KR101477546B1 - Apparatus for decoding motion vector - Google Patents

Abstract

An image decoding apparatus is disclosed. The video decoding apparatus determines neighboring blocks having a motion vector among neighboring blocks of the current block, determines a predicted motion vector candidate among the motion vectors of the determined neighboring blocks, and determines, based on the prediction mode information of the current block, A predictor for determining a predicted motion vector of the current block among predicted motion vector candidates; And a motion vector restoring unit for obtaining a motion vector of the current block based on the predictive motion vector and a difference vector obtained from the bitstream, wherein the neighboring blocks include a first block located outside and a left lower end of the current block, Block.

Description

[0001] Apparatus for decoding motion vector [

The present invention relates to motion vector decoding, and more particularly, to an apparatus for decoding a predictive motion vector of a current block.

In a codec such as MPEG-4 H.264 / MPEG-4 Advanced Video Coding (AVC), a motion vector of a previously coded block adjacent to a current block is used to predict a motion vector of the current block. The median of the motion vectors of the previous coded blocks adjacent to the upper left, the upper and the upper right of the current block is used as a motion vector predictor of the current block.

SUMMARY OF THE INVENTION The present invention provides a method and apparatus for encoding and decoding motion vectors, and a computer-readable recording medium having recorded thereon a program for executing the method.

According to an aspect of the present invention, there is provided an apparatus for decoding an image, the apparatus comprising: a motion estimation unit that determines neighboring blocks having a motion vector among neighboring blocks of a current block, A predictor for determining a predicted motion vector of the current block among the predicted motion vector candidates based on prediction mode information of the current block; And a motion vector restoring unit for obtaining a motion vector of the current block based on the predictive motion vector and a difference vector obtained from the bitstream, wherein the neighboring blocks include a first block located outside and a left lower end of the current block, Block.

According to an embodiment, the predictive motion vector candidate may further include a motion vector of a block at the same position of a reference picture at the same position as the current block of the current picture.

According to an embodiment, the predicting unit may scale the motion vector of the block at the same position based on the temporal distance between the reference picture and the current picture.

According to one embodiment, the image is hierarchically divided from a maximum encoding unit according to the maximum encoding unit size information according to a depth, and a current depth encoding unit is divided into a plurality of square data units Wherein the coding unit of the current depth is divided into coding units of lower depth independently of neighboring coding units and the coding units of the hierarchical structure include coding units among the coding units divided from the maximum coding unit can do.

1 illustrates an image encoding apparatus according to an embodiment of the present invention.
FIG. 2 illustrates an image decoding apparatus according to an embodiment of the present invention.
FIG. 3 illustrates a hierarchical encoding unit according to an embodiment of the present invention.
FIG. 4 illustrates an image encoding unit based on an encoding unit according to an embodiment of the present invention.
FIG. 5 illustrates an image decoding unit based on an encoding unit according to an embodiment of the present invention.
FIG. 6 illustrates a maximum encoding unit, a sub-encoding unit, and a prediction unit according to an embodiment of the present invention.
7 shows an encoding unit and a conversion unit according to an embodiment of the present invention.
FIGS. 8A and 8B show a division form of an encoding unit, a prediction unit, and a frequency conversion unit according to an embodiment of the present invention.
9 illustrates an apparatus for encoding a motion vector according to an embodiment of the present invention.
10A and 10B show predicted motion vector candidates in explicit mode according to an embodiment of the present invention.
Figures 11A-11C illustrate predicted motion vector candidates in explicit mode in accordance with another embodiment of the present invention.
12 illustrates a method of generating a predictive motion vector of an implicit mode according to an embodiment of the present invention.
13 shows an apparatus for decoding a motion vector according to an embodiment of the present invention.
14 is a flowchart illustrating a method of coding a motion vector according to an embodiment of the present invention.
15 is a flowchart illustrating a method of decoding a motion vector according to an embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.

1 illustrates an image encoding apparatus according to an embodiment of the present invention.

1, an image encoding apparatus 100 according to an exemplary embodiment of the present invention includes a maximum encoding unit division unit 110, an encoding depth determination unit 120, an image data encoding unit 130, (140).

The maximum coding unit division unit 110 may divide the current picture or the current slice based on the maximum coding unit which is the coding unit of the maximum size. The current picture or current slice can be divided into at least one maximum encoding unit.

According to an embodiment of the present invention, an encoding unit can be expressed using a maximum encoding unit and a depth. As described above, the maximum coding unit indicates the largest coding unit among the coding units of the current picture, and the depth indicates the size of the sub-coding unit in which the coding units are hierarchically reduced. As the depth increases, the encoding unit can be reduced from the maximum encoding unit to the minimum encoding unit, the depth of the maximum encoding unit can be defined as the minimum depth, and the depth of the minimum encoding unit can be defined as the maximum depth. As the depth of the maximum encoding unit increases, the size of the depth-dependent encoding unit decreases. Thus, the sub-encoding unit of k depth may include a sub-encoding unit of depth greater than a plurality of k.

As the size of a picture to be encoded increases, if an image is coded in a larger unit, the image can be encoded with a higher image compression rate. However, if the coding unit is enlarged and its size is fixed, the image can not be efficiently encoded reflecting the characteristics of the continuously changing image.

For example, when coding a flat area with respect to the sea or sky, the compression rate can be improved by increasing the coding unit. However, when coding a complex area for people or buildings, the compression ratio is improved as the coding unit is decreased.

To this end, one embodiment of the present invention sets a different maximum picture encoding unit for each picture or slice, and sets a maximum depth. Since the maximum depth means the maximum number of times the encoding unit can be reduced, the minimum encoding unit size included in the maximum image encoding unit can be variably set according to the maximum depth.

The encoding depth determination unit 120 determines the maximum depth. The maximum depth may be determined based on the Rate-Distortion Cost calculation. The maximum depth may be determined differently for each picture or slice, or may be determined differently for each maximum encoding unit. The determined maximum depth is output to the encoding information encoding unit 140, and the image data for each maximum encoding unit is output to the image data encoding unit 130.

The maximum depth means the smallest encoding unit, that is, the minimum encoding unit, which can be included in the maximum encoding unit. In other words, the maximum encoding unit may be divided into sub-encoding units of different sizes according to different depths. Will be described later in detail with reference to Figs. 8A and 8B. Further, the sub-encoding units of different sizes included in the maximum encoding unit can be predicted or frequency-converted based on the processing units of different sizes. In other words, the image encoding apparatus 100 can perform a plurality of processing steps for image encoding based on various sizes and processing units of various types. In order to encode video data, processing steps such as prediction, frequency conversion, and entropy encoding are performed. Processing units of the same size may be used in all stages, and processing units of different sizes may be used in each step.

For example, in order to predict a coding unit, the image coding apparatus 100 may select a coding unit and a different processing unit.

If the size of the encoding unit is 2Nx2N (where N is a positive integer), the processing unit for prediction may be 2Nx2N, 2NxN, Nx2N, NxN, and the like. In other words, motion prediction may be performed based on a processing unit of a type that halves at least one of a height or a width of an encoding unit. Hereinafter, a data unit serving as a basis of prediction is referred to as a 'prediction unit'.

The prediction mode may be at least one of an intra mode, an inter mode, and a skip mode, and the specific prediction mode may be performed only for a prediction unit of a specific size or type. For example, the intra mode can be performed only for a 2Nx2N, NxN sized prediction unit, which is a square. In addition, the skip mode can be performed only for a prediction unit of 2Nx2N size. If there are a plurality of prediction units in an encoding unit, a prediction mode having the smallest coding error can be selected by performing prediction for each prediction unit.

Also, the image encoding apparatus 100 can frequency-convert image data based on a processing unit having a different size from the encoding unit. The frequency conversion may be performed based on a data unit having a size smaller than or equal to the encoding unit for frequency conversion of the encoding unit. Hereinafter, a processing unit serving as a basis of frequency conversion is referred to as a 'conversion unit'.

The coding depth determiner 120 may determine sub-coding units included in the maximum coding unit using Rate-Distortion Optimization based on a Lagrangian Multiplier. In other words, it is possible to determine what type of sub-encoding unit the maximum encoding unit is divided into, wherein the plurality of sub-encoding units have different sizes depending on the depth. Then, the image data encoding unit 130 encodes the maximum encoding unit based on the division type determined by the encoding depth determination unit 120, and outputs the bit stream.

The encoding information encoding unit 140 encodes information on the encoding mode of the maximum encoding unit in the encoding depth determining unit 120. [ Information on the division type of the maximum encoding unit, information on the maximum depth, and information on the encoding mode of the sub-encoding unit by depth, and outputs the bit stream. The information on the encoding mode of the sub-encoding unit may include information on the prediction unit of the sub-encoding unit, prediction mode information per prediction unit, information on the conversion unit of the sub-encoding unit, and the like.

There is a sub-encoding unit of a different size for each maximum encoding unit, and information on the encoding mode is determined for each sub-encoding unit, so that information on at least one encoding mode can be determined for one maximum encoding unit.

As the depth increases, the image encoding apparatus 100 may generate a sub-encoding unit by dividing the maximum encoding unit by half the height and the width. That is, if the size of the encoding unit of the kth depth is 2Nx2N, the size of the encoding unit of the k + 1th depth is NxN.

Accordingly, the image decoding apparatus 100 according to an exemplary embodiment can determine an optimum division type for each maximum encoding unit based on the size and the maximum depth of a maximum encoding unit considering characteristics of an image. It is possible to more efficiently encode images of various resolutions by adjusting the size of the maximum encoding unit in consideration of the image characteristics and encoding the image by dividing the maximum encoding unit into sub-encoding units of different depths.

FIG. 2 illustrates an image decoding apparatus according to an embodiment of the present invention.

2, an image decoding apparatus 200 according to an exemplary embodiment of the present invention includes an image data obtaining unit 210, an encoding information extracting unit 220, and an image data decoding unit 230.

The image-related data acquisition unit 210 parses the bit stream received by the image decoding apparatus 200, acquires image data for each maximum encoding unit, and outputs the image data to the image data decoding unit 230. The image data obtaining unit 210 may extract information on the maximum coding unit of the current picture or slice from the header of the current picture or slice. In other words, the bitstream is divided into a maximum encoding unit, and the video data decoding unit 230 decodes the video data per maximum encoding unit.

The encoding information extracting unit 220 parses the bit stream received by the video decoding apparatus 200 and extracts a maximum encoding unit, a maximum depth, a division type of the maximum encoding unit, and a coding mode of the sub-encoding unit from the header for the current picture . The information on the division type and the encoding mode is output to the video data decoding unit 230. [

The information on the division type of the maximum encoding unit may include information on sub-encoding units of different sizes according to the depth included in the maximum encoding unit, the information on the encoding mode may include information on a prediction unit for each sub- Information on the prediction mode, information on the conversion unit, and the like.

The image data decoding unit 230 decodes the image data of each maximum encoding unit based on the information extracted by the encoding information extracting unit to restore the current picture. The image data decoding unit 230 can decode the sub-encoding unit included in the maximum encoding unit based on the information on the division type of the maximum encoding unit. The decoding process may include a motion prediction process including intra prediction and motion compensation, and an inverse frequency conversion process.

The image data decoding unit 230 may perform intra prediction or inter prediction based on information on a prediction unit for each sub-coding unit and prediction mode information for prediction of a sub-coding unit. In addition, the image data decoding unit 230 can perform frequency inverse transform for each sub-encoding unit on the basis of the information on the conversion unit of the sub-encoding unit.

FIG. 3 illustrates a hierarchical encoding unit according to an embodiment of the present invention.

Referring to FIG. 3, the hierarchical coding unit according to the present invention may include 32x32, 16x16, 8x8, and 4x4 from a coding unit having a width x height of 64x64. In addition to the square-shaped encoding units, there may be encoding units whose width x height is 64x32, 32x64, 32x16, 16x32, 16x8, 8x16, 8x4, 4x8.

Referring to FIG. 3, the maximum encoding unit size is set to 64x64 and the maximum depth is set to 2 for the image data 310 having a resolution of 1920x1080.

The size of the maximum encoding unit is set to 64x64 and the maximum depth is set to 4 for the image data 320 having another resolution of 1920x1080. For the video data 330 having a resolution of 352x288, the size of the maximum encoding unit is set to 16x16 and the maximum depth is set to 2. [

It is desirable that the maximum size of the encoding size is relatively large in order to accurately reflect not only the compression ratio but also the image characteristic when the resolution is high or the data amount is large. Therefore, the size of the maximum encoding unit of the image data 310 and 320 having a higher resolution than the image data 330 can be selected to be 64x64.

The maximum depth indicates the total number of layers in the hierarchical encoding unit. Since the maximum depth of the image data 310 is 2, the coding unit 315 of the image data 310 is divided into sub-coding units 315 having a major axis size of 32 and 16 as the depth increases, .

On the other hand, since the maximum depth of the image data 330 is 2, the encoding unit 335 of the image data 330 is encoded from the maximum encoding units having the major axis size of 16 to the encoding units having the major axis size of 8 and 4 Units.

Since the maximum depth of the video data 320 is 4, the encoding unit 325 of the video data 320 has a length of 32, 16, 8, and 4 as the depth increases, Sub-encoding units. As the depth increases, the image is encoded based on a smaller sub-encoding unit, which makes it suitable for encoding an image including a finer scene.

FIG. 4 illustrates an image encoding unit based on an encoding unit according to an embodiment of the present invention.

The intra prediction unit 410 performs intra prediction on a prediction unit of the intra mode of the current frame 405 and the motion estimation unit 420 and the motion compensation unit 425 perform intra prediction on the prediction unit of the intra mode, 405 and a reference frame 495. The inter-prediction and the motion compensation are performed using the reference frame 495 and inter-prediction.

The residual values are generated based on the prediction unit output from the intra prediction unit 410, the motion estimation unit 420 and the motion compensation unit 425, and the generated residual values are input to the frequency conversion unit 430 and the quantization unit 420. [ (440) and output as quantized transform coefficients.

The quantized transform coefficients are restored to a residual value through the inverse quantization unit 460 and the frequency inverse transform unit 470. The restored residual values are passed through the deblocking unit 480 and the loop filtering unit 490, And output to the reference frame 495. [ The quantized transform coefficient may be output to the bitstream 455 via the entropy encoding unit 450.

In order to perform encoding according to the image encoding method according to an embodiment of the present invention, an intra prediction unit 410, a motion estimation unit 420, a motion compensation unit 425, The inverse quantization unit 460, the inverse quantization unit 470, the deblocking unit 480 and the loop filtering unit 490 of the quantization unit 430, the quantization unit 440, the entropy coding unit 450, the inverse quantization unit 460, , Sub-encoding units according to depth, prediction units, and conversion units.

FIG. 5 illustrates an image decoding unit based on an encoding unit according to an embodiment of the present invention.

The bitstream 505 passes through the parser 510 and the encoded image data to be decoded and the encoding information necessary for decoding are parsed. The encoded image data is output as inverse-quantized data through the entropy decoding unit 520 and the inverse quantization unit 530, and is restored to the residual values through the frequency inverse transform unit 540. [ The residual values are added to the intraprediction result of the intraprediction unit 550 or the motion compensation result of the motion compensation unit 560, and restored for each encoding unit. The reconstructed coding unit is used for predicting the next coding unit or the next picture through the deblocking unit 570 and the loop filtering unit 580.

A parsing unit 510, an entropy decoding unit 520, an inverse quantization unit 530, an inverse frequency transforming unit (hereinafter referred to as an inverse quantization unit) 530, The intra prediction unit 550, the motion compensation unit 560, the deblocking unit 570 and the loop filtering unit 580 are all based on the maximum encoding unit, the depth-dependent sub-encoding unit, the prediction unit, And processes the image decoding processes.

In particular, the intra prediction unit 550 and the motion compensation unit 560 determine a prediction unit and a prediction mode in the sub-coding unit in consideration of the maximum coding unit and the depth, and the frequency inverse transform unit 540 considers the size of the conversion unit Thereby performing frequency inverse transform.

FIG. 6 illustrates a maximum encoding unit, a sub-encoding unit, and a prediction unit according to an embodiment of the present invention.

The image encoding apparatus 100 and the image decoding apparatus 200 according to an embodiment of the present invention use a hierarchical encoding unit to perform encoding and decoding in consideration of image characteristics. The maximum encoding unit and the maximum depth may be adaptively set according to the characteristics of the image, or may be variously set according to the demand of the user.

The hierarchical structure 600 of the encoding unit according to an embodiment of the present invention shows a case where the height and the width of the maximum encoding unit 610 are 64 and the maximum depth is 4. The depth increases along the vertical axis of the hierarchical structure 600 of the encoding unit, and the height and width of the sub-encoding units 620 to 650 decrease as the depth increases. Prediction units of the maximum encoding unit 610 and the sub-encoding units 620 to 650 are shown along the horizontal axis of the hierarchical structure 600 of the encoding units.

The maximum encoding unit 610 has a depth of 0, and the size of the encoding unit, i.e., the height and the width, is 64x64. A sub-encoding unit 620 having a depth 1 of 32x32 and a sub-encoding unit 630 having a depth 16x16 having a depth of 16x16, a sub-encoding unit 640 having a depth of 3x8 having a size 8x8, There is a sub-encoding unit 650 of depth 4. A sub-encoding unit 650 of depth 4 with a size of 4x4 is the minimum encoding unit.

Referring to FIG. 6, examples of prediction units along the horizontal axis are shown for each depth. That is, the prediction unit of the maximum coding unit 610 of depth 0 is a prediction unit 610 of size 64x64, a prediction unit 612 of size 64x32, and size 32x64, which are the same or smaller than the coding unit 610 of size 64x64, A prediction unit 614 of size 32x32, and a prediction unit 616 of size 32x32.

The prediction unit of the 32x32 coding unit 620 having the depth 1 has the prediction unit 620 of the size 32x32 which is equal to or smaller than the coding unit 620 of the size 32x32, the prediction unit 622 of the size 32x16, A prediction unit 624 of size 16x16, and a prediction unit 626 of size 16x16.

The prediction unit of the 16x16 encoding unit 630 of depth 2 has a prediction unit 630 of 16x16 size, a prediction unit 632 of size 16x8, and a size of 8x16, which are the same or smaller than the encoding unit 630 of size 16x16. A prediction unit 634 of size 8x8, and a prediction unit 636 of size 8x8.

The prediction unit of the 8x8 encoding unit 640 of depth 3 has a prediction unit 640 of size 8x8, a prediction unit 642 of size 8x4, and a size of 4x8, which are the same or smaller than the encoding unit 640 of size 8x8. A prediction unit 644 of size 4x4, and a prediction unit 646 of size 4x4.

Finally, the coding unit 650 of size 4x4 is the minimum coding unit and the coding unit of maximum depth, and the prediction unit is the prediction unit 650 of size 4x4.

7 shows an encoding unit and a conversion unit according to an embodiment of the present invention.

The image encoding apparatus 100 and the image decoding apparatus 200 according to an embodiment of the present invention encode the maximum encoding unit as a unit or encode the maximum encoding unit in units of sub encoding units smaller than or equal to the maximum encoding unit. The size of a conversion unit for frequency conversion during encoding is selected as a conversion unit that is not larger than each encoding unit. For example, when the current encoding unit 710 is 64x64, the frequency conversion can be performed using the 32x32 conversion unit 720. [

FIGS. 8A and 8B show a division form of an encoding unit, a prediction unit, and a frequency conversion unit according to an embodiment of the present invention.

8A shows an encoding unit and a prediction unit according to an embodiment of the present invention.

The left side of FIG. 8A shows a division type selected by the image encoding apparatus 100 according to an embodiment of the present invention to encode the maximum encoding unit 810. The image encoding apparatus 100 divides the maximum encoding unit 810 into various types, encodes the encoded image, and then selects an optimal division type by comparing the encoding results of various division types based on the R-D cost. When it is optimal to directly encode the maximum encoding unit 810, the maximum encoding unit 800 may be encoded without dividing the maximum encoding unit 810 as shown in FIGS. 8A and 8B.

Referring to the left side of FIG. 8A, a maximum encoding unit 810 having a depth of 0 is divided into sub-encoding units having a depth of 1 or more and encoded. The maximum encoding unit 810 is divided into sub-encoding units of four depths 1, and then all or a part of the sub-encoding units of depth 1 are divided into sub-encoding units of depth 2 again.

Among the sub-coding units of depth 1, sub-coding units coded at the upper right and sub-coding units located at the lower left are divided into sub-coding units of depth 2 or more. Some of the sub-encoding units having depths of 2 or more may be further divided into sub-encoding units having depths of 3 or more.

The right side of FIG. 8B shows the division type of the prediction unit for the maximum coding unit 810.

Referring to the right side of FIG. 8A, the prediction unit 860 for the maximum coding unit can be divided into the maximum coding unit 810 and the prediction unit 860 for the maximum coding unit. In other words, the prediction unit for each of the sub-encoding units may be smaller than the sub-encoding unit.

For example, a prediction unit for a sub-coding unit 854 coded right below the sub-coding unit at depth 1 may be smaller than the sub-coding unit 854. The prediction unit for some of the sub-encoding units 815, 816, 850, and 852 among the sub-encoding units 814, 816, 818, 828, 850, and 852 at the depth 2 may be smaller than the sub- In addition, the prediction unit for the sub-coding units 822, 832, and 848 of depth 3 may be smaller than the sub-coding unit. The prediction unit may be a form in which each sub-coding unit is halved in the height or width direction, or may be divided into four in height and width directions.

FIG. 8B shows a prediction unit and a conversion unit according to an embodiment of the present invention.

The left side of FIG. 8B shows the division form of the prediction unit for the maximum coding unit 810 shown on the right side of FIG. 8A, and the right side of FIG. 8B shows the division form of the conversion unit of the maximum coding unit 810.

Referring to the right side of FIG. 8B, the division type of the conversion unit 870 may be set differently from the prediction unit 860. [

For example, even if the prediction unit for the depth 1 encoding unit 854 is selected to be half the height, the conversion unit may be selected to be the same size as the depth unit 854 encoding unit. Likewise, even if the prediction unit for the depth 2 coding units 814 and 850 is selected in such a manner that the height of the depth level 2 coding units 814 and 850 is halved, the level of the level 2 coding units 814 and 850 It can be selected to be the same size as the original size.

The conversion unit may be selected to be smaller than the prediction unit. For example, if the prediction unit for depth 2 coding unit 852 is chosen to be half the width, the conversion unit may be selected to be half the width and height, which is a smaller size than the prediction unit.

9 illustrates an apparatus for encoding a motion vector according to an embodiment of the present invention.

The apparatus for encoding a motion vector included in the image encoding apparatus 100 described above with reference to FIG. 1 or the image encoding unit 400 described with reference to FIG. 4 is illustrated in detail. Referring to FIG. 9, a motion vector coding apparatus 900 according to an embodiment of the present invention includes a predictor 910, a first encoder 920, and a second encoder 930.

In order to decode a block coded by inter prediction or inter-picture prediction, information on a motion vector indicating a position difference between a current block and a similar block in a reference picture is needed. Therefore, when the image coding is performed, the information on the motion vector is encoded and inserted into the bitstream. If the information on the motion vector is directly encoded and inserted, an overhead for coding information on the motion vector increases And the compression rate of the video data is lowered.

Therefore, in the image coding, only the difference vector between the motion vector predictor and the original motion vector generated as a result of the prediction is predicted, and information about the motion vector is also inserted Compress. FIG. 9 shows an apparatus for coding a motion vector using such a predictive motion vector.

Referring to FIG. 9, the predictor 910 determines whether a predictive motion vector of a current block is predictively encoded based on an explicit mode or an implicit mode.

As described above, in a codec such as MPEG-4 H.264 / MPEG-4 AVC (Advanced Video Coding), a motion vector of a previously coded block adjacent to a current block is used to predict a motion vector of the current block. The median of the motion vectors of the previous coded blocks adjacent to the upper left, upper and right upper portions of the current block is used as the predicted motion vector of the current block. Since the motion vectors of all blocks coded using inter prediction are predicted using the same method, it is not necessary to separately encode information for the predicted motion vectors. However, in order to more accurately predict a motion vector, the image encoding apparatus 100 or the image encoding unit 400 according to the present invention may include a mode in which information on the predictive motion vector is not separately encoded, Encoding mode are all used, which will be described later in detail.

(1) explicit mode

One of the methods for encoding the predictive motion vector that can be selected by the prediction unit 910 may be a mode for explicitly encoding information about the predictive motion vector of the current block. This mode computes at least one predicted motion vector candidate and separately encodes information indicating which of the predicted motion vectors is used to predict a motion vector of the current block. The predictive motion vector candidates of the present invention will be described with reference to Figs. 10A, 10B, 11A to 11C.

10A and 10B show predicted motion vector candidates in explicit mode according to an embodiment of the present invention.

Referring to FIG. 10A, a motion vector prediction method according to an embodiment of the present invention can use one of motion vectors of previously coded blocks adjacent to a current block as a predicted motion vector of a current block. The block a0, the block a0, the block a2, the block a3, the block a3, the block a3, the block a3, Can be used as a motion vector.

Referring to FIG. 10B, a motion vector of all adjacent blocks of the current block can be used as a predicted motion vector of the current block. In other words, not only the leftmost a block of the blocks adjacent to the uppermost block but also the motion vectors of all the blocks adjacent to the uppermost block can be used as a predicted motion vector of the current block. In addition to the uppermost b0 block among the blocks adjacent to the left, The motion vector of all blocks adjacent to the current block can be used as a predicted motion vector of the current block.

In addition, a median of motion vectors of adjacent blocks can be used as a predicted motion vector. In other words, median (mv_a0, mv_b0, mv_c) can be used as the predicted motion vector of the current block. Here, mv_a0 is a motion vector of the a0 block, mv_b0 is a motion vector of the b0 block, and mv_c is a motion vector of the c block.

Figures 11A-11C illustrate predicted motion vector candidates in explicit mode in accordance with another embodiment of the present invention.

FIG. 11A illustrates a method of calculating a predictive motion vector of a B-directional predictive picture according to an embodiment of the present invention. If the current picture including the current block is a B-picture for bidirectional prediction, the motion vector generated based on the temporal distance may be a predicted motion vector candidate.

The predicted motion vector of the current block 1100 of the current picture 1110 may be generated using the motion vector of the block 1120 of the same colocated temporal preceding picture 1112. [ For example, if the motion vector mv_colA of the block 1120 in the same position as the current block 1100 is generated for the retrieved block 1122 of the temporally following picture 1114 of the current picture 1110, 1100), mv_L0A and mv_L1A, which are predicted motion vector candidates, can be generated as follows.

mv_L1A = (t1 / t2) x mv_colA

mv_L0A = mv_L1A - mv_colA

Here, mv_L0A denotes a predicted motion vector of the current block 1110 with respect to a temporally preceding picture 1112, and mv_L1A denotes a predictive motion vector of the current block 1110 with respect to a temporally following picture 1114 do.

FIG. 11B shows a method of generating a predictive motion vector of a B-directional predictive picture according to another embodiment of the present invention. Compared with the method shown in Fig. 11A, there is a difference in that a temporally following picture 1114 has a block at the same position as the current block 1100. Fig.

11B, the predicted motion vector of the current block 1100 of the current picture 1110 may be generated using the motion vector of the block 1130 of the same position (colocated) of the temporally following picture 1114 . For example, if the motion vector mv_colB of the block 1130 in the same position as the current block 1100 is generated for the retrieved block 1132 of the temporally preceding picture 1112 of the current picture 1110, 1100) mv_L0B and mv_L1B, which are predicted motion vector candidates, can be generated as follows.

mv_L0B = (t3 / t4) x mv_colB

mv_L1B = mv_L0B - mv_colB

Here, mv_L0B denotes a predicted motion vector of the current block 1110 with respect to a temporally preceding picture 1112, and mv_L1A denotes a predictive motion vector of the current block 1100 with respect to a temporally following picture 1114 do.

In generating the predicted motion vector of the current block 1100 of the B-picture, at least one of the method shown in Fig. 11A and the method shown in Fig. 11B can be used. In other words, the motion vector of the block 1120 or 1130 at the same position as the current block 1100 is used to generate the predicted motion vector using the temporal distance, 11a and 11b to generate a predicted motion vector. Accordingly, the predictor 910 according to the present invention generates a predicted motion vector of the current block 1100 using only the block having the motion vector for the corresponding block among the blocks 1120 and 1130 of the same position.

For example, when the block 1120 at the same position in the temporally preceding picture 1112 is coded using intra prediction rather than inter prediction, the motion vector of the corresponding block 1120 does not exist. Therefore, It is not possible to generate a predicted motion vector of the current block 1100 using a method of generating a predictive motion vector as shown in FIG.

FIG. 11C shows a method of generating a predictive motion vector of a P-picture (Predictive Picture) according to an embodiment of the present invention.

11C, the predicted motion vector of the current block 1100 of the current picture 1110 may be generated using the motion vector of the block 1140 of the same colocated temporal preceding picture 1112 . For example, if the motion vector mv_colC of the block 1130 at the same position as the current block 1100 is generated for the retrieved block 1142 of another temporally preceding picture 1116, the prediction of the current block 1100 Mv_L0C, which is a motion vector candidate, can be generated as follows.

mv_L0C = (t6 / t5) x mv_colC

Since the current picture 1110 is a P picture, only one candidate of the predicted motion vector of the current block 1100 is generated, unlike in FIGS. 11A and 11B.

Taken together, a set C of predicted motion vector candidates may be generated as follows according to FIGS. 10A and 10B and FIGS. 11A through 11C as follows.

Mv_b0, mv_b1, ..., mv_bN, mv_c, mv_d, mv_e, mv_temporal}, mv_a0, mv_a1,

Or, the number of prediction motion vector candidates may be reduced.

C = {median (mv_a ', mv_b', mv_c '), mv_a', mv_b ', mv_c', mv_temporal}

Here, mv_x denotes a motion vector of x block, median () denotes a median value, and mv_temporal denotes predicted motion vector candidates generated using the temporal distance described above with reference to Figs. 11A to 11C.

Also, mv_a 'denotes the first motion vector effective among mv_a0, mv_a1 ... mv_aN. For example, when the a0 block is coded using intraprediction, mv_a0, which is a motion vector of a0, is not valid, so mv_a '= mv_a1 and mv_a' = mv_a2 when the motion vector of a1 block is also invalid.

Likewise, mv_b 'denotes the first motion vector valid among mv_b0, mv_b1, ..., mv_bN, and mv_c' denotes the first motion vector valid among mv_c, mv_d, and mv_e.

The explicit mode is a mode for coding information indicating which motion vector of the set C is used as a predicted motion vector of the current block. For example, when coding a motion vector in the explicit mode, a binary number corresponding to each of the elements of the C set, that is, the predicted motion vector candidates is allocated, and when one of them is used as a predicted motion vector of the current block, a corresponding binary number Can be output.

It will be appreciated by those skilled in the art that other predictive motion vector candidates other than all the predictive motion vector candidates described above with respect to the explicit mode can be used.

(2) Implicit mode

Another method of coding the predictive motion vector that can be selected by the prediction unit 910 is to indicate that the predictive motion vector of the current block is generated based on a block or pixel included in a previously encoded area adjacent to the current block It is a mode to encode information only. Unlike the explicit mode, this mode is a mode in which information for specifying a predictive motion vector is not encoded but only information indicating that the predictive motion vector is generated in an implicit mode.

As described above, in a codec such as MPEG-4 H.264 / MPEG-4 AVC (Advanced Video Coding), a motion vector of a previously coded block adjacent to a current block is used to predict a motion vector of the current block. The median of the motion vectors of the previous coded blocks adjacent to the upper left, upper and right upper blocks of the current block is used as a predicted motion vector of the current block. In this case, information for selecting one of the predicted motion vector candidates It is not necessary to encode it.

In other words, in the image coding process, if only information indicating that the predictive motion vector of the current block is coded in the implicit mode is coded, in the image decoding process, the motion vectors of the previous decoded blocks adjacent to the left, The median value can be used as the predicted motion vector of the current block.

Also, the image encoding method according to the present invention provides a new implicit mode in addition to the method of using the median of the motion vectors of the previous coded blocks adjacent to the left, upper, and upper right of the current block as a predicted motion vector. Will be described in detail with reference to FIG.

12 illustrates a method of generating a predictive motion vector of an implicit mode according to an embodiment of the present invention.

Referring to FIG. 12, pixels 1222 contained in a previously encoded region 1220 adjacent to a current block are used in generating a predicted motion vector of a current block 1200 of a current picture 1210. The neighboring pixels 1222 are used to search the reference picture 1212 to determine the corresponding pixels 1224. The Sum of Absolute Difference (SAD) may be calculated to determine the corresponding pixels 1224. Once the corresponding pixels 1224 are determined, the motion vector mv_template of the neighboring pixels 1222 is generated and mv_template can be used as the predicted motion vector of the current block 1200.

If the mode for using the median of the motion vectors of adjacent blocks as a predictive motion vector is implicit mode_1 and the mode for generating predictive motion vectors using pixels 1222 adjacent to the current block is implicit mode_2, Information on a mode of one of the inter-gamut modes is encoded, and in the image decoding process, the predictive motion vector can be generated using one of the implicit mode_1 and the implicit mode_2 referring to the mode information.

(3) Selection of mode

There may be various criteria for the predicting unit 910 to select one of the above-described explicit mode and implicit mode.

Since the explicit mode selects one of a plurality of predicted motion vector candidates, it is possible to select a predicted motion vector more similar to the motion vector of the current block. Instead, it may encode information indicating one of a plurality of predicted motion vector candidates, resulting in greater overhead than the implicit mode. Therefore, it is appropriate to encode a motion vector in the explicit mode in the case of a large-size encoding unit. This is because a probability that an error occurs when a large-sized coding unit is incorrectly predicted from a motion vector is smaller than a small-sized coding unit, and the number of times overhead occurs for each picture becomes small.

For example, when coding a uniformly divided picture with m 64x64 coding units in the explicit mode, the number of times of occurrence of overhead is m times, but a picture of the same size is uniformly divided into 4m 32x32 coding units When the divided pictures are coded in the explicit mode, the number of overhead occurrences is 4m.

Therefore, when the prediction unit 910 according to the present invention encodes the motion vector of the current block, one of the explicit mode and the implicit mode can be selected based on the size of the encoding unit.

In the image encoding and decoding method according to the present invention described above with reference to FIGS. 1 to 8, since the size of an encoding unit is represented by depth, the predictor 910 specifies a motion vector of the current block based on the depth of the current block. Mode or in an implicit mode. For example, in the case of inter prediction of a coding unit of depth 0 and depth 1, a motion vector of a coding unit is coded in the explicit mode, and in the case of inter prediction of coding units of depth 2 or more, coding can be performed in an implicit mode.

According to another embodiment of the present invention, the predicting unit 910 can select the explicit mode or the implicit mode in units of pictures or slices. Since the picture characteristics are different for each picture or slice unit, a clear mode or an implicit mode can be selected in units of pictures or slices considering this. It is possible to predictively encode motion vectors of coding units included in the current picture or slice by selecting an optimal mode from the explicit mode and the implicit mode considering the R-D cost.

For example, if motion vectors of coding units included in a picture or a slice can be accurately predicted without using the explicit mode, motion vectors of all coding units included in a picture or slice can be predictively encoded in an implicit mode.

According to another embodiment of the present invention, the predicting unit 910 may select either the explicit mode or the implicit mode depending on whether the current block is coded in the skip mode. The skip mode refers to an encoding mode in which only flag information indicating that the current block is coded in the skip mode is encoded, and pixel values are not encoded.

The skip mode is a mode in which the prediction block generated by motion compensation using the predicted motion vector as a motion vector of the current block is very similar to the current block and thus the pixel value of the current block is not encoded. Accordingly, as the predictive motion vector is generated similar to the motion vector of the current block, the probability of encoding the current block in the skip mode increases. Therefore, the block to be coded in the skip mode can be encoded in the explicit mode.

Referring again to FIG. 9, when one of the explicit mode and the implicit mode is selected in the predicting unit 910 and the predicted motion vector is determined according to the selected mode, the first encoding unit 920 and the second encoding unit 930 Information on a coding mode and a motion vector are encoded.

First, the first encoder 920 encodes information on a predicted motion vector of a current block. If the prediction unit 910 selects to encode the motion vector of the current block in the explicit mode, information indicating that the predictive motion vector has been generated in the explicit mode and information indicating which of the plurality of predicted motion vector candidates are to be predicted And information indicating whether the motion vector is used as a motion vector is encoded.

On the other hand, if the prediction unit 910 selects to encode the motion vector of the current block in the implicit mode, information indicating that the motion vector of the current block is generated in the implicit mode is encoded. In other words, information indicating that a predictive motion vector of the current block is generated using a block or pixel adjacent to the current block is encoded. If there are more than two implicit modes, it may be possible to encode information indicating which of the implicit modes is used to generate the predictive motion vector of the current block.

The second encoder 930 encodes the motion vector of the current block based on the predicted motion vector determined by the predictor 910. A difference vector is generated by subtracting the predicted motion vector generated by the predictor 910 from the motion vector of the current block generated as a result of motion compensation. Then, information about the difference vector is encoded.

13 shows an apparatus for decoding a motion vector according to an embodiment of the present invention.

An apparatus for decoding a motion vector included in the image encoding apparatus 200 described above with reference to FIG. 2 or the image encoding unit 500 described with reference to FIG. 5 is illustrated in detail. 13, a motion vector decoding apparatus 1300 according to an embodiment of the present invention includes a first decoding unit 1310, a second decoding unit 1320, a predicting unit 1330, and a motion vector restoring unit 1340 ).

The first decoding unit 1310 decodes information on the predicted motion vector of the current block included in the bitstream. And decodes information indicating whether the predicted motion vector of the current block is coded in the explicit mode or the implicit mode. When the predictive motion vector of the current block is coded in the explicit mode, information indicating one predictive motion vector used as the predictive motion vector of the current block among the plurality of predictive motion vector candidates is also decoded. Also, when the predictive motion vector of the current block is coded in the implicit mode, information indicating which predictive motion vector of the current block is encoded in which of the plurality of implicit modes is also decoded.

The second decoding unit 1310 decodes the difference vector between the motion vector and the predicted motion vector of the current block included in the bitstream.

The predicting unit 1330 generates a predicted motion vector of the current block based on the information on the predicted motion vector of the current block decoded by the first decoding unit 1310. [

When information on the predictive motion vector of the current block coded in the explicit mode is decoded, a predictive motion vector of one of the predictive motion vector candidates described above with reference to Figs. 10A and 10B and 11A to 11C is generated, Is used as a vector.

When information on a predictive motion vector of a current block coded in an implicit mode is decoded, a predictive motion vector of the current block is generated using a block or pixel included in a previously coded area adjacent to the current block. A median of motion vectors of blocks adjacent to the current block is generated as a predictive motion vector of the current block or a reference picture is retrieved using pixels adjacent to the current block to generate a predictive motion vector of the current block.

The motion vector restoring unit 1340 restores the motion vector of the current block by adding the predictive motion vector generated by the predicting unit 1330 and the difference vector decoded by the second decoding unit 320. [ The restored motion vector is used for motion compensation of the current block.

14 is a flowchart illustrating a method of coding a motion vector according to an embodiment of the present invention.

Referring to FIG. 14, in step 1410, a motion vector coding apparatus according to an exemplary embodiment of the present invention selects one of an explicit mode and an implicit mode as a mode for encoding information on a predictive motion vector.

The explicit mode is a mode for coding information indicating a predicted motion vector candidate of at least one predicted motion vector candidate as information for a predicted motion vector, and the implied mode is a mode for previously And information indicating that a predictive motion vector should be generated based on the block or pixel included in the encoded region. Detailed descriptions have been given above with reference to Figs. 10A, 10B, 11A to 11C and 12. [

The mode can be selected based on the size of the current block, that is, the depth of the current block, or the mode can be selected in the current picture or the current slice unit including the current block. In addition, the mode may be selected depending on whether or not the current block is coded in the skip mode.

In step 1420, the motion vector coding apparatus determines a predicted motion vector according to the mode selected in step 1410. [ The predictive motion vector of the current block is determined based on the explicit mode or the implicit mode selected in step 1410. A predictive motion vector candidate of one of at least one predictive motion vector candidate is determined as a predictive motion vector of a current block according to the explicit mode or a predictive motion vector of a current block is determined based on a block or a pixel adjacent to the current block according to an implicit mode .

In step 1430, the motion vector coding apparatus encodes the information on the predicted motion vector determined in step 1420. In the explicit mode, information indicating that the predictive motion vector of the current block indicates one predictive motion vector of at least one predictive motion vector and information indicating that the information about the predictive motion vector of the current block is encoded according to the explicit mode is encoded . In the case of the implicit mode, information indicating that a predictive motion vector of the current block is generated based on a block or pixel included in a previously encoded area adjacent to the current block is encoded. If there are a plurality of implicit modes, information indicating one of the implicit modes can also be encoded.

In step 1440, the motion vector coding apparatus codes the difference vector generated by subtracting the predicted motion vector determined in step 1420 from the motion vector of the current block.

15 is a flowchart illustrating a method of decoding a motion vector according to an embodiment of the present invention.

Referring to FIG. 15, in step 1510, a motion vector decoding apparatus according to an embodiment of the present invention decodes information on a predicted motion vector of a current block included in a bitstream. And decodes the information on the mode used to encode the predictive motion vector of the current block in the explicit mode and the ambiguous mode.

In the explicit mode, information indicating that the predicted motion vector of the current block is coded according to the explicit mode and information on one predicted motion vector candidate of the at least one predicted motion vector candidate are decoded. Further, in the case of the implicit mode, information indicating that the predicted motion vector of the current block is generated based on the block or pixel included in the previously decoded area adjacent to the current block is decoded. If there is a plurality of implicit modes, information indicating one implicit mode of the plurality of implicit modes can also be decoded together.

In step 1520, the motion vector decoding apparatus decodes information on difference vectors. The difference vector is a vector for the difference between the predicted motion vector of the current block and the motion vector of the current block.

In step 1530, the motion vector decoding apparatus generates a predicted motion vector of the current block based on the information on the predicted motion vector decoded in step 1510. The predictive motion vector of the current block is generated according to the explicit mode or the implicit mode. A predictive motion vector of at least one predictive motion vector candidate is selected or a predictive motion vector of a current block is generated using a block or pixel included in a previously decoded area adjacent to the current block.

In operation 1540, the motion vector encoding apparatus reconstructs the motion vector of the current block by adding the difference vector decoded in operation 1520 and the motion vector generated in operation 1530.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but, on the contrary, Modification is possible. Accordingly, the spirit of the present invention should be understood only in accordance with the following claims, and all of the equivalent or equivalent variations will fall within the scope of the present invention. In addition, the system according to the present invention can be embodied as computer-readable codes on a computer-readable recording medium.

For example, the image encoding apparatus, the image decoding apparatus, the image encoding unit, the image decoding unit, the motion vector encoding apparatus, and the motion vector decoding apparatus according to the exemplary embodiments of the present invention are shown in FIGS. 1, 2, 4, 5, 9, A bus coupled to each unit of the apparatus as shown at 13, and at least one processor coupled to the bus. It may also include a memory coupled to the bus for storing instructions, received messages or generated messages, and coupled to the at least one processor for performing the instructions as described above.

In addition, the computer-readable recording medium includes all kinds of recording apparatuses in which data that can be read by a computer system is stored. Examples of the recording medium include ROM, RAM, CD-ROM, magnetic tape, floppy disk, optical data storage, and the like. The computer-readable recording medium may also be distributed over a networked computer system so that computer readable code can be stored and executed in a distributed manner.

Claims (4)

In the image decoding apparatus,
Determines a predicted motion vector candidate from the motion vectors of neighboring blocks of the current block if the current block's prediction mode is the inter prediction mode, A predictor for determining a predicted motion vector of the current block; And
And a motion vector restoring unit for obtaining a motion vector of the current block based on the predictive motion vector and the difference vector obtained from the bitstream,
Wherein the neighboring blocks are blocks located outside the current block, the first block located at the lower left of the current block, the second block located at the upper side of the first block, the third block located at the upper right side of the current block, A fourth block located on the left side of the third block and a fifth block located on the upper left side of the current block,
The image is divided into a plurality of maximum coding units according to the maximum coding unit size information, the maximum coding unit is hierarchically divided into one or more coding units having a depth, and the current depth is (k + 1) Wherein the encoding unit of the current depth (k + 1) is one of the square data units divided from the k-depth encoding unit. The method according to claim 1,
The predicted motion vector candidate is
And a motion vector of a block in the same position of a reference picture at the same position as the current block of the current picture. 3. The method of claim 2,
The predicting unit
And scales the motion vector of the block at the same position based on the temporal distance between the reference picture and the current picture. delete

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