KR20080032741A - Display apparatus and control method thereof - Google Patents

Abstract

A display device and its control method are provided to reduce a motion error occurring according as motions of a foreground and a background are different and minimize a motion error generated according as a motion estimation is not performed properly. A motion estimating unit(10) divides a current frame into a plurality of blocks of a certain size and compares a current block among the plurality of blocks and a certain search region set in a previous frame to estimate a motion vector of the current block. When a difference between motion vectors of the current block and a neighbor block is greater than a certain range, a candidate vector selecting unit(20) selects the motion vector of the neighbor block as a candidate vector. A matching error calculating unit(30) searches a matching block matched to the candidate vector from the current frame and the previous frame, and calculates a matching error by comparing the candidate vector and the searched matching block. A reliability calculating unit(40) calculates the reliability of the candidate vector based on the calculated matching error. An interpolation mode selecting unit(60) selects one of a bi-directional interpolation mode which interpolates an image corresponding to the current block which uses the previous frame and the current frame and a uni-directional interpolation mode which interpolates the image by using one of the previous frame and the current frame. An interpolation ratio adjusting unit(50) adjusts an interpolation ratio by using the calculated matching error. An interpolating unit(70) interpolates the image corresponding to the current block by using the selected interpolation mode, the interpolation ratio, and the reliability.

Description

DISPLAY APPARATUS AND CONTROL METHOD THEREOF}

1 is a control block diagram of a display apparatus for correcting a motion error according to the present embodiment,

2 is a flowchart illustrating a control process of the display apparatus according to the present embodiment.

Explanation of symbols on the main parts of the drawings

10: motion estimation unit 20: fubobgetter selection unit

30: matching error calculation unit 40: reliability calculation unit

50: interpolation ratio adjustment unit 60: interpolation mode selection unit

The present invention relates to a display apparatus for correcting a motion error and a control method thereof. More particularly, the present invention relates to a display apparatus and a method for controlling the motion error generated by synthesizing an intermediate frame by estimating a motion vector.

In general, in a field-rate converter using a motion estimation and compensation technique, it is very important to find a correct motion vector and correct motion.

In the conventional motion compensating method, it is determined whether the area is covered / uncovered by using a motion vector input from the motion estimator, and accordingly, statistical filtering is used to compensate for the motion of the image.

Here, the covered region is a case in which the movement vector of the current block is in conflict with another block moving in the opposite direction, and the uncovered region is a case in which the empty block is not filled with other blocks by moving the current block.

In this case, a method of determining the covered / uncovered region may be known using a motion vector. That is, if the distance difference with the motion vector of the neighboring block is less than 0, it is determined as a covered area, and if it is greater than 0, it is determined as an uncovered area.

Alternatively, the covered / uncovered area may be determined using a matching error at a temporal position where an intermediate frame to be inserted between the current frame and the previous frame is located using the motion vector.

However, the method of determining the covered / uncovered region using the motion vector of the neighboring block considers only the direction and size of the vector. If the current block and the neighboring blocks represent the movement of a small object, if the current and some blocks correspond to the small object, the motion vector of the small object must be represented, but the motion vector alone cannot detect the motion of the foreground or the background.

Therefore, if the interpolation is performed using only the detected result, a motion error occurs. In addition, there is a problem that a motion error occurs even when a covered / uncovered area is determined using a motion vector incorrectly estimated from a motion estimator.

Accordingly, it is an object of the present invention to provide a display apparatus and a control method thereof capable of reducing movement errors caused by different movements of a foreground and a background.

Another object of the present invention is to provide a display apparatus and a method of controlling the same, which minimize a motion error occurring when a motion estimation is wrong.

According to the present invention, in the display device, the current frame is divided into a plurality of blocks of a predetermined size, and the current block and the predetermined search area set in the previous frame of the plurality of blocks by comparing the A motion estimation unit for estimating a motion vector; A candidate vector selecting unit selecting a motion vector of the neighboring block having a difference between the motion vector of the current block and the neighboring blocks more than a predetermined range as a candidate vector; A matching error calculator for searching for a matching block matched with the candidate vector in the current frame and the previous frame, and comparing the candidate vector with the searched matching block to calculate a matching error; A reliability calculator for calculating the reliability of the candidate vector based on the match error calculated from the match error calculator; Any one of a bidirectional interpolation mode for interpolating an image corresponding to the current frame using the previous frame and the current frame, and a unidirectional interpolation mode for interpolating the image using any one of the previous frame and the current frame. An interpolation mode selection unit for selecting; An interpolation ratio adjustment unit for adjusting an interpolation ratio by using matching errors calculated for forward, symmetrical, rearward, and symmetrical directions of the candidate vector; And an interpolation unit for interpolating an image corresponding to the current block by using the selected interpolation mode, the interpolation ratio, and the reliability.

The candidate vector selecting unit may select a motion vector having the largest vector distance between the motion vector of the current block and the motion vectors of neighboring blocks as an optimal candidate vector.

The interpolation mode selector may select the interpolation mode based on the still region flag of the video signal detected by a predetermined external detection means and the candidate vector.

The reliability of the candidate vector is inversely proportional to the matching error calculated from the matching error calculating unit.

On the other hand, according to the present invention, in the control method of the display apparatus, the current frame is divided into a plurality of blocks of a predetermined size, and comparing the current block and the predetermined search region set in the previous frame of the plurality of blocks Estimating a motion vector of the current block; Selecting a motion vector of the neighboring block having a difference between the motion vector of the current block and the motion vector of the neighboring blocks as a candidate vector; Retrieving a matching block matched with the candidate vector in the current frame and the previous frame, respectively; Calculating a matching error by comparing the candidate vector with the retrieved matching block; Calculating the reliability of the candidate vector based on the calculated matching error; Any one of a bidirectional interpolation mode for interpolating an image corresponding to the current block using the previous frame and the current frame, and a unidirectional interpolation mode for interpolating the image using any one of the previous frame and the current frame. Selecting; Adjusting an interpolation ratio using the matching error calculated for the candidate vector and the forward, symmetrical, rearward, and symmetrical directions of the candidate vector; And interpolating an image corresponding to the current block by using the selected interpolation mode, the interpolation ratio, and the reliability.

Hereinafter, with reference to the accompanying drawings will be described an embodiment of the present invention;

1 is a control block diagram of a display apparatus for correcting a motion error according to the present embodiment. As shown in FIG. 1, the display apparatus includes a motion estimation unit 10, a candidate vector selecting unit 20, a matching error calculating unit 30, a reliability calculating unit 40, and an interpolation ratio adjusting unit 50. ), An interpolation mode selection unit 60, and an interpolation unit 70.

The motion estimation unit estimates a motion vector by comparing a previous frame and a current frame. To this end, the motion estimation unit 10 divides the current frame into a plurality of blocks of a predetermined size. A motion vector for a block (hereinafter, referred to as a "current block") for estimating motion in the current frame is estimated, and a motion prediction error value SAD is output together.

Here, the motion estimation unit 10 estimates a motion vector for compensation of the motion through a block matching algorithm (BMA). The block matching algorithm compares two frames in units of blocks and estimates one motion vector per block.

More specifically, the motion estimation unit 10 calculates a plurality of motion prediction error values SAD by applying a block matching algorithm to each block. Then, the motion estimation unit 10 estimates the motion vector of each block from the position having the minimum motion prediction error value SAD. Here, the motion prediction error value SAD may be calculated by various methods such as Mean Absloute Difference (MAD) in addition to SAD (Sum of Absolute Difference). In addition, the motion estimation unit 10 may perform several motion corrections to estimate the correct motion vector.

The candidate vector selecting unit 20 selects a candidate vector from among motion vectors of the current block estimated from the motion estimation unit 10 and motion vectors of neighboring blocks of the current block. In this case, the candidate vector selecting unit 20 may select the candidate vector by dividing the current block into subblocks smaller than the current block and comparing motion vectors of neighboring blocks of each of the divided subblocks.

Here, the candidate vector selecting unit 20 selects a motion vector having the largest sum of the vector distances between the motion vector of the current block and the motion vector of the neighboring block as the optimal candidate vector. This is because the motion vector of the current block is unreliable when the motion vector estimated by the motion estimation unit 10 is incorrectly estimated or when the motion vector field is discontinuous because the motions of the foreground and the background are different from each other. .

If the motion vector having the smallest sum of the vector distances between the motion vector of the current block and the motion vector of the neighboring block is selected as the best candidate vector, candidate vectors may be selected using only vectors similar to the wrong motion vector. Therefore, the candidate vector having the largest vector difference from the motion vector of the current block is selected.

The candidate vectors selected by the candidate vector selection unit 20 are output to the matching error calculation unit 30, the interpolation ratio adjustment unit 50, and the interpolation mode selection unit 60, which will be described later.

The matching error calculator 30 searches for a block (hereinafter referred to as a matching block) that matches the candidate vector selected from the candidate vector selecting unit 20 in the current frame and the previous frame. Then, a matching error is calculated by comparing the candidate vector with the motion vector of the matched block of the current frame and the motion vector of the matched block of the previous frame.

The matching error may be calculated by Equation 1 below.

<Equation 1>

(Where x is the motion vector of the matching block, Vi is the candidate vector, a is the distance between the previous frame and the intermediate frame, n-1 is the previous frame, and n is the current frame.)

At this time, the matching error calculated by the matching error calculator 30 is smaller as the accuracy of the candidate vector is higher.

The reliability calculation unit 40 calculates the reliability of the candidate vector based on the matching error calculated from the matching error calculation unit 30. The reliability of the candidate vector can be calculated through Equation 2 below, and the reliability is inversely proportional to the matching error.

<Equation 2>

(Where Ø is a candidate vector and f (Ø) represents a matching error of the candidate vector.)

The interpolation mode selection unit 60 selects which of the previous frame and the current frame to generate when interpolating the image. The so-called interpolation mode selection unit 60 selects one of the bidirectional interpolation mode using both the previous frame and the current frame, and the unidirectional interpolation mode using the previous frame or the current frame.

At this time, the interpolation mode selection unit 60 selects the interpolation mode based on the still region flag and the candidate vector inputted from a predetermined external detection means, thereby eliminating distortion generated by the motion vectors of the blocks located around the still region. Minimize. Here, the still area flag is a static area inserted into an image signal for artificial processing such as a logo or a caption.

For example, it is assumed that a video signal corresponding to a matching block of a previous frame is included in a background area, and a video signal corresponding to a matching block of a current frame is included in a still area. In this case, when interpolating an image by selecting a bidirectional interpolation mode using both the matching frame of the previous frame and the current frame that matches the candidate vector, the image signal included in the still region and the image signal included in the background region are mixed with each other and distortion is generated. Will occur. Therefore, it is preferable that the interpolation mode selector 60 selects a unidirectional interpolation mode using a frame in which the video signal corresponding to the matching block is the background region.

The interpolation ratio adjustment unit 50 calculates a matching error with blocks having moved the candidate vector by a predetermined number of pixels in the forward, symmetric, and backward directions of the candidate vector. The interpolation ratio for interpolating the image is calculated according to the calculated matching error. This minimizes distortion occurring in the covered area when the motion estimation in the motion estimator is wrong or when the motion vector becomes discontinuous because the foreground and the background are different from each other.

In general, in the backward-motion estimation method that performs block matching on the basis of the current frame, it is advantageous to estimate the motion of the covered area where the background disappears from the previous frame to the current frame. Create

On the contrary, in the Forward-Motion Estimation, which performs block matching on the basis of the previous frame, it is advantageous to estimate the motion of the uncovered area where the foreground disappears from the previous frame to the current frame. Create

Therefore, the interpolation ratio adjustment unit 50 according to the present invention adjusts the interpolation ratio by using matching errors along the forward, symmetrical, rearward, and symmetrical directions of the candidate vectors.

Here, the matching error along the symmetry direction is the sum of the differences with the motion vectors matched by moving the predetermined number of pixels by the candidate vector at the time when the interpolated image is located. The matching error along the backward direction and the forward direction is the sum of the differences between the motion vectors matched when the interpolated image between the previous frame and the current frame is close.

At this time, the backward direction and the forward direction are close to 1 and 0, respectively, and the backward matching error value is relatively small in the area where the background disappears from the current frame such as the covered area, and the uncovered area and Likewise, in the region where the foreground disappears from the previous frame, the forward matching error value is relatively small.

Therefore, the interpolation ratio adjusting unit 50 adjusts the interpolation ratio to increase the weight of the current frame when generating the intermediate frame in the region where the forward matching error value is small, and the weight of the previous frame in the region where the backward matching error value is small. Adjust the interpolation rate to increase.

The weight for adjusting the interpolation ratio may be calculated by Equation 3 below.

<Equation 3>

(Where α, β, and γ are forward, backward, and symmetric directions, respectively, and f (Ø) represents a mismatch of candidate vectors.)

The interpolation ratio adjustment unit 50 adjusts the interpolation ratio by weighting the weights calculated by Equation 3 at the forward, symmetrical, and rearward split points, respectively. The interpolation ratio is calculated as in Equation 4 below.

<Equation 4>

For example, in the case of the covered area, since the backward matching error is relatively small, the weight for the rear direction is increased and the weight for the remaining directions is small. Therefore, the interpolation rate of the previous frame is increased to reduce the motion error generated when interpolating the image.

The interpolation unit 70 is an intermediate frame based on the reliability calculated by the reliability calculation unit 40, the interpolation mode selected by the interpolation mode selecting unit 60, and the interpolation ratio adjusted by the interpolation ratio adjusting unit 50. Is generated and output to the predetermined display unit.

Through this, it is possible to reduce the motion error generated when generating the intermediate frame based on the estimated motion vector.

The control method of the display apparatus according to the embodiment of the present invention described above will be described using the flowchart of FIG. 2.

As shown in FIG. 2, the motion vector of the current block is estimated (S1). As described above, the motion vector of the current block is estimated by dividing the current frame into a plurality of blocks of a predetermined size, comparing the most similar block by comparing the current search block and a predetermined search area set in the previous frame. Can be.

The motion vector of the neighboring block whose difference between the motion vector of the current block and the neighboring blocks is greater than or equal to a predetermined range is selected as a candidate vector (S3). Here, the motion vector having the largest difference in the motion vectors becomes an optimal candidate vector.

The matching blocks matched with the candidate vectors are searched in the current frame and the previous frame, respectively (S5), and the matching blocks of the searched current frame and the matching blocks in the previous frame are compared with the candidate vectors, respectively, to calculate a matching error (S7). .

The reliability of the candidate vector is calculated based on the calculated matching error (S9).

Then, the interpolation mode for interpolating the image among the previous frame and the current frame is selected (S11). That is, one of the two-way interpolation mode for interpolating the image corresponding to the current block using the previous frame and the current frame, and the one-way interpolation mode for interpolating the image using any one of the previous frame and the current frame are selected.

The interpolation ratio is then adjusted using the matching error calculated for the forward, symmetrical, backward and symmetrical directions of the candidate vector and the candidate vector (S13).

The image corresponding to the current block is interpolated using the selected interpolation mode, interpolation ratio, and reliability (S15).

Through this, a motion error may be reduced when interpolating an image based on the estimated motion vector. In addition, it is possible to minimize the motion error that occurs when the motion of the foreground and the background is different or the motion vector is incorrectly estimated.

Although some embodiments of the invention have been shown and described, it will be apparent to those skilled in the art that modifications may be made to the embodiment without departing from the spirit or spirit of the invention. . It is intended that the scope of the invention be defined by the claims appended hereto and their equivalents.

As described above, according to the present invention, there is provided a display apparatus and a control method thereof capable of reducing a motion error during image interpolation based on the estimated motion vector. In addition, there is provided a display apparatus and a method of controlling the same, which can minimize a motion error that occurs when the foreground and background motions are different or when the motion vector is incorrectly estimated.

Claims (5)

In the display device, A motion estimation unit for dividing a current frame into a plurality of blocks of a predetermined size and estimating a motion vector of the current block by comparing a current search block and a predetermined search region set in a previous frame among the plurality of blocks; A candidate vector selecting unit selecting a motion vector of the neighboring block having a difference between the motion vector of the current block and the neighboring blocks more than a predetermined range as a candidate vector; A matching error calculator for searching for a matching block matched with the candidate vector in the current frame and the previous frame, and comparing the candidate vector with the searched matching block to calculate a matching error; A reliability calculator for calculating the reliability of the candidate vector based on the match error calculated from the match error calculator; Any one of a bidirectional interpolation mode for interpolating an image corresponding to the current frame using the previous frame and the current frame, and a unidirectional interpolation mode for interpolating the image using any one of the previous frame and the current frame. An interpolation mode selection unit for selecting; An interpolation ratio adjustment unit that adjusts an interpolation ratio by using matching errors calculated for the forward, symmetrical, rearward, and symmetrical directions of the candidate vector; And an interpolator configured to interpolate an image corresponding to the current block by using the selected interpolation mode, the interpolation ratio, and the reliability. The method of claim 1, And the candidate vector selecting unit selects a motion vector having the largest vector distance between the motion vector of the current block and the motion vector of neighboring blocks as an optimal candidate vector. The method of claim 1, And the interpolation mode selection unit selects the interpolation mode based on the still region flag of the video signal detected by a predetermined external detection means and the candidate vector. The method of claim 1, The reliability of the candidate vector is And an inverse proportion to a matching error calculated from the matching error calculating unit. In the control method of the display device, Dividing a current frame into a plurality of blocks having a predetermined size, and estimating a motion vector of the current block by comparing a current search block set in a previous frame with a current block; Selecting a motion vector of the neighboring block having a difference between the motion vector of the current block and the motion vector of the neighboring blocks as a candidate vector; Retrieving a matching block matched with the candidate vector in the current frame and the previous frame, respectively; Calculating a matching error by comparing the candidate vector with the retrieved matching block; Calculating the reliability of the candidate vector based on the calculated matching error; Any one of a bidirectional interpolation mode for interpolating an image corresponding to the current block using the previous frame and the current frame, and a unidirectional interpolation mode for interpolating the image using any one of the previous frame and the current frame. Selecting; Adjusting an interpolation ratio using the matching error calculated for the candidate vector and the forward, symmetrical, rearward, and symmetrical directions of the candidate vector; And interpolating an image corresponding to the current block by using the selected interpolation mode, the interpolation ratio, and the reliability.

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