WO2011053054A9 - Method and apparatus for motion vector encoding/decoding using a motion vector resolution limitation, and image encoding/decoding method and apparatus using same - Google Patents

Abstract

One embodiment of the present invention relates to a method and apparatus for motion vector encoding/decoding using a motion vector resolution limitation, and to an image encoding/decoding method and apparatus using same. The embodiment of the present invention provides a motion vector encoding method, comprising: calculating encoding costs for each limitation level of a motion vector resolution which is limited by levels; selecting a limitation level of the motion vector resolution using the encoding costs calculated for each limitation level; and outputting motion vector encoded data obtained by encoding the motion vector determined by the selected limitation level of the motion vector resolution, and resolution limitation index data obtained by encoding a resolution limitation index for indicating the selected limitation level of the motion vector resolution. According to the embodiment of the present invention, the resolution of the motion vector is adaptively limited to determine and encode a motion vector, thereby improving compression efficiency.

Description

Motion vector encoding / decoding method and apparatus using motion vector resolution limitation and image encoding / decoding method using same

The present invention relates to a motion vector encoding / decoding method and apparatus using a motion vector resolution limitation, and an image encoding / decoding method and apparatus using the same. More particularly, the present invention relates to a method and an apparatus for improving compression efficiency by determining and encoding a motion vector by adaptively limiting the resolution of the motion vector in encoding an image.

The content described in this section merely provides background information on the embodiments of the present invention and does not necessarily constitute prior art.

H.264 / AVC is the standard for the most highly compressed video codecs among the standardized video coders and decodes to date. The H.264 / AVC standard includes intra prediction with directionality to improve compression efficiency, integer transform in 4x4 pixel units, and block mode with various sizes from 16x16 pixel size to 4x4 pixel size. Mode and a deblocking filter to predictively encode an image. In addition, the H.264 / AVC standard performs motion estimation by interpolating images up to 1/2 pixel unit and 1/4 pixel unit in order to find a more accurate motion vector.

However, as described above, in the H.264 / AVC standard, since motion vectors having various resolutions are determined and encoded by estimating motion at various resolutions such as 1/2 pixel unit and 1/4 pixel unit, 1/2 pixel unit, 1 Since a long code word is used to encode a motion vector having a resolution of 4/4 pixels, the bit amount for encoding a small motion vector is increased, resulting in an increase in the bit amount of the encoded bitstream, thereby increasing compression efficiency. There is a problem of this deterioration.

In order to solve the above-described problem, an embodiment of the present invention has a main object to improve compression efficiency by determining and encoding a motion vector by adaptively limiting the resolution of the motion vector.

In order to achieve the above object, an embodiment of the present invention provides an apparatus for encoding / decoding an image, wherein the motion vector of the image is determined and determined according to the limited step-by-step motion vector resolution in which the motion vector resolution is limited step by step. Generate a predictive image of the image by using a motion vector, subtract, transform, and quantize the image and the predictive image, and then encode the resultant to generate image coded data for each step, and calculate encoding cost of the image coded data for each step. Selects a restriction step of the motion vector resolution using the encoding cost of the image coded data according to the restriction step; image coded data encoded using the motion vector determined according to the motion vector resolution according to the selected restriction step, and the selected motion. Vector resolution Video encoder for encoding the display limitations index showing a step of outputting the display limitations index data; And decoding the motion vector encoded data extracted from the bitstream in accordance with the limitation of the motion vector resolution, which is obtained by decoding the resolution limit index data extracted from the bitstream, and converting and quantized from the bitstream. An image decoder for restoring an image by restoring a residual image, inverse quantization and inverse transform, and generating a prediction image of the image by using the restored motion vector, and adding the residual image and the prediction image to restore the image. It provides a video encoding / decoding apparatus comprising a.

In addition, an embodiment of the present invention to achieve another object of the present invention, in the apparatus for encoding an image, the motion vector resolution is determined and determined according to the motion vector resolution of the step-by-step limited motion vector resolution A predictor for generating a predictive image of the image using the motion vector; A subtractor configured to generate a residual image by subtracting the image and the predicted image; A converter and quantizer for transforming and quantizing the residual image; And encoding the transformed and quantized residual images to generate restriction image encoding data, calculating encoding cost of the restriction phase encoding image data, and selecting a restriction level of the motion vector resolution using the encoding cost of the restriction encoding image encoding data. And an encoder for generating a bitstream including image coded data encoded using the motion vector determined according to the motion vector resolution according to the selected limiting step and resolution limit index data indicating the limiting step of the selected motion vector resolution. A video encoding apparatus is provided.

In addition, according to an embodiment of the present invention to achieve another object of the present invention, in the apparatus for decoding an image, the bit according to the limitation step of the motion vector resolution to be recovered by decoding the resolution limit index data extracted from the bitstream A decoder which decodes motion vector encoded data extracted from the stream to reconstruct the motion vector, and decodes the encoded video extracted from the bitstream to reconstruct the transformed and quantized residual image; An inverse quantizer and an inverse converter that inverse quantizes and inverse transforms the transformed and quantized residual image to reconstruct the residual image; A predictor for generating a predicted image of the image by using the reconstructed motion vector; And an adder for reconstructing the image by adding the residual image and the predictive image.

In addition, to achieve another object of the present invention, an embodiment of the present invention, in the encoding device for a motion vector, encoding cost calculator for calculating the encoding cost according to the motion vector resolution of the step-by-step limited motion vector resolution ; A limiting resolution determiner which selects a limiting step of the motion vector resolution using the encoding cost calculated in the limiting step; And a motion information encoder for encoding the motion vector coded data in which the motion vector determined according to the limiting step of the selected motion vector resolution is encoded and the resolution limit index indicating the limiting step of the selected motion vector resolution to output resolution limit index data. A motion vector encoding apparatus is provided.

In addition, to achieve another object of the present invention, an embodiment of the present invention, in the apparatus for decoding a motion vector, a limitation for restoring the motion vector resolution limitation step by decoding the resolution limitation index data extracted from the bitstream Resolution restorer; And a motion vector reconstructor for reconstructing the motion vector by decoding the motion vector encoded data extracted from the bitstream according to the limiting step of the reconstructed motion vector resolution.

Further, in order to achieve another object of the present invention, an embodiment of the present invention, in the method for encoding / decoding an image, determines the motion vector of the image according to the limited step-by-step motion vector resolution in which the motion vector resolution is limited step by step. Generating a predicted image of the image by using the determined motion vector, subtracting, transforming, and quantizing the image and the predicted image, and encoding the same to generate image coded data for each step, and encoding the image coded data for each step. Calculates a cost, selects a restriction step of motion vector resolution using the encoding cost of the restriction-level image coded data, and encodes image coded data encoded using a motion vector determined according to the motion vector resolution according to the selected restriction step. And the selected movement The image encoding step by encoding the limited resolution index indicating a limiting step of the emitter which outputs a resolution of the display limitations index data; And decoding the motion vector encoded data extracted from the bitstream in accordance with the limitation of the motion vector resolution, which is obtained by decoding the resolution limit index data extracted from the bitstream, and converting and quantized from the bitstream. An image decoding step of restoring a residual image, inverse quantization and inverse transformation, and restoring the image, generating a predicted image of the image using the restored motion vector, and adding the residual image and the predicted image to restore the image It provides a video encoding / decoding method comprising a.

According to another aspect of the present invention, there is provided a method of encoding an image, the method comprising: determining a motion vector of an image according to a step-by-step motion vector resolution in which the motion vector resolution is limited step by step; Generating a predicted image of the image using the determined motion vector; Generating a residual image by subtracting the image and the predictive image; Converting and quantizing the residual image; Encoding the transformed and quantized residual images to generate image coded data for each step; Calculating a coding cost of the image coded data for each step; Selecting a limiting step of the motion vector resolution using the encoding cost of the video encoding data for each step; And generating a bitstream including image coded data encoded using the motion vector determined according to the motion vector resolution according to the selected limiting step and resolution limit index data indicating the limiting step of the selected motion vector resolution. A video encoding method is provided.

In addition, an embodiment of the present invention to achieve another object of the present invention, in the method for decoding an image, the bit according to the limitation step of the motion vector resolution to be recovered by decoding the resolution limit index data extracted from the bitstream Reconstructing the motion vector by decoding the motion vector coded data extracted from the stream; Reconstructing the transformed and quantized residual image by decoding the image encoded data extracted from the bitstream; Inverse quantization and inverse transformation of the transformed and quantized residual image to reconstruct the residual image; Generating a predicted image of the image by using the reconstructed motion vector; And reconstructing the image by adding the residual image and the prediction image.

In addition, to achieve another object of the present invention, an embodiment of the present invention, in the method for encoding a motion vector of the image, calculating the encoding cost according to the motion vector resolution of the step-by-step limited motion vector resolution ; Selecting a limiting step of the motion vector resolution using the encoding cost calculated in the limiting step; And encoding the motion vector encoded data encoded with the motion vector determined according to the limiting step of the selected motion vector resolution and the resolution limit index indicating the limiting step of the selected motion vector resolution to output resolution limit index data. A motion vector encoding method is provided.

In addition, an embodiment of the present invention to achieve another object of the present invention, in the method for decoding a motion vector, the step of restoring the limit of the motion vector resolution by decoding the resolution limit index data extracted from the bitstream ; And reconstructing the motion vector by decoding the motion vector encoded data extracted from the bitstream according to the limiting step of the reconstructed motion vector resolution.

As described above, according to the exemplary embodiment of the present invention, the compression efficiency can be improved by adaptively limiting the resolution of the motion vector to determine and encode the motion vector.

1 is a block diagram schematically illustrating a video encoding apparatus according to an embodiment of the present invention;

2 is an exemplary view showing a state of determining a motion vector through motion estimation according to an embodiment of the present invention;

3 is a block diagram schematically illustrating an encoder according to an embodiment of the present invention;

4 is a block diagram schematically illustrating a motion vector encoding apparatus according to an embodiment of the present invention;

5 is an exemplary diagram for describing a process of estimating a motion vector having a motion vector resolution of a small pixel unit using template matching according to an embodiment of the present invention;

6 is an exemplary view for explaining a process of selecting a motion vector according to an embodiment of the present invention;

7 is a flowchart illustrating a motion vector encoding method according to an embodiment of the present invention;

8 is a flowchart illustrating an example of implementing a motion vector encoding method according to an embodiment of the present invention;

9 is a flowchart illustrating a video encoding method according to an embodiment of the present invention;

10 is a flowchart for explaining another example of implementing an image encoding method according to an embodiment of the present invention;

11 is a block diagram schematically illustrating an image decoding apparatus according to an embodiment of the present invention;

12 is a block diagram schematically illustrating a decoder according to an embodiment of the present invention;

13 is a block diagram schematically illustrating a motion vector decoding apparatus according to an embodiment of the present invention;

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

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

Hereinafter, some embodiments of the present invention will be described in detail through exemplary drawings. In adding reference numerals to the components of each drawing, it should be noted that the same reference numerals are assigned to the same components as much as possible even though they are shown in different drawings. In addition, in describing the present invention, when it is determined that the detailed description of the related well-known configuration or function may obscure the gist of the present invention, the detailed description thereof will be omitted.

In addition, in describing the component of this invention, terms, such as 1st, 2nd, A, B, (a), (b), can be used. These terms are only for distinguishing the components from other components, and the nature, order or order of the components are not limited by the terms. If a component is described as being "connected", "coupled" or "connected" to another component, that component may be directly connected to or connected to that other component, but there may be another configuration between each component. It is to be understood that the elements may be "connected", "coupled" or "connected".

The motion vector encoding apparatus (Motion Vector Encoding Apparatus), the motion vector decoding apparatus (Motion Vector Decoding Apparatus), the video encoding apparatus (Video Encoding Apparatus), and the video decoding apparatus (Video Decoding Apparatus) will be described later. Computer), Notebook Computer, Personal Digital Assistant (PDA), Portable Multimedia Player (PMP), PlayStation Portable (PSP), Wireless Communication Terminal (Wireless Communication Terminal), Smartphone ( It may be a user terminal such as a smart phone) or a TV, or a server terminal such as an application server or a service server, and may encode, decode, encode, or decode an image, a communication device such as a communication modem for communicating with various devices or a wired / wireless communication network. Various programs and data for predicting inter or intra It may mean a variety of devices including a memory for storing, a microprocessor for executing and controlling a program.

In addition, the motion vector or the image encoded in the bitstream by the motion vector encoding apparatus or the image encoding apparatus is real time or non-real time through a wired or wireless communication network such as the Internet, a local area wireless communication network, a wireless LAN network, a WiBro network, a mobile communication network, or the like. Is transmitted to the motion vector decoding apparatus or the image decoding apparatus through various communication interfaces such as a universal serial bus (USB), and the like, decoded by the motion vector decoding apparatus and restored as a motion vector or decoded by the image decoding apparatus to the image. Can be recycled.

In general, a moving picture is composed of a series of pictures, and each picture is divided into a predetermined area such as a block. When a region of an image is divided into blocks, the divided blocks are largely classified into intra blocks and inter blocks according to encoding methods. An intra block refers to a block that is encoded by using an intra prediction coding scheme. Intra prediction coding is performed by using pixels of blocks that have been previously encoded, decoded, and reconstructed in a current picture that performs current encoding. A prediction block is generated by predicting pixels of a block, and a difference value with pixels of the current block is encoded. An inter block refers to a block that is encoded using inter prediction coding. Inter prediction coding generates a prediction block by predicting a current block in a current picture by referring to one or more past pictures or future pictures, and then generates a current block. This is a method of encoding the difference value with. Here, a picture referred to for encoding or decoding the current picture is referred to as a reference picture.

1 is a block diagram schematically illustrating a video encoding apparatus according to an embodiment of the present invention.

The image encoding apparatus 100 according to an embodiment of the present invention is an apparatus for encoding an image, and includes a predictor 110, a subtractor 120, a transformer and quantizer 130, and an encoder. The encoder may include an encoder 140, an inverse quantizer and an inverse transformer 150, an adder 160, and a reference picture memory 170.

The predictor 110 determines a motion vector of the image according to the limited step-by-step motion vector resolution in which the motion vector resolution is limited in stages, and uses the determined motion vector to predict the image. Create That is, the motion vector and the reference frame index of the current block are estimated by estimating the motion of a block to be encoded in the predictor 110 input image (hereinafter referred to as a current block). Determining the motion information (Motion Information) including, and by using the determined motion information of the current block to compensate for the motion of the current block to generate a prediction block of the current block.

In addition, the predictor 110 further estimates a motion vector having a motion vector resolution of a pixel unit larger than the minimum motion vector resolution according to the limitation of the motion vector resolution selected by the encoder 140, and predicts the motion vector using the estimated motion vector. An image can be generated. In this case, the predictor 110 may estimate a motion vector having a smaller motion unit resolution by using template matching (TM). Here, template matching refers to a method of estimating a motion vector of a current block by using pixels that are already encoded, decoded, and reconstructed among neighboring pixels (or adjacent pixels among neighboring pixels) of a current block to be encoded. A method of additionally estimating a motion vector using template matching will be described in detail later with reference to FIGS. 5 and 6.

In addition, the process of determining the motion information in units of blocks of the predictor 110 and generating a prediction block is performed by a coding unit (eg, a block, a slice, a picture, and a picture group (GOP). Picture), etc., and an image obtained by collecting each prediction block generated by performing the coding unit may be generated as a prediction image. For example, when the coding unit is a slice, the predictor 110 determines a motion vector by estimating the motion of each block in the slice, and generates a prediction image by collecting the prediction blocks generated using the motion vector in units of slices. can do. Therefore, in an embodiment of the present invention, the input image may be an image (eg, an image corresponding to an arbitrary slice in an arbitrary picture) for a predetermined coding unit constituting a video, and the prediction image may be an input image. It may be an image (eg, a slice image in which prediction blocks are collected) for a predetermined coding unit including prediction blocks generated by predicting blocks in the block.

In addition, the predicted image generated by the predictor 110 may be generated according to the motion vector resolution for each step. That is, the predictor 110 determines a motion vector for each block in the input image according to the motion vector resolution for each step, generates a prediction block using the prediction vector, and generates a prediction image by collecting the generated prediction blocks. As many as the number of limiting steps of the vector resolution may be generated. In addition, when a motion vector having a motion vector resolution of a pixel unit smaller than the minimum motion vector resolution according to the selected motion vector resolution is further estimated, one prediction image may be generated for an image of a coding unit.

The subtractor 120 subtracts the input image and the prediction image to generate a residual image. Here, the residual image is an image generated by subtracting an input image and a prediction image to be encoded, and means an image including a residual signal that is a difference between a pixel of the input image and a pixel of the prediction image. In addition, since the predicted image generated by the predictor 110 is generated as many as the number of limiting steps of the motion vector resolution, the residual image generated by the subtractor 120 may be generated as many as the number of limiting steps of the motion vector resolution. When a prediction image is generated according to the estimated motion vector, a residual image of the prediction image may be generated.

The converter and quantizer 130 transforms and quantizes the residual image. That is, the transformer and the quantizer 130 convert the residual signal of the residual image generated by the subtractor 120 into the frequency domain to generate a transformed residual image having a transform coefficient and convert the residual signal. The transform coefficients of the residual image are quantized to generate transformed and quantized residual images. In this case, as a transform method used, a method of transforming an image signal in a spatial domain into a frequency domain such as a Hadamard transform or a discrete cosine transform based integer transform is used. As the scheme, various quantization techniques such as Dead Zone Uniform Threshold Quantization (DZUTQ) or quantization weighted matrix (DZUTQ) may be used.

The encoder 140 encodes the transformed and quantized residual images to generate the limited-level image coded data, calculates the encoding cost of the limited-step image coded data, and uses the encoding cost of the limited-step image coded data to obtain the motion vector resolution. A restriction step is selected, and the encoded image data is encoded using a motion vector determined according to the motion vector resolution according to the selected restriction step. Here, the entropy encoding technique may be used as a technique for encoding the quantized transform coefficients by the encoder 140, but various encoding techniques may be used without being limited thereto. The encoder 140 will be described in detail with reference to FIGS. 2 and 3.

The inverse quantizer and inverse converter 150 inverse quantizes and inverse transforms the transformed and quantized residual image to reconstruct the residual image. That is, the inverse quantizer and the inverse transformer 150 inverse quantizes the transformed and quantized residual images transmitted from the transformer and the quantizer 130 to restore a residual image having a transform coefficient, and reconstructs the residual image having a transform coefficient. Inverse conversion restores a residual image having a residual signal. In this case, the inverse quantizer and the inverse transformer 150 may reconstruct the residual image by performing the transformed and quantized method in the inverse of the transformer and the quantizer 130. In addition, the inverse quantizer and inverse transformer 150 inversely quantizes and inverse transforms all the transformed and quantized residual images transmitted from the transformer and quantizer 130, but limits the motion vector resolution selected by the encoder 140. Only the residual image according to the limitation of the motion vector resolution may be reconstructed by performing inverse quantization and inverse transformation on the residual image of the predicted image generated using the motion vector determined according to the step, and transforming only the residual image.

The adder 160 reconstructs the input image by adding the residual image reconstructed by the inverse quantizer and the inverse transformer 150 and the predictive image generated by the predictor 110. The reference picture memory 170 stores a reference picture in which reconstructed input pictures are accumulated by picture units, and the stored reference pictures may be used by the predictor 110 to predict the next input picture or the next picture.

Although not shown in FIG. 1, the image encoding apparatus 100 according to an exemplary embodiment of the present invention may add an intra predictor, a deblocking filter, or the like for intra prediction in the predictor 110. It can be included as. In this case, the subtractor 120 may generate a residual image by subtracting the input image and the prediction image generated by the intra predictor, and the transformer and quantizer 130 and the inverse quantizer and inverse transformer 150 may generate the residual image. Transform and quantization for and inverse transform and inverse quantization on the transformed and quantized residual image may be further performed. In addition, the encoder 140 may generate image encoded data by encoding the transformed and quantized residual image, which is included in the bitstream. In addition, the deblocking filter deblocks the input image to be reconstructed. Here, the deblocking filtering refers to an operation of reducing block distortion generated by encoding an image in block units, and applying a deblocking filter to a block boundary and a macroblock boundary, or applying a deblocking filter only to a macroblock boundary or a deblocking filter. You can optionally use one of the methods that does not use.

2 is an exemplary view showing a state of determining a motion vector through motion estimation according to an embodiment of the present invention.

The predictor 110 finds a reference block that is the block most similar to the current block among predetermined search regions within several reference pictures that can be used to determine a motion vector of the current block, and finds a reference picture index and a reference block representing the reference picture. The motion of the current block is estimated by acquiring the indicated motion vector as motion information. As described above, a method of determining a motion vector may be represented by Equation 1 and Equation 2.

[Equation 1]

[Revision under Rule 91 08.11.2011]

[Equation 2]

[Revision under Rule 91 08.11.2011]

In Equation 1, MV represents a motion vector of a current block, and the position of the motion vector may exist anywhere in several reference pictures. org represents the original current block, and ref _MV represents a reference block indicated by MV . SAD ( org , ref _MV ) represents a function that calculates the sum of absolute values for the difference of pixels between org and ref _MV , λ represents a Lagrange Multiplier, and PMV represents a predictive motion vector. Ref_idx represents a reference picture index, which is an index representing a reference picture, and Rate ( MV , PMV , ref_idx ) represents a function for calculating the difference between MV and PMV and the amount of bits required to encode ref_idx . Mcost ( MV ) represents an encoding cost required for encoding motion information according to MV. In Equation 2, MV ^* represents a motion vector of the current block that is finally determined, and S _MV represents a predetermined motion search region.

Accordingly, the predictor 110 may determine a predetermined motion search region of several reference pictures.S                  _MV                  The coding cost for each MV that can be considered within is calculated using Equation 1, and the MV having the smallest coding cost can be found using Equation 2 and determined as the motion vector of the current block. In Equation 1, for example, the encoding cost is calculated as the rate-distortion cost, but the encoding cost is not necessarily calculated as the rate-distortion cost and may be calculated in various other ways.

In calculating the encoding cost for encoding the current block, not only the motion vector but also the block mode of the current block is affected. A method of determining the block mode may be represented by Equations 3 and 4 below.

[Equation 3]

[Revision under Rule 91 08.11.2011]

[Equation 4]

In Equation 3, org, λ, PMV, ref_idx each represent the same as described above through Equation 1, i represents a block mode index for identifying an interblock _mode , and S _mode from a block of 16x16 pixel size Rec _i represents a reconstructed block which is recovered by encoding and decoding the current block using block mode i , and SSD ( org , rec _i ) represents org and rec _i. represents a function for calculating a pixel sum of the square error between, Coeff _i represents the quantized transform coefficients produced by the transform, and both the residual block of the current block by using the block mode, _{i, Rate (MV i, PMV} , ref_idx , Coeff _i) is and for coding the current block by using the block mode, i, calculating the bit rate required for encoding the MV and the difference value, ref_idx, and the quantized transform coefficient between PMV Denotes a function for, rdcost (i) represents the coding cost of encoding the current block by using the block mode, i. In Equation 4, i ^* is an index indicating the block mode of the current block that is finally determined.

Accordingly, the predictor 110 calculates encoding costs for several interblock modes by using Equation 3, and finds i ^* , which is an index indicating a block mode having a minimum encoding cost, by using Equation 4. It can be determined as the block mode of the final current block. In Equation 3, the encoding cost is calculated as a rate-distortion cost, but the encoding cost is not necessarily calculated as the rate-distortion cost as shown in Equation 3 and may be calculated in various other ways.

In FIG. 1, the predictor 110 calculates the encoding cost, but the present invention is not limited thereto. The encoder 140 calculates the encoding cost and transfers the calculated encoding cost to the predictor 110 so that the predictor 110 may calculate the encoding cost. The motion vector may be determined.

Meanwhile, the motion vector obtained through Equation 2 is predictively encoded, and the predictor 110 or the encoder 140 encodes a differential motion vector which is a difference value between the motion vector and its predicted motion vector as shown in Equation 5.

[Equation 5]

In this case, in a conventional video compression standard such as H.264 / AVC, motion vectors are obtained by performing motion estimation at resolutions of integer pixel units, 1/2 pixel units, and 1/4 pixel units, and differential motion vectors of the obtained motion vectors are obtained. Is encoded using a code table to which a bit string for each multiple of quarter pixels as shown in Table 1 is assigned.

Table 1

As can be seen from Table 1, in the conventional compression standard, long codewords are used to encode small motion vectors to encode all motion vectors of various resolutions, and consequently, motions generated by encoding motion vectors. The size of the vector coded data increases, and the compression efficiency decreases. For example, referring to Table 1, when the differential motion vector is (3,2), in order to encode '3', the bit string '00011000' having a code number of '23' is used and '2' is used. To be encoded, a bit string '0001000' having a code number of '15' is used. Long codewords are used to encode a motion vector having a small size, such as a codeword for encoding a motion vector having a resolution of 1/2 pixel and a resolution of a quarter pixel and a motion of a resolution of an integer pixel. This is because a codeword for encoding a vector is used together.

In order to solve this problem, an embodiment of the present invention restricts the motion vector resolution stepwise to perform motion estimation, motion compensation, encoding of the residual image, and encoding of the motion vector at the limited motion vector resolution of each step. The cost is calculated to select a limit of motion vector resolution having a minimum encoding cost, and a bitstream including image encoded data and motion vector encoded data encoded at the selected motion vector resolution of the selected limit level is generated.

3 is a block diagram schematically illustrating an encoder according to an embodiment of the present invention.

The encoder 140 according to an embodiment of the present invention may include a predicted residual encoder 310 and a motion vector encoder 320.

The predictive residual encoder 310 encodes the transformed and quantized residual image to generate image coded data for each step. That is, the predictive residual encoder 310 encodes the residual image transformed and quantized by the transformer and the quantizer 130. The residual residual encoder 310 encodes the transformed and quantized residual image in the step of limiting the motion vector resolution. Generates video coded data.

The motion vector encoder 320 calculates an encoding cost of the image coded data for each step, selects a restriction step of the motion vector resolution using the encoding cost of the image coded data for each step, and according to the motion vector resolution according to the selected restriction step. The motion vector encoded data obtained by encoding the determined motion vector is output. That is, the motion vector encoder 320 receives various types of information transmitted from the predictor 110 and the predictive residual encoder 310 in the process of encoding the image coded data of each step of the limitation of the motion vector resolution generated by the predictive residual encoder 310. Calculate the encoding cost for encoding each image coded data, select the motion vector resolution limit step among the motion vector resolution limit steps, and determine according to the limit level of the selected motion vector resolution. The motion vector encoded data obtained by encoding the motion vector to be output is output. In this case, the motion vector encoder 320 encodes a motion vector that is already determined by the limitation step of each motion vector resolution and generates motion vector encoded data for each restriction step when calculating the encoding cost for each restriction step of the motion vector resolution. After selecting the limit of the vector resolution, the generated motion vector encoded data may be output without generating the motion vector encoded data again. The motion vector encoder 320 will be described in detail with reference to FIG. 4.

4 is a block diagram schematically illustrating a motion vector encoding apparatus according to an embodiment of the present invention.

The motion vector encoding apparatus according to an embodiment of the present invention may be implemented as the motion vector encoder 320 in the encoder 140 described above with reference to FIG. 3. Hereinafter, for convenience of description, the motion vector encoding apparatus according to an embodiment of the present invention is called a motion vector encoder 320.

The motion vector encoder 320 may include a coding cost calculator 410, a motion information encoder 430, and a limited resolution determiner 420.

The encoding cost calculator 410 calculates the encoding cost according to the motion vector resolution of the step-by-step limited motion vector resolution. That is, the encoding cost calculator 410 is required to encode a residual image which is a difference between the predicted image and the input image generated by using the motion vector including the motion vector and the reference picture index determined according to the motion vector resolution for each step. Calculate the cost.

Here, the motion vector resolution may include one or more of an integer pixel resolution, a 1/2 pixel resolution, a 1/4 pixel resolution, and a 1/8 pixel resolution, but is not limited thereto. It may also include a pixel-by-pixel resolution. In addition, the step of limiting the motion vector resolution refers to a group formed step by step in order of increasing motion vector resolution in a set of motion vector resolutions that can be used for motion estimation.

For example, assuming that the available motion vector resolution is the resolution in integer pixels, the resolution in 1/2 pixel, the resolution in 1/4 pixel, and the resolution in 1/8 pixel unit, as described above, The first limiting step is a group containing only resolution in integer pixel units, and the second limiting step of motion vector resolution is a group including resolution in integer pixel units and resolution in 1/2 pixel units, and motion vector resolution The third step of the group is a group including the resolution in integer pixel unit, the resolution in 1/2 pixel unit and the resolution in 1/4 pixel unit, and the fourth step of the motion vector resolution is the resolution in integer pixel unit, 1/2 It may be a group including a resolution in units of pixels, a resolution in units of 1/4 pixels and a resolution in units of 1/8 pixels.

Accordingly, in the above-described example, the encoding cost calculator 410 predicts and encodes the input image using the motion vector determined by estimating the motion at the resolution of the integer pixel unit included in the first limiting step of the motion vector resolution. An input image is calculated by using the motion vector determined by calculating the encoding cost required as the encoding cost of the first constraint step and estimating the motion at a resolution of 1/2 pixel unit, which is an integer included in the second constraint stage of the motion vector resolution. The coding cost required for predictive coding is calculated as the coding cost of the second limiting step, and the motion is estimated using the integer, 1/2, and 1/4 pixel resolutions included in the third limiting step of the motion vector resolution. The encoding cost required to predict-encode the input image using the determined motion vector is calculated as the encoding cost of the third limited step. Required for predictive encoding an input image using a motion vector determined by estimating the motion at resolutions of integers, 1/2, 1/4, and 1/8 pixels included in the fourth limiting step of the motion vector resolution. The encoding cost is calculated as the encoding cost of the fourth restriction stage.

In addition, the encoding cost calculator 410 may determine at least one of a motion vector for each block and a block mode according to the motion vector resolution for each step, and calculate an encoding cost using at least one of the determined motion vector and the determined block mode. For example, the encoding cost calculator 410 may calculate the encoding cost considering the motion vector and the block mode using Equation 6. cost ( k ) represents the encoding cost of each step.

[Equation 6]

In Equation 6, k represents a resolution limit index for identifying a limit step of motion vector resolution. In this case, the considered motion vector resolution is up to 1/2 ^k pixel units. Therefore, in the above example, k becomes 0, 1, 2, and 3, respectively, when the resolution limit index indicates the first to fourth limit steps of the motion vector resolution. N _MB denotes the number of blocks (macroblock or subblock in which a motion vector is determined) existing in a coding unit (eg, slice) in which a limiting step of motion vector resolution and a coding cost are respectively selected and calculated. Represents a block index (block index) for identifying each block, i ^* _m represents a block mode for the block in the coding unit. rdcost _{{ m, k }} ( i ^* _m ) is used to calculate the coding cost for encoding each block by using the block mode and the motion vector of each block in the coding unit determined according to the limitation of the motion vector resolution. Function. In this process, the N_MB value may have a positive integer value. When N_MB = 1, the N_MB value is a case where the limit level of the motion vector resolution is determined for every subblock.

 In addition, the encoding cost calculator 410 may calculate the encoding cost by encoding the motion vector using a different code table according to the motion vector resolution for each step. That is, the encoding cost calculator 410 may store another code table in advance for each step of limiting the motion vector resolution and use the same to encode a motion vector of the motion vector resolution for each step by step. Here, another code table for each step of limiting the motion vector resolution refers to a code table for encoding considering only the motion vector of the motion vector resolution within the limit step of each motion vector resolution.

Therefore, in the above-described example, as shown in Table 2, the code table for the first limiting step of the motion vector resolution is a code table for encoding considering only the motion vector having the resolution of the integer pixel unit, As shown in Table 3, the code table for the second limit step of the motion vector resolution is a code table for encoding by considering only the motion vector having the resolution of integer, 1/2 pixel unit. As shown in Table 4, the code table for the third limiting step is a code table for encoding by considering only motion vectors of resolutions of integer, 1/2, and 1/4 pixel units. The code table for the fourth constraint step, as exemplarily shown in Table 5, is a motion of resolution in integer, 1/2, 1/4, and 1/8 pixel units. Code table for encoding by considering only vectors.

TABLE 2

TABLE 3

Table 4

Table 5

Accordingly, according to an embodiment of the present invention, as described above, the code table for encoding the motion vector determined by the step of limiting the motion vector resolution is configured and used differently to be suitable for the step of limiting the motion vector resolution. The compression efficiency can be improved by encoding the vector efficiently.

The limited resolution determiner 420 selects a limited step of the motion vector resolution by using the encoding cost calculated in the limited step. In other words, the limited resolution determiner 420 compares the encoding costs of the limited stages calculated by the encoding cost calculator 410 with each other and selects the restriction of the motion vector resolution having the smallest encoding cost. Here, the limited resolution determiner 420 may select a limit step of the motion vector resolution for each coding unit including at least one of a block, a slice, a picture, and a picture group.

In this case, the limited resolution determiner 420 may calculate the motion vector resolution having the smallest encoding cost among the limited step coding costs calculated by summing the coding costs for all the blocks in the coding unit as shown in Equation 6 in the step of limiting the motion vector resolution. The restriction step can be selected in the same manner as in Equation 7.

[Equation 7]

In Equation 7, k denotes a resolution limit index, and k ^* denotes a resolution limit index for identifying a limit step of the motion vector resolution selected by the limit resolution determiner 420. The resolution limit index k ^* for identifying the limit level of the motion vector resolution selected by the limited resolution determiner 420 is included in the bitstream when encoded by the motion information encoder 430 and generated as the resolution limit index data. . In Equation 7, it is merely exemplary that k is represented by {0, 1, 2, 3}, and does not necessarily mean that the value of k should have only one value of {0, 1, 2, 3}. Therefore, k has an integer value of 0 or more and may have one or more values.

The motion information encoder 430 outputs motion vector encoded data obtained by encoding a motion vector determined according to a limitation step of the selected motion vector resolution. That is, when the motion vector encoder 430 selects the limit of the motion vector resolution by the limited resolution determiner 420, the motion vector coded data is generated by encoding in advance in the process of calculating the encoding cost by the encoding cost calculator 410. The motion vector encoded data obtained by encoding the motion vector determined according to the motion vector resolution of the limited step selected by the limited resolution determiner 420 is output. In this case, since the encoding cost and the motion vector resolution limiting step are calculated and selected for each predetermined coding unit such as a slice, the motion vector coded data output from the motion information encoder 430 is also determined for each block in the predetermined coding unit such as a slice. It may be generated motion vector encoded data. In addition, the motion vector encoded data may further include a reference picture index as well as a motion vector. In this case, the restriction information of the motion vector resolution is determined, and a unit for encoding the information may be not limited to a slice unit but may be a small subblock unit to a large frame and an entire sequence.

In this case, the motion information encoder 430 may output resolution restriction index data by encoding a resolution restriction index indicating a restriction level of the selected motion vector resolution. The resolution limit index data is additionally included in the bitstream, and used to identify the limiting step of the motion vector resolution in the motion vector decoding apparatus or the image decoding apparatus.

Hereinafter, a method of estimating a motion vector having a motion vector resolution smaller than a selected motion vector resolution using template matching and a pixel unit smaller than a motion vector having a selected motion vector resolution or a selected motion vector resolution will be described with reference to FIGS. 5 and 6. A method of selecting a motion vector having a resolution of a motion vector will be described.

5 is an exemplary diagram for describing a process of estimating a motion vector having a motion vector resolution of a small pixel unit using template matching according to an embodiment of the present invention.

As shown in FIG. 5, the predictor 110 is presently present in the reference picture at a motion vector resolution of a pixel unit smaller than the minimum motion vector resolution among the motion vector resolutions included in the motion vector resolution limiting step selected by the encoder 140. A reference block having an adjacent pixel most similar to the adjacent pixels of the block is found to obtain a motion vector indicating the reference block. In this case, the search region for estimating the motion by using template matching at a motion vector resolution of a small pixel unit may be limited to a peripheral region of the motion vector determined according to the limiting step of the selected motion vector resolution. Herein, the peripheral area of the motion vector may be an area that is equally or differently spaced apart by a predetermined number of pixels with respect to the pixel indicated by the motion vector.

6 is an exemplary diagram for describing a process of selecting a motion vector according to an embodiment of the present invention.

6A illustrates a process of calculating an encoding cost for a motion vector determined according to the limitation of the motion vector resolution selected by the encoder 140, and 6B illustrates a process of limiting the motion vector resolution selected by the encoder 140. A process of calculating a coding cost for a motion vector determined by using template matching at a motion vector resolution of a pixel unit smaller than the minimum motion vector resolution is shown. The coding costs calculated by the methods shown in 6A and 6B can be calculated using Equations 8 and 9, respectively.

[Equation 8]

[Equation 9]

In Equations 8 and 9, T _org ( i ) represents a current template representing adjacent pixels of the current block,

Denotes a reference template indicating adjacent pixels of a reference block indicated by the motion vector MV ^* determined according to the motion vector resolution selected by the limited resolution determiner 420, and N _T denotes a pixel of the pixel included in the current template and the reference template. Number,

Is an adjacent pixel of the reference block indicated by the motion vector MV ^* _T determined by using template matching at a motion vector resolution in pixels smaller than the minimum motion vector resolution according to the motion vector resolution selected by the limited resolution determiner 420. Represents a reference template to indicate. In Equations 8 and 9, the distortion cost is taken as an encoding cost, but the encoding cost is not necessarily limited thereto and may be calculated in various ways.

Since the motion vector having the small SAD among the SADs calculated using Equations 8 and 9 has better coding efficiency, the predictor 110 outputs the predicted block by compensating for the motion of the block using the corresponding motion vector. do. In this case, the predictor 110 may select a motion vector for each block in the coding unit. Therefore, the predictor 110 may output a predicted block whose motion is compensated using the estimated motion vector only when the selected motion vector for each block is a motion vector additionally estimated using template matching. If the motion vector determined according to the limit of the motion vector resolution is selected, the prediction block is not additionally generated.

As described above with reference to FIGS. 5 and 6, for the motion vector estimated at the motion vector resolution of a small pixel unit, the image coded data encoded by using additional information or any motion vector for additionally encoding or identifying the bit is encoded. It is not necessary to encode information indicating whether the stream is included. This is because the image decoding apparatus may perform the same process as described with reference to FIGS. 5 and 6 in the same manner as the image encoding apparatus 100.

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

According to the motion vector encoding method according to the embodiment of the present invention, the motion vector encoder 320 calculates the encoding cost according to the motion vector resolution in which the motion vector resolution is limited step by step (S710), A step of limiting the motion vector resolution is selected using the encoding cost (S720), and motion vector encoded data encoded by the motion vector determined according to the limit of the selected motion vector resolution is output (S730).

Here, the motion vector resolution may include at least one of resolution in integer pixel units, resolution in 1/2 pixel units, resolution in 1/4 pixel units, and resolution in 1/8 pixel units.

In addition, the motion vector encoder 320 may further output resolution limit index data by encoding a resolution limit index indicating a limit step of the selected motion vector resolution.

In operation S710, the motion vector encoder 320 may determine at least one of a motion vector for each block and a block mode according to the motion vector resolution for each step, and calculate a coding cost using at least one of the determined motion vector and the determined block mode. The coding cost can be calculated by encoding the motion vector using a different code table according to the motion vector resolution for each step.

In operation S720, the motion vector encoder 320 may select a restriction step of the motion vector resolution for each coding unit including one or more of blocks, slices, pictures, and picture groups, and encode the smallest of the encoding costs calculated for each restriction step. The limiting step with cost can be selected as the limiting step of the motion vector resolution.

8 is a flowchart for explaining an example of implementing a motion vector encoding method according to an embodiment of the present invention.

In FIG. 8, the motion vector resolution that the motion vector encoder 320 can use to determine the motion vector is resolution in integer pixels, resolution in 1/2 pixel, resolution in 1/4 pixel, and 1/8 pixel. Assuming a resolution of and coding unit is a slice, a process of encoding a motion vector is illustrated.

The motion vector encoder 320 calculates cost (0), which is an encoding cost when encoding an image, by considering only a motion vector having a motion vector resolution of an integer pixel unit as a first limiting step of the motion vector resolution (S810). That is, the motion vector encoder 320 performs motion estimation on the motion vector resolution in integer pixel units by using Equation 1 and Equation 2 for all blocks in the slice in the input image. A motion vector is determined, and a block mode according to the motion vector determined by the motion vector resolution in units of integer pixels is determined using Equation 3 and Equation 4. In addition, the motion vector encoder 320 predictively encodes each block according to the determined motion vector and the block mode to generate image coded data for each block of which the motion vector resolution is limited in units of integer pixels. The encoding cost for each image encoded data is calculated using the, and the encoding cost for all blocks in the slice is summed to calculate the encoding cost cost (0) for the first limiting step of the motion vector resolution as shown in Equation (6). At this time, when the motion vector encoder 320 predictively encodes each block to generate image coded data, the motion vector encoder 320 also predicts and encodes a motion vector having a motion vector resolution of an integer pixel unit. Encode using a code table.

In addition, the motion vector encoder 320 calculates cost (1), which is an encoding cost when encoding an image, by considering only a motion vector having a motion vector resolution of an integer and 1/2 pixel unit as a second limiting step of the motion vector resolution. (S820). That is, the motion vector encoder 320 performs motion estimation on the motion vector resolutions of integer pixel units and 1/2 pixel units using Equation 1 and Equation 2 for all blocks in the slice in the input image. A motion vector having a motion vector resolution of a unit or 1/2 pixel unit is determined, and a block mode according to a motion vector determined by an integer pixel unit or a motion vector resolution of a unit of 1/2 pixel using Equations 3 and 4 Determine. In addition, the motion vector encoder 320 predictively encodes each block according to the determined motion vector and the block mode, and generates image coded data for each block of which the motion vector resolution is limited only in integer pixel units and 1/2 pixel units. Equation 3 and Equation 4 are used to calculate the encoding cost for each piece of image encoded data and add the encoding cost for all the blocks in the slice to calculate the encoding cost cost for the second limited step of motion vector resolution as shown in Equation 6. Calculate 1). In this case, when the motion vector encoder 320 predictively encodes each block to generate image coded data, the motion vector encoder 320 also predicts and encodes a motion vector having a motion vector resolution of an integer pixel unit or 1/2 pixel unit, as shown in Table 3 below. Encode using the code table for the second constraint step of.

In addition, the motion vector encoder 320 is a third limitation step of the motion vector resolution, which is a cost cost of encoding an image by considering only a motion vector having a motion vector resolution of integer, 1/2, and 1/4 pixel units. 2) is calculated (S830). That is, the motion vector encoder 320 moves all the blocks in the slice in the input image using the equation 1 and the equation 2 at the motion vector resolution of integer pixel unit, 1/2 pixel unit and 1/4 pixel unit. By performing the estimation, a motion vector having a motion vector resolution of an integer pixel unit, 1/2 pixel unit, or 1/4 pixel unit is determined, and an integer pixel unit, 1/2 pixel unit or A block mode according to a motion vector determined by a motion vector resolution of a quarter pixel unit is determined. In addition, the motion vector encoder 320 predicts and encodes each block according to the determined motion vector and the block mode, so that an image of each block whose motion vector resolution is limited to an integer pixel unit, 1/2 pixel unit, and 1/4 pixel unit only. Generating encoded data, calculating encoding cost for each image encoded data using Equation 3 and Equation 4, summing the encoding cost for all blocks in the slice, and limiting the motion vector resolution as shown in Equation 6. Calculate the coding cost cost (2) for. At this time, when the motion vector encoder 320 predictively encodes each block to generate image coded data, the motion vector encoder 320 also predicts and encodes a motion vector having a motion vector resolution of integer pixel unit, 1/2 pixel unit, or 1/4 pixel unit. As shown in FIG. 4, encoding is performed using a code table for a third limit step of motion vector resolution.

In addition, the motion vector encoder 320 encodes an image by encoding only a motion vector having a motion vector resolution of integer, 1/2, 1/4, and 1/8 pixel units as a fourth limiting step of the motion vector resolution. The cost (3) is calculated (S840). That is, the motion vector encoder 320 uses equations 1 and 2 for all blocks in the slice in the input image to be integer pixel units, 1/2 pixel units, 1/4 pixel units, and 1/8 pixel units. By performing motion estimation at a motion vector resolution of, a motion vector having a motion vector resolution of integer pixel unit, 1/2 pixel unit, 1/4 pixel unit, or 1/8 pixel unit is determined. A block mode according to a motion vector determined by a motion vector resolution of an integer pixel unit, 1/2 pixel unit, 1/4 pixel unit, or 1/8 pixel unit is determined. In addition, the motion vector encoder 320 predictively encodes each block according to the determined motion vector and the block mode, and the motion vector resolution is increased only in integer pixel units, 1/2 pixel units, 1/4 pixel units, and 1/8 pixel units. Generate image encoding data for each limited block, calculate encoding cost for each image encoding data using equations (3) and (4), add the encoding cost for all blocks in the slice, and add the motion vector as shown in (6). The coding cost cost (3) for the fourth limiting step of resolution is calculated. In this case, when the motion vector encoder 320 predictively encodes each block to generate the image coded data, the motion vector resolution moves in the integer pixel unit, 1/2 pixel unit, 1/4 pixel unit, or 1/8 pixel unit. The vector is also predictively encoded using a code table for the fourth limited step of motion vector resolution, as shown in Table 5.

Thereafter, the motion vector encoder 320 selects a limit step of the motion vector resolution having the smallest cost () among cost (0), cost (1), cost (2), and cost (3) (S850). That is, the motion vector encoder 320 calculates a resolution limit index corresponding to a cost having a minimum value among cost (0), cost (1), cost (2), and cost (3) calculated in steps S810 to S840. Equation 7 is used to select.

If the limit of the motion vector resolution is selected, the motion vector encoder 320 encodes the motion vector and the resolution limit index determined according to the limit of the selected motion vector resolution (S860). That is, the motion vector encoder 320 encodes the motion vector determined according to the restriction of the motion vector resolution selected in step S850 among the motion vectors determined according to the restriction step of each motion vector resolution when calculating the encoding cost in steps S810 to S840. The encoded motion vector encoded data is outputted, and the resolution limited index representing the limited level of the motion vector resolution selected in step S850 is encoded to output the resolution limited index data. Such restriction index data may be inserted into a block header or a slice header of the bitstream. If the coding unit is a picture other than a slice, it will be inserted into the picture header.

Each step described above with reference to FIGS. 7 and 8 is not necessarily all performed, and some steps may be selectively omitted or added. In addition, the order of each step is not necessarily determined as shown, and the order of some or all of the steps may be changed or even performed in parallel. For example, in FIG. 8, steps S810 to S840 are illustrated and described as being sequentially performed, but steps S810 to S840 may be performed in a changed order or in parallel.

9 is a flowchart illustrating an image encoding method according to an embodiment of the present invention.

According to an image encoding method according to an embodiment of the present invention, the image encoding apparatus 100 determines a motion vector of an image according to a limited step-by-step motion vector resolution in which the motion vector resolution is limited step by step (S910), and determines the determined motion vector. Generate a predictive image of the image by using (S920), subtract the image and the predictive image to generate a residual image (S930), transform and quantize the residual image (S940), and encode the transformed and quantized residual image Generate the coded image of the restriction stage (S950), calculate the encoding cost of the image coded data of the restriction stage (S960), and select the restriction stage of the motion vector resolution using the encoding cost of the image encoding data of the restriction stage (S970). Image coded using the motion vector determined according to the motion vector resolution according to the selected restriction step A bitstream including the data stream is generated (S980).

In operation S980, the image encoding apparatus 100 estimates a motion vector having a motion vector resolution of a pixel unit smaller than the minimum motion vector resolution according to the limiting step of the selected motion vector resolution, and moves the estimated motion vector resolution of a small pixel unit. The image may be predictively encoded using a vector to generate a bitstream including encoded image encoded data. In this case, the image encoding apparatus 100 may estimate a motion vector having a motion vector resolution of a small pixel unit by using template matching, and predictively encode an image according to a motion vector determined according to a limitation step of the selected motion vector resolution. A bitstream including image encoded data encoded using a motion vector having a small encoding cost among encoding costs required to predict and encode an image according to a motion vector having a motion vector resolution of a small pixel. Can be generated.

10 is a flowchart for explaining another example of implementing an image encoding method according to an embodiment of the present invention.

Steps S1010 to S1070 are the same as or similar to steps S910 to S970 described above with reference to FIG. 9, and thus a detailed description thereof will be omitted.

After the step S1070, the image encoding apparatus 100 determines according to the motion vector resolution of the pixel unit smaller than the minimum motion vector resolution among the motion vector resolutions within the limit of the motion vector resolution selected in step S1070 and the limit of the selected motion vector resolution. A search region for motion estimation is determined based on the motion vector, in step S1080. For example, in step S1070, if a limiting step of motion vector resolution including a motion vector resolution in integer pixel units and 1/2 pixel units is selected, the minimum motion vector resolution is a motion vector resolution in units of 1/2 pixel, which is the minimum. do. In this case, the image encoding apparatus 100 minimizes the motion vector resolution in the 1/4 pixel unit and the motion vector resolution in the 1/8 pixel unit that is smaller than the motion vector resolution in the 1/2 pixel unit. The resolution is determined as the motion vector resolution in pixels smaller than the vector resolution. Further, in step S1070, the step of limiting the motion vector resolution including the motion vector resolution of the integer pixel unit and the half pixel unit is selected. Therefore, additional motion estimation is performed to the peripheral region of the motion vector determined when the encoding cost is calculated in step S1060. Set to limit the search area.

Also, the image encoding apparatus 100 determines a motion vector having a smaller motion unit resolution by performing motion estimation using template matching at a motion vector resolution of a smaller pixel unit in the search area determined in operation S1080 (S1090). ). That is, as described above with reference to FIG. 5, the image encoding apparatus 100 moves a motion of each block in a slice at a motion vector resolution of 1/4 pixel unit and a motion vector resolution of 1/8 pixel unit using template matching. Is further estimated to determine a motion vector with a motion vector resolution of 1/4 pixel unit or with a motion vector resolution of 1/8 pixel unit. In this case, as described above with reference to FIG. 6, the image encoding apparatus 100 uses the motion vector determined according to the limit of the motion vector resolution selected in step S1070 and the template matching in step S1090 to a motion vector resolution in small pixel units. A bitstream including image coded data encoded using a motion vector having good encoding efficiency among the motion vectors determined by performing motion estimation may be output.

11 is a block diagram schematically illustrating an image decoding apparatus according to an embodiment of the present invention.

The image decoding apparatus 1100 according to an embodiment of the present invention may include a decoder 1110, an inverse quantizer and an inverse converter 1120, a predictor 1130, an adder 1140, and a reference picture memory 1150. It can be configured to include.

The decoder 1110 reconstructs the motion vector by decoding motion vector encoded data extracted from the bitstream according to the motion vector resolution limiting step, which is obtained by decoding the resolution limit index data extracted from the bitstream, and extracting from the bitstream. The transformed and quantized residual images are reconstructed by decoding the encoded image encoded data. That is, the decoder 1110 extracts and decodes the resolution limited index data, the motion vector encoded data, and the image encoded data from the bitstream, respectively, to restore the resolution limited index, the motion vector, and the transformed and quantized residual images. At this time, the decoder 1110 decodes the motion vector encoded data by using the code table identified by the motion vector resolution limit step indicated by the reconstructed resolution limit index. The decoder 1110 may decode using an encoding technique such as entropy encoding. The decoder 1110 may reversely decode the encoder 140 described above with reference to FIG. 1 to decode.

The inverse quantizer and inverse transformer 1120 inverse quantizes and inverse transforms the transformed and quantized residual image to reconstruct the residual image. That is, the inverse quantizer and inverse transformer 1120 inverse quantizes and inversely transforms the quantized transform coefficients of the transformed and quantized residual image transmitted by the decoder 1110 to reconstruct the residual image having the residual signal. In this case, the inverse quantizer and the inverse converter 1120 may perform inverse quantization and inverse transformation by performing the transformation and quantization of the converter and the quantizer 1130 described above with reference to FIG. 1. Here, the reconstructed residual image is an image in a predetermined coding unit including several residual blocks, and the image of the coding unit may be various images such as a block, a slice, a picture, a picture group, and the like.

The predictor 1130 generates a predicted image of the image by using the reconstructed motion vector. That is, the predictor 1130 generates a prediction block by compensating for the motion of blocks to be encoded by using the motion vector reconstructed by the decoder 1110, and the prediction blocks are collected in a predetermined coding unit to form a prediction image. .

Also, the predictor 1130 is not a motion vector reconstructed by the decoder 1110, but a pixel unit smaller than the minimum motion vector resolution according to the limit of the motion vector resolution indicated by the resolution limit index reconstructed by the decoder 1110. A motion vector having a motion vector resolution of H may be estimated, and a prediction image may be generated using the motion vector having a motion vector resolution of a small pixel unit. Here, the predictor 1130 may determine a smaller encoding cost between the encoding cost calculated using the motion vector reconstructed by the decoder 1110 and the encoding cost calculated using the motion vector estimated with the motion vector resolution of a small pixel. The branch may generate a prediction image by using a motion vector. In this case, the predictor 1130 may estimate a motion vector having a motion vector resolution of a small pixel unit by using template matching.

The adder 1140 reconstructs the image by adding the residual image and the predicted image. That is, the adder 1140 reconstructs the image by adding the residual image reconstructed by the inverse quantizer and the inverse transformer 1120 and the predicted image generated by the predictor 1130.

The image reconstructed by the adder 1140 may be accumulated in picture units and output as a reconstructed image. The image reconstructed by the adder 1140 may be stored in the reference picture memory 1150 and used by the predictor 1130 to predict the next image.

Although not shown in FIG. 11, the image decoding apparatus 1100 according to an embodiment of the present invention may include an intra predictor for intra prediction, a deblocking filter for deblocking filtering the reconstructed current block, and the like. It may further comprise.

12 is a block diagram schematically illustrating a decoder according to an embodiment of the present invention.

The decoder 1110 may include a motion vector decoder 1210 and a predictive residual decoder 1220.

The motion vector decoder 1210 reconstructs the motion vector by decoding the motion vector coded data extracted from the bitstream according to the limitation of the motion vector resolution, which is obtained by decoding the resolution limit index data extracted from the bitstream. The motion vector encoder 1210 will be described in detail with reference to FIG. 13.

The predictive residual decoder 1220 reconstructs the transformed and quantized residual image by decoding image encoded data extracted from the bitstream.

13 is a block diagram schematically illustrating a motion vector decoding apparatus according to an embodiment of the present invention.

The motion vector decoding apparatus according to an embodiment of the present invention may be implemented as the motion vector decoder 1210 in the decoder 1110 described above with reference to FIG. 12. Hereinafter, for convenience of description, the motion vector decoding apparatus according to an embodiment of the present invention is called a motion vector decoder 1210.

The motion vector decoder 1210 may include a restricted resolution reconstructor 1310 and a motion vector reconstructor 1320.

The limited resolution decompressor 1310 decodes the resolution limited index data extracted from the bitstream to restore the limiting step of the motion vector resolution. That is, the limited resolution restorer 1310 extracts and decodes the resolution limited index data from the bitstream to restore the resolution limited index, and restores the limiting step of the motion vector resolution indicated by the reconstructed resolution limited index. In this case, the limited resolution reconstructor 1310 may extract the resolution limited index data from a header of a predetermined coding unit such as a block header, a slice header, a picture header, and the like of the bitstream. The restraining step of the reconstructed motion vector resolution has limit information of the motion vector resolution for all blocks in the image of a predetermined coding unit. For example, assuming that the limiting step of the motion vector resolution is the second step of the motion vector resolution, the motion vectors of all blocks within a predetermined coding unit have only the motion vector resolution of integer pixels or 1/2 pixel units.

The motion vector reconstructor 1320 reconstructs the motion vector by decoding motion vector coded data extracted from the bitstream according to the limitation of the reconstructed motion vector resolution. That is, the motion vector decompressor 1320 extracts and decodes motion vector encoded data from the bitstream to reconstruct motion vectors of all blocks within a predetermined coding unit, and the motion vector resolution restored by the limited resolution decompressor 1310. The motion vector encoded data may be decoded using the code table identified by the restriction step of. For example, assuming that the limiting step of the motion vector resolution is the second step of the motion vector resolution, the motion vector may be reconstructed by decoding the motion vector encoded data using a code table exemplarily shown in Table 3. To this end, the motion vector decompressor 1320 includes a different code table in advance and stores the code table according to the limitation of the motion vector resolution, and the code table is previously agreed with the motion vector encoder 430 or the image encoding apparatus 100. This is the same table.

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

According to the motion vector decoding method according to an embodiment of the present invention, the motion vector decoder 1210 decodes the resolution limit index data extracted from the bitstream to restore the limit of the motion vector resolution (S1410). The motion vector is reconstructed by decoding the motion vector encoded data extracted from the bitstream according to the motion vector resolution limiting step (S1420).

In operation S1420, the motion vector decoder 1210 may decode the motion vector encoded data using another code table according to the limitation of the motion vector resolution restored in operation S1410.

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

According to an image decoding method according to an embodiment of the present invention, the image decoding apparatus 1100 is a motion vector extracted from a bitstream in accordance with a limitation step of motion vector resolution, which is reconstructed by decoding resolution limited index data extracted from a bitstream. Decode the encoded data to restore the motion vector (S1510), decode the image coded data extracted from the bitstream to restore the transformed and quantized residual image (S1520), and inverse quantization and inverse transformation of the transformed and quantized residual image Reconstruct the residual image (S1530), generate a predicted image of the image using the reconstructed motion vector (S1540), and reconstruct the image by adding the residual image and the predicted image (S1550).

In operation S1540, the image decoding apparatus 1100 may generate a prediction image by using the motion vector reconstructed in operation S1510, but the pixel smaller than the minimum motion vector resolution according to the limit of the motion vector resolution restored in operation S1510. A small encoding cost between an encoding cost calculated by using a motion vector estimated by using a motion vector reconstructed in step S1510 and a motion vector estimated by a motion vector resolution of a small pixel A prediction image may also be generated using a motion vector having. In this case, the image decoding apparatus 1100 may estimate a motion vector having a motion vector resolution of a small pixel unit by using template matching.

Each step described above with reference to FIGS. 14 and 15 is not necessarily all performed, and some steps may be selectively omitted or added. In addition, the order of each step is not necessarily determined as shown, and the order of some or all of the steps may be changed or even performed in parallel.

As described above, according to an embodiment of the present invention, when encoding an image, it is determined by limiting the resolution of motion vectors for blocks in an image of a predetermined coding unit such as blocks and slices, and limited motion vector resolution. Since the motion vectors of the motion vectors can be encoded using a code table suitable for the limited motion vector resolution, the amount of bits required to encode the motion vectors can be reduced, and consequently, the compression efficiency of the image can be improved.

In addition, according to an embodiment of the present invention, the image encoding apparatus 100 and the image decoding apparatus 1100 may perform more than a limited motion vector resolution through a motion estimation technique such as template matching that can be performed in the same manner. Since additional motion estimation can be performed at a smaller pixel-by-pixel motion vector resolution, the image can be encoded using motion vectors with more detailed motion vector resolution. Since it is not necessary to additionally encode a motion vector having a determined fine motion vector resolution, the compression efficiency of an image may be further improved.

Meanwhile, the image encoding / decoding apparatus according to an embodiment of the present invention connects the encoded data output terminal of the image encoding apparatus 100 of FIG. 1 to the bitstream (encoding data) input terminal of the image decoding apparatus 1100 of FIG. Can be implemented.

An image encoding / decoding apparatus according to an embodiment of the present invention determines a motion vector of the image according to a limited step-by-step motion vector resolution in which the motion vector resolution is limited step by step, and predicts the image of the image by using the determined motion vector. Generate and subtract, transform, and quantize the image and the predictive image, and then encode the image to generate the limited-level image coded data, calculate the encoding cost of the limited-step image coded data, and encode the encoded image data of the limited-step image. Selects a limiting step of the motion vector resolution using; and is a resolution limit index indicating a limiting step of the image coded data encoded using the motion vector determined according to the motion vector resolution according to the selected limiting step and the selected motion vector resolution. The motion vector is decoded by decoding the motion vector encoded data extracted from the bitstream according to a video encoding apparatus for encoding and outputting the resolution limited index data and the motion vector resolution, which is obtained by decoding the resolution limited index data extracted from the bitstream. And reconstructing the image by reconstructing and inversely transforming and quantizing the bitstream from the bitstream, and reconstructing the image by inverse quantization and inverse transformation. The prediction image of the image is generated using the reconstructed motion vector. And an image decoder for reconstructing the image.

In the image encoding / decoding apparatus according to an embodiment of the present invention, an image encoder may be implemented by the image encoding apparatus 100 according to an embodiment of the present invention, and the image decoder is an image decoding apparatus according to an embodiment of the present invention. It is possible to implement (1100).

In an image encoding / decoding method according to an embodiment of the present invention, a motion vector of the image is determined according to a limited step-by-step motion vector resolution in which the motion vector resolution is limited in stages, and the predicted image of the image is determined using the determined motion vector. Generate and subtract, transform, and quantize the image and the predictive image, and then encode the image to generate the limited-level image coded data, calculate the encoding cost of the limited-step image coded data, and encode the encoded image data of the limited-step image. Selects a limiting step of the motion vector resolution using; and is a resolution limit index indicating a limiting step of the image coded data encoded using the motion vector determined according to the motion vector resolution according to the selected limiting step and the selected motion vector resolution. The image encoding method comprising: encoding and outputting the display limitations index data; And decoding the motion vector encoded data extracted from the bitstream in accordance with the limitation of the motion vector resolution, which is obtained by decoding the resolution limit index data extracted from the bitstream, and converting and quantized from the bitstream. An image decoding step of restoring a residual image, inverse quantization and inverse transformation, and restoring the image, generating a predicted image of the image using the restored motion vector, and adding the residual image and the predicted image to restore the image It includes.

In the image encoding / decoding method according to an embodiment of the present invention, the image encoding step may be implemented as an image encoding step according to an embodiment of the present invention, and the image decoding step is an image decoding step according to an embodiment of the present invention. It can be implemented.

In the above description, it is described that all the components constituting the embodiments of the present invention are combined or operated in one, but the present invention is not necessarily limited to these embodiments. In other words, within the scope of the present invention, all of the components may be selectively operated in combination with one or more. In addition, although all of the components may be implemented in one independent hardware, each or all of the components may be selectively combined to perform some or all functions combined in one or a plurality of hardware. It may be implemented as a computer program having a. Codes and code segments constituting the computer program may be easily inferred by those skilled in the art. Such a computer program may be stored in a computer readable storage medium and read and executed by a computer, thereby implementing embodiments of the present invention. The storage medium of the computer program may include a magnetic recording medium, an optical recording medium, a carrier wave medium, and the like.

In addition, the terms "comprise", "comprise" or "having" described above mean that the corresponding component may be inherent unless specifically stated otherwise, and thus excludes other components. It should be construed that it may further include other components instead. All terms, including technical and scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art unless otherwise defined. Terms used generally, such as terms defined in a dictionary, should be interpreted to coincide with the contextual meaning of the related art, and shall not be interpreted in an ideal or excessively formal sense unless explicitly defined in the present invention.

The above description is merely illustrative of the technical idea of the present invention, and those skilled in the art to which the present invention pertains may make various modifications and changes without departing from the essential characteristics of the present invention. Therefore, the embodiments disclosed in the present invention are not intended to limit the technical idea of the present invention but to describe the present invention, and the scope of the technical idea of the present invention is not limited by these embodiments. The protection scope of the present invention should be interpreted by the following claims, and all technical ideas within the equivalent scope should be interpreted as being included in the scope of the present invention.

As described above, according to an exemplary embodiment of the present invention, the present invention is applied to an image compression processing field that encodes or decodes a video and encodes or decodes a motion vector therefor, thereby adaptively limiting the resolution of the motion vector to thereby remove the motion vector. It is a very useful invention that produces the effect of improving the compression efficiency by determining and encoding.

CROSS-REFERENCE TO RELATED APPLICATION

This patent application is related to the patent application No. 10-2009-0104411 filed in Korea on October 30, 2009 and the patent application No. 10-2010-0106747 filed in Korea on October 29, 2010. If priority is claimed under section (a) (35 USC § 119 (a)), all of that is incorporated by reference into this patent application. In addition, if this patent application claims priority for the same reason as above for a country other than the United States, all the contents thereof are incorporated into this patent application by reference.

Claims (39)

1. An apparatus for encoding / decoding a video,

   The motion vector resolution of the image is determined according to the step-by-step motion vector resolution. The prediction vector of the image is generated using the determined motion vector, the image and the prediction image are subtracted, transformed and quantized. And then encoding to generate restriction step image coded data, calculate encoding cost of the restriction step image coded data, and select a restriction step of motion vector resolution using the encoding cost of the restriction step image coded data. Image coded by using the motion vector determined according to the motion vector resolution according to the limiting step, and an image that outputs the resolution limiting index data by encoding the resolution limit index indicating the limiting step of the selected motion vector resolution. Encoder; And

   Reconstructing the motion vector by decoding the motion vector encoded data extracted from the bitstream according to the limitation of the motion vector resolution, which is reconstructed by decoding the resolution limit index data extracted from the bitstream, and converting and quantized the residual from the bitstream. An image decoder for restoring an image, restoring an image by inverse quantization and inverse transformation, and generating a predicted image of the image using the restored motion vector, and adding the residual image and the predicted image to restore the image.

   Image encoding / decoding apparatus comprising a.
2. In the apparatus for encoding a video,

   A predictor for determining a motion vector of the image according to a step-by-step limited motion vector resolution and generating a predicted image of the image using the determined motion vector;

   A subtractor for generating a residual image by subtracting the image and the prediction image;

   A converter and quantizer for transforming and quantizing the residual image; And

   Encoding the transformed and quantized residual images to generate restriction image encoding data, calculating encoding cost of the restriction phase image encoding data, and limiting motion vector resolution using the encoding cost of the restriction phase image encoding data. And encoding the image coded data encoded using the motion vector determined according to the motion vector resolution according to the selected limiting step and the resolution limiting index indicating the limiting step of the selected motion vector resolution. An encoder that generates a bitstream

   An image encoding apparatus comprising a.
3. The method of claim 2, wherein the encoder,

   Estimating a motion vector of a motion vector resolution of a pixel unit smaller than the minimum motion vector resolution according to the limiting step of the selected motion vector resolution, and predictively encoding the image using the estimated motion vector resolution of a motion vector resolution of a small pixel unit. And generating a bitstream including the encoded image encoded data.
4. The method of claim 3, wherein the encoder,

   And a motion vector having a motion vector resolution of the small pixel unit using template matching.
5. The method of claim 3, wherein the encoder,

   The prediction cost of encoding the image according to the motion vector determined according to the limiting step of the selected motion vector resolution and the motion vector of the motion vector resolution of the small pixel unit are predicted to be encoded. And a video encoding data encoded using a motion vector having a smaller encoding cost among the encoding costs.
6. In the apparatus for decoding an image,

   Decoding the motion vector encoded data extracted from the bitstream according to the limitation of the motion vector resolution, which is obtained by decoding the resolution limit index data extracted from the bitstream, and reconstructs the motion vector, and the image encoded data extracted from the bitstream. A decoder to decode and reconstruct the transformed and quantized residual images;

   An inverse quantizer and an inverse converter for inversely quantizing and inversely transforming the transformed and quantized residual image to reconstruct the residual image;

   A predictor for generating a predicted image of the image using the reconstructed motion vector; And

   An adder for reconstructing the image by adding the residual image and the prediction image;

   Video decoding apparatus comprising a.
7. The method of claim 6, wherein the decoder,

   Estimating a motion vector of a motion vector resolution of a pixel unit smaller than the minimum motion vector resolution according to the limit of the reconstructed motion vector resolution, and using a coding cost calculated using the reconstructed motion vector and the estimated motion vector. An image decoding apparatus, characterized by reconstructing a motion vector having a small encoding cost among the calculated encoding costs as a motion vector.
8. In the device for encoding a motion vector,

   An encoding cost calculator for calculating an encoding cost according to the motion vector resolution in which the motion vector resolution is limited step by step;

   A limiting resolution determiner which selects a limiting step of the motion vector resolution by using the encoding cost calculated in the limiting step; And

   A motion information encoder for encoding the motion vector coded data in which the motion vector determined according to the limiting step of the selected motion vector resolution is encoded and the resolution limit index indicating the limiting step of the selected motion vector resolution to output resolution limit index data.

   Motion vector encoding apparatus comprising a.
9. The method of claim 8, wherein the limited resolution determiner,

   And a step of limiting the motion vector resolution for each coding unit including at least one of a block, a slice, a picture, and a picture group.
10. The method of claim 8, wherein the motion vector resolution,

    And at least one of an integer pixel resolution, a 1/2 pixel resolution, a 1/4 pixel resolution, and a 1/8 pixel resolution.
11. The method of claim 8, wherein the limited resolution determiner,

    And a limiting step having the smallest coding cost among the coding costs calculated by the limiting step as the limiting step of the motion vector resolution.
12. The method of claim 8, wherein the encoding cost calculator,

    And determining at least one of a motion vector for each block and a block mode according to the limited step motion vector resolution, and calculating a coding cost using at least one of the determined motion vector and the determined block mode.
13. The method of claim 8, wherein the calculating of the encoding cost comprises:

    And encoding the motion vector by using a different code table according to the motion vector resolution of the limited step.
14. In the apparatus for decoding a motion vector,

    A limited resolution decompressor for decoding the resolution limited index data extracted from the bitstream and restoring the limitation of the motion vector resolution; And

    A motion vector reconstructor for decoding a motion vector coded data extracted from a bitstream according to the restriction of the reconstructed motion vector resolution to reconstruct a motion vector.

    Motion vector decoding apparatus comprising a.
15. The method of claim 14, wherein the motion vector decompressor,

    And decoding the motion vector encoded data using a code table corresponding to the restraining step of the reconstructed motion vector resolution.
16. The method of claim 14,

    The resolution limit index data,

    The motion vector decoding apparatus is generated based on the coding cost according to the motion vector resolution for each step, which is calculated for each motion vector resolution limit step.
17. The method of claim 14,

    And the resolution limited index data is included for each decoding unit including at least one of a block, a slice, a picture, and a picture group.
18. The method of claim 14,

    The reconstructed motion vector resolution limiting step includes a resolution in units of 1/8 pixels.
19. The method of claim 16,

    The coding cost according to the limited step motion vector resolution is calculated using at least one of a motion vector and a block mode determined according to the limited step motion vector resolution.
20. In the method of encoding / decoding an image,

    The motion vector resolution of the image is determined according to the step-by-step motion vector resolution. The prediction vector of the image is generated using the determined motion vector, the image and the prediction image are subtracted, transformed and quantized. And then encoding to generate restriction step image coded data, calculate encoding cost of the restriction step image coded data, and select a restriction step of motion vector resolution using the encoding cost of the restriction step image coded data. Image coded by using the motion vector determined according to the motion vector resolution according to the limiting step, and an image that outputs the resolution limiting index data by encoding the resolution limit index indicating the limiting step of the selected motion vector resolution. An encoding step; And

    Reconstructing the motion vector by decoding the motion vector encoded data extracted from the bitstream according to the limitation of the motion vector resolution, which is reconstructed by decoding the resolution limit index data extracted from the bitstream, and converting and quantized the residual from the bitstream. An image decoding step of restoring an image, restoring the image by inverse quantization and inverse transform, generating a predicted image of the image using the restored motion vector, and adding the residual image and the predicted image to restore the image.

    Image encoding / decoding method comprising a.
21. In the method of encoding an image,

    Determining a motion vector of the image according to a step-by-step motion vector resolution with limited motion vector resolution;

    Generating a predicted image of the image by using the determined motion vector;

    Generating a residual image by subtracting the image and the prediction image;

    Converting and quantizing the residual image;

    Encoding the transformed and quantized residual images to generate image coded data for each step;

    Calculating a coding cost of the limited stage image coded data;

    Selecting a limiting step of the motion vector resolution by using the encoding cost of the video encoding data of the limiting step; And

    Generating a bitstream including image coded data encoded using a motion vector determined according to the motion vector resolution according to the selected limiting step and resolution limit index data indicating a limiting step of the selected motion vector resolution;

    Image encoding method comprising a.
22. The method of claim 21, wherein generating the bitstream,

    Estimating a motion vector having a motion vector resolution smaller than the minimum motion vector resolution according to the limiting step of the selected motion vector resolution;

    Generating a bitstream including encoded image encoded data by predictively encoding the image by using the motion vector having the estimated motion pixel resolution of the small pixel unit.

    Image encoding method comprising a.
23. The method of claim 22, wherein estimating the motion vector comprises:

    And a motion vector having a motion vector resolution of the small pixel unit using template matching.
24. The method of claim 22, wherein the predictive encoding of the image to generate a bitstream including encoded image encoded data comprises:

    The prediction cost of encoding the image according to the motion vector determined according to the limiting step of the selected motion vector resolution and the motion vector of the motion vector resolution of the small pixel unit are predicted to be encoded. And a video encoding data encoded using a motion vector having a smaller encoding cost among the encoding costs.
25. In the method of decoding an image,

    Reconstructing the motion vector by decoding the motion vector encoded data extracted from the bitstream according to the limitation of the motion vector resolution reconstructed by decoding the resolution limited index data extracted from the bitstream;

    Restoring the transformed and quantized residual image by decoding the image encoded data extracted from the bitstream;

    Inversely quantizing and inversely transforming the transformed and quantized residual image to reconstruct the residual image;

    Generating a predicted image of the image by using the reconstructed motion vector; And

    Reconstructing the image by adding the residual image and the prediction image

    Image decoding method comprising a.
26. The method of claim 25, wherein the reconstructing the motion vector comprises:

    Estimating a motion vector having a motion vector resolution of a pixel unit smaller than the minimum motion vector resolution according to the limitation of the reconstructed motion vector resolution;

    Reconstructing a motion vector having a smaller encoding cost as a motion vector between a coding cost calculated using the reconstructed motion vector and a coding cost calculated using the estimated motion vector.

    Image decoding method comprising a.
27. The method of claim 26, wherein estimating the motion vector,

    And using a template matching to estimate a motion vector having a resolution of the motion vector in the unit of small pixels.
28. In the method of encoding a motion vector of an image,

    Calculating a coding cost according to the motion vector resolution in which the motion vector resolution is limited step by step;

    Selecting a limiting step of the motion vector resolution using the coding cost calculated in the limiting step; And

    Outputting motion vector encoded data encoded with a motion vector determined according to the limiting step of the selected motion vector resolution and resolution limit index data indicating a limiting step of the selected motion vector resolution;

    Motion vector encoding method comprising a.
29. 29. The method of claim 28, wherein selecting the limiting step comprises:

    And limiting the motion vector resolution for each coding unit including at least one of a block, a slice, a picture, and a picture group.
30. The method of claim 28, wherein the motion vector resolution,

    A motion vector encoding method comprising at least one of an integer pixel resolution, a 1/2 pixel resolution, a 1/4 pixel resolution, and a 1/8 pixel resolution.
31. The method of claim 28, wherein the step of selecting the limiting step,

    And a limiting step having the smallest coding cost among the coding costs calculated by the limiting step as the limiting step of the motion vector resolution.
32. The method of claim 28, wherein the calculating of the encoding cost comprises:

    And determining at least one of a motion vector for each block and a block mode according to the step-by-step motion vector resolution, and calculating a coding cost using at least one of the determined motion vector and the determined block mode.
33. 29. The method of claim 28, wherein calculating the encoding cost comprises:

    And encoding the motion vector using a different code table according to the motion vector resolution according to the limited step to calculate the encoding cost.
34. In the method for decoding a motion vector,

    Restoring the limit of the motion vector resolution by decoding the resolution limit index data extracted from the bitstream; And

    Reconstructing a motion vector by decoding motion vector coded data extracted from a bitstream according to the limitation of the reconstructed motion vector resolution.

    Motion vector decoding method comprising a.
35. The method of claim 34,

    The resolution limit index data,

    A motion vector decoding method, wherein the motion vector resolution is generated based on a coding cost according to the motion vector resolution.
36. 36. The method of claim 34 or 35, wherein the reconstructing the motion vector comprises:

    And decoding the motion vector encoded data by using a code table corresponding to the restraining step of the reconstructed motion vector resolution.
37. 36. The method of claim 34 or 35,

    And the resolution limited index data is included for each decoding unit including one or more of blocks, slices, pictures, and picture groups.
38. 36. The method of claim 34 or 35,

    The restoring motion vector resolution limiting step includes a resolution in units of 1/8 pixels.
39. 36. The method of claim 34 or 35,

    The encoding cost according to the limited step motion vector resolution is calculated using at least one of a motion vector and a block mode determined according to the limited step motion vector resolution.

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