JPH0210992A - Video signal recording and reproducing device - Google Patents

Abstract

PURPOSE:To attain broad band of a luminance signal without picture deterioration in a chrominance signal by mixing a reproduced chrominance carrier signal after applying time base correction of a reproduced luminance signal subjected to FM demodulation at the reproduction. CONSTITUTION:A time base correction circuit 24 is added in a conventional VTR recording reproducing system. A horizontal synchronizing signal is separated from a luminance signal inputted to a terminal 25 of the circuit 24 via a variable delay line 26 and a horizontal synchronizing separator circuit 27. The signal is inputted to a phase comparator 29 together with a reference horizontal synchronizing signal synchronously with the burst frequency of a reproduced color signal inputted from a terminal 28. A delay control circuit 29 is controlled by a detection signal of the comparator 29 and the phase of the horizontal synchronizing of the output of the delay line 26 is made coincident with a reference horizontal synchronizing signal. As a result, the deviation of the horizontal synchronization and the deviation of phase shift are eliminated. In this case, the color signal eliminated from the time axis fluctuation is mixed with the said luminance signal by an adder 23. Thus, the time base fluctuation of the residual color signal in the luminance signal is avoided.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a video signal recording and reproducing device, and a video signal that separates and records a composite video signal in which a luminance signal and a chrominance signal are mixed into a luminance signal and a chrominance signal. Concerning improvements in recording and reproducing measures.

[Conventional technology]

Although this invention can be widely applied to video equipment,
In the following, a magnetic recording/reproducing device (VTR) will be explained as an example.

In a conventional VTR, for example, when recording an NTSC signal separately into a luminance signal and a chrominance signal, a luminance/chrominance signal separation circuit is required, but the luminance signal band to be recorded is the chrominance signal band3. If the frequency is narrower than 58 MH2±500 KHz, that is, about 3 MHz, even if the luminance and chrominance signals are recorded separately, reproduced, and then mixed, the luminance signal and the chrominance signal are unlikely to interfere with each other.

However, when the luminance signal band includes the chrominance signal band, the residual chrominance signal component included in the luminance signal interferes with the chrominance signal component during reproduction, greatly degrading the image quality.

As a method for reducing the interference between the residual color signal and the color signal component due to the broadbandization of the luminance signal as described above, luminance/chrominance signal separation (hereinafter referred to as Y/C separation) using a rectangular filter is performed.

Figure 6 shows, for example, VTR service manual HV-901.
(This is a block diagram of a conventional VTR shown in F&I. Also, FIG. 7 is an explanatory diagram of the operation of FIG. 6.

In Fig. 6, a composite video signal in which a luminance signal and a color signal shown in Fig. 7 fa) are mixed is input to terminal 1, and LH (
H is one horizontal period) is led to delay line 2. If the input video signal has a correlation in the vertical direction of the receiver screen, the IH delay line 2 output signal will have almost the same waveform for the luminance signal as shown in Figure 7 (bl), and the signal phase for the color signal will be the same. Therefore, when the terminal 1 human input signal and the IH delay line 2 output signal are added by the adder 3, the color signal component is removed and the luminance signal component is obtained as shown in FIG. 7 (C1). Conversely, if the terminal 1 human input signal and the IH delay vA2 output signal are subtracted by the subtracter 4, the luminance signal component is removed and the color signal component shown in Figure 7+d) is obtained.In this way, 2.3 The Y/C separation configured with removal) comb filter, Fig. 8 (
bl indicates the frequency characteristic of a C-type (luminance signal removal) comb-shaped filter). The output signal of the adder 3 is limited by the low-pass filter 5 to the luminance signal recording band of the VTR. Next, the high-frequency components of the luminance signal are emphasized by the pre-emphasis circuit 6 due to the low-frequency triangular noise during FM demodulation, and then the FM modulator 7
The frequency is modulated by

On the other hand, the color signal output from the subtracter 4 is limited to a predetermined band by a bandpass filter 8, and then converted to a low band of several hundred KHz by a frequency converter 9. The output signal of the frequency converter 9 and the output signal of the FM modulator 7 are added by an adder 10, amplified by a recording amplifier 11, and recorded on a tape 13 by a recording head 12.

Next, the regeneration processing process will be explained.

The signal recorded on the tape 13 is detected by a reproducing head 14 and amplified by a reproducing amplifier 15 to a predetermined signal level. As for the luminance signal, the low-pass color signal is removed by the high-pass filter 16, and then FMy! , iI unit 17 demodulates the signal. Further, high-frequency noise is suppressed by a de-emphasis circuit 18 having characteristics opposite to those of the pre-emphasis circuit 6 during recording. Furthermore, in order to remove the carrier component of the FM signal, it is guided to a low-pass filter 19. Regarding the color signal, the output signal of the reproduction amplifier 15 is filtered by the low-pass filter 20 to reduce the luminance F.
After the M signal is removed, the frequency converter 21 performs 3.
It is returned to a high frequency signal of 58MHz. In the process of this frequency conversion, time axis fluctuations due to VTR speed fluctuations, etc. are removed. The output signal of the frequency converter 21 is passed through a bandpass filter 22 to remove unnecessary components outside the band, and then passed through a mixer 23.
and mixed with the luminance signal output from the low-pass filter 19.

In this case, the relationship between the signal processed as a color signal and the residual color signal processed as a luminance signal is as shown in FIG. 9, and when this is processed as a color signal, both the amplitude and first-order sum change. become.

[Problem to be solved by the invention]

Since conventional VTRs are configured as described above, the Y/C separation during recording is not sufficient, and the leakage component of the color signal to the luminance signal is directly FM modulated and recorded and reproduced, so the leakage color signal is Therefore, when mixed with the original color signal recorded by low frequency conversion and corrected for speed fluctuation, they interfere with each other, causing amplitude fluctuations and hue fluctuations in the color signal. This results in extremely poor image quality.

This invention was made to solve the above-mentioned problems, and its purpose is to provide a video signal recording and reproducing device that can widen the band of luminance signals without degrading the S/N of color signals. do.

[Means for Solving the Problems] The video signal recording and reproducing device according to the present invention is configured to correct the time axis of a reproduced luminance signal reproduced from a medium and subjected to FM demodulation, and then mix it with a reproduced carrier color signal. be.

[Effect]

The video signal recording and reproducing device according to the present invention has an FM
Since the time axis correction of the demodulated reproduced luminance signal is performed, the time axis fluctuation of the residual color signal in the luminance signal is eliminated,
The influence of mixing with color signals can be eliminated.

(Example〕 An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 1, the same symbols as in FIG. 6 indicate the same parts,
24 is a time axis correction circuit (Time Ba5e Correct) that corrects the time axis of the FM demodulated reproduced luminance signal.

r, hereinafter referred to as TBC).

Next, the operation will be explained. The composite video signal input to terminal 1 is input to IH delay line 2. Adder 3. The signal is separated into a luminance signal component and a color signal component by a comb-shaped filter constituted by a subtracter 4. The luminance signal separated from the color signal is limited to the luminance signal recording band of the VTR by a low-pass filter 5.
Next, for the purpose of reducing triangular noise during FM demodulation, a pre-emphasis circuit 6 emphasizes high-frequency components of the luminance signal, and then an FM modulator 7 frequency-modulates the luminance signal. On the other hand, the chrominance signal separated from the luminance signal is limited to a predetermined band by a bandpass filter 8, and then sent to a frequency converter 9 of several hundred kilohertz.
It is converted to the low frequency range of z. Frequency converter 9 output signal and F
The M modulator 7 output signals are added by an adder 10, amplified by a recording amplifier 11, and then recorded on a tape 13 by a recording head 12. The above recording process is the same as the conventional one.

Next, we will discuss the regeneration process. Information recorded on the tape 13 is detected by a playback head 14 and amplified by a playback amplifier 15 to a predetermined signal level. The luminance signal is demodulated by the FMfi modulator 17 after the low-pass color signal is removed by the high-pass filter 16 to become a baseband signal. Further, high-frequency noise is suppressed by a de-emphasis circuit 18 having characteristics opposite to those of the pre-emphasis circuit 6 during recording. Further, the signal is guided to a low-pass filter 19 to remove the carrier component of the FM signal. The luminance signal shown in FIG. 2(b) obtained at the output of the low-pass filter 19 is compared to the signal that should be obtained as shown in FIG. , a shift (τ) occurs in the horizontal period.

Also, if we look at the residual color components in the luminance signal, as shown in Figure 3(a), a phase shift (θ3, θ2) occurs with respect to the reference phase X, and changes in the Y direction and Z direction. . A brightness signal including such speed fluctuations is input to the TBC 24.

The TBC 24 has a configuration as shown in FIG.

The operation will be explained below.

The luminance signal input to the terminal 25 is guided to a variable delay line 26 composed of a CCD, semiconductor memory, or the like. variable delay′
The fa26 output signal is input to the horizontal synchronization separation circuit 27,
Here, the horizontal synchronization signal is separated. The separated horizontal synchronization signal is input to the phase comparator 29 together with a reference horizontal synchronization signal that is in synchronization with the burst frequency of the reproduced color signal input from the terminal 28, and the phase difference between the two is detected. The detection signal of the phase comparator 29 is used as a control signal of the delay control circuit 30. When the variable delay line 26 is a COD, the delay control circuit is a VCO (voltage controlled oscillator). Here, if the polarity of the delay control is determined so that the entire loop becomes negative feedback, the horizontal synchronizing signal phase in the output signal of the variable delay W26 matches the reference horizontal synchronizing signal phase. Therefore, if the reference horizontal synchronizing signal frequency is a signal that does not change over time, speed fluctuations in the output signal of the variable delay line 26 are removed, and there is no horizontal period shift as shown in FIG. 2(C). The phase shift is also removed as shown in Figure 3('b).

On the other hand, as for the color signal, the low-pass filter 20
After removing the luminance signal, the signal is returned to the original high-frequency color signal by the frequency converter 21, and at the same time, time axis fluctuations are also removed. After unnecessary components are removed from the output signal 21 by a bandpass filter 22, the output signal 21 is mixed with a luminance signal by an adder 23. In this case, the residual color signal processed as a luminance signal has a fixed influence on the color signal, as shown in FIG.
Does not change over time.

In addition, in the above embodiment, a horizontal synchronization signal is used to correct the time axis, but the signal for detecting the time axis variation of the luminance signal is not particularly limited to this, and the time axis variation of the luminance signal can be detected. In the above embodiment, NT
Although the SC signal has been described, the present invention can be applied to any system in which a color signal and a luminance signal are frequency interleaved and multiplexed, and similar effects can be obtained.

〔Effect of the invention〕

As described above, according to the present invention, during playback, the time axis fluctuations of the luminance signal are removed before mixing the color signal and the luminance signal, so that the luminance signal and the chrominance signal are reused from the mixed video signal. Even if they are processed separately, the phase and saturation of the color signal will not change, and the luminance signal can be made into a wider band without deteriorating the image quality of the color signal.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the recording and reproducing system of a VTR according to an embodiment of the present invention, FIGS. 2 and 3 are diagrams showing how time axis fluctuations are removed in the above embodiment, and FIG. FIG. 5 is a block diagram showing the configuration of the time axis correction circuit of the above embodiment; FIG. 5 is a diagram for explaining the present invention in detail; FIG. 6 is a block diagram of the recording and reproducing system of a conventional VTR; FIG. 8 is a block diagram showing the operating waveforms of the comb filter, FIG. 8 is a diagram showing the frequency spectrum of the comb filter, and FIG. 9 is a diagram showing the drawbacks of the conventional example. 24 is a TBC, 26 is a variable delay line, 27 is a horizontal synchronization separation circuit, 29 is a phase comparator, and 30 is a delay control circuit. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (1)

[Claims] (1) A video signal in which a luminance signal and a carrier chrominance signal are frequency multiplexed is used as an input signal, and during recording, the input signal is separated into a luminance signal and a carrier chrominance signal, the luminance signal is frequency-modulated, and the carrier chrominance signal is For this, the frequency is converted to the low band of the FM luminance signal, and both are frequency multiplexed and recorded. During playback, when frequency converting the reproduced low band carrier color signal to the normal carrier color signal, hue stabilization is performed, and the brightness signal About F
The FM demodulated reproduced luminance signal is subjected to time axis correction, and the reproduced carrier color signal after the time axis correction is mixed with the reproduced luminance signal subjected to the time axis correction to be output as a video signal. video signal recording and reproducing device.