KR20090078895A - Equipment and method for de-interlacing - Google Patents

Abstract

A deinterlacing apparatus and a method thereof are provide to mitigate increase of operation quantity relatively when improving image quality of a deinterlacing image. By using plural first pixels and plural second pixels, a direction of an edge is detected(S200). The plural first pixels are included in a first upper scan line and a first lower scan line for an interpolation target pixel of an interlacing scan signal. The plural second pixels are included in a second upper scan line and a second lower scan line. If the edge direction is determined as a first diagonal direction or a second diagonal direction, interpolation is performed by reflecting each weight to a linear interpolation value of a pixel of the edge direction and a linear interpolation value of a pixel of a vertical direction(S220).

Description

Equipment and Method for De-interlacing

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to de-interlacing of video signals, and more particularly, to a deinterlacing apparatus and method for converting a signal of a progressive scan type into a signal of a sequential scan type.

Interlacing is the division of an entire frame into two parts called fields. One of the two fields is an image composed of even-numbered horizontal lines, and the other is an image composed of odd-numbered horizontal lines. In broadcast or storage devices, such field images are used to encode, transmit, and / or reproduce in a widely accompaniment scanning format, which has an advantage of efficiently using a limited bandwidth without significant deterioration in image quality. For example, such a conventional scanning format has been widely used in broadcast standards such as the National Television System Commitee (NTSC), Phase Alternation Line (PAL), and Secam (SECAM).

Conventional scanning methods for displaying field images have shown satisfactory effects in human visual systems, but with the advent of HDTV, interlacing defects have started to appear due to the increase in screen size of flat panel display devices. An interlacing defect is a phenomenon in which image quality deteriorates, for example, a line crawl phenomenon, a serration of tooth shape, and an inter-line flicker. Therefore, the recent HDTV system supports a sequential scanning method to provide an image of improved quality using a flat screen display device having a large screen size.

De-interlacing is a technique of converting a scan format so that an image of a progressive scan format can be converted into an image of a sequential scan format and output. This deinterlacing is important in how exactly the predicted or interpolated pixel values for the empty lines of the field image match the pixel values of the actual image. In the deinterlacing, it is necessary to accurately restore the pixel value of the original frame image and maintain edge sharpness or the like. In particular, since low-pass filtering and decimated video signals have lower resolution than the original video, it is particularly important to reconstruct the original video including edge sharpness more accurately and precisely by deinterlacing. Do.

De-interlacing can be broadly classified into intra-field interpolation and inter-field interpolation. Intra-field interpolation method is to interpolate using only information in the field based on spatial correlation, and inter-field interpolation method is to interpolate using information between front and rear fields as well as information in the field based on spatial correlation and temporal correlation. In general, the performance of the inter-field interpolation method is known to be more excellent, but there is a disadvantage that the structure is complicated and expensive because additional field memory is required to use the front and rear field information. On the other hand, in-field interpolation method has lower interpolation performance than inter-field interpolation method, but its advantages are simple implementation and low cost.

Among the interpolation methods in the field, the edge based line average (ELA) technique is effective as the intrafield interpolation method because it can effectively remove the step phenomenon occurring at the edge of the image by interpolating using the edge information of the image. However, in the ELA method, a portion including a vertical edge, a portion where a brightness difference of a pixel is not clear, and a portion including a high frequency component of an image may not detect an actual edge but may detect an incorrect direction. In this case, the image quality is deteriorated because it causes a noticeable high frequency component error.

In this regard, the E-ELA technique is proposed, in which the trend of the edge is first identified and then deinterlaced by applying the ELA technique according to the trend of the edge. However, the E-ELA (Enhanced ELA) method determines the direction in which the difference between the two pixel values centered on the interpolation target pixel is the smallest as the direction of the edge. One had a limit.

In addition, the direction-oriented interpolation (DOI) technique is a method of deinterlacing by determining edges of various angles such as 90 °, ± 45 °, ± 26.6 °, and ± 18.4 °. This uses a concept of the direction vector to consider the various directions, which has a considerable complexity, which makes it difficult to apply in real time.

The problem to be solved by the present invention is to provide a de-interlacing apparatus and method that can obtain a better image quality.

Another object of the present invention is to provide a deinterlacing apparatus and method that can relatively alleviate an increase in the amount of computation in improving the image quality of a deinterlacing image.

Deinterlacing method or apparatus according to an embodiment of the present invention for solving the above problems is a plurality of first pixels and first to be included in the first upper scan line and the first lower scan line for the interpolation target pixel of the parallel scan signal Determining an edge direction by using a plurality of second pixels included in the second upper scan line and the second lower scan line; And a linear interpolation value of a pixel in a direction perpendicular to the interpolation target pixel among the plurality of first pixels and the plurality of second pixels when the direction of the edge is determined as the first diagonal direction or the second diagonal direction. And interpolating or interpolating using a linear interpolation value of a pixel in the direction of the edge of the plurality of first pixels and the plurality of second pixels.

According to this problem solving means, the direction of the edge is determined using not only two pixels adjacent to the interpolation target pixel but also pixels of the scan line located above and below it. If the edge direction is vertical, interpolation is performed using the pixel value in the vertical direction. However, if the edge direction is diagonal, the pixel value in the vertical direction and the pixel value in the diagonal direction are considered in consideration of the local pattern. Perform interpolation using all of them. Therefore, according to the present invention, the direction of the edge can be more accurately determined, and the influence on the interpolation target pixel can be reflected according to the distance between the neighboring pixels and the local pattern, so that the image quality can be significantly improved. . In addition, according to the present invention, it is possible to relatively alleviate an increase in the amount of computation in improving the image quality of the deinterlaced image.

Hereinafter, with reference to the accompanying drawings will be described in detail an embodiment of the present invention. Since the embodiments described below are for the purpose of illustrating the technical idea of the present invention, the technical idea of the present invention should not be construed as being limited by the embodiments. Reference numerals added to the respective components in the description of the embodiment and the drawings are merely described for convenience of description.

1 is a block diagram showing a configuration of a deinterlacing apparatus according to an embodiment of the present invention, FIG. 2 shows a window centering on an interpolation target pixel, and FIG. 5 shows a deinterlacing method according to an embodiment of the present invention. It is a flowchart.

Referring to FIG. 1, the deinterlacing apparatus 100 includes an edge direction detector 110 and an interpolating unit 120.

The edge direction determiner 110 is included in the plurality of first pixels, the second upper scan line, and the second lower scan line included in the first upper scan line and the first lower scan line for the interpolation target pixel of the parallel scan signal. The direction of the edge is determined using the plurality of second pixels.

Here, as shown in FIG. 2, the first upper scan line is a scan line positioned above the interpolation target pixel, the first lower scan line is a scan line positioned below the interpolation target pixel, and the second upper scan line Is a scan line located above the first upper scan line, and the second lower scan line is a scan line located below the first lower scan line.

Meanwhile, the plurality of first pixels are located in the first upper scan line and positioned upwardly with respect to the interpolation target pixel (hereinafter, referred to as “u”), and pixels positioned up and left with respect to the interpolation target pixel. (Hereinafter referred to as ul) and a pixel positioned up and right with respect to the interpolation target pixel (hereinafter referred to as ur), and a pixel located within the first lower scan line and positioned below the interpolation target pixel ( Hereinafter referred to as d), a pixel positioned down and right with respect to the interpolation target pixel (hereinafter, referred to as dr) and a pixel positioned below and left with respect to the interpolation target pixel (hereinafter referred to as dl). It is included).

In addition, the plurality of second pixels may be located in the second upper scan line and positioned upwardly with respect to the u (hereinafter, referred to as U), and pixels positioned up and left with respect to the ul (hereinafter, referred to as UL). And pixels located up and right with respect to ur (hereinafter referred to as UR) and pixels located within the second lower scan line and located downward with respect to d (hereinafter, referred to as D). Pixels located down and right with respect to dr (hereinafter, referred to as DR) and pixels located down and left with respect to dl (hereinafter, referred to as DL) are included.

As can be seen in FIG. 2, the edges can have a vertical direction, a first diagonal direction, and a second diagonal direction. Here, the vertical direction is a direction including pixels of U, u, d, and D, the first diagonal direction is a direction including pixels of UL, ul, dr, and DR, and the second diagonal direction is UR, ur, dl And a pixel of the DL.

According to an embodiment of the present invention, the direction of the edge is i) a plurality of pixels U, u, d, and V, which are perpendicular to the interpolation target pixel X of the plurality of first pixels and the plurality of second pixels. Dispersion of pixel values of D), ii) dispersion of pixel values of pixels UL, ul, dr, and DR in the first diagonal direction of the plurality of first pixels and the plurality of second pixels; The direction of having the smallest value among the variances of pixel values of the pixels UR, ur, dl and DL in the second diagonal direction among the plurality of first pixels and the plurality of second pixels (s200 in FIG. 5). .

Unlike the conventional method of determining the direction of an edge using two pixels centered on the interpolation target pixel, in the present invention, the direction of the edge is determined using four or more pixels that may affect the interpolation target pixel. The direction of the edge can be determined more accurately.

Next, the information on the direction of the edge determined by the edge direction determination unit 110 is sent to the interpolator 120.

According to an embodiment of the present invention, when the direction of the edge is determined as the first diagonal direction or the second diagonal direction, the interpolation target pixel X of the plurality of first pixels and the plurality of second pixels may be used. Linear interpolation values of pixels U, u, d, and D in the vertical direction and pixels UL, ul, dr, and DR or UR in the direction of the edge of the plurality of first pixels and the plurality of second pixels. , ur, dl, and DL) are interpolated using the linear interpolation values (s210 of FIG. 5). Specifically, interpolation is performed by reflecting respective weights on the linear interpolation value of the pixel in the vertical direction and the linear interpolation value of the pixel in the direction of the edge. More specifically, the weight is determined using the ratio of the distance from the interpolation target pixel X to the pixel in the vertical direction and the distance from the interpolation target pixel to the pixel in the edge direction.

This takes into account the fact that the influence on the interpolation target pixel X varies depending on the position of the pixel. That is, even when the direction of the edge is diagonal, the interpolation target pixel X is more closely affected by the pixels in the vertical direction since the interpolation target pixel X is closer in distance to the pixels in the vertical direction.

According to an embodiment of the present invention, when the direction of the edge is determined as the first diagonal direction or the second diagonal direction, the linear interpolation value of the pixel in the vertical direction and the linear interpolation value of the pixel in the direction of the edge are determined. The sum of the values multiplied by the respective weights is interpolated by the sum of the respective weights.

배만큼 더욱 가까운 사실을 고려한 것이다. According to an embodiment of the present invention, when the direction of the edge is determined as the first diagonal direction or the second diagonal direction, the weight of the linear interpolation value of the pixel in the vertical direction and the linearity of the pixel in the direction of the edge are determined. The ratio of weights to interpolation values is 1: 1 to 2: 1. This means that the pixels in the vertical direction are interpolated relative to the pixels in the diagonal direction.

Considering the fact that the ship is closer.

According to an embodiment of the present invention, when the direction of the edge is the vertical direction, the interpolation unit 120 adjusts pixel values of the pixels U, u, d, and D in the vertical direction with respect to the interpolation target pixel X. Linear interpolation using (s220 of FIG. 5)

3 is a graph illustrating the principle of linear interpolation considering a local pattern of pixels according to an embodiment of the present invention. Point A of FIG. 3 shows a value obtained based on a conventional bi-linear interpolation method. In the conventional bilinear interpolation method, since only the left and right pixel values f ₂ and f _{3 that} are closest to the interpolated pixel are not considered, the image is blurred due to inaccurate interpolation.

The linear interpolation method according to an embodiment of the present invention considers not only f ₂ and f ₃ but also pixel values of f ₁ and f ₄ . As shown in FIG. 3, temp ₁ is defined in consideration of patterns formed by f ₁ and f ₂ , temp ₂ is defined in consideration of patterns formed by f ₃ and f ₄ , and temp ₁ and temp ₂ are used. More accurate interpolation values can be obtained.

Equation 1 below is a specific equation for linear interpolation according to an embodiment of the present invention.

,

,

Here, s is a distance from the interpolation target pixel to a pixel ul, u, ur, dl, d or dr adjacent to the interpolation target pixel among the plurality of first pixels, and (1-s) is the interpolation target pixel. Is a distance from another pixel (ul, u, ur, dl, d, or dr) symmetric to the adjacent pixel, f ₁ , f ₂ , f _3, and f ₄ are ⅰ) the plurality of first pixels and the plurality of pixels Pixel values of the pixels U, u, d, and D in the direction perpendicular to the interpolation target pixel among the second pixels of ii) in a first diagonal direction of the plurality of first pixels and the plurality of second pixels; Pixel values of the pixels UL, ul, dr, and DR, or i) Pixel values of the pixels UR, ur, dl, and DL in a second diagonal direction among the plurality of first pixels and the plurality of second pixels. Are shown in order. Further, the slope of the pattern formed by f ₁ and f ₂ is (f ₂ -f ₁ ) / 1, and the slope of the pattern formed by f ₃ and f ₄ is (f ₄ -f ₃ ) / 1.

Table 1 below shows the objective image quality as a Peak Signal to Noise Ratio (PSNR) by performing experimental results on various still images having a size of 512 × 512. As shown in Table 1, it can be seen that the method according to an embodiment of the present invention can obtain better image quality than the conventional ELA, E-ELA, and DOI techniques for various still images.

ELA E-ELA DOI The present invention lena 35.97 36.89 37.09 38.28 barbara 25.17 30.61 31.56 32.85 boats 32.67 33.43 34.76 35.60 finger 28.91 29.40 29.54 32.58

4 is a photograph showing a result of deinterlacing an image according to an embodiment of the present invention. As can be seen in Figure 4, when de-interlacing according to an embodiment of the present invention it can be seen that the image quality is significantly improved compared to the existing methods ELA, E-ELA, and DOI.

1 is a block diagram showing a configuration of a deinterlacing apparatus according to an embodiment of the present invention;

2 is a window centering on an interpolation target pixel X;

3 is a graph illustrating a principle of interpolation method considering a local pattern of pixels according to an embodiment of the present invention;

4 is a photograph showing a result of deinterlacing an image according to an embodiment of the present invention;

5 is a flowchart illustrating a deinterlacing method according to an embodiment of the present invention.

Claims (16)

A plurality of first pixels included in the first upper scan line and the first lower scan line for the interpolation target pixel of the parallel scan signal, and a plurality of second pixels included in the second upper scan line and the second lower scan line are used. Determining the direction of the edges; And In the case where the direction of the edge is determined in the first diagonal direction or the second diagonal direction, the linear interpolation value of the pixel which is perpendicular to the interpolation target pixel among the plurality of first pixels and the plurality of second pixels and Interpolating using a linear interpolation value of a pixel in the direction of the edge of the plurality of first pixels and the plurality of second pixels. The method of claim 1, The determining of the edge direction may include: i) dispersion of pixel values of pixels in a direction perpendicular to the interpolation target pixel among the plurality of first pixels and the plurality of second pixels, ii) the plurality of first pixels and the plurality of pixels. Variance of pixel values of the pixels in the first diagonal direction among the second pixels of V, and iii) the smallest value of the dispersion of pixel values of the pixels in the second diagonal direction among the plurality of first pixels and the plurality of second pixels Deinterlacing method characterized in that it determines the direction having the direction of the edge. The method of claim 1, And the interpolation step interpolates the linear interpolation values of the pixels in the vertical direction and the linear interpolation values of the pixels in the edge direction. The method of claim 3, And the weight is determined using a ratio of the distance from the interpolation target pixel to the pixel in the vertical direction and the distance from the interpolation pixel to the pixel in the edge direction. The method of claim 3, wherein The interpolation may include interpolating a sum of a product of a linear interpolation value of a pixel in the vertical direction and a linear interpolation value of a pixel in a direction of the edge by a respective weight, divided by a sum of the respective weights. Deinterlacing method. The method of claim 3, wherein And a ratio of the weights of the linear interpolation values of the pixels in the vertical direction and the weights of the linear interpolation values of the pixels in the edge direction is 1: 1 to 2: 1. The method of claim 1, In the interpolation step, when the direction of the edge is determined to be a vertical direction, a value that is linearly interpolated by using a pixel that is perpendicular to the interpolation target pixel among the plurality of first pixels and the plurality of second pixels. A deinterlacing method, characterized in that interpolation. The method according to claim 1 or 7, In the interpolation step, a linear interpolation value is calculated using Equation (E-1) below.

(E-1) Here, s is a distance from the interpolation target pixel to a pixel adjacent to the interpolation target pixel among the plurality of first pixels, and (1-s) is a distance from the interpolation target pixel to another pixel symmetric to the adjacent pixel. ,

,

F ₁ , f ₂ , f ₃ and f ₄ are i) pixel values of pixels in a direction perpendicular to the interpolation target pixel among the plurality of first pixels and the plurality of second pixels, or ii) the Pixel values of pixels in a first diagonal direction among the plurality of first pixels and the plurality of second pixels or i) Pixel values of pixels in a second diagonal direction among the plurality of first pixels and the plurality of second pixels Are shown in order. A plurality of first pixels included in the first upper scan line and the first lower scan line for the interpolation target pixel of the parallel scan signal, and a plurality of second pixels included in the second upper scan line and the second lower scan line are used. Edge direction determination unit for determining the direction of the edge; And In the case where the direction of the edge is determined in the first diagonal direction or the second diagonal direction, the linear interpolation value of the pixel which is perpendicular to the interpolation target pixel among the plurality of first pixels and the plurality of second pixels and And an interpolation unit configured to interpolate using a linear interpolation value of a pixel in the direction of the edge of the plurality of first pixels and the plurality of second pixels. The method of claim 9, The edge direction determination unit (i) the dispersion of pixel values of pixels in a direction perpendicular to the interpolation target pixel among the plurality of first pixels and the plurality of second pixels, ii) the plurality of first pixels and the plurality of Variance of pixel values of the pixels in the first diagonal direction among the second pixels and iii) the smallest value among the dispersion of the pixel values of the pixels in the second diagonal direction among the plurality of first pixels and the plurality of second pixels A deinterlacing apparatus, characterized in that for determining the direction to have the direction of the edge. The method of claim 9, And the interpolation unit interpolates the linear interpolation values of the pixels in the vertical direction and the linear interpolation values of the pixels in the edge direction by interpolating respective weights. The method of claim 11, wherein And the weight is determined using a ratio of the distance from the interpolation target pixel to the pixel in the vertical direction and the distance from the interpolation pixel to the pixel in the edge direction. The method of claim 11, The interpolation unit interpolates a sum of a product of a linear interpolation value of a pixel in the vertical direction and a linear interpolation value of a pixel in a direction of the edge by respective weights divided by a sum of the respective weights. De-interlacing device. The method of claim 11, And a ratio of the weights of the linear interpolation values of the pixels in the vertical direction and the weights of the linear interpolation values of the pixels in the edge direction is 1: 1 to 2: 1. The method of claim 9, When the direction of the edge is determined to be a vertical direction, the interpolation unit interpolates to a linear interpolated value using a pixel that is perpendicular to the interpolation target pixel among the plurality of first pixels and the plurality of second pixels. Deinterlacing apparatus, characterized in that. The method according to claim 9 or 15, The interpolation unit is a deinterlacing apparatus, characterized in that for calculating a linear interpolation value using the following formula (E-2).

(E-2) Here, s is a distance from the interpolation target pixel to a pixel adjacent to the interpolation target pixel among the plurality of first pixels, and (1-s) is a distance from the interpolation target pixel to another pixel symmetric to the adjacent pixel. ,

F ₁ , f ₂ , f ₃ and f ₄ are i) pixel values of pixels in a direction perpendicular to the interpolation target pixel among the plurality of first pixels and the plurality of second pixels, or ii) the Pixel values of pixels in a first diagonal direction among the plurality of first pixels and the plurality of second pixels or i) Pixel values of pixels in a second diagonal direction among the plurality of first pixels and the plurality of second pixels Are shown in order.

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