JPS61265995A - Video signal reproducing device - Google Patents

Abstract

PURPOSE:To reproduce properly a chromaticity signal and to insure a luminous high frequency component against fluctuating due to a jitter by bisecting a signal subjected to low frequency conversion and giving no jitter to the chromaticity signal and making the high frequency component of a luminance signal into a signal having the same jitter as a low frequency component. CONSTITUTION:In terms of a APC 902, a jitter component is removed by the 1st fixed oscillator 95, and is frequency-converted. A chromaticity comb line filter CCF 7 outputs only the chromaticity signal. In terms of an APC 901, the signal is frequency-converted as it has a jitter with the aid of the output of an FM demodulator 55. A high frequency luminance signal YH obtained in such a way, carrier chromaticity signal and a low frequency luminance signal YL being the output of the FM demodulator 55 are synthesized. Thus an output terminal 76 obtains the carrier chrominance signal without a jitter and the luminance signal having the same jitter in the low and high frequency components. Since the chromaticity signal has no jitter, its color is properly reproduced, and the high frequency component of the luminance signal can be viewed without fluctuation.

Description

DETAILED DESCRIPTION OF THE INVENTION FIELD OF INDUSTRIAL APPLICATION The present invention relates to an apparatus for reproducing video signals recorded using a low frequency conversion method.

2. Description of the Related Art Conventional general low frequency conversion video signal recording and reproducing apparatuses have configurations as shown in FIGS. 4 and 6, respectively. This will be explained using FIG. Figure 3 (&) shows NTSC or PA in which luminance signal Y and chromaticity signal C are combined.
This indicates a composite color video signal such as L, but the following is an NTSC
Explain with signals.

The NTSC signal is applied to input terminal 60 in FIG. Then, a low pass filter (hereinafter referred to as LPF) of about 3 MHz is applied.
As shown in FIG. 3 (bl), the output of the 61 is only the low-frequency luminance signal YL, which is the low-frequency component of the luminance signal Y, and this is converted into a frequency modulated signal (
(hereinafter referred to as FM signal). On the other hand, the composite color video signal that has passed through the band pass filter (hereinafter referred to as BFF) 64 is a high-frequency component Y of the luminance signal Y, as shown in FIG. 3(C).
H and the carrier color signal C are combined. Chromaticity signal C
If we consider dividing into subcarrier frequency fs and sideband component c, this can be expressed as fs−)fc+τH. From this signal, only the burst signal is extracted by the burst gate 66, and a continuous wave of the burst frequency, that is, the subcarrier frequency fs is obtained by a PLL (phase locked loop) consisting of a phase comparator 66LPF6 and a voltage controlled crystal oscillator (VXO) 6S. , furthermore, from the horizontal synchronization signal fH extracted from the composite color video signal by the synchronization separator 71, a low frequency The signal obtained by obtaining the subcarrier f1 and using the balanced modulator (hereinafter referred to as BM) 69 is as follows:
Since it becomes a continuous wave with a frequency of fs + f1, this and the output of the BPF 64 are input to the BM 70 to obtain a low frequency conversion signal centered on the low frequency subcarrier f1. This signal and F
The synthesized M signal is shown in FIG. 3(d) and is amplified by a recording amplifier 63 and recorded on a magnetic tape or the like by a head 51.

FIG. 5 is a block diagram of the reproduction side, in which the reproduction signal obtained by the head 51 is amplified by a preamplifier 62, and then filtered through a bypass filter (hereinafter referred to as HPF) 53 and an LPF.
6 into an FM signal and a low frequency conversion signal. The FM signal is amplitude limited by IJ Mitsutaro 4 to suppress amplitude fluctuations, and demodulated by 7M demodulator 66 to obtain the original low-band luminance signal YL. However, it includes jitter Δ in the drive system of the magnetic tape, etc.

On the other hand, the low frequency conversion signal is returned to the carrier color signal C centered on the original subcarrier fs by the output of the local oscillator 95 and the chromaticity processing unit (human PC) 9, and is combined with the low frequency luminance signal YL. At the output terminal 76, the original composite color video signal is obtained. At this time, the fifth PC 9 operates to stabilize the phase of the subcarrier so that colors can be reproduced correctly on the receiver side. In other words, on PC9, 8M
From the signal that has undergone frequency conversion in 91 and passed through BPF 92, only the burst portion is extracted by burst gate 93, and its phase is compared with the output of subcarrier fixed oscillator 96 by phase comparator 94. The obtained error signal is output by LPF 98. It is smoothed and drives the VCO 97.

The output of vcos7 is the frequency of the low subcarrier f1 plus an error, which is the frequency of the subcarrier fixed oscillator 9.
The output of 6 is frequency-converted by 8M9B, and the low frequency conversion signal is frequency-converted by 8M91. Then, a carrier color signal fs-1-fc-1-YH is obtained as shown in the following equation.

(f'5-1-f, +Δ) -(fl-fc-YH+Δ
)=fs + fc + YH Since this loop performs negative feedback operation to eliminate errors, a signal without jitter components is obtained as an output. This is generally called a PC loop. These are described in Japanese Patent Publication No. 60-14852.

Now, since the jitter of the carrier color signal has been removed, the colors are correctly reproduced, and the FM demodulated low-band luminance signal YL+Δ
contains jitter. However, since it can be tracked on the receiver side, the image can be reproduced.

By the way, jitter has been removed from the high-frequency luminance signal YH, which is included in the carrier color signal band signal by frequency-converting the low-frequency conversion signal, but the receiver follows the jitter of the low-frequency luminance signal YL+Δ. Therefore, it appears to be distorted, as if there is jitter, and the reproduced high-frequency luminance signal YH
are not fully utilized. This method of making use of the high-frequency luminance signal YH is also described in Japanese Patent Application Laid-open No. 57-89387-89, but it requires a time base collector and cannot be easily constructed.

Problems to be Solved by the Invention These conventional methods cannot make full use of the high-frequency components of the luminance signal mixed into the chromaticity signal. there was.

The present invention has been made in view of the above points, and an object of the present invention is to provide a video signal reproducing device that has a simple configuration, makes use of high-frequency components of a luminance signal, and does not require a device such as a time base collector. There is.

Means to Solve the Problems In order to solve the above problems, the present invention divides the low frequency converted signal into two, and on the other hand, focuses on the chromaticity signal and performs processing to remove subcarrier jitter. , Then, only the chromaticity signal is extracted with a chromaticity signal comb filter (CAP), and on the other hand, focusing on the luminance signal, frequency conversion is performed with jitter included, and then only the luminance signal is converted according to the jitter. A luminance signal comb filter (hereinafter referred to as ycy) using a 1H delay line with varying delay time extracts the luminance signal, combines these two signals with the FM demodulated low-frequency luminance signal, and removes jitter from the chromaticity signal. By making the high-frequency component of the luminance signal a signal that has the same jitter as the low-frequency component, it is possible to obtain a video signal in which the chromaticity signal is correctly reproduced and the high-frequency component of the luminance does not fluctuate due to jitter. .

Effect of the Invention With the above-described configuration, the present invention can obtain a jitter-free carrier chromaticity signal and a high-range luminance signal that is synchronized with a low-range luminance signal. Provides high resolution and reproduces accurate colors.

Embodiment FIG. 1 is a block diagram showing an embodiment of the video signal reproduction system of the present invention. In FIG. 1, the same components as in FIG. 5 are given the same numbers, and their explanations will be omitted.

The two human PCs 901 and 902 in Figure 1 are the PCs in Figure 6.
It has the same configuration as 9.

In FIG. 1, the signal passing through the 0LPF 6, which describes the case of an NTSG signal, is input to the PC 901 and the PC 9o2. In the human PC 902, as in FIG.
outputs only the chromaticity signal. As is well known, in this method, the chromaticity signal and the luminance signal have a frequency interleaved relationship as shown in FIG. Filter (CCF
) 7 can easily pass only the chromaticity signal.

On the other hand, in the PC 901, from the output of the 7M demodulator 55,
PLL based on the horizontal synchronization signal obtained by the synchronization separator 56
A 455 multiplier 67.1/2 frequency divider 58 is configured with a frequency converting carrier wave that has passed from the second oscillator through the phase control unit 4, and the frequency of the subcarrier fs is 227.5 times that of the horizontal synchronization signal. Frequency conversion is performed with jitter present. Tsumashi, fs of person PC9 in Figure 6 changes to fs + Δ,
Since the output of the BM98 is considered to be f's +f, -)-2Δ, the output of the human PC9o1 is fs -)-fc +YH+Δ, as shown in the following equation.

(fs-1-fl-1-2Δ)-(f,-fc-YH+
Δ)=fs-)-f'c-1-YH+Δ Further, only the luminance signal is extracted by a luminance signal comb filter (YCF) 8 having the frequency characteristic shown by the broken line in FIG. In other words, the chromaticity signal is attenuated at the valleys of the comb filter. However, as mentioned above, this signal is accompanied by jitter, so the spectrum in Figure (b) oscillates left and right.If the comb-shaped filter uses a delay line with a constant delay time, the width of the valley will increase. Because it is narrow, it is not possible to sufficiently attenuate the chromaticity signal.

Therefore, in FIG. 1, the luminance signal comb filter 8 is constructed of a comb filter using a variable delay line, such as a CCD 81, whose delay time changes depending on the frequency of the clock pulse. Then, the clock pulse is transferred to the synchronous separator 5.
The third signal is phase-locked to the synchronization signal with jitter obtained in step 6.
By obtaining the signal from the oscillator, the frequency characteristic shown in FIG. 2 (IL) fluctuates from side to side in the same way as the signal in the carrier chrominance signal band, so that the chromaticity signal can be effectively attenuated.

Finally, the third oscillator is an N multiplier 69, which obtains a frequency N times the frequency of the synchronizing signal accompanied by jitter, and supplies this to the N stage CCD 81.
By matching the correlation between the output and the input of the CD 81, chromaticity signals having an opposite phase relationship are attenuated.

By combining the high-frequency luminance signal YH obtained in this way, the carrier chromaticity signal, and the low-frequency luminance signal YL that is the output of the 7M demodulator 66, the output terminal 76 outputs a jitter-free carrier color signal. A luminance signal with the same jitter in the high-frequency and low-frequency components of the luminance signal is obtained, and when viewed on a receiver, the chromaticity signal has no jitter, so the colors are correctly reproduced.
Since it follows the jitter of the luminance signal, the high range of the luminance signal can be seen without fluctuation.

Note that if the frequencies of the third oscillator and the second oscillator are in a multiple relationship, the oscillation source of the PLL can be shared. For example, if a 455-stage COD is used, the output of the third oscillator is extracted from the second oscillator multiplied by 455, thereby substantially eliminating the component of the third oscillator.

Effects of the Invention As described above, according to the present invention, high-frequency components of a low-frequency-converted luminance signal can be reproduced with an extremely simple configuration, and without using complicated devices such as a time base collector. Colors can be reproduced correctly, making it extremely useful for practical purposes.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a video signal reproducing device according to an embodiment of the present invention, FIG. 2 is a diagram showing the relationship between the characteristics of a comb filter and frequency interleaving, and FIG. 3 is a diagram showing the frequency spectrum of each signal. , FIG. 4 is a block diagram showing a conventional video signal recording device, and FIG. 6 is a block diagram showing a conventional video signal reproducing device. 8... Luminance signal comb filter, 81...
...COD. 901...APC, 56...Sync separator, 57...466 multiplier, 68...
1/2 frequency divider, 59...N multiplier. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2 Figure 3 Figure 4 Figure 5

Claims (3)

[Claims] (1) Frequency modulation of the carrier wave using a low-frequency conversion signal obtained by converting the frequency of the carrier color signal band signal separated from the composite color video signal to a low frequency band and a luminance signal separated from the composite color video signal using a low-pass filter. The reproduced low-pass conversion signal separated from the reproduced signal obtained by reproducing the same is multiplex-recorded with the frequency modulated signal obtained by the above process, and the reproduced carrier color signal band signal obtained by frequency converting the reproduced low-pass conversion signal to the original frequency band. , in a video recording and reproducing apparatus which obtains a reproduced composite color video signal by mixing a reproduced frequency modulation signal separated from the reproduced signal with a reproduced luminance signal obtained by demodulating the reproduced frequency modulation signal, the frequency conversion process of the reproduced low frequency conversion signal is performed in two steps. One side uses a fixed first local oscillator to obtain a signal in the reproduced carrier color signal band without jitter components, and outputs a reproduced carrier color signal from which only the color signal component is extracted using a chromaticity signal comb filter. The other has second and third local oscillators that are phase synchronized with a horizontal synchronizing signal separated from the reproduced luminance signal or a signal containing a jitter component such as a pilot signal recorded at the same time, and the second local oscillator A signal in the reproduced carrier chrominance signal band including a jitter component is obtained, the output of the third local oscillator is used as a clock pulse, and a luminance signal comb is formed using a delay line whose delay time changes according to the frequency of the clock pulse. An image characterized in that a reproduced high-frequency luminance signal, which is a high-frequency component of a luminance signal included in a reproduced carrier color signal band, is outputted by a filter, and is mixed with the reproduced carrier color signal and the reproduced luminance signal. Signal regenerator. (2) The video signal reproducing device according to claim (1), wherein the second local oscillator and the third local oscillator are the same. (3) The video signal reproducing device according to claim (1), wherein the oscillation source is shared when the frequencies of the second local oscillator and the third local oscillator are in a multiple relationship.