KR920005203B1 - Television circuit - Google Patents

Abstract

The vertical complementary color detector is to re-extract color signal from brightness signal when brightness and color signal dividing process has some fault so that color variation between lines becomes complementary. The circuit comprises a bandpass filter (1) for extracting color subcarrier signal having frequency of 3.58 MHz from brightness signal, a brightness signal checker (2) for checking the subcarrier signal, a color signal checker (4) for checking the color signal of current line and former line, a phase checker (3) for detecting the phase difference between the brightness signal and the color signal (C), and an AND gate (5) for generating control signal (CS).

Description

TV's Vertical Compensation Color Detector

1 is a circuit diagram of a conventional vertical complementary color change detector.

2 is a circuit diagram of a vertical complementary color change detector according to the present invention.

3 is a circuit diagram showing the removal of the color expression information and the return of the chroma signal from the luminance signal of the present invention.

4 is a graph showing the frequency characteristic diagram of the bandpass filter of FIG.

5 is a phase relationship diagram of subcarriers when the complementary color changes vertically.

6 is a luminance / chromatic signal separation diagram by the line separation filter at the complementary color change point vertically.

* Explanation of symbols for main parts of the drawings

1: Band Pass Filter (BPF) 2: Luminance Signal Determinator

3: phase relation judge 4: chromatic signal judge

5: AND Gate 6: Low Pass Filter

7,8: selector (MUX) 2a, 2a, 4a, 4a ': absolute value calculator

2b, 3b, 4b, 4b ': Comparator 2c, 3c, 4c, 4c': Threshold generator

3d: line delay

The present invention is to separate a luminance signal and a chroma signal from a composite video signal by a separation filter in a color television, and in particular, when the luminance signal and the chroma signal are separated from the composite video signal, the signal changes vertically. It is about the vertical complementary color change detector of a television for re-isolating that color expression information is mixed in luminance signal when the change of color acid is complementary to the liver.

In general, when the signal is changed vertically when the luminance signal and the chromaticity signal are separated from the composite image signal by the separation filter, the separation performance is not appropriate. At this time, the luminance information is mixed into the chroma signal or the color expression information is mixed into the luminance signal, and a sequence of points appears at subcarrier frequency intervals.In general, according to the National Television System Committee (NTSC) standard, adjacent lines are adjacent to each other. The phase carrier of the color carrier should be 180 °. When the complementary color changes vertically, the phase carrier of the color carrier between adjacent lines does not occur, so all color expression information is mixed with the luminance signal, and the chroma signal becomes zero.

In the separation filter for vertical change processing of US Patent Application No. 4,694,331, which is designed to detect such a vertical complementary color change state, the luminance signal separated from the bandpass image signal of the current line and the bandpass image signal of the previous line are used. In this paper, we propose a method to detect the vertical complementary color state by comparing the filtered color signal at and the relatively small luminance signal separated from the bandpass image signal of the previous line based on the correlation.

Referring to the structure of the conventional vertical complementary color change detector as described above in detail as follows.

FIG. 1 is a circuit diagram of a conventional vertical complementary color shift detector. As shown therein, a digital composite image signal YC is applied from a band pass filter 1 and separated into a luminance signal Y and a chroma signal C. As shown in FIG. The separation filter 2 is connected to the line delay unit 3 which delays the luminance signal Y, and multiplied by the luminance signal Y and the chroma signal C outputted from the line delay unit 4 to output the multiplier. Connected to a multiplier (5), and the output of the multiplier (5) is composed of a comparative reference voltage source (6a) and a comparator (6b) through a low pass filter (7) so that the comparative reference voltage source (6a) and the low pass filter (7) The signal output from the signal is connected to a threshold detector 6 for comparing and detecting the signal output from the input terminal of the AND gate 9, and the line delay unit 3 is composed of a comparison reference voltage source 8b and a comparator 8a. The threshold level of the luminance signal Y and the comparison reference voltage source 8b delayed by the time when one scan line is scanned in the delay unit 3 is performed. Is connected to a threshold detector 8 which compares and detects the signal to the type force terminal of the AND gate 9, and obtains a control signal for combining the image signal with the output of the AND gate 9.

In the conventional vertical complementary color shift detector configured as described above, the composite image signal YC converted into modulated color representation information of 3 MHz to 4 MHz and the high frequency component signal of the luminance signal through the band pass filter 1 is separated from the filter 2. After the luminance signal (Y) and the chroma signal (C) are separated into the luminance signal (Y) is applied to the multiplier (5) and the line delay unit (3), the chroma signal (C) is connected to the line delay unit (4) Delayed by one time the horizontal scan line of the chroma signal (C) through the () is applied to the multiplier (5). The multiplier 5 multiplies the signal delayed by the time for which the horizontal scan line of the luminance signal Y and the chroma signal C are scanned and applied to the comparator 6b configured in the threshold detector 6 through the low pass filter 7. In this case, the comparator 6b compares the threshold level output from the reference voltage source 6a with the signal output from the low pass filter 7, and outputs a Dirkman high (H) signal with the threshold level to the end gate 9. It is applied to the input end of.

On the other hand, the luminance signal Y separated by the separation filter 2 is applied to the comparator 8b configured in the threshold detector 8 after being delayed by the time when one horizontal scan line is scanned in the line delay unit 3. Therefore, the comparator 8b compares the threshold level of the reference voltage source 8a with the signal delayed by the horizontal scan line period in the line delay unit 3, and outputs a high (H) signal when the threshold level is large. At the output of the end gate 9, a control signal for combining the image signals is output as a high (H) signal by applying a type force.

However, in the conventional vertical complementary color shift detector, a multiplier performs a phase comparison between the color component carrier 3.88MHz component in the luminance signal of the current line and the chromaticity signal of the previous line, which is performed by real-time control in actual hardware implementation. If one chip is used, the cost is high, and if the circuit is composed, the circuit configuration is complicated, and there is no chromatic signal or no judgment device of the current line. At the point where the subcarrier component appears, there was a problem in that it was determined that there was a change in complementary color vertically unlike the reality.

According to the present invention, in order to solve such a conventional problem, color information in a color video composite video signal is carrier-suppressed modulated and transmitted to a color carrier of 3.58 MHz, and the phase of the subcarrier is information about color. The information about this color concentration shows that the subcarrier frequency of 3.58 MHz is half the odd number of the line scanning ratio of 15.75 KHz, so that the phases of the subcarriers differ by 180 ° between adjacent lines. The luminance signal and the chroma signal are separated from each other. However, in the manner in which the color information is expressed as the phase of the subcarrier, a phase difference of 180 ° appears between complementary colors. When such a relationship is formed between adjacent lines, the phase difference is summed with the original phase difference of 180 ° between the inerger lines and eventually becomes the same.

In this case, nothing is left in the luminance signal and chroma signal separated by the separation filter. At this time, the luminance signal contains a subcarrier of 3.58 MHz, which is displayed like the representation of the minute details of the luminance. appear.

The present invention proposes a method for detecting such a case to remove color information that is erroneously mixed in the luminance signal and to recover the chroma signal. Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. Is as follows.

2 is a circuit diagram of a vertical complementary color shift detector according to the present invention. As shown therein, a band pass filter for detecting a subcarrier of 3.58 MHz in a luminance signal Y line-separated from a digital composite video signal by a separation filter ( 1) is connected to a subtractor 3e and composed of an absolute value calculator 2a, a comparator 2b, and a threshold generator 2c to detect a 3.58 MHz subcarrier component in the separated luminance signal Y. The absolute value calculator 2b, which is connected to the absolute value calculator 2e of the determiner 2 and outputs an input value as an absolute value, compares the output signal thereof with the threshold level output from the threshold value generator 2c. Connected to a comparator 2b, and the separated chroma signal C is composed of an absolute value calculator 4a, 4a ', a comparator 4b, 4b' and a threshold generator 4c, 4c '. It is connected to the absolute value calculator 4a 'of the chromaticity signal determiner 4 which detects the presence or absence of the separated chromaticity signal C. Separated luminance consisting of a line delay (3d), a subtractor (3e), an absolute value calculator (3a), a comparator (3b) and a threshold generator (3c) for delaying the one scan line of the separated chroma signal (C) The difference between the output thereof and the output of the band pass filter 1 is calculated through the line delay unit 3d of the phase relationship determiner 3 which detects the phase relationship between the signal Y and the chroma signal C. It is connected to a subtractor 3e and connected to an absolute value calculator 4a configured in the chromaticity signal determiner 4, and the subtractor 3e calculates and outputs an input value as an absolute value. Through the comparator 3b for comparing and detecting the threshold level of the threshold value generator 3c and the output value of the absolute value calculator 3a, and for each absolute value calculator 4a configured in the chromaticity signal determiner 4 ( 4a ') is connected to each comparator 4b and 4b' that compares and detects its output value and the threshold level output from the threshold generators 4c and 4c ', and compares each comparison. (2b), (3b), (4b), (4b ') is configured to connect to the end gate (5) for generating a control signal (CS) to indicate that a complementary color change, depending on its output signal.

3 is a circuit diagram showing the removal of the color expression information and the return of the chroma signal from the luminance signal of the present invention. As shown therein, one side of the luminance signal Y separated from the separation filter is output from the end gate 5. And a counter 6c, 6d, 6e, line delayer 6a, 6b, and the like, connected to a selector 7 which selects and outputs one of two inputs according to the logic state of the control signal CS. The modified luminance signal Y 'is obtained by connecting to the selector 7 through the low pass filter 6 composed of the adder 6f, and the other side of the line separated luminance signal Y is a line delay unit 6a. (6b) and a counter (1a), (1b) (1c) and a subtractor (1d), connected to the adder (9) through a bandpass filter (1) covalently coupled with the lowpass filter (6), the line separation The chroma signal C is connected to the selector 8 and is inputted according to the logic state of the control signal CS output from the end gate 5 through the adder 9. One is selected and connected to the selector 8 which outputs the modified chromaticity signal C '.

Referring to the operation and the effects of the present invention configured as described above are as follows.

In the color signal of a color television, in the state in which the color signal is carrier-suppressed modulated and transmitted to the color carrier, the phase of the carrier represents the color tone and the amplitude represents the saturation of the color concentration, respectively.

At this time, the modulated subcarrier phase is 180 ° out of the complementary colors (for example, red and cyan, magenta and green, yellow and blue, etc.). When there is a change in complementary color vertically, for example, when the color is yellow until the nth line as shown in (b) of FIG. 5 and becomes blue at the n + 1th line as shown in (c), the phase of the nth line subcarrier The phases of the subcarriers of the n + 1th line become the same, and if they are the same color, the phases of the subcarriers between adjacent lines are 180 degrees different as shown in (a) and (b) of FIG.

When the composite video signal, i.e., the subcarrier signal of the nth line, the subcarrier signal of the n + 1th line, and the subcarrier signal of the n-1th line is separated by the line separation filter, the luminance signal and the chromaticity signal are separated. Since 1/2 (average) is used as the luminance signal and 1/2 of the difference between two adjacent lines is used as the chroma signal, separation cannot be performed properly at the color change point, and as shown in (a)-(d) of FIG. The chroma signal of the + 1th line (complementary color changing line) is incorrectly separated by the high frequency component of the luminance signal in the line separation filter.

In this way, when the color carrier signal 3.58 MHz is mixed in the luminance signal Y separated by the line separation filter and applied to the band pass filter 1, the band pass filter 1 receives the 3.58 MHz component of the color carrier signal in the luminance signal Y. The filter is applied to the absolute value calculator 2a configured in the luminance signal determiner 2 and the subtractor 3e configured in the phase relation determiner 3, and the absolute value calculator 2a is applied to the band pass filter 1. The comparator 2b compares the signal output from the absolute value calculator 2a with the threshold level input from the threshold generator 2c by calculating the absolute value of 3.58 MHz output from the absolute value and applying it to the comparator 2b. Is greater than the threshold level, a high (H) signal that determines that there is a high frequency component of 3.58 MHz in the luminance signal (Y) is applied to one end of the input of the end gate (5).

On the other hand, when the separated chromaticity signal C is applied to the line delay unit 3d configured in the phase relation determiner 3 and the absolute value calculator 4a configured in the chromaticity signal determiner 4, the line delay unit 3d ) Applies the chroma signal C of the previous line delayed by one line scanning period of the chroma signal C to the subtractor 3e and the absolute value calculator 4a, and the absolute value calculator 4a applies this input signal. The absolute value is calculated and applied to the comparator 4d.

Therefore, the comparator 4d compares the signal output from the absolute value calculator 4a with the threshold level output from the threshold generator 4c, and the chromaticity signal C of the previous line delayed by one line scanning period is the threshold level generator. If it is larger than the threshold level of (4c), a high (H) signal which determines that there is a chroma signal in the previous line is applied to the other input of the end gate 5, and all of the chroma signal (C) of the current line separated in the line is separated. Since the color accuracy is mismixed with the luminance signal Y, it is applied to the comparator 4b 'through the absolute value calculator 4a' of the chromaticity signal determiner 4 so that the comparator 4b 'is a threshold generator ( 4c '), when the threshold level is greater than the chroma signal C level of the current line, the high signal H that judges that there is no chroma signal C on the current line is output and the input of the end gate 5 is output. Is applied from the line delay unit (3d) and the band pass filter (1). The subtractor 3e receiving the 3.58 MHz components in the chroma signal C of all the lines and the luminance signal Y of the current line obtains the difference between these signals and applies them to the comparator 3b through the absolute value calculator 3a. . At this time, if the value obtained by the difference of the subtractor 3e does not exceed the threshold level of the threshold generator 4c, the comparator 4b outputs a high H, which is determined to be in phase, to the input terminal of the end gate 5. As a result, the output of the end gate 5 generates a high (H) level control signal CS, i.e., a signal indicating that there is a change in complementary color to the vertical, and is applied to the selectors 7 and 8.

FIG. 3 is a circuit diagram for correcting a luminance / chromatic signal that is incorrectly separated from a control signal CS that is determined to have a complementary color change vertically. The control signal CS output from the end gate 5 is selected from a selector 7 (8). Is applied to the selector 7, and is composed of counters 6c, 6d and 6e, line delayers 6a and 6b, and adder 6f. The multiplier is multiplied by a quarter through the counter 6c of the low pass filter 6 and applied to the adder 6f, and the luminance signal Y is transmitted through the line delay 6a and the counter (6a). 6d) is applied to the adder 6f after being delayed by 1/2 of the color carrier cycle, and delayed by 1/4 of the color carrier carrier through the line delays 6a and 6b to adder 6f. ), The adder 6f adds this signal and applies it to the selector 7.

In this way, the low-pass filter 6 removes the 3.58 MHz component in the luminance signal Y and applies it to the selector 7, and then the chroma signal C separated in line transmits the luminance signal Y to the line delay unit 6a. 6b, the counters 1a, 1b, 1c, and a subtractor 1d, which are passed through a bandpass filter 1, which picks out the 3.58 MHz component in the luminance signal Y, and adds the signal 9 to the adder. In addition, when applied to the selector 8, the selectors 7 and 8 select one of the two signals according to the control signal CS of the end gate 5, thereby correcting the luminance signal Y and the chroma signal C. ') Is sent to the luminance signal processor and the chroma signal processor, respectively, to obtain red, green, and blue video signals (R, G, B).

As such, the present invention improves the conventional problem of using a multiplier to detect the phase relationship between the 3.58 MHz component of the luminance signal of the current line and the chromaticity signal of the previous line. It is possible to realize more economical hardware by using the 3.58MHz component having the presence / absence of the colorless signal component of the previous line and the non-chromatic signal component of the previous line, as well as the new useful features that enhance the reliability.

Claims (2)

In the complementary color change detector for detecting a complementary color change by separating a luminance signal and a chromaticity signal with a line separation filter, a band pass filter for detecting a color carrier signal 3.58 MHz from the luminance signal Y separated by a line separation filter (1). ) Is composed of an absolute value calculator 2a, a threshold generator 2c, and a comparator 2b, and is connected to a luminance signal determiner 2 that determines the presence or absence of a subcarrier component of 3.58 MHz in the luminance signal Y. In addition, the chromaticity signal C, which is connected to the subtractor 3e, is composed of an absolute value calculator 4a, 4a ', a comparator 4b, 4b' and a threshold generator 4c, 4c '. Line delayer (3d), which is connected to the chromaticity signal determiner (4) for judging the presence or absence of the chromaticity signal of the current line and the newness signal of the previous line, and delays the chromaticity signal (C) by one line scanning period. And a subtractor 3e, an absolute value calculator 3a, a comparator 3b, and a threshold generator 3c, and the 3.58 MHz component of the luminance signal Y Dosin arc (C) phase relation determining unit (3) connected to the end gate (5) A television vertical complementary color change of the detector characterized by obtaining a control signal (CS) in a to detect a phase difference. 2. The luminance signal of claim 1, wherein the band pass filter 1 comprises a line delay unit 6a, 6b, a counter 1a, 1b, 1c, and a subtractor 1d. The high frequency component at (Y) is detected and the chroma signal C and the adder 9 are added to the selector 8, and the counters 6c, 6d, 6e and line delay ( The control signal is applied to the selector 7 by applying a luminance signal Y, which is covalently coupled with the low pass filter 6 composed of 6a) and 6b and an adder 6f, to which the 3.58 MHz high-band component in the luminance signal Y is removed. A vertical complementary color change detector of a television, characterized by outputting a luminance signal Y 'and a chromaticity signal C' modified according to CS.

Images