KR20030081698A - Method For Separating Luminance/Color Signals In The Comb Filter - Google Patents

Abstract

PURPOSE: A method for separating a brightness signal from a color signal in a comb filter is provided to prevent a blurry picture cause of lowering the brightness signal in the case of separating the brightness signal from the color signal. CONSTITUTION: It is discriminated whether a horizontal edge and a vertical edge exist at a sample point where the current brightness and color signals are to be separated(S10). Normal horizontal filtering and vertical filtering are selectively applied to divide the brightness and color signals(S20). After applying the vertical filtering to the sample point and peripheral sample points and the horizontal filtering is applied to all the results of the application(S30-S40). Enhancement elements are added to the obtained brightness signal and color signal for deciding final brightness and color signals(S50).

Description

Method for Separating Luminance / Color Signals In The Comb Filter}

The present invention relates to a method of separating luminance / color signals from a composite video signal, and more particularly, luminance / color signal separation in a comb filter to suppress image quality deterioration by properly separating luminance / color signals from a composite video signal. It is about a method.

In general, quadrature-modulated color TVs, such as the National Television System Committee (NTSC) or Phase Alternating Line System (PAL), use color signals in luminance signals to efficiently use a limited frequency band. Interleave. Therefore, a process of separating the luminance / color signal from the input video signal in a color television as a receiving end is necessary. The separation process of the luminance / color signal is typically performed by a comb filter. However, it is not easy to properly separate the luminance / color signals because the luminance / color signals exist in some frequency bands due to the characteristics of the input image signal. If the luminance / color signal is incorrectly separated, several undesirable phenomena appear. Typical examples are cross luminance such as dot obstruction, occurrence of rainbow fringes and cross color phenomenon. The cross color phenomenon is a phenomenon caused by the detection of the high frequency component of the luminance signal as part of the color signal, and the cross luminance phenomenon is a phenomenon caused by the detection of the low frequency component of the color signal as part of the luminance signal called dot crawl. to be. Therefore, in color television or video recording and reproducing apparatus, complete separation of luminance / color signals is required.

Recently, in order to improve such a point, a line comb filter and a frame comb filter have been proposed, which uses a feature in which the phase of a color signal is inverted every line and every frame in an NTSC color video signal. A luminance / color signal separation scheme and a motion adaptive luminance / color signal separation scheme that adaptively uses luminance / color signal separation in a three-dimensional region for motion information have been proposed.

The luminance / color signal separation scheme is applied to a plasma display panel (PDP) system. As an example, as shown in FIG. 1, the luminance / color signal separation apparatus 10 may include four parts of the memory unit 11, the three-dimensional comb filter 13, the image processing processor 15, and the deinterlacing unit 17. It consists of.

When the luminance / color signal separation device 10 is applied to the PDP system, the cross luminance or cross color phenomenon continues to appear because the luminance / color signal is still not properly separated on the boundary line. Examples of the cross luminance phenomenon include a dot crawl or a hanging dot phenomenon appearing on a boundary line.

The reason why the luminance / color signal is not properly separated will be described with reference to FIGS. 2 to 6. For example, in FIGS. 2 to 6, it is assumed that the sample point S5 to which the current luminance signal and the color signal are to be separated is on the line 1, and the sampling value of the sample point S5 is N5. At this time, the sampling values of the sample points S4 and S6 on the left and right of the sample point S5 on the line l are N4 and N6, respectively, and the lines l-1 and l adjacent to the sample point S5, respectively. The sampling values of sample point S2 on +1) are N2 and N8, respectively. On the line (l-1), sampling values of the sample points S1 and S3 on the left and right of the sample point S2 are N1 and N3, respectively. Sampling values of sample points S7 and S9 on the left and right sides of the sample point S8 on the line 1 + 1 are N7 and N9, respectively. Where? And? Indicate inverted mutually as the color subcarrier phase of the sample point, and?,? Indicate inverted each other as the color subcarrier phase of the corresponding sample point. Further,? Represents Y + U,? Represents Y-U,? Represents Y + V, and? Represents Y-V.

Thus, the phases of the sampling values N1, N3, N5, N7, N9 and the sampling values N2, N4, N6, N8 are inverted from each other. The sampling values N1, N3, N5, N7, and N9 represent the difference between the sampled luminance signal value Y and the color signal value C, that is, YU, and the sampling values N2, N4, N6, and N8 represent the sampled luminance. The sum of the signal value Y and the color signal value C, i.e., Y + U.

In this condition, when the comb filter 13 processes the luminance / color signal separation at the sample point S5, a general equation for the separation of the luminance / color signal is expressed by Equation 1 below.

Yh = N5-Ch = Y

Yv = N5-Cv = Y

Here, Ch is used to separate data that is horizontal and Cv is used to separate data that is vertical. That is, Ch corresponds to a horizontal filter and Cv corresponds to a vertical filter. C is a color signal and Y is a luminance signal.

As mentioned above, Ch is a method of separating the color (C) signal by using the sampling value of the horizontal position, and the resultant color (C) signal is put into a filter such as Yh to obtain the luminance (Y) signal. Find the value. In a similar way, Cv calculates the values of the color (C) signal and the luminance (Y) signal by using sampling values that are also vertical on the vertical line. At this time, the sample point to be obtained is S5, and the color (C) signal is U and V, which can be obtained according to the sampling value. In FIG. 2, since the sampling value N5 of the sample point S5 to be obtained currently has the form of Y-U, the value of the color (C) signal corresponds to the value of U.

However, in the general position, the luminance / color signal separation of the NTSC color image signal is performed as in the case of using the horizontal filter in Equation 1 above. However, as shown in FIGS. 3 and 4, in the case of an NTSC color image signal located at an edge or as shown in FIGS. 5 and 6, an NTSC color image hung in a narrow band. In the case of signals, the luminance / color signals are not separated properly.

In more detail, in the case where the horizontal edge of FIG. 3 occurs, when the Ch in Equation 1 is applied to the sample point S5 having the horizontal edge, the color (C) signal is properly separated. However, when Cv of Equation 1 is applied, the color C signal is not properly separated and is expressed as Equation 2 below.

Further, in the case where the vertical edge of FIG. 4 occurs, when the Cv of Equation 1 is applied to the sample point S5 having the vertical edge, the color (C) signal is properly separated. However, when the Ch of Equation 1 is applied, the color C signal is not properly separated.

That is, in the part with the horizontal edge, when the value of the color (C) signal is separated using Cv, the value of the color (C) signal and the value of the luminance (Y) signal of different types are mixed. The value becomes the value of the color (C) signal. That is, the color (C) signal is not separated at all, but rather a phenomenon in which several signals are mixed.

In more detail, in the case where the sampling value N5 of the sample point S5 to be obtained in FIG. 3 is Y-C, the sampling values N8 and N2 are used together when using Cv. In this case, N8 is Y + C, but N2 is Y'-C 'which has a different value from N5 on the horizontal edge, so it may have a different value of luminance (Y) and color (C) from N5. high. At this time, assuming that N2 = Y '+ C', N5 = Y-C, N8 = Y + C, and applying Cv of Equation 1, the same result as Equation 2 is obtained. Accordingly, the phenomenon that the value of the color C signal is not separated, but rather the values of C-C 'Y-Y' are mixed. This brings about a cross color phenomenon.

Similarly, in the case of the narrow line, when the values of the luminance (Y) signal and the color (C) signal are separated, a phenomenon in which these values are mixed with each other occurs. That is, as shown in FIG. 5, when the horizontal line is caught in the narrow band, a phenomenon in which the separation of the color (C) signal and the luminance (Y) signal is not properly performed and is represented by the following Equation 3 may occur. have.

Yh = Y-Ch = Y

In addition, as shown in FIG. 5, even when the vertical filter is used when the horizontal narrow band is caught, the separation of the color (C) signal and the luminance (Y) signal is not performed properly, and is represented by the following equation (4). May occur.

As shown in FIG. 4, when the narrow band is a horizontal line, when three sample points S4, S5, and S6 of the horizontal line all have the same value of Y, Ch in the above Equation 3 When applied, Ch becomes 0, and substituting it into the equation for Yh yields a well-separated value of Y. However, in this case, if the sampling values N2 and N8 of the sample points S2 and S8 are the same Y when Cv is applied, and only the sampling value N5 of the sample point S5 is Y ', Cv and Yv of Equation 4 are applied. When you do that, you get the wrong Y and C values. (In case of narrow band, it is a black line, so the value of color (C) signal should be 0).

In the opposite case, that is, when the narrow band is a vertical line, as shown in Fig. 5, a similar problem occurs when Ch is applied.

As can be seen in Equation 2, Equation 3, and Equation 4, the luminance / color signal separation is not properly performed at the sample point with an edge or the sample point with a narrow band, which is cross luminance and Cause cross color phenomenon. That is, a phenomenon in which rainbow colors are mixed at the edges or a mixture of colors on the edges is caused. As a result, in the conventional large-screen PDP, the image quality deterioration is not serious, but the overall border of the screen is blurred.

In order to suppress this phenomenon, there is an urgent need for a two-dimensional adaptive comb filter capable of properly processing the luminance / color signal separation even at the edge portion or the narrow band portion.

Accordingly, an object of the present invention is to provide a method for separating luminance / color signals in a comb filter to suppress image quality deterioration by properly separating luminance / color signals at an edge portion.

Another object of the present invention is to provide a method of separating luminance / color signals in a comb filter to suppress image quality degradation by properly separating luminance / color signals in a narrow band.

It is still another object of the present invention to provide a method for recovering luminance and color components lost in a filtering process of separating luminance / color through an enhancement factor.

1 is a block diagram showing a luminance / color signal separation device applied to a conventional PDP panel.

2 is a two-dimensional data array diagram of an NTSC composite video signal sampled at 4fsc, which is four times the color subcarrier frequency fsc to which the present invention is applied;

3 is a two-dimensional data arrangement diagram in the case where there is a horizontal edge in FIG.

4 is a two-dimensional data arrangement diagram in the case where there is a vertical edge in FIG.

FIG. 5 is a two-dimensional data array diagram when a narrow line (horizontal line) is caught in a narrow band in FIG. 2; FIG.

FIG. 6 is a two-dimensional data arrangement diagram when the narrow line (horizontal line) is caught in the narrow band in FIG. 2; FIG.

7 is a flowchart illustrating a method of separating luminance / color signals in a comb filter according to the present invention;

In the comb filter according to the present invention for achieving the above object, the luminance / color signal separation method is a step of determining whether the horizontal edge and the vertical edge is not over the sample point to separate the current luminance signal and the color signal; ; Selectively applying general horizontal and vertical filtering to separate the luminance signal and the color signal at the sample point according to the determination result; A vertical / horizontal filtering step of applying vertical filtering to the sample point and predetermined sample points around the sample point and then applying horizontal filtering to all of the results; And adding an enhancement element to the obtained luminance signal and color signal to determine a final luminance signal and a color signal.

Preferably, the vertical / horizontal filtering step applies first vertical filtering to sample points centered on a sample point horizontally to the left of the sample point, and applies a second vertical filter to sample points centered on the sample point. The vertical filtering may be applied, and the third vertical filtering may be applied to the sample points centered on the sample points on the horizontal right side of the sample point.

Preferably, in the vertical / horizontal filtering step, first vertical filtering is applied to three sample points centered on a sample point on the horizontal left side of the sample point, and three sample points centered on the sample point. The second vertical filtering may be applied to the field, and the third vertical filtering may be applied to the three sample points around the sample points on the horizontal right side of the sample point.

Preferably, the vertical / horizontal filtering step may apply horizontal filtering to the values of the first, second, and third vertical filtering.

Preferably, the enhancement step may determine the final luminance signal by applying horizontal filtering to the luminance signal at the sample point and the horizontal left and right sample points, and adding the result to the luminance of the sample point. have.

Preferably, the enhancement step may determine the final luminance by applying horizontal filtering to the first, second, and third vertical filtering results, and adding the result with the color signal of the sample point.

Hereinafter, a method of separating luminance / color signals in a comb filter according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

7 is a flowchart illustrating a method of separating luminance / color signals in a comb filter according to the present invention. The same reference numerals are given to the same parts as those in Figs.

Referring to FIG. 7, for example, if the sample point for the current luminance / color signal separation is S5, it is determined in step S10 whether the sample point S5 has a horizontal edge or a vertical edge. In more detail, when there is a horizontal correlation at the sample point S5, that is, when the absolute value for the difference between N4 and N6 is less than or equal to an arbitrary threshold Kh, as shown in Equation 5 below. , It is determined that there is a horizontal edge. In addition, if the absolute value for the difference between Yh2 and Yh8 is greater than or equal to any threshold value Kyv, it can be determined that the horizontal edge is more certain. If the absolute value of the difference between N4 and N6 is less than or equal to Kh, the N4 and N6 have the same sampling value. This means that the N4 and N6 are located on a line not separated from the horizontal edge.

vert N4-N6 vert = Kh

vert Yh2-Yh8 vert> = Kyv

Where Kh and Kyv are thresholds. Yh2 and Yh8 are luminance signal values at sample points S2 and S8.

When there is a vertical correlation at the sample point S5, that is, when the absolute value of the difference between N2 and N8 is less than or equal to Kv, as shown in Equation 6, it is determined that there is a vertical edge. In addition, if the absolute value for the difference between Yv4 and Yv6 is greater than or equal to any threshold Kyh, it can be determined that the vertical edge is more certain.

vert N2-N8 vert = Kv

vert Yv4-Yv6 vert> = Kyh

Where Kv and Kyv are thresholds.

On the other hand, in all other cases, it is determined that there is no horizontal edge and vertical edge.

When it is determined that the horizontal edge exists, the luminance / color signal at the sample point S5 can be properly separated by performing horizontal filtering as in Ch in Equation 1 in step S20.

If it is determined that the vertical edge exists, the luminance / color signal at the sample point S5 can be properly separated by performing vertical filtering as in Cv of Equation 1 in step S30.

If it is determined that there are no horizontal edges or vertical edges, the present invention provides a current luminance / color signal in step S40 to solve the conventional problem that a general luminance / color signal separation method is not appropriate in the narrow band portion. 2D comb filter as shown in Equation 7 below is further applied to the sampling value of the sample point S5 to be separated and the eight sample points around it. Therefore, a better luminance / color signal value can be filtered at the sample point S5.

Here, Chv is a color signal value horizontally filtered using values of Cv4, {} Cv5, and {} Cv6 instead of using N4, N5, and N6 values. Cv4 is a color signal value vertically filtered on the upper and lower N1 and N7 around N4, Cv5 is a color signal value vertically filtered on the upper, lower N2 and N8 around N5, and Cv6 is centered on N6. N3 and N9 are vertically filtered color signal values.

That is, in step S40, the luminance / color signal separation of the sample point S5 should first obtain the values of Cv4, {} Cv5, {} Cv6, and then the value of Chv. In more detail, the vertical filtering of the sample points S4 adjacent to the sample point S5 for the current luminance / color signal separation and the sampling values N1, N4, N7 of the upper and lower sample points S1, S7 on the vertical line of the Cv4 is performed. Find the value. Similarly, sampling values N2, N5 and N8 of the sample point S5 and the upper and lower sample points S2 and S8 on the vertical line are vertically filtered to obtain the value of Cv5. Further, the value of Cv6 is obtained by vertical filtering the sample points S6 adjacent to the sample point S5 and the sampling values N3, N6 and N9 of the upper and lower sample points S3 and S9 on the vertical line. Then, the values of Cv4, Cv5, and Cv6 are horizontally filtered to obtain the value of Chv. Therefore, luminance / color signal separation at the sample point S5 can be made better than in the prior art.

In other words, when C 'is a C value that needs to be separated, Cv4, {} Cv5, {} Cv6 are mixed with pure C values such as C' + α, C'-α, and C '+ α. In this case, if you apply Chv, you can separate the C 'value. It can also be properly separated even when applied to a narrow band.

After the vertical / horizontal filtering is completed, the luminance signal value Y5 and the color signal value C5 are enhanced in step S50. In more detail, using the luminance signal values Y4, Y5, Y6 obtained after filtering the sample points 4, 5, and 6, horizontal filtering is performed as shown in Equation 8 below. Find the value. In addition, by using the values of Cv4, {} Cv5, and {} Cv6, vertical filtering is performed as shown in Equation 8 to obtain the value of Av, which is a vertical reinforcement element.

Then, the value of Y5 is added to the value of Ah, and the result is determined as the final luminance signal value Y5 at the sample point S5. Similarly, the value of C5 is added to the value of Av and the resulting value is determined as the final color signal value C5 at the sample point S5.

Therefore, the present invention can reinforce the value of Y5 by obtaining the value of the luminance signal of the lost portion when the composite video signal is separated into the luminance signal and the color signal and adding it to the value of Y5. As a result, the overall blurring of the screen and the inferior sharpness of the boundary line may be eliminated due to the decrease in the luminance signal value generated in the conventional luminance / color signal separation process. Moreover, image quality deterioration in the large screen PDP can be improved.

As described above, the luminance / color signal separation method in the comb filter according to the present invention determines whether the sample point to which the luminance / color signal is currently separated has a horizontal edge or a vertical edge or no edge. In this case, if there is a horizontal edge, a conventional horizontal filter is used, and if there is a vertical edge, a color signal value and a luminance signal value are obtained using a vertical filter. Different filters are used depending on the tendency of the horizontal and vertical edges. In addition, to compensate for the inability to separate the luminance / color signals in the narrow band in the case of non-vertical / horizontal edges, the sample point to which the current luminance / color signal is separated and the eight samples around it Apply a two-dimensional filter on the points. Finally, the final luminance value is determined by reinforcing the luminance signal value and the color signal value obtained at the sample point from which the current luminance / color signal is to be separated.

Accordingly, the present invention can eliminate the overall blurring phenomenon of the screen and the inferior sharpness of the boundary due to the decrease in the luminance signal value generated in the conventional luminance / color signal separation process. As a result, image quality deterioration in the large screen PDP can be improved.

On the other hand, the present invention is not limited to the contents described in the drawings and detailed description, it is obvious to those skilled in the art that various modifications can be made without departing from the spirit of the invention. .

Claims (6)

Determining whether a horizontal edge and a vertical edge extend from a sample point to which a current luminance signal and a color signal are to be separated; Selectively applying general horizontal and vertical filtering to separate the luminance signal and the color signal at the sample point according to the determination result; A vertical / horizontal filtering step of applying vertical filtering to the sample point and predetermined sample points around the sample point and then applying horizontal filtering to all of the results; And And an enhancement step of adding an enhancement element to the obtained luminance signal and color signal to determine a final luminance signal and a color signal. The method of claim 1, wherein the vertical / horizontal filtering step A first vertical filtering is applied to sample points centered on the sample point on the horizontal left of the sample point, a second vertical filtering is applied to the sample points centered on the sample point, and the horizontal of the sample point And a third vertical filtering is applied to the sample points centering on the sample points on the right side. The method of claim 2, wherein the vertical / horizontal filtering step Apply first vertical filtering to three sample points centered on the sample point on the horizontal left side of the sample point, apply second vertical filtering to the three sample points centered on the sample point, and And a third vertical filtering is applied to three sample points centered on the sample points on the horizontal right side of the sample point. 4. The method of claim 2 or 3, wherein the vertical / horizontal filtering step is And applying horizontal filtering to the result values of the first, second and third vertical filtering. 4. The method of claim 3, wherein the enhancement step comprises applying horizontal filtering to the luminance signal at the sample point and the horizontal left and right sample points, and adding the result to the luminance of the sample point to obtain the final luminance signal. Determining the luminance / color signal in the comb filter. The method of claim 3, wherein the enhancement step comprises applying horizontal filtering to the results of the first, second, and third vertical filtering, and adding the result with the color signal of the sample point to determine the final luminance. How to separate luminance / color signal in comb filter.