JPH06153154A - Video signal processing unit for vtr - Google Patents

Abstract

PURPOSE:To make noise unremarkable and to observe a stable picture continuously by outputting selectively either a luminance signal or a blanking signal with an output signal of a specified signal. CONSTITUTION:A blanking signal generator 11 outputs a black level signal to mask noise at a head changeover point by adjusting a level of an HD (horizontal synchronizing) signal based on the HD signal from an HD generator 7. An analog switch 12 receives a Y signal outputted from a luminance signal processing circuit 3 and a blanking signal outputted from the blanking signal generator 11 and the Y signal or the blanking signal is switched over by a masking control signal outputted from a gate circuit 10 of a specification circuit 21. That is, when the masking control signal is at an L level, the Y signal is outputted and when the control signal is at an H level, the blanking signal is outputted through the switching of the analog switch 12.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video signal processing device of a VTR which adopts a rotary scanning two-head head scan method.

[0002]

2. Description of the Related Art Generally, a VTR (Video Tape Recorder)
Then, recording of video signals (hereinafter referred to as video signals)
Many of the reproduction systems adopt a rotary scan system with a rotating two-head system. Normally, in this helical scan system, two video heads are provided on the rotary drum at intervals of 180 °, so that a video signal is recorded on a video track every half rotation of one rotation of the rotary drum.

In a video camera integrated type VTR adopting the helical scan system, for example, at least two video heads H1'.H are provided as shown in FIG.
2 ', rotary transformer 21, head amplifier 22, luminance signal processing circuit 23, color signal processing circuit (chroma signal processing circuit) 24, mixing circuit 26, viewfinder unit (hereinafter simply referred to as VF unit) 27 A processing device is provided.

The reproduction processing of the video signal in the video signal processing device of the VTR will be described below with reference to FIG.

First, tracks of one field are alternately traced by the video heads H1 'and H2', and a video signal which is a magnetic recording signal is converted into a reproduction signal which is an electric recording signal through the rotary transformer 21. This reproduced signal is amplified by the head amplifier 22 and is corrected so as to have a flat frequency characteristic from a low band to a high band.
Further, in the head amplifier 22, the video head H output from the control circuit 25 including a servo circuit and the like.
A reproduction signal is output as one continuous video signal in response to a switching signal of 1 ′ · H2 ′ (Head Switching Palus: hereinafter referred to as H-SW-P).

Next, when the reproduced signal is input to the luminance signal processing circuit 23 and the chroma signal processing circuit 24, the luminance signal (Y signal) is output from the luminance signal processing circuit 23 and the chroma signal processing circuit 24 is input. Outputs a color signal (C signal). Of these signals, the Y signal is mixed with the C signal by the mixing circuit 26 and video-outputted as a composite video signal, while VF for monitoring the video output.
It is designed to be output to the unit 27. At this time, since only the Y signal is input to the VF unit 27, a black and white image is formed, but it is also possible to form a color image by using a composite video signal.

By the way, in the helical scan method, one field and one track recording is performed for one video head, and a reproduced signal is generated by switching the signals of the head H1 'and the head H2' and connecting them in order. There is. In such a reproduction signal, the joint noise at the head switching point becomes conspicuous during reproduction, and therefore the head switching point is usually adjusted so as to be close to the vertical synchronizing signal (V.SYNC) of the video signal, and the noise portion is displayed on the screen. It is designed to be fixed on the lower side.

Further, since the tape is wound around the rotary drum for more than half a round, the video signals are recorded by the respective video heads H1 'and H2' so as to overlap in the vicinity of the joint. For this reason, it is possible to eliminate signal loss at the joints of the reproduction screens during reproduction.

The above head switching point is standardized, and in the 8 m / m format, V. 6H ± 1.5H from SYNC leading edge, V.S. SYNC
It is determined to be 5-8H from the leading edge.

[0010]

However, since the joint at the head switching point is adjusted so that it is located at the bottom of the playback screen, the noise itself does not disappear. If the display rate is about 95%, the noise at the joint is not noticeable, but if the image display rate is close to 100%, such as a VF unit, white dropout-like noise is visible at the head switching point and is stable. There is a problem that you cannot see the video that you made.

Therefore, the present invention has been made in view of the above problems, and an object thereof is to mask the noise at the head switching point so that the image display rate is 100% like that of a VF unit. It is an object of the present invention to provide a video signal processing device of a VTR that allows a stable video image to be viewed on a near reproduced image device.

[0012]

A video signal processing device for a VTR according to the present invention includes at least a head amplifier for switching a plurality of video heads to output a reproduction signal and a color signal processing circuit for processing the reproduction signal as a color signal. A luminance signal processing circuit for processing the reproduced signal as a luminance signal, and a mixing circuit for mixing the color signal and the luminance signal, wherein the luminance signal is input to the output side of the luminance signal processing circuit, A horizontal synchronizing signal generating circuit for outputting a synchronizing signal, a blanking signal generating means for outputting a blanking signal based on the horizontal synchronizing signal, and a number H before and after the video head switching point are similarly set based on the horizontal synchronizing signal. A regulating means for outputting a regulating signal is provided, and the luminance signal and the blanking signal are switched and output by the output signal of the regulating means. And it is characterized in and.

[0013]

With the above structure, the horizontal synchronizing signal generating circuit for inputting the luminance signal and outputting the horizontal synchronizing signal is provided on the output side of the luminance signal processing circuit to adjust the signal of the horizontal synchronizing signal generating circuit. It is possible to generate a black level blanking signal, and noise can be masked by outputting the black level blanking signal in synchronization with white noise at the head switching point. Further, the blanking signal is provided as the defining signal for defining the mask section at the head switching point by providing the defining means for outputting the signal for defining the number H before and after the video head switching point by the horizontal synchronizing signal. It is possible to switch between outputting the luminance signal and outputting the luminance signal with good timing. Therefore, the white noise portion at the head switching point can be masked with the black level blanking signal in good timing, so that it is possible to continuously view a stable image with no noise in a viewfinder having a high image display rate. it can.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The following will describe one embodiment of the present invention with reference to FIGS.

As shown in FIG. 1, the video signal processing device of the VTR according to the present embodiment includes at least two video heads H1 and H2 which alternately trace at least one field track of a magnetic tape as a recording medium. A rotary transformer (hereinafter referred to as RT) 1 for converting a magnetic signal traced by the video heads H1 and H2 into a reproduction signal which is an electric recording signal, and a head amplifier 2 for amplifying the reproduction signal from the RT1. A luminance signal processing circuit 3 for creating a luminance signal from the reproduced signal, a chroma signal processing circuit 4 as a color signal processing circuit for similarly producing a color signal from the reproduced signal, and a switch for switching the outputs of the video heads H1 and H2. Head switching signal (hereinafter H / SW / P
(Referred to as a) and a mixing circuit 6 for mixing the output signal of the luminance signal processing circuit 3 and the output signal of the chroma signal processing circuit 4 and outputting as a composite video signal.

Of these, the head amplifier 2 is about 60d.
It has an amplifier gain of B, and amplifies an electric recording signal, that is, a reproduction signal taken out from a video head so as to have a flat frequency characteristic from a low range to a high range. The P is used to remove the overlapping period of the reproduced signals from the two video heads H1 and H2 and then output as one continuous reproduced video signal.

The luminance signal processing circuit 3 outputs a luminance signal (hereinafter referred to as Y signal) obtained by processing the high frequency signal extracted from the reproduction signal. As shown in FIG. 2, at least a high-pass filter (HPF) 14, a dropout compensation circuit 15, a limiter circuit 16, and an FM demodulation circuit 1 are provided.
7, a low pass filter (LPF) 18, a de-emphasis 19 and a noise canceling circuit 20.

Of these, the HPF 14 takes out a reproduction signal (FM signal) having a high frequency from the reproduction signals inputted from the head amplifier 2, and
The limiter circuit 16 prevents the inversion phenomenon of the FM signal, removes the AM component in the FM signal, and outputs it to the FM demodulation circuit 17. Then, in the FM demodulation circuit 17, the output from the limiter circuit 16 is 4.2 to 5.4 MHz (8 mm format (NTS
The FM signal of C)) is demodulated to a luminance signal of DC to 3.1 MHz. The LPF 18 removes the FM carrier component contained in the FM demodulation output of the luminance signal, and the de-emphasis 19 The high frequency component emphasized at the time of recording is attenuated and returned to the original state to improve the S / N ratio in the high frequency range. The dropout compensating circuit 15 replaces the drop noise, which is a signal loss occurring in the FM signal, with a signal before 1H by using a 1H delay line (not shown).

Next, in the noise canceling circuit 20, S /
A noise component distributed in the high frequency band of the FM signal with an improved N ratio is removed and output as a Y signal.

On the other hand, the chroma signal processing circuit 4 outputs a color signal (hereinafter referred to as C signal) obtained by processing a low frequency signal extracted from the reproduction signal. .

The Y signal and the C signal are output to the mixing circuit 6, where they are mixed with each other and output as a composite video signal, while only the Y signal is a horizontal synchronizing signal (hereinafter, referred to as a horizontal synchronizing signal). The signal is output to a viewfinder unit (VF unit) 13 via an HD switch 7 which is a horizontal synchronizing signal generating circuit for outputting an HD signal) and an analog switch 12.

Here, the HD generator 7 outputs Y inputted by comparing the phase with the horizontal synchronizing frequency clock.
While the HD signal synchronized with the horizontal sync signal of the signal is generated, the automatic frequency adjustment (AFC: Automatic Frequenc
y Control) function. Therefore, the HD signal is stably output regardless of the noise at the head switching point. And H from this HD generator 7
The D signal is output to the defining circuit 21 as a defining unit that defines the switching point of the video head, and also to the blanking signal generator 11 that generates a blanking signal (blanking signal).

Further, the regulation circuit 21 measures the number H before and after the head switching point based on the HD signal. For example, the counter A8 and the counter B9, and the head switching point based on the output signals of the counter A8 and the counter B9. The gate circuit 10 is composed of an AND or OR circuit or the like that outputs a prescribed signal before and after the number H, that is, a masking control signal.

The blanking signal generator 11 is also provided.
Based on the HD signal from the HD generator 7,
By adjusting the level of the signal, a black level signal for masking noise at the head switching point is output. That is, when the Y signal level output from the luminance signal processing circuit 3 is 1.0 V _PP, since synchronization level is 0.285V _PP, for example, when the level of the HD signal is 5V _PP, synchronization level 0.285V _A black level masking signal is output to the analog switch 12 by attenuating to _PP and inverting the polarity.

In the analog switch 12, the Y signal output from the luminance signal processing circuit 3 and the blanking signal output from the blanking signal generator 11 are input. The signal and the blanking signal are switched by a masking control signal output from the gate circuit 10. That is, as shown in FIG. 3, the analog switch 12 switches so that the Y signal is output when the masking control signal is at the L level and the blanking signal is output when the masking control signal is at the H level.

Here, a masking control signal for controlling whether to output a blanking signal for masking or a Y image signal will be described below with reference to FIGS. 1 and 3. Incidentally, the masking section at the head switching point may be ± several H and is ± 4 in this embodiment.
H is adopted, but not limited to this.

The masking control signal is shown in FIG.
As shown in FIG. 5, the output is from the defining circuit 21 including the counter A8, the counter B9, and the gate circuit 10.

Of these, the counter A8 counts + 4H from the head switching point, and by setting the pulse at the head switching point as a reset pulse, the rising or falling of the HD signal from the HD generator 7 is 4 times. It is a program timer that counts times.

The counter B9 counts 258H from the head switching point to determine -4H from the head switching point, and is a program timer that counts the HD signal 258 times. The above 258H is
Counter A8 is advanced from one field 262.5H derived from one frame 525H in the NTSC system 4
The value calculated as 258.5H by subtracting H,
In the PAL system, one frame is 625H, so NT
When calculated in the same way as the SC method, it becomes 308.5H,
The count number of the counter B9 is 308 times.

Incidentally, in the above, ± 4H with respect to the head switching point
However, this is because a signal of ± several H is generated with respect to the rising or falling of the head switching point in order to mask noise generated at the head switching point, and the present invention is not limited to this.

From the above, the masking of noise at the head switching point occurring on the reproduction screen will be described below with reference to FIGS. 1 and 3.

Normally, the reproduction signal from the head amplifier 2 is
The head switching signal is adjusted so that the head output signal is not interrupted. This head switching signal is shown in FIG.
As shown in (a), the vertical synchronizing signal (V-SYNC) is adjusted to rise at the leading edge 6H.
The head switching signal determines the HD signal as shown in FIG. 3B, and as shown in FIGS. 3C and 3D, the rising edge corresponding to the rising edge of the head switching signal in the HD signal. Or ± 4 from the fall
The counter A output signal and the counter B output signal of H are determined. The counter A output signal and the counter B output signal are, as shown in FIG. 3E, a gate circuit output signal having ± 4H at the H level by the gate circuit 10,
That is, it is output as a masking control signal. Also, this masking control signal is shown in FIG.
As shown in (g), the video signal of the Y signal is output at the L level and the black level blanking signal is output at the H level.

In this embodiment, in the defining circuit 21 as means for outputting the masking control signal,
Although a counter or the like is used, other means for outputting a masking control signal may be used, and there is no particular limitation.

From the above, the white noise component generated at the joint at the head switching point during video reproduction can be masked by outputting the blanking signal at the black level, so that the image display rate is approximately 10.
Even when viewing a 0% VTR or the like, noise becomes inconspicuous, and stable images can be continuously viewed.

In this embodiment, the image display rate is 100%.
Although a VTR viewfinder with a built-in video camera has been described, the same processing can be performed when video is output to a TV having a high image display rate.

[0036]

The video signal processing device of the VTR of the present invention comprises:
As described above, at least a head amplifier that switches a plurality of video heads to output a reproduction signal, a color signal processing circuit that processes the reproduction signal as a color signal, and a luminance signal processing circuit that processes the reproduction signal as a luminance signal. A horizontal synchronizing signal generating circuit for receiving a luminance signal and outputting a horizontal synchronizing signal on the output side of the luminance signal processing circuit, and a mixing circuit for mixing the color signal and the luminance signal. A blanking signal generating means for outputting a blanking signal on the basis of the signal and a defining means for outputting a signal for defining the number H before and after the video head switching point on the basis of the horizontal synchronizing signal are also provided. The configuration is characterized in that the luminance signal and the blanking signal are switched and output according to the output signal of the defining means.

Therefore, the white noise component generated at the joint at the head switching point during video reproduction can be masked by outputting the blanking signal at the black level, so that the image display rate is almost 100%, for example. Even when a VTR or the like is viewed, noise is less noticeable, and a stable image can be continuously viewed.

[Brief description of drawings]

FIG. 1 is a block diagram showing a video signal processing device of a VTR according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a luminance signal processing circuit in the video signal processing device of the VTR of FIG.

3 is a waveform diagram of an output signal in each circuit of FIG. 1, FIG. 3 (a) is a waveform diagram showing a head switching signal, and FIG. 3 (b) is a waveform showing an HD signal. FIG. 6C is a waveform diagram showing a counter A output signal, FIG. 7D is a waveform diagram showing a counter B output signal, and FIG. 7E is a gate circuit output. FIG. 4F is a waveform diagram showing signals, FIG. 6F is an enlarged diagram of FIG. 6E, and FIG. 6G is a waveform diagram showing an analog switch output signal.

FIG. 4 is a block diagram showing a conventional VTR video signal processing device.

[Explanation of symbols]

1 rotary transformer 2 head amplifier 3 luminance signal processing circuit 4 chroma signal processing circuit (color signal processing circuit) 5 control circuit 6 mixing circuit 7 HD generator (horizontal synchronizing signal generation circuit) 8 counter A 9 counter B 10 gate circuit 11 block Ranking signal generator (blanking signal generating means) 12 Analog switch 13 VF unit 21 Regulation circuit (regulation means)

Claims (1)

[Claims] 1. A head amplifier for switching at least a plurality of video heads to output a reproduced signal, a color signal processing circuit for processing the reproduced signal as a color signal, and a luminance signal processing circuit for processing the reproduced signal as a luminance signal. A video signal processing device for a VTR having a mixing circuit for mixing a color signal and a luminance signal, the horizontal synchronizing signal generating circuit outputting a horizontal synchronizing signal when the luminance signal is input to the output side of the luminance signal processing circuit. A blanking signal generating means for outputting a blanking signal based on the horizontal synchronizing signal, and a defining means for outputting a signal for defining the number H before and after the video head switching point based on the horizontal synchronizing signal. A video signal of a VTR, which is provided and switches between a luminance signal and a blanking signal according to the output signal of the defining means and outputs the switched signal. Processing equipment.