JPH01117494A - Y/c separation circuit - Google Patents

Abstract

PURPOSE:To simply constitute an adaptive comb-line filter without any malfunction by one CCD delay line only by ANDing YL correlation detection chroma detection pulses. CONSTITUTION:A YL correlation output D obtained via a low pass filter(LPF) 11, a detection output E obtained by extracting and detecting a chroma signal in the center of fsc by a BPF 13 are formed to a signal obtained by subtracting a signal VD after 1H from an existing signal and a comb-line filter is controlled by both AND outputs. That is, in controlling the comb-line filter by the YL correlation output only, since trap is set as the non-correlation in case of tilt stripes for example and the deterioration of resolution is incurred, a chroma signal is detected and the existence of the chroma signal in the part regarded to have non-correlation by the YL correlation detection circuit 12 is discriminated and the trap is set only when the chroma signal exists. Thus, the adaptive comb-line filter is realized by one 1H delay line.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for Y/C separation of a composite video signal, and more particularly to a comb filter suitable for Y/C separation of a wideband video signal.

[Conventional technology]

The composite video signal of the NT8C system is 0 to 4, 2.
For luminance signals up to MHZ, color subcarrier frequency fsc
(fsc −-7-fH: fH is horizontal scanning frequency)
The central chroma signal is superimposed in an interleaf relationship. Therefore, in order to separate both signals, conventionally, an SMHz low-pass filter (hereinafter abbreviated as LPF) and an s fsc±50010 (z 11 degree band-pass filter (hereinafter abbreviated as BPF), that is, a one-dimensional filter, have been used. In contrast, recently, the mainstream method has been to separate the luminance signal and chroma signal using a comb-shaped filter using a delay line. The goal is to expand the band while minimizing interference between signals.

However, since the above comb filter performs addition and subtraction of signals around 1H, Y
/C separation becomes impossible (Fig. 3, al, a@, I
)+%b, shown in). Generally, when viewed on a screen, dot interference (disturbance caused when a chroma signal is processed as a luminance signal) and color blurring occur at edges in the vertical direction.

・As shown in Videocom, July 1962 issue, ps3-P57-, the signal that could not be separated by the luminance comb filter is compared, and the detected signal is used to control the comb filter, and the vertical edge A method for removing dot interference and color bleeding has been reported. In the uncorrelated part, the luminance comb filter output [fsc trap is turned on, and the chroma output is switched to the current signal. The conventional method for detecting uncorrelated parts is to use a chroma comb filter to extract the chroma signal (the cause of vertical dot interference) contained in the output of the luminance comb filter, detect it, and then obtain the uncorrelated detection signal. It's something you get. That is, it detects components that cause interference and controls the comb filter.

[Problem that the invention seeks to solve]

The above conventional technology has extremely good performance due to the force (Y/C
In addition to using a 1H delay line for the separation comb filter, another 1H delay line was required for the non-correlation detection circuit, which led to further problems in increasing costs.

An object of the present invention is to realize an adaptive comb filter with one 1H delay line.

[Means for solving problems]

The above purpose is to firstly apply the YL correlation obtained through the LPF to the signal obtained by subtracting the signal after 1H from the current signal (detect the presence/absence of correlation in the vertical direction using only the low-frequency components of the luminance signal). This is achieved by extracting the chroma signal at the center of fsc with the second KBPF', creating a detection output by detecting it, and controlling a comb filter with the AND output of both.

[Effect]

If the comb filter is controlled using only the YL correlation output, for example, in the case of inclined fringes, it will be uncorrelated and the trap will be turned on, resulting in resolution deterioration. Therefore, in order to prevent this malfunction, the chroma signal is detected and the YL correlation detection circuit determines that the chroma signal exists in the part that is considered to be uncorrelated.
I used a trap method that turns on only when the Chroma 1 word is M.

〔Example〕

An embodiment of the present invention will be explained below with reference to FIG. 1st
The figure shows a block diagram of the adaptive comb filter of the present invention. 1 is the video input terminal, 2 is the CCD (Charge
Couphed Device-e) 1H delay line, 3.4 is the subtracter, 5 is the BPF, 6 is the chroma switch, 7 is the fsc) wrap, 8 is the switch, 9 is the brightness signal output terminal, 10 is the chroma signal output Terminal, 11 is LPF
, 12 is a YL correlation detection circuit, and 13 is a BPF.

14 is a chroma detection circuit, 15 is an AND gate, and 16 is a non-correlation detection circuit. Figure i3 shows the waveforms of each part. As is well known, the comb filter is formed by adding and subtracting the current signal (V) and the signal after 1H (VD). To extract the chroma signal, subtract the signal (VD) after 1H from the current signal (V) by 3, and multiply by BPF"5.
(A signal like the one shown in () is obtained.

The subtracter 4 extracts the chroma signal (C+) from the current signal (V).
) t', the luminance value (Y, ) is obtained.

It can be seen that perfect separation is not possible in the places where there is no correlation between the signals before and after 1H in the μ portions of al, al and duck, b shown in (Y,) and (C8). Since the luminance signal (Y,) remains at A, a becomes a dot disturbance at the vertical edge. This causes vertical edges 19 to appear on the monitor 17, as shown in FIG. Furthermore, the center of gravity of the chroma signal (CI) is shifted by α5H with respect to the luminance signal (Y, ), resulting in color blur.

In order to prevent these, the trap 7 is turned on with the switch 8 for the luminance signal (Y,), and the dot interference collection a@
S al is removed to obtain a complete luminance signal (Y,), and as a chroma signal, a switch 611tb (XIVc is connected and a chroma signal (C
, ) is what you get. The non-correlation detection circuit 16 for obtaining the signal (F) for controlling the switches 8 and 6 will be described below. The low-frequency component of the output (V-VD) of the subtracter 3 is extracted by the LPP11, and the YL correlation detection circuit 12 performs processing such as full-wave rectification to obtain a pulse CD).

Further, only the chroma component is extracted from (V-V'n) by the BPF 13, and the chroma detection circuit 14 performs processing such as detection to obtain a chroma detection pulse (E). Pulse CD above)
The AND gate 15 performs the logical product of and (E) to obtain the output CF).

For example, if switch 8 is controlled only by the output CD of the YL correlation detection circuit, as shown in 18 in Figure 2, it will be determined that the luminance signal is uncorrelated in the diagonal striped area and the trap will be turned on. This leads to a deterioration in resolution. At this time,(
As shown in F2), the chroma detection circuit detects the presence/absence of the chroma signal.
It looks for nothing and turns on the trap only when a chroma signal is present.

Therefore, it is possible to prevent malfunctions caused by black and white signals.

FIG. 4 shows a specific block diagram of the decorrelation detection circuit 16 of FIG. 1. Signal input from terminal 20 (Y-YD
) is applied with LPF 21, and it is full-wave rectified with 22,
A detection pulse (D) is obtained by comparing with a base 1% DC voltage (Vrefl) using a humpator 23. In addition, for the chroma signal extracted by the BPF27, burst Ace (A
Auto Co1or Control) 2 B is applied, the output is detected, and compared with the reference DC voltage Vre f 2 by the humpator 32, and the chroma detection pulse (E) is detected.
&obtain.

25 is an AND gate and corresponds to FIG. 15.

FIG. 5 shows the bands of the LPF 21 and BPF'27.

35 shows the band of the LPF 21, and 36 shows the band of BpH'27. ◎As the band of the BPF 27, fsc*500KHz 8F, which is the chroma signal band, is selected. LPF
When the '55 band overlaps with the BPF27 band, resolution deteriorates because high-frequency components of brightness are detected and the trap is turned on/off. Therefore, the band of LPF35 is BPF
! Set the cutoff frequency to 2MHz so that it does not overlap with 6.
It is necessary to select a location nearby.

〔Effect of the invention〕

According to the present invention, by taking the logical product of s YL, correlation detection pulse, and chroma detection pulse, it is possible to easily construct an adaptive comb filter without malfunction using only one delay line (CCl). A low-cost η°C isolation circuit can be realized.

[Brief Description of the Drawings] Fig. 1 is a block configuration diagram showing an embodiment of the present invention, Fig. 2 is a schematic diagram showing a monitor image, Fig. 5 is a timing chart diagram, and Fig. 4 is an embodiment of the present invention. Block configuration diagram shown,
FIG. 5 is a diagram showing the band of the filter. 2..., CCD1H delay line, 7... fsc) wrap, 12... YL correlation detection circuit, 14... chroma detection circuit, 15... AND gate.

Claims (1)

[Claims] 1. When separating a composite video signal in which a luminance signal and a chroma signal are frequency multiplexed in an interleaf relationship into a luminance signal and a chroma signal using a comb filter using a 1H delay line, the current signal V and the signal after 1H are separated. V_D difference signal (
A first signal obtained from the low frequency component of (V-V_D);
means for obtaining an AND with a second signal obtained by detecting the chroma component in V-V_D), a switch for turning on a trap for the luminance comb filter output using the AND signal, and a chroma comb filter. A Y/C separation circuit characterized by being equipped with a switch for switching the output to the current signal.