JPH0361398B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention provides a Y/C separation device that separates a luminance signal (hereinafter referred to as Y signal) and a color signal (hereinafter referred to as C signal) from an NTSC video signal. In particular, it relates to a device with a vertical contour function added.

[Conventional technology]

The sharpness of a TV image is one of the factors that determines the picture quality.
However, for this purpose, various means have been used to perform contour compensation or enhancement. In the case of horizontal edge enhancement, it is sufficient to simply superimpose the high frequency component of the luminance signal extracted by a high-pass filter onto the original signal, but in the case of vertical edge enhancement, the circuit configuration becomes complex.

Figure 3 shows an example of this, in which the Y _o+1 signal separated by the Y/C separation circuit 1 is led to the cascaded 1H delay elements 2 and 3, and the output Y _o-1 signal of the 1H delay element 3 is connected to the adder 4. After adding, multiply by 1/2 using coefficient unit 5, and calculate the arithmetic average _o
The signal is obtained, and the subtracter 6 calculates the difference between the signal and the Y _o signal at the midpoint (the current point). This differential ΔY _o signal is used as a vertical contour emphasizing signal, and is multiplied by an appropriate coefficient K by a coefficient unit 7 to obtain KΔY _o , which is added to the _Yo signal.

The above contour-enhanced (Y _o +K△Y _o ) signal,
The C _o+1 signal output from the Y/C separation circuit 1 is delayed by the 1H delay element 9, and the C _o signal is input to the subsequent matrix circuit. The above circuit requires three 1H delay elements, an adder, a subtracter, a coefficient unit, etc., and even if it is provided to improve image quality, an increase in cost cannot be avoided.

[Problem that the invention seeks to solve]

By the way, as a Y/C separation method, a method of separating video signals on the time axis by utilizing the correlation between adjacent scanning lines (hereinafter referred to as a correlation separation method) is well known. As a circuit configuration of this system, there is one in which 1H delay elements are connected in cascade and the signals of each part of this string are combined. Since the vertical contour enhancement circuit also uses the cascade connection of 1H delay elements,
If the main parts of the Y/C separation circuit can be used as is to have a vertical contour enhancement function, the cost increase of providing a separate circuit for vertical contour enhancement can be avoided.

SUMMARY OF THE INVENTION An object of the present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to provide an apparatus in which a vertical contour enhancement function is added to a Y/C separation apparatus.

[Means for solving problems]

The device of the present invention includes a first delay circuit that inputs a composite video signal l _{o +1} and outputs a signal l _o that is delayed by one horizontal scanning period; a second delay circuit that outputs a signal _lo-1 ; and outputs a first difference signal ( _lo −lo+1) from the composite video signal _lo+1 , the signal _lo and the signal _{lo- 1.} and a second subtractor that outputs a second difference signal (l _o −l _o-1 ), the composite video signal l _o+1 and the signal l of the three horizontal scanning periods. _o and a Y/C separator that separates a luminance signal and a color signal from the signal l _o-1 , the first difference signal and the second difference signal are added and low-pass filtered to obtain a vertical contour. a vertical edge enhancement signal generation circuit that outputs an enhancement signal; a level adjustment coefficient unit that weights the vertical edge enhancement signal with a predetermined coefficient and outputs the resultant signal; It is equipped with an adder that adds to the signal.

〔Example〕

Hereinafter, one embodiment of the present invention will be described with reference to the drawings. The Y/C separation device may be of any type as long as it uses two cascaded 1H delay elements and utilizes the correlation between three adjacent scanning lines, or includes a portion that takes such a correlation. A typical correlation separation method circuit is shown in 1 in Figure 1.
It is as shown by 0. This circuit is called a 2H type, and uses two delay elements 11a and 11b to separate Y and C signals by combining signals at each node. The midpoint is the current signal l _o , and the previous signal
When l _{o -1} is subtracted by subtractor 13b, l _o = Y _o +
As C _o , l _o-1 = Y _o-1 −C _o-1 (a negative sign is added to take into consideration the phase of C), l _o −l _o-1 = (Y _o −Y _o-1 ) ＋C _o
+C _o-1 , and if the correlation between the signal l _o and the signal l _o-1 is strong, this difference signal will be approximately 2C _o . Similarly, the difference signal (lo _{- lo+1} ) of the subtractor 13a also becomes approximately _2Co . The outputs of the subtracters 13a and 13b are sent to the adder 14.
When the signals are added together and multiplied by 1/4 by the multiplier 15, the C signal is obtained. Further, by subtracting the C signal from the signal _lo by the subtracter 16, the Y signal is obtained. An edge enhancement section 100(1) is added to the Y/C separation circuit 10.
The contour enhancement section 100 (1) is a low-pass filter 10
1. Level adjustment coefficient unit 103, coefficient setter 10
4. Consists of an adder 105, and an adder 14
and the low-pass filter 101 constitute a vertical contour emphasizing signal generation circuit.

The operation of the contour emphasizing section 100(1) will be explained below. Adder 14 in Y/C separation circuit 10
If the signals lo ₊₁ , _lo , _{and lo-1} are perfectly correlated, the output of the C signal will be four times that of the C signal. However, if the intensity of adjacent scanning lines is different in an image in which the correlation is broken, the outputs 14A and 14B of the adder 14 include a difference signal between the Y signal in addition to the C signal. The present invention
This method actively utilizes this difference signal corresponding to the differential characteristic to emphasize vertical contours. Since the cutoff frequency of the low-pass filter 101 is determined so as to remove the frequency band in the vicinity including the C signal, its output becomes ΔY corresponding to the differential amount of Y, and becomes a vertical contour emphasizing signal. This signal is sent by the level adjustment coefficient unit 103 to the adder 105 as KΔY. The coefficient K is determined by the coefficient setter 104.

As described above, a relatively simple contour emphasizing section 100(1) is added to the Y/C separation circuit 10, and the Y/C
Contour enhancement can be performed by receiving an appropriate signal within the separation circuit 10. Note that even if the circuit configuration is such that the multiplier 15 is included in the adder 14, it is only necessary to change the coefficients appropriately using the coefficient setter 104.

Next, as another Y/C separation device, a case where the present invention is applied to Japanese Patent Application No. 60-232528 ``Y/C separation device for color television signals'' of which the present inventor is one of the co-inventors will be described. This device consists of a Y/C separation circuit using a correlation separation method using temporal correlation, a Y/C separation circuit using a frequency separation method using a frequency filter, and the luminance and color signals received from each of these Y/C separation circuits. It has a combining means for weighting and combining each of the signals, and a means for detecting a vertical change component and changing the weighting according to the magnitude of the detected component.

FIG. 2 is a circuit block diagram in which the present invention is applied to the separation device described above and an edge enhancement section 100(2) is added. 10 is a correlation separation type Y/C separation circuit, which is the same as the circuit shown in FIG. Reference numeral 20 is a Y/C separation circuit of frequency separation type, and outputs Y ₁ , C ₁ and Y ₂ , C ₂ of both Y/C separation circuits 10 and 20 are shown.
The signals are weighted and combined for each Y signal and C signal in a combining circuit 30. Synthesis circuit 3
The coefficients of the coefficient circuits 31 to 34 that carry out weighting of 0 are determined by the synthesis control circuit 70. The inputs of the synthesis control circuit 70 are a color signal horizontal component detection circuit 40, a luminance signal horizontal component detection circuit 50, and a vertical component detection circuit 6.
The output is 0. By combining the magnitudes of the outputs of the circuits 40, 50, and 60, the mixing ratio of the Y ₁ and C ₁ signals and the Y ₂ and C ₂ signals is changed to appropriately suppress cross color and dot crawl.

The contour emphasizing section 100(2) is almost the same as the contour emphasizing section 100(1) of FIG. 1, but the low-pass filter 101 is replaced with an adder 102. The inputs of the adder 102 are the respective output signals of the low-pass filters 51 and 52 on the input side of the luminance signal horizontal component detection circuit 50. The signal input to the low-pass filters 51 and 52 is Y/C.
These are the output signals of the subtraction circuits 13b and 13a in the separation circuit 10. In FIG. 1, the vertical contour emphasizing signal generation circuit is composed of an adder 14 and a low-pass filter 101.
While the color signal component is removed by one low-pass filter 101 on the input side of 00(1), in FIG. The color signal components are removed from the outputs of the subtracting circuits 13b and 13a by low-pass filters 51 and 52, respectively, and then added by an adder 102. Therefore, they are operationally identical. However, there is an advantage that the low-pass filters 51 and 52 can also be used for contour enhancement.

〔Effect of the invention〕

As explained in detail above, in a Y/C separation device including separation means that utilizes the correlation between three scanning lines, a signal generated within the Y/C separation device is used to convert an edge enhancement signal into an outline image with a simple configuration. By creating this in the enhancement section and adding it to the separated Y signal, an image with high sharpness can be obtained.

[Brief explanation of drawings]

1 and 2 are circuit block diagrams showing an embodiment of the present invention, and FIG. 3 is a diagram showing a circuit in which an edge enhancement circuit is provided separately from a Y/C separation device. 10...Y/C separation circuit (correlation separation method), 1
1a, 11b...1H delay element, 13a, 13b,
16...Subtractor, 14...Adder, 20...Y/
C separation circuit (frequency separation method), 30... synthesis circuit, 50... luminance signal horizontal component detection circuit, 51,
52...Low pass filter, 100(1), 10
0(2)... Contour emphasis unit, 101... Low pass filter, 102... Adder, 103... Level adjustment coefficient unit, 104... Coefficient setter, 105... Adder.

Claims (1)

[Claims] 1. A first delay circuit that inputs a composite video signal l _o+1 and outputs a signal _{l o delayed} by one horizontal scanning period; signal
a second delay circuit that outputs l _o-1 ; and outputs a first difference signal (l _o −l o+1) from the composite video signal l _o+1 , the signal l _o , and the signal l _{o- 1.} a first subtracter and a second subtracter that outputs a second difference signal (lo _{- lo-1} ), the composite video signal lo ₊₁ of the three horizontal scanning periods;
A Y/C separation device that separates a luminance signal and a chrominance signal from the signal lo and the signal _lo-1 , adds the first difference signal and the second difference signal _, and low-pass filters the signal. a vertical edge enhancement signal generation circuit that outputs a vertical edge enhancement signal; a level adjustment coefficient unit that weights the vertical edge enhancement signal with a predetermined coefficient and outputs the resultant signal; What is claimed is: 1. A Y/C separation device having an edge enhancement function, characterized in that it is equipped with an adder for adding to a luminance signal.