KR20080092103A - Image processing apparatus and image processing method thereof - Google Patents

Abstract

An image processing apparatus and a method are provided to improve picture quality without inserting a new frame between frames, generate sub fields with a reduced level from an image and use all the generated sub fields to enhance picture quality. An image processing apparatus(1) includes an input unit(10) for receiving continuous video signals, a motion estimator(20) for estimating a motion vector with respect to an image, an image generator(30) for generating a new image compensated by the motion estimation, and a filtering unit(40) for filtering the new image. The apparatus further includes a sub field generator(50) for generating sub fields corresponding to the received video signals and an image processor(60) for estimating the motion vector from the received continuous video signals according to the motion estimator to generate at least one new image, filtering the new image according to the filtering unit and combining the sub fields generated by the sub field generator to generate an image.

Description

Image processing apparatus and its image processing method {IMAGE PROCESSING APPARATUS AND IMAGE PROCESSING METHOD THEREOF}

1 is a diagram illustrating a relationship between luminance of an image and a human eye in a conventional image processing apparatus.

2 is a block diagram showing the configuration of an image processing apparatus according to a first embodiment of the present invention.

3 is a diagram illustrating a process of synthesizing a frame in an image processing apparatus according to the present invention.

4 is a view showing a relationship between the brightness of the image and the human eye in the image processing apparatus according to the present invention,

5 is a block diagram showing the configuration of an image processing apparatus according to a second embodiment of the present invention.

6 is a flowchart illustrating an image processing method of the image processing apparatus according to the present invention.

Explanation of symbols on the main parts of the drawings

10: input unit 20: motion estimation unit

30: image generation unit 40: filtering unit

40a: low pass filter 40b: high pass filter

50: subfield generation unit 60: image processing unit

70: reverse gamma correction unit 80: dithering unit

90: display panel

The present invention relates to an image processing apparatus and an image processing method thereof. More particularly, the present invention relates to an image processing apparatus for estimating the motion of an image and an image processing method thereof.

The image processing apparatus performs image processing to generate an image viewable by a user with respect to the input image signal. Among image processing apparatuses, a false contour may occur in an image of a moving object in a device such as a plasma display panel (PDP) or a digital mirror device (DMD) that displays gray levels using a time division method.

On the other hand, television broadcasting uses different methods such as NTSC (National Television System Committee) and PAL (Phase Alternation Line) depending on the country and region. Among them, in the case of the PAL method, since a frequency of 50 Hz is used, flicker may occur, so a plurality of subfields in a frame are divided into a first subfield group and a second subfield group, and the gray level of each subfield is divided. The sum of the sums becomes the luminance of the image to prevent the flicker phenomenon.

FIG. 1 is a diagram illustrating a relationship between luminance of an image and human vision when displaying an image by a plurality of subfields in a conventional image processing apparatus. As shown in FIG. 1, in the conventional image processing apparatus, the displayed position does not change before the predetermined reference time elapses, but the human recognizes the integrated luminance according to the trajectory of A. FIG. That is, due to the mismatch between the brightness of the image actually displayed and the time for recognizing the same, the conventional image processing apparatus has a problem in that a double edge and a motion blur are generated.

Accordingly, it is an object of the present invention to provide an image processing apparatus and an image processing method thereof capable of preventing a deterioration in image quality when displaying an image having motion by a plurality of subfields.

Another object of the present invention is to provide an image processing apparatus and an image processing method capable of improving image quality without inserting a new frame between frames.

An object of the present invention is to provide an image processing apparatus comprising: an input unit for receiving a continuous image signal; A motion estimator for estimating a motion vector for the image; An image generator which generates a new image compensated by the motion estimation; A filtering unit which performs filtering on the image; A subfield generating unit generating a subfield from the image; At least one new image is generated by estimating a motion vector by the motion estimation unit from the continuous input image signal, and the generated new image is filtered by the filtering unit to generate the subfield from the filtered image. And an image processor for combining the subfields generated by the subfield to generate a new driving subfield.

The subfield generator may generate a subfield in which the number of gray levels that can be displayed is reduced from the at least one new image.

The subfield generator may generate a first subfield and a second subfield in which the number of gray levels is reduced by 50% from the two filtered images.

The filtering unit may perform low frequency filtering on a new image compensated by the motion estimation, and perform high frequency filtering on the remaining images.

Here, it is preferable that the filtering unit performs filtering according to a temporal level.

The apparatus may further include a dithering unit which performs dithering on the filtered image.

Preferably, the new driving subfield generated by the combination of the subfields has the same frequency as the input video signal.

The video signal is preferably received according to a PAL (Phase Alternation Line) standard.

The display apparatus may further include a display panel including a plasma display panel (PDP) displaying an image generated by the new driving subfield.

On the other hand, the image processing method of the image processing apparatus, comprising the steps of: receiving a continuous image signal; Generating at least one new image by estimating a motion vector from the continuous input image signal; Performing filtering on the generated new image; Generating a subfield from the filtered image; The object is also achieved by an image processing method comprising the step of combining the generated subfields to generate a new driving subfield.

In the generating of the subfield, it is preferable to generate a subfield in which the number of gradations that can be displayed is reduced.

In the generating of the subfield, it is preferable to generate a first subfield and a second subfield in which the number of gray levels is reduced by 50% from the two filtered images.

The filtering may include performing low frequency filtering on a new image compensated by the motion estimation among the two images, and performing high frequency filtering on the remaining images.

In this case, the filtering may be performed according to a temporal level.

In addition, the performing of the filtering may further include performing dithering on the filtered image.

Preferably, the new driving subfield generated by the combination of the subfields has the same frequency as the input video signal.

In addition, the video signal is preferably received according to a PAL (Phase Alternation Line) standard.

The generating of the new driving subfield may further include displaying an image generated by the new driving subfield by a display panel configured with a plasma display panel (PDP).

Hereinafter, an image processing apparatus according to the present invention will be described in detail with reference to the accompanying drawings.

2 is a block diagram showing the configuration of an image processing apparatus 1 according to the present invention. As shown in FIG. 2, the image processing apparatus 1 according to the present invention includes an input unit 10, a motion estimation unit 20, an image generation unit 30, a filtering unit 40, and a subfield. The generator 50 and the image processor 60 are included.

The input unit 10 receives a continuous video signal. The input unit 10 according to the present invention may not only be implemented as a tuner for receiving an image signal from the outside, but also may receive an image signal corresponding to an image stored in the image processing apparatus through a predetermined interface.

The motion estimator 20 estimates a motion vector by comparing a previous frame and a current frame. The motion estimator 20 divides the current frame into a plurality of blocks having a predetermined size, estimates a motion vector of a block (hereinafter, referred to as a "current block") to estimate motion in the current frame, and predicts motion accordingly. The error value (Sum of Absolute Difference, SAD) is also output.

Here, the motion estimator 20 estimates a motion vector for motion compensation through a block matching algorithm (BMA). More specifically, the motion estimation unit 20 calculates a motion prediction error value SAD for a plurality of blocks by applying a block matching algorithm to each block. The motion estimator 20 estimates the motion vector of each block from the position having the minimum motion prediction error value SAD. Here, the motion prediction error value may be calculated by various methods such as Mean Absolute Difference (MAD) in addition to SAD. The motion estimator 20 may perform a plurality of motion corrections to estimate the correct motion vector.

The image generator 30 generates a new image compensated by the motion estimation. The image generator 30 may generate at least one new image and perform motion compensation by the motion estimator 20 on any one of the generated new images. As will be described later, when the image generator 30 newly generates two images corresponding to one frame, it is preferable to perform motion compensation on one of them.

The filtering unit 40 filters the subfields, and includes a low-pass filter 40a that performs low frequency filtering and a high-pass filter 40b that performs high frequency filtering. do.

The low pass filter 40a performs low frequency filtering to filter only low frequency components in which the applied luminance signal is distributed, and the high pass filter 40b performs high frequency filtering to filter only high frequency components in which the luminance signal is distributed. The luminance signal filtered by the filtering unit 40 may be applied to the inverse gamma correction unit 70 and the dithering unit 80 to be described later.

Here, the filtering unit 40 preferably performs temporal filtering based on a motion compensation result of the current frame from at least one adjacent frame. In other words, when encoding, filtering is performed from a frame of a low temporal level, and when decoding, conversely, filtering is performed from a frame of a high temporal level.

In addition, the filtering unit 40 may vary the passband according to the direction and magnitude of the motion vector estimated by the motion estimating unit 20.

The subfield generation unit 50 generates a plurality of subfields corresponding to the input video signal. The subfields generated by the subfield generation unit 50 are binary data representing information about a video grayscale group, and are used in an image processing apparatus such as a PDP or a digital mirror device (DMD) for processing an image according to a time division method. . In particular, in order to reduce pseudo contours, it is preferable that bit transitions between codewords of adjacent grayscales among the grayscales used are small. Table 1 below shows an example of the configuration of the subfield and the luminance weight value according to light emission of the subfield.

TABLE 1

Subfield SF1 SF2 SF3 SF4 SF5 SF6 SF7 SF8 SF9 SF10 Sum of luminance weights Luminance weighting One 2 4 8 16 24 32 44 56 68 255 ON ON ON ON ON 75 ON ON ON ON 128

Meanwhile, the subfield generation unit 50 according to the present invention generates a subfield in which the number of gray levels that can be displayed from an image is reduced. That is, the first subfield and the second subfield may be generated by reducing the number of gray levels that can be displayed in the conventional subfield by 50%. The first subfield and the second subfield generated by the subfield generator 50 are combined by the image processor 60 to be described later to generate an image having the same number of gray levels as the conventional subfield.

The image processor 60 estimates a motion vector by the motion estimator from frames of consecutive input image signals, generates at least one new image, and filters the generated new image by the filtering unit. The video image is generated by combining the subfields generated by the subfield generator from the received image.

When the motion vector of the two consecutive frames included in the image signal is estimated by the motion estimator 20, the image processor 60 compensates the plurality of subfields based on the pixels present in the trajectory of the estimated motion vector. . Then, the subfields compensated by the filtering unit 30 are filtered.

Here, the image processor 60 may perform high frequency filtering on the first subfield among the plurality of subfields and perform low frequency filtering on the second subfield whose motion is compensated. Of course, high frequency filtering may be performed on the motion-compensated second subfield, and low frequency filtering may be performed on the first subfield, but low frequency filtering may be performed on the motion-compensated second subfield. In this case, natural motion can be expressed without inserting an image between frames. In addition, by performing high frequency filtering on the first subfield whose motion is not compensated, the luminance of the original frame may be maintained.

On the other hand, when the input unit 10 of the image processing apparatus 1 according to the present invention is implemented as a tuner for receiving an image signal from the outside, it is preferable to receive the image signal according to the PAL standard. Since the PAL standard uses 50 Hz unlike the NTSC standard using a frequency of 60 Hz, the conventional image processing apparatus expresses a moving image by inserting a new interpolation frame and the like between frames, but according to the present invention, According to (1), the frequency of 50 Hz can be maintained by modifying the original frame itself.

3 is a diagram illustrating a process of generating a new driving subfield by combining the subfields by the image processor 60 according to the present invention.

As illustrated in FIG. 3, the image processor 60 performs image processing by the subfield generator 50 to generate the first subfield and the second subfield. In addition, high frequency filtering is performed on the divided first subfield, and low frequency filtering is performed on the second subfield. Here, the number of gray levels in the first subfield and the second subfield is reduced by 50% compared with the conventional subfield. Therefore, when the first subfield and the second subfield are combined, they have the same gray number as the conventional subfield. That is, the image processing apparatus 1 according to the present invention can use the subfields generated by the subfield generation unit 50 and use all of the generated subfields, thereby improving the image quality. have.

FIG. 4 is a diagram showing a relationship between luminance of an image and human vision when displaying an image by a plurality of subfields in the image processing apparatus 1 according to the present invention. Unlike the conventional image processing apparatus of FIG. 1, in the case of the image processing apparatus 1 according to the present invention, a second sub-field is displayed in which a motion is compensated and low-frequency filtered on a straight line representing a time when a human recognizes a frame. This makes it possible to eliminate double images and motion blur.

Hereinafter, the image processing apparatus 2 according to the second embodiment of the present invention will be described with reference to FIG. 5. As shown in FIG. 5, the image processing apparatus 2 according to the second embodiment of the present invention further includes an inverse gamma correction unit 70, a dithering unit 80, and a display panel 90.

The inverse gamma correction unit 70 includes an inverse gamma conversion unit (not shown) and an error diffusion unit (not shown) to correct an input / output characteristic between an input video signal and an output signal of the inverse gamma conversion unit to be an inverse gamma curve.

The dithering unit 80 compares the dither value of each halftone of the subfield of the image with the dither value of each pixel, and converts the dither value into one of adjacent video gradation groups according to the comparison result. As a result, the output quality of the video including multi-gradation can be improved.

The display panel 90 displays an image output as a frame changed by the image processor 60. The display panel 90 according to the present invention is preferably composed of a PDP for processing an image according to a time division method.

Of course, the display panel 90 according to the present invention may further include a panel driver (not shown) for driving the display panel 90 to display an image processed by the image processor 60.

The image processor 60 classifies the plurality of subfields output from the inverse gamma correction unit 70 and the dithering unit 80 into a first subfield group and a second subfield group, and transmits the subfields to the display panel 90. The output quality of a video including multi gradation can be improved, and an image suitable for the characteristics of the display panel 90 can be output.

Hereinafter, an image processing method of the image processing apparatuses 1 and 2 according to the present invention will be described with reference to FIG. 6.

First, when a continuous video signal is input (S10), a new video is generated by estimating a motion vector from the input video signal (S20). Then, the filtering unit 20 performs filtering on the new image (S30).

Here, low frequency filtering is performed on the compensated image based on the motion vector estimated by the motion estimator 20 of the two new images generated by the image generator 30, and high frequency filtering is performed on the remaining images. Preferably, the filtering unit 20 may perform filtering according to a temporal level.

In operation S40, a subfield is generated from the filtered image. Here, in step S40, it is preferable to generate a subfield in which the number of displayable gradations is reduced, and to generate the first subfield and the second subfield in which the number of gradations is reduced by 50% from the two filtered images.

Thus, the image processor 40 generates a new driving subfield by combining the subfields generated in step S40 (S50). Here, step S50 may further include displaying the image generated from the generated new driving subfield on the display panel 90.

As mentioned above, the present invention has been described in detail through preferred embodiments, but the present invention is not limited thereto and may be variously implemented within the scope of the claims.

As described above, according to the image processing apparatus and the image processing method according to the present invention, it is possible to prevent the deterioration in image quality when displaying an image having a movement by a plurality of subfields.

In addition, according to the image processing apparatus and the image processing method according to the present invention it is possible to improve the quality of the image without inserting a new frame between the frame.

In addition, according to the image processing apparatus and the image processing method according to the present invention, since the subfields having a reduced level are generated from the image and all the generated subfields are used, the image quality can be improved.

Claims (18)

In the image processing apparatus, An input unit for receiving a continuous video signal; A motion estimator for estimating a motion vector for the image; An image generator which generates a new image compensated by the motion estimation; A filtering unit which performs filtering on the image; A subfield generating unit generating a subfield from the image; At least one new image is generated by estimating a motion vector by the motion estimation unit from the continuous input image signal, and the generated new image is filtered by the filtering unit to generate the subfield from the filtered image. And an image processing unit for generating a new driving subfield by combining the subfields generated by the unit. The method of claim 1, And the subfield generation unit generates a subfield in which the number of gray levels that can be displayed is reduced from the at least one new image. The method of claim 1, And the subfield generator generates a first subfield and a second subfield in which the number of gray levels is reduced by 50% from the two filtered images. The method of claim 2, The filtering unit may perform low frequency filtering on a new image compensated by the motion estimation among the two images, and perform high frequency filtering on the remaining images. The method of claim 1, And the filtering unit performs filtering according to a temporal level. The method of claim 1, And a dithering unit for dithering the filtered image. The method of claim 1, And the new driving subfield generated by the combination of the subfields has the same frequency as the input video signal. The method of claim 7, wherein And the image signal is received according to a PAL (Phase Alternation Line) standard. The method of claim 1, And a display panel including a plasma display panel (PDP) for displaying an image generated by the new driving subfield. In the image processing method of the image processing apparatus, Receiving a continuous video signal; Generating at least one new image by estimating a motion vector from the continuous input image signal; Performing filtering on the generated new image; Generating a subfield from the filtered image; And combining the generated subfields to generate a new driving subfield. The method of claim 10, The generating of the subfield may include generating a subfield having a reduced number of displayable gradations. The method of claim 11, The generating of the subfield may include generating a first subfield and a second subfield in which the number of gray levels is reduced by 50% from the two filtered images. The method of claim 12, The performing of the filtering may include performing low frequency filtering on a new image compensated by the motion estimation among the two images, and performing high frequency filtering on the remaining images. The method of claim 10, The performing of the filtering may include filtering according to a temporal level. The method of claim 10, Performing the filtering, And dithering the filtered image. The method of claim 10, And the new driving subfield generated by the combination of the subfields has the same frequency as the input video signal. The method of claim 16, And the video signal is received according to a PAL (Phase Alternation Line) standard. The method of claim 10, Generating the new driving subfield may include: And displaying an image generated by the new driving subfield by a display panel composed of a plasma display panel (PDP).

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