JPS6118285A - Luminance signal and chrominance signal separating filter - Google Patents

Abstract

PURPOSE:To prevent reduction in the filter effect due to sudden change in a picture signal between adjacent picture elements by constituting a separation filter to each prescribed four-direction and using properly four kinds of the separating filters with selection. CONSTITUTION:When a signal S(m, n) appears on a signal line 114, signals S(m+2, n+1), S(m-2, n+1), S(m+2, n-1), S(m-2, n-1) appear on signal lines 101, 112, 116 and 118 respectively. A four-direction separating filter 7 inputs the signals S(m, n), S(m+2, n), S(m-2, n), S(m, n-1), S (m, n+1) so as to attain a prescribed operation. Four values of calculated C1N(m, n), C2N(m, n), C3N(m, n), C4N(m, n) are inputted to a selector 8 through signal lines 120-123, and a signal selected by a control signal from a comparison decision circuit 4 is outputted on the signal line 124.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a color television receiver, and more particularly to a digital filter that separates a luminance signal and a chrominance signal from a digitized color television signal.

[Prior art]

The NTSC composite color television signal S is a composite signal of a luminance signal Y and a chrominance signal C. The chrominance signal C consists of two color difference signals U and V at a right angle of 2 at a color subcarrier frequency fsc.
It is well known that it is phase modulated. That is, S=Y+C=Y+Usin (2ifsct)+Vc
os (2πfsc t Roux+11 If the frame frequency is fr (=30Hz) and the field frequency tfvs horizontal scanning frequency is fH, then fsc = T-fH = -T
It is also well known that fsc is determined by the relationship -T-fv=-T-525f, -121, and fsc=3.583 MHz. Furthermore, when digitizing the signal S shown in equation (1), the sampling frequency fs
It is also well known to set fs = 4 fsc.

fs = 4 When the signal S is sampled at fsc, the signal S at the sampling point corresponding to the online m column on the screen, the signal at each sampling point near (m, n) is shown in Figure 1. It becomes as shown in .

In Figure 1, the black triangle (e.g. S (m, n))
is Y10 c, where C= (U0V)), a hollow triangle (for example, S(m, n-1)) is Y-C, and a black square (for example, S(m+1.n)) is Y 10C' [However, S
(m+1.n-1)) represents Y-C'. Also f
From the relationship sc=i5iifH, black and hollow are alternately arranged in each row in the vertical column.

Next, PAL composite color television signal PP=
Y + Usin (2πfsc pt) :t V
cos(2yrfscpt)-+31, where Y
, U, and V are Y in formula (1), respectively.

Similar to U and V, fscp is the color subcarrier frequency in the PAL direction, and the frame frequency of the PAL system is tftp.
(= 25 Hl), where the field frequency is fvp and the horizontal scanning frequency is fHl, fscp = (2S4-'A +625) f, p
=(2S4-V4+-0r)・Dingfvp=(2S4-V
4"-rrr 625 fFp...(4). In equation (3), the sign change is - for even scan lines and 10 for odd scan lines. In other words, the V component is inverted for each scan line. do.

With a sampling frequency of fsp = 4 fscp, the formula (
When the signal shown in 3; is digitized, the signal P(m, n) at the sampling point corresponding to the online m column on the screen is obtained.
The signals at each sampling point in the vicinity of are as shown in FIG. In other words, on the line where ± of equation (31) becomes 0, it becomes the same as equation (11), so the arrangement in Figure 2 is the same as in Fig. 1, and on the line where + becomes -, the black rectangle and the hollow are inserted. change.

A conventional digital filter compatible with the NTSC system is constructed using the characteristics of the signal array shown in FIG. 1, and FIG. 3 is a block diagram showing an example of the conventional device. In the figure, (1) is a vertical filter, (2) is a bandpass filter, (3) is a subtracter, and the vertical filter (1) is a vertical filter calculation circuit ασ and a 1-line delay circuit ttn.
and 112. (101) to (106) indicate each signal line.

Assume that a signal S expressed by the formula fi+ is inputted onto the signal line (101) as a digitized signal S18+ as shown in FIG. However, +81 S is the number of the sampling point. At the time when the signal S (m, n+1) in FIG.
(m, n), and the signal on the signal line (103) which is the output of the one-line delay circuit u21 is S(m, n-1).

The arithmetic circuit 1101 calculates He (mr ”) =-Kaede (S(mT ”-1
) −2S (mT n ) ”b (m r n
+1 ) )...t! Perform the calculation of 51 and calculate % Hc(
m, n). By the way, S(m, n-1)+
s(mTn)+SCm, n+1) t/'i
Since these are signals of lines that touch each other in the vertical direction, the values of Y, U, and V in equation (1) should generally be very similar.

Y, C straightness S (m, n-1), 5cm1n>l
For S(m, n+1), respectively (Yo+ΔYl +
Co+ΔCt)+(YO+cO)+(Yo+Δ
Y2yQl+△C2) then △Y1. ΔY2 +ΔC
1+ΔC2 is generally an extremely small value. Therefore, the calculation result of equation (5) is Hc (m, n) = -'
A (C△Y1 +ΔY2)-4Co 10 (
-ΔC1-6Ct))”Co”A(ΔC,+8C2
)4(ΔY, +ΔY2)...(61).

The signal on the signal line (101) is 3(m, n+1) in Figure 1.
Next is S (m+1. n+1), but
At this point, the arithmetic circuit (1α output HC(m+1,
HC(m+1, n)=C'ten'/4(ΔC'
+ ΔC”)l 2 ・V4(ΔY3 +ΔY4)...(7),
ΔC1, ΔC2, ΔCf, Δq, ΔY3° and ΔY4 are generally extremely small values.

That is, the signal S input to the vertical filter il+
(S) includes a luminance signal Y (81 (digitized signal Y in equation (1)) and a color signal C (sl (digitized signal C in equation (1)). , it can be seen from equations (16) and (7) that the luminance signal Y(8) at the output of the arithmetic circuit 111 is sufficiently attenuated.

Letting z and z using a delay of one sampling period and a delay of one line using 1-2 conversion, respectively, Z'' = e
xp (-j2πf/fs) −= +81,
From equation 12), t = 910.

If the signal on the signal line (101) is S (81), the signals on the signal lines (102) and (103) are delayed by one line (5(s)) and S ((s) by two lines), respectively.
81, vertical filter +11 transfer function Hv (
z) is HV(Z) = -V4(1-2z-' + z
−2勺= −'A (1−Z−')” −−・−1
It becomes 101.

The signal Y remaining in the output of the vertical filter (1)
(In order to further attenuate 81, a bandpass filter (
2) is used. The bandpass filter (2) has a center frequency f
This is a band-pass digital filter designed to pass the band of the sCs signals U and V.

For example, the transfer function HB(Z) of the bandpass filter (2) is trn(z)=-(1-z-2)2(1+z
-')2(1+z-8)-...old).

The output of the bandpass filter (2) is assumed to be the color signal C (81), subtractor ta+vc oi-r
5r8)-as) = Y(s>) can be obtained.

A conventional digital filter compatible with the PAL system is constructed using the characteristics of the signal arrangement shown in FIG. In other words, in the case of the NTSC system, the equation (
51, in the PAL system, using two lines above and below, Hcp (m, 2n) = -W (S (m, 2n - 2) -, 2
S (m, 2n) + S (m, 2n + 2)) - (12), and outputs the calculation result onto the signal line (104).

The conventional device is configured as described above, and in the vertical filter (1), Δ′f′l, ΔY of equations 16+, +71
2 +Δya 1ΔY4 +ΔC1+ΔC2, ΔC7,
Since the filter is constructed assuming the characteristic that the value of ΔC (etc.) is sufficiently small, it is difficult to The vertical filter does not function as a filter, and as a result, there is a drawback that the reproduced image becomes blurred, such as color dot interference due to cross color.

[Summary of the invention]

This invention was made to eliminate the above-mentioned drawbacks of the conventional ones. In general, image signals for pixels that are adjacent to each other in the direction of a line that is inclined to the horizontal direction (hereinafter referred to as a diagonal line) are also similar to each other. In general, focusing on the fact that they are similar to each other, a separation filter is constructed for each of four predetermined directions, and by appropriately switching and using these four types of separation filters, the image signal changes suddenly between adjacent pixels. In particular, the reduction in filter effectiveness caused by this was prevented.

[Embodiments of the invention]

Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 4 is a block diagram showing one embodiment of the present invention.
Corresponding to the input signals shown in the figure, the same symbols as in Figure 3 are the same.
or a corresponding portion (41 is a comparison/judgment circuit, (5a)
, (5b), (5c), (5d), (5e), (5f)
are delay circuits each having two sampling periods (6a).

(6b) is a delay circuit of (1 line - 4 sampling periods), (71 is a 4-way separation filter, (81 is a selector), and (111) to (125) are signal lines, respectively. In the case shown in the figure, the band filter (2) is omitted, but the selector (9)
A bandpass filter (2
) may be inserted.

When the signal S (m, n) shown in FIG. 1 appears on the signal line (114), the signal lines (101), (112), (11
6).

(118) have S(m+2.n+1) and S
(m-2, n+1)+S(m+2.n-1), S(
Signals denoted by m-2, n-1) appear, and these signals have the same color subcarrier phase as the signal S(, m, n),
Also, signal lines (111) and (113).

(115) and (117) each have S(m, n+1)
, S(m+2゜n)+s(m-2,nLs(m,n
−1) appear, and these signals become the signal s (“ r ”
), the phase of the color subcarrier differs by 180°.

4-way separation filter (71 is the signal S (m, n) and the signal S
(m+2.n), S(m-2, n), S(m, n-1)
y signal S(m, n+1) manually and CW(m, n)"-'/i(S(m-2rn)-2S
(m, n) 10S(m,n-1)1...(13 CN(m,n)=-1/4{S(m+2,n)-2S(
m, n)+S(m, n-1))...α→ CN(m, n)=-'4(S(m-2, n)-2S(m
, n)+S(m, n+1)) -・-UcN(ml'n
)==-*(S(m+2,n)-2S(m,n)
+S(m, n+1))-9Q is calculated.

< (m, n) calculated by formula a31-o*
I C”2 (m, n).

The four values C'H (m, n) and C': (mln) are input to the selector (9) through signal lines (120) to (123), respectively, and the control signal (signal 11i1 (119)) is output on the signal line (124).

The comparison/judgment circuit (4) has signals S(m+2.n+1),
S(m-2゜”1)+ S(mln)l S(m+
2. n-1) + S(m'-2, n-1) is input, '1 (m, n) = l S(m, n)-8(m-2
, n-1) l ・-Lη'2(mln) = l
S(”+1)=S(m+2.n-1) I
・-tt81εN(m, n) = l S(m, n)-
8 (m-2, n+1) I-・Sub■C4 (mln)
” l S(m,n)-8(m+2.n+
1) The operation X of l −1all is performed and ε , ε ,
Among ε and e, the one with the minimum value is determined, and the minimum values are C1 and C2.

Corresponding to the case where the bow and εr are CIN, respectively.

c: , c, N, cN are output from the selector 191.

In the case of the embodiment shown in FIG. 4, the signal output from the selector (9) corresponds to C(s) in FIG.
Attending S (81-Ctsl : Y-(sl) by the button is the same as in the case of FIG. 3.

FIG. 5 is a block diagram showing an embodiment of the present invention for the PAL system composite color television signal shown in FIG. do. (6c).

(6d) is a delay circuit that provides a delay amount of (2 lines - 4 sampling periods).

Therefore, the signal P(m) shown in FIG.
, 2n) appears, the signal line (101),
(111).

(112), (113), (114), (15), (1
16), (117), and (118), P(m
+2.2n+2L P(m, 2n+2), p(m+
2゜2n), P(m-2, 2n) + P(m+2
．． n), P(m-2, '2n), P(m+2゜2n-2
), P(m, 2n-2), P(m-2, 2n-2
) signal is output.

For 4-way separation filter +71, CP (m, 2n) = -% {P (m-2, 2n) - 2P
(m, 2n)+P(m, 2n-2)) -el) c, (m, 2n)=='+L{P(m+2.2n)-
2P (m, 2n) + p (m, 2n-2))... (goods) C3 (m + 2n) = -1 {P (m-2, 2n) - 2P
(m, 2n)+P(m, 2n+2)) ・・・娑jCP(m, 2n)=-W{P(m+2.2n)
-2P(m, 2n)+P(m, 2n+2)) ・
・・・(to) is calculated and the calculation result is C□(m, 2n)
, C2(m, 2n).

c: (m, 2n), 'C: (m', 2n) are input to the selector 181.

Comparison/judgment circuit (in 41, εIP(m, 2n) = I P(m, 2n) −
P(m-2, 2n-2] -eAε2P (rrz
2n) = J p(m, 2n) −P(m+
2. 2n-2] −QBF3P(”b 2n) =
l P(m, 2n) -PCm-2, 2n+2]
−@, p (m, 2n) = l P(m
, 2n)-P(m+2. 2n+2)l-12S1
The operation of the selector (9) and the operation of the circuit after the selector (9) are the same as those shown in Fig. 4. .

Furthermore, the delay circuits (6a) and (6b) in FIG. 4 may be used as variable delay circuits for both the NTSC system and the PAL system.

〔Effect of the invention〕

As described above, according to the present invention, the color subcarrier frequency is
When separating a luminance signal and a color signal from a composite color television signal digitized by double the sampling frequency, automatic switching is performed to use the filter in the direction that causes the smallest change in the image signal on the cathode ray tube. Therefore, it is possible to provide a luminance signal separation filter that is effective for any image signal.

[Brief explanation of drawings]

Figure 1 shows the data array on a cathode ray tube when an NTSC composite color television signal is digitized at a sampling frequency four times the color subcarrier frequency. A diagram showing the data array on a cathode ray tube when digitized at a sampling frequency four times the subcarrier frequency, FIG. 3 is a block diagram showing the configuration of a conventional filter, and FIGS. FIG. 2 is a block diagram showing one embodiment. +31-...Subtractor, 141-...Comparison judgment circuit, (5
a), (5b). (5c) , (5c+) , (5e) , (5f) ,
(6a), (6b), (6c), (6d
) --Respectively delay circuit, (7) . . . four-way separation filter, (81 . . selector). In addition, the same reference numerals in the drawings indicate the same or phase west portions.

Claims (2)

[Claims] (1) For each data signal obtained by digitizing an NTSC composite color television signal at a sampling frequency that is four times the color subcarrier frequency, digitize the data signal in the mth column and the Let the signal S(m, n) be arranged in n rows, and the data signal arranged in the same row as the signal S(m, n) and in the column 2 bits before is the signal S.
(m-2, n), and the data signal arranged in the same row as the signal S(m, n) and the column two bits later is the signal S(m+2,
n), and the data signal arranged in the same column and one row before the signal S(m, n) is the signal S(m, n-1), and the signal S(
The data signal arranged one row after in the same column as S
(m, n+1), and the data signal arranged in the column one row and two bits before the signal S(m, n) is the signal S(m, n+1).
-2, n-1), and the data signal arranged in the column one row before and two bits after the signal S(m, n) is the signal S(m, n-1).
+2, n-1), and the data signal arranged in the column one row after and two bits before the signal S(m, n) is called the signal S(m, n).
−2, n+1), and the data signal arranged in the column one row and two bits after the signal S(m, n) is the signal S(m, n+1).
+2, n+1), then C^N_1(m, n)=-
1/4 {S(m-2,n)-2S(m,n)+S(m,
n-1)} and outputs a signal C^N_1(m, n), C^N_2(m, n)=-1/4{S(m+2, n)-
2S(m, n)+S(m, n-1)} and outputs a signal C_2^N(m, n), C^N_3(m, n)=-1/ 4{S(m-2, n)-
2S(m, n)+S(m, n+1)} and outputs the signal C^N_3(m, n), C^N_4(m, n)=-1/4{ S(m+2,n)-
2S(m,n)+S(m,n+1)} and outputs the signal C^N_4(m,n); -2, n-1)
, signal S(m+2, n-1), signal S(m-2, n+1
), the signal S (m+2, n+1) is determined to determine which of the four signals is most similar to the first and second signals.
, a luminance signal and a chrominance signal separation filter, comprising means for selecting an output of one of the third and fourth direction separation filters. (2) For each data signal obtained by digitizing a PAL composite color television signal at a sampling frequency that is four times the color subcarrier frequency, the data signal is digitized in the mth column, the mth column, and the Let the signal P(m, 2n) be arranged in 2n rows, let the data signal be arranged in the same row as the signal P(m, 2n) and in the column 2 bits before the signal P(m-2, 2n), The data signal arranged in the column two bits after the signal P(m, 2n) in the same row as the signal P(m, 2n) is
m+2, 2n), and 2 in the same column as the signal P(m, 2n).
The data signal arranged before the row is the signal P(m, 2n-2)
Let P(m, 2n+2) be the data signal arranged in the same column and two rows after the signal P(m, 2n), and the signal P(m,
The data signal arranged in the column two rows and two bits before the signal P(m-2, 2n-2) is the signal P(m-2, 2n-2).
The data signal arranged in the column two rows before and two bits after the signal P(m, 2n) is defined as a signal P(m+2, 2n-2), and the data signal arranged in the column two rows and two bits before the signal P(m, 2n) Let the data signal arranged in columns be a signal P(m-2, 2n+2),
When the data signal arranged in the column two rows and two bits after the signal P (m, 2n) is the signal P (m+2, 2n+2), C^P_1 (m, 2n) = -1/4 { P(m-2, 2n
)-2P(m, 2n)+P(m, 2n-2)} and outputs a signal C_1^P(m, 2n), C^P_2(m, 2n)=- 1/4 {P(m+2, 2n
)-2P(m, 2n)+P(m, 2n-2)} and outputs a signal C_2^P(m, 2n), C^P_3(m, 2n)=- 1/4 {P(m-2, 2n
)-2P(m, 2n)+P(m, 2n+2)} and outputs a signal C_3^P(m, 2n), C^P_4(m, 2n)=-1/ 4{P(m+2, 2n
)-2P(m, 2n)+P(m, 2n+2) and outputs the signal C_4^P(m, 2n). m-2, 2n-
2), signal P(m+2, 2n-2), signal P(m-2,
2n+2) and signal P(m+2, 2n+2), one of the first, second, third, and fourth direction separation filters is determined by determining which of the four signals P(m+2, 2n+2) is most similar.
A luminance signal chrominance signal separation filter comprising means for selecting the output of two direction separation filters.