JPS60237784A - Pal system luminance signal chrominance signal separating filter - Google Patents

Abstract

PURPOSE:To reproduce a reception picture without cross color and cross luminance by using a signal in a direction where vertical and horizontal waveforms are changed more slowly to separate a luminance signal and a chrominance signal. CONSTITUTION:A generating circuit 3 is oscillated synchronously in a frequency four times the chrominance subcarrier frequency of a composite TV signal applied to an input terminal 1 and the phase of the sampling pulse is a phase led or lagged by 45 deg. to the axis of R-Y and B-Y color difference signals. The sampling pulse is fed to an A/D converter 2, where an analog composite TV signal is converted into a digital signal and the sampling signal series is given to a luminance signal output circuit 91 via a vertical/horizontal filter 70 and a detection circuit 80. In this case, the YC separation is attained by using values of the sampling point before and after two samples of a line upper or lower by one line to the noted sampling point or the sampling point of the said line. Further, the direction where the signal changes more slowly is detected by using the sampling point value in existence adjacently and the Y signal is extracted by using an output of the filter in the said direction.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention provides a system for converting a luminance signal (hereinafter referred to as Y signal) and a color signal (hereinafter referred to as C signal) from a PAL system composite television signal (composite video signal). This is a luminance signal/chrominance signal separation filter (hereinafter referred to as YC separation filter) that separates and extracts the signal. After converting a PAL system analog composite television signal into a digital signal, it digitally separates the Y signal and C signal. Concerning those who carry out

[Prior art]

In the current color television standard system, the Y signal and C signal are transmitted as a frequency-multiplexed composite signal.
The receiver needs to correctly separate the Y signal and C signal from the received composite signal.

The PAL composite television signal P includes a luminance signal Y,
It is a composite signal of two color difference signals U and (or I and Q) and a color signal C which is quadrature two-phase modulated at a color subcarrier frequency fsc, and can be expressed as shown in the following equation.

P=Y+C -Y+Usin (2nfsc t) ±Vcos (2nfsc t) Here, the sign "±" added to the third term in the above equation is "+" for the odd scanning line and "+" for the even scanning line in the signal P. −”
It is. That is, the V component is inverted for each scanning line. Set the frame frequency to fF (25Hz).

If the field frequency is fV (50H2) and the horizontal scanning frequency is fH (15,625KHz), then fsc = (2841/4 + 1/825) f between these and the above fsc.
H= (284-1/4 + 1/625) 625
-fV/2= (284-1/4 + 1/625)
A relationship of 625 fp is established. That is, the above fsc
and fH above! - is in the relationship of 1/4 line offset. Therefore, a sampled signal sequence obtained by synchronously sampling a PAL system composite television signal at a sampling frequency fS that is four times the color subcarrier frequency becomes a two-dimensional array on the screen as shown in FIG. That is, the same phase of the color signal is repeated every four lines. In the figure, the symbols indicated by circles, triangles, etc. indicate the sample points P, Y is the luminance signal, CI, C2, C1°, and C2' are the color signals, respectively, and U
l, U2. Vl.

v2 indicates a color difference signal.

In addition, in order to ensure compatibility with black and white television signals,
It is necessary for the receiver to accurately separate the ``Y-fold signal C signal'' from a composite color television signal containing a C signal frequency-multiplexed so that the spectrum increments in frequency within the band of the Y signal. .

An example of the configuration of a conventional YC separation filter is shown in FIG. In FIG. 2, 1 is an input terminal for a PAL analog composite television signal, 2 is an A/D converter, 3 is a sampling pulse generation circuit (S P), and 41 and 42 are the A/D converters 2, respectively. These are first and second delay circuits (two-line memories) that delay the sampling signal output from the two horizontal scanning periods by two horizontal scanning periods.

5 is the 1/2 times circuit, 61.62 is the 1st. The second 1/4 multiplication circuit 7 is a subtraction circuit, and this subtraction circuit 7 is
It is configured to subtract the outputs of the first and second 1/4 times circuits 61 and 62 from the output of the /2 times circuit 5.

8 is a horizontal band pass filter, and 9 is a second subtraction circuit, which is configured to subtract the output of the horizontal band pass filter 8 from the output of the first delay circuit 41.

10 is the output end of the horizontal band pass filter 8, and 11 is the output end of the subtraction circuit 9.

Next, the operation of the circuit shown in FIG. 2 will be explained.

The sampling pulse generation circuit 3 is an oscillation circuit that synchronously oscillates at a frequency fs that is four times the color subcarrier frequency fsc of the composite television signal applied to the input terminal 1, and its output is A/
It is applied to the D converter 2. The A/D converter 2 converts the analog signal applied to the input terminal 1 into a digital signal based on the signal from the sampling pulse generation circuit 3. A sampled signal sequence of a PAL composite color television signal sampled at a sampling frequency fs=4fsc has an arrangement as shown in FIG. 1, if attention is paid to the phase of the C signal on the screen. In other words, the phase of the C signal returns every 4 lines, and a line 2 lines above or below a certain line l (
j2-2) and (#+2), the phase of the color subcarrier of the color signal component changes by 180 degrees, that is, is reversed. The 1/2 multiplication circuit 5 is a circuit that multiplies the output of the first delay circuit 41 by 1/2,
The output of this 1/2 multiplier circuit 5 is applied to a subtraction circuit 7.

Further, the first 1/4 multiplier circuit 61 multiplies the output of the A/D converter 2 by 1/4, and the output of this 1/4 multiplier circuit 61 is applied to the subtraction circuit 7. Also, the second 1/4 times circuit 6
2 multiplies the output of the second delay circuit 42 by 1/4, and the output of this 174 times circuit 62 is applied to the subtraction circuit 7. The subtracting circuit 7 converts the output of the 1/2 times circuit 5 into the output of the first 174 times circuit 61 and the second 1/2 times the output.
The output of the quadruple circuit 62 is subtracted. Therefore, the output Hc (It, m) of this subtraction circuit 7 is He (j!, m) = 1/4 (-P (# -2
, m) + 2P (1++o) P (It +21m
) ) becomes. Here, P(j!, m) indicates the sample value of the m-th sample point on the first line. The output signal Hc (β, m) of the subtraction circuit 7 is applied to a horizontal band pass filter 8. The horizontal band-pass filter 8 is a band-pass filter configured to pass the color signal component, and is the output signal Hc (j!) of the subtraction circuit 7.
, m) remove the Y signal component contained in This filter is, for example, Rh(Z) = -1/32- (1-Z
-2) 2(1+Z-4)2 (1+Z-8) That is, the C signal is obtained as the output of the horizontal band pass filter 8.

The subtraction circuit 9 is configured to subtract the output of the horizontal bandpass filter 8 from the output of the first delay circuit 41, and therefore the subtraction circuit 9 subtracts the color signal from the composite television signal. Therefore, a Y signal is obtained at the output of the subtraction circuit 9. Output end 10,1
．． 1 are the horizontal band pass filters 8, 1 and 1, respectively. It is obvious that the output terminal 1o is connected to the subtraction circuit 9, so that the C signal is obtained at the output terminal 1o, and the Y signal is obtained at the output terminal 11.

In this way, conventional YC separation filters are constructed by fixing vertical and horizontal filters and combining them, and the pixels that are the sampling series of the television signal are adjacent to each other on the main 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 Y signal and C signal leak into each other's channels, causing interference such as cross color and cross luminance, which significantly reduces the quality of the reproduced image. The problem was that it was difficult to get used to.

[Purpose of the invention]

The present invention was made to eliminate these difficulties, and it is possible to input a composite television signal at a frequency four times as high as the color subcarrier frequency and whose phase is 45 degrees ahead or behind the color difference signal. An inverted sampling point sampled with phased sampling pulses and whose color subcarrier phase is inverted from that of the sampling point of interest is placed in the neighborhood of the line of the sampling point of interest and lines above and below that line. Using the values of the sample point of interest and the inverted sample point, the color signal of the sample point of interest is separated by a vertical filter and a horizontal filter, respectively, and the color signal of the sample point of interest is separated by the inverted sample point. Accurate separation of the Y signal and C signal can be achieved by detecting the attributes of the filter and switching the vertical filter and horizontal filter as appropriate, and yet does not require a 2-line memory as in the conventional method. Not 1
It is an object of the present invention to provide a PAL type YC separation filter that can perform processing using a line memory.

[Embodiments of the invention]

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 3 is a diagram showing an embodiment of the present invention. In the figure, 1 is a long end of a composite television signal (composite video signal) which is an analog signal, 2 is an A/D converter, and 3 is a sampling The pulse generation circuit (SP) 43 is a first delay circuit (SP) that delays the output of the A/D converter 2 by one horizontal scanning period.
1 line memory), 44 is a second delay circuit whose delay time is two sampling periods shorter than the delay time of the first delay circuit 43, and 51, 52, and 53 are the first delay circuits, respectively. Second. 3rd 1
/2x circuit, 63.64 is the 1st. second 1/4 circuit,
91, 92, 93, 94.95 are the 1st. Second.
Third. 4th. Fifth subtraction circuit, 21a, 21b, 21c
, 21d, 21e, and 21f each delay the sampled signal by two sampling periods. 4th. Fifth. 6th. 7th. 8th
This is a delay circuit. 22a, 22b, 22c, and 22d are the first degree, the second degree, and the second degree. Third. 4th adder circuit, 23a, 23b are absolute value circuits of the 11th field 2, 24a, 24b, 24C are the 1st . Second. In the third switch circuit, 25 is a comparison circuit, 26 is a switching pulse generation circuit, and 10.11 is an output terminal of the above-mentioned switch circuit 24C1 and the above-mentioned subtraction circuit 91, respectively.

And the above-mentioned first to eighth delay circuits 43, 44゜21a~
21f, the first to fourth adding circuits 22a to 22d1, the first to fourth adding circuits 22a to 22d1;
second 1/4 multiplier circuits 63, 64, third . Fifth subtraction circuits 93, 95, first . Second switch circuits 24a, 24b
, the first to third 1/2 multiplier circuits 51 to 53, and the switching pulse generation circuit 26 constitute a vertical filter and a horizontal filter 70. Also, the above 2. The fourth subtraction circuit 92.94, the first subtraction circuit 92.94. second absolute value circuit 23a,
23b and the comparison circuit 25 constitute a detection circuit 80 that detects the direction in which the composite television signal changes less.

Next, the operation of the circuit shown in FIG. 3 will be explained.

The sampling pulse generation circuit 3 is an oscillation circuit that synchronously oscillates at a frequency fs that is four times the color subcarrier frequency fsC of the composite television signal applied to the input terminal 1, and the phase of the sampling pulse is determined by the color difference signal (R -Y).

The phase is configured to be advanced or delayed by 45 degrees with respect to the (BY) axis. The sampling pulse, which is the output of the sampling pulse generation circuit 3, is transmitted to the A/D converter 2.
The A/D converter 2 converts the analog composite signal applied to the input terminal 1 into a digital signal. The sampling signal sequence of the PAL composite color television signal sampled using the sampling pulses is arranged as shown in FIG. 4, if attention is paid to the phase of the C signal on the screen.

FIGS. 5 and 6 are diagrams for explaining in detail one embodiment of the present invention, in which symbols are attached to the sampling series shown in FIG. 4 above. The case of FIG. 5 will be explained using the circuit diagram of FIG. 3.

Assuming that the A/D converter 2 outputs a sample value of a sample point P9 at a certain time T, the third delay circuit 21a outputs P8, the fourth delay circuit 21b outputs P1,
P6 from the first delay circuit 43, and the seventh delay circuit 21e.
The sample value of the sample point is P5 from , P4 from the eighth delay circuit 21f, P3 from the second delay circuit 44, P2 from the fifth delay circuit 21C, and Pl from the sixth delay circuit 21d. Each is output. In this case, the sample point to be separated by YC (the sample point of interest) is P5.

In the case of FIG. 5, the switching pulse generation circuit 26 is connected to the first 1/2 times circuit 51 for the first switch circuit 24a.
A control signal is sent to the second switch circuit 24b to pass the output signal of the fifth delay circuit 2IC, and a control signal is sent to the second switch circuit 24b to pass the output signal of the fifth delay circuit 2IC.

The first adder circuit 22a adds the output signal of the A/D converter 2 and the output of the fourth delay circuit 21b, and the first 1/2 times circuit 51 adds the output signal of the A/D converter 2 and the output of the fourth delay circuit 21b. Since the output of the first adder circuit 22a, that is, the output signal of the first switch circuit 24a, is 1/2 ((sampled value of sample point P9) + (sampled value of Pl) The sample value of the sample point)) becomes. Further, the output signal of the second switch circuit 24b is
This is the sample value of the sample point P2.

The third adder circuit 22c is connected to the first switch circuit 24a.
and the output of the second switch circuit 24b, and the first 1/4 multiplier circuit 63 multiplies the output of the adder circuit 22c by 1/4. Further, the third 172x circuit 53 multiplies the output of the seventh delay circuit 21e by 1/2. . Then, the third subtraction circuit 93 subtracts the output signal of the first 1/4 times circuit 63 from the output signal of the third 1/2 times circuit 53, and therefore the output signal of this subtraction circuit 93 is - 1/4
(1/2 (sample value of sampling point P9) + (sample value of sampling point Pl))] +1/2 (sample value of sampling point P5) - 1/4 (sample value of sampling point P5)
The sample value of the sample point is 2).

Further, the fourth adder circuit 22d adds the output of the first delay circuit 43, the eighth delay circuit 21f, and the output signal, and the second 1/4 multiplier circuit 64 adds the output of the adder circuit 22d. Multiply by 1/4. The fifth subtraction circuit 95 is connected to the third subtraction circuit 95.
The output signal of the second 1/4 multiplier circuit 64 is subtracted from the output signal of the 1/2 multiplier circuit 53, and therefore this subtraction circuit 95
The output signal of is 1/4 (sample value of sample point P4) + 1/2 (P
The sample value of the sample point P5)'-1/4 (the sample value of the sample point P6).

Furthermore, the first switch circuit 24a and the second switch circuit 2
4b is applied to a second subtraction circuit 92, and the absolute value of the output of this subtraction circuit 92 is taken by the first absolute value circuit 23a. Therefore, the output signal TV of the first absolute value circuit 23a
is TV=11/2 ((sample value of sample point P9) + (P
The sample value of the sample point l)) - (the sample value of the sample point P2).

Also, the first delay circuit 43. The output of the eighth delay circuit 21f is applied to a fourth subtraction circuit 94, and the absolute value of the output of this subtraction circuit 94 is taken by the second absolute value circuit 23b. Therefore, the output signal TO of the second absolute value circuit 23b is as follows: TH=l(sample value at sample point P4)=(sample value at sample point P6).

The output signal Tv of the first absolute value circuit 23a and the second
The output signal TH of the absolute value circuit 23b is applied to the comparison circuit 25, which compares the magnitude of Tv and TH, and sends a control signal to the third switch circuit 24C.

The output signal of the third subtraction circuit 93 and the output signal of the fifth subtraction circuit 95 are applied to the third switch circuit 24C, and the comparator circuit 25 determines that the TV and TO are 'l' v < TH. When , the third switch circuit 24
T so that the output of c becomes the output of the third subtraction circuit 93.
When v≧TI, a control signal is applied to the third switch circuit 24c so that the output of the third switch circuit 24c becomes the output of the fifth subtraction circuit 95.

In other words, in the method according to this embodiment, the direction in which the signal changes less is detected using neighboring pixel signals (values of inverted sample points) in which the phase of the color subcarrier is inverted, and the pixel in the direction in which the signal changes less is detected. Since the signal is used to separate the C signal from the composite television signal, accurate separation is possible.

Next, the case of FIG. 6 will be explained using FIG. 3.

Assuming that the A/D converter 2 outputs a sample value of a sample point P9 at a certain time T, the third delay circuit 21a outputs P8, the fourth delay circuit 21b outputs P1,
From the first delay circuit 43, P6 and the seventh delay circuit zte
The sample value of the sample point is P5 from , P4 from the eighth delay circuit 21f, P3 from the second delay circuit 44, P2 from the fifth delay circuit 21C, and PI from the sixth delay circuit 21d. Each is output.

In the case of FIG. 6, the switching pulse generation circuit 26 is connected to the third delay circuit 21 for the first switch circuit 24a.
A control signal is sent to the second switch circuit 24b so as to allow the output signal of the second 1/2 circuit 52 to pass therethrough.

The second adder circuit 22b adds the output signal of the second delay circuit 44 and the output of the sixth delay circuit 21d, and the second 1/2 times circuit 52 adds the output signal of the second delay circuit 44 and the output of the sixth delay circuit 21d. Since the output is multiplied by 1/2, the output of the second addition circuit 22b, that is, the output signal of the second switch circuit 24b is 1/2 ((sampled value of the sampling point P3) + (sampled point Pl) sample value)). Further, the output signal of the first switch circuit 24a is P
This is the sample value of the sample point 8.

The third adder circuit 22C is connected to the first switch circuit 24a.
and the output of the second switch circuit 24b, and the first 1/4 multiplier circuit 63 multiplies the output of the adder circuit 22C by 1/4. Further, the third 1/2 multiplying circuit 53 multiplies the output of the seventh delay circuit 21e by 1/2. Then, the third subtraction circuit 93 subtracts the output signal of the first 1/4 times circuit 63 from the output signal of the third 172 times circuit 53, so that the output signal of this subtraction circuit 93 is 1/4 (
1/2 ((Sample value of the sampling point P3) + (Sample value of the sampling point Pl))] + 1/2 (Sample value of the sampling point P5) - 1/4 (P
The sample value of the sample point is 8).

Further, the fourth adder circuit 22d adds the output signal of the first delay circuit 43 and the output signal of the eighth delay circuit 21f, and the second 1/4 multiplier circuit 64 adds the output signal of the first delay circuit 43 and the output signal of the eighth delay circuit 21f. Multiply by 1/4. The fifth subtraction circuit 95 is connected to the third subtraction circuit 95.
The output signal of the second 1/4 multiplier circuit 64 is subtracted from the output signal of the 1/2 multiplier circuit 53. Therefore, this subtraction circuit 9
The output signal of 5 is: -1/4 (sample value of sample point P4) +1/2 (sample value of sample point P5) -1/4 (sample value of sample point P5)
The sample value of the sample point is 6).

Furthermore, the first switch circuit 24a and the second switch circuit 2
4b is applied to a second subtraction circuit 92, and the absolute value of the output of this subtraction circuit 92 is taken by the first absolute value circuit 23a. Therefore, the output signal Tv of the first absolute value circuit 23a
is Tv= l 1/2 ((sample value of sample point pa) +
(Sample value of sample point Pl) - (Sample value of sample point P8) 1.

Also, the first delay circuit 43. The output of the eighth delay circuit 21f is applied to a fourth subtraction circuit 94, and the absolute value of the output of this subtraction circuit 94 is taken by the second absolute value circuit 23b. Therefore, the output signal TH of the second absolute value circuit 23b is as follows: TH=l(sample value at the sample point P4)-(sample value at the sample point P6)1.

The output signal Tv of the first absolute value circuit 23a and the second
The output signal TH of the absolute value circuit 23b is applied to a comparator circuit 25, which compares the magnitude of TH with the above TV, and sends a control signal to the third switching circuit 24C. The third sui-nochi circuit 24C has a third subtraction circuit 9.
3 and the output signal of the fifth subtraction circuit 95 are applied, and the comparator circuit 25 receives the Tv, 'I')I
TV≧TH so that when Tv<TH, the output of the third switch circuit 24C becomes the output of the third subtraction circuit 93.
In this case, the third switch circuit 24C is switched so that the output of the third switch circuit 24C becomes the output of the fifth subtraction circuit 95.
Apply a control signal to.

That is, in the method according to this embodiment, the direction in which the signal changes less is detected using neighboring pixel signals whose color subcarriers have inverted phases, and the pixel signals in the direction where the signal changes less are used to detect the composite television. Since the C signal is separated from the signal, accurate separation is possible.

Next, the operation of the switching pulse generation circuit 26 will be explained.

As can be understood from FIG. 3, when focusing on a certain sample point, the sample point whose color subcarrier phase is inverted may be one line above or one line below. Sample point P of interest
Figure 5 is used to show the case where the sample point where the phase of the color subcarrier is inverted with respect to the sample point of interest is on one line. The case of one line below has been explained using FIG. 6, but in order to realize an actual YC separation filter, the switching pulse generation circuit 26 switches the first switch circuit 24a, It is necessary to generate a control pulse to switch the second switch circuit 24b between the case of FIG. 5 and the case of FIG. 6. For example, this is the absolute value of the difference between the sample value of the sample point P5 of interest and the sample value of the corresponding sample point P2 on one line, and the sample value of the sample point P5 and the corresponding one line. Compare the absolute value of the difference with the sample value of the sample point P8 below, 1 (sample value of the sample point P5) - (sample value of the sample point P2) 〉1 (sample value of the sample point P5) - (sample value at the sampling point P8), the switching pulse generation circuit 26 allows the first switch circuit 24a to pass the output signal of the first 1/2 times circuit 51, as explained in FIG. In this case, the second switch circuit 24b generates a control signal to pass the output signal of the fifth delay circuit 21C, and in the opposite case, the first switch circuit 24a passes the output signal of the fifth delay circuit 21C. delay circuit 2
A control signal is generated so that the second switch circuit 24b passes the output signal of the circuit 1a and the output signal of the second 1/2 multiplier circuit 52.

For example, if the phase of the sampled signal is fixed, the pattern shown in FIG. The switching pulse generation circuit 26 may be configured to switch for each sample point.

Further, the first subtraction circuit (luminance signal output circuit) 91 subtracts the output signal of the third switch circuit 24C from the output signal of the seventh delay circuit 21e. Since the output signal of the seventh delay circuit 21e is a composite separated C signal, the output signal of the first subtraction circuit 91 becomes a Y signal.

In this embodiment, YC separation is performed using the sample points on the line one line above and below the sample point of interest, or the values of the sample points two samples on the same line. Changes in each of these values are small (more accurate YC separation can be achieved than in the past). Furthermore, the system uses the values of neighboring sample points to detect the direction in which the signal changes less, and uses the output of the filter in that direction to extract the Y signal, so it can be used when the image changes suddenly. Therefore, it is possible to reproduce the received image without cross color or cross luminance.

Furthermore, in the above embodiment, during A/D conversion, the frequency is four times the color subcarrier frequency and the phase thereof is 45% with respect to the color difference signal.
Since A/D conversion is performed using a sampling pulse that is phase-advanced or phase-delayed, the inverted sampling point whose color subcarrier is inverted from that of the sampling point of interest is placed at one line of the sampling point of interest.
Therefore, in this embodiment, the conventionally used two-line memory is unnecessary, and one
Line memory is sufficient and the cost is low.

〔Effect of the invention〕

As described above, according to the present invention, the luminance signal and the chrominance signal are separated using a signal whose waveform in the vertical and horizontal directions changes more gradually in the composite television signal. This has the advantage of being able to accurately separate luminance signals and color signals by following sudden changes in the image, and to reproduce received images without cross color or cross luminance. In addition, since the composite television signal is sampled with a sampling pulse whose frequency is four times the color subcarrier frequency and whose phase is 45 degrees ahead or behind the color difference signal, the color subcarrier Inverted sample points whose phase is inverted to that of the sample point of interest can be obtained on lines one line above and below the line of the sample point of interest. Processing can be performed using a line memory, which has the effect of reducing the cost of the device.

[Brief explanation of the drawing]

Figure 1 shows a two-dimensional array of sampled signal sequences on the screen when a PAL system composite video signal is sampled at a sampling frequency four times the color subcarrier frequency, and Figure 2 shows a two-dimensional array of the sampled signal sequence on the screen when a PAL system composite video signal is sampled at a sampling frequency that is four times the color subcarrier frequency. FIG. 3 is a diagram showing the configuration of a luminance signal/chrominance signal separation filter according to an embodiment of the present invention, and FIG. 4 is a diagram showing the configuration of a PAL luminance signal/chrominance signal separation filter according to an embodiment of the present invention. Figures 5 and 6 are diagrams showing the on-screen arrangement of sampled signal sequences obtained when a PAL video signal is sampled using pulses, respectively, according to an embodiment of the present invention shown in Figure 3. FIG. 3 is a diagram for explaining the operation. 2... A/D converter, 3... Sampling pulse generation circuit, 24c... Third switch circuit (selection circuit), 70
...Vertical filter and horizontal filter, 80.
...detection circuit, 91...first subtraction circuit (luminance signal output circuit). Note that the same reference numerals in the figures indicate the same or equivalent parts. Agent Masuo Oiwa+ 1 1 1 1 l Figure 2

Claims (1)

[Claims] (11 In a PAL system luminance signal/chrominance signal separation filter that separates and extracts a luminance signal and a color signal from a PAL system composite television signal, the frequency is four times the color subcarrier frequency and A sampling pulse generation circuit that generates a sampling pulse whose phase is advanced or delayed by 45 degrees with respect to the color difference signal, and A that converts the input analog composite television signal into a digital signal using the sampling pulse.
/D converter and the value of each sample point obtained by the A/D conversion and its color subcarrier phase in the line one line above and below each sample point is inverted with that of each sample point. A vertical filter and a horizontal filter extract a color signal at each sampling point using the values of sampling points neighboring the sampling point, and a detection circuit that detects a direction in which there is little change; a selection circuit that selects and outputs the output of a filter in a direction where signal changes are small among the vertical filter and horizontal filter according to the detection result of the detection circuit; A PAL luminance signal/chrominance signal separation filter comprising: a luminance signal output circuit that separates a chrominance signal output from the selection circuit from a digitized composite television signal and outputs a luminance signal. (2) As the neighboring sample points in the calculation of the vertical filter, those selected according to the value of the sample point and the values of sample points one line above and below it are used. PAL luminance signal described in range 1.
Color signal separation filter. (3) As neighboring sample points in the calculation of the vertical filter, select a plurality of sample points that have a predetermined positional relationship with each sample point in the order determined by the line of the input PAL signal. P according to claim 1, characterized in that the selected one is used by switching.
AL method luminance signal color signal separation filter.