JPS60165889A - Applicable comb line filter for separating luminance signal and chrominance signal - Google Patents

Abstract

PURPOSE:To reproduce a beautiful received picture whithout cross color or dot interference by using a signal of a direction of which waveform in a vertical direction and horizontal direction of a composite color television signal slowly change, and by constituting a separating filter to separate a luminance signal from a chrominance signal. CONSTITUTION:A sampling signal series S (m, n) of a sampled composite color television signal simultaneously outputs five diamond latice shaped sampled points through two pairs of variable line delay circuit 5 and a dot delay circuit 6. A comparison decision circuit 9, in order to decide to select either of them by an output signal group of each directional separating filter, compares a differencial absolute value with respect to each of two upper/lower and right/left group picture element signals of S (m, n) and switches a selector 10 to select a less-change directional separating filter output. A filter for separating a luminance signal and a chrominance signal detects a direction whose waveform is steep and less changed by using four picture element signals in vertical horizontal directions where the phase of a chrominance sub-carrier becomes identical, and separates the luminance signal from the chrominance signal by using the picture element signal of the direction whose waveform is less changed.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a luminance signal and chrominance signal separation filter for separating luminance signals and chrominance signals from a standard composite color television signal.

In the current color television standard system, brightness information and color information are sent as a frequency-multiplexed composite signal, so the receiver must correctly separate this information into brightness signals and color signals.

NTSO composite color television signal S.

It is a composite signal of a luminance signal Y and a color signal C obtained by quadrature two-phase modulation of two color difference signals Uk and V (or Uk and Q) at a color subcarrier frequency fsc.

S=Y+O=Y+Us stone (2πfsct)”Vm(2π
fsot) Frame frequency 11 fF (30 Hz), field frequency fv.

There is a relationship of = 455 525 f, = 455, 525f.

Therefore, when an NTSO composite color television signal is synchronously sampled at a sampling frequency fs that is four times the color subcarrier frequency fBc, the sampled signal sequence is
Take a two-dimensional array as shown in the figure. That is, the phase of the color signal C is inverted by 1800 for each line, and four samples are extracted in one cycle of the color subcarrier.

Furthermore, the pAL composite color television signal P is 9
If the color subcarrier frequency f'Bc is PBY+Ul+In
(2πflsot) ±V cos (2πflsot)
It is expressed as Switching on the sign is + on even scan lines.

It becomes - for odd numbered scanning lines. That is, the V component is inverted for each scanning line.

Frame frequency f'p (25H2), field cylinder wave number f, horizontal scanning frequency fH, then 1 1 1, l + f '5c - (2844 = 625) fH = (28
44+625) ・625, 1l --fv= (284-7+=)-625f'.

There is a relationship between That is, the color subcarrier frequency f'[]c and the horizontal scanning frequency fH have a seven-line offset relationship. For this reason, the PAL composite color television signal is processed at a sampling frequency f18, which is four times the color subcarrier frequency f'Bc.
The sampled signal sequence sampled by JrA at
Take a two-dimensional array as shown in the figure. That is, the color signals having the same phase are repeated every four lines.

To achieve compatibility with black-and-white television signals, a receiver accurately converts a luminance signal Y and a chrominance signal C from a composite color television signal that includes a color signal that is frequency-multiplexed so that the spectrum is frequency interleaved within the band of the luminance signal. A Y&O separation filter is required to separate the .

An example of the configuration of a conventional luminance signal/chrominance signal separation filter of this type is shown in FIG.

In the figure, (I) is a 1-line delay circuit, (2) is a vertical filter, (3) is a horizontal bandpass filter, +41
i1: Subtractor.

First, the operation of the filter for an NTEIO composite color television signal will be explained.

Composite color television input signal sequence 0 sampled synchronously with the color subcarrier at sampling frequency f8=4·f'sc
01) becomes a two-dimensional grid-like array on the screen like the first south. Now, two transformations are used as symbols to represent a delay of one sample and a delay of one line as z-1 and z-l. Here z-'-exp(-j2yrf/, f8o)5
It is 5. Also, since ff3o=TfH, /=910. At this time, a 1-line delay signal (102) and a 2-line delay signal (103) delayed using a set of two 1-line delay circuits (1) and the current input signal (101) are input to a vertical filter (2). A line alternating signal (104) is extracted for each line including the color signal.

The transfer function Hv(Z) of the vertical filter 21 is Hv(
Z)=(1-z-')2 That is, assuming that the television signals are similar between neighboring pixels, the coordinate (m) is calculated on the first drawing plane.

n) line alternating signal H8(m,n) Hc(m,n)=-7(8(m,n-1>-28(m
, n-1)+E(rn, n+1>1. Since the line alternating signal H8 also includes the luminance signal Y,
The horizontal band pass filter (3) separates the color signal 0 (m, n) f: H (B (m, n), which is a high frequency component. The color signal (105) is simultaneously sent to the subtracter (4). sent,
1 line delay signal (102) to Y (m, n) =
S(m,n)-C! Luminance signal Y as (m, n)
Used to separate (m,n) (1o6).

Transfer function Hh of the horizontal bandpass filter 3)
(z) is, for example, Hh(Z)=-ku(1-z-2)(1+z-')(t+
z-8)2.

Next, the operation of the filter for a PAL composite color television signal will be explained.

Sampling frequency f'S-4f,. l/(composite color television input signal sequence sampled synchronously to the color subcarrier (
101), in the PAL system, the phases of color signals are arranged on the screen as shown in FIG. In other words, the phase of one color signal is 4
For even lines, the color signal component whose color subcarrier phase changes by 180 degrees corresponds to the previous line, and for odd lines, the color signal component whose phase changes by 180 degrees corresponds to the next line. Therefore, the PAL 4-line alternating signal H1 corresponding to the NTSO line alternating signal (104) is obtained by the signal processing of the vertical filter (21).
To obtain o, switch the operation between odd and even lines; 0 odd lines; H'. (m, 2n-1)='(P(
m, 2n-1) - P(m, 2n)) 1' Even line: H'o(m, 2n) - 7(P(m, 2n
)-P(m, 2n-1)), that is, extract the alternating signal (104) using the upper and lower sample points that form a set of every 2 lines,
Color signal 0 through horizontal band pass filter 13+
Take out (m, n).

Conventional luminance signal/color signal separation filters are constructed by combining fixed vertical filters and horizontal filters as described above, and in addition, nine pixels, which are the sampling series of television signals, are adjacent on the screen. It was established on the assumption that things are similar.

Therefore, in the conventional method, in areas where the brightness and color of the image change drastically, the brightness signal and the color signal leak into each other's channels, resulting in blurring of the reproduced image such as dot interference due to the cross color r<. There are drawbacks.

This invention was made to eliminate these drawbacks, and it detects the attributes of a composite television signal waveform in a small area and adaptively switches the vertical filter and horizontal filter to obtain accurate brightness information. The object of the present invention is to provide a luminance signal color signal separation filter that separates luminance signal and color information.

FIG. 4 is a block diagram showing an embodiment of the adaptive luminance signal/chrominance signal separation comb filter according to the present invention.

In the figure, (5) is a variable line delay circuit, (61 is a dot delay circuit, (7) is a vertical separation filter, (8) is a horizontal separation filter, (9) is a comparison decision circuit, and (11 is a selector). In the figures, parts with the same reference numerals indicate the same or equivalent parts.

First, the operation of the separation filter according to the present invention for an NTSO composite color television signal will be explained.

A sampled signal sequence (101) of a composite color television signal sampled at a sampling frequency fS = 4fso is transmitted in a diamond grid pattern on one screen through two sets of variable line delay circuits (5) and a dot delay circuit (61). The variable line delay circuit (5) and the dot delay circuit (6) simultaneously output the five sample points of z-('-2) and z-2.
Perform a delay. At this time, the configuration of the five sample points is as follows when the composite color television signal B (m, n) at the coordinates (m, n) appears on the signal line at (1oe) on the screen in FIG. Upper and lower pixel signals S (m, n-1) (11
o) and S (m, n+1) (101), and left and right pixel signals s (m-2, n) (109) and S (m+2.11) (107) two samples apart. At this time, the phases of the color subcarriers of the other four composite color television signals differ by 180 degrees from S (m, n), so the vertical separation filter (7) and horizontal separation filter (8) are as follows. In processing, the luminance signal and color signal of each direction component are separated.

Vertical separation filter; Yy (m, n) = ± (E + (m, n-1) + 28 (m,
n) + S (m, n + January Cy (m + n) = -'
(S(m+n1)-28(m+n)"
S(m+n+1)) horizontal separation filter; Ch(m,n)=-'(S(m-2,n)-28(m,
n)+S(m+2.n)) Signal output Yv(m,n)(1u) of the separation filter in each direction.

Oy (m, n) (112), Yh (m, n) (113)
and Oh(m,n) (114) are sent to selector four. Here, in order to decide which of the output 1g sets of the separation filters in each direction to select, the comparison and decision circuit (9) calculates the difference between the two sets of pixel signals on the upper and lower sides and the left and right sides of B(rn, n). The selector O1 is switched so as to compare the absolute values and select the output of the separation filter in the direction with the least change.

That is, Is(m-z,n)-8(m+2.n)l×Is(m
, nn-1)-8(,n+1)1, the output signals (115) (114) of the horizontal separation filter (8) are converted into the output signal Y(m,n)(N5) of the adaptive separation filter,
Selectively output as (3(m,n)(116).
s(m-2,n)-8(m+2,n)l >is(
m, nn-1)-s(, n+1)1, the output signals (111) (112) of the vertical separation filter (7) are selected as the output signals of the adaptive separation filter. In other words, the luminance signal color signal separation filter according to the present invention uses four pixel signals in the vertical and horizontal directions whose color subcarriers have the same phase to detect the direction in which the waveform changes less rapidly, and detects the direction in which the waveform changes less rapidly. The luminance signal and color signal are separated using the pixel signal.

Next, the operation of the adaptive separation filter according to the present invention for PAL color television signals will be explained.

When a PAL composite color television input signal series (101) sampled synchronously with the color subcarrier at a sampling frequency of f's-4f', c is input, two sets of variable line delay circuits (5 channels) are input. and dot delay circuit (6) perform delays corresponding to z-(21'-2> and 2, respectively).

(Here, /'=1135) Five sample points are output simultaneously by the delay circuit.

That is, on the screen in FIG. 2, the composite color television 'fW number P(m, 2n) at coordinates (m, n)
At the time when it appears on the signal line of E (1oa), the upper and lower pixel signals P (m, 2n-2) and P (m,
2n-1-2) is output to (11o) and (10j), and pixel signals p(m-2, 2n) and p
(m+2.2n) is output to (109) and (107) simultaneously. P(m, 2n), the pixel signals of the other four composite color television signals have color subcarrier phases different by 18oO, so the separation of the luminance signal and color signal is performed in the same way as in the processing of the NTSC color television signal. It is possible. That is, the final luminance signal Y (m, 2n)
(1163 and color signal C(m, 2n) (117) are extracted using the following processing f/(.

jp(m, 2n-2) -p(rn, 2n+2
) 1<IP(to-2, 2n)-PCno+2.2
n) 1, then M(m, 2n)=7 (P(m, 2n-2)+2P
(m, 2n)+P(m, 2n+2))(!(m,
2n)--7(P(m, 2n-2)-2P(m, 2n)
+P(m, 2n+2)) or jP(m, 2n-2)-P(m, 2n+2) l
) IP(m-2, 2n)-P(m+2.2n)j then Y(m+2n)=7(P(m-2+2n)+2P(m+
2n)”P(m”2,2n))0(m,2n)=-,(
P(m-2, 2n)-2P(m, 2n)+P(m+2,
2n)). In addition, in this method, the composite color television signal P(m, 2n+1) on odd-numbered lines is similarly separated into luminance signals and color signals using upper and lower pixel signals two lines apart and left and right pixel signals two samples apart. can. That is, in the PAL system, the phase of the color subcarrier changes every four lines, so if samples two lines above and below are used, the luminance signal and color signal can be separated in the same circuit.

As described above, the adaptive luminance and chrominance signal separation comb-shaped filter according to the present invention separates the luminance signal and chrominance signal using a signal in which the vertical and horizontal waveforms of a composite color television signal change more gradually. Since I configured the separation filter to do so.

It is effective in following sudden changes in the image and accurately separating the nv times color signal and reproducing a clean received image without cross color or dot interference.

[Brief explanation of drawings]

Figure 1 is an explanatory diagram showing the on-screen arrangement of a signal sequence obtained by synchronously sampling an NTSO composite color television signal at four times the color subcarrier frequency. Explanatory diagram showing the arrangement on the screen of a signal sequence synchronously sampled at four times the subcarrier frequency, Part 3
The figure is a block diagram showing one embodiment of a conventional luminance signal chrominance signal separation filter. FIG. 4 is a block diagram showing an embodiment of an adaptive luminance signal/chrominance signal separation comb filter according to the present invention. In the figure, (1) is the ↑ line delay circuit, c21 is the vertical filter, (3) is the horizontal band pass filter, (4H
-1 subtracter, (5) is a variable line delay circuit; 6) is a dot delay circuit, (7) is a vertical separation filter, and in between is a horizontal separation filter + (9jB comparison decision circuit kLllIl
lff selector. In the drawings, the same or equivalent parts are indicated by the same reference numerals. Agent Masuo Oiwa 1 11 1 1 1 1 1 (>

Claims (1)

[Claims] For a signal sequence obtained by synchronously sampling an NTSO composite color television signal at four times the color subcarrier frequency, a signal on the same line whose color subcarrier phase differs by 180° from the sampled signal Two horizontally adjacent sampling signals adjacent to each other two samples apart on the left and right, and two vertically adjacent sampling signals adjacent to each other one line above and below, the phase of the color subcarrier differing by 180 degrees with respect to the sampling signal. Along with extracting the signals simultaneously. PAL composite color television? For a signal sequence in which the signal is synchronously sampled at four times the color subcarrier frequency. Two horizontally adjacent sampling signals adjacent to each other two samples apart on the left and right on the same line, the phase of the color subcarrier differing by 180 degrees with respect to the sampling signal, and the phase of the color subcarrier with respect to the sampling signal differs by 180 degrees. A variable delay circuit that simultaneously extracts two vertically adjacent sampling signals that are adjacent above and below two lines that are 180 degrees apart. The horizontal difference absolute value between two horizontally adjacent sampling signals, which are the output signals of the variable delay circuit, and the vertical difference absolute value between two vertically adjacent sampling signals are compared, and the absolute difference value in the direction of the smaller absolute difference value is compared. A comparison/determination circuit for selecting output signals of the vertical and horizontal separation filters described below, which constitutes a 92nd-order digital filter by adding and subtracting the sampled signal of the composite color television signal series and two horizontally adjacent sampled signals. A horizontal separation filter separates and outputs a luminance signal and a color signal, and a second-order digital filter is configured by adding and subtracting the sampled signal of the composite color television signal series and two vertically adjacent sampled signals. Vertical separation filter that separates and outputs the luminance signal and color signal,
a selector, etc., for selecting the output signal of the vertical or horizontal separation filter in the direction in which the adjacent sampling signal changes less than the comparison and determining circuit 1, and using it as the final luminance signal/chrominance signal separation power signal; [Characterized by ] related type luminance signal chrominance signal *@ type filter.