KR19990004711A - Color and Luminance Signal Separation Circuit - Google Patents

Abstract

A color and luminance signal separation circuit capable of separating a composite video signal into color and luminance signals without generating a hanging dot phenomenon on a screen is disclosed. The color and luminance signal separation circuit may include: a frequency separation unit for separating a continuous image signal that is continuously input into a low frequency luminance signal and a high frequency signal in which the luminance and color signals are interleaved; A comb filter for adaptively filtering the high frequency signals from the frequency separation unit and separating the high frequency signals into color and high frequency luminance signals; A first detector for detecting a color signal from the high frequency signal; A second detector for detecting a color signal from the high frequency luminance signal; A signal remover for removing a color carrier from the high frequency luminance signal; And a selector configured to selectively output one of a signal from the signal remover and a high frequency luminance signal from the comb filter in response to the first and second sensing signals from the first and second sensing units. In addition, the color signal is prevented from flowing into the high frequency luminance signal output from the comb filter, thereby preventing the occurrence of a hanging dot on the screen.

Description

Color and Luminance Signal Separation Circuit

The present invention relates to a circuit for separating a color signal and a luminance signal from a composite video signal, and more particularly, the present invention can separate the composite video signal into color and luminance signals without the occurrence of a hanging dot phenomenon on the screen. It relates to a color and luminance signal separation circuit.

In NTSC systems, frequencies up to 4 MHz are allocated to represent the maximum detail contrast in the horizontal direction. However, not all of the 4 MHz bands are required for color video signals. This is because for very small areas the human eye typically can only perceive luminance information.

Therefore, color information can be transmitted in a band smaller than the 4 MHz, and color signals modulated as the color carrier (3.58 MHz) by the above-described properties are put in a band much narrower than the luminance signal band.

For example, in the NTS method, an I signal component of a color signal modulated as a color carrier is used for a 1.3 MHz band, and a Q signal component uses a band of 0.5 MHz. Providing a wider band for the I signal component compared to the Q signal component of the color signal is because the I signal is better for color resolution.

Since the frequency of the color carrier is 3.58 MHz, the modulated color signal is interleaved on the high frequency sideband of the luminance signal to generate a composite image signal. The comb filter method is used to minimize the attenuation of the luminance signal and the interference by the luminance signal of the color signal when the luminance signal and the color signal interleaved to the luminance signal are separated from the composite image signal.

FIG. 1 is a circuit diagram showing the configuration of a conventional comb filter 10. An input terminal 11, one horizontal scanning time (H) delay unit 12, a first subtractor 13, 1/2 Amplifier 14, a band pass filter (BPF) 15, and a second subtractor 14.

Referring to the operation of the comb filter 10, when the composite video signal is input to the 1H delay unit 12 through the input terminal 11, the 1H delay unit 12 delays the input composite image signal by 1H. Output to the first subtractor 13.

The first subtractor 13 subtracts the 1H delayed composite video signal from the 1H delayer 12 from the current composite video signal input through the input terminal 11 to mutually attenuate the luminance signal component. A signal, that is, a color signal, is output to the half amplifier 14. Then, the half amplifier 14 amplifies the color signal output from the subtractor 13 by half and outputs it to the band pass filter 15.

The band pass filter 15 filters the 1/2 amplified color signal from the 1/2 amplifier 14 and provides it to the second subtractor 16 and outputs it to the outside. The second subtractor 16 subtracts the filtered 1/2 amplified color signal from the band pass filter 15 from the current composite video signal input through the input terminal 11 to externally output the luminance signal Y. Will output

In the comb filter 10, the color signal components of two consecutive horizontal scanning lines have a phase difference of 180 degrees with each other.

Accordingly, the comb filter 10 obtains only a color signal component by removing the luminance signal component from the composite video signal by calculating a signal difference between the composite video signal input with a 1H delay time and the currently input composite video signal. However, in the comb filter 10, when the composite image signal of one horizontal line including only the luminance signal and the composite image signal of one horizontal line including the color signal are adaptively filtered, the composite image including only the luminance signal The color signal is vertically shifted to a signal, thereby causing a hanging dot on a screen.

Accordingly, the present invention has been made in view of the foregoing, and an object of the present invention is to provide a color and luminance signal separation circuit capable of separating a composite video signal into color and luminance signals without generating a hanging dot phenomenon.

1 is a block diagram showing an example of a conventional comb filter;

2 is a block diagram showing a color and luminance signal separation circuit according to an embodiment of the present invention;

3 is a circuit diagram illustrating an example of the second detector illustrated in FIG. 2.

<Explanation of symbols for main parts of drawing>

201: input terminal 210: signal separation unit

220: frequency separation unit 221: low pass filter

222: subtractor 230: comb filter

240, 250: detector 251, 253, 255: sampling unit

252: logic operation unit 270: 3.58 MHz trap

280: selection unit 290: adder

Color and luminance signal separation circuit according to the present invention for achieving the above object is a frequency separation means for separating the low-frequency luminance signal and a high frequency signal interleaved luminance and color signals, the frequency separation means Comb filter means for adaptive filtering and separating the high frequency signal from the color signal into a high frequency luminance signal; first sensing means for detecting a color signal in the high frequency signal, and second sensing means for detecting a color signal in the high frequency luminance signal Signal removing means for removing a color carrier from the high frequency luminance signal, and a signal from the signal removing means and the comb filter in response to first and second sensing signals from the first and second sensing means. Selection for selective output of one of the high frequency luminance signals from the means It consists of a stage.

According to the above configuration, when the composite video signal separated from the composite video signal is separated into the color and luminance signals, the color signal is transferred to the luminance signal, thereby preventing the hanging dot phenomenon from occurring on the screen.

Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings.

2 is a diagram illustrating a color and luminance signal separation circuit 200 according to an exemplary embodiment of the present invention.

In FIG. 2, the color and luminance signal separation circuit 200 includes a signal separator 210, a first detector 240, a second detector 250, a 3.58 MHz trap 270, a selector 280, and an adder. 290.

The signal separating unit 210 separates the composite image signal 2011 continuously input through the input terminal 201 into a low frequency luminance signal 2211, a high frequency luminance signal Y ′, and a color signal C. Selects the generated low frequency luminance signal 2211 to the adder 290 and the high frequency luminance signal Y ′ to the first detector 240, the second detector 250, and the 3.58 MHz trap 270. The color signal C is output to the unit 280, respectively.

The signal separating unit 210 separates the composite video signal from the frequency separating unit 220 and the frequency separating unit 220 for separating the low frequency luminance signal and the high frequency signal 2221 into which the color and luminance signals are interleaved. The comb filter 230 is configured to adaptively filter the high frequency signal 2221.

The frequency separation unit 220 may include a low pass filter 221 for detecting the complex image signal 2011 and a low frequency luminance signal 2211, and a low pass filter 221 of the composite image signal 2011. And a subtractor 222 for attenuating the low frequency luminance signal 2211 to detect the high frequency signal 2221.

The first detector 240 detects a color carrier of 3.58 MHz from a high frequency signal 2221 from the frequency separator 220 of the signal separator 210, and detects the color carrier based on whether the color carrier is detected. 2401 and provides the generated first detection signal 2401 to the selector 280. When the first detector 240 detects a color carrier of 3.58 MHz from the high frequency signal 2221, generates a logic high signal as the first detection signal 2401, and when it does not detect the color carrier. A logic low signal is generated as the first detection signal 2401.

The second detector 240 detects a color carrier from the high frequency luminance signal Y ′ from the comb filter 230 of the signal separator 210, and a second detection signal 2501 according to whether the color carrier is detected. ) And provide the second detection signal 2501 to the selector 280. When the second detector 250 detects a color carrier of 3.58 MHz from the high frequency luminance signal Y ′, the second detector 250 generates a logic high signal as the second detection signal 2501 and fails to detect the color carrier. In this case, a logic low signal is generated as the second detection signal 2501.

3 is a circuit diagram illustrating an example of the second detector 250. In FIG. 3, the second detector 250 includes a sampling unit 251 and a logic operation unit 252.

The sampling unit 251 successively first samples a 3.58 MHz signal at every 1/2 cycle time of the color carrier from the high frequency luminance signal Y ′ from the comb filter 230, and performs the first sampling. Five consecutively generated sampling signals are provided to the logic operation unit 252 as first sampling signals. In addition, the sampling unit 251 changes the phase of the high frequency luminance signal Y 'by 90 degrees, and continuously converts a signal of 3.58 MHz in the phase shifted high frequency signal Y' every 1/2 cycle time of the color carrier. After the second sampling, the five sampling signals generated by the second sampling are provided to the logic operation unit 252 as a second sampling signal.

The sampling unit 251 includes a first sampling unit 253 for the first sampling and a second sampling unit 255 for the second sampling. The first sampling unit 253 includes first to fourth delayers 2531 to 2534 connected in series. The first to fourth delayers 2253 to 2534 are connected in series to output the high frequency luminance signals Y 'which are respectively inputted by a time corresponding to a half cycle of the color carrier. The input and output signals of the first to fourth delayers 2253 to 2534 are output to the logic operation unit 252 as the first sampling signal. The second sampling unit 254 is composed of fifth to ninth retarders 2581 to 2545 connected in series. The fifth delay unit 2541 delays the high frequency luminance signal Y ′ from the comb filter 230 by a quarter of a color carrier period.

The sixth to ninth delayers 2252 to 2545 are the same as those of the first to fourth delayers 2253 to 2534 of the first sampling unit 253. The luminance signal is delayed by time corresponding to one-half period of the color carrier, and the signal of the input / output terminal is output to the logic operation unit 252 as the second sampling signal.

The logic operation unit 252 performs a logic operation on the first and second sampling signals from the sampling unit 251, and outputs a logic result signal generated by the logic operation as the second detection signal 2501. The logic operation unit 252 is configured with first to fifth logic gates 255 to 259 to logically operate the first and second sampling signals from the sampling unit 251. The first and second logic gates 255 and 256 are the first sampling signal, the third and fourth logic gates 257 and 258 are the second sampling signal, and the fifth logic gate 259. ) Logically operates the first to fourth logic result signals of the first to fourth logic gates 255 to 258.

The first logic gate 255 generates a first logic signal 2551 by logically multiplying the second and fourth signals inverted from the first sampling signal with the remaining three signals, and generates the first logic signal. 2255 to the fifth logic gate 259. The second logic gate 256 logically multiplies the first, third, and fifth signals that are not inverted by the first logic gate 255 with the remaining two signals, thereby performing a second logic signal 2551. ) And provide the second logic signal 2561 to the fifth logic gate 259. The third logic gate 257 generates a third logic signal 2571 by logically multiplying the second and fourth signals of the second sampling signal by the inverted signal and the remaining three signals, and generates the third logic signal. 2257 is provided to the fifth logic gate 259. The fourth logic gate 258 logically multiplies the first, third, and fifth signals that are not inverted by the third logic gate 257 with the other two signals, thereby performing a fourth logic signal 2601. ) And provides the fourth logic signal 2571 to the fifth logic gate 259. Then, the fifth logic gate 259 logically sums the first to fourth logic signals to generate a fifth logic signal 2501, and transmits the fifth logic signal 2501 to the second sensing signal 2501. And outputs to the selection unit 280 as.

The 3.58 MHz trap 270 generates a trap signal 2701 by removing a 3.58 MHz signal from the high frequency luminance signal Y ′ from the comb filter 230 and generates the trap signal 2701. Provided at 280.

The selector 280 responds to the first and second sensing signals 2401 and 2501 from the first and second detectors 240 and 250, and generates a high frequency luminance signal from the comb filter 230. Y ') and one of the trap signals 2701 from the 3.58 MHz trap 270 are selected and provided to the adder 290 as a hanging dot removal signal 2821.

The selector 280 responds to the first and second sensing signals 2401 and 2501 from the first and second detectors 240 and 250, and generates a high frequency luminance signal from the comb filter 230. Y ') and a control signal generator 281 and a switch 282 to select one of the trap signals 2701 from the 3.58 MHz trap 270. A logic low signal is input to the control signal generator 281 as the second detection signal 2501 from the second detector 250 or a first signal from the first and second detectors 240 and 250. And when a logic high signal is input as both of the second sensing signals 2401 and 2501, the control signal generator 281 generates a logic high signal as the control signal 2811. The control signal generator 281 receives a logic low signal as the first sense signal 2401 from the first and second detectors 240 and 250, and a logic high signal as the second sense signal 2501. When a signal of? Is input, the control signal generator 281 generates a logic low signal as the control signal 2811.

In addition, the switch 282 responds to the control signal 2811 from the control signal generator 281 and the high frequency luminance signal Y ′ from the comb filter 230 and the 3.58 MHz trap 270. A first input terminal S1 connected to the high frequency luminance signal output terminal of the comb filter 230 and an output terminal of the 3.58 MHz trap 270 to selectively output one of the trap signals 2701 from the trap signal 2701. The connected second input terminal S2 and an output terminal connected to one input terminal of the adder 290 are provided. The switch 282 is connected to the first input terminal S1 when the logic high signal is input as the control signal 2811 from the control signal generator 281 to be connected to the first input terminal S1. The high frequency luminance signal Y 'input through the output to the adder 290, on the contrary, when the logic low signal is input as the control signal 2811 from the control signal generator 281, The trap signal 2701 connected to the second input terminal S2 and input through the second input terminal S2 is output to the adder 290.

The adder 290 generates the luminance signal Y by adding the high frequency luminance signal from the switch 282 and the low frequency luminance signal 2211 from the signal separator 210.

Hereinafter, the operation of the color and luminance signal separation circuit 200 having the above configuration will be described in detail.

The composite video signal 2011 inputted to the signal separator 210 through the input terminal 201 is inputted to the frequency separator 220 of the signal separator 210 to the frequency separator 220. As a result, the low frequency luminance signal 2211 and the color and luminance signals are separated into the interleaved high frequency signal 2221. The low frequency luminance signal 2221, which is separated from the composite image signal by the frequency separation unit 220, is input to the adder 290, and the high frequency signal 2221 is input to the comb filter 230.

The comb filter 230 separates the high frequency signal 2221 into a color C and a high frequency luminance signal Y ′ using a correlation between the scan lines of the composite image signal. However, when the correlation between the scan lines of the composite image signal input to the comb filter 230 is low, for example, one line has two color signals in two consecutively input scan lines, and the other line has a color signal. When there is no signal and when two lines are adapted by the comb filter 230, the color signal of the adjacent line is transferred to the high frequency luminance signal Y 'upon adaptation.

Meanwhile, the first detector 240 detects whether there is a color carrier in the high frequency signal 2221. That is, for the high frequency signal, the first detector 240 generates a logic high signal as the first sense signal 2401 for a horizontal scan line having a color carrier, and vice versa. 2401) to generate a logic low signal. The second detector 240 detects a color carrier at high frequency luminance Y ′ from the comb filter 230 while the two horizontal lines are adapted, and generates a logic high as the second detection signal 2501. Outputs the signal of.

Then, the control signal generator 281 generates a logic high signal as the control signal, and the switch 282 is connected to the second input input terminal S2 in response to the control signal of the logic high. The luminance signal 2701 from which the color signal inputted through the 3.58 MHz trap is removed is provided to the adder 290.

Therefore, according to the above configuration, when the luminance signal is separated from the composite video signal, it is possible to prevent the luminance signal from including the color signal component, thereby preventing the hanging dot phenomenon caused by the inflow of the color signal component into the luminance signal. Will be.

As described above, the present invention can realize a color and luminance signal separation circuit capable of separating a composite video signal into color and luminance signals without generating a hanging dot phenomenon.

Although the present invention has been described in detail by the above embodiments, the present invention is not limited thereto, and variations and improvements can be made without departing from the ordinary knowledge of those skilled in the art.

Claims (7)

Frequency separating means 220 for separating the continuously input composite video signal 2011 into a high frequency signal in which the low frequency luminance signal and the luminance and color signals are interleaved; Comb filter means 230 for adaptively filtering the high frequency signal from the frequency separating means 220 to separate the color and high frequency luminance signals; First sensing means (240) for detecting a color signal from the high frequency signal; Second sensing means (250) for detecting a color signal from the high frequency luminance signal; Signal removing means (270) for removing a color carrier from the high frequency luminance signal; And In response to the first and second sensing signals from the first and second sensing means 240 and 250, one of the signal from the signal removing means 270 and the high frequency luminance signal from the comb filter means is output. Color and luminance signal separation circuit, characterized in that it comprises a selection means (280) for selective output. 2. The color and luminance signal separation circuit according to claim 1, wherein the comb filter means is a line comb filter for adaptive filtering according to the correlation of the scan lines of the composite video signal. 2. The apparatus of claim 1, wherein the frequency dividing means (220) comprises: a low pass filter (221) for detecting a low frequency luminance signal from the composite video signal; And And a subtractor (222) for attenuating the low frequency luminance signal from the low pass filter (221) in the composite video signal. 4. The color and luminance signal separation circuit according to claim 3, wherein the low frequency luminance signal is a frequency signal of 3 MHz or less. 5. The apparatus according to any one of claims 2 to 4, further comprising adding means (290) for adding a low frequency luminance signal from said frequency separating means (220) and a high frequency luminance signal from said comb filter means (230). Color and luminance signal separation circuit, characterized in that configured to. 2. The color and luminance signal separation circuit of claim 1, wherein the first sensing unit detects a color carrier from the high frequency signal. 2. The second sensing means (250) of claim 1, wherein the second sensing means (250) phase of the high frequency luminance signal from the comb filter means (230) at a phase 180 degrees with respect to the phase of the color carrier carrier 1/2 times of the color carrier carrier period. First sampling means 253 for sampling every time; Second sampling means (255) for sampling a 3.58 MHz signal of the high frequency luminance signal from the comb filter means (230) every half time of the color carrier period in a 90 ° phase with respect to the phase of the color carrier; And Logic arithmetic means 252 for generating a second detection signal by performing a logic operation on the first sampling signal from the first sampling means 253 and the second sampling signal from the second sampling means 254. Color and luminance signal separation circuit, characterized in that the.