KR100774300B1 - Method and apparatus for decoding motion vectors - Google Patents

Abstract

A method and apparatus for decoding a motion vector are disclosed. According to another aspect of the present invention, there is provided a method of decoding a motion vector, the method comprising: selecting a neighboring block having a motion vector to be used as a predicted motion vector of a current block according to a size and a position of a current block included in the macroblock; Wherein the step of selecting a neighboring block to be used as a predictive motion vector of a current block comprises the steps of: if the size of the current block in the macroblock is 16x8 and the current block is a lower block in the macroblock, The motion vector of the neighboring block adjacent to the left side of the block is selected as the predicted motion vector of the current block.

Description

[0001] The present invention relates to a motion vector decoding method,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to motion vector coding and decoding, and more particularly, to a method and a device for coding a motion vector calculated with reference to a plurality of pictures.

According to the MPEG-1 or MPEG-2 coding standard, in encoding a current picture, a P-picture coding method which refers to a past picture and a B-picture coding method which refers to both past and future pictures are adopted And motion compensation is performed based on this. In addition, in order to increase the coding efficiency, the motion vector of the current block is not encoded as it is, but prediction coding is performed using motion vectors of neighboring blocks so that the association between motion vectors between neighboring blocks is reflected.

It may happen that the motion vectors of neighboring blocks used for predictive coding do not use the same reference picture as that of the current block. When such a case occurs, a motion vector of a neighboring block which is not the same as a reference picture has been dealt with in a process of excluding it from a predictive coding process. If the motion vector obtained based on another reference picture participates in the prediction coding, the coding efficiency may be lowered. However, if the motion vector of a neighboring block having a different reference picture is excluded from the predictive coding process, the degree of relevance of motion vectors of neighboring blocks is lowered, and thus the coding efficiency of the motion vector may be reduced accordingly. This is particularly so in the case of a picture in which the reference pictures are frequently different from each other.

An object of the present invention is to provide a motion vector coding method, a decoding method thereof, and an apparatus therefor, which can more efficiently perform predictive coding even for motion vectors different from each other in reference pictures.

Another object of the present invention is to provide a motion vector coding method, a decoding method thereof, and an apparatus therefor, which improve coding efficiency by re-adjusting at least a part of motion vectors which are different from each other.

According to another aspect of the present invention, there is provided a method of coding a motion vector, the method comprising the steps of: (a) determining, for a neighboring block having a motion vector of a type different from a motion vector of the current block among a plurality of neighboring blocks neighboring the current block, Estimating a motion vector of the same type as a motion vector to obtain a predicted motion vector; (b) calculating a representative value of the motion vectors of the same type as the motion vector of the current block among the motion vectors of the neighboring blocks including the predicted motion vector; (c) calculating an error value between the calculated representative value and the motion vector of the current block; And (d) encoding the calculated error value.

According to another aspect of the present invention, there is provided an apparatus for coding a motion vector, the apparatus comprising: a motion vector estimating unit for estimating, for a neighboring block having a motion vector of a different type from a motion vector of the current block among a plurality of neighboring blocks neighboring the current block, A motion vector of the same type as the motion vector of the current block is predicted to obtain a predicted motion vector and motion vectors of the same type as the motion vector of the current block among the motion vectors of the neighboring blocks, A motion vector predictor for calculating an error value between the calculated representative value and the motion vector of the current block; And a motion vector encoder for coding the calculated error value.

When the motion vector of the current block is the forward motion vector MVf and the motion vector of the neighboring block is the backward motion vector MVb, the motion vector predictor calculates the forward motion vector MVf (prediction), which is the predictive motion vector, .

MVf (prediction) = {Distance between the current picture to which the neighboring block belongs and the reference picture to which the neighboring block belongs / Distance between the future picture referenced by the neighboring block and the past picture - Distance between the current picture to which the neighboring block belongs and the past picture to which the neighboring block belongs) * MVb

When the motion vector of the current block is the backward motion vector MVb and the motion vector of the neighboring block is the forward motion vector MVf, the motion vector predictor calculates the backward motion vector MVb (prediction), which is the predictive motion vector, .

MVb (prediction) = {(distance between the future picture referred to by the neighboring block and the previous picture, distance between the current picture to which the neighboring block belongs and the past reference picture) / distance between the current picture to which the neighboring block belongs, * MVf

The motion vector predictor preferably obtains a predictive value PMV_X, which is a representative value calculated by the following equation.

PVM_X = median (MVf_A, MVf_B, MVf_C) or median (MVb_A, MVb_B, MVb_C)

Here, MVf_A, MVf_B, MVf_C, MVb_A, MVb_B, and MVb_C are components of the motion vectors of the neighboring blocks, MVf_A is the forward motion vector of the left block, MVf_B is the forward motion vector of the upper block, MVb_A is the backward motion vector of the left block. MVb_B denotes a backward motion vector of the upper block, and MVb_C denotes a backward motion vector of the upper right block. The predictive motion vector may be any one of them.

According to another aspect of the present invention, there is provided a method of decoding a motion vector, the method comprising the steps of: (a) decoding neighboring blocks having a motion vector of a type different from the current block from a plurality of neighboring blocks neighboring the current block; Estimating a motion vector of the same type as the motion vector of the current block to obtain a predicted motion vector; (b) calculating a representative value of the motion vectors of the same type as the current block among the motion vectors of the neighboring blocks including the predicted motion vector; And (c) calculating a motion vector of the current block by adding the calculated representative value and the decoded error value.

When the motion vector of the current block is the forward motion vector MVf and the motion vector of the neighboring block is the backward motion vector MVb, the forward motion vector MVf (prediction), which is the predictive motion vector, is calculated by the following equation .

MVf (prediction) = {time difference between the current picture to which the neighboring block belongs and the referenced past picture / (time difference between the future picture referenced by the neighboring block and the past picture - temporal difference between the current picture to which the neighboring block belongs and the past picture to which the neighboring block belongs) * MVb

When the motion vector of the current block is the backward motion vector MVb and the motion vector of the neighboring block is the forward motion vector MVf, the backward motion vector MVb (prediction), which is the predictive motion vector, is calculated by the following equation .

MVb (prediction) = {(time difference between the future picture referred to by the neighboring block and the past picture, time difference between the current picture to which the neighboring block belongs and the past picture referred to) / temporal difference between the current picture to which the neighboring block belongs and the past picture to which the neighboring block belongs} * MVf

When the motion vector of the current block is the forward motion vector MVf and the motion vector of the neighboring block is the backward motion vector MVb, the forward motion vector MVf (prediction), which is the prediction motion vector, is calculated by the following equation.

MVf (prediction) = {Distance between the current picture to which the neighboring block belongs and the reference picture to which the neighboring block belongs / Distance between the future picture referenced by the neighboring block and the past picture - Distance between the current picture to which the neighboring block belongs and the past picture to which the neighboring block belongs) * MVb

When the motion vector of the current block is the backward motion vector MVb and the motion vector of the neighboring block is the forward motion vector MVf, the backward motion vector MVb (prediction), which is the predictive motion vector, is calculated by the following equation .

MVb (prediction) = {(distance between the future picture referred to by the neighboring block and the previous picture, distance between the current picture to which the neighboring block belongs and the past reference picture) / distance between the current picture to which the neighboring block belongs, * MVf

The step (b) is preferably a step of obtaining a predictive value PMV_X for decoding, which is a representative value calculated by the following equation.

PVM_X = median (MVf_A, MVf_B, MVf_C) or median (MVb_A, MVb_B, MVb_C)

Here, MVf_A, MVf_B, MVf_C, MVb_A, MVb_B, and MVb_C are components of the motion vectors of the neighboring blocks, MVf_A is the forward motion vector of the left block, MVf_B is the forward motion vector of the upper block, MVb_A is the backward motion vector of the left block. MVb_B denotes a backward motion vector of the upper block, and MVb_C denotes a backward motion vector of the upper right block. The predictive motion vector may be any one of them.

According to another aspect of the present invention, there is provided an apparatus for decoding a motion vector, the apparatus comprising: a motion vector decoder for decoding an error value; And a motion vector predictor for estimating a motion vector of the same type as that of the current block with respect to a neighboring block having a motion vector of a different type from the current block among a plurality of neighboring blocks neighboring the current block, A representative value of the motion vectors of the same type as the motion vector of the current block among the motion vectors of the neighboring blocks is calculated and the motion vector of the current block is calculated by adding the calculated representative value and the error value And a motion vector prediction compensator for performing motion vector prediction.

When the motion vector of the current block is the forward motion vector MVf and the motion vector of the neighboring block is the backward motion vector MVb, the motion vector prediction compensator calculates the forward motion vector MVf (prediction) .

MVf (prediction) = {time difference between the current picture to which the neighboring block belongs and the referenced past picture / (time difference between the future picture referenced by the neighboring block and the past picture - temporal difference between the current picture to which the neighboring block belongs and the past picture to which the neighboring block belongs) * MVb

When the motion vector of the current block is a backward motion vector MVb and the motion vector of the neighboring block is a forward motion vector MVf, the motion vector prediction compensator calculates a backward motion vector MVb (prediction) .

MVb (prediction) = {(time difference between the future picture referred to by the neighboring block and the past picture, time difference between the current picture to which the neighboring block belongs and the past picture referred to) / temporal difference between the current picture to which the neighboring block belongs and the past picture to which the neighboring block belongs} * MVf

When the motion vector of the current block is the forward motion vector MVf and the motion vector of the neighboring block is the backward motion vector MVb, the motion vector prediction compensator calculates the forward motion vector MVf (prediction) .

MVf (prediction) = {distance between the current picture to which the neighboring block belongs and the reference picture past / (distance between the future picture referenced by the neighboring block and the previous picture, distance between the current picture to which the neighboring block belongs, } * MVb

When the motion vector of the current block is a backward motion vector MVb and the motion vector of the neighboring block is a forward motion vector MVf, the motion vector prediction compensator calculates a backward motion vector MVb (prediction) .

MVb (prediction) = {(distance between the future picture referred to by the neighboring block and the previous picture, distance between the current picture to which the neighboring block belongs and the past reference picture) / distance between the current picture to which the neighboring block belongs, * MVf

The above object is also achieved by a computer-readable information storage medium having recorded therein a program code for performing the above-described encoding method or decoding method.

According to another aspect of the present invention, there is provided a motion vector decoding method comprising: selecting a neighboring block having a motion vector to be used as a predicted motion vector of a current block according to a size and a position of a current block included in the macro block; And selecting a motion vector of the selected neighboring block as a predicted motion vector of the current block, wherein the step of selecting a neighboring block to be used as a predicted motion vector of the current block includes: And if the current block is a lower side block in a macroblock, a motion vector of a neighboring block adjacent to the left of the current block is selected as a predicted motion vector of the current block.

According to another aspect of the present invention, there is provided an apparatus for decoding a motion vector, the apparatus comprising: a motion vector decoding unit decoding a difference value between an original motion vector of a current block and a predicted motion vector of the current block; And selecting a neighboring block having a motion vector to be used as a predictive motion vector of the current block according to the size and position of the current block included in the macroblock, and selecting a motion vector of the selected neighboring block as a predictive motion vector of the current block And a motion vector prediction compensator for adding the selected predictive motion vector and the decoded difference value, wherein the motion vector prediction compensator compensates the motion vector predictor for a current block in the macroblock with a size of 16x8, The motion vector of the neighboring block adjacent to the left of the current block is selected as the predicted motion vector of the current block.

According to the present invention, in encoding and decoding a motion vector, a motion vector of the same type is predicted for a neighboring block having a motion vector of a type different from the motion vector of the current block, an intermediate value is obtained based on the predicted motion vector, The motion vector of the current block is obtained by adding the intermediate value obtained based on the predicted motion vector to the decoded difference value for the neighboring block having the motion vector of the different type from the current block, Coding efficiency and decoding efficiency are increased.

That is, in coding or decoding the motion vector of the current block, it is based on the representative value (intermediate value) of the neighboring blocks, that the motion of neighboring blocks is similar. According to the motion vector coding method and the decoding method of the present invention, it is possible to improve the problem that motion of neighboring blocks is not properly reflected by excluding a motion vector of a conventional type from calculation of a representative value (intermediate value) Even when a motion vector is included, a prediction motion vector of the same type is obtained and reflected in a representative value (intermediate value) to improve encoding and decoding efficiency.

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

1 is a block diagram of a motion vector coding apparatus according to a preferred embodiment of the present invention.

Referring to FIG. 1, an encoder 70 encodes a motion vector, and includes a motion vector predictor 701 and a motion vector encoder 702. When motion vectors for a plurality of blocks are inputted, the motion vector predictor 701 predicts a motion vector of a neighboring block having only motion vectors of a different type from a motion vector of the current block among a plurality of neighboring blocks neighboring the current block, A motion vector of the same type as the motion vector of the current block is predicted to obtain a predicted motion vector and motion vectors of the same type as the motion vector of the current block among the motion vectors of the neighboring blocks, And calculates an error value between the calculated representative value and the motion vector of the current block. The motion vector encoder 702 encodes the error value output from the motion vector predictor 701. In this embodiment, the motion vector encoder 702 encodes a difference value as an error value.

FIG. 2 is a block diagram of an image data encoding apparatus including the motion vector encoding apparatus of FIG. 1, according to a preferred embodiment of the present invention.

Referring to FIG. 2, the image data encoding apparatus includes a coding control unit 100, a first source coding unit 200, and a second source coding unit 700, do. In addition, a source decoding unit 300, a memory unit 400, a motion compensation unit 500, and a motion prediction unit 600 are provided.

As shown in FIG. 3, input image data is composed of blocks obtained by dividing a frame or a frame input from a camera along a time axis into a predetermined size. The frame includes a progressive scan frame obtained by the progressive scanning method, a field obtained by the interlaced scanning method, or an interlaced scanning frame. Therefore, the video data described below means a picture of a progressive scan frame, an interlaced scan frame, a field, and a block structure.

When the video data is input, the encoding control unit 100 determines a coding-type (intra coding / inter coding) according to whether to perform motion compensation on the input video according to characteristics of the input video or a predetermined operation objective desired by the user And outputs the corresponding control signal to the first switch S1. In the case of performing motion compensation, the first switch S1 is closed because the previous or the later input image data is required. When the motion compensation is not performed, the previous or later input image data is not needed, (S1) is opened. When the first switch S1 is closed, the difference image data obtained from the input image and the previous or subsequent image are input to the first source encoding unit 200 and the first switch S1 is opened, only the input image is input to the first source encoding unit 200).

The first source encoding unit 200 quantizes the transform coefficient values obtained by transform coding the input image data according to a predetermined quantization step to obtain N × M data that is two-dimensional data composed of quantized transform coefficient values . An example of the transform used is DCT (Discrete Cosine Transform). The quantization is performed according to a predetermined quantization step.

Since the image data input to and coded by the first source coding unit 200 can be used as reference data for motion compensation of the image data inputted in the following or before, the source decoding unit 300 decodes the image data, And then stored in the memory 400 after being subjected to inverse quantization and inverse transform coding, which are inverse processes of the inverse quantizer 200. If the data output from the source decoding unit 200 is differential image data, the coding control unit 100 closes the second switch S2 and outputs the differential image data output from the source decoding unit 300 to the motion compensation unit 500. [ And then stored in the memory 400. FIG.

The motion estimation unit 600 compares input image data with data stored in the memory 400 to find data most similar to the currently inputted data and then compares the input image data with the input image data to obtain a motion vector MV Motion Vector). A motion vector is obtained by referring to at least one picture. That is, it can be calculated with reference to a plurality of past and / or future pictures. When the motion vector is transferred to the memory 400, the memory 400 outputs the corresponding data to the motion compensation unit 500. The motion compensation unit 500 compresses the image data And outputs the compensation value corresponding to the output value.

The second source encoder 700 receives the quantized transform coefficients output from the first source encoder 200 and the motion vector output from the motion estimator 600, Coding type information, quantization step information, and other information necessary for decoding and the like, and outputs the finally obtained bitstream.

The motion vector coding apparatus 70 according to the present invention is provided in the second source coding unit 700. Therefore, the motion vector coding method according to the present invention is performed by the second source coding unit 700. [ As in the MPEG-4 coding standard and the H.263 coding standard, the second source coding unit 700 does not directly encode the motion vector of the current block in order to enhance the coding efficiency by reflecting the association between the motion vectors, And predictive coding is performed using the motion vectors of the motion vectors.

4 is a block diagram of a motion vector decoding apparatus according to a preferred embodiment of the present invention.

Referring to FIG. 4, the apparatus for decoding a motion vector according to the present invention includes a motion vector decoder 131 and a motion vector prediction compensator 132. The motion vector decoder 131 decodes the input encoded motion vector error value and restores the error value. In order to obtain the original motion vector from the reconstructed error value, the predicted value used for the error value calculation should be obtained and added to the error value, so that the original motion vector can be finally obtained. For this, the motion vector prediction compensator 132 receives the motion vectors for the plurality of blocks and receives the motion vectors of neighboring blocks having only different types of motion vectors from the motion vectors of the current block among a plurality of neighboring blocks neighboring the current block A motion vector of the same type as the motion vector of the current block is predicted to obtain a predicted motion vector, and a motion vector of the same type as the motion vector of the current block among the motion vectors of the neighboring blocks, And adds the calculated representative value to the error value reconstructed by the motion vector decoder 131 to calculate a motion vector of the current block.

The motion vector decoding method according to the present invention is performed by the motion vector decoding apparatus 130 according to the present invention. As in the MPEG-4 coding standard and the H.263 coding standard, the motion vector decoding apparatus 130 does not decode the motion vector of the current block in order to enhance the decoding efficiency by reflecting the association between the motion vectors, Predictive decoding is performed using motion vectors.

FIG. 5 is a block diagram of a video data decoding apparatus provided with the motion vector decoding apparatus 130 of FIG.

Referring to FIG. 5, the decoding apparatus includes a demultiplexer 110, a second source decoder 710, and a first source decoder 210 for demultiplexing a bitstream. In addition, a coding type information decoding unit 120 for decoding coding type information and a motion vector decoding unit 130 for performing motion vector decoding according to the present invention are provided.

The bit stream is demultiplexed into entropy-encoded quantized transform coefficients, motion vector information, coding type information, and the like by the demultiplexer 110. The second source decoding unit 710 entropy-decodes the encoded transcoding coefficients and outputs quantized transcoded coefficients. The first source decoding unit 210 performs source decoding on the quantized transform coefficients. That is, the inverse process of the first source encoding unit 200 of FIG. 1 is performed. For example, if the first source coding unit 200 performs DCT, the first source decoding unit 210 performs an IDCT (Inverse Discrete Cosine Transform). Thus, the image data is restored. The restored image data is stored in the memory unit 410 for motion compensation.

Meanwhile, the coding type information decoding unit 120 finds the coding type and closes the third switch S30 when the inter type is motion compensation, and adds the data output from the first source decoding unit 210 to the motion compensation unit 510 To be added to the motion compensation value to obtain the reconstructed image data. The motion vector decoding unit 130 notifies the position indicated by the motion vector obtained from the motion vector information, and the motion compensation unit 510 generates and outputs a motion compensation value from the reference image data indicated by the motion vector. The detailed operation of the motion vector decoding unit 130 is the same as that described with reference to FIG. 10, and thus a repetitive description thereof will be omitted.

6 is a reference diagram for explaining a multiple reference method according to a preferred embodiment of the present invention.

Referring to FIG. 6, an I picture indicates an intra picture obtained without referring to another picture, and a B picture indicates a bi-predictive picture obtained by referring to two different pictures. A P picture indicates a predictive picture obtained by referring to only an I picture. The arrows show the pictures, or dependencies, needed for decoding. The B2 picture is dependent on the I0 picture and the P4 picture, and the B1 picture is dependent on the I0 picture, the P4 picture, and the B2 picture. The B3 picture is subordinate to the I0 picture, the P4 picture, the B1 picture, and the B2 picture. Therefore, the display order is I 0, B 1, B 2, B 3, P 4 .. but the order of transmission is I 0, P 4, B 2, B 1, B 3 .... As described above, according to the encoding apparatus of FIG. 1, there are B pictures generated by referring to a plurality of pictures. In other words, the motion vector in the encoding method and the decoding method of the present invention may be at least one of a forward prediction method, a backward prediction method, a bi-directional prediction method, and a direct prediction method, . In the bidirectional prediction method, both reference pictures can be either a past picture or a future picture in all.

FIG. 7 is a reference view showing motion compensation blocks as motion compensation units according to a preferred embodiment of the present invention. Referring to FIG.

Referring to FIG. 7, a picture is composed of a plurality of motion compensation blocks. The motion compensation block includes a 16 × 16 macroblock (MB) according to the present embodiment, a 16 × 8 block obtained by dividing the macroblock in the horizontal direction, an 8 × 16 block obtained by dividing the macroblock in the vertical direction, An 8x8 block obtained by dividing a macroblock in the horizontal and vertical directions, an 8x4 block or a 4x8 block obtained by dividing the macroblock in the horizontal or vertical direction, and a 4x8 block obtained by dividing the macroblock in the horizontal and vertical directions, respectively × 4 blocks.

The motion vector coding method according to the present invention is based on a differential coding scheme (differential pulse coded modulation) for coding a representative value of neighboring blocks of the motion vector MV_X of the current block, that is, an error value with respect to a median in the present embodiment . That is, if the motion vectors of the left block A, the upper block B, and the upper right block C, which are neighbor blocks for the current block X, are MV_A, MV_B, and MV_C, respectively, a prediction vector PVM_X, which is a prediction vector for differential vector coding, The difference vector MVD_X is calculated by the following equation (1). The calculation is performed independently for each of the component values (x component and y component) of the vector. On the other hand, the left block A indicates a block to which the adjacent pixel to the left of the leftmost pixel of the first row belonging to the current block X belongs, and the upper block C indicates the block adjacent to the uppermost pixel of the leftmost pixel of the first row belonging to the current block X And the upper right side block C indicates a block to which a pixel adjacent to the right side of the pixel adjacent to the upper right side of the pixel on the right side of the first row belonging to the current block X belongs.

PMV_X = median (MV_A, MV_B, MV_C)

MVD_X = MV_X - PMV_X

The motion vector decoding method according to the present invention is based on a decoding method of obtaining a motion vector MV_X of a current block by adding a representative value of neighboring blocks of the current block, in this embodiment, an intermediate value (median) and an error value MVD_X obtained by decoding. That is, if the motion vectors of the left block A, the upper block B, and the upper right block C, which are neighbor blocks for the current block X, are MV_A, MV_B, and MV_C, respectively, a prediction vector PVM_X, which is a prediction value for decoding, The motion vector MV_X obtained by adding MVD_X is calculated by the following equation (2). The calculation is performed independently for each of the component values (x component and y component) of the vector.

PMV_X = median (MV_A, MV_B, MV_C)

MV_X = MVD_X + PMV_X

The logic for processing an exception case in obtaining a predicted motion vector according to the above-described encoding method and decoding method is as follows.

First, when a specific block among the neighboring blocks A, B, C, and D is located outside a picture (or a slice), the following processing is performed. A slice is a minimum unit of a series of data sequences having a start code and has an arbitrary length and is composed of macro blocks. The slice does not exist across several pictures and exists inside one picture.

(1) MV_A = MV_D = 0 if blocks A and D are both located outside the picture (or slice), and blocks A and D are considered to have reference pictures different from the current block X.

(2) MV_B = MV_C = MV_A when the blocks B, C, and D are located outside the picture (or slice), and MV_A must be the predicted vector PMV_X of the current block X when taking an intermediate value.

(3) If block C is located outside the picture (or slice), replace it with block D. The block D indicates a block to which a pixel adjacent to the upper left side of the leftmost pixel of the first row belonging to the current block X belongs as the upper left side block of the current block X. [

Second, if the neighboring blocks are intra-coded, that is, if there is a block coded in intra-neighboring blocks A, B, C, and D, the motion vector of the block is regarded as having 0 and having another reference picture.

Thirdly, when the neighboring block has a reference picture different from the current block, a "predicted motion vector" is obtained according to the method proposed by the present invention, and then a "predicted motion vector" obtained is used to obtain an intermediate value. In other words, if the current block and the neighboring block participating in the predictive encoding have different types of motion vectors, a predictive motion vector of the same type is obtained according to the method proposed by the present invention, Is substituted into the equation for obtaining the predictive vector to obtain the intermediate value.

8 is a reference diagram for explaining a case of obtaining a predicted motion vector according to a preferred embodiment of the present invention.

Referring to FIG. 8, the current block X has a forward motion vector MVf_X, and the neighboring blocks A and D have forward motion vectors MVf_A and MVf_D of the same type as the current block X. [ However, neighboring block B has a different type of backward motion vector MVb_B than current block X, and neighboring block C has both forward motion vector MVf_C and backward motion vector MVb_C.

The intermediate values according to the above-described equations (1) and (2) must be obtained for the same type of motion vectors. This is because encoding and decoding efficiency may be degraded if motion vectors different from the current block participate in encoding and decoding. Since the neighboring block B does not have the same type of motion vector, the predicted motion vector of the neighboring block B must be obtained. In other words, a forward motion vector of the same type as the current block X must be predicted.

FIG. 9 shows an example of a method of obtaining a predicted motion vector.

Referring to FIG. 9, the forward motion vector MVf (prediction) or the backward motion vector MVb (prediction) as a prediction motion vector for a neighboring block can be predicted by the following equation.

MVb (prediction) = {(Distance_B - Distance_A) / Distance_B} * MVf

MVf (prediction) = {Distance_B / (Distance_B - Distance_A)} * MVb

Here, Distance_A is the picture distance (picture_distance) between the reference picture 1 and the reference picture 2 referenced by the current picture to which the corresponding neighboring block belongs, and Distance_B is the picture distance (picture_distance) between the current picture and the reference picture 1 to which the corresponding neighboring block belongs. In this example, reference picture 1 is a past picture for the current picture and reference picture 2 is a future picture.

FIG. 10 shows another example of a method of obtaining a predicted motion vector.

Referring to FIG. 10, the forward motion vector MVf (prediction) or the backward motion vector MVb (prediction) as predicted motion vectors for neighboring blocks can be predicted by the following equation.

MVb (prediction) = {(TR_B - TR_A) / TR_B} * MVf

MVf (prediction) = {TR_B / (TR_B - TR_A)} * MVb

Here, TR_A is the time difference between the current picture to which the corresponding neighboring block belongs and the future picture referenced by the current picture, and TR_B is the time difference between the current picture and the past picture to which the corresponding neighboring block belongs. The time difference can be obtained from a counter value TR (Temporal Reference) for knowing the relative time sequence of display between pictures.

Meanwhile, since the motion vector coding method according to the present invention has characteristics of a B (Bi-predictive) picture, the B picture will be described in more detail as follows.

The B picture does not necessarily have a constraint that the motion compensation must be performed with the past picture and the future picture temporally. Accordingly, the motion vector of the current block belonging to the B picture is independent of time or direction. In other words, since the B picture is obtained by referring to a plurality of pictures, there is a high possibility that the current block and the neighboring block have different types of motion vectors. Nevertheless, the motion vector of the current block belonging to the B picture can be encoded and decoded regardless of the type of motion vectors of neighboring blocks by the motion vector coding method and decoding method according to the present invention.

Since B pictures have four kinds of motion compensation modes, there are four kinds of motion vectors. Forward motion vector Forward MV (MVf), backward motion vector Backward MV (MVb), bidirectional motion vector Bi-predictive MV (MVf, MVb), and direct motion vector Direct MV. In the case of a direct motion vector, it is not necessary to encode and decode motion vector information since the motion vector information is not transmitted to the receiving end. Likewise, the remaining motion vectors are encoded or decoded using a predictive vector PMV obtained from motion vectors of neighboring blocks .

As described above, the motion vector of the current block belonging to the B picture is independent of the time or direction, and thus does not necessarily mean that the forward and backward words are necessarily separated by a specific time or direction. Both directions also need to include the past and the future based on the specific time or direction by distinguishing the specific time or direction, or both directions based on the specific point are not necessarily included.

In obtaining the prediction vector PMV, MVf and MVb use motion vectors of the same type as neighboring blocks, respectively. That is, MVf uses only neighboring MVfs in finding a prediction vector, and MVb uses only nearby MVbs. However, since the bidirectional motion vector has both of them, a necessary motion vector is used. Therefore, when setting the predictive vector PMV in coding or decoding the motion vector of the B picture, if the types of neighboring motion vectors are different, motion vectors of the same type can be predicted by the method described with reference to FIG. 9 and FIG.

7, MVb_B = (-1, -1), MVf_C = (0,3), MVb_C = (-1, -2) MVb_B = (-1, -1) is excluded from obtaining the intermediate value because MVb_B = (-1, -1) is different from the type of the motion vector of the current block, and (0,0) is substituted instead. Therefore, the intermediate value becomes (0, 3) and the difference value DMV_X becomes (1, -1). However, according to the present invention, the predicted (1, 1) instead of MVb_B = (-1, -1) is used to obtain the intermediate value. Therefore, the intermediate value becomes (1,1) and the difference value DMV_X becomes (0, 1).

On the other hand, the motion compensation block may have a rectangular shape as described above. In the case of a rectangular motion compensation block, the prediction direction of the motion vector can be known. Therefore, instead of using the intermediate value of the motion vectors of the neighboring three blocks described above as prediction vectors, prediction vectors predicted by other methods are used.

11 is a reference diagram for explaining a method of obtaining a prediction vector for a rectangular motion compensation block.

Referring to FIG. 11, when the motion compensation block is 8 × 16, the motion vector of the left block of the neighboring block is used as the predictive vector of the block 1, and the motion vector of the upper block is used as the prediction vector of the block do.

If the motion compensation block is 16 × 8, the motion vector of the upper block of the neighboring block is used as the prediction vector of the block ③, and the motion vector of the left block of the neighboring block is used as the prediction vector of the block ④.

When the motion compensation block is 8 × 4, the prediction vector of the block ⑤ is obtained by using the intermediate value of the previous block as it is, and the motion vector of the left block among the neighboring blocks is used as the prediction vector of the block ⑥.

If the motion compensation block is 4 × 8, the prediction vector of the block ⑦ is obtained by using the intermediate value of the previous block as it is, and the motion vector of the upper block among the neighboring blocks is used as the prediction vector of the block ⑧, respectively.

However, if the reference picture of the motion vector set as the predictive vector is different from the reference picture of the current block, the existing intermediate value is used. Other cases of exception are processed in the same manner as in the above-described intermediate value prediction.

The motion vector coding method and the decoding method described above can be created by a computer program. The codes and code segments that make up the program can be easily deduced by a computer programmer in the field. Also, the program is stored in a computer readable medium and read and executed by a computer to implement a motion vector coding method and a decoding method. The information storage medium includes a magnetic recording medium, an optical recording medium, and a carrier wave medium.

1 is a block diagram of a motion vector coding apparatus according to a preferred embodiment of the present invention.

FIG. 2 is a block diagram of an image data encoding apparatus including the motion vector encoding apparatus of FIG. 1 according to a preferred embodiment of the present invention;

3 shows an example of an input image,

4 is a block diagram of a motion vector decoding apparatus according to a preferred embodiment of the present invention.

FIG. 5 is a block diagram of a video data decoding apparatus including the motion vector decoding apparatus of FIG. 10 according to a preferred embodiment of the present invention;

6 is a reference diagram for explaining a multiple reference method according to a preferred embodiment of the present invention,

FIG. 7 is a reference view showing motion compensation blocks as units of motion compensation according to a preferred embodiment of the present invention;

8 is a reference diagram for explaining a case of obtaining a predicted motion vector according to a preferred embodiment of the present invention,

9 shows an example of a method of obtaining a predicted motion vector,

10 shows another example of a method of obtaining a predicted motion vector,

11 is a reference diagram for explaining a method of obtaining a prediction vector for a rectangular motion compensation block.

Claims (3)

A method for decoding a motion vector, Selecting a neighboring block having a motion vector to be used as a predicted motion vector of the current block according to a size and position of a current block included in the macroblock; And And selecting a motion vector of the selected neighboring block as a predicted motion vector of the current block, Wherein the step of selecting a neighboring block to be used as a predictive motion vector of the current block comprises: if the current block size in the macroblock is 16x8 and the current block is a lower block in the macroblock, And selecting a predictive motion vector of the current block as a predictive motion vector of the current block. The method according to claim 1, Reconstructing a difference value between the original motion vector of the current block and the predicted motion vector; And And adding the restored difference value to the predicted motion vector. An apparatus for decoding a motion vector, A motion vector decoding unit for decoding a difference value between a original motion vector of a current block and a predicted motion vector of the current block; And Selecting a neighboring block having a motion vector to be used as a predictive motion vector of the current block according to a size and a position of the current block included in the macroblock and selecting a motion vector of the selected neighboring block as a predictive motion vector of the current block And a motion vector prediction compensator for adding the selected predictive motion vector and the decoded difference value, The motion vector predictor and the motion vector predicting unit may calculate a motion vector of a neighboring block adjacent to the left of the current block as a predictive motion vector of the current block if the current block size of the macroblock is 16x8 and the current block is a lower block in the macroblock And a motion vector of the motion vector.

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