WO2017003063A1

WO2017003063A1 - Method for processing image based on inter prediction mode and system therefor

Info

Publication number: WO2017003063A1
Application number: PCT/KR2016/002034
Authority: WO
Inventors: 서정동; 박승욱; 임재현; 박내리; 김철근; 남정학
Original assignee: 엘지전자(주)
Priority date: 2015-06-28
Filing date: 2016-02-29
Publication date: 2017-01-05

Abstract

A method for processing an image on the basis of an inter prediction mode and a system therefor are disclosed. Specifically, the method for processing an image on the basis of an inter prediction comprises the steps of: determining whether or not an inter prediction using multiple motion parameters is applied to a block constituting an image; decoding the multiple motion parameters when the multiple motion parameters are used; and generating a prediction block for the block using the multiple motion parameters, wherein the multiple motion parameters can be defined with a plurality of motion parameters selected from a candidate list of single motion parameters.

Description

Inter prediction mode based image processing method and apparatus therefor

The present invention relates to a still image or moving image processing method, and more particularly, to a method for encoding / decoding a still image or moving image based on an inter prediction mode and an apparatus supporting the same.

Compression coding refers to a series of signal processing techniques for transmitting digitized information through a communication line or for storing in a form suitable for a storage medium. Media such as an image, an image, an audio, and the like may be a target of compression encoding. In particular, a technique of performing compression encoding on an image is called video image compression.

Next-generation video content will be characterized by high spatial resolution, high frame rate and high dimensionality of scene representation. Processing such content would result in a tremendous increase in terms of memory storage, memory access rate, and processing power.

Accordingly, there is a need to design coding tools for more efficiently processing next generation video content.

The present invention proposes a method of encoding / decoding video using multiple motion parameters in inter prediction (or inter picture prediction).

In addition, the present invention proposes a method for signaling multiple motion parameters usable in inter prediction (eg, merge mode or AMVP mode).

In addition, the present invention proposes a method for performing motion compensation using multiple motion parameters.

The technical problems to be achieved in the present invention are not limited to the technical problems mentioned above, and other technical problems not mentioned above will be clearly understood by those skilled in the art from the following description. Could be.

According to an aspect of the present invention, in a method of processing an image based on inter prediction, determining whether an inter prediction using a multi motion parameter is applied to a block constituting an image, wherein the multi motion parameter Is used, decoding the multiple motion parameters and generating a predictive block for the block using the multiple motion parameters, wherein the multiple motion parameters are a plurality of selected from a single motion parameter candidate list. It may be defined as a motion parameter.

An aspect of the present invention is an apparatus for processing an image based on inter prediction, wherein the multi-motion parameter application determining unit determines whether inter prediction using a multi-motion parameter is applied to a block constituting the image A motion parameter decoder for decoding the multiple motion parameters and a prediction block generator for generating a prediction block for the block using the multiple motion parameters when the multiple motion parameters are used. It may be defined as a plurality of motion parameters selected from a single motion parameter candidate list.

Preferably, the prediction block may be generated by overlapping pixel values of each reference block specified by each motion parameter included in the multi-motion parameter at the same ratio.

Preferably, the prediction block may be generated by overlapping pixel values to which a predetermined weight is applied for each reference block specified by each motion parameter included in the multi-motion parameter.

Preferably, the prediction block may be generated by overlapping a value to which a predetermined weight is applied for each pixel value of each reference block specified by each motion parameter included in the multiple motion parameter.

Preferably, the block is divided into a plurality of subblocks, and a prediction block may be generated for each subblock by using a motion parameter applied to each subblock among the multiple motion parameters.

Preferably, each motion parameter included in the multiple motion parameters may be applied to each subblock according to a z-scan order in a decoding order.

Preferably, a motion parameter applied to each subblock may be determined based on a correlation between each motion parameter included in the multiple motion parameter and a motion parameter of a neighboring block of each subblock.

Preferably, a motion parameter applied to each subblock may be determined based on a position of a candidate block corresponding to each motion parameter included in the multiple motion parameter.

Preferably, the candidate list index selected from the motion parameter candidate list is transmitted, and the multiple motion parameters can be decoded using the candidate list index.

Preferably, the number of candidate list indexes may be transmitted, and then the candidate list indexes may be sequentially transmitted.

Preferably, decoding of the candidate list index may be terminated when an end code for the candidate list index is transmitted.

Preferably, the candidate list index value may be transmitted in the case of the first motion parameter included in the multi-motion parameter, and the difference value from the previous candidate list index may be transmitted in the case of the second and subsequent motion parameters.

Preferably, the candidate list index selected from the motion parameter candidate list, the inter prediction mode indicating the inter prediction direction, the reference index indicating the reference picture, and the motion vector information are transmitted in one unit, and the candidate list index and the inter The multiple motion parameter may be decoded using a prediction mode, the reference index, and the motion vector information.

Preferably, the candidate list index, the inter prediction mode, the reference index, and the motion vector information are transmitted in the case of the first motion parameter included in the multi-motion parameter, and in the case of the second motion parameter, the inter prediction mode, The reference index and the motion vector information may be transmitted.

According to an embodiment of the present invention, the efficiency of motion compensation may be increased by performing inter prediction (or inter picture prediction) using multiple motion parameters.

In addition, according to an embodiment of the present invention, by performing inter prediction (or inter picture prediction) using multiple motion parameters, it is possible to increase the accuracy of inter prediction.

In addition, according to an embodiment of the present invention, by performing inter prediction (or inter-picture prediction) using multiple motion parameters, the amount of residual signal is reduced and the overall video encoding efficiency can be increased.

The effects obtainable in the present invention are not limited to the above-mentioned effects, and other effects not mentioned will be clearly understood by those skilled in the art from the following description. .

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, included as part of the detailed description in order to provide a thorough understanding of the present invention, provide embodiments of the present invention and together with the description, describe the technical features of the present invention.

1 is a schematic block diagram of an encoder in which encoding of a still image or video signal is performed according to an embodiment to which the present invention is applied.

2 is a schematic block diagram of a decoder in which encoding of a still image or video signal is performed according to an embodiment to which the present invention is applied.

3 is a diagram for describing a partition structure of a coding unit that may be applied to the present invention.

4 is a diagram for explaining a prediction unit applicable to the present invention.

5 is a diagram illustrating a direction of inter prediction as an embodiment to which the present invention may be applied.

6 illustrates integer and fractional sample positions for quarter sample interpolation, as an embodiment to which the present invention may be applied.

7 illustrates a position of a spatial candidate as an embodiment to which the present invention may be applied.

8 is a diagram illustrating an inter prediction method as an embodiment to which the present invention is applied.

9 is a diagram illustrating a motion compensation process as an embodiment to which the present invention may be applied.

10 is a diagram illustrating a method of using multiple motion parameters in a merge mode according to an embodiment of the present invention.

11 is a diagram illustrating a method of using multiple motion parameters in an AMVP mode according to an embodiment of the present invention.

12 is a diagram illustrating a decoding process in an inter prediction mode using multiple parameters according to an embodiment of the present invention.

13 is a diagram illustrating a motion compensation method using multiple motion parameters according to an embodiment of the present invention.

14 is a diagram illustrating a method of calculating similarity between a current block and a reference block when motion compensation using multiple motion parameters according to an embodiment of the present invention.

FIG. 15 is a diagram illustrating a method of calculating pixel weights in motion compensation using multiple motion parameters according to an embodiment of the present invention.

16 is a diagram illustrating a motion compensation method using multiple motion parameters according to an embodiment of the present invention.

FIG. 17 illustrates a non-square division of a current block when motion compensation is applied by applying four multiple motion parameters according to an embodiment of the present invention.

18 is a diagram illustrating a non-square division method of the current block when motion compensation is applied by applying four multiple motion parameters according to an embodiment of the present invention.

FIG. 19 illustrates a non-square division of a current block when motion compensation is applied by applying four multiple motion parameters according to an embodiment of the present invention.

FIG. 20 illustrates a split form of a current block when motion compensation is performed by applying three multi-motion parameters according to an embodiment of the present invention.

FIG. 21 is a diagram illustrating a method of deriving a partitioned shape of a current processing block using neighboring pixel values according to an embodiment of the present invention.

22 is a diagram illustrating a motion compensation method using multiple motion parameters according to an embodiment of the present invention.

23 is a diagram illustrating a motion compensation method using multiple motion parameters according to an embodiment of the present invention.

24 is a diagram more specifically illustrating an inter predictor according to an embodiment of the present invention.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. The detailed description, which will be given below with reference to the accompanying drawings, is intended to explain exemplary embodiments of the present invention and is not intended to represent the only embodiments in which the present invention may be practiced. The following detailed description includes specific details in order to provide a thorough understanding of the present invention. However, one of ordinary skill in the art appreciates that the present invention may be practiced without these specific details.

In some instances, well-known structures and devices may be omitted or shown in block diagram form centering on the core functions of the structures and devices in order to avoid obscuring the concepts of the present invention.

In addition, the terminology used in the present invention was selected as a general term widely used as possible now, in a specific case will be described using terms arbitrarily selected by the applicant. In such a case, since the meaning is clearly described in the detailed description of the part, it should not be interpreted simply by the name of the term used in the description of the present invention, and it should be understood that the meaning of the term should be interpreted. .

Specific terms used in the following description are provided to help the understanding of the present invention, and the use of such specific terms may be changed to other forms without departing from the technical spirit of the present invention. For example, signals, data, samples, pictures, frames, blocks, etc. may be appropriately replaced and interpreted in each coding process.

Hereinafter, in the present specification, the 'processing unit' refers to a unit in which a process of encoding / decoding such as prediction, transformation, and / or quantization is performed. Hereinafter, for convenience of description, the processing unit may be referred to as a 'unit', 'processing block' or 'block'.

The processing unit may be interpreted to include a unit for the luma component and a unit for the chroma component. For example, the processing unit may correspond to a Coding Tree Unit (CTU), a Coding Unit (CU), a Prediction Unit (PU), or a Transform Unit (TU).

In addition, the processing unit may be interpreted as a unit for a luma component or a unit for a chroma component. For example, the processing unit may be a coding tree block (CTB), a coding block (CB), a prediction block (PB), or a transform block (TB) for a luma component. May correspond to. Or, it may correspond to a coding tree block (CTB), a coding block (CB), a prediction block (PU), or a transform block (TB) for a chroma component.

In addition, the processing unit is not necessarily limited to square blocks, but may also be configured in a polygonal form having three or more vertices.

In addition, in the present specification, the transmission or reception of specific data or information may be interpreted to mean that corresponding data or information is included in a bitstream composed of an encoded image and data related to encoding.

본 발명이 적용될 수 있는 장치 일반General apparatus to which the present invention can be applied

Referring to FIG. 1, the encoder 100 may include an image divider 110, a subtractor 115, a transform unit 120, a quantizer 130, an inverse quantizer 140, an inverse transform unit 150, and a filtering unit. 160, a decoded picture buffer (DPB) 170, a predictor 180, and an entropy encoder 190. The predictor 180 may include an inter predictor 181 and an intra predictor 182.

The image divider 110 divides an input video signal (or a picture or a frame) input to the encoder 100 into one or more processing units.

The subtractor 115 subtracts the difference from the prediction signal (or prediction block) output from the prediction unit 180 (that is, the inter prediction unit 181 or the intra prediction unit 182) in the input image signal. Generate a residual signal (or difference block). The generated difference signal (or difference block) is transmitted to the converter 120.

The transform unit 120 may convert a differential signal (or a differential block) into a transform scheme (eg, a discrete cosine transform (DCT), a discrete sine transform (DST), a graph-based transform (GBT), and a karhunen-loeve transform (KLT)). Etc.) to generate transform coefficients. In this case, the transform unit 120 may generate transform coefficients by performing a transform using a transform mode determined according to the prediction mode applied to the difference block and the size of the difference block.

The quantization unit 130 quantizes the transform coefficients and transmits the transform coefficients to the entropy encoding unit 190, and the entropy encoding unit 190 entropy codes the quantized signals and outputs them as bit streams.

Meanwhile, the quantized signal output from the quantization unit 130 may be used to generate a prediction signal. For example, the quantized signal may recover the differential signal by applying inverse quantization and inverse transformation through an inverse quantization unit 140 and an inverse transformation unit 150 in a loop. A reconstructed signal may be generated by adding the reconstructed difference signal to a prediction signal output from the inter predictor 181 or the intra predictor 182.

Meanwhile, in the compression process as described above, adjacent blocks are quantized by different quantization parameters, thereby causing deterioration of the block boundary. This phenomenon is called blocking artifacts, which is one of the important factors in evaluating image quality. In order to reduce such deterioration, a filtering process may be performed. Through this filtering process, the image quality can be improved by removing the blocking degradation and reducing the error of the current picture.

The filtering unit 160 applies filtering to the reconstruction signal and outputs it to the reproduction apparatus or transmits the decoded picture buffer to the decoding picture buffer 170. The filtered signal transmitted to the decoded picture buffer 170 may be used as the reference picture in the inter prediction unit 181. As such, by using the filtered picture as a reference picture in the inter prediction mode, not only image quality but also encoding efficiency may be improved.

The decoded picture buffer 170 may store the filtered picture for use as a reference picture in the inter prediction unit 181.

The inter prediction unit 181 performs temporal prediction and / or spatial prediction to remove temporal redundancy and / or spatial redundancy with reference to a reconstructed picture.

In particular, the inter prediction unit 181 according to the present invention may further include a configuration for performing inter prediction using multiple motion parameters. Detailed description thereof will be described later.

Here, since the reference picture used to perform the prediction is a transformed signal that has been quantized and dequantized in units of blocks at the time of encoding / decoding in the previous time, blocking artifacts or ringing artifacts may exist. have.

Accordingly, the inter prediction unit 181 may interpolate the signals between pixels in sub-pixel units by applying a lowpass filter to solve performance degradation due to discontinuity or quantization of such signals. Herein, the sub-pixels mean virtual pixels generated by applying an interpolation filter, and the integer pixels mean actual pixels existing in the reconstructed picture. As the interpolation method, linear interpolation, bi-linear interpolation, wiener filter, or the like may be applied.

The interpolation filter may be applied to a reconstructed picture to improve the precision of prediction. For example, the inter prediction unit 181 generates an interpolation pixel by applying an interpolation filter to integer pixels, and uses an interpolated block composed of interpolated pixels as a prediction block. You can make predictions.

The intra predictor 182 predicts the current block by referring to samples in the vicinity of the block to which the current encoding is to be performed. The intra prediction unit 182 may perform the following process to perform intra prediction. First, reference samples necessary for generating a prediction signal may be prepared. The prediction signal may be generated using the prepared reference sample. Then, the prediction mode is encoded. In this case, the reference sample may be prepared through reference sample padding and / or reference sample filtering. Since the reference sample has been predicted and reconstructed, there may be a quantization error. Accordingly, the reference sample filtering process may be performed for each prediction mode used for intra prediction to reduce such an error.

The prediction signal (or prediction block) generated by the inter prediction unit 181 or the intra prediction unit 182 is used to generate a reconstruction signal (or reconstruction block) or a differential signal (or differential block). It can be used to generate.

2, the decoder 200 includes an entropy decoding unit 210, an inverse quantization unit 220, an inverse transform unit 230, an adder 235, a filtering unit 240, and a decoded picture buffer (DPB). Buffer Unit (250), the prediction unit 260 may be configured. The predictor 260 may include an inter predictor 261 and an intra predictor 262.

The reconstructed video signal output through the decoder 200 may be reproduced through the reproducing apparatus.

The decoder 200 receives a signal (ie, a bit stream) output from the encoder 100 of FIG. 1, and the received signal is entropy decoded through the entropy decoding unit 210.

The inverse quantization unit 220 obtains a transform coefficient from the entropy decoded signal using the quantization step size information.

The inverse transform unit 230 applies an inverse transform scheme to inverse transform the transform coefficients to obtain a residual signal (or a differential block).

The adder 235 outputs the obtained difference signal (or difference block) from the prediction unit 260 (that is, the prediction signal (or prediction block) output from the inter prediction unit 261 or the intra prediction unit 262. ) Generates a reconstructed signal (or a reconstruction block).

The filtering unit 240 applies filtering to the reconstructed signal (or the reconstructed block) and outputs the filtering to the reproduction device or transmits the decoded picture buffer unit 250 to the reproduction device. The filtered signal transmitted to the decoded picture buffer unit 250 may be used as a reference picture in the inter predictor 261.

In the present specification, the embodiments described by the filtering unit 160, the inter prediction unit 181, and the intra prediction unit 182 of the encoder 100 are respectively the filtering unit 240, the inter prediction unit 261, and the decoder of the decoder. The same may be applied to the intra predictor 262.

In particular, the inter prediction unit 261 according to the present invention may further include a configuration for performing inter prediction using multiple motion parameters. Detailed description thereof will be described later.

처리 유닛 분할 구조Processing unit split structure

In general, a still image or video compression technique (eg, HEVC) uses a block-based image compression method. The block-based image compression method is a method of processing an image by dividing the image into specific block units, and may reduce memory usage and calculation amount.

The encoder splits one image (or picture) into units of a coding tree unit (CTU) in a rectangular shape. In addition, one CTU is sequentially encoded according to a raster scan order.

In HEVC, the size of the CTU may be set to any one of 64 × 64, 32 × 32, and 16 × 16. The encoder may select and use the size of the CTU according to the resolution of the input video or the characteristics of the input video. The CTU includes a coding tree block (CTB) for luma components and a CTB for two chroma components corresponding thereto.

One CTU may be divided into a quad-tree structure. That is, one CTU has a square shape and is divided into four units having a half horizontal size and a half vertical size to generate a coding unit (CU). have. This partitioning of the quad-tree structure can be performed recursively. That is, a CU is hierarchically divided into quad-tree structures from one CTU.

CU refers to a basic unit of coding in which an input image is processed, for example, intra / inter prediction is performed. The CU includes a coding block (CB) for a luma component and a CB for two chroma components corresponding thereto. In HEVC, the size of a CU may be set to any one of 64 × 64, 32 × 32, 16 × 16, and 8 × 8.

Referring to FIG. 3, the root node of the quad-tree is associated with the CTU. The quad-tree is split until it reaches a leaf node, which corresponds to a CU.

More specifically, the CTU corresponds to a root node and has a smallest depth (ie, depth = 0). The CTU may not be divided according to the characteristics of the input image. In this case, the CTU corresponds to a CU.

The CTU may be divided into quad tree shapes, resulting in lower nodes having a depth of 1 (depth = 1). In addition, a node that is no longer divided (ie, a leaf node) in a lower node having a depth of 1 corresponds to a CU. For example, in FIG. 3 (b), CU (a), CU (b), and CU (j) corresponding to nodes a, b, and j are divided once in the CTU and have a depth of one.

At least one of the nodes having a depth of 1 may be split into a quad tree again, resulting in lower nodes having a depth of 1 (ie, depth = 2). In addition, a node (ie, a leaf node) that is no longer divided in a lower node having a depth of 2 corresponds to a CU. For example, in FIG. 3 (b), CU (c), CU (h) and CU (i) corresponding to nodes c, h and i are divided twice in the CTU and have a depth of two.

In addition, at least one of the nodes having a depth of 2 may be divided into quad tree shapes, resulting in lower nodes having a depth of 3 (ie, depth = 3). And, a node that is no longer partitioned (ie, a leaf node) in a lower node having a depth of 3 corresponds to a CU. For example, in FIG. 3 (b), CU (d), CU (e), CU (f), and CU (g) corresponding to nodes d, e, f, and g are divided three times in the CTU, Has depth.

In the encoder, the maximum size or the minimum size of the CU may be determined according to characteristics (eg, resolution) of the video image or in consideration of encoding efficiency. Information about this or information capable of deriving the information may be included in the bitstream. A CU having a maximum size may be referred to as a largest coding unit (LCU), and a CU having a minimum size may be referred to as a smallest coding unit (SCU).

In addition, a CU having a tree structure may be hierarchically divided with predetermined maximum depth information (or maximum level information). Each partitioned CU may have depth information. Since the depth information indicates the number and / or degree of division of the CU, the depth information may include information about the size of the CU.

Since the LCU is divided into quad tree shapes, the size of the SCU can be obtained by using the size and maximum depth information of the LCU. Or conversely, using the size of the SCU and the maximum depth information of the tree, the size of the LCU can be obtained.

For one CU, information indicating whether the corresponding CU is split (for example, a split CU flag split_cu_flag) may be transmitted to the decoder. This split mode is included in all CUs except the SCU. For example, if the flag indicating whether to split or not is '1', the CU is divided into 4 CUs again. If the flag indicating whether to split or not is '0', the CU is not divided further. Processing may be performed.

As described above, a CU is a basic unit of coding in which intra prediction or inter prediction is performed. HEVC divides a CU into prediction units (PUs) in order to code an input image more effectively.

The PU is a basic unit for generating a prediction block, and may generate different prediction blocks in PU units within one CU. However, PUs belonging to one CU are not mixed with intra prediction and inter prediction, and PUs belonging to one CU are coded by the same prediction method (ie, intra prediction or inter prediction).

The PU is not divided into quad-tree structures, but is divided once in a predetermined form in one CU. This will be described with reference to the drawings below.

The PU is divided differently according to whether an intra prediction mode or an inter prediction mode is used as a coding mode of a CU to which the PU belongs.

FIG. 4A illustrates a PU when an intra prediction mode is used, and FIG. 4B illustrates a PU when an inter prediction mode is used.

Referring to FIG. 4 (a), assuming that a size of one CU is 2N × 2N (N = 4,8,16,32), one CU has two types (ie, 2N × 2N or N). XN).

Here, when divided into 2N × 2N type PU, it means that only one PU exists in one CU.

On the other hand, when divided into N × N type PU, one CU is divided into four PUs, and different prediction blocks are generated for each PU unit. However, the division of the PU may be performed only when the size of the CB for the luminance component of the CU is the minimum size (that is, the CU is the SCU).

Referring to FIG. 4 (b), assuming that a size of one CU is 2N × 2N (N = 4,8,16,32), one CU has 8 PU types (ie, 2N × 2N). , N × N, 2N × N, N × 2N, nL × 2N, nR × 2N, 2N × nU, 2N × nD).

Similar to intra prediction, PU partitioning in the form of N × N may be performed only when the size of the CB for the luminance component of the CU is the minimum size (that is, the CU is the SCU).

In inter prediction, 2N × N splitting in the horizontal direction and N × 2N splitting in the vertical direction are supported.

In addition, it supports PU partitions of nL × 2N, nR × 2N, 2N × nU, and 2N × nD types, which are Asymmetric Motion Partition (AMP). Here, 'n' means a 1/4 value of 2N. However, AMP cannot be used when the CU to which the PU belongs is a CU of the minimum size.

In order to efficiently encode an input image within one CTU, an optimal partitioning structure of a coding unit (CU), a prediction unit (PU), and a transformation unit (TU) is subjected to the following process to perform a minimum rate-distortion. It can be determined based on the value. For example, looking at the optimal CU partitioning process in 64 × 64 CTU, rate-distortion cost can be calculated while partitioning from a 64 × 64 CU to an 8 × 8 CU. The specific process is as follows.

1) The partition structure of the optimal PU and TU that generates the minimum rate-distortion value is determined by performing inter / intra prediction, transform / quantization, inverse quantization / inverse transform, and entropy encoding for a 64 × 64 CU.

2) Divide the 64 × 64 CU into four 32 × 32 CUs and determine the optimal PU and TU partitioning structure that generates the minimum rate-distortion value for each 32 × 32 CU.

3) The 32 × 32 CU is subdivided into four 16 × 16 CUs, and a partition structure of an optimal PU and TU that generates a minimum rate-distortion value for each 16 × 16 CU is determined.

4) Subdivide the 16 × 16 CU into four 8 × 8 CUs and determine the optimal PU and TU partitioning structure that generates the minimum rate-distortion value for each 8 × 8 CU.

5) 16 × 16 blocks by comparing the sum of the rate-distortion values of the 16 × 16 CUs calculated in 3) above with the rate-distortion values of the four 8 × 8 CUs calculated in 4) above. Determine the partition structure of the optimal CU within. This process is similarly performed for the remaining three 16 × 16 CUs.

6) 32 × 32 block by comparing the sum of the rate-distortion values of the 32 × 32 CUs calculated in 2) above with the rate-distortion values of the four 16 × 16 CUs obtained in 5) above. Determine the partition structure of the optimal CU within. Do this for the remaining three 32x32 CUs.

7) Finally, compare the sum of the rate-distortion values of the 64 × 64 CUs calculated in step 1) with the rate-distortion values of the four 32 × 32 CUs obtained in step 6). The partition structure of the optimal CU is determined within the x64 block.

In the intra prediction mode, a prediction mode is selected in units of PUs, and prediction and reconstruction are performed in units of actual TUs for the selected prediction mode.

TU means a basic unit in which actual prediction and reconstruction are performed. The TU includes a transform block (TB) for a luma component and a TB for two chroma components corresponding thereto.

In the example of FIG. 3, as one CTU is divided into quad-tree structures to generate CUs, the TUs are hierarchically divided into quad-tree structures from one CU to be coded.

Since the TU is divided into quad-tree structures, the TU divided from the CU can be further divided into smaller lower TUs. In HEVC, the size of the TU may be set to any one of 32 × 32, 16 × 16, 8 × 8, and 4 × 4.

Referring again to FIG. 3, it is assumed that a root node of the quad-tree is associated with a CU. The quad-tree is split until it reaches a leaf node, which corresponds to a TU.

In more detail, a CU corresponds to a root node and has a smallest depth (that is, depth = 0). The CU may not be divided according to the characteristics of the input image. In this case, the CU corresponds to a TU.

The CU may be divided into quad tree shapes, resulting in lower nodes having a depth of 1 (depth = 1). In addition, a node (ie, a leaf node) that is no longer divided in a lower node having a depth of 1 corresponds to a TU. For example, in FIG. 3B, TU (a), TU (b), and TU (j) corresponding to nodes a, b, and j are divided once in a CU and have a depth of 1. FIG.

At least one of the nodes having a depth of 1 may be split into a quad tree again, resulting in lower nodes having a depth of 1 (ie, depth = 2). In addition, a node (ie, a leaf node) that is no longer divided in a lower node having a depth of 2 corresponds to a TU. For example, in FIG. 3B, TU (c), TU (h), and TU (i) corresponding to nodes c, h, and i are divided twice in a CU and have a depth of two.

In addition, at least one of the nodes having a depth of 2 may be divided into quad tree shapes, resulting in lower nodes having a depth of 3 (ie, depth = 3). And, a node that is no longer partitioned (ie, a leaf node) in a lower node having a depth of 3 corresponds to a CU. For example, in FIG. 3 (b), TU (d), TU (e), TU (f), and TU (g) corresponding to nodes d, e, f, and g are divided three times in a CU. Has depth.

A TU having a tree structure may be hierarchically divided with predetermined maximum depth information (or maximum level information). Each divided TU may have depth information. Since the depth information indicates the number and / or degree of division of the TU, it may include information about the size of the TU.

For one TU, information indicating whether the corresponding TU is split (for example, split TU flag split_transform_flag) may be delivered to the decoder. This partitioning information is included in all TUs except the smallest TU. For example, if the value of the flag indicating whether to split is '1', the corresponding TU is divided into four TUs again. If the value of the flag indicating whether to split is '0', the corresponding TU is no longer divided.

예측(prediction)Prediction

The decoded portion of the current picture or other pictures in which the current processing unit is included may be used to reconstruct the current processing unit in which decoding is performed.

Intra picture or I picture (slice), which uses only the current picture for reconstruction, i.e. performs only intra picture prediction, predicts a picture (slice) using at most one motion vector and reference index to predict each unit A picture using a predictive picture or P picture (slice), up to two motion vectors, and a reference index (slice) may be referred to as a bi-predictive picture or a B picture (slice).

Intra prediction means a prediction method that derives the current processing block from data elements (eg, sample values, etc.) of the same decoded picture (or slice). That is, a method of predicting pixel values of the current processing block by referring to reconstructed regions in the current picture.

Hereinafter, the inter prediction will be described in more detail.

Inter Inter prediction (or inter screen prediction)

Inter prediction means a prediction method of deriving a current processing block based on data elements (eg, sample values or motion vectors, etc.) of pictures other than the current picture. That is, a method of predicting pixel values of the current processing block by referring to reconstructed regions in other reconstructed pictures other than the current picture.

Inter prediction (or inter picture prediction) is a technique for removing redundancy existing between pictures, and is mostly performed through motion estimation and motion compensation.

Referring to FIG. 5, inter prediction includes uni-directional prediction that uses only one past picture or a future picture as a reference picture on a time axis with respect to one block, and bidirectional prediction that simultaneously refers to past and future pictures. Bi-directional prediction).

In addition, uni-directional prediction includes forward direction prediction using one reference picture displayed (or output) before the current picture in time and 1 displayed (or output) after the current picture in time. It can be divided into backward direction prediction using two reference pictures.

The motion parameter (or information) used to specify which reference region (or reference block) is used to predict the current block in the inter prediction process (i.e., unidirectional or bidirectional prediction) is an inter prediction mode (where The inter prediction mode may indicate a reference direction (i.e., unidirectional or bidirectional) and a reference list (i.e., L0, L1 or bidirectional), a reference index (or reference picture index or reference list index), Contains motion vector information. The motion vector information may include a motion vector, a motion vector prediction (MVP), or a motion vector difference (MVD). The motion vector difference value means a difference value between the motion vector and the motion vector prediction value.

For unidirectional prediction, motion parameters for one direction are used. That is, one motion parameter may be needed to specify the reference region (or reference block).

Bidirectional prediction uses motion parameters for both directions. In the bidirectional prediction method, up to two reference regions may be used. The two reference regions may exist in the same reference picture or may exist in different pictures, respectively. That is, up to two motion parameters may be used in the bidirectional prediction scheme, and two motion vectors may have the same reference picture index or different reference picture indexes. In this case, all of the reference pictures may be displayed (or output) before or after the current picture in time.

The encoder performs motion estimation to find the reference region most similar to the current processing block from the reference pictures in the inter prediction process. In addition, the encoder may provide a decoder with a motion parameter for the reference region.

The encoder / decoder may obtain a reference region of the current processing block using the motion parameter. The reference region exists in a reference picture having the reference index. In addition, the pixel value or interpolated value of the reference region specified by the motion vector may be used as a predictor of the current processing block. That is, using motion information, motion compensation is performed to predict an image of a current processing block from a previously decoded picture.

In order to reduce the amount of transmission associated with the motion vector information, a method of acquiring a motion vector prediction value mvp using motion information of previously coded blocks and transmitting only a difference value mvd thereof may be used. That is, the decoder obtains a motion vector prediction value of the current processing block using motion information of other decoded blocks, and obtains a motion vector value for the current processing block using the difference value transmitted from the encoder. In obtaining the motion vector prediction value, the decoder may obtain various motion vector candidate values by using motion information of other blocks that are already decoded, and obtain one of them as the motion vector prediction value.

Reference picture set and reference picture list

To manage multiple reference pictures, a set of previously decoded pictures are stored in a decoded picture buffer (DPB) for decoding the remaining pictures.

The reconstructed picture used for inter prediction among the reconstructed pictures stored in the DPB is referred to as a reference picture. In other words, a reference picture refers to a picture including a sample that can be used for inter prediction in a decoding process of a next picture in decoding order.

A reference picture set (RPS) refers to a set of reference pictures associated with a picture, and is composed of all pictures previously associated in decoding order. The reference picture set may be used for inter prediction of an associated picture or a picture following an associated picture in decoding order. That is, reference pictures maintained in the decoded picture buffer DPB may be referred to as a reference picture set. The encoder may provide the decoder with reference picture set information in a sequence parameter set (SPS) (ie, a syntax structure composed of syntax elements) or each slice header.

A reference picture list refers to a list of reference pictures used for inter prediction of a P picture (or slice) or a B picture (or slice). Here, the reference picture list may be divided into two reference picture lists, and may be referred to as reference picture list 0 (or L0) and reference picture list 1 (or L1), respectively. Also, a reference picture belonging to reference picture list 0 may be referred to as reference picture 0 (or L0 reference picture), and a reference picture belonging to reference picture list 1 may be referred to as reference picture 1 (or L1 reference picture).

In the decoding process of P pictures (or slices), one reference picture list (i.e., reference picture list 0) is used, and in the decoding process of B pictures (or slices), two reference picture lists (i.e., reference) Picture list 0 and reference picture list 1) may be used. Such information for distinguishing a reference picture list for each reference picture may be provided to the decoder through reference picture set information. The decoder adds the reference picture to the reference picture list 0 or the reference picture list 1 based on the reference picture set information.

A reference picture index (or reference index) is used to identify any one specific reference picture in the reference picture list.

Fractional sample interpolation

A sample of the prediction block for the inter predicted current processing block is obtained from the sample value of the corresponding reference region in the reference picture identified by the reference picture index. Here, the corresponding reference region in the reference picture represents the region of the position indicated by the horizontal component and the vertical component of the motion vector. Fractional sample interpolation is used to generate predictive samples for noninteger sample coordinates, except when the motion vector has an integer value. For example, a motion vector of one quarter of the distance between samples may be supported.

For HEVC, fractional sample interpolation of luminance components applies an 8-tap filter in the horizontal and vertical directions, respectively. In addition, fractional sample interpolation of the color difference component applies a 4-tap filter in the horizontal direction and the vertical direction, respectively.

Referring to FIG. 6, the shaded block in which the upper-case letter (A_i, j) is written indicates the integer sample position, and the shaded block in which the lower-case letter (x_i, j) is written is the fractional sample position. Indicates.

Fractional samples are generated by applying interpolation filters to integer sample values in the horizontal and vertical directions, respectively. For example, in the horizontal direction, an 8-tap filter may be applied to four integer sample values on the left side and four integer sample values on the right side based on the fractional sample to be generated.

Inter prediction mode

In HEVC, a merge mode and advanced motion vector prediction (AMVP) may be used to reduce the amount of motion information.

1) Merge Mode

Merge mode refers to a method of deriving a motion parameter (or information) from a neighboring block spatially or temporally.

The set of candidates available in merge mode is composed of spatial neighbor candidates, temporal candidates and generated candidates.

Referring to FIG. 7A, it is determined whether each spatial candidate block is available according to the order of {A1, B1, B0, A0, B2}. In this case, when the candidate block is encoded in the intra prediction mode and there is no motion information, or when the candidate block is located outside the current picture (or slice), the candidate block is not available.

After determining the validity of the spatial candidate, the spatial merge candidate can be constructed by excluding unnecessary candidate blocks from candidate blocks of the current processing block. For example, when the candidate block of the current prediction block is the first prediction block in the same coding block, the candidate block having the same motion information may be excluded except for the corresponding candidate block.

When the spatial merge candidate configuration is completed, the temporal merge candidate configuration process is performed in the order of {T0, T1}.

In the temporal candidate configuration, when the right bottom block T0 of the collocated block of the reference picture is available, the block is configured as a temporal merge candidate. The colocated block refers to a block existing at a position corresponding to the current processing block in the selected reference picture. On the other hand, otherwise, the block T1 located at the center of the collocated block is configured as a temporal merge candidate.

The maximum number of merge candidates may be specified in the slice header. If the number of merge candidates is larger than the maximum number, the number of spatial candidates and temporal candidates smaller than the maximum number is maintained. Otherwise, the number of merge candidates is generated by combining the candidates added so far until the maximum number of candidates becomes the maximum (ie, combined bi-predictive merging candidates). .

The encoder constructs a merge candidate list in the above manner and performs motion estimation to merge candidate block information selected from the merge candidate list into a merge index (for example, merge_idx [x0] [y0] '). Signal to the decoder. In FIG. 7B, the B1 block is selected from the merge candidate list. In this case, “index 1” may be signaled to the decoder as a merge index.

The decoder constructs a merge candidate list similarly to the encoder, and derives the motion information for the current prediction block from the motion information of the candidate block corresponding to the merge index received from the encoder in the merge candidate list. The decoder generates a prediction block for the current processing block based on the derived motion information (ie, motion compensation).

2) Advanced Motion Vector Prediction (AMVP) Mode

The AMVP mode refers to a method of deriving a motion vector prediction value from neighboring blocks. Thus, horizontal and vertical motion vector difference (MVD), reference index, and inter prediction modes are signaled to the decoder. The horizontal and vertical motion vector values are calculated using the derived motion vector prediction value and the motion vector difference (MVD) provided from the encoder.

That is, the encoder constructs a motion vector predictor candidate list and performs motion estimation to perform a motion estimation flag (ie, candidate block information) selected from the motion vector predictor candidate list (for example, mvp_lX_flag [x0] [y0). ] ') Is signaled to the decoder. The decoder constructs a motion vector predictor candidate list similarly to the encoder, and derives a motion vector predictor of the current processing block using the motion information of the candidate block indicated by the motion reference flag received from the encoder in the motion vector predictor candidate list. The decoder obtains a motion vector value for the current processing block by using the derived motion vector prediction value and the motion vector difference value transmitted from the encoder. The decoder generates a prediction block for the current processing block based on the derived motion information (ie, motion compensation).

In the AMVP mode, two spatial motion candidates are selected from among the five available candidates in FIG. 7. The first spatial motion candidate is selected from the set of {A0, A1} located on the left side, and the second spatial motion candidate is selected from the set of {B0, B1, B2} located above. At this time, when the reference index of the neighboring candidate block is not the same as the current prediction block, the motion vector is scaled.

If the number of candidates selected as a result of the search for the spatial motion candidate is two, the candidate configuration is terminated, but if less than two, the temporal motion candidate is added.

Referring to FIG. 8, a decoder (in particular, the inter prediction unit 261 of the decoder in FIG. 2) decodes a motion parameter for a processing block (eg, a prediction unit) (S801).

For example, if the processing block has a merge mode applied, the decoder may decode the merge index signaled from the encoder. The motion parameter of the current processing block can be derived from the motion parameter of the candidate block indicated by the merge index.

In addition, when the processing block is applied with the AMVP mode, the decoder may decode horizontal and vertical motion vector difference (MVD), reference index, and inter prediction mode signaled from the encoder. The motion vector prediction value may be derived from the motion parameter of the candidate block indicated by the motion reference flag, and the motion vector value of the current processing block may be derived using the motion vector prediction value and the received motion vector difference value.

The decoder performs motion compensation on the prediction unit by using the decoded motion parameter (or information) (S802).

That is, the encoder / decoder performs motion compensation that predicts an image of the current unit from a previously decoded picture by using the decoded motion parameter.

9 illustrates a case in which a motion parameter for a current block to be encoded in a current picture is unidirectional prediction, a second picture in LIST0, LIST0, and a motion vector (-a, b). do.

In this case, as shown in FIG. 9, the current block is predicted using values of positions (ie, sample values of reference blocks) that are separated from the current block by (-a, b) in the second picture of LIST0.

In the case of bidirectional prediction, another reference list (eg, LIST1), a reference index, and a motion vector difference value are transmitted so that the decoder derives two reference blocks and predicts the current block value based on the reference block.

다중 움직임 파라미터를 이용한 Using multiple motion parameters 인터Inter 예측 방법 Forecast method

The present invention proposes a method for performing inter prediction (ie, motion estimation / compensation) using multiple motion parameters for one block.

Hereinafter, in the description of the present invention, a list consisting of candidates of motion parameters available for deriving a motion parameter for the current processing block is referred to as a motion parameter candidate list (eg, a merge candidate list in the case of merge mode. candidate list) or motion vector predictor candidate list in the AMVP mode.

In the following description of the present invention, an index indicating a motion parameter selected by a transmitting end (ie, an encoder) in the 'motion parameter candidate list' is referred to as a 'candidate list index (for example, in the case of merge mode, a merging candidate index ( merging candidate index (or merge index) or available flag (availablility flag) in the AMVP mode.

In addition, in the following description of the present invention, 'multiple motion parameters' means a plurality of motion parameters selected (or found) from a single 'reference picture list'.

Multiple motion parameters Signaling Way

According to an embodiment of the present invention, a method of signaling a multi-motion parameter when a merge mode, which is a technique of constructing a candidate list with neighboring motion parameters and transmitting only an index of the candidate list, is applied.

FIG. 10 illustrates a case where B1 and A0 are selected as multiple motion parameters in a state where a motion parameter candidate list (that is, a merge candidate list) is configured.

In this case, in order to transmit the multiple motion parameters selected by the transmitting end (ie, the encoder) to the receiving end (ie, the decoder), the decoder must know the number of motion parameters transmitted from the encoder. That is, the encoder may inform the decoder of the number of multiple motion parameters transmitted or the number of multiple motion parameters may be predetermined.

For example, in the case of FIG. 10, since B1 and A0 are selected as the multi-motion parameters, the decoder may select two motion parameters from the encoder (ie, each candidate list index indicating two motion parameters selected in the motion parameter candidate list). It should be noted that will be sent.

To this end, the following methods can be used.

1) The encoder may first transmit the number of candidate list indexes (ie, the number of multiple motion parameters) to the decoder, and then sequentially transmit each candidate list index to the decoder.

2) Alternatively, the number of candidate list indexes to be transmitted to the decoder may be predetermined so that the encoder and the decoder may know each other. In this case, the encoder may transmit a predetermined number of respective candidate list indexes to the decoder.

3) Alternatively, the encoder may preset an end code of candidate list index encoding and transmit all candidate list indexes to the decoder before inserting the end code. That is, the end code can be inserted into the next bit (column) of all candidate list indices.

4) Or, the encoder sets the maximum number of candidate list indexes to be transmitted and the end code of the candidate list index encoding. If the number of candidate list indexes to be transmitted reaches the maximum number, the encoder finishes the transmission without transmitting the end code to the decoder. You may. Even in this case, if the number of candidate list indexes to be transmitted does not reach the maximum number, the encoder may preset the end code of the candidate list index encoding and transmit all the candidate list indexes to the decoder before inserting the end code.

The encoder transmits a candidate list index for indicating each motion parameter to the decoder. The following methods may be used for this purpose.

For example, in the case of FIG. 10, since B1 and A0 have been selected as the multi-motion parameters, the encoder must send a candidate list index (ie, each index indicating B1 and A0) to the decoder.

1) The encoder may transmit a candidate list index indicating the selected multiple parameters in the motion parameter candidate list to the decoder as it is.

For example, in the case of FIG. 10, when the method 1) is used, candidate list index values 1 and 3 may be transmitted to the decoder.

2) Or, in the case of the first candidate list index, the encoder may transmit the candidate list index value of the motion parameter candidate list as it is, and the second candidate list index may transmit a difference value from the first candidate list index to the decoder. Similarly, the candidate list index may then transmit a difference value with the previous candidate list index to the decoder.

2-1) In this case, when the order in which each motion parameter is transmitted is determined, the encoder may transmit each candidate list index in the order. In this case, the second and subsequent candidate list indexes may transmit a difference value with the previous candidate list index to the decoder.

2-2) Or, when each motion parameter is transmitted irrespective of the transmission order, the candidate list index indicating each motion parameter is sorted in ascending order so that a negative number does not occur in the difference value, and the imprinting candidate list according to the order The index can be sent to the decoder.

For example, in the case of FIG. 10, when the method 2) is used, candidate list index values may be 1, 2 (= index 3 -index 1) transmitted to the decoder.

Table 1 illustrates syntax for transmitting multiple motion parameters for a block to which merge mode is applied.

Table 1 exemplifies the syntax of the method 1) of the above-described method for transmitting the number of multiple motion parameters. For other methods, the syntax may be configured differently from that of Table 1 below.

Referring to Table 1, when a merge mode other than skip is applied when encoding a current processing block (for example, a prediction unit) (that is, cu_skip_flag [x0] [y0] == 0 and merge_flag [x0] [y0] == 1) and the number of multiple motion parameters (num_multiple_motion_param_munus_1) may be transmitted to the decoder.

The decoder checks the number of multiple motion parameters num_multiple_motion_param_munus_1 (that is, the number of candidate list indexes) when a merge mode is applied in which the current processing block (for example, the prediction unit) is not skip. .

For example, a value obtained by adding 1 to 'num_multiple_motion_param_munus_1' may indicate the number of multiple motion parameters.

The encoder transmits a candidate list index (multiple_merge_idx [x0] [y0]) for indicating multiple motion parameters by the number of multiple motion parameters.

The decoder checks the index (multiple_merge_idx [x0] [y0]) of the candidate list for indicating the multiple motion parameter while looping the number of multiple motion parameters.

Here, 'multiple_merge_idx [x0] [y0]' may indicate the index value of the candidate list as it is, or in case of the first candidate list index, 'multiple_merge_idx [x0] [y0]' indicates the candidate list index and The second and subsequent candidate list indexes may indicate a difference value from the previous candidate list index.

In another embodiment according to the present invention, a motion parameter candidate list is created by using neighboring motion parameters, and one of them is selected to include a candidate list index, an inter prediction mode (or a reference direction, a reference list direction), and a reference index of the current block. (Or reference picture index, reference list index), when a mode for transmitting a motion vector difference value of a motion parameter selected from a motion parameter candidate list (AMVP mode) is applied, a method for signaling multiple motion parameters is proposed. .

11 illustrates a case where B1 and A1 are selected as multiple motion parameters in a state where a motion parameter candidate list (that is, a motion vector predictor candidate list) is configured.

As in the merge mode, the decoder needs to know the number of motion parameters transmitted from the encoder in order to transmit the multiple motion parameters selected by the transmitter (ie, the encoder) to the receiver (ie, the decoder). To this end, the methods described above may be used in the same manner.

In the AMVP mode, the difference between the multiple motion parameters and the motion vector is transmitted together, so the following methods can be used.

1) The encoder may bundle four pieces of information of a candidate list index, an inter prediction mode (or reference direction), a reference index, and a motion vector difference value in one unit and transmit the number of multiple motion parameters.

For example, in the case of FIG. 11, when the method 1) is used, the candidate list index '1', the inter prediction mode (inter_pred_idc), the reference index (ref_idx), and the motion vector difference value (mvd) are transmitted to the decoder as a set. The candidate list index '0', the inter prediction mode inter_pred_idc, the reference index ref_idx, and the motion vector difference value mvd may be transmitted to the decoder as a set.

2) Alternatively, the encoder transmits only the first motion parameter, four types of information of the candidate list index, the reference list direction, the reference list index, and the difference vector, and after that, only three pieces of information except the candidate list index may be transmitted.

2-1) At this time, when transmitting the second and subsequent motion parameter information, the reference value of the difference vector may be fixed and used as the motion vector of the motion parameter indicated by the corresponding candidate list index.

2-2) Or, when transmitting the second and subsequent motion parameter information, the reference of the difference vector may be set to the motion vector of the immediately transmitted motion parameter.

2-3) Alternatively, the method of 2-1) and 2-2) may be optionally used. In this case, the encoder may transmit a flag indicating a method used among the methods of 2-1) and 2-2). Alternatively, the decoder may infer a method selected among the methods of 2-1) and 2-2) using a specific value (eg, an absolute value of a motion difference vector).

For example, in the case of FIG. 11, using the method 2), the candidate list index '1', the inter prediction mode (inter_pred_idc), the reference index (ref_idx), and the motion vector difference value (mvd) are transmitted to the decoder as a set. The inter prediction mode inter_pred_idc, the reference index ref_idx, and the motion vector difference value mvd may be transmitted to the decoder as a set.

Referring to FIG. 12, the decoder determines whether inter prediction using multiple motion parameters is applied to the current block (S1201).

Here, the information indicating whether the multiple motion parameter is used (for example, the flag 'multiple_motion_param_enable' indicating the on / off of the multiple motion parameter) is a sequence level, a picture. It may be transmitted in units of levels or slice levels.

The encoder may transmit on / off on whether to use multiple motion parameters at a sequence level (eg, Sequence Parameter Set (SPS)). In this case, the decoder may determine whether the multi motion parameter is used in the current video image on a video image basis.

The encoder turns on / off whether to use multiple motion parameters at a Picture level (e.g. Picture Parameter Set (PPS)) or at a slice level (e.g. slice header). You can send (on / off). In this case, the decoder may determine whether multiple motion parameters are used in the current picture / slice on a picture / slice basis.

Alternatively, the information indicating whether the multiple motion parameter is used (for example, the flag 'multiple_motion_param_flag' indicating whether the multiple motion parameter is applied) may be transmitted in units of processing blocks (eg, coding units or prediction units). It may be. In this case, the decoder may determine whether the multi motion parameter is applied to the current processing block on a processing block (for example, coding unit or prediction unit) basis.

For example, a merge mode and an AMVP mode may be applied as a method of encoding a processing block to which multiple motion parameters are applied.

In this case, when the merge mode is applied to the corresponding processing block, a flag (multiple_motion_param_flag) indicating whether to apply the multiple motion parameter after the merge flag (merge_flag) indicating whether the merge mode is applied in the prediction unit syntax is transmitted. Can be. In addition, when the AMVP mode is applied to the corresponding processing block, a flag (multiple_motion_param_flag) indicating whether to apply the multiple motion parameter may be transmitted before determining the slice type (slice_type).

If the flag (multiple_motion_param_flag) indicating whether to apply the multiple motion parameter to the processing block is applied (i.e., the flag value is '1'), the partition for the prediction unit (i.e., the processing block is the prediction unit) The mode (PartMode) may be set to 2N × 2N.

In addition, whether the multiple motion parameters are applied to the current processing block may be indicated as one of the partition modes (PartMode) other than the flag (multiple_motion_param_flag) indicating whether to apply the multiple motion parameters. Even in this case, the prediction unit (that is, when the processing block is the prediction unit) may be decoded without further splitting in one coding unit, such as a split mode (PartMode) 2N × 2N.

As a result of the determination in step S1201, when the multi-motion parameter is applied to the current block, the decoder decodes (or derives) the multi-motion parameter (S1202).

At this time, the candidate list index selected from the motion parameter candidate list is transmitted, and the decoder can decode the multiple motion parameters by decoding the candidate list index.

For example, if the merge mode is applied to the current processing block, the decoder decodes the candidate list index and decodes (or derives) the motion parameter for the current processing block from the motion parameters of the plurality of candidate blocks indicated by the candidate list index, respectively. )can do.

Alternatively, when the AMVP mode is applied to the current processing block, the decoder may decode the candidate list index (if present), the inter prediction mode, the reference index, and the motion vector difference value received from the encoder. The motion vector prediction value of the current processing block is derived from the motion parameters of the plurality of candidate blocks indicated by the candidate list index, and the motion vector of the current processing block is obtained by adding the derived motion vector prediction value and the received motion vector difference value. Can be decrypted (or derived).

In this case, as described above, the decoder may receive the number of multiple motion parameters from the encoder (eg, 'num_multiple_motion_param_minus_1') or the number of multiple motion parameters may be predetermined so that the decoder may already know. In this case, the decoder may decode a candidate list index (and inter prediction mode, reference index, and motion vector difference value) transmitted from the encoder while performing a loop as many times as the number of multiple motion parameters.

Or, the encoder transmits a candidate list index (and inter prediction mode, reference index, and motion vector difference value) to the decoder, and ends when transmission of the candidate list index (and inter prediction mode, reference index, and motion vector difference value) is finished. The code may be sent to the decoder. Alternatively, the encoder may complete the transmission without transmitting the end code to the decoder when the maximum number of candidate list indexes to be transmitted reaches a predetermined maximum number. In this case, the decoder decodes the candidate list index (and inter prediction mode, reference index, motion vector difference value) transmitted from the encoder, and reaches the maximum number of candidate list indexes or if the end code is decoded, the candidate list index ( And the decoding process of the inter prediction mode, the reference index, and the motion vector difference value.

In this case, as described above, the candidate list index value in the motion parameter candidate list may be transmitted as it is.

Alternatively, in the case of the first candidate list index, the candidate list index value of the motion parameter candidate list may be transmitted as it is, and the second and subsequent candidate list indexes may be transmitted as difference values from the first candidate list index.

The decoder performs motion compensation on the current block by using the decoded multiple motion parameters (S1203).

That is, the decoder identifies multiple reference blocks (within the reference picture) for the current block by using the decoded multiple motion parameters, and generates a predictive block (or prediction value) for the current block based on the multiple reference blocks. do.

In this case, as described below, the partitioning information (for example, 'block_partitioning_info') of the current processing block may be transmitted from the encoder to apply the multi-motion parameter, but when the partitioning of the current processing block is derived from the decoder, May not be encoded and transmitted.

For example, the partitioning information may include the location of each subblock in which the current processing block is divided. Alternatively, when the split type is predefined, the split information may include indication information (eg, an index or a flag) indicating the split type selected from the predefined split types.

A method of performing motion compensation on the current processing block using the multiple motion parameters will be described in detail later.

On the other hand, when it is determined in step S1201 that the multi-motion parameter is not applied to the current processing block, the decoder decodes the motion parameter (S1204).

For example, when merge mode is applied to the current processing block, the decoder may decode the candidate list index and decode (or derive) the motion parameter for the current processing block from the motion parameter of the candidate block indicated by the candidate list index. have.

Alternatively, when the AMVP mode is applied to the current processing block, the decoder may decode the candidate list index (if present), the inter prediction mode, the reference index, and the motion vector difference value received from the encoder. The motion vector prediction value of the current processing block is derived from the motion parameter of the candidate block indicated by the candidate list index, and the motion vector prediction value and the received motion vector difference value are summed to decode (or derive) the motion vector of the current processing block. )can do.

The decoder performs motion compensation on the current processing block by using the decoded motion parameter (S1205).

Motion Compensation Method Using Multiple Motion Parameters

Embodiment 1) According to an embodiment of the present invention, when performing motion compensation using multiple motion parameters, a motion compensation method overlapping the entire block using each motion parameter is proposed.

FIG. 13 shows an example of a method of overlapping an entire block in motion compensation using multiple motion parameters.

In FIG. 13, there are three motion parameters transmitted from the encoder and each information is {unidirectional prediction, LIST0, first picture, (-a, b)}, {unidirectional prediction, LIST1, first picture, (c, d)}, {unidirectional Prediction, LIST1, second picture, (e, -f)}. Assume that the current block is CB, and the reference block obtained using the respective motion parameters is A, B, or C.

The prediction value for the current block can be obtained using the following methods.

1) A method of obtaining prediction values by equally overlapping values of each reference block

Pixel values (or sample values) of each reference block specified by each motion parameter included in the multiple motion parameters may be superimposed at the same rate to generate a prediction value (or prediction block) for the current processing block.

According to this method, when a pixel value corresponding to the (i, j) th position of the block is called a block (i, j), a prediction value for the current block may be generated using Equation 1 below.

Referring to Equation 1, to obtain CB (i, j) representing a prediction value of the current block, the average of pixel values at the same positions of each reference block A, B, and C is taken. This method applies equally to each pixel of the current block.

2) How to obtain a predicted value by overlapping each reference block by reflecting a certain ratio (that is, applying weight)

A pixel value (or sample value) to which a predetermined weight is applied may be overlapped for each reference block specified by each motion parameter included in the multi-motion parameter to generate a prediction value (or prediction block) for the current processing block.

According to this method, when a pixel value corresponding to the (i, j) th position of the block is called a block (i, j), a prediction value for the current block may be generated using Equation 2 below.

Referring to Equation 2, the reference block determined by each motion parameter of the multiple motion parameter has a certain ratio (a, b, c in Equation 2), and reflects each ratio to predict the value CB (i) for the current block. , j)

In this case, ratios (ie, coefficients) a, b, and c for each overlap may be transmitted to the decoder as a motion parameter.

For example, in the encoder, a coefficient for each superposition may be obtained through a search based on rate-distortion optimization (RDO) by setting a start point and a search section of each coefficient. Each coefficient obtained as described above may be transmitted to the decoder as a motion parameter.

Alternatively, the coefficients a, b, and c for each overlap may be derived and used in the same manner as the encoder in the decoder. The following methods can be applied to calculate the coefficients a, b, c for overlap.

When the encoder and the decoder derive the same method without transmitting coefficients, the encoder / decoder may acquire the reference block due to the characteristic of the corresponding picture or the positional characteristic of the reference block.

For example, each coefficient may be determined based on a difference between a picture order count (POC) of a picture in which each reference block is located and a POC of a current picture. As an example, a coefficient may be determined by assigning a high ratio to a picture close to the current picture (ie, a picture having a small POC difference).

As another example, coefficients for each overlap may be determined based on the magnitude of the absolute value of the motion vector pointing to each reference block. In one example, the weighting coefficient may be set in inverse proportion to the absolute value of the motion vector.

In addition, when the encoder and the decoder derive the same method without transmitting the coefficients, each coefficient may be determined in consideration of the similarity between the current block and each reference block.

In one example, a large weight may be assigned to a reference block having a high similarity with the current block. A method of calculating the similarity between the current block and the reference block will be described with reference to the drawings below.

In the decoder, a template 1401 illustrated in FIG. 14 may be used to calculate the similarity between the current block and the reference block. For example, the template 1401 may be composed of pixels adjacent to the left and / or top of the current block and the reference block.

The decoder may infer the similarity or correlation between the current block and the reference block by calculating a sum of absolute differences (SAD) or mean absolute difference (MAD) in the template region of the current block and the reference block. And, as in the previous example, a large weight may be assigned to a reference block having a high similarity with the current block.

3) A method of obtaining a prediction value by overlapping with different ratios according to positions of a reference block and pixels in the block

A predetermined weighted value is superimposed on each pixel value (or sample value) of each reference block specified by each motion parameter included in the multi-motion parameter to generate a prediction value (or prediction block) for the current processing block. have.

According to this method, when a pixel value corresponding to the (i, j) th position of a block is called a block (i, j), a prediction value for the current block may be generated for each pixel by using Equation 3 below. have.

Referring to Equation 3, the overlap ratio value applied to each reference block is not fixed and has a value that varies depending on the position (i, j) of the pixel.

In Equation 3, the condition a (i, j) + b (i, j) + c (i, j) is an overlap ratio value applied to each pixel position to maintain a constant energy of the predicted value CB for the current block. Sum indicates that 1 must be maintained.

Each overlap ratio (or coefficient) (a (i, j), b (i, j), c (i, j)) may be determined in consideration of the direction in which the motion parameter is applied, correlation with the surrounding vector.

In this case, the ratio for each overlap may be transmitted to the decoder as a motion parameter.

For example, an optimal coefficient value can be determined through a search based on rate-distortion optimization (RDO). In this process, the superposition coefficients may be represented in the form of a specific function and transmitted to the decoder, rather than directly representing the superposed coefficients in units of pixels in consideration of the complexity of the search and the efficiency of coefficient coding.

For example, in the case of expressing the pixel unit coefficient in the form of a plane equation or Gaussian function, the complexity and the efficiency may be lower than that of directly calculating and encoding the weight value of each pixel position. As such, an example of a plane equation and a Gaussian function is shown in Equation 4 below.

In Equation 4, a weight coefficient in units of pixels may be expressed as a, b, c, or a, b, σ.

Alternatively, the coefficients for each overlap may be derived and used in the decoder using the same method as the encoder in the decoder.

For example, the encoder / decoder may calculate pixel-weighted weights (ie, ratios for overlapping) that are biased at similar positions in consideration of similarity between each motion information and neighboring motion information of the current block. This will be described with reference to the drawings below.

Referring to FIG. 15, if the motion information of the current block has a high similarity to the motion information of neighboring neighboring blocks in the upper left corner, the weight coefficient may be expressed by a Gaussian function biased in the upper left corner.

If the similarity is inferior to all spatially neighboring motion information, the entire block may be set to have a uniform weight.

The width of the Gaussian function may be set according to the similarity with the motion information of the neighboring block. The similarity may be calculated by the difference of each component of the motion vector when referring to the same picture, and may be calculated by the difference of each component of the vector by scaling to the picture referenced by the current block when not referring to the same picture. have.

If the width of the Gaussian function is fixed, the position of the center point of the Gaussian function may be adjusted by using the similarity between the surrounding motion information and the current motion information.

Embodiment 2) As another embodiment according to the present invention, when performing motion compensation using multiple motion parameters, motion compensation is performed by applying a motion parameter corresponding to each region (that is, a subblock) by dividing a current block. Suggest how to do it.

That is, the processing block may be divided into a plurality of subblocks, and a prediction block may be generated for each subblock using a motion parameter corresponding to each subblock among multiple motion parameters. The prediction block for the processing block may be generated by adding the prediction blocks for each subblock.

Assume that there are four multiple motion parameters transmitted from the encoder (or derived by the decoder) as shown in FIG. 16 (b).

In this case, the current block is divided into four blocks (hereinafter referred to as 'subblocks') as shown in FIG. 16 (a), and each subblock is allocated in the order in which the motion parameters are transmitted (or decoded) to compensate for the motion. This can be done. For example, if the motion vector for each subblock is Mv1, Mv2, Mv3, Mv4, the motion vector for each divided subblock may be allocated according to a Z-scan order. That is, each motion parameter included in the multiple motion parameters may be applied to each subblock according to the z-scan order in the order of decoding. In addition, motion compensation may be performed for each subblock using an assigned motion parameter.

Further embodiments of the present proposal are as follows.

1) When the number of motion parameters transmitted (or decoded) with respect to the current processing block is four, the division of the processing block may be divided into not only square but also various forms (ie, non-square).

If the current processing block is divided into squares, it is the same as the case of being divided into N × N blocks, and thus it may not be necessary to transmit additional information from the encoder.

On the other hand, when the current processing block is divided into non-squares, it will be described with reference to the drawings below.

As illustrated in FIG. 17, the current block may be divided into four subblocks (eg, rectangular shapes) having different sizes / shapes. In addition, motion compensation may be performed by using a motion parameter assigned to each subblock.

As such, when the current processing block is divided into non-square shapes, the encoder may further transmit information about the division of the current processing block to the decoder.

For example, the current processing block transmits information (flag) indicating that non-square division is applied and the position of each divided subblock (for example, the x-axis position and y-axis position of the upper left pixel of each subblock). Can be. As another example, a non-square segmentation form is predefined, and the encoder may transmit indication information (or a flag) indicating a segmentation form selected among the predefined segmentation forms to the decoder.

Alternatively, when the current processing block is divided into a non-square form, the splitting information of the processing block may not be transmitted from the encoder to the decoder, but may be derived and applied in the same manner in the encoder and the decoder. For example, the method of dividing the current processing block may be derived in the same manner in the encoder and the decoder by using the pixel value of the neighboring block, the motion vector of the neighboring block, and / or the prediction direction of the neighboring block.

This will be described with reference to the drawings below.

Referring to FIG. 18, division may be performed at

discrete portions

1802 and 1803 using peripheral pixel values 1801 of the current block.

If the peripheral pixels 1801 are entirely continuous, the center of the current block (ie, the center on the x-axis and / or y-axis) may be selected as a split point.

In addition, when the discontinuous portion appears more than once in the peripheral pixel 1801, a position where a high intensity of discontinuity (for example, a difference between successive pixel values or a value of a sobel operator) may be selected as a split point. .

Equation 5 expresses a process of selecting a position where the difference between successive pixel values is greatest as a split position by using an equation. As described above, a sobel operator or the like may be applied as well as the difference in successive pixel values.

In Equation 5, anabove neighboring pixel value (anpv) represents an upper neighboring pixel value of the current block, and lnpv (left neighboring pixel value) represents an left neighboring pixel value of the current block. That is, a boundary at which the difference between the values of consecutive pixels among the upper peripheral pixels of the current block and the left peripheral pixels of the current block is minimal may be selected as the splitting point.

In addition, when there are four multiple motion parameters, various types of division may be performed as shown in FIG. 19 below.

As illustrated in FIG. 19, the current block may be divided into four subblocks (eg, rectangular shapes) having different sizes / shapes. In addition, motion compensation may be performed by using a motion parameter assigned to each subblock.

As described above, when the current processing block is divided into a non-square form, the encoder may further transmit information about the division of the current processing block to the decoder. For example, the current processing block transmits information (flag) indicating that non-square division is applied and the position of each divided subblock (for example, the x-axis position and y-axis position of the upper left pixel of each subblock). Can be. As another example, a non-square segmentation form is predefined, and the encoder may transmit indication information (eg, an index or a flag) indicating a selected segmentation form among the predefined segmentation forms to the decoder.

2) If the number of motion parameters transmitted (or decoded) for the current processing block is less than four, motion compensation may be performed by dividing into various forms.

If there are three or less multiple motion parameters, symmetrical and asymmetrical partitioning are possible, similarly to four. This will be described with reference to the drawings below.

20 illustrates a symmetric chuck division form of the current block when motion compensation is performed by applying less than four multiple motion parameters according to an embodiment of the present invention.

20 (a) to 20 (d) illustrate a splitting method when the number of multiple motion parameters is three, and FIGS. 20 (e) and 20 (f) show when the number of multiple motion parameters is two. The division method is illustrated.

As such, when the current processing block is symmetrically divided, the encoder may further transmit information about the division of the current processing block to the decoder.

For example, the position of each subblock divided from the current processing block (eg, the x-axis position and the y-axis position of the upper left pixel of each subblock) may be transmitted. As another example, the partition type is predefined, and the encoder may transmit, to the decoder, indication information (eg, an index or a flag) indicating the selected partition type among the predefined partition types.

Alternatively, the split information of the current processing block may not be transmitted from the encoder to the decoder, but may be derived and applied in the same manner in the encoder and the decoder. For example, the method of dividing the current processing block may be derived in the same manner in the encoder and the decoder by using the pixel value of the neighboring block, the motion vector of the neighboring block, and / or the prediction direction of the neighboring block. This will be described with reference to the drawings below.

As shown in FIG. 21, the pixel (or block) adjacent to the upper left end of the current block is referred to as LT, the pixel (or block) adjacent to the upper right end is referred to as RT, and the pixel (or block) adjacent to the lower left end is referred to as LB.

An example of a method of deriving a partition form of a current block by using neighboring pixel values, and compares a value of a pixel LT adjacent to an upper left end, a pixel RT adjacent to an upper right end, and a pixel LB adjacent to a lower left end. The partition type of the current block can be determined.

Equations 6 to 9 below are equations for determining the partition type of the current block using neighboring pixel values in the encoder / decoder when three multi-motion parameters are used. In Equations 6 to 9, P () represents a pixel value of the corresponding position.

When all of Equations 6 are satisfied, the current block may be divided into N × 2N (R) forms as shown in FIG. 20 (c).

When all of Equations 7 are satisfied, the current block may be divided into N × 2N (L) forms as shown in FIG. 20 (a).

When all of Equation 8 is satisfied, the current block may be divided into 2N × N (D) forms as shown in FIG. 20 (b).

When all of Equations 9 are satisfied, the current block may be divided into 2N × N (U) forms as shown in FIG. 20 (d).

Equations 10 and 11 below are equations for determining the partition type of the current block using neighboring pixel values in the encoder / decoder when two multi-motion parameters are used. In Equations 10 and 11, P () represents a pixel value at the corresponding position.

If Equation 10 is satisfied, the current block may be divided into N × 2N forms as shown in FIG. 20 (e).

When Equation 11 is satisfied, the current block may be divided into 2N × N shapes as shown in FIG. 20 (f).

The method of using the neighbor motion information may also use, for example, the similarity between the motion information of the block LT adjacent to the upper left end of the current block, the block RT adjacent to the upper right end, and the block LLB adjacent to the lower left end. The partition form of can be determined.

Equations 12 to 15 below are calculations for determining the partition type of the current block by using the peripheral motion information in the encoder / decoder when three multiple motion parameters are used. In Equations 12 to 15, mv () represents a motion vector at the corresponding position, and || represents a sum of the differences between the motion vector components (that is, the x-axis component and the y-axis component).

When all of Equation 12 is satisfied, the current block may be divided into N × 2N (R) forms as shown in FIG. 20 (c).

When all of Equation 13 is satisfied, the current block may be divided into N × 2N (L) forms as shown in FIG. 20 (a).

When all of Equation 14 is satisfied, the current block may be divided into 2N × N (D) form as shown in FIG. 20 (b).

When all of Equation 15 is satisfied, the current block may be divided into a 2N × N (U) form as shown in FIG. 20 (d).

Equations 16 and 17 below are equations for determining the partition type of the current block by using the peripheral motion information in the encoder / decoder when two multiple motion parameters are used. In equations (16) and (17), mv () represents a motion vector at the corresponding position, and || represents a sum of the differences between the motion vector components (ie, the x-axis component and the y-axis component).

If Equation 16 is satisfied, the current block may be divided into N × 2N forms as shown in FIG. 20 (e).

If Equation 17 is satisfied, the current block may be divided into 2N × N forms as shown in FIG. 20 (f).

On the other hand, when motion information of the block LT adjacent to the upper left end of the current block, the block RT adjacent to the upper right end, and the block LLB adjacent to the lower left end are unavailable, the split may be considered to occur at the side associated with the corresponding position. have. For example, if it is possible to refer to the motion information of the LT and RT, but cannot refer to the motion information of the LB, it can be considered to be divided into 2N × N assuming that there is a discontinuity between the upper block and the lower block. . Alternatively, when motion information of LT and LB can be referred to, but motion information of RT cannot be referred to, it can be regarded that it is divided into N × 2N forms on the assumption that there is a discontinuity between the left block and the right block.

In addition, when the POCs are different from each other in reference to a block LT adjacent to the upper left end of the current block, a block adjacent to the upper right end RT, and a block adjacent to the lower left end LB, the encoder / decoder may determine the current picture and each reference picture. After the POC scaling of the motion vector of each neighboring block in consideration of the inter-distance (ie, POC difference), the difference between each motion vector component may be compared.

If the current block is split asymmetrically, information about the split pattern and split position should be transmitted from the encoder to the decoder. If the encoder and the decoder derive the partition type of the current block in the same manner, the information on the partition pattern is preferably transmitted to the decoder.

Embodiment 3) According to another embodiment of the present invention, when motion compensation is applied to multiple motion parameters, motion is applied by applying motion parameters regardless of the order of transmission (or derivation) to each area divided from the current block. Suggest ways to perform rewards.

Assume that there are four multiple motion parameters transmitted from the encoder (or derived by the decoder) as shown in FIG. 22 (b).

When the motion parameters are transmitted (or derived) regardless of the order, the divided regions (ie, subblocks) and the motion parameters may correspond to the motion parameters of the neighboring blocks based on the degree of correlation. That is, a motion parameter applied to each subblock may be determined based on a correlation between each motion parameter included in the multi-motion parameter and the motion parameter of the neighboring block of each subblock.

When the current block is divided into four subblocks as shown in FIG. 22, in the case of the first block (upper left subblock), the motion parameters of B2 or the neighboring block (s) and the multiple transmitted from the encoder (or derived) In comparison with the motion parameters, the decoder selects a motion parameter having the most similar value.

Similarly, in the case of the second subblock (the upper right subblock), the decoder has the most similar value compared to the motion parameters of B1 or its surrounding block (s) and the multiple motion parameters transmitted (or derived) from the encoder. Select a motion parameter.

In addition, for the third subblock (lower left subblock), the decoder compares the motion parameter of A1 or its surrounding block (s) with the multiple motion parameters transmitted from (or derived from) the encoder. The branch selects a motion parameter.

Also, in the case of the fourth subblock (lower subblock), the decoder compares the motion parameters of T0 or its surrounding block (s) with the multiple motion parameters transmitted from (or derived from) the encoder. The branch selects a motion parameter.

Here, the correlation between the motion parameters may be calculated in the form of a combination of the difference between the prediction direction, the reference list, the reference index, and / or the motion vector.

In this case, a weight may be given to a specific motion parameter. For example, as shown in FIG. 22B, when a weight is given to the first motion parameter 1 as one of four motion parameters, the first motion parameter 1 is preferentially assigned to each subblock. Corresponds to a subblock adjacent to the neighboring block with the highest similarity (or correlation) as compared to the motion parameters of the neighboring blocks B1, B2, A1, T0 of (e.g., the lower left subblock if it is most similar to A1). You can. The remaining second to fourth motion parameters may be compared with the motion parameters of the neighboring blocks of each subblock.

In addition, a threshold may be preset to a specific motion parameter. For example, when a threshold is set for a specific motion parameter among four motion parameters as shown in FIG. 22B, the specific motion parameter is compared with the motion parameters of the neighboring blocks B1, B2, A1, and T0 of each subblock. Only when the value is smaller than the preset threshold, it may correspond to a subblock adjacent to the neighboring block.

As such, when the transmitted motion parameters correspond to the respective partitions (that is, subblocks) in any order, based on the positions of candidate blocks (in the motion parameter candidate list) corresponding to each motion parameter included in the multi-motion parameters. The motion parameter applied to each subblock may be determined.

For example, in the merge mode in the current block, the position information of the motion parameter transmitted through the merge index can be known and correspond to the divided region based on this information. This will be described with reference to the drawings below.

In FIG. 23, four multi-motion parameters for the current block are used to divide the current block into four sub-blocks, and merge

indices

0, 1, 2, and 3 for the multi-motion parameters are assigned to the decoder as shown in FIG. Assume a signaled case.

The decoder may check the information of the neighboring block indicated by each merge index and correspond to the partition that is closest to the corresponding block.

For example, in the case of merge index 0 (Mrg0), since the neighbor block covered by the merge index is A1, the motion parameter of A1 may correspond to the lower left subblock closest to A1.

In addition, in the merge index 1 (Mrg1), since the neighboring block covered by the merge index is B1, the motion parameter of B1 may correspond to the upper right subblock closest to B1.

In addition, in the merge index 2 (Mrg2), since the neighboring block covered by the merge index is B2, the motion parameter of B2 may correspond to the upper left subblock closest to B2.

In addition, in the merge index 3 (Mrg3), since the neighbor block covered by the merge index is T0, a motion parameter of T0 of T0 may correspond to the lower right subblock closest to T0.

Referring to FIG. 24, the inter prediction unit 181 (see FIG. 1, 261; FIG. 2) implements the functions, processes, and / or methods proposed in FIGS. 3 to 23. In detail, the

inter predictors

181 and 261 may include a multiple motion parameter application determiner 2401, a motion parameter decoder 2402, and a predictive block generator 2403.

The multi-motion parameter application determining unit 2401 determines whether inter prediction using the multi-motion parameter is applied to the current block (eg, a coding unit or a prediction unit constituting an image).

As described above, the multi-motion parameter application determining unit 2401 may determine whether inter prediction using the multi-motion parameter is applied to the current block by using information indicating whether the multi-motion parameter is used. In this case, the information indicating whether the multiple motion parameter is used may be transmitted in units of a sequence level, a picture level, a slice level, or a processing block (eg, a coding unit or a prediction unit) level. Can be.

The motion parameter decoder 2402 decodes the multi motion parameter when the multi motion parameter is used. In addition, the motion parameter may be decoded when the multi motion parameter is not used.

When the merge mode is applied to the current block, the motion parameter decoder 2402 may decode a candidate list index selected from the motion parameter candidate list. Then, the motion parameters for the current block can be decoded (or derived) from the motion parameters of the plurality of candidate blocks indicated by the candidate list index.

Alternatively, when the AMVP mode is applied to the current block, the motion parameter decoder 2402 may decode the candidate list index (if present), the inter prediction mode, the reference index, and the motion vector difference value. Then, the motion vector prediction values of the current processing blocks can be derived from the motion parameters of the plurality of candidate blocks indicated by the candidate list index. The motion vectors of the current processing block may be decoded (or derived) by adding the derived motion vector prediction values and the received motion vector difference values.

The prediction block generator 2403 generates a prediction block (or prediction value) for the current block by using the multiple motion parameters. In addition, when multiple motion parameters are not used, a prediction block for the current block may be generated using the motion parameters.

The prediction block generator 2403 may generate a prediction block for the current block by using the method of FIG. 13 to FIG. 23.

The embodiments described above are the components and features of the present invention are combined in a predetermined form. Each component or feature is to be considered optional unless stated otherwise. Each component or feature may be embodied in a form that is not combined with other components or features. It is also possible to combine some of the components and / or features to form an embodiment of the invention. The order of the operations described in the embodiments of the present invention may be changed. Some components or features of one embodiment may be included in another embodiment or may be replaced with corresponding components or features of another embodiment. It is obvious that the claims may be combined to form an embodiment by combining claims that do not have an explicit citation relationship in the claims or as new claims by post-application correction.

Embodiments according to the present invention may be implemented by various means, for example, hardware, firmware, software, or a combination thereof. In the case of a hardware implementation, an embodiment of the present invention may include one or more application specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs), FPGAs ( field programmable gate arrays), processors, controllers, microcontrollers, microprocessors, and the like.

In the case of implementation by firmware or software, an embodiment of the present invention may be implemented in the form of a module, procedure, function, etc. that performs the functions or operations described above. The software code may be stored in memory and driven by the processor. The memory may be located inside or outside the processor, and may exchange data with the processor by various known means.

It will be apparent to those skilled in the art that the present invention may be embodied in other specific forms without departing from the essential features of the present invention. Accordingly, the above detailed description should not be construed as limiting in all aspects and should be considered as illustrative. The scope of the invention should be determined by reasonable interpretation of the appended claims, and all changes within the equivalent scope of the invention are included in the scope of the invention.

As mentioned above, preferred embodiments of the present invention are disclosed for purposes of illustration, and those skilled in the art can improve and change various other embodiments within the spirit and technical scope of the present invention disclosed in the appended claims below. , Replacement or addition would be possible.

Claims

In the method for processing an image based on inter prediction,

Determining whether an inter prediction using multiple motion parameters is applied to a block constituting an image;

Decoding the multiple motion parameter when the multiple motion parameter is used; And

Generating a predictive block for the block using the multiple motion parameters,

And wherein the multiple motion parameters are defined by a plurality of motion parameters selected from a single motion parameter candidate list.
The method of claim 1,

And the prediction block is generated by overlapping pixel values of each reference block specified by each motion parameter included in the multi-motion parameter at the same ratio.
The method of claim 1,

And the prediction block is generated by overlapping pixel values to which a predetermined weight is applied for each reference block specified by each motion parameter included in the multi-motion parameter.
The method of claim 1,

And the prediction block is generated by overlapping a value to which a predetermined weight is applied for each pixel value of each reference block specified by each motion parameter included in the multi-motion parameter.
The method of claim 1,

And a block is divided into a plurality of subblocks, and a prediction block is generated for each subblock by using a motion parameter applied to each subblock among the multiple motion parameters.
The method of claim 5,

The inter prediction mode based image processing method is applied to each subblock in the order in which each motion parameter included in the multi-motion parameter is decoded according to a z-scan order.
The method of claim 5,

And a motion parameter applied to each subblock based on a correlation between each motion parameter included in the multi-motion parameter and a motion parameter of a neighboring block of each subblock.
The method of claim 5,

And a motion parameter applied to each subblock based on a position of a candidate block corresponding to each motion parameter included in the multi-motion parameter.
The method of claim 1,

And a candidate list index selected from the motion parameter candidate list is transmitted, and the multiple motion parameters are decoded using the candidate list index.
The method of claim 9,

And the number of the candidate list indexes is transmitted, and then the candidate list indexes are sequentially transmitted.
The method of claim 9,

The decoding method of the candidate list index is terminated when the end code for the candidate list index is transmitted.
The method of claim 9,

And a candidate list index value is transmitted for the first motion parameter included in the multi-motion parameter, and a difference value with the previous candidate list index is transmitted for the second and subsequent motion parameters.
The method of claim 1,

A candidate list index selected from the motion parameter candidate list, an inter prediction mode indicating an inter prediction direction, a reference index indicating a reference picture, and motion vector information are transmitted in one unit,

And the multi-motion parameter is decoded using the candidate list index, the inter prediction mode, the reference index, and the motion vector information.
The method of claim 1,

The candidate list index, the inter prediction mode, the reference index, and the motion vector information are transmitted in the case of the first motion parameter included in the multi-motion parameter, and in the case of the second motion parameter, the inter prediction mode and the reference index are transmitted. And an inter prediction mode based image transmission method in which the motion vector information is transmitted.
An apparatus for processing an image based on inter prediction,

A multi-motion parameter application determining unit configured to determine whether inter prediction using the multi-motion parameter is applied to the block constituting the image;

A motion parameter decoder for decoding the multiple motion parameters when the multiple motion parameters are used; And

A prediction block generation unit generating a prediction block for the block by using the multi-motion parameter,

Wherein the multiple motion parameters are defined by a plurality of motion parameters selected from a single motion parameter candidate list.