JPH02124693A - Color video signal recorder - Google Patents

Abstract

PURPOSE:To obtain a beat signal with excellent S/N at reproduction by applying 1/4 offset to a frequency of a pilot signal with respect to a horizontal frequency and applying 1/2 offset to a frequency of a beat signal with respect to the horizontal frequency. CONSTITUTION:Frequencies f1-f4 of a pilot signal are selected so as to have 1/4 offset with respect to an integral number of multiple nfh of the horizontal frequency, and a frequency of a beat signal is selected so as to have 1/2 offset. A tracking error is detected based m on a level of a beat signal of frequencies (1/2fh and 3/2fh) between a pilot signal of an object track and a pilot signal from both adjacent tracks at the reproduction side, the capstan servo system or the piezoelectric element of a moving head is controlled by the error to apply tracking control. Thus, the S/N of the heat signal is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a color video signal recording device that records pilot signals of four different frequencies for tracking purposes.

[Summary of the invention]

In this invention, pilot signals each having four frequencies are recorded, and during playback, tracking is performed from the beat signal level of the pilot signal recorded on the target track and the pilot signals recorded on both adjacent tracks. In a color video signal recording device that performs control and does not have a low frequency conversion color signal, the frequency of the pilot signal is relative to the horizontal frequency fh.
The frequency of the above-mentioned beat signal is offset by η with respect to the horizontal frequency fh, so that a beat signal with good S/N can be obtained during playback, and the frequency of the pilot signal generated in the electromagnetic conversion system is 2 It is possible to prevent the doubled frequency component from having an adverse effect on the original signal.

[Conventional technology]

As a conventional rotary head type VTR, AT F is used so that the scanning trajectory of the rotary head and the track during playback match
(Automatic 1'rack Finding
) is known in which a pilot signal for a recording medium is superimposed on a recording signal and recorded.

Different frequencies fl, f2 . f3. f4(fl<f
Four pilot signals, 2<[3<f4), are sequentially recorded on each track. During playback, accurate tracking is achieved by detecting the level of a beat signal generated between the pilot signal of the target track and the pilot signals of adjacent tracks before and after, and comparing the detected levels. For example, a pilot signal of frequency f2 is recorded on the target track, and frequencies 11 and f3 are recorded on the tracks before and after it.
When the pilot signal of (ra-f
Tracking control is performed so that the levels of the beat signal at frequency 2) and the beat signal at frequency (f2-fl) are equal.

In the conventional V'I''R, the carrier color signal is frequency-converted to the lower frequency side, and the low-frequency converted color signal is recorded on the magnetic tape together with the FM-modulated luminance signal.

As the low carrier frequency fc of the color signal, N T S C
In the case of the PAL system, a frequency with an offset of '/4th is selected with respect to the horizontal frequency fh, and in the case of the PAL system,
A frequency with an offset of 1/8 fh is chosen.

Therefore, in the case of the NTSC system, as shown in FIG. 2A, for an integral multiple of the horizontal frequency nfh, (nfh+/
.
A spectrum of the low-frequency conversion color signal shown by a broken line exists at a position of I:l/8 fh).

The frequency of the pilot signal for tracking in V'I'H is selected so as to satisfy the following conditions.

First, the frequency difference between the pilot signals of both adjacent tracks is fh and a3rh. That is, fl 1, f
2 (=f1+fh), [3(=fil-4rh)
, f 4 (-f 1 +3 fh ) (7) Relation Nial, : and.

Second, it was necessary that the frequency f1 did not match an integer multiple of the horizontal frequency nfh.

Furthermore, in order to prevent interference with the low-frequency conversion color signal, thirdly, the highest frequency f3 (-f 1+4 fh
) is approximately 50Q kHz lower than the low carrier frequency fc.

Fourth, the frequencies f1 to f4 of the pilot signal are interleaved with the low carrier frequency fc.

was necessary.

The frequency of the pilot signal is constrained by the above conditions, and in reality, as (f 1 = 6.5 rh ),
(m+′Afh) ・The frequency of fh is used.

When recording and reproducing frequency-multiplexed FM modulated luminance signals, low-frequency conversion color signals, and pilot signals, odd-order distortion always occurs in the electromagnetic conversion system, and (fy±2fp) and (f
c±2 fp ) (fy': FM modulation carrier wave, f
p: Frequency of pilot signal, i.e. fl, f2, f
3 or f4), an unnecessary signal=5 component is generated. As mentioned above, (fp −(m×ηf
h) ・fh) Therefore, 2fp is an integer multiple of the horizontal frequency Brh), and from fy and fc, respectively i! , f
This is the spectrum at a position h away. Therefore, this unnecessary signal component has a frequency of βfh when the FM modulated luminance signal is demodulated and when the low frequency conversion color signal is frequency converted, and cannot be removed by a comb filter. Therefore, the recording level of the pilot signal has to be lower than that of the low frequency conversion color signal and the FM modulation luminance signal.

On the other hand, when separating the beat signals of pilot signals to detect tracking errors, horizontal frequency components and their harmonics generated in the VTR circuit system, monitor, etc.
There was a problem in that the S/N of the beat signal deteriorated due to unnecessary radiation.

[Problem to be solved by the invention]

High-definition broadcasting has been proposed as a new television system.・As a transmission method for high-definition broadcasting, for example, Japanese Patent Application Laid-Open No. 60-86994 describes M
US E (multiple 5ub-Nyqu
ist sampling encoding) method is disclosed. The MUSE signal is a signal obtained by band-compressing and time-division multiplexing a luminance signal and a chrominance signal. In addition, as a transmission method for high-definition broadcasting, Mt.
Methods other than JSE have also been proposed.

Unlike the composite color video signals of the NTSC or PAL systems, the transmission signals of these high-definition broadcasts do not have low-frequency conversion color signals, and the luminance signals and color signals are not frequency multiplexed but time axis multiplexed. It's multiplexed. In order to record and reproduce this transmission signal, the transmission signal is FM modulated and recorded and reproduced without performing Y/C separation of the transmission signal. Tracking control using pilot signals of four frequencies can also be applied to such a rotating head type VTR. In this case, a pilot signal of the same frequency as the conventional one can be used.

However, as mentioned above, the S/N of the beat signal component of the pilot signal deteriorates due to the horizontal frequency and its harmonic components,
In addition, since the unnecessary signal component (beat component) of the pilot signal generated in the magnetic recording/reproducing system is an integral multiple of the horizontal frequency, it is necessary to lower the level of the pilot signal.
Also from this point of view, there was a problem that the S/N of the pilot signal deteriorated.

Therefore, an object of the present invention is to have no low-frequency conversion color signal;
It is an object of the present invention to provide a color video signal recording device suitable for application to a color video signal in which a luminance signal and a color signal are time-division multiplexed.

[Means to solve the problem]

In this invention, the first, second,
In a color video signal recording and reproducing apparatus in which pilot signals of third and fourth frequencies are sequentially recorded for each track and tracking is performed based on the reproduced output of the pilot signals, the first, second and third and fourth frequency f1
, f2, f3, f4 are respectively X with respect to the horizontal frequency fh.
The beat frequency of the pilot signal between adjacent tracks is selected to be offset by X with respect to the horizontal frequency fh.

[Effect]

If the frequency of the pilot signal is X with respect to the horizontal frequency fh
Since it has an offset, the frequency of the beat signal becomes 'Afh
, 3/2 fh, which is an interleaved version of fh. Therefore, even if fh and its harmonic components are mixed in from a monitor or the like, the beat signal can be separated by the comb filter, and the S/N ratio of the beat signal can be improved. In addition, the frequency component twice the frequency of the pilot signal, which occurs due to distortion in the electromagnetic conversion system, is interleaved with respect to fh, and can be removed with a comb filter, preventing an adverse effect on the original signal. .

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, l is an input terminal to which, for example, a MUSE signal is supplied. The M[JSE signal is a signal obtained by time-division multiplexing of a band-compressed high-definition broadcast brightness signal and color signal. Furthermore, the MUSE signal includes audio information, control information, a positive horizontal synchronization signal, frame pulses, etc., and one frame has 1125 lines.
The l line has 480 samples.

The MUSE signal is supplied to the video signal processing circuit 2. The video signal processing circuit 2 performs processing such as time-base compression of the MUSE signal and addition of a negative polarity synchronization signal. The output signal of the video signal processing circuit 2 is supplied to the FM modulation circuit 3. The output signal of the FM modulation circuit 3 is sent to the equalizer circuit 4.
The signal is supplied to the adder circuit 5 via the adder circuit 5. ATF with adder circuit 5
The output signal of the adder circuit 5 is supplied to a rotary head 7 via a recording amplifier 6 and a rotary transformer (not shown), and recorded as a diagonal track on the magnetic tape.

The MUSE signal from the input terminal 1 is supplied to the synchronization signal detection circuit 8, and the detected synchronization signal (frame pulse) is supplied to the control signal generation circuit 9 and taken out to the output terminal 10. The synchronization signal taken out to the output terminal 10 is used as a reference signal for the drum servo system. The control signal generation circuit 9 generates a control signal synchronized with the rotation of the rotary head.

This control signal is a signal for sequentially switching the switch circuit 15.

11.12.13.14 are frequencies fl, f2, f3,
An oscillation circuit for generating an f4 pilot signal is shown. Output signals from these oscillation circuits 11 to 14 are supplied to a switch circuit 15. The pilot signal selected by the switch circuit 15 is supplied to the adding circuit 5 and added to the recording signal. The switch circuit 15 sequentially records pilot signals of frequencies f1 to f4 on the magnetic tape for each track.

Additionally, a rotary head mechanism that uses two rotary heads arranged at 180° intervals or four rotary heads arranged at 90° intervals, and a rotary head mechanism that uses multiple rotary heads that simultaneously scan the magnetic tape. The present invention can be applied to such cases.

The frequencies f1 to f4 of the pilot signal are as follows:
It is selected so that it has an offset of X and the frequency of the beat signal has an offset of % for an integer multiple of the horizontal frequency nfh.

f 1 =n-rh +'/a fh f 2=n -fh -%fh f 3= (n+1) ・fh +'/4fhf 4
= (n+1) ・fh +3/4 fh On the playback side, the tracking error is calculated from the level of the beat signal of the following frequencies ('Afh and 3/2fh) between the pilot signal of the target track and the pilot signals from both adjacent tracks. A detection is made.

This error causes the capstan servo system to be controlled,
Tracking control is performed by controlling the piezoelectric element of the movable head.

fl-f21=%fh f2-f3-1=3/2 fh f3-f41=ηfh f4-f11=3/2 fh As for the values of frequencies f1 to f4, the beat frequency meets the above-mentioned conditions. Or f1-f21=l f3-f41=3/2 fhf2
-f31=l f4-fl If l='Afh is satisfied,
fl itself is (nfh+y4fh) and (n'fh
%fh) may be used.

Furthermore, the beat frequencies are (3/2fh) and (9/2fh), respectively.
fh) may be selected.

〔Effect of the invention〕

According to this invention, the beat frequency of the pilot signal is interleaved with integral multiples of the horizontal frequency.

Therefore, even if there is a component of the horizontal frequency fh and its harmonics from the monitor, other circuits, etc., the beat signal can be separated by the comb filter, and the S/N ratio of the beat signal can be improved. In addition, in this invention, since the frequency fp of the pilot signal has a offset, the unnecessary signal component 2fp generated in the electromagnetic conversion system becomes interleaved with respect to the horizontal frequency, and can be easily removed with a comb filter. It is possible to prevent an adverse effect on the original signal.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the present invention, and FIG. 2 is a frequency spectrum diagram of a color video signal. Explanation of main symbols in the drawings 7: Rotating head, 11.12.13.14: Oscillation circuit that generates a pilot signal for ATF. to

Claims (1)

[Claims] Pilot signals of first, second, third and fourth frequencies are sequentially recorded for each track without having a low frequency conversion color signal,
In the color video signal recording and reproducing apparatus that performs tracking based on the reproduced output of the pilot signal, the first, second, third and fourth frequencies are each offset by 1/4 with respect to the horizontal frequency fh. A color video signal recording apparatus characterized in that the beat frequency of the pilot signal between adjacent tracks is selected to be offset by 1/2 with respect to the horizontal frequency fh.