JPH01245692A - Yc separating circuit - Google Patents

Abstract

PURPOSE:To reduce dot disturbance at a small circuit scale and to obtain the picture of high picture quality by constituting a comb-line filter to the respective upper and lower two lines of three horizontal scanning lines, switching it applyingly and obtaining a chrominance signal. CONSTITUTION:Differential signals B and C are outputted at a first comb-line filter 1 and a second comb-line filter, respectively, on upper two lines and lower two lines among continuous three horizontal scanning, and the correlation of the continuous two horizontal scanning lines outputted by the first comb-line filter is detected by detecting means 8-12. Then, a selecting means 7 selects the output signal B of the first comb-line filter 1 as the chrominance signal when the detecting means 8-12 don't generate a detecting signal and switches to the output signal C of the second tandem filter 2 and selects as the chrominance signal when the detecting signal is generated. Thus, Y/C separating circuit can be constituted simplified and at a small scale, moreover, YC separation can be executed effectively and the picture of high picture quality can be obtained.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a YC separation circuit that is applied to a circuit that processes a video signal and separates a luminance signal and a color (chroma) signal, and particularly relates to a YC separation circuit that is applied to a circuit that processes a video signal and separates a luminance signal and a color (chroma) signal. The present invention relates to a YC separation circuit using an adaptive comb filter that eliminates drag crawl.

[Prior art]

An example of this type of YC separation circuit is one shown in FIG. 4, for example. That is, the subtracter 21 subtracts the signal output from the IH delay line 22 from the input composite video signal, and then passes it through the bandpass filter 23 to extract the color signal.Furthermore, the adder 24 extracts the color signal. The luminance signal can be extracted by subtracting it from the video signal, thereby separating the luminance signal and the color signal. In addition, as another YC separation technology, an adaptive YC separation digital filter (
1981 IEICE General National Conference 1.366)
, Adaptive Contour Compensation Digital Filter (1'J85 National Conference of the Television Society of Japan 15-11), In-field Y/C Minute M Using Adaptive Comb Filter (1986 National Conference of the Television Society of Japan, 15-8), etc. .

First, the first adaptive YC separation digital filter includes two IH delay lines and is configured to adaptively switch separation parameters based on the attributes of the waveform pattern in the horizontal and vertical directions. It has the characteristic of following image changes.

The second adaptive contour compensation digital filter is composed of two IH delay lines and a contour detection circuit. The in-yield Y/C separation circuit is composed of a comb-shaped filter section, a contour detection section, and a filter changeover switch, and can detect dots not only on horizontal lines but also on diagonal contours without deteriorating the resolution. It reduces interference.

[Problem to be solved by the invention]

Y/ using the above first IH delay linear comb filter
Although the C separation circuit improves the horizontal resolution and reduces cross color, complete Y/C separation cannot be performed at the contours of horizontal lines or diagonal lines where the vertical correlation between the two images disappears, and the color signal leaks into the luminance signal. The disadvantage is that a so-called drag crawl occurs.

In addition, the first adaptive YC separation digital filter and the second
When there is no correlation between color signals in the vertical direction, the adaptive contour compensation digital filter can reduce doso I/crawl by switching between a comb filter and a bandpass filter, but the resolution at the time of switching is This results in problems such as a decrease in color and an increase in cross-color interference. Furthermore, since the correlation is detected over 2H and over 2 samples, there is also a drawback that the correlation cannot be detected accurately.

Furthermore, although the intra-field Y/C separation circuit using the third adaptive comb filter can reduce dot interference and obtain high-quality images, it has the disadvantage that the overall circuit becomes complicated and the circuit size increases. .

The present invention was devised in order to eliminate the problems in view of the above-mentioned circumstances, and can be constructed simply and on a small scale, and furthermore, can perform YC separation effectively and obtain high-quality images. It is intended to provide a yc separation circuit.

[Means to solve the problem]

In order to achieve the above object, the present invention provides four first comb filters that output a difference signal between the upper two horizontal scanning lines, and two lower horizontal scanning lines, for three consecutive horizontal scanning lines of a television signal. a second comb-shaped filter that outputs a difference signal between two horizontal scanning lines; a detection means that detects a correlation between two consecutive horizontal scanning lines outputted by the first comb-shaped filter; When the detection means does not generate a detection signal, the output signal of the first comb filter is selected as the color signal, and when the detection means generates the detection signal, the output signal of the first comb filter is switched to the output signal of the second comb filter, and the color signal is changed. and a selection means for selecting the signal.

[Effect]

According to the configuration of the present invention, three consecutive television signals
Difference signals are output from the first comb filter and the second comb filter for the upper two and lower two horizontal scanning lines of the book, respectively, and the first comb filter outputs two consecutive horizontal scanning lines. The detection means detects the correlation between the lines, and the selection means selects the output signal of the first comb filter as the color signal when the detection means does not generate a detection signal, and selects the output signal of the first comb filter as the color signal when the detection means generates a detection signal. The output signal of the filter is switched to the output signal of the second comb filter and selected as the color signal.

〔Example〕

The present invention will be explained based on an embodiment shown in the drawings.

FIG. 1 is a block diagram of the YC separation circuit, FIG. 2 is a waveform diagram for explaining the principle of generation of don't crawl, and FIG. 3 is a waveform diagram for explaining the process of removing don't crawl.

A composite video signal is input to the input end of the YC separation circuit, and first and second comb filters 1.2 are arranged on this input side. Each comb filter 1.2 is each formed by an IH delay line 5 and an adder 6, L
It consists of an H delay line 3 and a subtracter 4 formed by an adder. Signals B and C output from the subtracter 4.6 are supplied to the selector 7. Also, the output signal B from the subtracter 6
is further added to an IH delay line 8 and an adder 9. In the adder 9, the output signal B and the output signal of the LH delay line 8 are added, and the resulting signal is given to the next stage bandpass filter 10, and then to the absolute value circuit IL comparison circuit 12, The signal is applied to the selector 7 as a switching signal through the low-pass filter 13. A comparison reference level is provided to the comparison circuit 12 from the outside, and the output signal of the comparison circuit 12 is also fed-hacked to this comparison reference level. The selector 7 selects and outputs one of the signals B and C based on the switching signal from the low-pass filter 13 and transmits it to the band-pass filter 14 at the next stage. A subtracter 15 subtracts the output signal of the bandpass filter 14 from the output signal of the IH delay line 3. Then, the color (c) signal is taken out at the output end of the bandpass filter 14, and the luminance signal (Y) signal is taken out at the output end of the subtractor 15.

The operation of the YC separation circuit having such a configuration will be explained.

A composite video signal (video signal) is input to the input end of the YC separation circuit. Due to this signal, a difference between any two consecutive horizontal scanning lines appears in the color (chroma) signal B output from the rectangular filter 2.As shown in FIG. At the input end of 5, the horizontal scanning number N, N
Assuming that a composite video signal consisting of 111, N+2, N+3, N+4, and N+5 scanning lines is input sequentially, the color signal B
As, (N+1)-N, (N+2)-(N+1),
(N+3)-(N+2) difference signals are sequentially output. In this case, as shown in a in FIG. 2, horizontal scanning lines N+2 and N
+3, if there is no correlation in the vertical direction, the color signal B
As shown in Fig. 3c, interference with the color signal and interference with the Y signal (door crawl) occur. In order to eliminate such interference b and dot crawl C to the color signal, the Y of the present invention
In the c separation circuit, a selector 7 switches between the color signal c output from the comb filter 1 and the color signal B output from the comb filter 2 under predetermined conditions, and extracts the color signal without interference.

In FIG. 3, A, B, C, D, and E represent the signals of each part of the circuit in FIG. 1, respectively, on the horizontal scanning lines N, N+1, and
. . . are shown in correspondence with N+5. Signal A is IH
The output signals of the delay line 3, B and C, are the color signals output from the comb filter 1.2 described above, D is the output signal of the bandpass filter 10, and E is the luminance signal.

As shown in FIG. 1, the output signal B of the first comb filter 1 is applied to an IH delay line 8 and an adder 9, and the two successive difference signals are added together and sent to a bandpass filter 10, where the signal is It is taken out as a In this signal, as shown in FIG. 3, a waveform d is always generated in response to interference to the color signal B. Therefore, the signal D, that is, the waveform d, can be used as an interference detection flag when interference to the color signal B occurs. The signal is converted into an absolute value by an absolute value circuit 11, and compared with a comparison reference level by a comparator circuit 12 to detect the presence or absence of waveform d. When waveform d is generated, it is passed through a low-pass filter 13 and sent to the selector 7 as a switching signal.
given to. On the other hand, with respect to the color signal B, in the color signal C output from the second comb filter 2, the number of each horizontal scanning line that is subtracted for the same horizontal scanning line increases by 1, as shown in FIG. Therefore, when an interference to the color signal occurs in color signal B, (N+4)-(N
+3) is performed, and no disturbance to the color signal C occurs.

Therefore, when interference to color signal B occurs, this is predicted by the signal and the selector 7 switches the signal to be selected from color signal B to color signal C, thereby causing a dot crawl in the luminance signal. prevent.

As described above, according to the YC separation circuit according to the present invention, in any three consecutive horizontal scanning lines in a composite video signal, at least one of the upper two colors or the lower two colors has a strong correlation. Considering that there are many comb filters, two comb filters 1.2 are configured for each of the upper and lower sides of the three horizontal scanning lines, and YC bone separation is performed by adaptively switching them to obtain color signals. .

〔Effect of the invention〕

As is clear from the above description, according to the present invention, there are two comb filters, a circuit for detecting the occurrence of disturbance to a color signal, and a selection circuit for switching the color signal using the signal output from the detection circuit. As a result, the structure is simple and small-scale, dot crawl can be efficiently eliminated, and interference such as cross color when switching the color signal output from the comb filter can be reduced. .

[Brief explanation of the drawing]

The drawing shows an embodiment of the YC separation circuit according to the present invention,
Figure 1 is a block diagram, Figure 2 is a waveform diagram to explain the principle of dot crawling, Figure 3 is a waveform diagram to explain the process of removing dot crawls, and Figure 4 is a conventional comb. FIG. 2 is a block diagram of a YC separation circuit using a shaped filter. (Brief explanation of drawings showing main parts) 1.2. Comb filter 3.5.8 IH delay line 7 Selector 10.14 Pandopa X filter

Claims (1)

[Claims] Regarding three consecutive horizontal scanning lines of a television signal, a first comb filter outputs a difference signal between the upper two horizontal scanning lines, and a second comb filter outputs a difference signal between the lower two horizontal scanning lines. a comb filter; a detection means for detecting a correlation between two consecutive horizontal scanning lines outputted by the first comb filter;
selection means for selecting the output signal of the comb filter as the color signal, and switching from the output signal of the first comb filter to the output signal of the second comb filter when the detection means generates the detection signal; Y configured with
C separation circuit.