JPH0366877B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a Y/C separation circuit having a function of performing edge enhancement processing on a television video signal to improve image quality.

Hereinafter, the operation of the present invention will be explained in detail together with examples.

(Prior Art) In television receivers and the like equipped with large display devices, an edge enhancement circuit is sometimes added as part of image quality improvement.

The configuration of such an edge enhancement circuit was developed in U.S. Pat.
It is disclosed in No. 94121 and Japanese Patent Application Laid-Open No. 120284/1984.

(Problems to be Solved by the Invention) The above-mentioned conventional edge enhancement circuits all include a large number of filtering circuits, and therefore have a problem of high cost.

(Means for Solving the Problems) A Y/C separation circuit with an edge enhancement function according to the present invention has two cascade-connected circuits that provide a delay time of one scanning line to a television video signal. a Y/C separation unit that includes a scanning line delay circuit and separates a luminance signal and a color signal based on the correlation between adjacent scanning lines while generating an average value of composite video signals before and after one scanning line in an intermediate process; A low-pass filter circuit extracts the low-frequency component of the luminance signal by removing the high-frequency component of the average value of the composite video signal before and after one scanning line generated in the intermediate process of Y/C separation. A subtraction circuit that creates a difference between the low-frequency component of the luminance signal extracted by the pass filter circuit and the luminance signal separated by the Y/C separation section, and the output of this subtraction circuit is used as an edge emphasis signal to perform the Y/C separation. and an adder circuit for superimposing the luminance signal on the luminance signal.
The contour enhancement function is achieved with an extremely simple configuration.

Hereinafter, the operation of the present invention will be explained along with examples.

(Embodiment) FIG. 1 is a block diagram showing the configuration of a Y/C separation circuit having an edge enhancement function according to an embodiment of the present invention.

This Y/C separation circuit includes a Y/C separation section 20,
The contour emphasizing section 30 is also provided.

The Y/C separation unit 20 includes cascade-connected one-scan line delay circuits 21, 22, adders 23, 25, 28,
It is equipped with 1/2 coefficient units 24, 26, a subtracter 25, and a bandpass filter 27, and uses the correlation between the scanning lines of the television video signal supplied to the input terminal IN to convert the luminance signal Y _o and the chrominance signal C. Separate _o .

That is, three adjacent scanning lines are numbered n-1, n, and n+1 in the order of their appearance, and the scanning line output from the one-scanning line delay circuit 21 is taken as a temporal reference, and the number on this scanning line is Composite video signal Y _o
−C _o . The color signal of the composite video signal on the scanning line immediately after being supplied to the one-scanning line delay circuit 21 is inverted in phase from the color signal C _o on the scanning line used as the reference, so Y _o+1 +C _o+ It is expressed as ₁ .

According to the same notation method and considering that the phase of the color signal is reversed between adjacent scanning lines, the composite video signal on the scanning line immediately before being output from the 1-scanning line delay circuit 22 is Y _{o -1} + C _{o -1} .

The composite video signal Y _o+1 +C _o+1 on the immediately previous scanning line,
The composite video signal Y _o-1 + C _o-1 on the immediately following scanning line is
After the adder 23 and the 1/2 coefficient unit 24 obtain the average value (Y _o +C _o ) of the composite video signal before and after one scanning line, the subtracter 25 calculates the actual composite video signal on the reference scanning line. Subtracted by Y _o − C _o .
If the correlation between adjacent scanning lines is large to some extent,
Since Y _o and _Yo are almost equal, and C _o and _Co are almost equal, the output of the subtracter 25 is approximately 2C _o , and the 1/2 coefficient unit 26 outputs a Y/C separated color signal that is approximately equal to _Co. is output. This color signal passes through a bandpass filter 27 having a band center on the color subcarrier, and is separated into Y/C color signals based on the correlation between scanning lines.
It is supplied to the color signal output terminal C as _Co.

On the other hand, the video output Y _o −C _o outputted from the one-scanning line delay circuit 21 is converted to Y/C in the adder 28 .
It is added to the separated color signal _Co and is supplied to the edge enhancement section 30 as a Y/C-separated luminance signal _Yo .

In reality, the luminance signal and the color signal leak into each other to a degree corresponding to the degree of correlation collapse. The bandpass filter 27 having its band center on the color subcarrier functions to remove the luminance signal component leaking into the correlated color signal component.

In parallel with the Y/C separation process in the Y/C separation unit, an edge enhancement process is performed by an edge enhancement unit 30 having an extremely simple configuration consisting of a subtracter 35, a coefficient unit 36, an adder 37, and a low-pass filter circuit 38. will be held.

First, in the low-pass filter circuit 38, Y/C
High-frequency components are removed from the average value (Y _o +C _o ) of the composite video signal before and after one scanning line output from the coefficient unit 24 of the separation unit 20, and only the low-frequency components of the luminance signal are extracted. In other words, the frequency spectrum of a composite video signal consisting of a luminance signal and a color signal is shown in Figure 2A.
2B, the insertion loss of the low-pass filter circuit 27 is set to the characteristics shown in FIG. 2B, and all components of the color signal and high-frequency components of the luminance signal are removed. By doing so, only the low frequency components of the luminance signal are extracted.

The subtracter 35 subtracts the low-frequency component of the luminance signal extracted by the low-pass filter circuit 38 from the separated luminance signal output from the Y/C separator 20, thereby reducing the high-frequency component of the luminance signal. The components are extracted. The high frequency component of this extracted luminance signal is
The signal is multiplied by a coefficient in a coefficient unit 36 and supplied as an edge emphasis signal to one input terminal of an adder 37,
It is superimposed on the Y/C separated luminance signal supplied to the other input terminal.

Of the two luminance signals supplied to each input terminal of the subtracter 35, one has high frequency components removed, and the other also includes high frequency components, so in addition to contour enhancement in the scanning line direction (vertical direction), Contour enhancement in the horizontal direction is also performed at the same time.

(Effects of the Invention) As explained in detail above, the Y/C separation circuit with an edge enhancement function according to the present invention has an extremely simple configuration compared to the Y/C separation circuit according to the prior art described above. , the number of parts and adjustment effort can be reduced, and costs can be reduced.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of a Y/C separation circuit with an edge enhancement function according to a first embodiment of the present invention, and FIG. 2 is a low-pass filter circuit of the edge enhancement section 20 of FIG. 1. 38 is a characteristic diagram showing an example of insertion loss of No. 38. FIG. 20... Y/C separation section, 30... Contour emphasis section,
21, 22...1 scanning line delay circuit connected in cascade, 23, 25, 28, 37... adder, 25,
35...Subtractor, 38...Low pass filter circuit.

Claims (1)

[Scope of Claims] 1. Two one-scan line delay circuits connected in cascade to give a television video signal a delay time of one scanning line each, the average value of the composite video signal before and after one scanning line is Y/C that separates luminance signals and color signals based on the correlation between adjacent scanning lines while generating them during the process.
a separation unit; and a low-pass filter circuit that extracts the low-frequency component of the luminance signal by removing the high-frequency component of the average value of the composite video signal before and after one scanning line generated in the intermediate process of the Y/C separation. , a subtraction circuit that creates a difference between the low-frequency component of the luminance signal extracted by the low-pass filter circuit and the luminance signal separated by the Y/C separation section, and the output of the subtraction circuit as the edge emphasis signal. 1. A Y/C separation circuit having an edge enhancement function, comprising an edge enhancement section comprising an addition circuit that superimposes a Y/C separated luminance signal.