KR940006624B1 - Y / C separation circuit of digital video signal - Google Patents

Abstract

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Description

Y / C separation circuit of digital video signal

1 is a block diagram of a conventional three-dimensional dynamic Y / C separation.

2 is a Y / C separation block diagram of the present invention.

3 is a detailed block diagram of the HBC 20 during the second.

4 is a detailed block diagram of the VP 40 during the second.

The present invention relates to a circuit for separating a luminance signal (hereinafter referred to as "Y") and a color signal (hereinafter referred to as "C") from a digitally converted composite video signal, and particularly for implementing Y / C separation at a lower cost. A Y / C separation circuit of a digital video signal.

Typically, Y / C separation circuits are essential for digital high-definition digital televisions as well as digital VTRs and other digital imaging devices to separate luminance and color signals.

Such a Y / C separation circuit is disclosed in a number of known prior arts, and a method and apparatus for Y / C separation of NTSC composite video signals by digital processing are shown in FIG. The above-mentioned FIG. 1 requires motion detection and its adaptive Y / C separation circuit, and in particular, since motion detection requires one frame of image memory, it has been a price increase factor in actual production.

In FIG. 1, a band pass filter (BPF) 1 is used to separate a color signal from a composite video signal applied to an input terminal in a frequency separation scheme, and the color signal is transmitted to a 3.58 MHz subcarrier. Based on the points shown, it consists of a filter centered on 3.5MHz and having a passband of ± 1.4MHz. In addition, the line comb filter 2 is a two-line comb filter which subtracts the current composite video signal V by one horizontal line delayed signal Vn and obtains a color signal value of a result of half multiplication. have.

That is, the color signal C is

C = (V _H -V) / 2 = {(Y _H + C _H )-(YC)} / 2

= {(Y _H -Y) + (C _H + C)} / 2... … … … … … … … … … … … … … … … … … … … … … Equation ①

Appears.

Assuming that the correlation between lines in Equation (1) is high, Yn-Y will be 0, and Cn + C will be 2C.

As a result of this, the color signal C value is obtained. In addition, the frame comb filter 3 uses the principle that the phase of the color signal is inverted (180 °) every NTSC composite video signal by one line delay unit 8, similar to the principle of the line comb filter 2 above. The color signal C is obtained using one VH signal and one VFH (1 frame delay signal) delayed by the one frame delay unit 9.

The motion detector 4 detects a motion factor by one frame difference, detects the difference ΔY of the luminance signal, takes its absolute value, and then calculates the coefficient according to the reference value of several steps. Make k. In this case, the made K is used as a coefficient representing the movement. The selection and mixer section 5 selects among the color signals C obtained from the BPF 1, the line comb filter 2, and the frame comb filter 3, and combines them to produce the final output color signal C. Will be determined. That is, when the input signal is a non-standard signal and the correlation between the frames of the lines does not match at all, the output of the BPF 1 is selected and output, and in the case of the standard signal according to the amount of motion of the image (that is, The output of the line comb filter 2 and the output of the frame comb filter 3 are mixed and output according to the operation coefficient k.

The mixing relation for this is as follows.

C _2M .k + C _H. (1-k) = C... … … … … … … … … … … … … … … … … … … … … … Expression ②

The detection of the non-standard signal is detected by the non-standard signal detector 7, when a signal that does not match the video game or VTR special playback and LDP (laser disc player) signal or other standard NTSC signal is input. The phases of the vertical sync (V Sync), the horizontal sync (H Sync), and the burst (Burst) signals are compared to generate a signal for determining whether or not a non-standard signal is present. According to the generated signal S, the selection and mixer unit 5 is configured to detect whether or not a non-standard signal.

As described above, since the Y / C separation circuit of a conventional high-definition digital TV performs a motion adaptive three-dimensional Y / C separation method, a lot of hardware is required in the process of realizing the IC into a product. In particular, since the frame memory capacity requires a large capacity of 4M-5M bits, there is a disadvantage that the price of the product increases.

Accordingly, an object of the present invention is to provide a Y / C separation circuit of a digital video signal capable of maintaining proper image quality without employing a frame memory.

According to the present invention for achieving the above object, a delay means for extracting the video signal of the current and the upper and lower lines of the input digital video signal, and the video signal of the current and the upper and lower lines of the delay means to the correlation of the upper and lower lines A filtering means for adaptively comb-filtering, a band adjusting means for horizontally adjusting a band of the filtering color signal output from the filtering means according to a transition value of the color signal, a band-adjusted color signal of the band adjusting means, and Color signal output control means for outputting the first and second color signals by inputting the low line signal and the SVHS signal of the video signal, and for extracting vertical contour components by inputting current and upper and lower image signals of the delay means. Contour extraction means, the output of the contour extraction means and the video signal of the current line of the delay means and the color signal output control Enter the first stage of the color signal by the current after subtracting the first color signal in the video signal of the line, the luminance signal extraction means for adding the output of said contour extraction means is provided.

Hereinafter, the present invention will be described with reference to the accompanying drawings.

2 is a block diagram of a Y / C separation according to the present invention, in which a color signal of an A / D converter 80 and a VHS that input a composite video signal to the first input terminal IN1 and convert it into a digital video signal are shown. An A / D converter 90 for inputting IN2) into a digital video signal, a line delay unit 81 for delaying the digital video signal of the A / D converter 80 by one horizontal line, and the line delay unit 81 A multiplexer 70 for multiplexing the output of the multiplexer and the output of the A / D converter 90 according to an applied SVHS signal, and a line delay unit 71 for delaying the output of the multiplexer 70 by one horizontal line. A delay means, an adaptive comb filter 10 corresponding to the filtering means, a horizontal bandwidth control (HBC) 20 corresponding to the band adjusting means, and a color output control unit 30 corresponding to the color signal output control means. And a VP (Vertical Peaking) 40 corresponding to the contour extraction means. It consists of a luminance extraction portion 50 corresponding to a number extracting means dosin.

3 is a detailed view of the HBC 20 in FIG. 2 and FIG. 4 is a detailed block diagram of the VP 40.

Hereinafter, the present invention will be described in detail the operation relationship based on the above configuration. First of all, the present invention is to minimize the artifacts caused by errors in Y / C separation while constructing a circuit at low cost by performing Y / C separation in two dimensions in actual hardware implementation.

In FIG. 2, the adaptive comb filter 10 is an important part of Y / C separation and extracts the color signal C from the digital composite video signal. Three Y / C separation filters are built in the comb filter 10, and their shapes are as follows.

First is a one-dimensional frequency separation filter (BPF). The one-dimensional frequency separation filter has characteristics such as band-pass filtering of color signals to separate Y / C like a normal analog TV, and is used when there is no correlation between screens or when inputting non-standard signals.

Second, it is an adaptive comb filter. This is used to detect the correlation between the upper and lower lines and perform one horizontal line comb filtering toward the higher correlation.

Third is a 2H comb filter. This is advantageous because the image quality is more stable than the adaptive comb filter when the change between the upper and lower lines is small. In particular, when the correlation between the upper and lower scanning lines is large, the Y / C separation characteristics are excellent. That is, the adaptive comb filter 10 has a built-in configuration for detecting and counting correlations between upper and lower lines of luminance and color signals. _{After the LOW} component is detected and its absolute value is taken, it is | ΔY _LOW | and the reference value of several steps (for example, R (Adaptive Comb), R (2H comb); Reference value R (x) Numbered by size). In other words, it is important to select a corresponding filter according to the coefficient.

The HBC 20 is for adjusting the horizontal band. For example, if an error occurs when extracting a color signal, the effect will also appear on the luminance signal. Even if the filter 10 extracts an optimal color signal, the spectrum of the luminance and the color signal in the two-dimensional configuration is assumed. This overlap cannot be completely removed.

Therefore, to compensate for this, the horizontal band is adjusted. That is, the characteristics of the color signal for luminance detection are grasped, and the luminance and color signals are varied by varying the characteristics of the high frequency region of the color signal for detecting the color signal using the value of the amount of transition and the magnitude of the color signal. Minimize interference. As a result, the size of the region where the mutual interference effect is reduced is much reduced, but the original signal amount of the portion is also reduced by the same amount. That is, when there is a transition of the color signal, the color signal has a wide band width. Therefore, the color signal for extracting the luminance passes through the wide BPF and otherwise passes through the narrow BPF.

A detailed configuration of the HBC 20 is shown in detail in FIG. 3 and it can be seen that hardware is implemented according to the above description. The color output control unit 30 receives three color signal inputs. That is, the Y / C separated horizontal band adjusted color signal, the Y / C separated and bypassed color signal, and the other one is the SVHS input color signal.

If the system is in SVHS mode, the SVHS input color signal is exported as the output color signal and the output of line g is not exported. Otherwise, the output of the line e is outputted to the output of line e by the C output, and the output signal of the line h is output to the output of the line g. That is, the color signal to be subtracted from the composite video signal to extract the luminance is the first color signal, and the color signal for the color signal itself outputs the BPF color signal, that is, the second color signal.

VP 40 is for vertical peaking, VBPF 42 for extracting vertical contour components, LPF 44 for limiting bands horizontally, and vertical contour, as in the configuration of FIG. The core 45 has a structure of a core 45, a gain 46, and a limiting 47 for non-linear transformation of the amount.

In addition, the luminance extractor 50 receives three input signals. That is, the digital video signal V _H delayed by one line, the output signal Y _VC of the VP 40, and the output color signal (first color signal) of the line g. The extractor 50 first subtracts the first color signal from V _H to obtain the luminance signal Y, and then adds the luminance signal Y to the output signal Y _VC of the VP 40. Generate the final output signal (Vout) signal.

In the present invention, the VP 40 and the color output controller 30 may be selectively removed, and the 2H comb filter may be selected instead of the BPF in the adaptive comb filter 10.

As described above, since the present invention does not require a frame memory, there is an advantage in that a circuit can be configured at low cost and an image quality can be improved in luminance and color signal separation.

Claims (3)

A luminance and color signal separation circuit of a digital video signal, comprising: delay means for extracting video signals of current and upper and lower lines of an input digital video signal, and correlation between upper and lower lines of the current and upper and lower video signals of the delay means; Filtering means for adaptively comb-filtering according to the present invention, band adjusting means for horizontally adjusting a band of the filtering color signal output from the filtering means according to a transition value of the color signal, band-adjusted color signal of the band adjusting means, and Color signal output control means for inputting the lower line signal and the SVHS signal of the video signal to output the first and second color signals, and inputting the current and upper and lower video signals of the delay means to extract vertical contour components. Contour extracting means, an output of the contour extracting means, a video signal of the current line of the delay means and the color signal output By entering the first color signal of the control means the current after subtracting the first color signal in the video signal of the line the outline extracting luminance characterized in that consists of the luminance signal extraction means for adding the output of the means and the color signal separation circuit. 2. The luminance and color signal separation circuit according to claim 1, wherein the band adjusting means is made of a narrow BPF or an optical BPF for narrowly or broadly filtering the comb filtering color signal. The VBPF 42 for filtering vertical contour components by inputting the video signal, and the LPF 44 for band-limiting the filtering output of the VBPF 42 in a horizontal direction. And means for non-linearly converting the output of the LPF (44).