JPS5853812Y2 - video signal recording device - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a video signal recording/reproducing device, etc., and is an improvement of the device which adopts a method of recording a color video signal for each unit field on a unit track in an azimuth arrangement different from that of adjacent tracks. Regarding.

The so-called azimuth recording method is a recording method that substantially eliminates the need for guard bands by making the azimuth arrangement of adjacent recording tracks different, increasing the recording density and improving the envelope efficiency of recording media such as magnetic tape. On the other hand, when recording a composite color video signal such as an NTSC signal, when a so-called color subcarrier low-pass conversion recording method is adopted, it is difficult to obtain a signal that has been reduced and recorded. However, the azimuth effect is small, so the influence of crosstalk between adjacent tracks can be avoided, resulting in color signal interference, color unevenness, blurring, etc.

In order to improve such drawbacks, for example, in a VTR, when a low frequency converted color subcarrier signal is superimposed on an FM modulated luminance signal and recorded on a unit track of a recording medium such as a magnetic tape for each unit field. , color subcarrier signals every l fields, once every l horizontal scan line.
Recording is performed by changing the phase by 80 degrees and performing low frequency conversion.

The low frequency converted color subcarrier signal recorded in this way is reproduced in the normal subcarrier band (3,58MH2±0.5
In addition to re-converting to MH2), for fields that have been low-pass converted by changing the phase by 1800 for every horizontal scanning line, the playback signal is phase inverted in the opposite way to the recording time, and after being converted to continuous phase, it is passed through a comb filter. In addition, the color subcarrier signal component of the adjacent track has a phase difference of 1800 degrees for each horizontal scanning line, so they cancel each other out, and furthermore, the color subcarrier signal component of the track being scanned for reproduction is interleaved. Since the related high-frequency luminance signal also passes through the comb filter and is canceled out, the above-mentioned problem is solved to a certain extent.

However, since the high-frequency luminance signal interleaved and mixed in the color subcarrier, which is the crosstalk signal component of the liquid adjustment track, is not canceled even through the comb-shaped filter, the color reproduced from the track being scanned for reproduction is It mixes into the subcarrier signal and causes phenomena such as S/N deterioration and bead interference.

The present invention has been made in view of this point.

The details will be explained below with reference to one embodiment of the circuit as shown in FIGS. 1 and 2.

FIG. 1 shows a circuit block diagram of the main part of the recording system of the apparatus of the present invention, which is roughly divided into a luminance signal system Y and a chroma signal system C.

The chroma signal system is an NTSC signal that is applied to the input terminal ■.
Bandpass filter C frequency band example for separating color subcarrier signal S from color composite signal such as signal, 3.58
7. to M'. ±0.5MHz), a comb-shaped filter 2 that removes only high-frequency luminance components that are in an interleaving relationship with the color subcarrier signal component from the output, and a comb filter 2 that removes from the output only high-frequency luminance components that are in an interleaving relationship with the color subcarrier signal component; 1
In order to sequentially change the position of the color subcarrier to be low-frequency converted by 180 degrees in each horizontal scanning period, a frequency conversion signal having a phase difference of 1800 times is generated every horizontal scanning period in the l field. An oscillation circuit 3 that converts the output of the comb filter 2 into a low frequency range, and a low pass filter 5C that allows only the low frequency conversion output to pass.Example frequency band: 0.688MH2±0.5M
H2).

The oscillation circuit 3 has a reference oscillation frequency (for example, 4.26) selected as an odd multiple of ifH (where fH is the horizontal scanning frequency).
7919MH2), a phase conversion circuit 33 that converts the output into two outputs with a 180° phase difference, and a vertical synchronization signal fv and a horizontal synchronization signal fH in the recording signal, and combines the vertical synchronization signal fv and horizontal synchronization signal fH in the recording signal, At T□, the switching control circuit 32 enables a flip-flop circuit configured to alternately invert with the horizontal synchronization signal period and maintain only one stable or quasi-stable state during the other one field period T2. The two phase-inverted outputs of the phase conversion circuit 33 are combined to form a field-equivalent signal consisting of a signal in a field-equivalent period T2, which is fixed to one of the phases, and a signal whose phase is inverted every horizontal scanning period. A circuit including a switching circuit that switches and selects signals such that the signal in section T1 is an alternating signal for each -field may be used.

tl, t2/I'i, the switching control circuit 32
shows the output of

The luminance signal system includes a low-pass filter 1 that removes unnecessary high-frequency components in the luminance signal, and an FM filter after controlling the output AGC and performing processing such as clamping and white clipping.
It is composed of an FM conversion circuit 12 that allows a multivibrator type modulator to perform modulation.

With such a configuration, only the color subcarrier signal obtained by removing the interleaved high-frequency luminance component from the high-frequency signal component separated by the band-pass filter 1 through the comb filter 2 is transmitted to the next stage with low frequency. After being converted to a low frequency signal by the conversion circuit 4, it is passed through the low-pass filter 5, superimposed on the output of the FM modulation range 12, and then azimuthally recorded.
Even if low-frequency converted color subcarrier signal components are mixed in due to crosstalk between adjacent tracks during playback, the luminance signal components that are already in an interleaved relationship are removed from these signals, so the above-mentioned crosstalk will not occur. The talk time is
As is well known, the beat disturbance caused by crosstalk components can be completely removed by passing through another comb-shaped filter inserted in the reproduction path or the above-mentioned comb-shaped filter which is switched and shared during reproduction. It is possible to remove moiré phenomena caused by

However, as will be described in detail later with reference to FIG. 2, even in the case of a reproduction chroma signal system, the comb filter 102 is essential in order to eliminate the influence of crosstalk between adjacent tracks.

Therefore, in such a device, the chroma signal is delayed by a total of 2H during recording and playback, and the 3H chroma signal in total, that is, the color subcarrier signal with a 2H delay with respect to the luminance signal, is mixed with the luminance signal. , and will be reproduced on a color receiver, resulting in vertical color blurring.

Furthermore, if the source of the recording signal is the output of another VTR of the same type, the chroma signal delayed by a total of 4H with respect to the luminance signal will be reproduced, and the deterioration of image quality due to the above-mentioned color shift will be significant. Become.

Also, as a recording signal source, only the chroma signal system can be used.
A similar reduction in image quality is inevitable when using a single-tube color camera with a built-in comb-type filter, etc. equipped with a delay line of be done.

In consideration of this point, in the case of the apparatus of the present invention, in addition to the above-described configuration of the recording system, a configuration is adopted in the reproduction system in which only the luminance signal is always IH delayed with respect to the ROMA signal.

The main structure of the reproduction system will be explained below with reference to FIG.

The playback output that passes through the preamplifier (equalizer, etc.) 110 is
A frequency conversion circuit 1 for inverse conversion via a low-pass filter 01 that allows only low-pass conversion chroma subcarrier components to pass.
Added to 03.

Therefore, it is inversely converted by an operation substantially in phase reversal to that of the recording system, and is further passed through the comb filter 02 to remove the crosstalk of the color subcarrier signal component of the adjacent channel as described above, and then FM demodulated. The signal is mixed with the luminance signal and amplified as an NTSC signal.

The inverse conversion operation will be briefly explained below.

A burst gate 10 is connected to the output of the comb filter 02.
The burst signal extracted by 4 is used for two purposes.

One is to change the phase of the color subcarrier signal for each horizontal scanning line by 1800 degrees during recording, and restore the phase of the field signal that was low-pass converted. 180 signals per horizontal scan line
In order to perform the inverse conversion operation with the 0 phase changed, a flip-flop controller is used to control the switcher 130 that supplies the frequency conversion circuit 103 with a frequency conversion signal with a different phase of 1800 for each horizontal scanning line. The purpose of this method is to maintain normal operation of the burst circuit 132, and utilizes the fact that when the operation of the circuit is reversed, the phase of the burst signal is inverted every horizontal scanning line.

That is, when the ID circuit 105 detects a large phase shift with respect to the reference oscillation circuit 106, the output triggers the flip-flop circuit 132 to return its operation to normal.

One purpose is to control the phase comparison circuit 107 and the voltage variable oscillator 108 (oscillation frequency fv co == 3.58M
Hz-, fH) as a comparison signal source for an APC loop.

This APC circuit eliminates phase fluctuations with respect to fH and allows AFC to use output multiplied by 44 times the horizontal oscillation frequency fH.
Together with the loop, the jitter component of the reproduced signal is removed.

The frequency conversion circuit 109 is provided for this purpose, and the frequency relationship is as shown in FIG.

The configuration around the switcher 130 is the same as that of the recording system, so a description thereof will be omitted.

A part of the output of the preamplifier 110 is applied to an IH delay line 113 via a bypass filter 111 and a limiter 112, and further passes through a limiter amplifier 114, and then demodulated by an FM demodulation circuit 115, resulting in an inversely converted color subcarrier signal. mixed with

The 1H delay line delays only the luminance signal and mixes it with the chroma signal as a relatively original signal and the 2H signal at the center of the 3H chroma signal, so there is almost no color shift on the reproduced screen. It's not a problem.

FIG. 3 shows a block diagram of the relevant portion when the IH delay line 113 is also used as a delay line for dropout compensation.

The difference from the conventional dropout compensation circuit is that the playback FM
A signal normally passes through the IH delay line 201, and when a dropout is detected during the IH delay output by the dropout detection circuit 203 that performs envelope detection of the signal passing through the delay line and limiter 202, a certain amount of The point is that the output of the Schmitt circuit 204, which operates with hysteresis characteristics, is replaced with the FM signal coming via the direct line 205.

With such a configuration, if a sufficient band cannot be secured depending on the characteristics of the lH delay line 201, the multiplier circuit 211
The FM signal may be frequency-multiplied and delayed according to the FM signal, and the delayed output may be down-downed again (down-down circuit 212) and applied to the switching circuit 206.

Although it is basically possible to prevent color shift with this configuration, as mentioned above, if the recording signal source is another home-use VTRC dubbing) or a single-tube color camera, If the band of the luminance signal is limited, it is better to transmit the high frequency signal to the chroma signal during recording without passing it through a comb filter.

Hereinafter, such an embodiment will be explained with reference to the main circuit example shown in FIG.

This figure shows a circuit around a recording chroma system comb-shaped filter.

This m filter 300 includes a common emitter type drive transistor 301 and an IH delay line 30 whose output is input.
2 and a mixing circuit 304 for adding and subtracting the output and the video signal supplied via the direct line 303.
Consists of.

The color subcarrier signal is output as a subtraction output from a terminal 305 of the bridge circuit forming the mixing circuit 304, and is applied to a bandpass filter 308 via an analog switch 306 and a direct-coupled two-stage amplifier 307.
After passing through the C circuit, it is supplied to the frequency conversion circuit 4 shown in FIG.

The luminance signal is output as an addition signal from the terminal 309 of the bridge circuit, and is applied to the low-pass filter 11 in FIG. 1 via the two-stage directly connected amplifier 310.

The output of the direct-coupled two-stage amplifier 310 is applied via a bypass filter HPF and an amplifier to an amplitude detection circuit 311 having a detection time constant of several seconds or more, and the presence or absence of a high-frequency luminance component is detected.

The detection output triggers the Schmitt circuit 312 after DC amplification, and if a high-frequency luminance signal is present, it is sent to the gold contact side of the analog switch 306, even though it is at a low level.
If it does not exist at all, switch to the ■ side to prevent unnecessary delay of the chroma signal.

If the band of the luminance signal in the recording signal is known in advance, a switch 320 can be provided to cut off the input to the IH delay line 302 in conjunction with the recording changeover switch (see FIG. 5). In the embodiment, by changing the emitter potential of the drive transistor 301, the drive transistor 30
1 is completely inactive.

That is, when recording a video signal without high-frequency luminance components, a positive potential is applied to the emitter 330 of the transistor via a resistor 331, a diode 332, and a switch 333.

Since the present invention has the above-mentioned configuration, it can be applied to an apparatus that uses the azimuth recording method to record by converting the color subcarrier to a low frequency band without providing a guard band between adjacent tracks. It is possible to remove the influence of crosstalk components of range conversion color subcarriers, and in this case, the deterioration of S/N due to the influence of high-frequency luminance components that may be interleaved and mixed without causing any color shift.
Phenomena such as beat disturbance can be prevented, and the influence of the absence of high-frequency luminance components can also be eliminated.

[Brief explanation of the drawing]

The drawings are all related to the present invention; Fig. 1 is a block diagram of the main circuit of the recording system, Fig. 2 is a block diagram of the main circuit of the reproduction system, and Fig. 3 is the main circuit of the dropout compensation circuit. The block diagram, FIG. 4, is a circuit diagram around the comb filter, and FIGS. 5 and 6 are examples of circuits having different circumferences of the comb filter. 2.102,300...Comb filter, 4゜1
03... Frequency conversion circuit, 113, 302...
...IH delay line.

Claims (1)

[Scope of utility model registration request] When a color video signal is recorded on a unit track for each unit field in a video signal recording device in an azimuth arrangement different from that of adjacent tracks, the luminance in a high frequency signal component including a subcarrier component separated from the video signal is calculated. Only when the signal exceeds a certain level, the high-frequency signal is passed through a comb-type filter to remove only the color subcarrier component, which removes the high-frequency luminance component that has an interleaf relationship with the subcarrier component. The low frequency of the FM brightness modulation signal in the video signal is converted so that the phase order of the signal for each horizontal scanning section of the low frequency conversion color subcarrier corresponding to the L field is different from that of the adjacent track. A video signal recording device configured to record in a superimposed manner on a signal.