JPH08256356A - Y/c separator - Google Patents

Abstract

PURPOSE: To suppress cross color while ensuring the color of transient by providing a Y/C separator circuit, a frame memory, a correlation detection circuit and applying band limit to a color signal in response to the result of the correlation detection circuit. CONSTITUTION: An in-field Y/C separator circuit 2 obtains vertical correlation and a comb-line filter is used to conduct Y/C separation when vertical resolution is in existence. When no vertical resolution is in existence, a horizontal BPF is used to conduct Y/C separation. The obtained color signal is given to a frame memory 3, delayed by one frame and then the result is outputted. Then the input and output of the memory 3 is given to a correlation detection circuit 4, then the correlation of color signals between frames is found. Based on the result of detection of this circuit 4, a color band limit circuit 5 limits the band to the color signal output of the circuit 2. That is, it is discriminated that cross color is in existence when the result of detection of the circuit 4 is larger to make the color band narrow and when no cross color component is in existence, the band is left wide.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a Y / C separation device for separating a composite color television signal into a luminance signal and a carrier color signal in a television receiver, for example.

[0002]

2. Description of the Related Art In recent years, with the development of digital signal processing technology, in a Y / C separation device for separating a composite color television signal into a luminance signal and a carrier color signal, a signal of interest and a point near the vertical or time axis direction. There is used an adaptive luminance signal / color signal separation device that selects a plurality of filters according to the presence or absence of correlation with. For example, as a conventional example of adaptive Y / C separation, Japanese Patent Laid-Open No. 4-63089 discloses Y / C.
As a C separation device, a motion adaptive luminance signal / color signal separation filter is shown in Japanese Patent Laid-Open No. 3-243089.

As a first conventional example, JP-A-4-63089
FIG. 2 shows a block diagram of a Y / C separation device according to the publication. In FIG. 2, 201 is an input composite color television signal, 202 is a first delay device that delays the composite color television signal, and 203 is a first BP that extracts a subcarrier frequency from the composite color television signal.
F and 204 are comb filters that extract color signal components from the output of the BPF by using signals of a plurality of scanning lines, 20
Reference numeral 5 is a second BPF for band-limiting the output of the comb filter and outputting a color signal. Reference numeral 206 is a subtractor for subtracting the output of the comb filter from a signal obtained by delaying a composite color television signal to obtain a luminance signal. , 207 are second delay devices that delay the obtained luminance signal so as to match the time with the color signal. The operation of the conventional Y / C separation device configured as described above will be described. The input composite color television signal is extracted by the first BPF 203 only in the vicinity of the subcarrier frequency. Then comb filter 20
At 4, the color signal is obtained by calculation in the vertical direction. That is, in the NTSC system, the phase of the color signal is inverted line by line, so when the output of the BPF 203 is subtracted between lines, the luminance signal near the subcarrier is canceled,
Only the color signal component is extracted. After that, the color signal is the second B
The band is limited to a narrow band by the PF and output.

As a second conventional example, Japanese Patent Application Laid-Open No. 3-24308
FIG. 3 shows a block diagram of the Y / C separation device according to Japanese Patent Laid-Open No. 9. In FIG. 3, 301 is an input composite color television signal, 302 is an intra-frame Y / C separation circuit that performs Y / C separation within a frame, and 303 is Y / C separation between frames using frame correlation. Inter-frame Y / C separation circuit, 304 is a luminance signal motion detection circuit for obtaining correlation between luminance signal frames, 305 is a color signal motion detection circuit for obtaining correlation between color signal frames, and 306 is the luminance signal motion detection circuit. And a synthesizing circuit for judging whether it is a moving image or a still image based on the result of the color signal motion detection circuit, and 307 is a luminance signal output from the in-frame Y / C separation circuit and Y / C between frames
A luminance signal mixing circuit that mixes the luminance signal output from the separation circuit based on the motion determination result of the synthesizing circuit, and 308 is the color signal output from the intra-frame Y / C separation circuit and the inter-frame Y / C.
A color signal mixing circuit that mixes the color signals output from the separation circuit based on the motion determination result of the combining circuit. The operation of the second conventional example of the Y / C separation device configured as described above will be described. In the input composite color television signal, the correlation between the low frequency component (luminance signal component) frames is detected by the luminance signal motion detection circuit. Further, the color signal motion detection circuit detects the inter-frame correlation of the subcarrier frequency component (color signal component). Judgment is made from these two types of correlation to determine whether it is a moving image or a still image. In the case of a still image, since there is a correlation between frames, the Y / C separation circuit between frames can perform complete Y / C separation. In the case of a moving image, intraframe Y / C separation is performed because there is no correlation between frames. Optimal Y / C separation is possible by changing Y / C separation for moving images and still images.

[0005]

However, with the above-mentioned configuration, in the first conventional example, Y / C separation cannot be performed correctly when there is no vertical correlation, and cross color and dot interference are conspicuous especially in a still image. Will end up. BPF here
When the band is limited to a narrow band at 205, the cross color becomes inconspicuous, but the color transient becomes worse, and the color boundary of the color bar, for example, becomes unclear. Also,
In the second conventional example, complete Y / C separation can be realized in a still image, but three-dimensional Y / C separation is not suitable for some devices such as master monitors for broadcasting business because of time delay. Therefore, there was a problem that it could not be applied.

In view of the above problems, the present invention provides a Y / C separation device capable of suppressing cross color while securing color transients.

[0007]

In order to solve the above problems, a Y / C separation device of the present invention receives a composite color television signal as an input and separates the composite color television signal into a luminance signal and a carrier color signal. The in-field Y / C separation circuit, the frame memory for storing the color signal output from the Y / C separation circuit for one frame period, and the color signal output from the color signal and the frame memory delayed by one frame. A correlation detection circuit for detecting the correlation with a signal and a color band limiting circuit for limiting the band of the color signal according to the result of the correlation detection circuit are provided.

[0008]

The present invention can realize a Y / C separation device capable of suppressing cross color while securing a color transient with the above configuration.

[0009]

EXAMPLE An example of the present invention will be described below (FIG. 1).
Will be explained.

FIG. 1 is a block diagram of a Y / C separation device according to the first embodiment of the present invention.

In FIG. 1, 1 is an input composite color television signal, and 2 is a composite color television signal adaptively switching between a comb filter and a horizontal BPF based on vertical correlation. To output the Y / C separation circuit in the field, 3 is a frame memory that delays the color signal output from the Y / C separation circuit in the field by one frame, and 4 is a cross color based on one frame correlation of the color signal. A correlation detection circuit for extracting components, 5 is a color band limiting circuit for limiting the band of the Y / C separated color signal based on the result of the correlation detection circuit, 6 is a Y / C separated luminance signal output, Reference numeral 7 is a color signal output that is Y / C separated and cross-color suppressed. The operation of the Y / C separation device configured as described above will be described below with reference to FIG.

First, the input composite color television signal 1
Is separated into a luminance signal and a chrominance signal by the in-field Y / C separation circuit 2. The intra-field Y / C separation circuit 2 obtains vertical correlation, and if there is vertical correlation, Y / C separation is performed by a comb filter, and if there is no vertical correlation, horizontal B
Y / C separation is performed by PF. The obtained color signal is input to the frame memory 3, delayed by one frame, and output. After that, the input and output of the frame memory 3 are input to the correlation detection circuit 4. The correlation detection circuit 4 finds the correlation between the frames of the color signal. Originally, the phase of the color signal is inverted every frame. If the Y / C separation is performed correctly, the phase relationship of the color signal over one frame is correctly inverted, but if there is no vertical correlation or if the vertical correlation is not detected correctly, cross color results. Since the cross color component is originally a luminance signal component, the phase relationship between one frame is the same. The correlation detection circuit 4 detects the magnitude of the correlation by obtaining the addition of the color signals during this one frame. 0 for color signals,
In the case of cross color, the level corresponding to the original luminance signal is detected. Based on the detection result of the correlation detection circuit 4, the color signal output of the intra-field Y / C separation circuit 2 is band-limited by the color band limiting circuit 5. That is, the larger the detection result of the correlation detection circuit 4, the more the cross color is determined, and the color band is narrowed. If there is no cross color component, the band remains wide. The color band is changed according to the detection value of the correlation detection circuit 4. By doing so, it is possible to suppress cross color while securing a color transient.

[0013]

As described above, according to the present invention, an in-field Y / C separation circuit for receiving a composite color television signal as an input and separating the composite color television signal into a luminance signal and a carrier color signal; A frame memory that stores the color signal output from the / C separation circuit for one frame period;
A correlation detection circuit for detecting a correlation between the color signal and a signal obtained by delaying the color signal output from the frame memory by one frame; and a color band limiting circuit for band limiting the color signal according to the result of the correlation detection circuit. By providing the above, it is possible to suppress cross color while securing a color transient.

[Brief description of drawings]

FIG. 1 is a block diagram of a Y / C separation device according to a first embodiment of the present invention.

FIG. 2 is a block diagram of a conventional Y / C separation device in a first example.

FIG. 3 is a block diagram of a Y / C separation device according to a second conventional example.

[Explanation of symbols]

 1 Composite Color Television Signal 2 In-Field Y / C Separation Circuit 3 Frame Memory 4 Correlation Detection Circuit 5 Color Band Limiting Circuit 6 Luminance Signal 7 Color Signal 201 Composite Color Television Signal 202 Delay Device 1 203 BPF1 204 Comb Filter 205 BPF2 206 Subtractor 207 Delay device 2 301 Composite color television signal 302 In-frame Y / C separation circuit 303 Inter-frame Y / C separation circuit 304 Luminance signal motion detection circuit 305 Color signal motion detection circuit 306 Synthesis circuit 307 Luminance signal mixing circuit 308 Color signal mixing circuit

Claims (1)

[Claims] 1. An in-field Y / C separation circuit which receives a composite color television signal as an input and separates the composite color television signal into a luminance signal and a carrier color signal;
A frame memory that stores the color signal output from the C separation circuit for one frame period; and a correlation detection circuit that detects the correlation between the color signal and the signal obtained by delaying the color signal output from the frame memory by one frame. A Y / C separation device comprising: a color band limiting circuit that limits the band of the color signal according to the result of a correlation detection circuit.