WO2020042604A1

WO2020042604A1 - Video encoder, video decoder and corresponding method

Info

Publication number: WO2020042604A1
Application number: PCT/CN2019/079955
Authority: WO
Inventors: 陈焕浜; 杨海涛; 陈建乐
Original assignee: 华为技术有限公司
Priority date: 2018-08-27
Filing date: 2019-03-27
Publication date: 2020-03-05
Also published as: CN110868602A; CN110868602B

Abstract

The embodiment of the present invention provides a video encoder, a video decoder and a corresponding method. The method comprises: parsing code streams to obtain an index, the index is used for indicating a target candidate motion vector set of a current decoding block; determining, according to the index, the target candidate motion vector set from a candidate motion vector list; if the first neighboring affine decoding block is a four-parameter affine decoding block and is located in the CTU above the current decoding block, the candidate motion vector list includes a first group of candidate motion vector prediction values obtained on the basis of a bottom left control point and a bottom right control point of the first neighboring affine decoding block; and obtaining a pixel prediction value of the current decoding block on the basis of the target candidate motion vector set. According to the embodiment of the present invention, memory reading can be reduced so as to promote the encoding and decoding performance.

Description

Video encoder, video decoder and corresponding method

Technical field

The present application relates to the technical field of video encoding and decoding, and in particular, to an inter prediction method and device for a video image, and a corresponding encoder and decoder.

Background technique

Digital video capabilities can be incorporated into a wide variety of devices, including digital television, digital live broadcast systems, wireless broadcast systems, personal digital assistants (PDAs), laptop or desktop computers, tablet computers, e-book readers, Digital cameras, digital recording devices, digital media players, video game devices, video game consoles, cellular or satellite radio phones (so-called "smart phones"), video teleconferencing devices, video streaming devices, and the like . Digital video devices implement video compression technology, for example, in standards defined by MPEG-2, MPEG-4, ITU-T H.263, ITU-T H.264 / MPEG-4 Part 10 Advanced Video Coding (AVC), Video coding standards described in the H.265 / High Efficiency Video Coding (HEVC) standard and extensions to such standards. Video devices can implement such video compression techniques to more efficiently transmit, receive, encode, decode, and / or store digital video information.

Video compression techniques perform spatial (intra-image) prediction and / or temporal (inter-image) prediction to reduce or remove redundancy inherent in video sequences. For block-based video coding, a video slice (ie, a video frame or a portion of a video frame) can be partitioned into image blocks, which may also be referred to as tree blocks, coding units (CU), and / or coding nodes . The spatial prediction of reference samples in neighboring blocks in the same image is used to encode the image blocks in the to-be-encoded (I) slice of the image. The image blocks in an inter-coded (P or B) slice of an image may use spatial prediction relative to reference samples in neighboring blocks in the same image or temporal prediction relative to reference samples in other reference images. An image may be referred to as a frame, and a reference image may be referred to as a reference frame.

Among them, various video coding standards including the High-Efficiency Video Coding (HEVC) standard have proposed predictive coding modes for image blocks, that is, predicting a current block to be coded based on a video data block that has been coded. In intra prediction mode, the current block is predicted based on one or more previously decoded neighboring blocks in the same image as the current block; in inter prediction mode, the current block is predicted based on already decoded blocks in different images. Piece.

Motion vector prediction is a key technique that affects encoding / decoding performance. In the current motion vector prediction process, there are motion vector prediction methods based on translational motion models for flat animals in the picture; motion vector prediction methods based on motion models and motion vectors based on control point combinations for non-translational objects. method of prediction. Among them, the motion vector prediction method based on the motion model reads more memory, which results in a slower encoding / decoding speed. How to reduce the amount of memory read in the motion vector prediction process is a technical issue being studied by those skilled in the art.

Summary of the Invention

The embodiments of the present application provide an inter-frame prediction method and device for a video image, and a corresponding encoder and encoder, which can reduce the read amount of the memory to a certain extent, thereby improving encoding and encoding performance.

In a first aspect, an embodiment of the present application discloses an encoding method including: determining a target candidate motion vector group from a candidate motion vector list (for example, an affine transformation candidate motion vector list) according to a rate distortion cost criterion; The target candidate motion vector group represents a motion vector prediction value of a set of control points of a current coding block (which may be specifically a current affine coding block), wherein if the first neighboring affine coding block is a four-parameter affine coding block, And the first adjacent affine coding block is located at the coding tree unit CTU above the current coding block, the candidate motion vector list includes a first set of candidate motion vector prediction values, and the first set of candidate motion vector predictions The value is obtained based on the lower left control point and the lower right control point of the first neighboring affine coding block; optionally, the candidate motion vector list may be constructed in the following manner: according to the neighboring block A and the neighboring block B , The neighboring block C, the neighboring block D, and the neighboring block E (as shown in FIG. 7A) determine one or more neighboring affine coding blocks of the current coding block, the one or more neighboring affine coding blocks Including the first adjacent affine coding block; then, if the first adjacent affine coding block is a four-parameter affine coding block, the lower left control point and the lower right control point of the first adjacent affine coding block are used. The first affine model obtains a motion vector prediction value of a first set of control points of the current encoding block, where the motion vector prediction value of the first set of control points of the current encoding block is used as a first of the candidate motion vector list. Group candidate motion vectors; after the target candidate motion vector group is determined in the above manner, an index corresponding to the target candidate motion vector is coded into a code stream to be transmitted (optionally, when the length of the candidate motion vector list is 1, (No index is needed to indicate the target motion vector group).

In the above method, there may be only one candidate motion vector group in the candidate motion vector list, or there may be multiple candidate motion vector groups, where each candidate motion vector group may be a motion vector binary group or a motion vector triplet . When there are multiple candidate motion vector groups, the predicted value of the first candidate motion vector group is one candidate motion vector group of the multiple candidate motion vector groups, and the other candidate motion vector groups of the multiple candidate motion vector groups are The generation principle may be the same as the generation principle of the first group of candidate motion vector prediction values, or may be different from the generation principle of the first group of candidate motion vector prediction values. Further, the target candidate motion vector group is an optimal candidate motion vector group selected from a candidate motion vector list according to a rate distortion cost criterion. If the first group of candidate motion vector prediction values is optimal, then, The selected target candidate motion vector group is the first group of candidate motion vector prediction values; if the first group of candidate motion vector prediction values is not optimal, then the selected target candidate motion vector group is not the first group of candidate motions. Vector prediction. The first adjacent affine coding block is a four-parameter affine coding block among the neighboring blocks of the current coding block. The specific one is not limited here. Taking FIG. 7A as an example, it may be a neighboring block therein. A, or neighboring block B, or other neighboring blocks. In addition, "first", "second", "third", etc. appearing elsewhere in the embodiments of the present application all mean a certain meaning. Among them, "first" represents a certain one, and "second" The one indicated and the one indicated by "third" refer to different objects. For example, if the first group of control points and the second group of control points appear, the first group of control points and the second group of control points each have It refers to different control points; in addition, the “first”, “second”, and the like in the embodiments of the present application have no sequential meaning.

It can be understood that when the CTU of the coding tree unit where the first neighboring affine coding block is located is above the current coding block position, the information of the lowest control point of the first neighboring affine coding block has been changed from Read in memory; therefore, in the above solution, in the process of constructing a candidate motion vector according to the first set of control points of the first neighboring affine coding block, the first set of control points includes the first neighboring affine coding block Lower left control point and lower right control point; instead of fixing the upper left control point, upper right control point, and lower left control point of the first adjacent coding block as the first group of control points as in the prior art (or fixed the first phase The upper left control point and the upper right control point of the neighboring coding block are used as the first group of control points). Therefore, by adopting the method for determining the first set of control points in this application, the information (for example, position coordinates, motion vectors, etc.) of the first set of control points can be directly reused from the memory, thereby reducing the probability. Read memory and improve encoding performance. In addition, since the first neighboring affine coding block is specifically specified as a four-parameter affine coding block, when the candidate motion vector is constructed based on the group control points of the first neighboring affine coding block, only the first neighboring The lower left control point and lower right control point of the affine coding block are sufficient, and no additional control points are needed, so it is further ensured that the memory read is not too high.

In a possible implementation manner, if the current coding block is a four-parameter affine coding block, the first set of candidate motion vector prediction values is used to represent an upper left control point and an upper right control point of the current coding block. , For example, substituting position coordinates of the upper left control point and the upper right control point of the current coding block into the first affine model, thereby obtaining the motion vector prediction values of the upper left control point and the upper right control point of the current coding block. , Wherein the first affine model is determined based on a motion vector and a position coordinate of a lower left control point and a lower right control point of the first adjacent affine coding block.

If the current coding block is a six-parameter affine coding block, the first set of candidate motion vector prediction values is used to represent a motion vector prediction of an upper left control point, an upper right control point, and a lower left fixed point control point of the current coding block. value. For example, the position coordinates of the upper left control point, the upper right control point, and the lower left fixed point control point of the current encoding block are substituted into the first affine model, so as to obtain the upper left control point, upper right control point, and lower left fixed point control point of the current encoding block. Motion vector prediction.

In another possible implementation manner, in the advanced motion vector prediction AMVP mode, the method further includes: using the target candidate motion vector group as a search starting point to search for a lowest cost one within a preset search range according to a rate distortion cost criterion. Motion vectors of a group of control points; then, determine a motion vector difference MVD between the motion vectors of the group of control points and the target candidate motion vector group, for example, if the first group of control points includes a first control point and The second control point, then it is necessary to determine the motion vector difference MVD between the motion vector of the first control point and the motion vector prediction value of the first control point in a set of control points represented by the target candidate motion vector group, and determine the first A motion vector difference MVD between a motion vector of two control points and a motion vector prediction value of a second control point in a set of control points represented by the target candidate motion vector group. In this case, the encoding the index corresponding to the target candidate motion vector group into a code stream to be transmitted may specifically include: encoding the MVD and an index corresponding to the target candidate motion vector group into The code stream to be transmitted.

In another optional solution, in the merge merge mode, the indexing the index corresponding to the target candidate motion vector group into a code stream to be transmitted may specifically include: combining the target candidate motion vector group with the target candidate motion vector group. The index corresponding to the group, reference frame index, and prediction direction is coded into the code stream to be transmitted.

In a possible implementation manner, the position coordinates (x ₆ , y ₆ ) of the lower left control point of the first adjacent affine coding block and the position coordinates (x ₇ , y ₇ ) of the lower right control point Both are calculated according to the position coordinates (x ₄ , y ₄ ) of the upper left control point of the first adjacent affine coding block, where the position coordinates of the lower left control point of the first adjacent affine coding block (x ₆ , y ₆ ) is (x ₄ , y ₄ + cuH), and the position coordinates (x ₇ , y ₇ ) of the lower right control point of the first adjacent affine coding block are (x ₄ + cuW, y ₄ + cuH), cuW is the width of the first neighboring affine coding block, and cuH is the height of the first neighboring affine coding block; in addition, the lower left of the first neighboring affine coding block is controlled The motion vector of the point is the motion vector of the lower left sub-block of the first adjacent affine coding block, and the motion vector of the lower right control point of the first adjacent affine coding block is the first adjacent affine coding block. Motion vector of the lower right child block. It can be seen that the position coordinates of the lower left control point and the position coordinates of the lower right control point of the first adjacent affine coding block are both derived and not read from memory, so using this method can Further reducing memory reads and improving encoding performance. As another alternative, the position coordinates of the lower left control point and the lower right control point may also be pre-selected and stored in the memory, and read from the memory when needed later.

In another optional solution, after determining the target candidate motion vector group from the candidate motion vector list according to the rate-distortion cost criterion, the method further includes: obtaining the current encoding based on the target candidate motion vector group. A motion vector of one or more sub-blocks of the block; and based on the motion vectors of the one or more sub-blocks of the current coding block, predicting a pixel prediction value of the current coding block. Optionally, when a motion vector of one or more sub-blocks of the current coding block is obtained based on the target candidate motion vector group, if a lower boundary of the current coding block is lower than a CTU of the current coding block, When the boundaries are coincident, the motion vector of the lower left sub-block of the current coding block is calculated according to the target candidate motion vector group and the position coordinate (0, H) of the lower left corner of the current coding block. The motion vectors of the sub-blocks in the lower right corner of the coding block are calculated according to the target candidate motion vector group and the position coordinates (W, H) of the lower right corner of the current coding block. For example, an affine model is constructed based on the target candidate motion vector, and then the position coordinates (0, H) of the lower left corner of the current coding block are substituted into the affine model to obtain the motion vector of the subblock in the lower left corner of the current coding block ( Instead of substituting the coordinates of the center point of the sub-block in the lower left corner into the affine model for calculation), substituting the position coordinates (W, H) of the lower right corner of the current coding block into the affine model to obtain the right of the current coding block The motion vector of the subblock in the lower corner (instead of substituting the coordinates of the center point of the subblock in the lower right corner into the affine model for calculation). In this way, the motion vector of the lower left control point and the lower right control point of the current coding block are used (for example, subsequent other blocks are constructed based on the motion vector of the lower left control point and the lower right control point of the current block). The candidate motion vector list of the other blocks) uses accurate values instead of estimated values; where W is the width of the current coding block and H is the height of the current coding block.

In a second aspect, an embodiment of the present application provides a video encoder, including several functional units for implementing any one of the methods in the first aspect. For example, a video encoder can include:

An inter prediction unit, configured to determine a target candidate motion vector group from a candidate motion vector list according to a rate distortion cost criterion; the target candidate motion vector group represents a motion vector prediction value of a set of control points of a current coding block;

An entropy coding unit, configured to encode an index corresponding to the target candidate motion vector into a code stream and transmit the code stream;

Wherein, if the first neighboring affine coding block is a four-parameter affine coding block, and the first neighboring affine coding block is located in the coding tree unit CTU above the current coding block, the candidate motion vector list A first group of candidate motion vector prediction values is included, and the first group of candidate motion vector prediction values is obtained based on a lower left control point and a lower right control point of the first neighboring affine coding block.

In a third aspect, an embodiment of the present application provides a device for encoding video data, where the device includes:

Memory for storing video data in the form of a stream;

A video encoder for determining a target candidate motion vector group from a candidate motion vector list according to a rate-distortion cost criterion; the target candidate motion vector group represents a motion vector prediction value for a set of control points of a current coding block; and Coding an index corresponding to the target candidate motion vector into a code stream, and transmitting the code stream; wherein if the first neighboring affine coding block is a four-parameter affine coding block, and the first neighboring affine coding block Is located in the coding tree unit CTU above the current coding block, the candidate motion vector list includes a first set of candidate motion vector prediction values, and the first set of candidate motion vector prediction values is based on the first phase The lower left control point and the lower right control point of the neighboring affine coding block are obtained.

In a fourth aspect, an embodiment of the present application provides an encoding device, including: a non-volatile memory and a processor coupled to each other, the processor calling program code stored in the memory to execute any one of the first aspect Some or all steps of this method.

In a fifth aspect, an embodiment of the present application provides a computer-readable storage medium, where the computer-readable storage medium stores program code, where the program code includes a part for performing any one of the methods of the first aspect or Instructions for all steps.

According to a sixth aspect, an embodiment of the present application provides a computer program product, and when the computer program product runs on a computer, the computer is caused to execute part or all of the steps of any one of the methods of the first aspect.

It should be understood that the second to sixth aspects of the present application are consistent with the technical solutions of the first aspect of the present application, and the beneficial effects obtained in each aspect and corresponding feasible implementation manners are similar, and will not be described again.

In a seventh aspect, an embodiment of the present application discloses a decoding method. The method includes parsing a bitstream to obtain an index, where the index is used to indicate a target candidate motion of a current decoding block (which may be specifically a current affine decoding block). A vector group; and then determining the target candidate motion vector group from a candidate motion vector list (for example, an affine transformation candidate motion vector list) according to the index (optionally, when the length of the candidate motion vector list is 1, It is not necessary to parse the bitstream to obtain the index, and the target motion vector group can be directly determined. The target candidate motion vector group represents the motion vector prediction value of a set of control points of the current decoding block; wherein, if the first adjacent affine decoding block is Is a four-parameter affine decoding block, and the first adjacent affine decoding block is located above the current decoding block decoding tree unit CTU, then the candidate motion vector list includes a first set of candidate motion vector prediction values, and The first group of candidate motion vector prediction values is obtained based on a lower left control point and a lower right control point of the first neighboring affine decoding block; optionally, where The construction method of the selected motion vector list may be: determine one or more of the current decoding block in the order of the neighboring block A, neighboring block B, neighboring block C, neighboring block D, and neighboring block E (as shown in FIG. 7A). Adjacent affine decoded blocks, the one or more adjacent affine decoded blocks include a first adjacent affine decoded block; and if the first adjacent affine decoded block is a four-parameter affine decoded block, Then using the first affine model to obtain the motion vector prediction value of the first set of control points of the current decoding block based on the lower left control point and the lower right control point of the first adjacent affine decoding block, where the The motion vector prediction value of the first set of control points is used as the first set of candidate motion vectors of the candidate motion vector list. After the target candidate motion vector group is determined in the above manner, an index corresponding to the target candidate motion vector is compiled into The transmitted code stream (optionally, when the length of the candidate motion vector list is 1, no index is needed to indicate the target motion vector group).

In the above method, there may be only one candidate motion vector group in the candidate motion vector list, or there may be multiple candidate motion vector groups, where each candidate motion vector group may be a motion vector binary group or a motion vector triplet . When there are multiple candidate motion vector groups, the predicted value of the first candidate motion vector group is one candidate motion vector group of the multiple candidate motion vector groups, and the other candidate motion vector groups of the multiple candidate motion vector groups are The generation principle may be the same as the generation principle of the first group of candidate motion vector prediction values, or may be different from the generation principle of the first group of candidate motion vector prediction values. Further, the target candidate motion vector group is an optimal candidate motion vector group selected from a candidate motion vector list according to a rate distortion cost criterion. If the first group of candidate motion vector prediction values is optimal, then, The selected target candidate motion vector group is the first group of candidate motion vector prediction values; if the first group of candidate motion vector prediction values is not optimal, then the selected target candidate motion vector group is not the first group of candidate motions. Vector prediction. The first adjacent affine decoding block is a four-parameter affine decoding block among the neighboring blocks of the current decoding block. The specific one is not limited here. Taking FIG. 7A as an example, it may be the neighboring block among them. A, or neighboring block B, or other neighboring blocks. In addition, "first", "second", "third", etc. appearing elsewhere in the embodiments of the present application all mean a certain meaning. Among them, "first" represents a certain one, and "second" The one indicated and the one indicated by "third" refer to different objects. For example, if the first group of control points and the second group of control points appear, the first group of control points and the second group of control points each have It refers to different control points; in addition, the “first”, “second”, and the like in the embodiments of the present application have no sequential meaning.

It can be understood that when the CTU of the decoding tree unit where the first neighboring affine decoding block is located is above the current decoding block position, the information of the lowest control point of the first neighboring affine decoding block has been changed from Read in memory; therefore, in the above solution, in the process of constructing candidate motion vectors according to the first set of control points of the first neighboring affine decoding block, the first set of control points includes the first neighboring affine decoding block Lower left control point and lower right control point; instead of fixing the upper left control point, upper right control point, and lower left control point of the first adjacent decoding block as the first group of control points as in the prior art (or fixing the first phase The upper left control point and the upper right control point of the neighboring decoding blocks are used as the first group of control points). Therefore, by adopting the method for determining the first set of control points in this application, the information (for example, position coordinates, motion vectors, etc.) of the first set of control points can be directly reused from the memory, thereby reducing the probability. Read the memory and improve decoding performance. In addition, because the first neighboring affine decoding block is specifically defined as a four-parameter affine decoding block, when the candidate motion vector is constructed based on the group control points of the first neighboring affine decoding block, only the first neighboring The lower left control point and lower right control point of the affine decoding block are sufficient, and no additional control point is needed, so it is further ensured that the memory read is not too high.

In a possible implementation manner, if the current decoding block is a four-parameter affine decoding block, the first set of candidate motion vector prediction values is used to represent an upper left control point and an upper right control point of the current decoding block. , For example, substituting position coordinates of the upper left control point and the upper right control point of the current decoding block into the first affine model, thereby obtaining the motion vector prediction values of the upper left control point and the upper right control point of the current decoding block. , Wherein the first affine model is determined based on a motion vector and a position coordinate of a lower left control point and a lower right control point of the first adjacent affine decoding block.

If the current decoding block is a six-parameter affine decoding block, the first set of candidate motion vector prediction values is used to represent motion vector prediction of the upper left control point, upper right control point, and lower left fixed point control point of the current decoding block. value. For example, the position coordinates of the upper left control point, the upper right control point, and the lower left fixed point control point of the current decoding block are substituted into the first affine model, so as to obtain the upper left control point, upper right control point, and lower left fixed point control point of the current decoding block. Motion vector prediction.

In another optional solution, the obtaining the motion vector of one or more sub-blocks of the current decoding block based on the target candidate motion vector group is specifically: obtaining the current decoding based on a second affine model. A motion vector of one or more sub-blocks of the block (for example, substituting coordinates of a center point of the one or more sub-blocks into the second affine model to obtain motion vectors of one or more sub-blocks), The two affine models are determined based on the position coordinates of the target candidate motion vector group and a set of control points of the current decoding block.

In an optional solution, in the advanced motion vector prediction AMVP mode, the obtaining a motion vector of one or more sub-blocks of the current decoding block based on the target candidate motion vector group may specifically include: The motion vector difference MVD obtained from the code stream and the target candidate motion vector group indicated by the index are used to obtain a new candidate motion vector group; and then based on the new candidate motion vector group, the current decoded block is obtained. For example, a second affine model is determined based on the position coordinates of the new candidate motion vector group and a set of control points of the current decoded block, and then based on the second affine model. A motion vector of one or more sub-blocks of the current decoding block is obtained.

In yet another possible implementation manner, in a merge merge mode, the obtaining a pixel prediction value of the current decoded block based on the motion vector of one or more sub-blocks of the current decoded block may specifically include: According to the motion vector of one or more sub-blocks of the current decoding block, and the reference frame index and prediction direction indicated by the index, a pixel prediction value of the current decoding block is obtained by prediction.

In yet another optional solution, the position coordinates (x ₆ , y ₆ ) of the lower left control point of the first adjacent affine decoding block and the position coordinates (x ₇ , y ₇ ) of the lower right control point ) Are calculated according to the position coordinates (x ₄ , y ₄ ) of the upper left control point of the first adjacent affine decoding block, where the position of the lower left control point of the first adjacent affine decoding block is The coordinates (x ₆ , y ₆ ) are (x ₄ , y ₄ + cuH), and the position coordinates (x ₇ , y ₇ ) of the lower right control point of the first adjacent affine decoding block are (x ₄ + cuW) , Y ₄ + cuH), cuW is the width of the first neighboring affine decoding block, and cuH is the height of the first neighboring affine decoding block; in addition, the bottom left of the first neighboring affine decoding block The motion vector of the control point is the motion vector of the lower left sub-block of the first adjacent affine decoding block, and the motion vector of the lower right control point of the first adjacent affine decoding block is the first adjacent affine decoding The motion vector of the block's bottom-right child block. It can be seen that the position coordinates of the lower left control point and the position coordinates of the lower right control point of the first adjacent affine decoding block are both derived and not read from the memory, so using this method can Further reducing memory reads and improving decoding performance. As another alternative, the position coordinates of the lower left control point and the lower right control point may also be pre-selected and stored in the memory, and read from the memory when needed later.

In another optional solution, when the motion vectors of one or more sub-blocks of the current decoding block are obtained based on the target candidate motion vector group, if the lower boundary of the current decoding block and the current decoding The lower bounds of the CTUs where the blocks are located coincide, the motion vector of the sub-left corner of the current decoding block is the position coordinate (0, H) according to the target candidate motion vector group and the bottom-left corner of the current decoding block. It is calculated that the motion vector of the sub-block in the lower right corner of the current decoding block is calculated according to the target candidate motion vector group and the position coordinates (W, H) of the lower right corner of the current decoding block. For example, an affine model is constructed based on the target candidate motion vector, and then the position coordinates (0, H) of the lower left corner of the current decoded block are substituted into the affine model to obtain the motion vector of the subblock in the lower left corner of the current decoded block ( Instead of substituting the coordinates of the center point of the subblock in the lower left corner into the affine model for calculation), substituting the position coordinates (W, H) of the lower right corner of the current decoded block into the affine model to obtain the right of the current decoded block The motion vector of the subblock in the lower corner (instead of substituting the coordinates of the center point of the subblock in the lower right corner into the affine model for calculation). In this way, the motion vector of the lower left control point and the lower right control point of the current decoding block are used (for example, the subsequent other blocks are constructed based on the motion vector of the lower left control point and the lower right control point of the current block). The candidate motion vector lists of the other blocks) use accurate values instead of estimated values. Wherein, W is the width of the current decoded block, and H is the height of the current decoded block.

In an eighth aspect, an embodiment of the present application provides a video decoder. The video decoder includes:

An entropy decoding unit, configured to parse a code stream to obtain an index, where the index is used to indicate a target candidate motion vector group of a current decoding block;

An inter prediction unit, configured to determine the target candidate motion vector group from a candidate motion vector list according to the index, where the target candidate motion vector group represents a motion vector prediction value of a set of control points of a current decoding block, where If the first neighboring affine decoding block is a four-parameter affine decoding block and the first neighboring affine decoding block is located above the current decoding block decoding tree unit CTU, the list of candidate motion vectors includes A first set of candidate motion vector prediction values, the first set of candidate motion vector prediction values being obtained based on a lower left control point and a lower right control point of the first adjacent affine decoding block; and based on the target candidate motion The vector group obtains a motion vector of one or more sub-blocks of the current decoding block; based on the motion vectors of the one or more sub-blocks of the current decoding block, predicts and obtains a pixel prediction value of the current decoding block.

In a ninth aspect, an embodiment of the present application provides a device for decoding video data, where the device includes:

Memory for storing video data in the form of a stream;

A video decoder for parsing a bitstream to obtain an index, the index indicating a target candidate motion vector group of a current decoding block; and for determining the target candidate motion from a candidate motion vector list according to the index Vector group, the target candidate motion vector group represents a motion vector prediction value of a set of control points of the current decoding block, wherein if the first adjacent affine decoding block is a four-parameter affine decoding block, and the first phase The neighboring affine decoding block is located above the current decoding block CTU, then the candidate motion vector list includes a first set of candidate motion vector prediction values, and the first set of candidate motion vector prediction values is based on the first Obtained from the lower left control point and the lower right control point of an adjacent affine decoding block; and obtaining a motion vector of one or more sub-blocks of the current decoding block based on the target candidate motion vector group; based on the current decoding block And predicting a motion vector of one or more sub-blocks to obtain a pixel prediction value of the current decoded block.

According to a tenth aspect, an embodiment of the present application provides a decoding device, including: a non-volatile memory and a processor coupled to each other, the processor invoking program code stored in the memory to execute any one of the seventh aspects Some or all steps of this method.

According to an eleventh aspect, an embodiment of the present application provides a computer-readable storage medium, where the computer-readable storage medium stores program code, where the program code includes a part for performing any one of the methods of the seventh aspect Or all step instructions.

In a twelfth aspect, an embodiment of the present application provides a computer program product, and when the computer program product runs on a computer, the computer is caused to execute part or all of the steps of any one of the methods in the seventh aspect.

It should be understood that the eighth to twelfth aspects of the present application are consistent with the technical solution of the seventh aspect of the present application, and the beneficial effects obtained in each aspect and corresponding feasible implementation manners are similar, and will not be described again.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to more clearly explain the technical solutions in the embodiments of the present application or the background art, the drawings that are needed in the embodiments of the present application or the background art will be described below.

FIG. 1 is a schematic block diagram of a video encoding and decoding system according to an embodiment of the present application; FIG.

2A is a schematic block diagram of a video encoder according to an embodiment of the present application;

2B is a schematic block diagram of a video decoder according to an embodiment of the present application;

3 is a flowchart of a method for inter prediction of an encoded video image according to an embodiment of the present application;

4 is a flowchart of a method for decoding an inter prediction of a video image according to an embodiment of the present application;

5 is a schematic diagram of motion information of a current image block and a reference block in an embodiment of the present application;

6 is a schematic flowchart of an encoding method according to an embodiment of the present application;

FIG. 7A is a schematic diagram of a scenario of an adjacent block provided by an embodiment of the present application; FIG.

7B is a schematic diagram of a scenario of an adjacent block provided by an embodiment of the present application;

8A is a schematic structural diagram of a motion compensation unit according to an embodiment of the present application;

8B is a schematic structural diagram of still another motion compensation unit according to an embodiment of the present application;

9 is a schematic flowchart of a decoding method according to an embodiment of the present application;

9A is a schematic flowchart of constructing a candidate motion vector list according to an embodiment of the present application;

10 is a schematic structural diagram of an encoding device or a decoding device according to an embodiment of the present invention;

FIG. 11 is a video encoding system 1100 including the encoder 20 of FIG. 2A and / or the decoder 200 of FIG. 2B according to an exemplary embodiment.

detailed description

The following describes the embodiments of the present application with reference to the drawings in the embodiments of the present application.

Non-translational motion model prediction refers to the use of the same motion model on the codec side (e.g., video encoder and video decoder ends) to derive the value of each sub-motion compensation unit (also known as a sub-block) in the current encoding / decoding block. The motion information (such as a motion vector) is subjected to motion compensation according to the motion information of the sub motion compensation unit to obtain a prediction block, thereby improving prediction efficiency. The process of deriving motion information of a motion compensation unit (also called a sub-block) in the current encoding / decoding block involves motion vector prediction based on the motion model. Currently, the upper left of the adjacent affine decoding block of the current encoding / decoding block is usually used The affine model is derived from the position coordinates and motion vectors of the control point, the upper right control point, the lower left control point, and the motion vector; and then the motion vector prediction value of a set of control points of the current encoding / decoding block is derived according to the affine model as the candidate motion vector A set of candidate motion vector predictions in a list. However, the position coordinates and motion vectors of the upper-left control point, upper-right control point, lower-left control point of adjacent affine decoding blocks used in the motion vector prediction process need to be read from memory in real time, which will increase the memory read pressure. The embodiment of the present application focuses on how to reduce the memory read pressure, which involves the optimization of the encoding and decoding ends. In order to better understand the idea of the embodiment of the present application, the application scenario of the embodiment of the present application is first introduced below.

Encoding a video stream, or a portion thereof, such as a video frame or an image block, can use temporal and spatial similarities in the video stream to improve encoding performance. For example, the current image block of a video stream can predict motion information for the current image block based on previously encoded blocks in the video stream, and identify the difference between the predicted block and the current image block (that is, the original block) (also known as the original block) Is the residual), thereby encoding the current image block based on the previously encoded block. In this way, only the residuals and some parameters used to generate the current image block are included in the digital video output bitstream, rather than the entirety of the current image block is included in the digital video output bitstream. This technique can be called inter prediction.

The motion vector is an important parameter in the inter prediction process, which represents the spatial displacement of a previously coded block relative to the current coded block. Motion vectors can be obtained using motion estimation methods, such as motion search. In the early inter-prediction technology, the bits representing the motion vector were included in the encoded bit stream to allow the decoder to reproduce the predicted block and then obtain the reconstructed block. In order to further improve the coding efficiency, it was later proposed to use the reference motion vector to differentially encode the motion vector, that is, instead of encoding the entire motion vector, only the difference between the motion vector and the reference motion vector was encoded. In some cases, the reference motion vector may be selected from previously used motion vectors in the video stream. Selecting a previously used motion vector to encode the current motion vector can further reduce the number of bits included in the encoded video bitstream .

FIG. 1 is a block diagram of a video decoding system 1 according to an example described in the embodiment of the present application. As used herein, the term "video coder" generally refers to both video encoders and video decoders. In this application, the terms "video coding" or "coding" may generally refer to video encoding or video decoding. The video encoder 100 and the video decoder 200 of the video decoding system 1 are configured to predict a current coded image block according to various method examples described in any of a variety of new inter prediction modes proposed in the present application. The motion information of the sub-block or its sub-blocks, such as the motion vector, makes the predicted motion vector close to the motion vector obtained using the motion estimation method to the greatest extent, so that the motion vector difference is not transmitted during encoding, thereby further improving the encoding and decoding performance.

As shown in FIG. 1, the video decoding system 1 includes a source device 10 and a destination device 20. The source device 10 generates encoded video data. Therefore, the source device 10 may be referred to as a video encoding device. The destination device 20 may decode the encoded video data generated by the source device 10. Therefore, the destination device 20 may be referred to as a video decoding device. Various implementations of the source device 10, the destination device 20, or both may include one or more processors and a memory coupled to the one or more processors. The memory may include, but is not limited to, RAM, ROM, EEPROM, flash memory, or any other media that can be used to store the desired program code in the form of instructions or data structures accessible by a computer, as described herein.

The source device 10 and the destination device 20 may include various devices including desktop computers, mobile computing devices, notebook (e.g., laptop) computers, tablet computers, set-top boxes, telephone handsets, such as so-called "smart" phones, etc. Cameras, televisions, cameras, display devices, digital media players, video game consoles, on-board computers, or the like.

The destination device 20 may receive the encoded video data from the source device 10 via the link 30. The link 30 may include one or more media or devices capable of moving the encoded video data from the source device 10 to the destination device 20. In one example, the link 30 may include one or more communication media enabling the source device 10 to directly transmit the encoded video data to the destination device 20 in real time. In this example, the source device 10 may modulate the encoded video data according to a communication standard, such as a wireless communication protocol, and may transmit the modulated video data to the destination device 20. The one or more communication media may include wireless and / or wired communication media, such as a radio frequency (RF) spectrum or one or more physical transmission lines. The one or more communication media may form part of a packet-based network, such as a local area network, a wide area network, or a global network (eg, the Internet). The one or more communication media may include a router, a switch, a base station, or other devices that facilitate communication from the source device 10 to the destination device 20.

In another example, the encoded data may be output from the output interface 140 to the storage device 40. Similarly, the encoded data can be accessed from the storage device 40 through the input interface 240. The storage device 40 may include any of a variety of distributed or locally-accessed data storage media, such as a hard drive, Blu-ray disc, DVD, CD-ROM, flash memory, volatile or non-volatile memory, Or any other suitable digital storage medium for storing encoded video data.

In another example, the storage device 40 may correspond to a file server or another intermediate storage device that may hold the encoded video produced by the source device 10. The destination device 20 may access the stored video data from the storage device 40 via streaming or download. The file server may be any type of server capable of storing encoded video data and transmitting the encoded video data to the destination device 20. Example file servers include a web server (eg, for a website), an FTP server, a network attached storage (NAS) device, or a local disk drive. The destination device 20 can access the encoded video data through any standard data connection, including an Internet connection. This may include a wireless channel (eg, a Wi-Fi connection), a wired connection (eg, DSL, cable modem, etc.), or a combination of both suitable for accessing encoded video data stored on a file server. The transmission of the encoded video data from the storage device 40 may be a streaming transmission, a download transmission, or a combination of the two.

The motion vector prediction technology of the present application can be applied to video codecs to support a variety of multimedia applications, such as over-the-air television broadcasting, cable television transmission, satellite television transmission, streaming video transmission (e.g., via the Internet), for storage in data storage Encoding of video data on media, decoding of video data stored on data storage media, or other applications. In some examples, the video coding system 1 may be used to support one-way or two-way video transmission to support applications such as video streaming, video playback, video broadcasting, and / or video telephony.

The video decoding system 1 illustrated in FIG. 1 is merely an example, and the techniques of the present application can be applied to a video decoding setting (for example, video encoding or video decoding) that does not necessarily include any data communication between the encoding device and the decoding device. . In other examples, data is retrieved from local storage, streamed over a network, and so on. The video encoding device may encode the data and store the data to a memory, and / or the video decoding device may retrieve the data from the memory and decode the data. In many instances, encoding and decoding are performed by devices that do not communicate with each other, but only encode data to and / or retrieve data from memory and decode data.

In the example of FIG. 1, the source device 10 includes a video source 120, a video encoder 100, and an output interface 140. In some examples, the output interface 140 may include a regulator / demodulator (modem) and / or a transmitter. Video source 120 may include a video capture device (e.g., a video camera), a video archive containing previously captured video data, a video feed interface to receive video data from a video content provider, and / or a computer for generating video data Graphics systems, or a combination of these sources of video data.

The video encoder 100 may encode video data from the video source 120. In some examples, the source device 10 transmits the encoded video data directly to the destination device 20 via the output interface 140. In other examples, the encoded video data may also be stored on the storage device 40 for later access by the destination device 20 for decoding and / or playback.

In the example of FIG. 1, the destination device 20 includes an input interface 240, a video decoder 200, and a display device 220. In some examples, the input interface 240 includes a receiver and / or a modem. The input interface 240 may receive the encoded video data via the link 30 and / or from the storage device 40. The display device 220 may be integrated with the destination device 20 or may be external to the destination device 20. Generally, the display device 220 displays decoded video data. The display device 220 may include various display devices, such as a liquid crystal display (LCD), a plasma display, an organic light emitting diode (OLED) display, or other types of display devices.

Although not illustrated in FIG. 1, in some aspects, video encoder 100 and video decoder 200 may each be integrated with an audio encoder and decoder, and may include an appropriate multiplexer-demultiplexer unit Or other hardware and software to handle encoding of both audio and video in a common or separate data stream. In some examples, the MUX-DEMUX unit may conform to the ITU H.223 multiplexer protocol, or other protocols such as the User Datagram Protocol (UDP), if applicable.

Video encoder 100 and video decoder 200 may each be implemented as any of a variety of circuits such as one or more microprocessors, digital signal processors (DSPs), application specific integrated circuits (ASICs), Field Programmable Gate Array (FPGA), discrete logic, hardware, or any combination thereof. If the present application is implemented partially in software, the device may store instructions for the software in a suitable non-volatile computer-readable storage medium and may use one or more processors to execute the instructions in hardware Thus implementing the technology of the present application. Any of the foregoing (including hardware, software, a combination of hardware and software, etc.) may be considered as one or more processors. Each of video encoder 100 and video decoder 200 may be included in one or more encoders or decoders, any of which may be integrated as a combined encoder in a corresponding device / Decoder (codec).

This application may generally refer to video encoder 100 as "signaling" or "transmitting" certain information to another device, such as video decoder 200. The terms "signaling" or "transmitting" may generally refer to the transmission of syntax elements and / or other data to decode the compressed video data. This transfer can occur in real time or almost real time. Alternatively, this communication may occur after a period of time, such as may occur when a syntax element is stored in a coded bit stream to a computer-readable storage medium at the time of encoding, and the decoding device may then after the syntax element is stored to this medium Retrieve the syntax element at any time.

The video encoder 100 and the video decoder 200 may operate according to a video compression standard such as High Efficiency Video Coding (HEVC) or an extension thereof, and may conform to the HEVC test model (HM). Alternatively, video encoder 100 and video decoder 200 may also operate according to other industry standards, such as the ITU-T H.264, H.265 standards, or extensions of such standards. However, the techniques of this application are not limited to any particular codec standard.

In an example, referring to FIG. 3 together, the video encoder 100 is configured to encode a syntax element related to an image block to be currently encoded into a digital video output bit stream (referred to as a bit stream or a code stream), which will be used here. The syntax element for inter prediction on the current image block is referred to as inter prediction data for short; in order to determine the inter prediction mode used to encode the current image block, the video encoder 100 is further configured to determine (S301) the candidate inter frame The inter prediction mode in the prediction mode set used to perform inter prediction on the current image block (for example, selecting a variety of new inter prediction modes to compromise the code rate of the current image block or the minimum inter prediction mode) And encoding the current image block based on the determined inter prediction mode (S303), the encoding process herein may include predicting motion information of one or more sub-blocks in the current image block based on the determined inter prediction mode ( Specifically, it may be motion information of each sub-block or all sub-blocks), and use the motion information of one or more sub-blocks in the current image block to perform frame processing on the current image block. Inter prediction

It should be understood that if the difference (that is, the residual) between the prediction block generated by the motion information predicted based on the new inter prediction mode proposed in the present application and the current image block (that is, the original block) to be encoded is 0 , The video encoder 100 only needs to program the syntax elements related to the image block to be encoded into a bit stream (also known as a code stream); otherwise, in addition to the syntax elements, the corresponding residuals need to be coded into bits flow.

In another example, referring to FIG. 4 together, the video decoder 200 is configured to decode a syntax element related to the image block to be decoded from the bit stream (S401), and when the inter prediction data indicates that a candidate is adopted When a set of inter prediction modes (that is, a new inter prediction mode) is used to predict the current image block, an inter prediction mode in the candidate inter prediction mode set for performing inter prediction on the current image block is determined (S403 ), And decoding the current image block based on the determined inter prediction mode (S405), the decoding process herein may include predicting motion information of one or more sub-blocks in the current image block based on the determined inter prediction mode, Inter motion prediction is performed on the current image block by using motion information of one or more sub-blocks in the current image block.

Optionally, if the inter prediction data further includes a second identifier for indicating which inter prediction mode the current image block uses, the video decoder 200 is configured to determine the inter prediction indicated by the second identifier. The mode is an inter prediction mode for performing inter prediction on the current image block; or, if the inter prediction data does not include a second identifier used to indicate which inter prediction mode is used by the current image block The video decoder 200 is configured to determine that a first inter prediction mode used for a non-directional motion field is an inter prediction mode used for inter prediction of the current image block.

FIG. 2A is a block diagram of a video encoder 100 according to an example described in the embodiment of the present application. The video encoder 100 is configured to output a video to the post-processing entity 41. The post-processing entity 41 represents an example of a video entity that can process the encoded video data from the video encoder 100, such as a media-aware network element (MANE) or a stitching / editing device. In some cases, the post-processing entity 41 may be an instance of a network entity. In some video encoding systems, the post-processing entity 41 and the video encoder 100 may be parts of separate devices, while in other cases, the functionality described with respect to the post-processing entity 41 may be performed by the same device including the video encoder 100 carried out. In a certain example, the post-processing entity 41 is an example of the storage device 40 of FIG. 1.

The video encoder 100 may perform encoding of a video image block according to any new inter prediction mode set of candidate inter prediction mode

sets including modes

0, 1, 2,... Or 10 proposed in the present application, for example, perform a video image block. Inter prediction.

In the example of FIG. 2A, the video encoder 100 includes a prediction processing unit 108, a filter unit 106, a decoded image buffer unit (DPB) 107, a summing unit 112, a transform unit 101, a quantization unit 102, and an entropy encoding unit 103. The prediction processing unit 108 includes an inter prediction unit 110 and an intra prediction unit 109. For image block reconstruction, the video encoder 100 further includes an inverse quantization unit 104, an inverse transform unit 105, and a summing unit 111. The filter unit 106 is intended to represent one or more loop filtering units, such as a deblocking filtering unit, an adaptive loop filtering unit (ALF), and a sample adaptive offset (SAO) filtering unit. Although the filtering unit 106 is shown as an in-loop filter in FIG. 2A, in other implementations, the filtering unit 106 may be implemented as a post-loop filter. In one example, the video encoder 100 may further include a video data storage unit and a segmentation unit (not shown in the figure).

The video data storage unit may store video data to be encoded by the components of the video encoder 100. The video data stored in the video data storage unit may be obtained from the video source 120. The DPB 107 may be a reference image storage unit that stores reference video data used by the video encoder 100 to encode video data in an intra-frame or inter-frame decoding mode. The video data storage unit and the DPB 107 may be formed by any of a variety of storage unit devices, such as a dynamic random access memory unit (DRAM), a synchronous resistive RAM (MRAM), a resistive RAM ( RRAM), or other types of memory cell devices. The video data storage unit and the DPB 107 may be provided by the same storage unit device or a separate storage unit device. In various examples, the video data storage unit may be on-chip with other components of video encoder 100, or off-chip with respect to those components.

As shown in FIG. 2A, the video encoder 100 receives video data and stores the video data in a video data storage unit. The segmentation unit divides the video data into several image blocks, and these image blocks can be further divided into smaller blocks, such as image block segmentation based on a quad tree structure or a binary tree structure. This segmentation may also include segmentation into slices, tiles, or other larger units. Video encoder 100 typically illustrates components that encode image blocks within a video slice to be encoded. The slice can be divided into multiple image patches (and possibly into a collection of image patches called slices). The prediction processing unit 108 may select one of a plurality of possible decoding modes for the current image block, such as one of a plurality of intra-coding modes or one of a plurality of inter-coding modes, wherein The multiple inter-frame decoding modes include, but are not limited to, one or more of the

modes

0, 1, 2, 3 ... 10 proposed in the present application. The prediction processing unit 108 may provide the obtained intra, inter-coded block to the summing unit 112 to generate a residual block, and to the summing unit 111 to reconstruct an encoded block used as a reference image.

The intra prediction unit 109 within the prediction processing unit 108 may perform intra predictive encoding of the current image block with respect to one or more neighboring blocks in the same frame or slice as the current block to be encoded to remove spatial redundancy. . The inter-prediction unit 110 within the prediction processing unit 108 may perform inter-predictive encoding of the current image block with respect to one or more prediction blocks in the one or more reference images to remove temporal redundancy.

Specifically, the inter prediction unit 110 may be configured to determine an inter prediction mode for encoding a current image block. For example, the inter-prediction unit 110 may use rate-distortion analysis to calculate rate-distortion values of various inter-prediction modes in the candidate inter-prediction mode set, and select an inter-frame having the best rate-distortion characteristics from among Forecasting mode. Rate distortion analysis generally determines the amount of distortion (or error) between the coded block and the original uncoded block that was coded to produce the coded block, and the bit rate used to generate the coded block (that is, , Number of bits). For example, the inter-prediction unit 110 may determine that the inter-prediction mode with the lowest code rate distortion cost of encoding the current image block in the set of candidate inter-prediction modes is the inter-prediction mode for inter-prediction of the current image block. The following describes the inter-predictive coding process in detail, especially in the various inter-prediction modes for non-directional or directional sports fields in this application, predicting one or more sub-blocks (specifically, each Sub-block or all sub-blocks).

The inter prediction unit 110 is configured to predict motion information (such as a motion vector) of one or more subblocks in the current image block based on the determined inter prediction mode, and use the motion information (such as the motion vector) of one or more subblocks in the current image block. Motion vector) to obtain or generate a prediction block of the current image block. The inter prediction unit 110 may locate a prediction block pointed to by the motion vector in one of the reference image lists. The inter prediction unit 110 may also generate syntax elements associated with image blocks and video slices for use by the video decoder 200 when decoding image blocks of the video slices. In another example, the inter prediction unit 110 uses the motion information of each sub-block to perform a motion compensation process to generate a prediction block of each sub-block, thereby obtaining a prediction block of the current image block. It should be understood that the The inter prediction unit 110 performs motion estimation and motion compensation processes.

Specifically, after the inter prediction mode is selected for the current image block, the inter prediction unit 110 may provide information indicating the selected inter prediction mode of the current image block to the entropy encoding unit 103, so that the entropy encoding unit 103 encodes the instruction. Information on the selected inter prediction mode. In this application, the video encoder 100 may include inter prediction data related to the current image block in the transmitted bit stream, which may include a first identifier block_based_enable_flag to indicate whether the new image proposed by the present application is adopted for the current image block. The inter prediction mode is used for inter prediction; optionally, a second identifier block_based_index may also be included to indicate which new inter prediction mode is used by the current image block. In the present application, in

different modes

0, 1, 2, ..., 10, a process of predicting a motion vector of a current image block or a sub-block thereof using motion vectors of multiple reference blocks will be described in detail below.

The intra prediction unit 109 may perform intra prediction on the current image block. Specifically, the intra prediction unit 109 may determine an intra prediction mode used to encode the current block. For example, the intra-prediction unit 109 may use rate-distortion analysis to calculate rate-distortion values for various intra-prediction modes to be tested, and select an intra-prediction with the best rate-distortion characteristics from the test modes. mode. In any case, after the intra prediction mode is selected for the image block, the intra prediction unit 109 may provide information indicating the selected intra prediction mode of the current image block to the entropy encoding unit 103 so that the entropy encoding unit 103 encodes the instruction Information on the selected intra prediction mode.

After the prediction processing unit 108 generates a prediction block of the current image block via inter prediction and intra prediction, the video encoder 100 forms a residual image block by subtracting the prediction block from the current image block to be encoded. The summing unit 112 represents one or more components that perform this subtraction operation. The residual video data in the residual block may be included in one or more TUs and applied to the transform unit 101. The transform unit 101 transforms the residual video data into a residual transform coefficient using a transform such as a discrete cosine transform (DCT) or a conceptually similar transform. The transform unit 101 may transform the residual video data from a pixel value domain to a transform domain, such as a frequency domain.

The transformation unit 101 may send the obtained transformation coefficient to the quantization unit 102. The quantization unit 102 quantizes the transform coefficients to further reduce the bit rate. In some examples, the quantization unit 102 may then perform a scan of a matrix containing the quantized transform coefficients. Alternatively, the entropy encoding unit 103 may perform scanning.

After quantization, the entropy encoding unit 103 performs entropy encoding on the quantized transform coefficients. For example, the entropy encoding unit 103 may perform context adaptive variable length coding (CAVLC), context adaptive binary arithmetic coding (CABAC), syntax-based context adaptive binary arithmetic coding (SBAC), and probability interval segmentation entropy (PIPE ) Coding or another entropy coding method or technique. After entropy encoding by the entropy encoding unit 103, the encoded bitstream may be transmitted to the video decoder 200, or archived for later transmission or retrieved by the video decoder 200. The entropy encoding unit 103 may also perform entropy encoding on the syntax elements of the current image block to be encoded.

The inverse quantization unit 104 and the inverse transform unit 105 respectively apply inverse quantization and inverse transform to reconstruct the residual block in the pixel domain, for example, as a reference block for later use as a reference image. The summing unit 111 adds the reconstructed residual block to a prediction block generated by the inter prediction unit 110 or the intra prediction unit 109 to generate a reconstructed image block. The filter unit 106 may be adapted to reconstructed image blocks to reduce distortion, such as block artifacts. This reconstructed image block is then stored as a reference block in the decoded image buffer unit 107 and can be used as a reference block by the inter prediction unit 110 to perform inter prediction on subsequent video frames or blocks in the image.

It should be understood that other structural changes of the video encoder 100 may be used to encode a video stream. For example, for some image blocks or image frames, the video encoder 100 may directly quantize the residual signal without processing by the transform unit 101 and correspondingly does not need to be processed by the inverse transform unit 105; or, for some image blocks, Or image frames, the video encoder 100 does not generate residual data, and accordingly does not need to be processed by the transform unit 101, the quantization unit 102, the inverse quantization unit 104, and the inverse transform unit 105; or, the video encoder 100 may convert the reconstructed image The blocks are directly stored as reference blocks without being processed by the filter unit 106; alternatively, the quantization unit 102 and the inverse quantization unit 104 in the video encoder 100 may be merged together. The loop filtering unit is optional, and in the case of lossless compression coding, the transform unit 101, the quantization unit 102, the inverse quantization unit 104, and the inverse transform unit 105 are optional. It should be understood that, according to different application scenarios, the inter prediction unit and the intra prediction unit may be selectively enabled, and in this case, the inter prediction unit is enabled.

FIG. 2B is a block diagram of a video decoder 200 according to an example described in the embodiment of the present application. In the example of FIG. 2B, the video decoder 200 includes an entropy decoding unit 203, a prediction processing unit 208, an inverse quantization unit 204, an inverse transform unit 205, a summing unit 211, a filter unit 206, and a decoded image buffer unit 207. The prediction processing unit 208 may include an inter prediction unit 210 and an intra prediction unit 209. In some examples, video decoder 200 may perform a decoding process that is substantially inverse to the encoding process described with respect to video encoder 100 from FIG. 2A.

During the decoding process, the video decoder 200 receives from the video encoder 100 an encoded video bitstream representing image blocks of the encoded video slice and associated syntax elements. The video decoder 200 may receive video data from the network entity 42, optionally, the video data may also be stored in a video data storage unit (not shown in the figure). The video data storage unit may store video data, such as an encoded video bit stream, to be decoded by the components of the video decoder 200. The video data stored in the video data storage unit can be obtained, for example, from the storage device 40, from a local video source such as a camera, via a wired or wireless network of video data, or by accessing a physical data storage medium. The video data storage unit may function as a decoded image buffer unit (CPB) for storing encoded video data from the encoded video bitstream. Therefore, although the video data storage unit is not illustrated in FIG. 2B, the video data storage unit and the DPB 207 may be the same storage unit, or may be separate storage units. The video data storage unit and DPB 207 can be formed by any of a variety of storage unit devices, such as: dynamic random access memory unit (DRAM) including synchronous DRAM (SDRAM), magnetoresistive RAM (MRAM), and resistive RAM (RRAM), or other types of memory cell devices. In various examples, the video data storage unit may be integrated on a chip with other components of the video decoder 200, or disposed off-chip relative to those components.

The network entity 42 may be, for example, a server, a MANE, a video editor / splicer, or other such device for implementing one or more of the techniques described above. The network entity 42 may or may not include a video encoder, such as video encoder 100. Before the network entity 42 sends the encoded video bitstream to the video decoder 200, the network entity 42 may implement some of the techniques described in this application. In some video decoding systems, the network entity 42 and the video decoder 200 may be part of separate devices, while in other cases, the functionality described with respect to the network entity 42 may be performed by the same device including the video decoder 200. In some cases, the network entity 42 may be an example of the storage device 40 of FIG. 1.

The entropy decoding unit 203 of the video decoder 200 performs entropy decoding on the bit stream to generate quantized coefficients and some syntax elements. The entropy decoding unit 203 forwards the syntax element to the prediction processing unit 208. Video decoder 200 may receive syntax elements at a video slice level and / or an image block level.

When a video slice is decoded into an intra-decoded (I) slice, the intra-prediction unit 209 of the prediction processing unit 208 may be based on the signaled intra-prediction mode and the previous decoded block from the current frame or image. Data to generate prediction blocks for image blocks of the current video slice. When a video slice is decoded into an inter-decoded (ie, B or P) slice, the inter-prediction unit 210 of the prediction processing unit 208 may determine, based on the syntax element received from the entropy decoding unit 203, the An inter prediction mode in which a current image block of a video slice is decoded, and based on the determined inter prediction mode, the current image block is decoded (for example, inter prediction is performed). Specifically, the inter prediction unit 210 may determine whether to use the new inter prediction mode for prediction of the current image block of the current video slice. If the syntax element indicates that the new inter prediction mode is used to predict the current image block, based on A new inter prediction mode (for example, a new inter prediction mode specified by a syntax element or a default new inter prediction mode) predicts the current image block of the current video slice or a sub-block of the current image block. Motion information, thereby obtaining or generating a predicted block of the current image block or a sub-block of the current image block by using the motion information of the predicted current image block or a sub-block of the current image block through a motion compensation process. The motion information here may include reference image information and motion vectors, where the reference image information may include but is not limited to unidirectional / bidirectional prediction information, a reference image list number, and a reference image index corresponding to the reference image list. For inter prediction, a prediction block may be generated from one of reference pictures within one of the reference picture lists. The video decoder 200 may construct a reference image list, that is, a list 0 and a list 1, based on the reference images stored in the DPB 207. The reference frame index of the current image may be included in one or more of the reference frame list 0 and list 1. In some examples, the video encoder 100 may signal whether to use a new inter prediction mode to decode a specific syntax element of a specific block, or may be a signal to indicate whether to use a new inter prediction mode. And indicating which new inter prediction mode is used to decode a specific syntax element of a specific block. It should be understood that the inter prediction unit 210 here performs a motion compensation process. In the following, the inter-prediction process of using the motion information of the reference block to predict the motion information of the current image block or a sub-block of the current image block under various new inter-prediction modes will be explained in detail.

The inverse quantization unit 204 inverse quantizes the quantized transform coefficients provided in the bitstream and decoded by the entropy decoding unit 203, that is, dequantization. The inverse quantization process may include using a quantization parameter calculated by the video encoder 100 for each image block in the video slice to determine the degree of quantization that should be applied and similarly to determine the degree of inverse quantization that should be applied. The inverse transform unit 205 applies an inverse transform to transform coefficients, such as an inverse DCT, an inverse integer transform, or a conceptually similar inverse transform process in order to generate a residual block in the pixel domain.

After the inter-prediction unit 210 generates a prediction block for the current image block or a sub-block of the current image block, the video decoder 200 passes the residual block from the inverse transform unit 205 and the corresponding prediction generated by the inter-prediction unit 210. The blocks are summed to get the reconstructed block, that is, the decoded image block. The summing unit 211 represents a component that performs this summing operation. When needed, a loop filtering unit (in the decoding loop or after the decoding loop) can also be used to smooth pixel transitions or otherwise improve video quality. The filter unit 206 may represent one or more loop filtering units, such as a deblocking filtering unit, an adaptive loop filtering unit (ALF), and a sample adaptive offset (SAO) filtering unit. Although the filtering unit 206 is shown as an in-loop filtering unit in FIG. 2B, in other implementations, the filtering unit 206 may be implemented as a post-loop filtering unit. In one example, the filter unit 206 is adapted to reconstruct a block to reduce block distortion, and the result is output as a decoded video stream. Moreover, the decoded image block in a given frame or image may also be stored in the decoded image buffer unit 207, and the decoded image buffer unit 207 stores a reference image for subsequent motion compensation. The decoded image buffer unit 207 may be part of a storage unit, which may also store the decoded video for later presentation on a display device, such as the display device 220 of FIG. 1, or may be separate from such a storage unit.

It should be understood that other structural variations of the video decoder 200 may be used to decode the encoded video bitstream. For example, the video decoder 200 may generate an output video stream without being processed by the filtering unit 206; or, for certain image blocks or image frames, the entropy decoding unit 203 of the video decoder 200 does not decode the quantized coefficients, and accordingly does not It needs to be processed by the inverse quantization unit 204 and the inverse transform unit 205. The loop filtering unit is optional; and in the case of lossless compression, the inverse quantization unit 204 and the inverse transform unit 205 are optional. It should be understood that, according to different application scenarios, the inter prediction unit and the intra prediction unit may be selectively enabled, and in this case, the inter prediction unit is enabled.

FIG. 5 is a schematic diagram illustrating motion information of an exemplary current image block 600 and a reference block in an embodiment of the present application. As shown in FIG. 5, W and H are the width and height of the current image block 600 and a co-located block (referred to as a co-located block) 600 'of the same position of the current image block 600. The reference blocks of the current image block 600 include: the upper airspace neighboring block and the left airspace neighboring block of the current image block 600, and the lower airspace neighboring block and the right airspace neighboring block of the collocated block 600 ', where the collocated block 600 'Is an image block in the reference image having the same size, shape, and coordinates as the current image block 600. It should be noted that the motion information of the lower spatial domain neighboring block and the right spatial domain neighboring block of the current image block does not exist and has not been encoded yet. It should be understood that the current image block 600 and the collocated block 600 'may be any block size. For example, the current image block 600 and the collocated block 600 'may include, but are not limited to, 16x16 pixels, 32x32 pixels, 32x16 pixels, 16x32 pixels, and the like. As described above, each image frame can be divided into image blocks for encoding. These image blocks can be further divided into smaller blocks, for example, the current image block 600 and the collocated block 600 'can be divided into multiple MxN sub-blocks, that is, each sub-block is MxN pixels in size, and each reference The size of the block is also MxN pixels, that is, the same size as the sub-block of the current image block. The coordinates in FIG. 5 are measured in MxN blocks. "M × N" and "M times N" are used interchangeably to refer to the pixel size of an image block according to the horizontal and vertical dimensions, that is, there are M pixels in the horizontal direction and N pixels in the vertical direction. Where M and N represent non-negative integer values. In addition, the block does not necessarily need to have the same number of pixels in the horizontal direction as in the vertical direction. For example, M = N = 4 here, of course, the subblock size and reference block size of the current image block can also be 8x8 pixels, 8x4 pixels, or 4x8 pixels, or the smallest predicted block size. In addition, the image block described in this application can be understood as, but not limited to, a prediction unit (PU), a coding unit (CU), or a transformation unit (TU). According to the provisions of different video compression codec standards, a CU may include one or more prediction units PU, or the PU and the CU have the same size. Image blocks can have fixed or variable sizes and differ in size according to different video compression codec standards. In addition, the current image block refers to an image block to be encoded or decoded currently, such as a prediction unit to be encoded or decoded.

In one example, it is possible to sequentially determine whether each of the left spatial-domain neighboring blocks of the current image block 600 is available along the direction 1 and to sequentially determine each upper-space neighboring block of the current image block 600 along the direction 2. Whether it is available, for example, judging whether neighboring blocks (also referred to as reference blocks, which are used interchangeably) are inter-coded. If the neighboring block exists and is inter-coded, the neighboring block is available; if the neighboring block does not exist or is intra Encoding, then the neighboring blocks are unavailable. If one neighboring block is intra-coded, the motion information of other neighboring reference blocks is copied as the motion information of the neighboring block. Whether the lower airspace neighboring block and the right airspace neighboring block of the juxtaposed block 600 'are available in a similar manner is not described here.

Further, if the size of the available reference block and the size of the subblock of the current image block are 4x4, the motion information of the fetch available reference block can be directly obtained; if the size of the available reference block is, for example, 8x4, 8x8, its center 4x4 block can be obtained The motion information of the available reference block is used as the motion information of the available reference block. The coordinates of the top left vertex of the center 4x4 block relative to the top left vertex of the reference block are ((W / 4) / 2 * 4, (H / 4) / 2 * 4). Here, the division operation is an integer division operation. If M = 8 and N = 4, the coordinates of the upper left corner vertex of the center 4x4 block relative to the upper left corner vertex of the reference block are (4,0). Optionally, the motion information of the 4x4 block in the upper left corner of the reference block may also be acquired as the motion information of the available reference block, but the application is not limited thereto.

In order to simplify the description, the following describes the MxN sub-blocks as sub-blocks and the neighboring MxN-blocks as neighboring blocks.

FIG. 6 is a flowchart illustrating a process 700 of an encoding method according to an embodiment of the present application. The process 700 may be performed by the video encoder 100. Specifically, the process 700 may be performed by the inter prediction unit 110 and the entropy coding unit (also referred to as an entropy encoder) 103 of the video encoder 100. The process 700 is described as a series of steps or operations. It should be understood that the process 700 may be performed in various orders and / or concurrently, and is not limited to the execution order shown in FIG. 6. Assume that a video data stream with multiple video frames is using a video encoder. If the first neighboring affine coding block is located above the current coding block (Coding Tree Unit, CTU), then the first neighboring affine coding block is used. The lower left control point and lower right control point of the radio coding block determine a set of candidate motion vector prediction values, corresponding to the process shown in FIG. 6, and the related description is as follows:

Step S700: The video encoder determines an inter prediction mode of a current coding block.

Specifically, the inter prediction mode may be an advanced motion vector prediction (Advanced Vector Prediction (AMVP) mode) or may be a merge mode.

If it is determined that the inter prediction mode of the current coding block is the AMVP mode, steps S711-S713 are performed.

If it is determined that the inter prediction mode of the current coding block is a merge mode, steps S721-S723 are performed.

AMVP mode:

Step S711: The video encoder constructs a candidate motion vector prediction value MVP list.

Specifically, the video encoder uses an inter prediction unit (also referred to as an inter prediction module) to construct a candidate motion vector prediction value MVP list (also referred to as a candidate motion vector list). One of the two methods provided below may be adopted. To build, or use a combination of the two methods, the candidate motion vector prediction value MVP list can be a triplet candidate motion vector prediction value MVP list or a binary tuple candidate motion vector prediction value MVP List; the above two methods are as follows:

Method 1: A motion vector prediction method based on a motion model is used to construct a candidate motion vector prediction value MVP list.

First, all or part of neighboring blocks of the current coding block are traversed in a predetermined order to determine the neighboring affine coding blocks, and the number of the determined neighboring affine coding blocks may be one or more. For example, the neighboring blocks A, B, C, D, and E shown in FIG. 7A may be traversed in order to determine neighboring affine coding blocks in the neighboring blocks A, B, C, D, and E. The inter prediction unit determines at least one set of candidate motion vector prediction values (each set of candidate motion vector prediction values is a two-tuple or three-tuple) according to at least one adjacent affine coding block, and an adjacent affine is used below The coding block is introduced as an example. For convenience of description, the neighboring affine coding block is called the first neighboring affine coding block, as follows:

A first affine model is determined according to a motion vector of a control point of a first neighboring affine coding block, and then a motion vector of a control point of the current coding block is predicted according to the first affine model. When the parameter model of the current coding block is different, the method of predicting the motion vector of the control point of the current coding block based on the motion vector of the control point of the first neighboring affine coding block is also different, so the following description will be made on a case-by-case basis.

A. The parameter model of the current coding block is a 4-parameter affine transformation model. The derivation method can be:

If the first neighboring affine coding block is located in a Coding Tree Unit (CTU) above the current coding block and the first neighboring affine coding block is a four-parameter affine coding block, the first phase is obtained The motion vectors of the bottom two control points of the adjacent affine coding block. For example, the position coordinates (x ₆ , y ₆ ) and motion vectors (vx ₆ , vy) of the lower left control point of the first adjacent affine coding block can be obtained. ₆ ), and the position coordinates (x ₇ , y ₇ ) and motion vector values (vx ₇ , vy ₇ ) of the lower right control point.

A first affine model is formed according to the motion vectors and coordinate positions of the bottom two control points of the first adjacent affine coding block (the first affine model obtained at this time is a 4-parameter affine model).

The motion vector of the control point of the current coding block is predicted according to the first affine model. For example, the position coordinates of the upper left control point and the position of the upper right control point of the current coding block may be brought into the first affine model, respectively. , Thereby predicting the motion vector of the upper left control point and the motion vector of the upper right control point of the current coding block, as shown in formulas (1) and (2).

In formulas (1) and (2), (x ₀ , y ₀ ) are the coordinates of the upper-left control point of the current coding block, and (x ₁ , y ₁ ) are the coordinates of the upper-right control point of the current coding block; in addition, ( vx ₀ , vy ₀ ) is a motion vector of the upper left control point of the predicted current coding block, and (vx ₁ , vy ₁ ) is a motion vector of the upper right control point of the predicted current coding block.

Optionally, the position coordinates (x ₆ , y ₆ ) of the lower left control point of the first adjacent affine coding block and the position coordinates (x ₇ , y ₇ ) of the lower right control point are both based on the The position coordinates (x ₄ , y ₄ ) of the upper left control point of the first adjacent affine coding block are calculated, where the position coordinates (x ₆ , y) of the lower left control point of the first adjacent affine coding block ₆ ) is (x ₄ , y ₄ + cuH), and the position coordinates (x ₇ , y ₇ ) of the lower right control point of the first adjacent affine coding block is (x ₄ + cuW, y ₄ + cuH) , CuW is the width of the first neighboring affine coding block, and cuH is the height of the first neighboring affine coding block. In addition, the motion vector of the lower left control point of the first neighboring affine coding block is A motion vector of a lower left sub-block of the first adjacent affine coding block, and a motion vector of a lower right control point of the first adjacent affine coding block is a Motion vector. It can be seen that the position coordinates of the lower left control point and the position coordinates of the lower right control point of the first adjacent affine coding block are both derived and not read from memory, so using this method can Further reducing memory reads and improving encoding performance. As another alternative, the position coordinates of the lower left control point and the lower right control point may also be pre-selected and stored in the memory, and read from the memory when needed later.

If the first neighboring affine coding block is located in a coding tree unit (CTU) above the current coding block and the first neighboring affine coding block is a six-parameter affine coding block, it is not based on the first phase The neighboring affine coding block generates a candidate motion vector prediction value of a control point of the current block.

If the first neighboring affine coding block is not located above the CTU of the current coding block, the manner of predicting the motion vector of the control point of the current coding block is not limited here. However, for ease of understanding, an optional determination method is also exemplified below:

The position coordinates and motion vectors of the three control points of the first adjacent affine coding block may be obtained, for example, the position coordinates (x ₄ , y ₄ ) and motion vector values (vx ₄ , vy ₄ ) of the upper left control point, an upper right position coordinates of the control points (x _{_5,} y ₅₎ and a motion vector value (vx _{_5,} vy _5), the position coordinates of the lower left control point (x _{_6,} y ₆₎ and the motion vector (vx _{_6,} vy _6).

A 6-parameter affine model is formed according to the position coordinates and motion vectors of the three control points of the first adjacent affine coding block.

The position coordinates (x ₀ , y ₀ ) of the upper left control point and the position coordinates (x ₁ , y ₁ ) of the upper right control point of the current coding block are substituted into a 6-parameter affine model to predict the motion vector of the upper left control point of the current coding block. And the motion vector of the upper right control point, as shown in formulas (4) and (5).

In formulas (4) and (5), (vx ₀ , vy ₀ ) is the motion vector of the upper left control point of the predicted current coding block, and (vx ₁ , vy ₁ ) is the predicted upper right control point of the current coding block. Motion vector.

B. The parameter model of the current coding block is a 6-parameter affine transformation model. The derivation method can be:

If the first neighboring affine coding block is located above the CTU of the current coding block and the first neighboring affine coding block is a four-parameter affine coding block, two lowermost two sides of the first neighboring affine coding block are obtained Position coordinates and motion vectors of control points. For example, the position coordinates (x ₆ , y ₆ ) and motion vectors (vx ₆ , vy ₆ ) of the lower left control point of the first adjacent affine coding block can be obtained, and the lower right control The position coordinates (x ₇ , y ₇ ) and motion vector values (vx ₇ , vy ₇ ) of the point.

A first affine model is formed according to the motion vectors of the two control points at the bottom of the first adjacent affine coding block (the first affine model obtained at this time is a 4-parameter affine model).

The motion vector of the control point of the current coding block is predicted according to the first affine model. For example, the position coordinates of the upper left control point, the position of the upper right control point, and the position of the lower left control point of the current coding block may be brought in respectively. To the first affine model to predict the motion vector of the upper left control point, the upper right control point, and the lower left control point of the current coding block, as shown in formulas (1), (2), and (3). Show.

Formulas (1) and (2) have been described above. In formulas (1), (2), and (3), (x ₀ , y ₀ ) are the coordinates of the upper-left control point of the current coding block, (x ₁ , y ₁ ) is the coordinate of the upper right control point of the current coding block, (x ₂ , y ₂ ) is the coordinate of the lower left control point of the current coding block; in addition, (vx ₀ , vy ₀ ) is the predicted upper left control of the current coding block The motion vector of the point, (vx ₁ , vy ₁ ) is the motion vector of the predicted upper right control point of the current coding block, and (vx ₂ , vy ₂ ) is the motion vector of the predicted right and left lower control point of the current coding block.

The position coordinates (x ₀ , y ₀ ) of the upper left control point, the position coordinates of the upper right control point (x ₁ , y ₁ ), and the position coordinates of the lower left control point (x ₂ , y ₂ ) of the current coding block are substituted into 6 parameters. The affine model predicts the motion vector of the upper left control point, the motion vector of the upper right control point, and the motion vector of the lower left control point of the current coding block, as shown in formulas (4), (5), and (6).

Formulas (4) and (5) have been described previously. In formulas (4), (5), and (6), (vx ₀ , vy ₀ ) is the predicted motion vector of the upper-left control point of the current coding block, ( vx ₁ , vy ₁ ) are the motion vectors of the predicted upper right control point of the current coding block, and (vx ₂ , vy ₂ ) are the motion vectors of the predicted lower left control point of the current coding block.

Method 2: A motion vector prediction method based on the combination of control points is used to construct a candidate motion vector prediction value MVP list.

The parameter model of the current coding block does not have the same way of constructing the candidate motion vector prediction value MVP list at the same time, which will be described below.

The motion information of the upper left vertex and the upper right vertex of the current coding block is estimated by using the motion information of the coded blocks adjacent to the current coding block. As shown in FIG. 7B: First, the motion vector of the upper left vertex adjacent to the coded block A and / or B and / or C block is used as a candidate motion vector of the motion vector of the upper left vertex of the current coding block; The motion vector of the coding block D and / or E block is used as a candidate motion vector of the motion vector of the top right vertex of the current coding block. A candidate motion vector of the upper left vertex and a candidate motion vector of the upper right vertex are combined to obtain a set of candidate motion vector prediction values. Multiple records obtained by combining in this combination manner can form a candidate motion vector prediction value MVP list.

B. The current parameter block parameter model is a 6-parameter affine transformation model. The derivation method can be:

The motion information of the upper left vertex and the upper right vertex of the current coding block is estimated by using the motion information of the coded blocks adjacent to the current coding block. As shown in FIG. 7B: First, the motion vector of the upper left vertex adjacent to the coded block A and / or B and / or C block is used as a candidate motion vector of the motion vector of the upper left vertex of the current coding block; The motion vector of the coding block D and / or E block is used as the candidate motion vector of the motion vector of the top right vertex of the current coding block; the motion vector of the coded block F and / or G block adjacent to the top right vertex is used as the top right vertex of the current coding block Candidate motion vector. A combination of the candidate motion vector of the upper left vertex, the candidate motion vector of the upper right vertex, and the candidate motion vector of the lower left vertex can be used to obtain a set of candidate motion vector prediction values. A plurality of sets of candidate motion vectors obtained by combining in this way The prediction value may constitute a candidate motion vector prediction value MVP list.

It should be noted that the candidate motion vector prediction value MVP list can only be constructed by using the candidate motion vector prediction value predicted by the first method, or the candidate motion vector prediction value MVP can be constructed by only using the candidate motion vector prediction value obtained by the second method prediction. For the list, the candidate motion vector prediction value obtained by the prediction method 1 and the candidate motion vector prediction value obtained by the method 2 prediction can be used to jointly construct a candidate motion vector prediction value MVP list. In addition, the candidate motion vector prediction value MVP list can be pruned and sorted according to a pre-configured rule, and then truncated or filled to a specific number. When each group of candidate motion vector prediction values in the candidate motion vector prediction value MVP list includes motion vector prediction values of three control points, the candidate motion vector prediction value MVP list may be called a triple list; when the candidate motion vector When each group of candidate motion vector prediction values in the prediction value MVP list includes motion vector prediction values of two control points, the candidate motion vector prediction value MVP list may be referred to as a two-tuple list.

Step S712: The video encoder determines the target candidate motion vector group from the candidate motion vector prediction value MVP list according to the rate-distortion cost criterion. Specifically, for each candidate motion vector group in the candidate motion vector prediction value MVP list, the motion vector of each sub-block of the current block is calculated, and motion compensation is performed to obtain the prediction value of each sub-block, thereby obtaining the prediction value of the current block. The candidate motion vector group with the smallest error between the predicted value and the original value is selected as a set of the best motion vector prediction values, that is, the target candidate motion vector group. In addition, the determined target candidate motion vector group is used as an optimal candidate motion vector prediction value for a set of control points, and the target candidate motion vector group corresponds to a unique index number in the candidate motion vector prediction value MVP list.

Step S713: The video encoder encodes an index corresponding to the target candidate motion vector and a motion vector difference MVD into a code stream to be transmitted.

Specifically, the video encoder may also use the target candidate motion vector group as a search starting point to search for a set of motion vectors with the lowest cost control point within a preset search range according to a rate distortion cost criterion; and then determine the group The motion vector difference MVD between the motion vector of the control point and the target candidate motion vector group, for example, if the first group of control points includes the first control point and the second control point, then the motion of the first control point needs to be determined A motion vector difference MVD of a motion vector prediction value of a first control point in a set of control points represented by the vector and the target candidate motion vector group, and a motion vector determining a second control point and the target candidate motion vector group A motion vector difference MVD of a motion vector prediction value of a second control point in a set of control points represented.

Optionally, in the AMVP mode, in addition to steps S711-S713 described above, steps S714-S715 may also be performed.

Step S714: The video encoder uses the affine transformation model to obtain the motion vector value of each sub-block in the current coding block according to the motion vector value of the control point of the current coding block determined above.

Specifically, the new candidate motion vector group obtained based on the target candidate motion vector group and the MVD includes two (upper left control points and upper right control points) or three control points (for example, upper left control point, upper right control point, and lower left control). Dot) motion vector. For each sub-block of the current coding block (a sub-block can also be equivalent to a motion compensation unit), the motion information of pixels at preset positions in the motion compensation unit can be used to represent the motion of all pixels in the motion compensation unit information. Assume that the size of the motion compensation unit is MxN (M is less than or equal to the width W of the current coding block, and N is less than or equal to the height H of the current coding block, where M, N, W, H are positive integers, usually powers of two, such as 4, 8, 16, 32, 64, 128, etc.), the preset position pixels can be the center point of the motion compensation unit (M / 2, N / 2), the upper left pixel (0, 0), and the upper right pixel ( M-1,0), or other locations. FIG. 8A illustrates a 4 × 4 motion compensation unit, and FIG. 8B illustrates an 8 × 8 motion compensation unit.

The coordinates of the center point of the motion compensation unit relative to the top left pixel of the current coding block are calculated using formula (5), where i is the ith motion compensation unit in the horizontal direction (from left to right), and j is the jth motion in the vertical direction The compensation unit (from top to bottom), (x _{(i, j)} , y _{(i, j)} ) represents the coordinates of the center point of the (i, j) th motion compensation unit relative to the upper left control point pixel of the current coding block. Then according to the affine model type (6 or 4 parameters) of the current coding block, substitute (x _{(i, j)} , y _{(i, j)} ) into the 6-parameter affine model formula (6-1) or (x _{(i, j)} , y _{(i, j)} ) is substituted into the 4-parameter affine model formula (6-2) to obtain the motion information of the center point of each motion compensation unit as the motion vector of all pixels in the motion compensation unit (vx _{(i, j)} , vy _{(i, j)} ).

Optionally, when the current coding block is a 6-parameter coding block, when the motion vectors of one or more sub-blocks of the current coding block are obtained based on the target candidate motion vector group, if the lower boundary of the current coding block and The lower boundary of the CTU where the current coding block is located coincides, and the motion vector of the sub-block in the lower left corner of the current coding block is a 6-parameter affine model constructed according to the three control points and the current coding block's The position coordinates (0, H) of the lower left corner are calculated, and the motion vector of the lower right corner sub-block of the current coding block is a 6-parameter affine model constructed according to the three control points and the right of the current coding block. The position coordinates (W, H) of the lower corner are calculated. For example, by substituting the position coordinates (0, H) of the lower left corner of the current coding block into the 6-parameter affine model, the motion vector of the sub block at the lower left corner of the current coding block (instead of the The center point coordinate is substituted into the affine model for calculation.) The position coordinates (W, H) of the lower right corner of the current coding block are substituted into the 6-parameter affine model to obtain the motion vector of the subblock in the lower right corner of the current coding block. (Instead of substituting the coordinates of the center point of the subblock in the lower right corner into the affine model for calculation). In this way, the motion vector of the lower left control point and the lower right control point of the current coding block are used (for example, subsequent other blocks are constructed based on the motion vector of the lower left control point and the lower right control point of the current block). The candidate motion vector prediction value MVP list of the other blocks) uses an accurate value instead of an estimated value. Wherein, W is the width of the current coding block, and H is the height of the current coding block.

Optionally, when the current coding block is a 4-parameter coding block, when a motion vector of one or more sub-blocks of the current coding block is obtained based on the target candidate motion vector group, if the lower boundary of the current coding block and The lower boundary of the CTU where the current coding block is located coincides, and the motion vector of the lower left sub-block of the current coding block is a 4-parameter affine model constructed according to the two control points and the The position coordinates (0, H) of the lower left corner are calculated, and the motion vector of the subblock in the lower right corner of the current coding block is a 4-parameter affine model constructed according to the two control points and the right of the current coding block. The position coordinates (W, H) of the lower corner are calculated. For example, by substituting the position coordinates (0, H) of the lower left corner of the current coding block into the 4-parameter affine model, the motion vector of the sub block at the lower left corner of the current coding block (instead of the The center point coordinate is substituted into the affine model for calculation), and the position coordinates (W, H) of the lower right corner of the current coding block are substituted into the four-parameter affine model to obtain the motion vector of the subblock in the lower right corner of the current coding block. (Instead of substituting the coordinates of the center point of the subblock in the lower right corner into the affine model for calculation). In this way, the motion vector of the lower left control point and the lower right control point of the current coding block are used (for example, subsequent other blocks are constructed based on the motion vector of the lower left control point and the lower right control point of the current block). The candidate motion vector prediction value MVP list of the other blocks) uses an accurate value instead of an estimated value. Wherein, W is the width of the current coding block, and H is the height of the current coding block.

Step S715: The video encoder performs motion compensation according to the motion vector value of each sub-block in the current coding block to obtain the pixel prediction value of each sub-block. For example, the motion vector and reference frame index value of each sub-block are used in The corresponding sub-block is found in the reference frame, and interpolation filtering is performed to obtain the pixel prediction value of each sub-block.

Merge mode:

Step S721: The video encoder constructs a candidate motion information list.

Specifically, the video encoder constructs a candidate motion information list (also referred to as a candidate motion vector list) through an inter prediction unit (also referred to as an inter prediction module), which may be constructed in one of two ways provided below. Or it can be constructed by a combination of two methods, and the candidate motion information list constructed is a triplet candidate motion information list; the above two methods are specifically as follows:

Method 1: A motion vector prediction method based on a motion model is used to construct a candidate motion information list.

First, all or part of neighboring blocks of the current coding block are traversed in a predetermined order to determine the neighboring affine coding blocks, and the number of the determined neighboring affine coding blocks may be one or more. For example, the neighboring blocks A, B, C, D, and E shown in FIG. 7A may be traversed in order to determine neighboring affine coding blocks in the neighboring blocks A, B, C, D, and E. The inter prediction unit determines a set of candidate motion vector prediction values (each set of candidate motion vector prediction values is a two-tuple or three-tuple) according to each adjacent affine coding block, and an adjacent affine is used below The coding block is introduced as an example. For convenience of description, the neighboring affine coding block is called the first neighboring affine coding block, as follows:

The first affine model is determined according to the motion vector of the control points of the first neighboring affine coding block, and then the motion vector of the control point of the current coding block is predicted according to the first affine model, which is specifically described as follows:

If the first adjacent affine coding block is located above the CTU of the current coding block and the first adjacent affine coding block is a four-parameter affine coding block, two lower-most two sides of the first adjacent affine coding block are obtained. Position coordinates and motion vectors of the control points, for example, the position coordinates (x ₆ , y ₆ ) and motion vectors (vx ₆ , vy ₆ ) of the lower left control point of the first adjacent affine coding block can be obtained, and the lower right The position coordinates (x ₇ , y ₇ ) and motion vector values (vx ₇ , vy ₇ ) of the control point.

Optionally, the motion vector of the control point of the current coding block is predicted according to the first affine model. For example, the position coordinates of the upper left control point, the position coordinates of the upper right control point, and the position of the lower left control point of the current coding block may be predicted. The coordinates are brought into the first affine model, so as to predict the motion vector of the upper left control point, the upper right control point, and the lower left control point of the current coding block to form a candidate motion vector triplet and add candidate motions. The information list is shown in formulas (1), (2), and (3).

Optionally, the motion vector of the control point of the current coding block is predicted according to the first affine model. For example, the position coordinates of the upper left control point and the position coordinates of the upper right control point of the current coding block may be brought into the first An affine model to predict the motion vector of the upper left control point and the motion vector of the upper right control point of the current coding block to form a candidate motion vector tuple, and add the candidate motion information list, as shown in formulas (1) and (2). Show.

In formulas (1), (2), and (3), (x ₀ , y ₀ ) are the coordinates of the upper-left control point of the current coding block, and (x ₁ , y ₁ ) are the coordinates of the upper-right control point of the current coding block. , (X ₂ , y ₂ ) are the coordinates of the lower left control point of the current coding block; in addition, (vx ₀ , vy ₀ ) is the predicted motion vector of the upper left control point of the current coding block, and (vx ₁ , vy ₁ ) is The predicted motion vector of the upper right control point of the current coding block, (vx ₂ , vy ₂ ) is the predicted motion vector of the lower left control point of the current coding block.

If the first neighboring affine coding block is located in a coding tree unit (CTU) above the current coding block and the first neighboring affine coding block is a six-parameter affine coding block, it is not based on the first The neighboring affine coding block generates a candidate motion vector prediction value of a control point of the current block.

Manner 2: A motion vector prediction method based on a combination of control points is used to construct a candidate motion information list.

The following two examples are exemplified as Option A and Option B:

Solution A: Combine the motion information of the control points of the two current coding blocks to build a 4-parameter affine transformation model. The combination of the two control points is {CP1, CP4}, {CP2, CP3}, {CP1, CP2}, {CP2, CP4}, {CP1, CP3}, {CP3, CP4}. For example, a 4-parameter affine transformation model constructed using CP1 and CP2 control points is denoted as Affine (CP1, CP2).

It should be noted that a combination of different control points can also be converted into a control point at the same position. For example: the four-parameter affine transformation model obtained by combining {CP1, CP4}, {CP2, CP3}, {CP2, CP4}, {CP1, CP3}, {CP3, CP4} into a control point {CP1, CP2} Or {CP1, CP2, CP3}. The conversion method is to substitute the motion vector of the control point and its coordinate information into formula (9-1) to obtain the model parameters, and then substitute the coordinate information of {CP1, CP2} to obtain its motion vector, which is used as a set of candidate motion vector predictions. value.

In formula (9-1), a ₀ , a ₁ , a ₂ , and a ₃ are parameters in the parameter model, and (x, y) represents position coordinates.

More directly, a set of motion vector prediction values represented by the upper left control point and the upper right control point can also be converted according to the following formula, and added to the candidate motion information list:

{CP1, CP2} is transformed to {CP1, CP2, CP3} 's formula (9-2):

{CP1, CP3} is converted to {CP1, CP2, CP3} 's formula (9-3):

{CP2, CP3} is converted to {CP1, CP2, CP3} 's formula (10):

{CP1, CP4} is converted to {CP1, CP2, CP3} 's formula (11):

{CP2, CP4} is converted to {CP1, CP2, CP3} 's formula (12):

{CP3, CP4} is converted to {CP1, CP2, CP3} 's formula (13):

Solution B: Combine the motion information of the 3 control points of the current coding block to build a 6-parameter affine transformation model. The combination of the three control points is {CP1, CP2, CP4}, {CP1, CP2, CP3}, {CP2, CP3, CP4}, {CP1, CP3, CP4}. For example, a 6-parameter affine transformation model constructed using CP1, CP2, and CP3 control points is denoted as Affine (CP1, CP2, CP3).

It should be noted that a combination of different control points can also be converted into a control point at the same position. For example: The 6-parameter affine transformation model of {CP1, CP2, CP4}, {CP2, CP3, CP4}, {CP1, CP3, CP4} is converted into a control point {CP1, CP2, CP3} to represent it. The transformation method is to substitute the motion vector of the control point and its coordinate information into formula (14) to obtain the model parameters, and then substitute the coordinate information of {CP1, CP2, CP3} to obtain its motion vector, which is used as a set of candidate motion vector predictions. value.

In formula (14), a ₁ , a ₂ , a ₃ , a ₄ , a ₅ , and a ₆ are parameters in the parameter model, and (x, y) represents position coordinates.

More directly, a set of motion vector prediction values represented by the upper left control point, upper right control point, and lower left control point can also be converted according to the following formula, and added to the candidate motion information list:

{CP1, CP2, CP4} is transformed into {CP1, CP2, CP3} 's formula (15):

{CP2, CP3, CP4} is converted to {CP1, CP2, CP3} 's formula (16):

{CP1, CP3, CP4} is converted to {CP1, CP2, CP3} 's formula (17):

It should be noted that the candidate motion information list may be constructed only by using the candidate motion vector prediction values predicted by the first method, or only the candidate motion vector prediction values obtained by the second prediction method may be used to construct the candidate motion information list. A candidate motion vector prediction value obtained by the first prediction and a candidate motion vector prediction value obtained by the second prediction are used to jointly construct a candidate motion information list. In addition, the candidate motion information list can be pruned and sorted according to pre-configured rules, and then truncated or filled to a specific number. When each group of candidate motion vector prediction values in the candidate motion information list includes motion vector prediction values of three control points, the candidate motion information list may be referred to as a triple list; when each group in the candidate motion information list When the candidate motion vector prediction value includes motion vector prediction values of two control points, the candidate motion information list may be referred to as a two-tuple list.

Step S722: The video encoder determines a target candidate motion vector group from the candidate motion information list according to the rate-distortion cost criterion. Specifically, for each candidate motion vector group in the candidate motion information list, the motion vector of each sub-block of the current block is calculated, and motion compensation is performed to obtain the prediction value of each sub-block, thereby obtaining the prediction value of the current block. The candidate motion vector group with the smallest error between the predicted value and the original value is selected as a set of the best motion vector prediction values, that is, the target candidate motion vector group. In addition, the determined target candidate motion vector group is used as an optimal candidate motion vector prediction value for a group of control points, and the target candidate motion vector group corresponds to a unique index number in the candidate motion information list.

Step S723: The video encoder encodes an index corresponding to the target candidate motion vector group, a reference frame index, and a prediction direction into a code stream to be transmitted.

Optionally, in the merge mode, in addition to steps S721-S723 described above, steps S724-S725 may also be performed.

Step S724: The video encoder uses the parameter affine transformation model to obtain the motion vector value of each sub-block in the current coding block according to the motion vector value of the control point of the current coding block determined above.

Specifically, it is a motion vector of two (upper left control points and upper right control points) or three control points (for example, upper left control points, upper right control points, and lower left control points) included in the target candidate motion vector group. For each sub-block of the current coding block (a sub-block can also be equivalent to a motion compensation unit), the motion information of pixels at preset positions in the motion compensation unit can be used to represent the motion of all pixels in the motion compensation unit information. Assume that the size of the motion compensation unit is MxN (M is less than or equal to the width W of the current coding block, and N is less than or equal to the height H of the current coding block, where M, N, W, H are positive integers, usually powers of two, such as 4, 8, 16, 32, 64, 128, etc.), the preset position pixels can be the center point of the motion compensation unit (M / 2, N / 2), the upper left pixel (0, 0), and the upper right pixel ( M-1,0), or other locations. FIG. 8A illustrates a 4 × 4 motion compensation unit, and FIG. 8B illustrates an 8 × 8 motion compensation unit.

The coordinates of the center point of the motion compensation unit relative to the top left pixel of the current coding block are calculated using formula (5), where i is the i-th motion compensation unit in the horizontal direction (from left to right), and j is the j-th motion in the vertical direction. The compensation unit (from top to bottom), (x _{(i, j)} , y _{(i, j)} ) represents the coordinates of the center point of the (i, j) th motion compensation unit relative to the upper left control point pixel of the current coding block. Then according to the affine model type (6 or 4 parameters) of the current coding block, substitute (x _{(i, j)} , y _{(i, j)} ) into the 6-parameter affine model formula (6-1) or (x _{(i, j)} , y _{(i, j)} ) is substituted into the 4-parameter affine model formula (6-2) to obtain the motion information of the center point of each motion compensation unit as the motion vector of all pixels in the motion compensation unit (vx _{(i, j)} , vy _{(i, j)} ).

Optionally, when the current coding block is a 6-parameter coding block, when the motion vectors of one or more sub-blocks of the current coding block are obtained based on the target candidate motion vector group, if the lower boundary of the current coding block and The lower boundary of the CTU where the current coding block is located coincides, and the motion vector of the sub-block in the lower left corner of the current coding block is a 6-parameter affine model constructed according to the three control points and the current coding block's The position coordinates (0, H) of the lower left corner are calculated, and the motion vector of the lower right corner sub-block of the current coding block is a 6-parameter affine model constructed according to the three control points and the right of the current coding block. The position coordinates (W, H) of the lower corner are calculated. For example, by substituting the position coordinates (0, H) of the lower left corner of the current coding block into the 6-parameter affine model, the motion vector of the sub block at the lower left corner of the current coding block (instead of the The center point coordinate is substituted into the affine model for calculation.) The position coordinates (W, H) of the lower right corner of the current coding block are substituted into the 6-parameter affine model to obtain the motion vector of the subblock in the lower right corner of the current coding block. (Instead of substituting the coordinates of the center point of the subblock in the lower right corner into the affine model for calculation). In this way, the motion vector of the lower left control point and the lower right control point of the current coding block are used (for example, subsequent other blocks are constructed based on the motion vector of the lower left control point and the lower right control point of the current block). The candidate motion information list of the other blocks) uses accurate values instead of estimated values. Wherein, W is the width of the current coding block, and H is the height of the current coding block.

Optionally, when the current coding block is a 4-parameter coding block, when a motion vector of one or more sub-blocks of the current coding block is obtained based on the target candidate motion vector group, if the lower boundary of the current coding block and The lower boundary of the CTU where the current coding block is located coincides, and the motion vector of the lower left sub-block of the current coding block is a 4-parameter affine model constructed according to the two control points and the The position coordinates (0, H) of the lower left corner are calculated, and the motion vector of the subblock in the lower right corner of the current coding block is a 4-parameter affine model constructed according to the two control points and the right of the current coding block. The position coordinates (W, H) of the lower corner are calculated. For example, by substituting the position coordinates (0, H) of the lower left corner of the current coding block into the 4-parameter affine model, the motion vector of the sub block at the lower left corner of the current coding block (instead of the The center point coordinate is substituted into the affine model for calculation), and the position coordinates (W, H) of the lower right corner of the current coding block are substituted into the four-parameter affine model to obtain the motion vector of the subblock in the lower right corner of the current coding block. (Instead of substituting the coordinates of the center point of the subblock in the lower right corner into the affine model for calculation). In this way, the motion vector of the lower left control point and the lower right control point of the current coding block are used (for example, subsequent other blocks are constructed based on the motion vector of the lower left control point and the lower right control point of the current block). The candidate motion information list of the other blocks) uses accurate values instead of estimated values. Wherein, W is the width of the current coding block, and H is the height of the current coding block.

Step S725: The video encoder performs motion compensation according to the motion vector value of each sub-block in the current coding block to obtain the pixel prediction value of each sub-block. Specifically, according to one or more sub-blocks of the current coding block The motion vector, and the reference frame index and prediction direction indicated by the index, to obtain a pixel prediction value of the current coding block.

It can be understood that when the CTU of the coding tree unit where the first neighboring affine coding block is located is above the current coding block position, the information of the lowest control point of the first neighboring affine coding block has been changed from Read in memory; therefore, in the above solution, in the process of constructing a candidate motion vector according to the first set of control points of the first neighboring affine coding block, the first set of control points includes the first neighboring affine coding block Lower left control point and lower right control point; instead of fixing the upper left control point, upper right control point, and lower left control point of the first adjacent coding block as the first group of control points as in the prior art. Therefore, by adopting the method for determining the first set of control points in this application, the information of the first set of control points (for example, position coordinates, motion vectors, etc.) can directly reuse the information read from the memory, thereby reducing the memory read. This improves encoding performance.

FIG. 9 is a flowchart illustrating a process 900 of a decoding method according to an embodiment of the present application. The process 900 may be performed by the video decoder 100, and specifically, may be performed by the inter prediction unit 210 of the video decoder 200 and the entropy decoding unit (also referred to as an entropy decoder) 203. The process 900 is described as a series of steps or operations. It should be understood that the process 900 may be performed in various orders and / or concurrently, and is not limited to the execution order shown in FIG. 9. Assume that a video data stream with multiple video frames is using a video decoder. If the first neighboring affine decoding block is located above the current decoding block (Coding, Tree Unit, CTU), then it is based on the first neighboring affine decoding unit. The lower left control point and lower right control point of the radio decoding block determine a set of candidate motion vector prediction values, corresponding to the process shown in FIG. 9 and the related description is as follows:

If the first neighboring affine decoding block is located above the coding tree unit (CTU) of the current decoding block, a set of candidate motions is determined based on the lower left control point and the lower right control point of the first neighboring affine decoding block. The vector prediction value is described in detail as follows:

Step S1200: The video decoder determines an inter prediction mode of the currently decoded block.

If it is determined that the inter prediction mode of the current decoding block is the AMVP mode, steps S1211-S1216 are performed.

If it is determined that the inter prediction mode of the current decoding block is the merge mode, steps S1221-S1225 are performed.

AMVP mode:

Step S1211: The video decoder constructs a candidate motion vector prediction value MVP list.

Specifically, the video decoder uses an inter prediction unit (also referred to as an inter prediction module) to construct a candidate motion vector prediction value MVP list (also referred to as a candidate motion vector list). One of the two methods provided below may be adopted. To build, or use a combination of the two methods, the candidate motion vector prediction value MVP list can be a triplet candidate motion vector prediction value MVP list or a binary tuple candidate motion vector prediction value MVP List; the above two methods are as follows:

First, all or part of neighboring blocks of the current decoding block are traversed in a predetermined order to determine the neighboring affine decoding blocks, and the number of the determined neighboring affine decoding blocks may be one or more. For example, the neighboring blocks A, B, C, D, and E shown in FIG. 7A may be traversed in order to determine neighboring affine decoding blocks among the neighboring blocks A, B, C, D, and E. The inter prediction unit determines at least one set of candidate motion vector prediction values (each set of candidate motion vector prediction values is a two-tuple or three-tuple) according to at least one neighboring affine decoding block, and an adjacent affine is used below The decoding block is introduced as an example. For convenience of description, the adjacent affine decoding block is called the first adjacent affine decoding block, as follows:

A first affine model is determined according to a motion vector of a control point of a first adjacent affine decoding block, and a motion vector of a control point of the current decoding block is predicted according to the first affine model. When the parameter model of the current decoding block is different, the method of predicting the motion vector of the control point of the current decoding block based on the motion vector of the control point of the first adjacent affine decoding block is also different, so the following description will be made on a case-by-case basis.

A. The parameter model of the current decoding block is a 4-parameter affine transformation model, and the derivation method can be (see Figure 9A):

If the first neighboring affine decoding block is located in a Coding Tree Unit (CTU) above the current decoding block and the first neighboring affine decoding block is a four-parameter affine decoding block, the first phase is obtained The motion vectors of the bottom two control points of the adjacent affine decoding block. For example, the position coordinates (x ₆ , y ₆ ) and motion vectors (vx ₆ , vy) of the lower left control point of the first adjacent affine decoding block can be obtained. _6), and a lower right position of the control point coordinates (x _{_7,} y ₇₎ and motion vector values (vx _{_7,} vy ₇₎ (step S1201).

A first affine model is formed according to the motion vectors and coordinate positions of the bottom two control points of the first adjacent affine decoding block (the first affine model obtained at this time is a 4-parameter affine model) (step S1202) .

The motion vector of the control point of the current decoding block is predicted according to the first affine model. For example, the position coordinates of the upper left control point and the position of the upper right control point of the current decoding block may be brought into the first affine model, respectively. , Thereby predicting the motion vector of the upper left control point and the motion vector of the upper right control point of the current decoding block, as shown in formulas (1) and (2) (step S1203).

In formulas (1) and (2), (x ₀ , y ₀ ) are the coordinates of the upper left control point of the current decoded block, and (x ₁ , y ₁ ) are the coordinates of the upper right control point of the current decoded block; in addition, ( vx ₀ , vy ₀ ) is a motion vector of the upper left control point of the predicted current decoded block, and (vx ₁ , vy ₁ ) is a motion vector of the upper right control point of the predicted current decoded block.

Optionally, the position coordinates (x ₆ , y ₆ ) of the lower left control point of the first adjacent affine decoding block and the position coordinates (x ₇ , y ₇ ) of the lower right control point are both based on the The position coordinates (x ₄ , y ₄ ) of the upper left control point of the first adjacent affine decoding block are calculated, where the position coordinates (x ₆ , y) of the lower left control point of the first adjacent affine decoding block ₆ ) is (x ₄ , y ₄ + cuH), and the position coordinates (x ₇ , y ₇ ) of the lower right control point of the first adjacent affine decoding block is (x ₄ + cuW, y ₄ + cuH) , CuW is the width of the first neighboring affine decoding block, and cuH is the height of the first neighboring affine decoding block. In addition, the motion vector of the lower left control point of the first neighboring affine decoding block is A motion vector of a lower left sub-block of the first adjacent affine decoding block, and a motion vector of a lower right control point of the first adjacent affine decoding block is a Motion vector. It can be seen that the position coordinates of the lower left control point and the position coordinates of the lower right control point of the first adjacent affine decoding block are both derived and not read from the memory, so using this method can Further reducing memory reads and improving decoding performance. As another alternative, the position coordinates of the lower left control point and the lower right control point may also be pre-selected and stored in the memory, and read from the memory when needed later.

If the first neighboring affine decoding block is located in a Coding Tree Unit (CTU) above the current decoding block and the first neighboring affine decoding block is a six-parameter affine decoding block, it is not based on the first phase The neighboring affine decoding block generates a candidate motion vector prediction value of a control point of the current block.

If the first adjacent affine decoding block is not located above the CTU of the current decoding block, the manner of predicting the motion vector of the control point of the current decoding block is not limited here. However, for ease of understanding, an optional determination method is also exemplified below:

The position coordinates and motion vectors of the three control points of the first adjacent affine decoding block may be obtained, for example, the position coordinates (x ₄ , y ₄ ) and motion vector values (vx ₄ , vy ₄ ) of the upper left control point, an upper right position coordinates of the control points (x _{_5,} y ₅₎ and a motion vector value (vx _{_5,} vy _5), the position coordinates of the lower left control point (x _{_6,} y ₆₎ and the motion vector (vx _{_6,} vy _6).

A 6-parameter affine model is formed according to the position coordinates and motion vectors of the three control points of the first adjacent affine decoding block.

The position coordinates (x ₀ , y ₀ ) of the upper left control point and the position coordinates (x ₁ , y ₁ ) of the upper right control point of the current decoding block are substituted into a 6-parameter affine model to predict the motion vector of the upper left control point of the current decoding block. And the motion vector of the upper right control point, as shown in formulas (4) and (5).

In formulas (4) and (5), (vx ₀ , vy ₀ ) is the motion vector of the upper left control point of the predicted current decoded block, and (vx ₁ , vy ₁ ) is the predicted upper right control point of the current decoded block. Motion vector.

B. The parameter model of the current decoding block is a 6-parameter affine transformation model. The derivation method can be:

If the first adjacent affine decoding block is located above the CTU of the current decoding block and the first adjacent affine decoding block is a four-parameter affine decoding block, two lower-most two sides of the first adjacent affine decoding block are obtained. The position coordinates and motion vectors of the control points, for example, the position coordinates (x ₆ , y ₆ ) and motion vectors (vx ₆ , vy ₆ ) of the lower left control point of the first adjacent affine decoding block can be obtained, and the lower right control The position coordinates (x ₇ , y ₇ ) and motion vector values (vx ₇ , vy ₇ ) of the point.

A first affine model is formed according to the motion vectors of the two control points at the bottom of the first adjacent affine decoding block (the first affine model obtained at this time is a 4-parameter affine model).

The motion vector of the control point of the current decoded block is predicted according to the first affine model. For example, the position coordinates of the upper left control point, the position of the upper right control point, and the position of the lower left control point of the current decoded block may be brought in respectively. To the first affine model, thereby predicting the motion vector of the upper left control point, the motion vector of the upper right control point, and the motion of the lower left control point of the current decoding block, as shown in formulas (1), (2), (3) Show.

Formulas (1) and (2) have been described above. In formulas (1), (2), and (3), (x ₀ , y ₀ ) are the coordinates of the upper-left control point of the current decoding block, (x ₁ , y ₁ ) is the coordinate of the upper right control point of the current decoded block, (x ₂ , y ₂ ) is the coordinate of the lower left control point of the current decoded block; in addition, (vx ₀ , vy ₀ ) is the predicted upper left control of the current decoded block The motion vector of the point, (vx ₁ , vy ₁ ) is the motion vector of the predicted upper right control point of the current decoded block, and (vx ₂ , vy ₂ ) is the predicted motion vector of the right and left lower control point of the current decoded block.

Substituting the position coordinates (x ₀ , y ₀ ) of the upper left control point, the position coordinates of the upper right control point (x ₁ , y ₁ ), and the position coordinates of the lower left control point (x ₂ , y ₂ ) into the 6 parameters of the current decoding block. The affine model predicts the motion vector of the upper left control point, the motion vector of the upper right control point, and the motion vector of the lower left control point of the current decoding block, as shown in formulas (4), (5), and (6).

Formulas (4) and (5) have been described previously. In formulas (4), (5), and (6), (vx ₀ , vy ₀ ) is the predicted motion vector of the upper-left control point of the current decoding block, ( vx ₁ , vy ₁ ) are the motion vectors of the predicted upper right control point of the current decoded block, and (vx ₂ , vy ₂ ) are the predicted motion vectors of the lower left control point of the current decoded block.

The parameter model of the current decoding block does not have the same way of constructing the candidate motion vector prediction value MVP list at the same time, which will be described below.

A. The parameter model of the current decoding block is a 4-parameter affine transformation model. The derivation method can be:

The motion information of the upper left vertex and the upper right vertex of the current decoded block is estimated using the motion information of the decoded blocks adjacent to the current decoded block. As shown in FIG. 7B: First, the motion vector of the upper left vertex adjacent to the decoded block A and / or B and / or C block is used as the candidate motion vector of the motion vector of the upper left vertex of the current decoded block; The motion vector of the decoding block D and / or E block is used as a candidate motion vector of the motion vector of the upper right vertex of the current decoding block. A candidate motion vector of the upper left vertex and a candidate motion vector of the upper right vertex are combined to obtain a set of candidate motion vector prediction values. Multiple records obtained by combining in this combination manner can form a candidate motion vector prediction value MVP list.

B. The current decoding block parameter model is a 6-parameter affine transformation model. The derivation method can be:

The motion information of the upper left vertex and the upper right vertex of the current decoded block is estimated using the motion information of the decoded blocks adjacent to the current decoded block. As shown in FIG. 7B: First, the motion vector of the upper left vertex adjacent to the decoded block A and / or B and / or C block is used as the candidate motion vector of the motion vector of the upper left vertex of the current decoded block; The motion vector of the decoded block D and / or E block is used as the candidate motion vector of the motion vector of the top right vertex of the current decoded block; the motion vector of the decoded block F and / or G block adjacent to the top right vertex is used as the top right vertex of the current decoded block Candidate motion vector. A set of candidate motion vector prediction values can be obtained by combining the above candidate motion vector of the upper left vertex, the candidate motion vector of the upper right vertex, and the candidate motion vector of the lower left vertex. Multiple sets of candidate motion vectors obtained by combining in this combination manner The prediction value may constitute a candidate motion vector prediction value MVP list.

Step S1212: The video decoder parses the bitstream to obtain an index and a motion vector difference MVD.

Specifically, the video decoder may parse the bitstream through an entropy decoding unit, and the index is used to indicate a target candidate motion vector group of the current decoding block, where the target candidate motion vector represents a motion vector prediction value of a set of control points of the current decoding block.

Step S1213: The video decoder determines a target motion vector group from the candidate motion vector prediction value MVP list according to the index.

Specifically, the video decoder determines the target candidate motion vector group determined from the candidate motion vectors according to the index to be used as the optimal candidate motion vector prediction value (optionally, when the length of the candidate motion vector prediction value MVP list is 1) (You don't need to parse the bitstream to get the index, you can directly determine the target motion vector group.) The following briefly introduces the optimal and preferred motion vector prediction value.

If the parameter model of the current decoding block is a 4-parameter affine transformation model, then the optimal motion vector prediction value of 2 control points is selected from the candidate motion vector prediction value MVP list established above; for example, the video decoder from The index number is parsed in the bitstream, and the optimal motion vector prediction value of 2 control points is determined from the candidate motion vector prediction value MVP list of the binary group according to the index number. Each candidate motion vector prediction value in the MVP list of the candidate motion vector The vector prediction values correspond to their respective index numbers.

If the parameter model of the current decoding block is a 6-parameter affine transformation model, then the optimal motion vector prediction value of 3 control points is selected from the candidate motion vector prediction value MVP list established above; for example, the video decoder from The index number is parsed in the code stream, and the optimal motion vector prediction value of the three control points is determined from the triplet candidate motion vector prediction value MVP list according to the index number. The candidate motion vector prediction value MVP list includes each candidate motion The vector prediction values correspond to their respective index numbers.

Step S1214: The video decoder determines the motion vector of the control point of the current decoding block according to the target candidate motion vector group and the motion vector difference MVD parsed from the code stream.

If the parameter model of the current decoding block is a 4-parameter affine transformation model, then the motion vector difference values of the two control points of the current decoding block are obtained by decoding from the code stream, respectively according to the motion vector difference values of the control points and the index indication. To obtain a new candidate motion vector group. For example, the motion vector difference MVD of the upper left control point and the motion vector difference MVD of the upper right control point are decoded from the code stream, and are respectively added to the motion vectors of the upper left control point and the upper right control point in the target candidate motion vector group to thereby A new candidate motion vector group is obtained. Therefore, the new candidate motion vector group includes new motion vector values of the upper left control point and the upper right control point of the current decoding block.

Optionally, the motion vector value of the third control point may also be obtained by using a 4-parameter affine transformation model based on the motion vector values of the two control points of the current decoding block in the new candidate motion vector group. For example, the motion vector (vx ₀ , vy ₀ ) of the upper left control point and the motion vector (vx ₁ , vy ₁ ) of the upper right control point of the current decoding block are obtained, and then the lower left control point (x of the current decoding block) (x ₂ , y ₂ ) 's motion vector (vx ₂ , vy ₂ ).

Among them, (x ₀ , y ₀ ) is the position coordinates of the upper left control point, (x ₁ , y ₁ ) is the position coordinates of the upper right control point, W is the width of the current decoded block, and H is the height of the current decoded block.

If the current decoding block parameter model is a 6-parameter affine transformation model, then the motion vector difference values of the three control points of the current decoding block are obtained by decoding from the code stream, respectively according to the motion vector difference values of each control point and the MVD and the index indication. To obtain a new candidate motion vector group. For example, the motion vector difference MVD of the upper left control point, the motion vector difference MVD of the upper right control point, and the motion vector difference of the lower left control point are obtained from the code stream, and are respectively compared with the upper left control point in the target candidate motion vector group, The motion vectors of the upper right control point and the lower left control point are added to obtain a new candidate motion vector group. Therefore, the new candidate motion vector group includes the motion vector values of the upper left control point, the upper right control point, and the lower left control point of the current decoding block.

Step S1215: The video decoder uses the affine transformation model to obtain the motion vector value of each sub-block in the current decoding block according to the motion vector value of the control point of the current decoding block determined above.

Specifically, the new candidate motion vector group obtained based on the target candidate motion vector group and the MVD includes two (upper left control points and upper right control points) or three control points (for example, upper left control point, upper right control point, and lower left control). Dot) motion vector. For each sub-block of the current decoding block (a sub-block can also be equivalent to a motion compensation unit), the motion information of pixels at preset positions in the motion compensation unit can be used to represent the motion of all pixels in the motion compensation unit information. Assume that the size of the motion compensation unit is MxN (M is less than or equal to the width W of the current decoding block, and N is less than or equal to the height H of the current decoding block, where M, N, W, H are positive integers, usually powers of two, such as 4, 8, 16, 32, 64, 128, etc.), the preset position pixels can be the center point of the motion compensation unit (M / 2, N / 2), the upper left pixel (0, 0), and the upper right pixel ( M-1,0), or other locations. FIG. 8A illustrates a 4 × 4 motion compensation unit, and FIG. 8B illustrates an 8 × 8 motion compensation unit.

The coordinates of the center point of the motion compensation unit relative to the top left pixel of the current decoding block are calculated using formula (8-1), where i is the i-th motion compensation unit in the horizontal direction (from left to right), and j is the j-th vertical direction. Motion compensation units (from top to bottom), (x _{(i, j)} , y _{(i, j)} ) represents the coordinates of the (i, j) th center of the motion compensation unit relative to the pixel at the upper left control point of the current decoding block . Then according to the affine model type (6 or 4 parameters) of the current decoding block, substitute (x _{(i, j)} , y _{(i, j)} ) into the 6-parameter affine model formula (8-2) or (x _{(i, j)} , y _{(i, j)} ) is substituted into the 4-parameter affine model formula (8-3) to obtain the motion information of the center point of each motion compensation unit as the motion vector of all pixels in the motion compensation unit (vx _{(i, j)} , vy _{(i, j)} ).

Optionally, when the current decoding block is a 6-parameter decoding block, when a motion vector of one or more sub-blocks of the current decoding block is obtained based on the target candidate motion vector group, if the lower boundary of the current decoding block is The lower boundary of the CTU where the current decoding block is located coincides, and the motion vector of the sub-block in the lower left corner of the current decoding block is a 6-parameter affine model constructed from the three control points and the current decoding block. The position coordinates (0, H) of the lower left corner are calculated, and the motion vector of the subblock in the lower right corner of the current decoding block is a 6-parameter affine model constructed according to the three control points and the right of the current decoding block. The position coordinates (W, H) of the lower corner are calculated. For example, by substituting the position coordinates (0, H) of the lower left corner of the current decoded block into the 6-parameter affine model, the motion vector of the lower left corner sub-block of the current decoded block (instead of the The center point coordinate is substituted into the affine model for calculation), and the position coordinates (W, H) of the lower right corner of the current decoded block are substituted into the 6-parameter affine model to obtain the motion vector of the lower right corner of the current decoded block. (Instead of substituting the coordinates of the center point of the subblock in the lower right corner into the affine model for calculation). In this way, the motion vector of the lower left control point and the lower right control point of the current decoding block are used (for example, the subsequent other blocks are constructed based on the motion vector of the lower left control point and the lower right control point of the current block). The candidate motion vector prediction value MVP list of the other blocks) uses an accurate value instead of an estimated value. Wherein, W is the width of the current decoded block, and H is the height of the current decoded block.

Optionally, when the current decoding block is a 4-parameter decoding block, when the motion vectors of one or more sub-blocks of the current decoding block are obtained based on the target candidate motion vector group, if the lower boundary of the current decoding block and The lower boundary of the CTU where the current decoding block is located coincides, and the motion vector of the lower left sub-block of the current decoding block is a 4-parameter affine model constructed according to the two control points and the current decoding block's The position coordinates (0, H) of the lower left corner are calculated, and the motion vector of the sub-block in the lower right corner of the current decoding block is a 4-parameter affine model constructed according to the two control points and the right of the current decoding block. The position coordinates (W, H) of the lower corner are calculated. For example, by substituting the position coordinates (0, H) of the lower left corner of the current decoded block into the 4-parameter affine model, the motion vector of the lower left sub-block of the current decoded block (instead of the The center point coordinates are substituted into the affine model for calculation), and the position coordinates (W, H) of the lower right corner of the current decoding block are substituted into the four-parameter affine model to obtain the motion vector of the subblock in the lower right corner of the current decoding block. (Instead of substituting the coordinates of the center point of the subblock in the lower right corner into the affine model for calculation). In this way, the motion vector of the lower left control point and the lower right control point of the current decoding block are used (for example, the subsequent other blocks are constructed based on the motion vector of the lower left control point and the lower right control point of the current block). The candidate motion vector prediction value MVP list of the other blocks) uses an accurate value instead of an estimated value. Wherein, W is the width of the current decoded block, and H is the height of the current decoded block.

Step S1216: The video decoder performs motion compensation according to the motion vector value of each sub-block in the current decoding block to obtain the pixel prediction value of each sub-block. For example, the motion vector and reference frame index value of each sub-block are used in The corresponding sub-block is found in the reference frame, and interpolation filtering is performed to obtain the pixel prediction value of each sub-block.

Merge mode:

Step S1221: The video decoder constructs a candidate motion information list.

Specifically, the video decoder constructs a candidate motion information list (also referred to as a candidate motion vector list) through an inter prediction unit (also referred to as an inter prediction module), which may be constructed in one of two ways provided below. Or it can be constructed by a combination of two methods, and the candidate motion information list constructed is a triplet candidate motion information list; the above two methods are specifically as follows:

First, all or part of neighboring blocks of the current decoding block are traversed in a predetermined order to determine the neighboring affine decoding blocks, and the number of the determined neighboring affine decoding blocks may be one or more. For example, the neighboring blocks A, B, C, D, and E shown in FIG. 7A may be traversed in order to determine neighboring affine decoding blocks among the neighboring blocks A, B, C, D, and E. The inter prediction unit determines a set of candidate motion vector prediction values (each set of candidate motion vector prediction values is a two-tuple or three-tuple) according to each adjacent affine decoding block, and an adjacent affine is used below. The decoding block is introduced as an example. For convenience of description, the adjacent affine decoding block is called the first adjacent affine decoding block, as follows:

A first affine model is determined according to a motion vector of a control point of a first adjacent affine decoding block, and then a motion vector of a control point of the current decoding block is predicted according to the first affine model, which is specifically described as follows:

If the first adjacent affine decoding block is located above the CTU of the current decoding block and the first adjacent affine decoding block is a four-parameter affine decoding block, two lower-most two sides of the first adjacent affine decoding block are obtained. Position coordinates and motion vectors of the control points, for example, the position coordinates (x ₆ , y ₆ ) and motion vectors (vx ₆ , vy ₆ ) of the lower left control point of the first adjacent affine decoding block can be obtained, and the lower right The position coordinates (x ₇ , y ₇ ) and motion vector values (vx ₇ , vy ₇ ) of the control point.

Optionally, the motion vector of the control point of the current decoding block is predicted according to the first affine model. For example, the position coordinates of the upper left control point, the position coordinates of the upper right control point, and the position of the lower left control point of the current decoding block can be predicted. The coordinates are brought into the first affine model respectively, thereby predicting the motion vector of the upper left control point, the motion vector of the upper right control point, and the motion of the lower left control point of the current decoded block to form a candidate motion vector triplet and adding candidate motions. The information list is shown in formulas (1), (2), and (3).

Optionally, the motion vector of the control point of the current decoding block is predicted according to the first affine model. For example, the position coordinates of the upper left control point and the position coordinates of the upper right control point of the current decoding block may be brought into the first An affine model, so as to predict the motion vector of the upper left control point and the motion vector of the upper right control point of the current decoding block, form a candidate motion vector two-tuple, and add the candidate motion information list, as shown in formulas (1) and (2). Show.

In formulas (1), (2), and (3), (x ₀ , y ₀ ) are the coordinates of the upper-left control point of the current decoded block, and (x ₁ , y ₁ ) are the coordinates of the upper-right control point of the current decoded block. , (X ₂ , y ₂ ) are the coordinates of the lower left control point of the current decoding block; in addition, (vx ₀ , vy ₀ ) is the predicted motion vector of the upper left control point of the current decoding block, and (vx ₁ , vy ₁ ) is The predicted motion vector of the upper right control point of the current decoded block, (vx ₂ , vy ₂ ) is the predicted motion vector of the lower left control point of the current decoded block.

The following two examples are exemplified as Option A and Option B:

Solution A: Combine the motion information of the two control points of the current decoding block to construct a 4-parameter affine transformation model. The combination of the two control points is {CP1, CP4}, {CP2, CP3}, {CP1, CP2}, {CP2, CP4}, {CP1, CP3}, {CP3, CP4}. For example, a 4-parameter affine transformation model constructed using CP1 and CP2 control points is denoted as Affine (CP1, CP2).

{CP1, CP2} is transformed to {CP1, CP2, CP3} 's formula (9-2):

{CP1, CP3} is converted to {CP1, CP2, CP3} 's formula (9-3):

{CP2, CP3} is converted to {CP1, CP2, CP3} 's formula (10):

{CP1, CP4} is converted to {CP1, CP2, CP3} 's formula (11):

{CP2, CP4} is converted to {CP1, CP2, CP3} 's formula (12):

{CP3, CP4} is converted to {CP1, CP2, CP3} 's formula (13):

Solution B: Combine the motion information of the three control points of the current decoding block to build a 6-parameter affine transformation model. The combination of the three control points is {CP1, CP2, CP4}, {CP1, CP2, CP3}, {CP2, CP3, CP4}, {CP1, CP3, CP4}. For example, a 6-parameter affine transformation model constructed using CP1, CP2, and CP3 control points is denoted as Affine (CP1, CP2, CP3).

More directly, a set of motion vector prediction values represented by the upper left control point, the upper right control point, and the lower left control point can also be converted according to the following formula, and added to the candidate motion information list:

{CP1, CP2, CP4} is transformed into {CP1, CP2, CP3} 's formula (15):

{CP2, CP3, CP4} is converted to {CP1, CP2, CP3} 's formula (16):

{CP1, CP3, CP4} is converted to {CP1, CP2, CP3} 's formula (17):

Step S1222: The video decoder parses the bitstream to obtain an index.

Step S1223: The video decoder determines a target motion vector group from the candidate motion information list according to the index. Specifically, the target decoder motion vector group determined from the candidate motion vectors according to the index is used as the optimal candidate motion vector prediction value (optionally, when the length of the candidate motion information list is 1, it is not required Analyze the bitstream to get the index and directly determine the target motion vector group), specifically the optimal motion vector prediction value of 2 or 3 control points; for example, the video decoder parses the index number from the bitstream, and then The optimal motion vector prediction value of 2 or 3 control points is determined from the candidate motion information list, and each group of candidate motion vector prediction values in the candidate motion information list corresponds to its own index number.

Step S1224: The video decoder uses the parameter affine transformation model to obtain the motion vector value of each sub-block in the current decoding block according to the motion vector value of the control point of the current decoding block determined above.

Specifically, it is a motion vector of two (upper left control points and upper right control points) or three control points (for example, upper left control points, upper right control points, and lower left control points) included in the target candidate motion vector group. For each sub-block of the current decoding block (a sub-block can also be equivalent to a motion compensation unit), the motion information of pixels at preset positions in the motion compensation unit can be used to represent the motion of all pixels in the motion compensation unit information. Assume that the size of the motion compensation unit is MxN (M is less than or equal to the width W of the current decoding block, and N is less than or equal to the height H of the current decoding block, where M, N, W, H are positive integers, usually powers of two, such as 4, 8, 16, 32, 64, 128, etc.), the preset position pixels can be the center point of the motion compensation unit (M / 2, N / 2), the upper left pixel (0, 0), and the upper right pixel ( M-1,0), or other locations. FIG. 8A illustrates a 4 × 4 motion compensation unit, and FIG. 8B illustrates an 8 × 8 motion compensation unit.

The coordinates of the center point of the motion compensation unit relative to the top left pixel of the current decoding block are calculated using formula (5), where i is the i-th motion compensation unit in the horizontal direction (from left to right), and j is the j-th motion in the vertical direction. The compensation unit (from top to bottom), (x _{(i, j)} , y _{(i, j)} ) represents the coordinates of the center point of the (i, j) th motion compensation unit relative to the upper left control point pixel of the current decoding block. Then according to the type of the affine model (6 or 4 parameters) of the current decoding block, substitute (x _{(i, j)} , y _{(i, j)} ) into the 6 parameter affine model formula (6-1) or (x _{(i, j)} , y _{(i, j)} ) is substituted into the 4-parameter affine model formula (6-2) to obtain the motion information of the center point of each motion compensation unit as the motion vector of all pixels in the motion compensation unit (vx _{(i, j)} , vy _{(i, j)} ).

Optionally, when the current decoding block is a 6-parameter decoding block, when a motion vector of one or more sub-blocks of the current decoding block is obtained based on the target candidate motion vector group, if the lower boundary of the current decoding block is The lower boundary of the CTU where the current decoding block is located coincides, and the motion vector of the sub-block in the lower left corner of the current decoding block is a 6-parameter affine model constructed from the three control points and the current decoding block. The position coordinates (0, H) of the lower left corner are calculated, and the motion vector of the subblock in the lower right corner of the current decoding block is a 6-parameter affine model constructed according to the three control points and the right of the current decoding block. The position coordinates (W, H) of the lower corner are calculated. For example, by substituting the position coordinates (0, H) of the lower left corner of the current decoded block into the 6-parameter affine model, the motion vector of the lower left corner of the current decoded block (instead of The center point coordinate is substituted into the affine model for calculation), and the position coordinates (W, H) of the lower right corner of the current decoded block are substituted into the 6-parameter affine model to obtain the motion vector of the lower right corner of the current decoded block. (Instead of substituting the coordinates of the center point of the subblock in the lower right corner into the affine model for calculation). In this way, the motion vector of the lower left control point and the lower right control point of the current decoding block are used (for example, the subsequent other blocks are constructed based on the motion vector of the lower left control point and the lower right control point of the current block). The candidate motion information list of the other blocks) uses accurate values instead of estimated values. Wherein, W is the width of the current decoded block, and H is the height of the current decoded block.

Optionally, when the current decoding block is a 4-parameter decoding block, when the motion vectors of one or more sub-blocks of the current decoding block are obtained based on the target candidate motion vector group, if the lower boundary of the current decoding block and The lower boundary of the CTU where the current decoding block is located coincides, and the motion vector of the lower left sub-block of the current decoding block is a 4-parameter affine model constructed according to the two control points and the current decoding block's The position coordinates (0, H) of the lower left corner are calculated, and the motion vector of the sub-block in the lower right corner of the current decoding block is a 4-parameter affine model constructed according to the two control points and the right of the current decoding block. The position coordinates (W, H) of the lower corner are calculated. For example, by substituting the position coordinates (0, H) of the lower left corner of the current decoded block into the 4-parameter affine model, the motion vector of the lower left sub-block of the current decoded block (instead of the The center point coordinates are substituted into the affine model for calculation), and the position coordinates (W, H) of the lower right corner of the current decoding block are substituted into the four-parameter affine model to obtain the motion vector of the subblock in the lower right corner of the current decoding block. (Instead of substituting the coordinates of the center point of the subblock in the lower right corner into the affine model for calculation). In this way, the motion vector of the lower left control point and the lower right control point of the current decoding block are used (for example, the subsequent other blocks are constructed based on the motion vector of the lower left control point and the lower right control point of the current block). The candidate motion information list of the other blocks) uses accurate values instead of estimated values. Wherein, W is the width of the current decoded block, and H is the height of the current decoded block.

Step S1225: The video decoder performs motion compensation according to the motion vector value of each sub-block in the current decoding block to obtain the pixel prediction value of each sub-block. Specifically, according to one or more sub-blocks of the current decoding block The motion vector, the reference frame index and the prediction direction indicated by the index, to obtain a pixel prediction value of the current decoded block.

It can be understood that when the CTU of the decoding tree unit where the first neighboring affine decoding block is located is above the current decoding block position, the information of the lowest control point of the first neighboring affine decoding block has been changed from Read in memory; therefore, in the above solution, in the process of constructing candidate motion vectors according to the first set of control points of the first neighboring affine decoding block, the first set of control points includes the first neighboring affine decoding block Lower left control point and lower right control point; instead of fixing the upper left control point, upper right control point, and lower left control point of the first adjacent decoding block as the first group of control points as in the prior art (or fixing the first phase The upper left control point and the upper right control point of the neighboring decoding blocks are used as the first group of control points). Therefore, by adopting the method for determining the first set of control points in this application, the information of the first set of control points (for example, position coordinates, motion vectors, etc.) can directly reuse the information read from the memory, thereby reducing the memory read. This improves the decoding performance.

FIG. 10 is a schematic block diagram of an implementation manner of an encoding device or a decoding device (hereinafter referred to as a decoding device 1000) according to an embodiment of the present application. The decoding device 1000 may include a processor 1010, a memory 1030, and a bus system 1050. The processor and the memory are connected through a bus system, the memory is used to store instructions, and the processor is used to execute the instructions stored in the memory. The memory of the encoding device stores program code, and the processor can call the program code stored in the memory to perform various video encoding or decoding methods described in this application, especially the video encoding or decoding methods in various new inter prediction modes. , And methods for predicting motion information in various new inter prediction modes. To avoid repetition, it will not be described in detail here.

In the embodiment of the present application, the processor 1010 may be a Central Processing Unit (“CPU”), and the processor 1010 may also be another general-purpose processor, a digital signal processor (DSP), or a dedicated integration. Circuits (ASICs), off-the-shelf programmable gate arrays (FPGAs) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general-purpose processor may be a microprocessor or the processor may be any conventional processor or the like.

The memory 1030 may include a read only memory (ROM) device or a random access memory (RAM) device. Any other suitable type of storage device may also be used as the memory 1030. The memory 1030 may include code and data 1031 accessed by the processor 1010 using the bus 1050. The memory 1030 may further include an operating system 1033 and an application program 1035. The application program 1035 includes at least one program that allows the processor 1010 to perform the video encoding or decoding method (especially the encoding method or the decoding method described in this application). For example, the application program 1035 may include applications 1 to N, which further includes a video encoding or decoding application (referred to as a video decoding application) that executes the video encoding or decoding method described in this application.

The bus system 1050 may include a power bus, a control bus, and a status signal bus in addition to a data bus. However, for the sake of clarity, various buses are marked as the bus system 1050 in the figure.

Optionally, the decoding device 1000 may further include one or more output devices, such as a display 1070. In one example, the display 1070 may be a tactile display that incorporates the display with a tactile unit operatively sensing a touch input. The display 1070 may be connected to the processor 1010 via a bus 1050.

FIG. 11 is an explanatory diagram of an example of a video encoding system 1100 including the encoder 20 of FIG. 2A and / or the decoder 200 of FIG. 2B according to an exemplary embodiment. The system 1100 may implement a combination of various techniques of the present application. In the illustrated embodiment, the video encoding system 1100 may include an imaging device 1101, a video encoder 100, a video decoder 200 (and / or a video encoder implemented by the logic circuit 1107 of the processing unit 1106), an antenna 1102, One or more processors 1103, one or more memories 1104, and / or a display device 1105.

As shown, the imaging device 1101, the antenna 1102, the processing unit 1106, the logic circuit 1107, the video encoder 100, the video decoder 200, the processor 1103, the memory 1104, and / or the display device 1105 can communicate with each other. As discussed, although the video encoding system 1100 is shown with the video encoder 100 and the video decoder 200, in different examples, the video encoding system 1100 may include only the video encoder 100 or only the video decoder 200.

In some examples, as shown, the video encoding system 1100 may include an antenna 1102. For example, the antenna 1102 may be used to transmit or receive an encoded bit stream of video data. In addition, in some examples, the video encoding system 1100 may include a display device 1105. The display device 1105 may be used to present video data. In some examples, as shown, the logic circuit 1107 may be implemented by the processing unit 1106. The processing unit 1106 may include application-specific integrated circuit (ASIC) logic, a graphics processor, a general-purpose processor, and the like. The video encoding system 1100 may also include an optional processor 1103, which may similarly include application-specific integrated circuit (ASIC) logic, a graphics processor, a general-purpose processor, and the like. In some examples, the logic circuit 1107 may be implemented by hardware, such as dedicated hardware for video encoding, and the processor 1103 may be implemented by general software, operating system, and the like. In addition, the memory 1104 may be any type of memory, such as volatile memory (for example, Static Random Access Memory (SRAM), Dynamic Random Access Memory (DRAM), etc.) or non-volatile memory Memory (for example, flash memory, etc.). In a non-limiting example, the memory 1104 may be implemented by a cache memory. In some examples, the logic circuit 1107 may access the memory 1104 (eg, for implementing an image buffer). In other examples, the logic circuit 1107 and / or the processing unit 1106 may include a memory (eg, a cache, etc.) for implementing an image buffer or the like.

In some examples, video encoder 100 implemented by logic circuits may include an image buffer (eg, implemented by processing unit 1106 or memory 1104) and a graphics processing unit (eg, implemented by processing unit 1106). The graphics processing unit may be communicatively coupled to the image buffer. The graphics processing unit may include a video encoder 100 implemented by a logic circuit 1107 to implement the various modules discussed with reference to FIG. 2A and / or any other encoder system or subsystem described herein. Logic circuits can be used to perform various operations discussed herein.

Video decoder 200 may be implemented in a similar manner through logic circuit 1107 to implement the various modules discussed with reference to decoder 200 of FIG. 2B and / or any other decoder system or subsystem described herein. In some examples, video decoder 200 implemented by a logic circuit may include an image buffer (implemented by processing unit 2820 or memory 1104) and a graphics processing unit (eg, implemented by processing unit 1106). The graphics processing unit may be communicatively coupled to the image buffer. The graphics processing unit may include a video decoder 200 implemented by a logic circuit 1107 to implement various modules discussed with reference to FIG. 2B and / or any other decoder system or subsystem described herein.

In some examples, the antenna 1102 of the video encoding system 1100 may be used to receive an encoded bit stream of video data. As discussed, the encoded bitstream may contain data, indicators, index values, mode selection data, etc. related to encoded video frames discussed herein, such as data related to coded segmentation (e.g., transform coefficients or quantized transform coefficients , (As discussed) optional indicators, and / or data defining code partitions). The video encoding system 1100 may also include a video decoder 200 coupled to the antenna 1102 and used to decode the encoded bitstream. The display device 1105 is used to present a video frame.

In the steps of the above method flow, the description order of the steps does not represent the execution order of the steps, and it is feasible to perform according to the above description order, and it is also possible to perform without the above description order. For example, the above step S1211 may be performed after step S1212, or may be performed before step S1212; the above step S1221 may be performed after step S1222, or may be performed before step S1222; the remaining steps are not illustrated here one by one.

Those skilled in the art can appreciate that the functions described in connection with the various illustrative logical blocks, modules, and algorithm steps disclosed in this disclosure may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions described by the various illustrative logical blocks, modules, and steps may be stored or transmitted as one or more instructions or code on a computer-readable medium and executed by a hardware-based processing unit. Computer-readable media may include computer-readable storage media, which corresponds to tangible media, such as data storage media, or communication media including any medium that facilitates transfer of a computer program from one place to another (e.g., according to a communication protocol) . In this manner, computer-readable media may generally correspond to (1) tangible computer-readable storage media that is non-transitory, or (2) a communication medium such as a signal or carrier wave. A data storage medium may be any available medium that can be accessed by one or more computers or one or more processors to retrieve instructions, code, and / or data structures used to implement the techniques described in this application. The computer program product may include a computer-readable medium.

By way of example, and not limitation, such computer-readable storage media may include RAM, ROM, EEPROM, CD-ROM or other optical disk storage devices, magnetic disk storage devices or other magnetic storage devices, flash memory, or may be used to store instructions or data structures Any form of desired program code and any other medium accessible by a computer. Also, any connection is properly termed a computer-readable medium. For example, a coaxial cable is used to transmit instructions from a website, server, or other remote source using coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared, radio, and microwave. Wire, fiber optic cable, twisted pair, DSL or wireless technologies such as infrared, radio and microwave are included in the definition of media. It should be understood, however, that the computer-readable storage media and data storage media do not include connections, carrier waves, signals, or other temporary media, but are instead directed to non-transitory tangible storage media. As used herein, magnetic disks and compact discs include compact discs (CDs), laser discs, optical discs, digital versatile discs (DVDs), and Blu-ray discs, where disks typically reproduce data magnetically, and optical discs use lasers to reproduce optically data. Combinations of the above should also be included within the scope of computer-readable media.

Can be processed by one or more, such as one or more digital signal processors (DSPs), general purpose microprocessors, application specific integrated circuits (ASICs), field programmable logic arrays (FPGAs), or other equivalent integrated or discrete logic circuits To execute instructions. Accordingly, the term "processor" as used herein may refer to any of the aforementioned structures or any other structure suitable for implementing the techniques described herein. Additionally, in some aspects, the functions described by the various illustrative logical blocks, modules, and steps described herein may be provided within dedicated hardware and / or software modules configured for encoding and decoding, or Into the combined codec. Moreover, the techniques can be fully implemented in one or more circuits or logic elements.

The techniques of this application may be implemented in a wide variety of devices or devices, including a wireless handset, an integrated circuit (IC), or a group of ICs (eg, a chipset). Various components, modules, or units are described in this application to emphasize functional aspects of the apparatus for performing the disclosed techniques, but do not necessarily need to be implemented by different hardware units. In fact, as described above, the various units may be combined in a codec hardware unit in combination with suitable software and / or firmware, or through interoperable hardware units (including one or more processors as described above) provide.

The above description is only an exemplary specific implementation of the present application, but the scope of protection of the present application is not limited to this. Any person skilled in the art can easily think of changes or changes within the technical scope disclosed in this application. Replacement shall be covered by the protection scope of this application. Therefore, the protection scope of this application shall be subject to the protection scope of the claims.

Claims

An encoding method, comprising:

Determining a target candidate motion vector group from the candidate motion vector list according to the rate-distortion cost criterion; the target candidate motion vector group represents a motion vector prediction value of a set of control points of the current coding block;

Coding an index corresponding to the target candidate motion vector into a code stream, and transmitting the code stream;

Wherein, if the first neighboring affine coding block is a four-parameter affine coding block, and the first neighboring affine coding block is located in the coding tree unit CTU above the current coding block, the candidate motion vector list A first group of candidate motion vector prediction values is included, and the first group of candidate motion vector prediction values is obtained based on a lower left control point and a lower right control point of the first neighboring affine coding block.
The method according to claim 1, characterized in that:

If the current coding block is a four-parameter affine coding block, the first set of candidate motion vector prediction values is used to represent motion vector prediction values of an upper left control point and an upper right control point of the current coding block;

If the current coding block is a six-parameter affine coding block, the first set of candidate motion vector prediction values is used to represent a motion vector prediction of an upper left control point, an upper right control point, and a lower left fixed point control point of the current coding block. value.
The method according to claim 1 or 2, wherein the first set of candidate motion vector prediction values is obtained based on a lower left control point and a lower right control point of the first neighboring affine coding block, and specifically for:

If the current coding block is a four-parameter affine coding block, the first set of candidate motion vector prediction values is obtained by substituting the position coordinates of the upper left control point and the upper right control point of the current coding block into a first affine model. ;or,

If the current coding block is a six-parameter affine coding block, the first set of candidate motion vector prediction values is to substitute the position coordinates of the upper left control point, upper right control point, and lower left fixed point control point of the current coding block into the first Obtained from the affine model;

The first affine model is determined based on a motion vector and a position coordinate of a lower left control point and a lower right control point of the first adjacent affine coding block.
The method according to any one of claims 1-3, further comprising:

Using the target candidate motion vector group as a search starting point to search for a motion vector of a set of control points with the lowest cost within a preset search range according to a rate distortion cost criterion;

Determining a motion vector difference MVD between a motion vector of the set of control points and the target candidate motion vector group;

The encoding the index corresponding to the target candidate motion vector into a code stream and transmitting the code stream includes:

Coding the MVD and an index corresponding to the target candidate motion vector group into a code stream to be transmitted, and transmitting the code stream.
The method according to any one of claims 1 to 3, wherein the coding an index corresponding to the target candidate motion vector into a code stream and transmitting the code stream comprises:

Indexes corresponding to the target candidate motion vector group, reference frame index, and prediction direction are coded into a code stream, and the code stream is transmitted.
The method according to any one of claims 1-5, wherein a position coordinate (x 6 , y 6 ) of a lower left control point of the first adjacent affine coding block and a position of the lower right control point The position coordinates (x 7 , y 7 ) are all calculated and derived based on the position coordinates (x 4 , y 4 ) of the upper-left control point of the first neighboring affine coding block, where the first neighboring affine coding block The position coordinates (x 6 , y 6 ) of the lower left control point of the affine coding block are (x 4 , y 4 + cuH), and the position coordinates (x 7 , y 7 ) is (x 4 + cuW, y 4 + cuH), cuW is the width of the first neighboring affine coding block, and cuH is the height of the first neighboring affine coding block.
The method according to claim 6, wherein the motion vector of the lower left control point of the first adjacent affine coding block is the motion vector of the lower left sub-block of the first adjacent affine coding block, and The motion vector of the lower right control point of the first neighboring affine coding block is a motion vector of the lower right sub-block of the first neighboring affine coding block.
A decoding method, comprising:

Parse the code stream to obtain an index, where the index is used to indicate the target candidate motion vector group of the current decoded block;

According to the index, the target candidate motion vector group is determined from a candidate motion vector list, and the target candidate motion vector group represents a motion vector prediction value of a set of control points of the current decoding block, where if the first neighboring simulation The affine decoding block is a four-parameter affine decoding block, and the first neighboring affine decoding block is located above the current decoding block in a decoding tree unit CTU, then the candidate motion vector list includes a first group of candidate motion vector predictions. Value, the first set of candidate motion vector prediction values is obtained based on a lower left control point and a lower right control point of the first neighboring affine decoding block;

Obtaining a motion vector of one or more sub-blocks of the current decoding block based on the target candidate motion vector group;

Based on the motion vectors of one or more sub-blocks of the current decoding block, a pixel prediction value of the current decoding block is obtained by prediction.
The method according to claim 8, characterized in that:

If the current decoding block is a four-parameter affine decoding block, the first set of candidate motion vector prediction values is used to represent the motion vector prediction values of the upper left control point and the upper right control point of the current decoding block;

If the current decoding block is a six-parameter affine decoding block, the first set of candidate motion vector prediction values is used to represent motion vector prediction of the upper left control point, upper right control point, and lower left fixed point control point of the current decoding block. value.
The method according to claim 8 or 9, wherein the first set of candidate motion vector prediction values is obtained based on a lower left control point and a lower right control point of the first adjacent affine decoding block, and specifically for:

If the current decoding block is a four-parameter affine decoding block, the first set of candidate motion vector prediction values is obtained by substituting the position coordinates of the upper left control point and the upper right control point of the current decoding block into the first affine model. ;or,

If the current decoding block is a six-parameter affine decoding block, the first set of candidate motion vector prediction values is to substitute the position coordinates of the upper left control point, upper right control point, and lower left fixed point control point of the current decoding block into the first Obtained from the affine model;

The first affine model is determined based on motion vectors and position coordinates of a lower left control point and a lower right control point of the first adjacent affine decoding block.
The method according to any one of claims 8 to 10, wherein the obtaining a motion vector of one or more sub-blocks of the current decoding block based on the target candidate motion vector group is specifically:

Obtaining a motion vector of one or more sub-blocks of the current decoding block based on a second affine model, the second affine model is based on the target candidate motion vector group and a set of control points of the current decoding block The position coordinates are determined.
The method according to any one of claims 8-11, wherein the obtaining a motion vector of one or more sub-blocks of the current decoding block based on the target candidate motion vector group comprises:

Obtaining a new candidate motion vector group based on the motion vector difference MVD parsed from the code stream and the target candidate motion vector group indicated by the index;

Based on the new candidate motion vector group, a motion vector of one or more sub-blocks of the current decoding block is obtained.
The method according to any one of claims 8 to 11, wherein the predicting and obtaining a pixel prediction value of the current decoded block based on a motion vector of one or more sub-blocks of the current decoded block comprises:

According to the motion vector of one or more sub-blocks of the current decoding block, and the reference frame index and prediction direction indicated by the index, a pixel prediction value of the current decoding block is obtained by prediction.
The method according to any one of claims 8-13, wherein a position coordinate (x 6 , y 6 ) of a lower left control point of the first adjacent affine decoding block and a position of the lower right control point The position coordinates (x 7 , y 7 ) are all obtained by calculating and deriving from the position coordinates (x 4 , y 4 ) of the upper-left control point of the first adjacent affine decoding block, where the first adjacent affine decoding block The position coordinates (x 6 , y 6 ) of the lower left control point of the affine decoding block are (x 4 , y 4 + cuH), and the position coordinates of the lower right control point of the first adjacent affine decoding block (x 7 , y 7 ) is (x 4 + cuW, y 4 + cuH), cuW is the width of the first neighboring affine decoding block, and cuH is the height of the first neighboring affine decoding block.
The method according to claim 14, wherein a motion vector of a lower left control point of the first adjacent affine decoding block is a motion vector of a lower left sub-block of the first adjacent affine decoding block, and The motion vector of the lower right control point of the first adjacent affine decoding block is the motion vector of the lower right sub-block of the first adjacent affine decoding block.
The method according to any one of claims 8-15, wherein, in the process of obtaining a motion vector of one or more sub-blocks of the current decoding block based on the target candidate motion vector group, if If the lower boundary of the current decoded block coincides with the lower boundary of the CTU where the current decoded block is located, then the motion vector of the sub-block at the lower left vertex of the current decoded block is based on the target candidate motion vector group and the current decode The position coordinates (0, H) of the lower left vertex of the block are calculated, and the motion vector of the sub-block of the lower right vertex of the current decoded block is based on the target candidate motion vector group and the lower right vertex of the current decoded block. The position coordinates (W, H) are calculated, where W is equal to the width of the current decoded block, H is equal to the height of the current decoded block, and the coordinates of the upper left vertex of the current decoded block are (0, 0).
A video encoder includes:

An inter prediction unit, configured to determine a target candidate motion vector group from a candidate motion vector list according to a rate distortion cost criterion; the target candidate motion vector group represents a motion vector prediction value of a set of control points of a current coding block;

An entropy coding unit, configured to encode an index corresponding to the target candidate motion vector into a code stream and transmit the code stream;

Wherein, if the first neighboring affine coding block is a four-parameter affine coding block, and the first neighboring affine coding block is located in the coding tree unit CTU above the current coding block, the candidate motion vector list A first group of candidate motion vector prediction values is included, and the first group of candidate motion vector prediction values is obtained based on a lower left control point and a lower right control point of the first neighboring affine coding block.
The video encoder according to claim 17, wherein:

If the current coding block is a four-parameter affine coding block, the first set of candidate motion vector prediction values is used to represent motion vector prediction values of an upper left control point and an upper right control point of the current coding block;

If the current coding block is a six-parameter affine coding block, the first set of candidate motion vector prediction values is used to represent a motion vector prediction of an upper left control point, an upper right control point, and a lower left fixed point control point of the current coding block. value.
The video encoder according to claim 17 or 18, wherein the first set of candidate motion vector prediction values is obtained based on a lower left control point and a lower right control point of the first neighboring affine coding block ,Specifically:

If the current coding block is a four-parameter affine coding block, the first set of candidate motion vector prediction values is obtained by substituting the position coordinates of the upper left control point and the upper right control point of the current coding block into a first affine model. ;or,

If the current coding block is a six-parameter affine coding block, the first set of candidate motion vector prediction values is to substitute the position coordinates of the upper left control point, upper right control point, and lower left fixed point control point of the current coding block into the first Obtained from the affine model;

The first affine model is determined based on a motion vector and a position coordinate of a lower left control point and a lower right control point of the first adjacent affine coding block.
The video encoder according to any one of claims 17 to 19, wherein:

The inter prediction unit is further configured to use the target candidate motion vector group as a search starting point to search for a motion vector of a group of control points with the lowest cost within a preset search range according to a rate distortion cost criterion; and determine the A motion vector difference MVD between a motion vector of a set of control points and the target candidate motion vector group;

The entropy encoding unit is specifically configured to encode the MVD and an index corresponding to the target candidate motion vector group into a code stream to be transmitted, and transmit the code stream.
The video encoder according to any one of claims 17 to 19, wherein the entropy coding unit is specifically configured to code an index corresponding to the target candidate motion vector group, a reference frame index, and a prediction direction into Code stream, and transmitting the code stream.
The video encoder as claimed in claim any one of claims 17-21, wherein the position coordinates of the lower left first adjacent control point affine encoded block (x 6, y 6), and said lower right control The position coordinates (x 7 , y 7 ) of the points are all calculated and derived based on the position coordinates (x 4 , y 4 ) of the upper-left control point of the first adjacent affine coding block, where the first phase The position coordinates (x 6 , y 6 ) of the lower left control point of the adjacent affine coding block is (x 4 , y 4 + cuH), and the position coordinates (x of the lower right control point of the first adjacent affine coding block) 7 , y 7 ) is (x 4 + cuW, y 4 + cuH), cuW is the width of the first neighboring affine coding block, and cuH is the height of the first neighboring affine coding block.
The video encoder according to claim 22, wherein a motion vector of a lower left control point of the first adjacent affine coding block is a motion vector of a lower left sub-block of the first adjacent affine coding block , A motion vector of a lower right control point of the first adjacent affine coding block is a motion vector of a lower right sub-block of the first adjacent affine coding block.
A video decoder, comprising:

An entropy decoding unit, configured to parse a code stream to obtain an index, where the index is used to indicate a target candidate motion vector group of a current decoding block;

An inter prediction unit, configured to determine the target candidate motion vector group from a candidate motion vector list according to the index, where the target candidate motion vector group represents a motion vector prediction value of a set of control points of a current decoding block, where If the first neighboring affine decoding block is a four-parameter affine decoding block and the first neighboring affine decoding block is located above the current decoding block decoding tree unit CTU, the list of candidate motion vectors includes A first set of candidate motion vector prediction values, the first set of candidate motion vector prediction values being obtained based on a lower left control point and a lower right control point of the first adjacent affine decoding block; and based on the target candidate motion The vector group obtains a motion vector of one or more sub-blocks of the current decoding block; based on the motion vectors of the one or more sub-blocks of the current decoding block, predicts and obtains a pixel prediction value of the current decoding block.
The video decoder according to claim 24, wherein:

If the current decoding block is a four-parameter affine decoding block, the first set of candidate motion vector prediction values is used to represent the motion vector prediction values of the upper left control point and the upper right control point of the current decoding block;

If the current decoding block is a six-parameter affine decoding block, the first set of candidate motion vector prediction values is used to represent motion vector prediction of the upper left control point, upper right control point, and lower left fixed point control point of the current decoding block. value.
The video decoder according to claim 24 or 25, wherein the first set of candidate motion vector prediction values is obtained based on a lower left control point and a lower right control point of the first adjacent affine decoding block ,Specifically:

If the current decoding block is a four-parameter affine decoding block, the first set of candidate motion vector prediction values is obtained by substituting the position coordinates of the upper left control point and the upper right control point of the current decoding block into the first affine model. ;or,

If the current decoding block is a six-parameter affine decoding block, the first set of candidate motion vector prediction values is to substitute the position coordinates of the upper left control point, upper right control point, and lower left fixed point control point of the current decoding block into the first Obtained from the affine model;

The first affine model is determined based on motion vectors and position coordinates of a lower left control point and a lower right control point of the first adjacent affine decoding block.
The video decoder according to any one of claims 24-26, wherein the inter-prediction unit is configured to obtain the one The motion vector is specifically: obtaining a motion vector of one or more sub-blocks of the current decoding block based on a second affine model, and the second affine model is based on the target candidate motion vector group and the current decoding block The position coordinates of a set of control points are determined.
The video decoder according to any one of claims 24-27, characterized in that the inter prediction unit is configured to obtain one or more sub-blocks of the current decoded block based on the target candidate motion vector group. The motion vector is specifically: obtaining a new candidate motion vector group based on the motion vector difference MVD parsed from the code stream and the target candidate motion vector group indicated by the index; and based on the new candidate motion vector Group to obtain a motion vector of one or more sub-blocks of the current decoding block.
The video decoder according to any one of claims 24-27, wherein the inter prediction unit is configured to predict and obtain the current based on a motion vector of one or more sub-blocks of the current decoding block. The pixel predicted value of the decoded block is specifically: according to the motion vector of one or more sub-blocks of the current decoded block, and the reference frame index and prediction direction indicated by the index, the pixel predicted value of the current decoded block is obtained by prediction. .
The video decoder according to any one of claims 24-29, wherein the position coordinates (x 6 , y 6 ) of the lower left control point of the first adjacent affine decoding block and the lower right control The position coordinates (x 7 , y 7 ) of the points are all obtained by calculating and deriving according to the position coordinates (x 4 , y 4 ) of the upper-left control point of the first adjacent affine decoding block, where the first phase The position coordinate (x 6 , y 6 ) of the lower left control point of the adjacent affine decoding block is (x 4 , y 4 + cuH), and the position coordinate (x of the lower right control point of the first adjacent affine decoding block) 7 , y 7 ) is (x 4 + cuW, y 4 + cuH), cuW is the width of the first neighboring affine decoding block, and cuH is the height of the first neighboring affine decoding block.
The video decoder according to claim 30, wherein a motion vector of a lower left control point of the first adjacent affine decoding block is a motion vector of a lower left sub-block of the first adjacent affine decoding block , A motion vector of a lower right control point of the first adjacent affine decoding block is a motion vector of a lower right sub-block of the first adjacent affine decoding block.
The video decoder according to any one of claims 24-31, wherein in the process of obtaining a motion vector of one or more sub-blocks of the current decoding block based on the target candidate motion vector group, If the lower boundary of the current decoding block coincides with the lower boundary of the CTU where the current decoding block is located, the motion vector of the sub-block at the lower left vertex of the current decoding block is based on the target candidate motion vector group and the The position coordinates (0, H) of the lower left vertex of the current decoded block are calculated, and the motion vector of the subblock of the lower right vertex of the current decoded block is according to the target candidate motion vector group and the lower right of the current decoded block. The position coordinates (W, H) of the vertices are calculated, where W is equal to the width of the current decoded block, H is equal to the height of the current decoded block, and the coordinates of the upper left vertex of the current decoded block are (0, 0).