to occur when is at a low level potential. As can be seen from FIG. 9, the waveforms 39 and 33 are equal, and it can be seen that the circuit of FIG. 8 effectively uses the timing of the horizontal synchronizing pulse and the ID pulse to function equivalent to a monostable multipipelator. Although the present example has been described in which a horizontal synchronizing pulse is applied to the input terminal 35, the present invention is not limited to this, and any signal that is repeated in a horizontal period can be used. In addition, even if the monostable multipipulator in Figure 7 is replaced with a flip-flop, phase inversion can be prevented in the same way as in Figures 7 and 8, but in this case, after inversion occurs in a certain horizontal period, the next When no ID pulse is input during the horizontal period, the ID pulse is ignored no matter how many days later.

In other words, even-numbered m pulses are ignored and the phase is not inverted, but there is actually no problem with the round gate and the flip-flop 1
It only requires a stage, which is advantageous in terms of cost. The above circuit example is 4
Although the phase of the 40th phase converted into four phases was manipulated by the output of the phase logic circuit, it is also possible to manipulate the phase within the logic circuit by adding a differentiation circuit or the like.

An example is shown in FIG. In the same figure, 42, 43
is a differential circuit. Although this example uses a monostable multivibrator, the monostable multivibrator can be replaced with one or two stages of flip-flops, as in the previous example shown in FIGS. 7 and 8. In the conventional method, when a large skew occurs, a large number of ID pulses are generated in succession, causing problems such as color fading, color change, and color unevenness at the top of the screen.

On the other hand, the color video signal recording and reproducing apparatus equipped with a phase reversal prevention circuit according to the present invention can solve this problem. Alternatively, it can be easily realized by adding a fritflop.

[Brief explanation of drawings]

Figure 1 is a block diagram showing the configuration of a comb filter, Figure 2 is a block diagram showing an example of a phase manipulation system, and Figure 3 is a block diagram showing the configuration of a comb filter.
The figure shows the phase of each part of the signal in Fig. 2, Fig. 4 is a block diagram showing a conventional example of a four-phase logic circuit used in the system of Fig. 2, and Fig. 5 shows the waveforms and signals of each part in Fig. 4. FIG. 6 is a diagram showing an example of a signal input to a comb filter, and FIGS.
A block diagram showing the main parts of the phase logic circuit, FIG.
FIG. 10 is a block diagram showing another embodiment of the present invention. 3... Delay element, 5, 9... Converter, 7...
Comb filter, 11...4-phase logic circuit, 12...ID
Detection circuit, 31, 40, 41...D flip-flop, 3
4... Monostable multipipulator, 42, 43... Differential circuit. 2 figures, 3 figures, 4 figures, S figures, 5 figures, 8 figures? Diagram 'o diagram

Claims (1)

[Claims] 1. A comb-shaped filter that adds a reproduced color signal of a certain horizontal period and one horizontal period before that during reproduction, and a phase detection circuit that detects the phase of a burst signal output from the comb-shaped filter, the phase detection circuit In a color video signal recording and reproducing apparatus using a color signal reduction conversion recording method having a phase inversion circuit that inverts the phase of the reproduced color signal by output, when the phase of the reproduced color signal is inverted in a certain horizontal period, the following occurs. A color video signal recording and reproducing device characterized by adding a phase reversal prevention device that does not perform phase reversal in a horizontal period.