JPS60253392A - Adaptive luminance and color signal separating filter - Google Patents

Abstract

PURPOSE:To accurately separate Y and C signals in response even to a sudden change of a picture by using a signal with which the vertical and horizontal waveforms of a composite TV signal have slower changes to separate the luminance signal from the color signal. CONSTITUTION:When the sample value having a sample point P9 is outputted from an A/D converter 2 at a certain time point T, the output of a delay circuit 161 is equal to the sample value of a sample point P8 adjacent the point P9. The output of a delay circuit 41 is equal to the sample value of a sample point P6 which is slower than the P9 by an amount equal to two horizontal scan lines. The output of a delay line 162 goes to the sample value of a sample point P5 adjacent to P6. The output of a delay circuit 163 goes to the sample value of a sample point P4 adjacent to P5. The output of a delay circuit 42 is equal to the sample value of a sample point P2 which is lower than the P5 by two scan lines. A comparator 14 compares the output signal TV' of an adder circuit 22 with the output signal TH of an absolute value circuit 132 and controls a switch circuit 15. Then the outputs of the subtractor circuits 71 and 72 are outputted to an output terminal 10 at TV'<TH and TV'>=TH respectively.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to an adaptive luminance signal/chrominance signal separation filter;
In particular, from the PAL composite video signal to the luminance signal (hereinafter referred to as
(hereinafter referred to as the Y signal) and a color signal (hereinafter referred to as the C signal)
This relates to a luminance signal chrominance signal separation filter (hereinafter referred to as VC separation filter) that separates and extracts a luminance signal and a chrominance signal,
The present invention relates to an adaptive luminance signal/chrominance signal separation filter that digitally separates a Y signal and a C signal after converting a PAL analog composite television signal into a digital signal.

[Prior art] In the current color television standard system, the Y signal and C signal are transmitted as a frequency multiplexed composite signal, and the receiver must correctly separate the Y signal and C signal from the received composite signal. There is a need to.

Generally, a composite television signal P of the PAL system is composed of a one-variant signal Y and a color signal C obtained by quadrature two-phase modulation of two color difference signals U and V (or I and Q) at a color subcarrier frequency fsC. It is a composite signal and can be written as the following equation.

p −v + c −'y'TjJsill (2πfscj>±VCO5
(2πLscj) In the above equation, the sign par ±″ added to the third term is
In the signal P mentioned above, i + u on odd scan lines.

It is "°-" for even-numbered scanning lines. That is, the V component is inverted for each scanning line. Set the frame frequency to f'(25)-1
z), the field frequency is fv (50)-12), and the horizontal scanning frequency is h (15,625kHz), then the color subcarrier frequency f as described above.

, Is c = (284-1/4+1/'625)f
The following relationship is established: H=(2841/4+1/625)62 5/2·fv − (284−1/4+1/625)621F. That is, the color subcarrier frequency rsc and the horizontal scanning frequency f described above. is in the relationship of 1/4 line offset. Therefore, the sampled signal sequence obtained by synchronously sampling the PAL composite television signal at a sampling frequency ``, which is four times the color subcarrier frequency, appears on the screen in a two-dimensional manner as shown in Figure 1. In other words, the same color signal phase is repeated every four lines.

In general, in order to maintain compatibility with black and white television signals, a receiver (one receiver) receives Y It is necessary to accurately separate the signal and the C signal.

FIG. 2 is a diagram that does not show the configuration of a conventional YC separation filter. Next, the configuration of a conventional YC separation filter will be explained with reference to FIG. An input terminal 1 receives a PAL analog composite television signal. This analog composite television signal is given to an A/D converter 2. A sampling pulse signal is applied to this Ay'D converter 2 from a sampling pulse generation circuit 3. Therefore, A
/D converter 2 converts the input analog composite television signal into a digital signal based on the sampled pulse signal. The output of the A/D converter 2 is the first one. It is input to second delay circuits 41 and 42. These delay circuits 41 and 42 each delay the above-mentioned Δ for one horizontal scanning period.
/' This is to delay the sampling signal which is the output of the D conversion circuit 2.

Also, the output of the A/'D converter 2 is the ``1st 1,''
The output of the delay circuit 41 is applied to the subtraction circuit 7 via the 1z2'lEt circuit 5, and the output of the delay circuit 42 is applied to the subtraction circuit 1 through the quadrupling circuit 61. /4x circuit 6
2 to the subtraction circuit 7. Subtraction circuit 7 is 1z
From the output of the doubling circuit 5 to the first and second 1z quadrupling circuits 6
It is configured to calculate the output of 1.62 by i. The output of the subtraction circuit 7 is outputted to the output terminal 10 via the pattern direction band-pass filter 8, and is also given to the second subtraction circuit 9.The second subtraction circuit 9 also receives the output of the delay circuit 41. Therefore, the subtraction circuit 9 subtracts the output signal of the horizontal bandpass filter 8 from the output signal of the first delay circuit 41. The output signal of the subtraction circuit 9 is outputted from the output terminal 11 as a Y signal. It will be done.

Next, the operation of the conventional YC separation filter shown in FIG. 2 will be explained. The sampling pulse generation circuit 3 is an oscillation circuit that oscillates synchronously at a frequency "," which is four times the color subcarrier frequency fsC of the composite television signal input to the input terminal 1, and its output is A, /D. The A/D converter 2 converts the analog signal applied to the input terminal 1 into a digital signal using the signal from the sampling pulse generation circuit 3.The A/D converter 2 converts the analog signal applied to the input terminal 1 into a digital signal. If we pay attention to the phase of the C signal, the sampled signal sequence of the converted PAL composite color television signal will be arranged on the screen as shown in FIG. 1.

In other words, the phase of the C signal returns every 4 lines, and for lines that are two lines apart above or below (see -2>, (additional +2)), the phase of the color subcarrier of the color signal component is 1801 The banquet has changed, that is, it has been reversed.

The 1/2x circuit 5 converts the output of the first delay circuit 41 into 1/2x.
The output of the 1/2 multiplier circuit 5 is input to the subtraction circuit 7. Further, the first 1/4 times circuit 61 is the above-mentioned A/4
The output of the D conversion @2 is multiplied by 1/4, and the output of this 1/4 multiplication circuit 61 is
Furthermore, the second 1/4 f & circuit 62 multiplies the output of the second delay circuit 42 by 1/4, and the output of this 1/4 multiplier 62 is It is input to circuit 7. Therefore, the subtraction circuit 7 subtracts the output of the first 1/4 times circuit 61 and the output of the second 1,74 times circuit 62 from the output of the 1/2 times circuit 5.

Therefore, the output Hc(rL, +n) of this subtraction circuit l
is, HC (see, El) = 1/4 (-P (see-2, v
a)-! ,,2P <a, m > −p (fL+
2. m)) yell. Here, P (i, ll1
) is Ii! in the standing line! Indicates the sample value of the eye sample point.

The output @Ha (Q, +11) of the subtraction circuit 7 is given 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 removes the Y signal component contained in the output signal ()-IC(A, III) of the subtraction circuit 7. This filter is, for example, Hh (,Z)-1/32 (1-Z-' )2 (1
+Z-')' (1+Z-8). That is, the C signal is obtained at 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. Since this subtraction circuit 9 subtracts the color signal from the composite television signal, a Y signal is obtained at the output of the subtraction circuit 9. Therefore, output terminals 10 and 1
1, a C signal is obtained from the horizontal band pass filter 8, and a YM@ signal is obtained from the subtraction circuit 9.

As mentioned above, conventional YC separation filters are constructed by fixing and combining vertical and horizontal FuC filters, and in addition, the pixels that are the sampling series of the television signal are adjacent on the screen. It was based on the assumption that things that are different 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, resulting in interference such as cross color and cross luminance, which significantly impairs the quality of the reproduced image.

[Object of the Invention] Therefore, the main object of the present invention is to detect the attributes of a composite television signal in a small area and adaptively switch the vertical filter and the horizontal filter.
An object of the present invention is to provide an adaptive luminance signal/chrominance signal separation filter that can achieve accurate separation of Y and C signals.

The above objects and other objects and features of the present invention will become more apparent from the detailed description given below with reference to the drawings.

[Embodiment of the Invention] FIG. 3 is a block diagram showing the electrical configuration of an embodiment of the invention. In FIG. 3, the same input terminal 1, A/D converter 2, and sampling pulse generation circuit 3 as shown in FIG. 2 are used. Furthermore, the YC separation filter in one embodiment of the present invention includes first and second delay circuits 41 and 42, a 1/2 multiplier circuit 5, and a first . the second 1/4 multiplier circuit 61.62; Second. The third and fourth subtraction circuits 71, 72, 73, 74, the subtraction circuit 9, and the first . Second. Third addition circuit 121, 122.123
, first and second absolute value circuits 131 and 132, comparison circuit 14, switch circuit 15, and third . M4. Fifth
．． Sixth delay circuit 161.162. -163, 164, and a constant generation circuit 17.

The first and second delay circuits 41 and 42 are connected to the A/D converter 2.
The output is delayed by two horizontal scanning periods. The first adder circuit 121 adds the output of the third delay circuit 161 and the output of the second delay circuit 42 , and the first 1/4 multiplier circuit 61 adds the output of the third delay circuit 161 and the output of the second delay circuit 42 . It multiplies the output by 1/4. Moreover, the 1/2 times circuit 5 is the fourth
The output of the delay circuit 162 is multiplied by 1/2. The first subtraction circuit 71 extracts the first 1 from the output of the 1/2 multiplication circuit 5.
The output of the /4x circuit 61 is subtracted. moreover,
The second adder circuit 122 is configured to add the output of the fifth delay circuit 163 and the output of the first delay circuit 41 , and the second 1/4 times circuit 62 is configured to add the output of the fifth delay circuit 163 and the output of the first delay circuit 41 . It is configured to multiply the output by 1/4. Furthermore, the second
The subtraction circuit 72 calculates the second 1/2 from the output of the 172x circuit 5.
The output of the quadrupling circuit 62 is subtracted.

Furthermore, the respective outputs of the third delay circuit 161 and the second delay circuit 42 are subtracted by a third subtraction circuit 73, and the absolute value of the output is taken by the first absolute value circuit 131.

Furthermore, the respective outputs of the first delay circuit 41 and the fifth delay circuit 163 are subtracted by a fourth subtraction circuit 74, and the absolute value of this output is taken by a second absolute value circuit 132.

The output of the first absolute value circuit 131 is sent to the third adder circuit 12.
3, and this third adder circuit 123 is provided with a predetermined constant K formed by the constant generating circuit 17. Therefore, the third adder circuit 123 is the first absolute value circuit 13
1 and the output of constant generation circuit 17 are added. Third
The output signal of the adder circuit 123 and the second absolute value circuit 132
The output signal of is given to the comparison circuit 14, which compares the outputs of both and gives a control signal to the switch circuit 15. The switch circuit 15 is provided with the output signal of the first subtraction circuit 71 and the output signal of the second subtraction circuit 72, and selects either one based on the control signal and outputs it as the C signal to the output terminal. Output to 10. Further, the signal selected by the switch circuit 15 is also given to the subtraction circuit 9, and the subtraction circuit 9 receives the output of the first delay circuit 41 and the switch circuit 15.
The output from the Y signal is subtracted from the Y signal, and the result is output to the output terminal 11 as a Y signal.

FIG. 4 is a diagram specifically showing the operation of an embodiment of the present invention, in which symbols are attached to some of the sampling series shown in FIG. 1 described above.

Next, the operation of the YC filter shown in FIG. 3 will be explained with reference to FIG. 4. Sampling pulse generation circuit 3
oscillates synchronously at a frequency r, which is four times the color subcarrier frequency rsc of the composite television signal applied to the input terminal 1. The output signal of this sampling pulse generation circuit 3 is A/
It is applied to the D converter 3. Therefore, the A/[) converter 3 converts the analog composite signal applied to the input terminal 1 into a digital signal using the signal from the sampling pulse generation circuit 3. PA sampled by sampling pulse
The sampling sequence of the L system composite television signal is arranged on the screen as shown in FIG. 1 above.

If the A/D converter 2 outputs the sample value of the sample point P9 at 6 degrees below the current time, the output of the third delay circuit 161 is the sample value of the sample point P8 near the sample point P9. It becomes a sample field.

The output of the first delay circuit 41 is a sample value of a sample point P6 delayed by two horizontal scanning lines from the sample point P9.

The output of the fourth delay circuit 162 is a sample value of a sample point 1]5 near the sample point P6 mentioned above.

The output of the fifth delay circuit 163 becomes the sample value of a sample point P4 near the sample point P5 described above.

The output of the second delay circuit 42 is the sample value of a sample point P2 delayed by two horizontal scanning lines from the sample point P8.

The first adder circuit 121 outputs the output of the first delay circuit 161 (
sample point P8) and the output of the second delay circuit 42 (sample point P8);
2>, and the first 1/4 multiplying circuit 61 is configured to multiply the output of the first adding circuit 121 by 1/4. Furthermore, the 172x circuit 5 is configured to multiply the output (sample point P5) of the fourth delay circuit 162 by 1/2. Furthermore, the first subtraction circuit 71 has 17
Since this is a circuit that subtracts the output signal of the first 1/4 times circuit 61 from the output signal of the 72 times circuit 5, the output signal of the subtraction circuit 71 is 1/4 (sample value of the sample point P2) + 1 /2 (P
Sample 1 of sample point 5! I)-1/4 (sample value of sample point P8).

Further, the second addition circuit 122 is a fifth delay circuit] 63
(sample point P4) and the output of the first delay circuit 41 <
sample point P6), and the second 1/
The quadruple circuit 62 is configured to multiply the output of the second adder circuit 122 by 174 times. Roughly speaking, the second subtraction circuit 7
2 subtracts the output of the second 17' quadruple circuit 62 from the output signal of the 1/2-circuit 5. Therefore, the output signal of this subtraction circuit 72 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, a third delay circuit 161. The respective outputs of the second delay circuits 42 are applied to a third subtraction circuit 73, and the absolute value of the output signal of this subtraction circuit 73 is taken by a first absolute value circuit 131. Therefore, the first absolute value circuit 13
The output signal TV of 1 is 1-v=1 (sample value of sample point Pg)-(sample value of sample point P2)1. Further, the first delay circuit 41. Fifth delay circuit 1
The respective outputs of 63 are applied to a fourth subtraction circuit 74, and the absolute value of the output signal of this subtraction circuit 74 is taken by a second absolute value circuit 132. Therefore, the output signal TH of the second absolute value circuit 132 becomes T, H=l (sample value 1 of the sample point P6 (sample value of the sample point P4) 1.

The output signal Tv of the first absolute value circuit 131 described above is
is applied to the adder circuit 123 of. The constant generation circuit 17 is
The third adder circuit 12 generates a predetermined constant K of
3. The third addition circuit 123 adds the output signal of the first absolute value circuit 131 and the output signal of the constant generation circuit 17. Therefore, the output TV of the adder circuit 123 becomes Tv - Tv + K.

The output signal Tv' of the third adder circuit 123 and the output signal TM of the second absolute value circuit 132 are applied to the comparison circuit 14. Comparison circuit 14 compares the magnitudes of Tv and TN described above, and sends a control signal to switch circuit 15, which will be described next. The output signal of the first subtraction circuit 71 and the output signal of the second subtraction circuit 72 are applied to the switch circuit 15, and the above-mentioned comparison circuit 14 receives the output signal V′ +
When T H is Tv'< -rs, the output of the switch circuit 15 becomes the output signal of the first subtraction circuit 71, and when Tv'≧Tel, the output of the switch circuit 15 becomes the output signal of the second subtraction circuit 71. A control signal is sent to the switch circuit 15 so that the output signal of the subtraction circuit 72 becomes an output signal of Since the pixel signal in the direction where the signal changes less is detected and the 04a signal is separated from the composite television low signal using the pixel signal in the direction where the signal changes less, accurate separation is possible. 1
The constant generated in step 7 is used to prevent a decrease in vertical resolution due to the use of sample values of sample points that are compressed by two lines above and below in the vertical direction.
By setting ilK, it is possible to prevent the vertical resolution from becoming low.

Further, the subtraction circuit 9 is configured to subtract the output signal of the switch circuit 15 from the output signal of the fourth delay circuit 162 described above. Further, the output signal of the fourth delay circuit 162 is a composite television signal, and the output signal of the fourth delay circuit 162 is a composite television signal.
Since the output signal of is a C signal separated from the composite television signal, the output signal of the subtraction circuit 9 is a Y signal.

[Effects of the Invention] As described above, according to the present invention, the luminance signal and the chrominance signal are separated using the signal in which the vertical and horizontal waveforms of the composite television signal change more gradually. With this configuration, it is possible to accurately separate luminance signals and color signals without losing resolution by following sudden changes in the image, and it is possible to reproduce received images without cross color or cross luminance. .

[Brief explanation of drawings]

FIG. 1 is a diagram showing a two-dimensional array of sampled signal sequences on the screen when a conventional PAL system composite video signal is sampled at a sampling frequency four times the color subcarrier frequency. Second
The figure is a diagram showing the configuration of a conventional luminance signal chrominance signal separation filter. FIG. 3 is a diagram showing the electrical configuration of one embodiment of the present invention. FIG. 4 is a diagram for explaining in detail the operation of one embodiment of the present invention, in which symbols are attached to some of the sampling series shown in FIG. 1 described above. In the figure, 1 is an input terminal, 2 is an A/D converter, 3 is a sampling pulse generation circuit, 41.42, 161° 162.1
63 is a delay circuit, 5 is a 1/2x circuit, 61.62 is a 1/2x circuit, and 61.62 is a 1/2x circuit.
4x circuit, 71, 72, 73.74.9 is subtraction circuit, +
21. 'I 22, 123 is an adder circuit, 131, 1
32 is an absolute value circuit, -14 is a comparison circuit, 15 is a switch circuit, and 17 is a constant generation circuit. Agent Masu Oiwa No. 1 1110---△----・- 111■-C>-m-Rho 1-1・--1mu--〇- 11-bit--1- ■- 11-○---Δ---・- m--■-C＞-One bite- ○: Y+C, △: Y1C2 ・: Knee C2 muni Y-C:z Figure 1- Muu〇−−−△−−− Rai〉 α−2)−1
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Claims (1)

[Scope of Claims] Conversion means for sampling an analog composite video signal at a sampling frequency four times the color subcarrier frequency and converting it into a digital signal, a first delay means, a first addition means, and a first subtraction. a horizontal filter comprising means and a first multiplication means, a vertical filter comprising a second delay means, a second addition means, a second subtraction means and a second multiplication means; switching means for switching between the horizontal filter and the vertical filter according to an input image, based on sample points and neighboring sample values in the vertical or horizontal direction on the screen in which the phase of the color subcarrier is reversed; Equipped with an adaptive luminance signal and chrominance signal separation filter.