KR100296311B1 - The circuit for improving picture quality of ntsc mode standard image - Google Patents

Abstract

The present invention relates to an image quality improvement circuit of an NTS standard image. Conventionally, methods for improving sharpness by using various interpolation methods do not have a change in the original signal itself, and in some parts of the video, the image of the interpolation line is not included. There is a problem of blurry or jagged contours. Therefore, in the present invention, the analog / digital conversion unit 100 converts an analog NTSC standard video signal of an input signal into a digital video and outputs the digital video, and horizontally interpolates the digital video. A horizontal interpolation unit 200 that performs interpolation, a first image enhancement unit 300 which improves the clarity of the digital image interpolated by the horizontal interpolation unit using a pseudo filter, and the horizontal interpolation in the horizontal direction. And a vertical interpolation unit 400 interpolating in the vertical direction by using the directional correlation of 10 pixels around the interpolation pixel of the image having improved sharpness, and the sharpness of the digital image interpolated in the vertical direction from the vertical interpolation unit. The second image enhancing unit 500 and the digital image converting the analog image into the digital image having improved clarity are output to the analog image. It consists of a digital / analog converter 600 to improve the NTSC standard video resolution by 2 times in the horizontal and vertical directions, respectively, to have 4 times the resolution, and to perform directional interpolation on the boundary of the image existing in the original signal. It allows the boundaries of the image to be preserved and also improves the sharpness of the image quality for the image.

Description

Image quality improvement circuit and method of NTS standard video {THE CIRCUIT FOR IMPROVING PICTURE QUALITY OF NTSC MODE STANDARD IMAGE}

The present invention relates to an image quality improvement circuit and a method for improving NTSC standard image resolution in the horizontal direction and 2 times in the vertical direction to obtain high image quality, and in particular, an image existing in the original signal. The directional interpolation using directional interpolation that preserves the boundary of the interpolation, and after this scanning line interpolation, directional interpolation is performed not only for the original signal but also for the edge of the interpolation signal to improve the sharpness of the image quality. And to a method.

Conventional analog NTSC standard video uses interlaced scanning to reduce transmission bandwidth and image flicker.

If you scan 525 scan lines per frame from top to bottom, the image may flicker, so 525 scan lines are scanned in two times instead of one time to send one screen.

However, it takes 1/30 second time interval until the next scan line appears in the same place on the screen, so if you divide the scan twice, scan with the 262.5 scan line for the first 1/60 second, and for the next 1/60 second. Inject with the remaining 262.5 scan lines.

Therefore, a total of 525 scan lines forming one frame are drawn with a time difference.

Therefore, when interlaced NTSC is drawn on the screen, scanning is done by alternating 525 scan lines, which causes flickering between lines, which reduces the definition of the screen and reduces the clarity of image quality.

In order to compensate for the deterioration of image quality clarity of the interlaced scan method, a method of combining two field images using a memory and then drawing 525 scanning lines constituting a frame was proposed. The deviation occurred and the sharpness of the image quality was not improved.

Therefore, in order to solve such a problem, the unclear part is proposed in a method of using one field image from two field images, and the clear part using a combination of two field images.

In this case, since a high-definition video detection circuit is required, this becomes a problem in real time processing.

In addition, as a method for improving the sharpness of the image quality, a method of supplementing the skipped lines in the interlaced scanning method using scanning line interpolation has been proposed.

In this case, since 525 scanning lines are actually drawn in each field at once, the resolution is improved by 2 times in the vertical direction than the conventional NTSC signal, thereby improving the sharpness.

However, in the prior art as described above, methods for improving the clarity using various interpolation methods are not only a change in the original signal itself, but also blurry or jagged edges of the interpolation line in some parts of the video. There is a problem.

Therefore, an object of the present invention for solving the conventional problems as described above is to improve the image quality improvement circuit of the NC standard image to prevent the boundary line blur by interpolating by the directional interpolation method for the boundary line of the image existing in the original signal In providing.

Another object of the present invention is to provide an image quality improvement circuit of NTS standard image, which achieves four times the resolution doubled effect by improving the resolution of NTSC standard image by 2 times in the vertical direction and 2 times in the horizontal direction.

It is still another object of the present invention to provide an image quality improvement circuit of an NTS standard image for improving the sharpness of image quality by using a filter for sharpening edges for not only the original signal but also the interpolation signal after scanning line interpolation.

1 is a circuit diagram of an image quality improvement of an NTS standard image of the present invention.

FIG. 2 is a configuration diagram of a horizontal interpolation unit in FIG. 1. FIG.

3 is a configuration diagram of the first image enhancement unit in FIG. 1.

FIG. 4 is an explanatory diagram showing the calculation of the pseudo filter constituting the noise removing unit and the pixel group used for the calculation in FIG. 3; FIG.

FIG. 5 is an explanatory diagram showing an application example of a shoe filter in FIG. 4; FIG.

FIG. 6 is a configuration diagram of the noise removing unit in FIG. 4. FIG.

7 is a calculation block diagram of a Minmax filter and a Maxmin filter in FIG. 6;

FIG. 8 is an explanatory diagram showing a region classification process for determining an enhancement factor of FIG. 3 and a pixel group used in this process; FIG.

FIG. 9 is an explanatory diagram showing a pixel group used in the average weighted high pass filter in FIG. 3; FIG.

10 is an original image before and after applying the average weighted high pass filter of FIG. 9; FIG.

FIG. 11 is a configuration diagram of a vertical interpolation part in FIG. 1. FIG.

12 is a detailed view of a direction determining unit in FIG. 11;

FIG. 13 is a diagram illustrating a configuration of a second image enhancement unit in FIG. 1.

FIG. 14 is a configuration diagram of an area determination unit in FIG. 13.

15 is a diagram illustrating directional correlation for vertical interpolation in the present invention.

16 is a flowchart illustrating operation for vertical directional interpolation in the present invention.

FIG. 17 is an explanatory diagram showing a determination example of a dominant region and a non-dominant region in FIG. 16; FIG.

18 is a system configuration diagram showing an example of applying the present invention to a television (TV).

19 is a signal processing block diagram showing an example in which the present invention is applied to a color signal.

20 is an exemplary view showing the operation of the present invention NC standard image.

***** Explanation of symbols for main parts of drawing *****

100: analog / digital conversion unit 200: horizontal interpolation unit

300: first image enhancing unit 301: noise removing unit

302: region classification unit 303: improvement coefficient determination unit

304: Average weighted high pass filter 400: Vertical interpolator

405: direction determination unit 406: data selection unit

500: second image enhancement unit 501: state control unit

502: address generator 503-505: memory

506: multiplexer 600: digital / analog converter

801: Max filter 802: Min filter

803: Subtractor 804: Comparator

In order to achieve the above object, the present invention provides an analog / digital conversion unit for converting an analog NTSC standard video signal of an input signal into a digital video, and outputting a linear video, and a linear interpolation method for the digital video provided above. A horizontal interpolation unit for performing interpolation in the horizontal direction by using the first interpolation unit, a first image enhancement unit for improving the sharpness of the digital image interpolated in the horizontal interpolation unit using a shadow filter, and interpolation and A vertical interpolation unit for interpolating in the vertical direction by using the directional correlation of 10 pixels around the interpolation pixel of the image with improved sharpness, and a second image for improving the sharpness of the digital image interpolated in the vertical direction from the vertical interpolation unit An enhancement unit and the second image enhancement unit converts the digital image into an analog image Of force it characterized in that, including digital / analog converting units.

Hereinafter, with reference to the accompanying drawings in detail as follows.

1 is an image improvement circuit diagram of an NTS standard image of the present invention. As shown in the drawing, an analog (A) / digital (D) conversion unit converts an input analog NTSC standard video signal into a digital video and outputs the digital video. 100, a horizontal interpolation unit 200 which performs interpolation in a horizontal direction with a linear interpolation method on the digital image provided by the analog / digital converter 100, and the pseudo filter using the Interpolation and horizontal interpolation in the first image enhancement unit 300 and the horizontal interpolation unit 200 and the first image enhancement unit 300 to improve the sharpness of the digital image interpolated by the horizontal interpolation unit 200. The vertical interpolation unit 400 interpolates in the vertical direction by using the directional correlation of 10 pixels around the interpolation pixel of the image with improved sharpness, and the sharpness of the digital image interpolated in the vertical direction by the vertical interpolation unit 400. A second image enhancement unit 500 for improving the degree and a digital / analog converter 600 for converting the analog image into an analog image and outputting the digital image having improved clarity in the second image enhancement unit 500.

As illustrated in FIG. 3, the first image enhancement unit 300 includes a noise removing unit 301 for removing impulse noise present in the image, and an image from which noise is removed from the noise removing unit 301. An image classifier 302 for classifying a flat region or an edge region as a maximum value and a minimum value of an absolute error value between the image enhancement position center pixel and the surrounding eight pixels among the image enhancement position center pixels, and the image classified by the image classifier 302 The enhancement coefficient determiner 303 is configured to determine and output an enhancement factor of 1/1024 if the area of the flat area is a flat area, and an enhancement factor of 1/512, and an edge of the image from which the noise is removed by the noise removing unit 301. An average weighted high pass filter 304 extracting a high frequency component having a different extraction degree according to a brightness value, and an enhancement coefficient determined by the enhancement coefficient determiner 303 and an average weighted high pass band filter 304 Multiplied by high frequency components A multiplier 304 and an adder 305 for multiplying the value through the multiplier 304 to an image passed through the noise removing unit 301 to improve the sharpness of the image.

As illustrated in FIG. 11, the vertical interpolation unit 400 includes a first first-in first-out memory 401 that sequentially provides five pixel values of the first scan line to be input, and the second scan line to be input. A second first-in first-out memory 401 that sequentially provides five pixel values, and an error between pixels output from the first-in first-out first memory 401 and pixels output from the second first-in first-out memory 402 are obtained. The differential amplifier 403, the absolute value output unit 404 for obtaining the absolute value of the error obtained by the differential amplifier 403, and the two through the differential amplifier 403 and the absolute value output unit 404 A direction determining unit 405 for determining the direction of two pixels to be used when interpolating the absolute error between the pixels and outputting a data selection signal SEL according to the determined direction, and outputting the direction determining unit 405. The pixels in the direction selected by the data selection signal SEL The data selector 406, the adder 407 that adds the two pixels selected by the data selector 406, and the two pixel values added by the adder 407 by an average value divided by 1/2. The divider 408 is included.

12, the direction determiner 405 selects the smallest absolute error value between the two pixels of the first and second scan lines to be input, as shown in FIG. 12, and the min filter ( A comparator 702 for comparing the smallest value selected in step 701 with the same absolute error between the two pixels, or comparing the absolute errors between the two pixels and arbitrary values, and a comparison output from the comparator 702 A combination unit 703 for NAND values using five NAND gates, and a comparison signal output from the combination unit 703 and the comparator 702 through NAND gates to change the direction of the interpolation pixel. And a selection signal output unit 704 for outputting a selection signal for selection.

As shown in FIG. 13, the second image enhancement unit 500 controls the memory in synchronization with the input horizontal / vertical synchronization signal S_SYNC V_SYNC and the horizontal / vertical offset signal H_OFFSET V_OFFSET. A state controller 501 for generating a signal and signals for controlling operations of each unit, an address generator 502 for generating a predetermined address in a memory when a start signal Start_GEN is input from the state controller 501; The first to third memories may be configured to write data input by the read / write signal provided by the state controller 501 and the address generated by the address generator 502, or to read and output the written data. 503-505, a multiplexer 506 for selecting data from the first to third memories 503-505 by a control signal provided by the state controller 501, and a multiplexer 506 selected from the multiplexer 506. Data A 3x3 first-in first-out memory 507 for storing and outputting the data in the order of storage, and a differential amplification unit for obtaining an error between the center pixel S2 and the peripheral pixels S1-S9 provided by the memory 507 ( 508, an absolute value generator 509 for generating an absolute value of the error output from the above, an area determiner 5010 for determining whether the corresponding area is a flat area or an edge area by the absolute error generated above; And a selector and an adder 5017 which selects a pixel suitable for the region determined by the region determiner 5010 and outputs the image as it is or adds the result using the output value passed through the center pixel S2 and the average weighted high pass filter. .

As described above, the area determiner 5015 receives an absolute error between the center pixel S2 and the pixels S1 and S3-S9 around it and selects the largest value among them. 801, a min filter 802 that receives the absolute error and selects the smallest value among them, a subtractor 803 that subtracts the output of the min filter 802 from the output of the max filter 801, and And a comparator 804 comparing the output value of the subtractor 803 with the threshold value Th to determine whether the corresponding area is a flat area or an edge area.

Referring to the operation and effect of the present invention configured as described in detail as follows.

In the present invention, in order to improve the sharpness of the NTSC signal scanned by interlaced scanning, the directional correlation of 10 pixels around the interpolation pixel is first performed in two scan lines in which the resolution is doubled horizontally through horizontal interpolation and image enhancement. The interpolation pixel is found by using the relationship, and the interpolation pixel thus found is interpolated by directional interpolation to improve the resolution twice in the vertical direction.

In order to perform such a process, first, when an analog NTSC standard video signal is input to the analog / digital conversion unit 100 of FIG. 1, it is converted into a digital image and provided to the horizontal interpolation unit 200.

Then, the horizontal interpolation unit 200 has a scanning line enlarged twice in the horizontal direction by using a linear interpolation method.

That is, the horizontal interpolation unit 200 has the configuration as shown in FIG. 2, and when an image converted into digital is input, the horizontal interpolation unit 200 delays the original image by the delay unit 201 for a predetermined time and then adds the adder 202 to the adder 202. It is supplied to the multiplexer 204, respectively.

Here, the delay unit 201 uses a deflip-flop to obtain an average of two serially input pixels, and the clock frequency Clk uses 27 MHz.

Then, the adder 202 adds the original image and the delayed image delayed through the delay unit 201, and the divider 203 obtains an average value of the added image and supplies it to the multiplexer 204.

As a result, the multiplexer 204 receives the original image delayed by the delay unit 201 by a predetermined time and the average value of the two pixels through the adder 202 and the divider 203, that is, an interpolation value.

Then, the multiplexer 204 selects and outputs an interpolated image through the adder 202 and the divider 203 when the input clock Clk is '0', and when the clock Clk is '1'. The delayed unit 201 selects and outputs a delayed original image.

20, the scanning line is doubled in the horizontal direction as shown in (b) by linear interpolation in the horizontal direction with respect to the original scanning line as shown in (a).

In this way, when the horizontal interpolation unit 200 interpolates in the horizontal direction and outputs the horizontal image to the first image enhancement unit 300, the first image enhancement unit 300 improves the sharpness of the image quality. Let's look at with reference to FIG.

The noise removing unit 301 of the first image enhancement unit 300 removes the impulse noise existing in the image and impulse noise that may be caused by incorrect directional estimation when performing directional interpolation, which will be described later, by using a filter.

The reason for removing the impulse noise is because the impulse noise is a high frequency component, and if it is not removed, the noise component is extracted from the next high pass filter to emphasize the noise.

In addition, a pseudomedian filter capable of real-time implementation is used to remove the impulse noise.

The pseudo median filter is composed of a Minmax filter and a Maxmin filter, as shown in FIG.

First, as shown in FIG. 7A, the maxmin filter selects the minimum value through two min filters Min among the entered security, and then again has the maximum value having the largest value among the minimum values selected using the max filter Max. After selecting the final value, the Minmax filter selects the maximum value through the two Max filters Max among the input sequences as shown in FIG. 7B and then selects the maximum value again using the Min filter. The smallest value with the smallest value is selected and finally output.

Accordingly, the definitions of the maxmin filter MAXIMIN and the minmax filter for the _L sequences S ₁ , S ₂ , S ₃ , ..., S _L are as follows.

MAXIMIN {S ₁ , S ₂ , S ₃ , ..., S _L } = MAX (MIN (S ₁ , S ₂ ,., S _M ), MIN (S ₂ , S ₃ ,., S _{M + 1} )

, .., MIN (S _{L-M + 1} , S ₃ , ..., S _L )]

MINIMAX {S ₁ , S ₂ , S ₃ , ..., S _L } = MIN (MAX (S ₁ , S ₂ ,., S _M ), MAX (S ₂ , S ₃ ,., S _{M + 1} )

, .., MAX (S _{L-M + 1} , S ₃ , ..., S _L )]

Where M = (L + 1) / 2.

The Maxmin filter removes bright impulse noise, and the Minmax filter removes dark impulse noise.

Therefore, when there are five pixels as shown in FIG. 4, the noise removing unit 301 passes through the filters MAXIMIN (MINIMAX), dividers 301a, 301b, and adder 301c shown in FIG. 6. Filtering is performed to remove impulse noise.

The operation values undergoing the above process are as shown in FIG. 4, and an example of applying these values is as shown in FIG. 5.

After the impulse noise is removed from the noise removing unit 301 by using the pseudo median filter operating as described above, the noise classification unit 302 and the average weighted high pass band filter 304 are respectively provided.

Here, the average weighted high pass band filter 304 is used instead of the high pass filter (HPF), for the following reason.

In general, the high pass filter (HPF) extracts high frequency components regardless of the brightness of the region, and when it is added to the original image for image enhancement, the high frequency components added in the dark region cause deterioration in image quality. .

This is because human vision reacts sensitively to differences in brightness values in the darker areas than in the brighter areas, and the degradation of image quality is more likely to occur when many high frequency components are added to the darker areas.

Therefore, the present invention uses a mean-weighted high pass filter having a different extraction degree of high frequency components according to the ambient brightness value.

The average weighted high pass filter 304 extracts a high frequency component by performing the following operation using the pixel group shown in FIG.

y [m, n] = mean × {4 × S ₂ -S ₁ -S ₃ -S ₄ , S ₅ }

mean = (S ₁ + S ₃ + S ₄ + S ₅ ) / 4

As such, when the average weighted high pass filter 304 is applied to the original image illustrated in FIG. 10A, it may be confirmed that more high frequency components are extracted from the bright region as illustrated in FIG. 10B.

However, in the case of the edge region, when the high frequency component is added, the edge is emphasized and the sharpness is improved, but in the case of the flat region, the deterioration of image quality occurs even if a little high frequency component is added.

Since a high pass filter for extracting high frequency components from most images takes a second derivative, high frequency components are extracted even for small pixel values in a flat region.

Therefore, segmentation of the original image is required before the high frequency component is added to improve the image.

Therefore, a high frequency component is extracted using the average weighted high pass band filter 304 which varies the degree of extraction of the high frequency component in accordance with the ambient brightness value, and the extracted high frequency component is provided to the multiplier 305.

In this case, the area classifier 302 may determine an absolute error value between the image enhancement position center pixel S2 shown in FIG. 8 and the surrounding eight pixels S1 and S3-S9 among the images input from the noise removing unit 301. Zone classification is performed using the maximum and minimum values of.

That is, the maximum value of the absolute error value ( ) And the minimum value of the absolute error value ( If the difference is smaller than the random value Th, it is classified as a flat area, and if it is larger than the random value, it is classified as an edge area.

: Flat area

Edge area

The area classifier 302 classifies whether the input image is a flat area or an edge area and provides the result to the improvement coefficient determiner 303.

Then, the improvement coefficient determiner 303 outputs the improvement coefficient 1/1034 to the multiplier 305 if the area classified by the area classification unit 302 is a flat area, and the improvement coefficient 1/512 to the edge area.

Accordingly, the multiplier 305 multiplies the improvement coefficient determined by the enhancement coefficient determiner 303 with the high frequency component extracted through the average weighted high pass filter 304 and outputs the multiplier 306 to the adder 306.

Therefore, the adder 306 improves an image by adding a high frequency component obtained through the multiplier 305 to an image from which the impulse noise is removed by the noise remover 301.

The interpolation pixel is interpolated in the vertical direction using the directional correlation of 10 pixels around the interpolation pixel by using two scanning lines whose horizontal resolution is doubled in the horizontal direction through horizontal interpolation and image enhancement.

That is, as shown in FIG. 15, the interpolation pixel position (k, n) obtains a correlation between pixels in five a, b, c, d, and e directions, finds the pixel having the largest correlation, and averages the two pixels. Interpolate

Here, k-1 and k + 1 denote scan lines whose resolutions are enlarged twice in the horizontal direction, and k denotes newly generated vertical interpolation scan lines.

The correlation between pixels is obtained by using an absolute error between two pixels in five directions, and the smaller the absolute error value obtained, the greater the correlation.

Referring to FIG. 11, a pixel of a newly generated k-1 scan line is input to the first-in first-out memory 401 of an image obtained through horizontal interpolation and image enhancement, and a pixel of a k + 1 scan line is input. When input to the first-in-first-out memory 402, the first-in first-out memory 401 sequentially outputs the input pixels through the output terminals ①-⑤ thereof, and the second first-in first-out memory 402. Similarly, the input pixels are sequentially output through their output terminals ⓐ-ⓔ in the order of input.

The differential amplifier 403 receives the difference between the pixel of the k-1 scan line and the pixel of the k + 1 scan line and outputs the error to the absolute value generator 404.

The absolute value generator 404 then outputs the absolute value of the error transmitted from the differential amplifier 403 to the direction determiner 405.

Accordingly, the direction determiner 405 determines the direction using the absolute value provided by the absolute value generator 404, and provides the determined direction select signal SEL to the data selector 406.

Accordingly, the data selector 406 may output two out of ten pixels output from the first and second first-in, first-out memory 401 and 402 input according to the direction selection signal SEL determined by the direction determiner 405. Select the pixel to determine the interpolation value.

The two pixels selected by the data selector 406 are added by the adder 407, and the interpolation value obtained by performing vertical interpolation or directional interpolation divided by the divider 408 in half is output.

At this time, the output from the direction determiner 405 is output as 5 bits, as shown in Figure 12, only one of the output 5 bits to '1' to select one of the five directions.

In addition, there are cases where all 5 bits of the output become '0', which corresponds to the case of c <Th in FIG. 16.

12, the absolute value generated by the absolute value generator 404 of FIG. 11 (│①-ⓐ│, │②-ⓑ│, │③-ⓒ│). , ④-ⓓ│, │⑤-ⓔ│) are accepted by the min filter 701 and the smallest value among the absolute error values is selected and output to the comparator 702.

At this time, the comparison unit 702 inputs values such as │②-ⓑ│ + 30, │④-ⓓ│ + 30, │⑤-ⓔ│ + 30, and the threshold value Th.

Then, the comparing unit 702 uses a plurality of comparators, and the absolute error value is the same as the most absolute error value selected through the min filter 701, and the absolute error value is larger than the threshold value and the absolute error value. The cases where the value is smaller than the threshold value are found and output to the first combination unit 703.

Accordingly, the first combination unit 703 nands the output value output from the comparator of the comparator 702 and outputs the output value to the second combination unit 704.

Accordingly, the second combiner 704 nds the signal output from the first combiner 703 and the signal output from some comparators of the comparator 702 to output a 5-bit output signal of FIG. 11. Output to selector 406.

Here, the 5-bit output signal corresponds to the direction selection signal SEL.

The data selector 406 then performs the operation shown in FIG. 16 to perform linear interpolation or directional interpolation in the vertical direction.

That is, ten pixels (①②③④⑤, ⓐⓑⓒⓓⓔ) from the first and second first-in first-out memories 401 and 402 from the two scan lines k-1 and k + 1 shown in FIG. If is input, the correlation between pixels is obtained in five directions such as a, b, c, d, and e (S101).

Here, the correlation between the pixels is to obtain the absolute error between the two pixels in five directions (a, b, c, d, e), the smaller the value of the absolute error value obtained, the greater the correlation.

In step S101, the correlation between the pixels is calculated, and the value of the direction c is compared with the threshold value Th (S102).

As a result of the comparison, if the value of the direction c is smaller than the threshold (Th) value, it is determined to be a flat area and interpolated by linear interpolation in the vertical direction (S103). If the value of c is larger than the threshold value (Th), Judging by the edge area.

If it is determined as the edge region, it is again determined whether the edge region is a dominant edge region or a non-dominant region (S104).

As a result of the determination, interpolation is performed by the directional interpolation method in the dominant region (S106), and linear interpolation is performed in the vertical direction in the non-dominant region (S105).

Herein, a process of determining the dominant region and the non-dominant region among the edge regions will be described with reference to FIG. 18.

If the absolute error value in the directions a and d is larger than the threshold value, and the absolute error value in the directions a and e is larger than the threshold value, the dominant region is determined. Otherwise, the non-dominant region is determined. .

That is, if (│a-d│> Th, │a-e│> Th) dominant edge area

else non-dominant edge region

In the above, directional interpolation is an average interpolation between two pixels having the largest correlation between pixels.

After the interpolation is performed by line interpolation and directional interpolation in the vertical direction, the interpolation is input to the first to third memories 503 to 505 of the second image enhancement unit 500 of FIG. 1.

At this time, the state control unit 501 is a horizontal and vertical synchronization signal (H_SYNC, V_SYNC) and a horizontal offset signal (H_OFFSET: the number of clocks until the actual data appears after the horizontal synchronization signal input), the vertical offset signal (V_OFFSET: vertical synchronization signal input) After receiving the number of lines until the actual data appears from the microcomputer not shown, the start signal (Start_GEN) is output to the address generator 502.

Then, the address generator 502 increases the address one by one every clock from the time when the start signal Start_GEN is input, and generates the address to the first to third memories 503 to 505. The address will change from 0 to 719.

Meanwhile, the state controller 501 outputs a bypass signal BYPASS for the first and second lines by using the horizontal sync signal H_SYNC and the vertical sync signal V_SYNC. Try bypassing it without making any improvements.

The read / write signal R / W, which is another output of the state controller 501, controls read / write of the first to third memories 503-505, and sends read signals to the two memories. The other one sends a write signal.

The read signal and the write signal are output while rotating.

Accordingly, two of the outputs of the first to third memories 503-505 and one of the current data inputs are input to the multiplexer 506.

Then, the multiplexer 506 selects one from the selection signal output from the state controller 501 and outputs the one to the 3x3 first-in, first-out memory 506.

As a result, the output of the multiplexer 506 includes two pixels at the same position in the current input pixel and the two previous lines.

This pixel is input to the 3x3 first-in, first-out memory 507, and is made up of pixel values up to S1-S9 necessary for image enhancement. The pixels up to S1-S9 are as shown in FIG.

When the pixel created in the 3x3 first-in-first-out memory 507 is input to the differential amplifier 508, the differential amplifier 508 obtains an error between the pixels S1 and S3-S9 different from the center pixel S2. Output to the value generator 509.

The absolute value generator 509 then provides the absolute error value to the area determiner 5010.

Accordingly, the region determiner 5010 determines whether the input image is an edge region or a flat region by using the input absolute error value and outputs the image to the selection and adder 5017.

In this case, the adder 5011 adds pixel values of S1, S3, S5, and S8 to the subtractor 5013, and the multiplier 5012 multiplies the center pixel S2 by 4 to output to the subtractor 5013.

Therefore, when the subtractor 5013 subtracts the output value of the multiplier 5012 from the output of the adder 5011 and then provides the multiplier 5014 to the multiplier 5014, the multiplier 5014 of the subtractor 5013 and the adder 5011. The output value is multiplied and output to the improvement coefficient multiplier 5015.

The value passed through the multiplier 5014 in the adder 5011 is a value obtained by extracting a high pass component through an average weighted high pass band pass filter. This has already been described with reference to FIG. 9.

The improvement coefficient multiplier 5015 multiplies the output of the multiplier 5014 by an improvement coefficient 1/2048 to provide the terminal E1 and the divider 5016 of the selector and adder 5017, respectively.

The divider 5016 then provides a value obtained by dividing the output of the enhancement coefficient multiplier 5015 by half to the E2 terminal of the selector and adder 5017.

Then, when the selection and adder 5017 determines the current image as the edge region in the area determiner 5010, the selector and adder 5017 adds the value inputted to the terminal E1 to the center pixel S2 to output the enhanced pixel S2 + E1, and displays the current image. If it is determined as the flat region, the pixel S2 + E2 is output by adding the value inputted to the terminal E2 to the center pixel S2.

This process improves the image.

The area determiner 5010 is as shown in FIG. 14, and its operation is absolute with the central pixel S2 and the other pixels S1 and S3-S9 in the Max filter 801 and the Min filter 802, respectively. When the error value is received and the largest value and the smallest value are selected and provided to the subtractor 803, the subtractor 803 calculates a threshold value in the comparator 804 by subtracting the smallest value from the largest value among the absolute error values. Compared with the value Th, if it is smaller than the threshold value Th, it is determined as a flat area, and if it is larger, it is determined as an edge area.

When the interpolation is performed using linear interpolation and directional interpolation in the vertical direction, and the image is further improved and provided to the digital / analog converter 600 of FIG. 1, the digital / analog converter 600 is an analog video signal. Convert and finally output.

Looking at the entire operation described so far based on Figure 20, when the same circular scanning line as in (a) is interpolated in the horizontal direction by the linear interpolation unit 200 in the horizontal direction with respect to the same image as in (b) Likewise, pixels increase in the horizontal direction.

The resolution of the image is increased with respect to the increased pixel as in (c) of the first image enhancement unit 300. After that, if the image belongs to the flat region in the vertical interpolation unit 400, linear interpolation in the vertical direction is performed. If the image belongs to the edge region, interpolation is performed using directional interpolation to increase the resolution in the vertical direction as shown in (d).

After that, the image is improved again, and as shown in (e), the image with improved image sharpness is output.

An example in which the present invention described above is applied to a TV system as shown in FIG. 18 is illustrated.

When the tuner 1 receives the standard NTSC signal and provides the composite video signal detected through the IF and detector stages 2 to the luminance / color signal separator 3, the luminance signal Y is passed through the separator 3. ) And the color signal (C).

The luminance signal Y and the color signal C are converted into the digital luminance signal Y and the color signal C by the analog / digital converter 5 and then provided to the image quality improvement circuit 6 of the present invention.

In this case, 13.5 MHz is used as the sampling clock provided to the analog / digital converter 5.

The luminance signal separated by the luminance / color signal separation unit 3 is input to the synchronization separation unit 4, and is separated into a horizontal synchronization signal H_SYNC and a vertical synchronization signal V_SYNC, so that the image quality improvement circuit 6 Used as a reference sync signal.

On the other hand, the horizontal offset signal H_OFFSET and the vertical offset signal V_OFFSET are input to the image quality improvement circuit 6 of the present invention as a means for knowing the effective data area of the present invention from the microcomputer 10.

The image quality improving circuit 6 of the present invention uses 13.5 MHz, 27 MHz, and 54 MHz as clocks for interpolation and image enhancement, where 27 MHz is used for horizontally interpolated signals and 54 MHz is used for horizontally and vertically interpolated signals.

The output of the image quality improvement circuit 6 is a signal having four times the resolution of the input.

The digital / analog converter 7 converts the luminance signal Y and the color signal C into analog Y / U / V signals and provides the matrix 8 with the matrix 8 converted into an RGB signal. Final output through the CRT (9).

19 shows an example in which the present invention is applied to a color signal. The color signal C input from the DEMUX is generated as CR and CB signals, and the signal is interpolated and improved through the image quality improvement circuit of the present invention. When the signal is supplied to the mux again, the mux outputs the interpolated enhanced color signal C.

In the process of demuxing the color signal C, a delay of one clock is generated, and the luminance signal Y is also delayed to match the timing.

As described in detail above, the present invention improves the resolution of an NTSC standard image by 2 times in the horizontal and vertical directions, respectively, to have 4 times the resolution, and performs directional interpolation on the boundary line of the image existing in the original signal. In addition to preserving the edges, there is an effect of improving the sharpness of the image quality for the image.

Claims (10)

Analog-to-digital converter that converts the input analog NTSC standard video signal into digital video and outputs it, and horizontal interpolation that performs interpolation in the horizontal direction by using linear interpolation on the digital video provided above. A first image enhancement unit for improving the sharpness of the digital image interpolated in the horizontal interpolation unit by using an executive unit and a shadow filter, and 10 pixels around the interpolation pixel of the image having the improved interpolation and sharpness in the horizontal direction. A vertical interpolation unit for interpolating in the vertical direction using directional correlation, a second image enhancement unit for improving the sharpness of the digital image interpolated in the vertical direction from the vertical interpolation unit, and a sharpness in the second image enhancement unit Includes a digital / analog converter that converts and outputs an analog image into an enhanced digital image. Characteristic improvement circuit of NTS standard image. The image display apparatus of claim 1, wherein the first image enhancement unit removes an impulse noise present in the image, and an absolute error between the image enhancement position center pixel and the surrounding eight pixels in the image from which the noise is removed. An image classification unit for classifying a flat area or an edge area with a maximum value and a minimum value, and an improvement coefficient for determining an improvement coefficient corresponding to an area of an image classified by the image classification unit, and outputting the determined improvement coefficient. And an average weighted high pass filter for extracting a high frequency component having a different extraction degree according to an ambient brightness value of the image from which the noise is removed by the noise removing unit, and an improvement coefficient determined by the enhancement coefficient determining unit and the average weighted high range. A multiplier multiplying the high frequency components extracted by the band pass filter, and multiplying the value by the multiplier to the image passed through the noise removing unit And an adder for improving the sharpness of the image. The image quality improvement circuit of claim 2, wherein the noise removing unit uses a pseudo median filter. The standard image image of claim 2, wherein the enhancement coefficient determiner determines that the enhancement coefficient is 1/1024 when the input image is a flat region, and the enhancement coefficient is 1/512 when the edge is an edge region. Image quality improvement circuit. 3. The image classification unit of claim 2, wherein the image classification unit comprises: a first process of obtaining an absolute error of the center pixel and the surrounding pixels; a second process of obtaining the maximum and minimum values of the absolute error obtained above; and a maximum value of the absolute error obtained above; A third step of obtaining the difference between the minimum value and a fourth step of classifying the area into a flat area if the difference between the maximum value and the minimum value is smaller than the random value Th, and classifying the edge area if the difference between the maximum value and the minimum value is larger than the random value Th. Characteristic improvement circuit of NTS standard image. 2. The first interpolation unit of claim 1, wherein the vertical interpolation unit sequentially inputs a first-in first-out memory that sequentially provides five pixel values of the first scan line to be input, and a second first-in first that sequentially provides five pixel values of the second scan line to be input. A differential amplifier which calculates an error between a first memory, a pixel output from the first-in-first-out memory and a pixel output from the second first-in-first-out memory, and an absolute value output unit that obtains an absolute value from the error obtained by the differential amplifier. A direction determining unit which determines a direction of two pixels to be used when interpolating the absolute error between the two pixels passing through the differential amplifier and the absolute value output unit, and outputs a data selection signal according to the determined direction; A data selection unit for selecting and outputting pixels in a direction selected by the data selection signal output from the determination unit, and two selected by the data selection unit And an adder for adding pixels, and a divider for interpolating the two pixel values added by the adder by an average value divided by 1/2. The method of claim 6, wherein the direction determiner is a min filter for selecting the smallest value among the absolute errors between the two pixels of the first and second scan line input, the smallest value selected from the min filter and the absolute error between the two pixels A comparator for comparing the same value or comparing the absolute errors and arbitrary values between the two pixels, and a combination unit for NAND-ringing the comparison values output from the comparator using five NAND gates, the combination unit and the comparator And a selection signal output unit configured to output a selection signal for selecting a direction of an interpolation pixel by NANDring the comparison signals output from the NAND gates through five NAND gates. 7. The data selector of claim 6, wherein the data selector selects and outputs data from two scan lines input to interpolate by linear interpolation if the area of the pixel to be interpolated is a flat area, and if the area is an edge area, the dominant again. A second process of classifying the dominant edge region and the non-dominant region, and interpolation by directional interpolation in the vertical direction in the case of the dominant region, and linear interpolation in the vertical direction in the non-dominant region. And a third process of selecting and outputting the input data so as to output the image quality. The display apparatus of claim 1, wherein the second image enhancement unit comprises: a state controller configured to generate a memory control signal and signals for controlling operations of each unit in synchronization with a horizontal / vertical synchronization signal and a horizontal / vertical offset signal; Writes or reads the data inputted by the address generator which generates a predetermined address in the memory upon input of the start signal, the read / write signal provided by the state controller, and the address generated by the address generator. A first to third memory for inputting and outputting a data, a multiplexer for selecting data from the first to third memory by a control signal provided by the state controller, and data selected from the multiplexer A 3x3 first-in first-out memory for outputting, the center pixel provided by the memory, and its A differential amplifier which calculates an error between the eight pixels of the side, an absolute value generator that generates an absolute value of the error outputted above, and an absolute error generated above to determine whether the corresponding area is a flat area or an edge area And a selector and an adder which selects a pixel corresponding to the region determined by the region determiner and outputs the same as it is or adds the output using the region determiner and the output value passed through the center pixel and the average weighted high pass filter. SCC standard image quality improvement circuit. 10. The method of claim 9, wherein the area determiner is a Max filter that receives the absolute error of the center pixel and the eight pixels around the pixel and selects the largest value therein, and a Min filter that receives the absolute error and selects the smallest value thereof. And a subtractor for subtracting the output of the min filter from the output of the max filter, and a comparator comparing the output value of the subtractor with a threshold value and determining whether the corresponding area is a flat area or an edge area. Image quality improvement circuit of MR standard video.