JPS6035723B2 - Video signal recording method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a video signal recording method, in which a rotational phase error of a rotary head caused during recording due to disturbance is detected as a comparison signal and a reference signal, and a phase difference obtained from the comparison signal and the reference signal is detected. By delaying the video signal to be recorded according to the error voltage, it is possible to record the horizontal synchronization signals recorded on each track with a simple configuration so as to align them with high precision between each track, thereby reducing crosstalk and improving the S/ It is an object of the present invention to provide a recording method capable of obtaining stable and high-quality images of N.

More stable in IJ cal scan type magnetic recording and reproducing devices such as VTRs that record video signals by sequentially forming tracks inclined with respect to the longitudinal direction of the magnetic tape using a rotating head and reproducing the signals. In order to obtain a high-quality reproduced image, it is necessary to perform recording with high precision in so-called date alignment, which aligns the recording positions of recording horizontal synchronization signals between adjacent tracks.

FIG. 1 shows a block diagram of an example of a conventional video signal recording system.

In the figure, a video signal to be recorded that has entered an input terminal 1 is supplied to a video signal recording system 2 and a reference signal generation system 3, respectively. The video signal recording system 2 processes the video signal into a signal format suitable for magnetic recording and outputs it to rotary heads 10a and 10b, which rotate integrally with a rotary drum 9, which will be described later, and have, for example, different azimuth angles. . On the other hand, the reference signal generation system 3 separates the vertical synchronization signal from the input video signal, shapes the signal, generates a symmetrical square wave of, for example, 30 Hz as a reference signal, and supplies it to the phase comparator 4. The rotating drum 9 is rotated by a drum motor 8,
Magnets 11a and 11b are located at 180o opposite positions, respectively.
is attached.

Since the magnets 11a and 11b are laid horizontally so as to cross in front of the pickup head 5 as the rotating drum 9 rotates, the magnets 11a and 11b
A rotation detection signal is output every time 1a, 11b passes and is supplied to the comparison signal generation system 6. A trapezoidal wave signal synchronized with the rotational phase of the rotary drum 9 is generated by the comparison signal generation system 6 and supplied to the phase comparator 4, where the phase is compared with the reference signal. As a result, a phase error voltage corresponding to the error in the rotational phase of the rotating drum is extracted from the phase comparator 4 and supplied to the discret control system 7. This disc control system 7 keeps the rotational speed of the drum motor 8 constant, and at the same time controls the rotational phase to match the reference signal using the phase error voltage from the phase comparator 4. For example, when the rotational speed of the rotary drum 9 becomes faster than the steady speed, the phase of the output comparison signal of the comparison signal generation system 6 advances, and the phase error voltage from the phase comparator 4 decreases accordingly. The control system 7 reduces the rotational speed of the drum motor 8, thereby maintaining the rotational speed and rotational phase of the rotating drum 9 in a constant steady state. In this way, the drum servo system allows the rotating drum 9 and the rotating heads 10a and 10b to maintain a constant rotational speed and rotational phase.
is rotated, so that the input video signal is transmitted in the longitudinal direction of the magnetic tape 34 onto the magnetic tape 34, which is attached to the rotating drum 9 for about 1800 mm as shown by the dashed line and is made to run in the longitudinal direction of the magnetic tape 34. Recording is performed by sequentially forming tracks that are oblique to each other, and the vertical synchronizing signal recording position and horizontal synchronizing signal recording position of each track are aligned in a fixed direction. However, in reality, the rotating head 10
There is a drawback in that the time axis of the video signal drifts due to disturbances such as rotational irregularities of a and 10b, and the recording position of the horizontal synchronizing signal is not necessarily aligned in a certain direction with high precision. When a magnetic tape in which the recording positions of the horizontal synchronizing signals are not precisely aligned is reproduced, there is a drawback that crosstalk from adjacent tracks becomes noticeable. This drawback is that of conventional VTRs.
There were no particular problems with respect to the tape speed, track width, etc. used in magnetic green image reproducing apparatuses such as the above, and crosstalk from adjacent tracks could usually be adequately dealt with by the azimuth recording method. However, from the viewpoint of realizing a method for recording video signals for as long as possible on a magnetic tape of limited length, as the running speed of magnetic tape decreases,
■Decrease in actual track width, ■S due to decrease in recording level
Due to the deterioration of S/N, etc., the above-mentioned drawbacks become noticeable as an adverse effect, and this adverse effect causes crosstalk and S/N of the reproduced image.
This resulted in deterioration of the quality of the reproduced image depending on the pattern.

The present invention eliminates the above-mentioned drawbacks, and embodiments thereof will be described below with reference to FIGS. 2 to 4.

FIG. 2 shows a block system diagram of a first embodiment of the video signal recording system according to the present invention.

In the figure, the same components as in FIG. 1 are denoted by the same reference numerals, and their explanations will be omitted. In FIG. 2, an input terminal 12 receives a video signal to be recorded. Here, in the specification of this application, "video signal" of course refers to a black and white video signal or a color video signal, but a modulated digital signal obtained by pulse code modulating an audio signal or other analog information signal is a composite video signal. It also includes digital signals that are present at the video signal position. A color video signal to be recorded that has entered from the input terminal 12 is supplied to a variable delay circuit 13 composed of, for example, a charge coupled device (CCD), and is also supplied to a vertical synchronization signal position separation circuit 14. Here, the vertical synchronization signal is separated and output.

This vertical synchronization signal is connected to a monostable multipipe generator (hereinafter referred to as "
After being counted down to 1/2 by a pulse shaping circuit 15 (abbreviated as "mono-multi"), it is supplied to a phase comparator 4 via a pulse shaping circuit 16. Each of the circuits 14 to 16 has the same configuration as the reference signal generation system 3. On the other hand, the rotation detection signal detected by the pickup head 5 triggers the monomultis 17 and 18 alternately every half rotation of the rotating drum 9.

Pulses taken out alternately from the monomultis 17 and 18 every half rotation of the rotary drum 9 are applied to the flip-flop 19 to trigger it. As a result, a symmetrical square wave whose period corresponds to one revolution of the rotary drum 9 is taken out from the flip-flop 19, converted into a trapezoidal wave by the trapezoidal wave forming circuit 2, and then supplied to the phase comparator 4. Circuit 1 above
Reference numerals 7 to 20 have the same configuration as the comparison signal generation system 6.
That is, the phase comparator 4 compares the phases of the reference signal from the pulse shaping circuit 16 and the trapezoidal wave (comparison signal) from the trapezoidal wave forming circuit 20 obtained in the same manner as in the past, and calculates the phase difference according to the phase difference between them. While supplying the phase error voltage to the discrete control system 7, in this embodiment, the voltage controlled oscillator (VCO) 21
is applied as a control voltage to the output oscillation frequency (7 to 1
4MHZ).

The output signal frequency of the VC021 changes according to the rotational phase of the rotary drum 9 (this is also the rotational phase of the rotary heads 10a, 10b), and is converted into a clock pulse by the clock pulse generation circuit 22 and applied to the variable delay circuit 13. The delay time is varied.

Therefore, the color video signal supplied from the input terminal 12 to the variable delay circuit 13 is delayed in accordance with the rotational phase error of the rotary drum 9. The color video signal delayed by the variable delay circuit 13 is applied to the rotary heads 10a, 10b via a well-known video signal recording system. That is, the delayed color video signal is
3, the carrier color signal is separated and taken out, and this carrier color signal passes through an ACC circuit 24 and a color signal processing circuit 25, and is frequency-converted to a frequency lower than that of a frequency-modulated luminance signal, which will be described later. The phase is advanced by 90 degrees every horizontal scanning period, and then the phase is delayed by 90 degrees every horizontal scanning period in one field period, which is alternately applied to each field, and then supplied to the low castle filter 26. Here, unnecessary frequency components are removed and the signal is supplied to a mixer 32. On the other hand, the delayed color video signal is also supplied to a low-pass filter 27, where the luminance signal is separated and extracted.

This luminance signal is sent to the pre-enhancement circuit 28, the white
The signals are supplied to the frequency modulator 30 through the dark clip circuits 29, where they are frequency modulated. This frequency modulated luminance signal is supplied to a mixer 32 after its low frequency components are removed by a high frequency filter 31, where it is frequency division multiplexed with a low frequency converted carrier color signal from a low frequency filter 26. The frequency division multiplexed signal taken out from the mixer 32 passes through the recording amplifier 33, and is alternately applied to one track per field by the rotary heads 10a and 100, which have different azimuth angles. ) A magnetic tape 3 is made to run at a constant speed by
4 and are sequentially recorded. Figure 3 shows magnetic tape 3
4 is a diagram showing an example of the above track pattern,
2 and t3 are tracks on which one field of the frequency division multiplexed signal is recorded, and 35 is one of the rotary heads 10a or 10b which scans in the direction of arrow 36. Further, the solid line portions of each track t, , , , etc. indicate the horizontal synchronizing signal position. By the way, according to this embodiment, as described above, the color video signal to be recorded is transferred to the rotating drum 9.
However, in a conventional recording system that does not have this variable delay circuit 13, the rotation of the rotary drum 9 may be delayed due to some disturbance while the magnetic tape 34 is running when recording track t3, for example. Assuming that the speed has decreased, the horizontal synchronization signal that should originally be recorded at the position 37 on track t3 shown in FIG. 3 is shifted to the position shown in FIG. It is recorded at the position indicated by the broken line 38.

However, according to this embodiment, the output phase error voltage of the phase comparator 4 increases in response to the drift of the rotating drum 9, and the frequency signal that decreases in inverse proportion to this increase is reduced to VC0.
21, the signal is supplied to the variable delay circuit 13 via the clock pulse generation circuit 22. Therefore, since the frequency of the clock pulse is lower than that in the steady state, the transfer time of the variable delay circuit 13 composed of a CCD becomes longer, and the delay time becomes longer. Therefore, the color video signal is delayed by the variable delay circuit 13 longer than in the steady state by a time corresponding to the drift of the rotating drum 9,
The horizontal synchronization signal is recorded at the position 37 where it should originally be recorded. Similarly, when the rotational speed of the rotating drum 9 increases due to disturbance than the steady speed, the variable delay circuit 1
The delay time of 3 is controlled to be shorter than that in the steady state, and the horizontal synchronizing signal is recorded at the position where it should originally be recorded. In this way, the rotational phase error of the rotary drum 9 caused by the disturbance is canceled out by controlling the delay time of the variable delay circuit 13, and the recording position of the horizontal synchronization signal with the adjacent track is aligned in a fixed direction with accuracy. A line-up with the highest number of days is held.
When the magnetic tape 34 recorded in this manner is reproduced, crosstalk components from adjacent tracks can be reduced compared to the conventional method, and a reproduced image with good S/N ratio can be obtained. In particular, alignment accuracy is required. This method is suitable for application to a long-time video signal recording method. Next, a second embodiment of the video signal recording method according to the present invention will be described with reference to the block diagram shown in FIG.

In the figure, the same components as those in FIG. 2 are denoted by the same reference numerals, and the explanation thereof will be omitted. In this embodiment, dedicated variable delay circuits are provided for the luminance signal transmission system and the carrier color signal transmission system, respectively. That is, the output signal of the VC021 is converted into a clock pulse by the clock pulse generation circuit 39 and then applied to the variable delay circuit 40 that delays the luminance signal, and the delay time is variably controlled according to the rotational phase error of the rotary drum 9. , the output signal of VC021 is divided into 1/1 by the 1'n frequency divider 41.
n frequency divider (n is an integer) and clock pulse generation circuit 4
2, which is converted into a clock pulse with a frequency of 1/n of the output clock pulse frequency of the clock pulse generation circuit 39, and applied to the variable delay circuit 43 that delays the low frequency conversion carrier color signal, and the delay time is Variable control is performed according to the rotational phase error of the rotating drum 9. Here, the variable delay circuits 40 and 43 are composed of CCDs, for example, and if the number of stages of the variable delay circuit 40 is X stages, the variable delay circuit 4
The number of stages of 3 is set to X/~.

The reason why the number of stages is made different in this way is to take into consideration the difference in band width between the luminance signal and the low-frequency conversion carrier chrominance signal, as well as the cost. The castle width should be 1/2 of that. Furthermore, the number of stages in the variable delay circuit 43 is determined because the input signal is a low frequency conversion carrier chrominance signal having a narrower bandwidth than the luminance signal.
There is no need to use the same one as X/N, which is cheaper
It has been confirmed that the bandwidth of the variable delay circuit 40 can be 1/9 of that of the variable delay circuit 40. however,
Since the delay times of the variable delay circuits 40 and 43 must be the same, the clock pulse frequency of the variable delay circuit 43 is 1/1/1 of the clock pulse frequency of the variable delay circuit 40.
It is set to n. In this way, the luminance signal and the low frequency conversion carrier chrominance signal are each delayed in response to the rotational phase error of the rotating drum 9 so that the error becomes zero, and then the luminance signal is frequency modulated. Both are frequency-division multiplexed and recorded on the magnetic tape 34 with high precision in date alignment.

- In the case of the first embodiment, the entire color video signal is delayed, so the circuit configuration is simple, whereas according to the present embodiment, the luminance signal and the low-frequency conversion carrier color signal are each delayed. Since the delay is caused by dedicated variable delay circuits 40 and 43, it is possible to arrange the date with higher accuracy. Note that in the present invention, the variable delay circuits 13, 40,
The delay time control 43 is performed based on the signal that detects the rotational phase error of the rotary heads 10a and 10b. Therefore, if this rotational phase error can be detected, the phase control of the rotary drum servo system as in each of the above embodiments is performed. It is not necessary to use the method of sharing the output signal of the phase comparator 4 used in the system, and other methods may be used.

In addition, although the variable delay circuits 13, 40, and 43 were constructed using CCDs, they were constructed using bucket pegged devices (BBDs).
) or other variable delay elements having similar functions. As described above, the video signal recording method according to the present invention includes a variable delay circuit that delays the video signal to be recorded, and a signal obtained by detecting the rotational phase error of the rotary head to determine the delay time of the variable delay circuit. , and a circuit for variable control so that the horizontal synchronization signal position of the video signal recorded on the track is aligned between each track by canceling the rotational phase error, so that the horizontal synchronization signal recording position on the track of the magnetic tape is adjusted. can be more accurately aligned between each track, and as a result, there is less crosstalk even in long-duration recording and playback systems with low tape speeds.
It is possible to obtain stable, high-quality images with good S/N, and the signal obtained by detecting the rotational phase error of the above-mentioned rotary head is obtained by using a phase comparator used in the phase control system of the servo system of the rotary head. Since the output phase error voltage is shared, the circuit configuration can be made simple and low-cost.Furthermore, when the video signal mentioned above is a color video signal, separate transmission systems for luminance signal and carrier color signal can be used. Since a dedicated variable delay circuit is provided for each to delay the same delay time,
It records color video signals even with extremely accurate date alignment. It has characteristics such as being able to

[Brief explanation of drawings]

Figure 1 is a block system diagram showing an example of the conventional system.
FIG. 3 is a block diagram showing a first embodiment of the method of the present invention, FIG. 3 is a track pattern diagram for explaining the operation of the method of the present invention, and FIG. 4 is a block diagram showing a second embodiment of the method of the present invention. . 4... Phase comparator, 9... Rotating drum, 10a, 10b... Rotating head, 11a, 11b
...Magnet, 12...Color video signal input terminal, 13, 40, 43...Variable delay circuit, 21...
．． Voltage controlled oscillator (VCO), 23... Bandwidth filter for carrier color signal separation, 27... Low-pass filter for luminance signal separation, 41...1/n Frequency divider. Figure 1 Figure 2 Figure 3 Figure 4

Claims (1)

[Scope of Claims] 1. A variable delay for delaying the video signal to be recorded by the rotary head in a method of recording video signals by sequentially forming tracks inclined with respect to the longitudinal direction of the magnetic tape using a rotary head. The delay time of the variable delay circuit is offset by the signal obtained by detecting the rotational phase error of the rotary head, and the horizontal synchronization signal position of the video signal recorded on the track is adjusted to each track. A video signal recording method characterized by comprising a circuit for variable control so that the signals are aligned between the two. 2. A patent claim characterized in that an output phase error voltage of a phase comparator used in a phase control system of a servo system of the rotary head is shared as a signal obtained by detecting a rotational phase error of the rotary head. The video signal recording method according to item 1.