JP2020202454A - Predictive image generation unit, moving image decoding device, and moving image encoding device - Google Patents

Abstract

To solve the problem in which, since prediction to improve the image quality using gradient images additionally requires a calculation of a sum of absolute values of differences between two interpolated images for determining whether to perform processing for each processing unit, a processing amount is not reduced in the worst case.SOLUTION: A predictive image generation unit that generates a predictive image from two interpolated images using bidirectional gradient change processing is included. In the prediction image generation unit, the calculation accuracy of the difference between the two interpolated images is made the same, whether to perform processing for each processing unit is determined and a predicted image is generated.SELECTED DRAWING: Figure 12

Description

Embodiments of the present invention relate to a predictive image generator, a moving image decoding device, and a moving image coding device.

In order to efficiently transmit or record a moving image, a moving image coding device that generates encoded data by encoding the moving image, and a moving image that generates a decoded image by decoding the encoded data. An image decoding device is used.

Specific examples of the moving image coding method include H.264 / AVC and HEVC (High-Efficiency Video Coding) method.

In such a moving image coding method, the image (picture) constituting the moving image is a slice obtained by dividing the image and a coding tree unit (CTU) obtained by dividing the slice. ), A coding unit obtained by dividing a coding tree unit (sometimes called a coding unit (CU)), and a conversion unit (TU:) obtained by dividing a coding unit. It is managed by a hierarchical structure consisting of (Transform Unit), and is encoded / decoded for each CU.

Further, in such a moving image coding method, a predicted image is usually generated based on a locally decoded image obtained by encoding / decoding an input image, and the predicted image is obtained from the input image (original image). The prediction error obtained by subtraction (sometimes referred to as "difference image" or "residual image") is encoded. Examples of the method for generating a prediction image include inter-screen prediction (inter-screen prediction) and in-screen prediction (intra-prediction).

In addition, non-patent documents can be mentioned as a technique for coding and decoding moving images in recent years. In particular, when a predicted image is derived from motion compensation (interpolated image) of biprediction, a gradient image is used to improve the image quality. BDOF technology is disclosed.

"Versatile Video Coding (Draft 5)", JVET-N1001, Joint Video Exploration Team (JVET) of ITU-T SG 16 WP 3 and ISO / IEC JTC 1 / SC 29/WG 11, 2019

In Non-Patent Document 1, in BDOF technology, it is necessary to calculate the sum of the absolute values of the differences between the two interpolated images in order to determine whether or not to perform processing for each processing unit. Since the processing can be terminated in the middle, the processing amount can be reduced on average, but the processing amount of the additional difference absolute value sum is added, so the processing amount was not reduced in the worst case. There was a problem.

The moving image decoding device according to one aspect of the present invention has a prediction image generation unit using bidirectional gradient change processing that generates a prediction image by a gradient change from two interpolated images, and the prediction image generation unit is From the two interpolated images, the L0 and L1 prediction generators that generate the L0 prediction image and the L1 prediction image for each coding unit, and the L0 prediction image and the L1 prediction image, bidirectional gradient change processing is performed for each coding unit. A flag setting unit that determines whether or not to perform the operation, a gradient image generation unit that generates four gradient images in the horizontal direction and the vertical direction from the L0 prediction image and the L1 prediction image, and the L0 prediction image and the L1 prediction image. And the correlation parameter calculation unit that calculates the correlation parameter for each processing unit from the product-sum calculation of the four gradient images, and the motion compensation that derives the value for correcting the bidirectional prediction image from the gradient image and the correlation parameter. It has a correction value derivation unit, a bidirectional prediction image generation unit that generates a prediction image from the L0 prediction image, the L1 prediction image, and the motion compensation correction value, and the flag setting unit and the correlation parameter calculation unit have the L0. It is characterized in that the calculation accuracy of the difference between the predicted image and the L1 predicted image is the same.

Further, in the moving image decoding device according to one aspect of the present invention, the calculation accuracy of the difference between the L0 predicted image and the L1 predicted image is made constant in the flag setting unit and the correlation parameter calculation unit regardless of the pixel bit length. It is characterized by that.

According to the above configuration, any of the above problems can be solved.

It is the schematic which shows the structure of the image transmission system which concerns on this embodiment. It is a figure which showed the structure of the transmission device which mounted the moving image coding device which concerns on this embodiment, and the receiving device which mounted on moving image decoding device. (a) shows a transmitting device equipped with a moving image coding device, and (b) shows a receiving device equipped with a moving image decoding device. It is a figure which showed the structure of the recording apparatus which carried out the moving image coding apparatus which concerns on this embodiment, and the reproduction apparatus which mounted on moving image decoding apparatus. (a) shows a recording device equipped with a moving image coding device, and (b) shows a reproducing device equipped with a moving image decoding device. It is a figure which shows the hierarchical structure of the data of a coded stream. It is a figure which shows the division example of CTU. It is a conceptual diagram which shows an example of a reference picture and a reference picture list. It is a schematic diagram which shows the structure of the moving image decoding apparatus. It is the schematic which shows the structure of the inter prediction parameter decoding part. It is a schematic diagram which shows the structure of the merge prediction parameter derivation part and AMVP prediction parameter derivation part. It is the schematic which shows the structure of the inter prediction image generation part. It is a figure which shows an example of the flowchart explaining the flow of the process of deriving the prediction image by the motion compensation part which has the motion compensation function using BDOF prediction which concerns on this embodiment. It is the schematic which shows the structure of the BDOF part which concerns on this embodiment. It is a figure which shows an example of the flowchart explaining the flow of the process which the BDOF part which concerns on this embodiment generates a predicted image. It is a figure which shows an example of the area where the BDOF part which concerns on this embodiment executes BDOF padding. It is a figure which shows an example of the unit of BDOF processing and the reading area of the BDOF part which concerns on this embodiment. It is a block diagram which shows the structure of the moving image coding apparatus. It is the schematic which shows the structure of the inter prediction parameter coding part.

(First Embodiment)
Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic view showing the configuration of the image transmission system 1 according to the present embodiment.

The image transmission system 1 is a system that transmits a coded stream in which a coded image is encoded, decodes the transmitted coded stream, and displays an image. The image transmission system 1 includes a moving image coding device (image coding device) 11, a network 21, a moving image decoding device (image decoding device) 31, and a moving image display device (image display device) 41. ..

The image T is input to the moving image coding device 11.

The network 21 transmits the coded stream Te generated by the moving image coding device 11 to the moving image decoding device 31. The network 21 is an Internet (Internet), a wide area network (WAN: Wide Area Network), a small network (LAN: Local Area Network), or a combination thereof. The network 21 is not necessarily limited to a two-way communication network, but may be a one-way communication network that transmits broadcast waves such as terrestrial digital broadcasting and satellite broadcasting. Further, the network 21 may be replaced with a storage medium such as a DVD (Digital Versatile Disc: registered trademark) or BD (Blue-ray Disc: registered trademark) on which an encoded stream Te is recorded.

The moving image decoding device 31 decodes each of the coded streams Te transmitted by the network 21 and generates one or a plurality of decoded images Td.

The moving image display device 41 displays all or a part of one or a plurality of decoded images Td generated by the moving image decoding device 31. The moving image display device 41 includes, for example, a display device such as a liquid crystal display or an organic EL (Electro-luminescence) display. Examples of the display form include stationary, mobile, and HMD. Further, when the moving image decoding device 31 has a high processing capacity, an image having a high image quality is displayed, and when the moving image decoding device 31 has a lower processing capacity, an image which does not require a high processing capacity and a display capacity is displayed. ..

<Operator>
The operators used herein are described below.

>> is the right bit shift, << is the left bit shift, & is the bitwise AND, | is the bitwise OR, | = is the OR assignment operator, and || is the OR.

x? y: z is a ternary operator that takes y when x is true (other than 0) and z when x is false (0).

Clip3 (a, b, c) is a function that clips c to a value greater than or equal to a and less than or equal to b, returning a if c <a, returning b if c> b, and other cases. Is a function that returns c (where a <= b).

abs (a) is a function that returns the absolute value of a.

Int (a) is a function that returns an integer value of a.

floor (a) is a function that returns the largest integer less than or equal to a.

ceil (a) is a function that returns the smallest integer greater than or equal to a.

a / d represents the division of a by d (rounded down to the nearest whole number).

a ^ b represents a to the power of b.

sign (a) is a function that returns the sign of a. sign (a) = a> 0? 1: a == 0? 0: -1
log2 (a) is a function that returns a logarithm with the base of a as 2.

Max (a, b) is a function that returns a when a> = b and b when a <b.

Min (a, b) is a function that returns b when a <= b, a, and a> b.

Round (a) is a function that returns the rounded value of a. Round (a) = sign (a) * floor (abs (a) +0.5).

<Structure of coded stream Te>
Prior to the detailed description of the moving image coding device 11 and the moving image decoding device 31 according to the present embodiment, the data of the coded stream Te generated by the moving image coding device 11 and decoded by the moving image decoding device 31. The structure will be described.

FIG. 4 is a diagram showing a hierarchical structure of data in the coded stream Te. The coded stream Te typically includes a sequence and a plurality of pictures that make up the sequence. In FIGS. 4 (a) to 4 (f), a coded video sequence that defines the sequence SEQ, a coded picture that defines the picture PICT, a coded slice that defines the slice S, and a coded slice that defines the slice data, respectively. It is a figure which shows the coded tree unit included in the data, the coded slice data, and the coded unit included in a coded tree unit.

(Encoded video sequence)
The coded video sequence defines a set of data that the moving image decoding device 31 refers to in order to decode the sequence SEQ to be processed. As shown in FIG. 4A, the sequence SEQ includes a video parameter set (Video Parameter Set), a sequence parameter set SPS (Sequence Parameter Set), a picture parameter set PPS (Picture Parameter Set), a picture PICT, and an additional extension. Information SEI (Supplemental Enhancement Information) is included.

The video parameter set VPS is a set of coding parameters common to a plurality of moving images in a moving image composed of a plurality of layers, and a set of coding parameters related to the plurality of layers included in the moving image and individual layers. The set is defined.

The sequence parameter set SPS defines a set of coding parameters that the moving image decoding device 31 refers to in order to decode the target sequence. For example, the width and height of the picture are specified. In addition, there may be a plurality of SPS. In that case, select one of multiple SPSs from PPS.

The picture parameter set PPS defines a set of coding parameters that the moving image decoding device 31 refers to in order to decode each picture in the target sequence. For example, a reference value of the quantization width used for decoding a picture (pic_init_qp_minus26) and a flag indicating the application of weighted prediction (weighted_pred_flag) are included. There may be a plurality of PPSs. In that case, one of a plurality of PPSs is selected from each picture in the target sequence.

(Encoded picture)
The coded picture defines a set of data referred to by the moving image decoding device 31 in order to decode the picture PICT to be processed. The picture PICT includes slices 0 to NS-1 as shown in Figure 4 (b) (NS is the total number of slices contained in the picture PICT).

In the following, when it is not necessary to distinguish between slice 0 and slice NS-1, the subscripts of the symbols may be omitted. The same applies to the data included in the coded stream Te described below and with subscripts.

(Coded slice)
The coded slice defines a set of data referred to by the moving image decoding device 31 in order to decode the slice S to be processed. The slice contains a slice header and slice data as shown in FIG. 4 (c).

The slice header contains a group of coding parameters referred to by the moving image decoding device 31 to determine the decoding method of the target slice. The slice type specification information (slice_type) that specifies the slice type is an example of the coding parameters included in the slice header.

Slice types that can be specified by the slice type specification information include (1) I slices that use only intra-prediction during coding, and (2) P-slices that use unidirectional prediction or intra-prediction during coding. (3) Examples include a B slice that uses unidirectional prediction, bidirectional prediction, or intra prediction at the time of coding. Note that the inter-prediction is not limited to single prediction and bi-prediction, and a prediction image may be generated using more reference pictures. Hereinafter, when referred to as P and B slices, they refer to slices containing blocks for which inter-prediction can be used.

The slice header may include a reference (pic_parameter_set_id) to the picture parameter set PPS.

(Coded slice data)
The coded slice data defines a set of data referred to by the moving image decoding device 31 in order to decode the slice data to be processed. The slice data includes the CTU, as shown in Figure 4 (d). A CTU is a fixed-size (for example, 64x64) block that constitutes a slice, and is sometimes called a maximum coding unit (LCU: Largest Coding Unit).

(Encoded tree unit)
FIG. 4 (e) defines a set of data referred to by the moving image decoding device 31 in order to decode the CTU to be processed. CTU is the basis of coding processing by recursive quadtree division (QT (Quad Tree) division), binary tree division (BT (Binary Tree) division) or ternary tree division (TT (Ternary Tree) division). It is divided into a coding unit CU, which is a typical unit. The combination of BT division and TT division is called multi-tree division (MT (Multi Tree) division). A tree-structured node obtained by recursive quadtree division is called a coding node. The intermediate nodes of the quadtree, binary, and ternary tree are coded nodes, and the CTU itself is defined as the highest level coded node.

CT has a QT division flag (qt_split_cu_flag) indicating whether or not to perform QT division, an MT division flag (mtt_split_cu_flag) indicating the presence or absence of MT division, an MT division direction (mtt_split_cu_vertical_flag) indicating the division direction of MT division, and CT information. Includes MT split type (mtt_split_cu_binary_flag) indicating the split type of MT split. qt_split_cu_flag, mtt_split_cu_vertical_flag, mtt_split_cu_binary_flag are transmitted for each encoding node.

FIG. 5 is a diagram showing an example of CTU division. When qt_split_cu_flag is 1, the coding node is divided into 4 coding nodes (Fig. 5 (b)).

When qt_split_cu_flag is 0 and mtt_split_cu_flag is 0, the encoding node is not divided and has one CU as a node (Fig. 5 (a)). The CU is the terminal node of the encoding node and is not divided any further. CU is a basic unit of coding processing.

When mtt_split_cu_flag is 1, the coded node is MT-divided as follows. When mtt_split_cu_vertical_flag is 0 and mtt_split_cu_binary_flag is 1, the coding node is horizontally divided into two coding nodes (Fig. 5 (d)), and when mtt_split_cu_vertical_flag is 1 and mtt_split_cu_binary_flag is 1, there are two coding nodes. It is vertically divided into conversion nodes (Fig. 5 (c)). When mtt_split_cu_vertical_flag is 0 and mtt_split_cu_binary_flag is 0, the coding node is horizontally divided into 3 coding nodes (Fig. 5 (f)), and when mtt_split_cu_vertical_flag is 1 and mtt_split_cu_binary_flag is 0, the coding node is 3. It is vertically divided into two coding nodes (Fig. 5 (e)). These are shown in Fig. 5 (g).

If the CTU size is 64x64 pixels, the CU size is 64x64 pixels, 64x32 pixels, 32x64 pixels, 32x32 pixels, 64x16 pixels, 16x64 pixels, 32x16 pixels, 16x32 pixels, 16x16 pixels, 64x8 pixels, 8x64 pixels. , 32x8 pixels, 8x32 pixels, 16x8 pixels, 8x16 pixels, 8x8 pixels, 64x4 pixels, 4x64 pixels, 32x4 pixels, 4x32 pixels, 16x4 pixels, 4x16 pixels, 8x4 pixels, 4x8 pixels, and 4x4 pixels. ..

(Encoding unit)
As shown in FIG. 4 (f), a set of data referred to by the moving image decoding device 31 in order to decode the coding unit to be processed is defined. Specifically, the CU is composed of a CU header CUH, a prediction parameter, a conversion parameter, a quantization conversion coefficient, and the like. The CU header defines the prediction mode and so on.

The prediction process may be performed in CU units or in sub-CU units that are further divided CUs. If the size of the CU and the sub CU are equal, there is only one sub CU in the CU. If the CU is larger than the size of the sub CU, the CU is split into sub CUs. For example, when the CU is 8x8 and the sub CU is 4x4, the CU is divided into four sub CUs consisting of two horizontal divisions and two vertical divisions.

There are two types of prediction (prediction mode): intra prediction and inter prediction. Intra-prediction is prediction within the same picture, and inter-prediction refers to prediction processing performed between different pictures (for example, between display times).

The conversion / quantization process is performed in CU units, but the quantization conversion coefficient may be entropy-encoded in subblock units such as 4x4.

(Prediction parameter)
The prediction image is derived by the prediction parameters associated with the block. Prediction parameters include intra-prediction and inter-prediction prediction parameters.

Hereinafter, the prediction parameters of the inter-prediction will be described. The inter-prediction parameter is composed of the prediction list usage flags predFlagL0 and predFlagL1, the reference picture indexes refIdxL0 and refIdxL1, and the motion vectors mvL0 and mvL1. The prediction list usage flags predFlagL0 and predFlagL1 are flags indicating whether or not the reference picture list called the L0 list and the L1 list is used, respectively, and the reference picture list corresponding to the case where the value is 1 is used. In the present specification, when "a flag indicating whether or not it is XX" is described, it is assumed that a flag other than 0 (for example, 1) is XX, 0 is not XX, and logical negation, logical product, etc. Treat 1 as true and 0 as false (same below). However, in an actual device or method, other values can be used as true values and false values.

The syntax elements for deriving the inter-prediction parameters include, for example, affine flag affine_flag, merge flag merge_flag, merge index merge_idx, inter-prediction identifier inter_pred_idc, reference picture index refIdxLX, prediction vector index mvp_LX_idx, difference vector mvdLX, motion vector accuracy. There is a mode amvr_mode.

(Reference picture list)
The reference picture list is a list composed of reference pictures stored in the reference picture memory 306. FIG. 6 is a conceptual diagram showing an example of a reference picture and a reference picture list. In Fig. 6 (a), the rectangle is the picture, the arrow is the reference relationship of the picture, the horizontal axis is the time, I, P, B in the rectangle are the intra picture, the single prediction picture, the bi-prediction picture, and the numbers in the rectangle are decoded. Show the order. As shown in the figure, the decoding order of the pictures is I0, P1, B2, B3, B4, and the display order is I0, B3, B2, B4, P1. Figure 6 (b) shows an example of the reference picture list of picture B3 (target picture). The reference picture list is a list representing candidates for reference pictures, and one picture (slice) may have one or more reference picture lists. In the example of the figure, the target picture B3 has two reference picture lists, the L0 list RefPicList0 and the L1 list RefPicList1. In each CU, the reference picture index refIdxLX specifies which picture in the reference picture list RefPicListX (X = 0 or 1) is actually referenced. The figure is an example of refIdxL0 = 2 and refIdxL1 = 0. Note that LX is a description method used when the L0 prediction and the L1 prediction are not distinguished. Hereinafter, the parameters for the L0 list and the parameters for the L1 list are distinguished by replacing LX with L0 and L1.

(Merge prediction and AMVP prediction)
The decoding (encoding) method of the prediction parameters includes a merge prediction (merge) mode and an AMVP (Advanced Motion Vector Prediction) mode, and the merge flag merge_flag is a flag for identifying these. The merge prediction mode is a mode used to derive the prediction list usage flag predFlagLX (or inter prediction identifier inter_pred_idc), the reference picture index refIdxLX, and the motion vector mvLX from the prediction parameters of the already processed neighborhood blocks without including them in the coded data. .. The AMVP mode is a mode in which the inter-prediction identifier inter_pred_idc, the reference picture index refIdxLX, and the motion vector mvLX are included in the encoded data. The motion vector mvLX is encoded as a prediction vector index mvp_LX_idx that identifies the prediction vector mvpLX, a difference vector mvdLX, and a motion vector accuracy mode amvr_mode. In addition to the merge prediction mode, there may be an affine prediction mode identified by the affine flag affine_flag. As a form of the merge prediction mode, there may be a skip mode identified by the skip flag skip_flag. The skip mode is a mode in which the prediction parameters are derived and used by the same method as the merge mode, and the prediction error (residual image) is not included in the coded data. In other words, when the skip flag skip_flag is 1, only the skip flag skip_flag and the syntax related to the merge mode such as the merge index merge_idx are included in the target CU, and the motion vector and the like are not included in the coded data. Therefore, when the skip flag skip_flag indicates that the skip mode is applied to the target CU, the decoding of the prediction parameters other than the skip flag skip_flag is omitted.

(Motion vector)
The motion vector mvLX indicates the amount of shift between blocks on two different pictures. The prediction vector and difference vector related to the motion vector mvLX are called the prediction vector mvpLX and the difference vector mvdLX, respectively.

(Inter prediction identifier inter_pred_idc and prediction list usage flag predFlagLX)
The inter-prediction identifier inter_pred_idc is a value indicating the type and number of reference pictures, and takes any of PRED_L0, PRED_L1, and PRED_BI values. PRED_L0 and PRED_L1 indicate a simple prediction using one reference picture managed by the L0 list and the L1 list, respectively. PRED_BI indicates a bipredictive BiPred that uses two reference pictures managed by the L0 list and the L1 list.

The merge index merge_idx is an index indicating which of the prediction parameter candidates (merge candidates) derived from the processed block is used as the prediction parameter of the target block.

The relationship between the inter-prediction identifier inter_pred_idc and the prediction list usage flags predFlagL0 and predFlagL1 is as follows and can be converted to each other.

inter_pred_idc = (predFlagL1 << 1) + predFlagL0
predFlagL0 = inter_pred_idc & 1
predFlagL1 = inter_pred_idc >> 1
(Judgment of bipred biPred)
The bipred BiPred flag biPred can be derived depending on whether the two prediction list usage flags are both 1. For example, it can be derived by the following formula.

biPred = (predFlagL0 == 1 && predFlagL1 == 1)
Alternatively, the flag biPred can also be derived by whether or not the inter-prediction identifier is a value indicating that two prediction lists (reference pictures) are used. For example, it can be derived by the following formula.

biPred = (inter_pred_idc == PRED_BI)? 1: 0
(Configuration of moving image decoding device)
The configuration of the moving image decoding device 31 (FIG. 7) according to the present embodiment will be described.

The moving image decoding device 31 includes an entropy decoding unit 301, a parameter decoding unit (predicted image decoding device) 302, a loop filter 305, a reference picture memory 306, a predicted parameter memory 307, a predicted image generator (predicted image generator) 308, and a reverse. It is composed of a quantization / inverse conversion unit 311 and an addition unit 312. In addition, there is also a configuration in which the loop filter 305 is not included in the moving image decoding device 31 in accordance with the moving image coding device 11 described later.

The parameter decoding unit 302 further includes a header decoding unit 3020, a CT information decoding unit 3021, and a CU decoding unit 3022 (prediction mode decoding unit) (not shown), and the CU decoding unit 3022 further includes a TU decoding unit 3024. ing. These may be generically called a decoding module. The header decoding unit 3020 decodes the parameter set information such as VPS, SPS, and PPS, and the slice header (slice information) from the encoded data. The CT information decoding unit 3021 decodes the CT from the encoded data. The CU decoding unit 3022 decodes the CU from the encoded data. The TU decoding unit 3024 decodes the QP update information (quantization correction value) and the quantization prediction error (residual_coding) from the coded data when the TU contains a prediction error.

Further, the parameter decoding unit 302 includes an inter-prediction parameter decoding unit (prediction image generation device) 303 and an intra-prediction parameter decoding unit 304 (not shown). The prediction image generation unit 308 includes an inter-prediction image generation unit (prediction image generation device) 309 and an intra-prediction image generation unit 310.

In the following, an example in which CTU and CU are used as the processing unit will be described, but the processing is not limited to this example, and processing may be performed in sub-CU units. Alternatively, CTU and CU may be read as blocks and sub-CUs may be read as sub-blocks, and processing may be performed in units of blocks or sub-blocks.

The entropy decoding unit 301 performs entropy decoding on the coded stream Te input from the outside, and decodes each code (syntax element).

The entropy decoding unit 301 outputs the decoded code to the parameter decoding unit 302. The decoded codes are, for example, prediction mode predMode, merge flag merge_flag, merge index merge_idx, inter prediction identifier inter_pred_idc, reference picture index refIdxLX, prediction vector index mvp_LX_idx, difference vector mvdLX, motion vector accuracy mode amvr_mode and the like. The control of which code is decoded is performed based on the instruction of the parameter decoding unit 302.

(Structure of inter-prediction parameter decoding unit)
The inter-prediction parameter decoding unit 303 decodes the inter-prediction parameter with reference to the prediction parameter stored in the prediction parameter memory 307 based on the code input from the entropy decoding unit 301. Further, the inter-prediction parameter decoding unit 303 outputs the decoded inter-prediction parameter to the prediction image generation unit 308 and stores it in the prediction parameter memory 307.

FIG. 8 is a schematic view showing the configuration of the inter-prediction parameter decoding unit 303 according to the present embodiment. The inter-prediction parameter decoding unit 303 includes merge prediction unit 30374, DMVR unit 30375, sub-block prediction unit (affine prediction unit) 30372, MMVD prediction unit (motion vector derivation unit) 30376, Triangle prediction unit 30377, and AMVP prediction parameter derivation unit 3032. , The addition unit 3038 is included. The merge prediction unit 30374 includes a merge prediction parameter derivation unit 3036. The AMVP prediction parameter derivation unit 3032, the merge prediction parameter derivation unit 3036, and the affine prediction unit 30372 are means common to the moving image coding device and the moving image decoding device. Therefore, they are collectively referred to as a motion vector deriving unit (motion vector). It may be called a derivation device).

The inter-prediction parameter decoding unit 303 instructs the entropy decoding unit 301 to decode the syntax elements related to the inter-prediction, and the affine flags include_flag, the merge flag merge_flag, and the merge index merge_idx include the affine flags included in the encoded data. , Inter prediction identifier inter_pred_idc, reference picture index refIdxLX, prediction vector index mvp_LX_idx, difference vector mvdLX, motion vector precision mode amvr_mode.

When the affine flag affine_flag indicates 1, that is, the affine prediction mode, the affine prediction unit 30372 derives the inter-prediction parameter of the subblock.

When the merge flag merge_flag is 1, that is, the merge prediction mode is indicated, the merge index merge_idx is decoded and output to the merge prediction parameter derivation unit 3036.

When the merge flag merge_flag is 0, that is, indicates the AMVP prediction mode, the AMVP prediction parameters, for example, the inter prediction identifier inter_pred_idc, the reference picture index refIdxLX, the prediction vector index mvp_LX_idx, and the difference vector mvdLX are decoded. The AMVP prediction parameter derivation unit 3032 derives the prediction vector mvpLX from the prediction vector index mvp_LX_idx. In the addition unit 3038, the derived prediction vector mvpLX and the difference vector mvdLX are added to derive the motion vector mvLX.

(Affine prediction department)
The affine prediction unit 30372 derives the affine prediction parameters of the target block. In this embodiment, motion vectors (mv0_x, mv0_y) (mv1_x, mv1_y) of two control points (V0, V1) of the target block are derived as affine prediction parameters. Specifically, the motion vector of each control point may be derived by predicting from the motion vector of the adjacent block of the target block, or derived from the prediction vector derived as the motion vector of the control point and the coded data. The motion vector of each control point may be derived from the sum of the difference vectors to be obtained.

The affine prediction unit 30372 may appropriately derive the parameters used for the 4-parameter MVD affine prediction or the parameters used for the 6-parameter MVD affine prediction.

(Merge prediction)
FIG. 9A is a schematic diagram showing the configuration of the merge prediction parameter derivation unit 3036 included in the merge prediction unit 30374. The merge prediction parameter derivation unit 3036 includes a merge candidate derivation unit 30361 and a merge candidate selection unit 30362. The merge candidate is configured to include the prediction list usage flag predFlagLX, the motion vector mvLX, and the reference picture index refIdxLX, and is stored in the merge candidate list. The merge candidates stored in the merge candidate list are indexed according to a predetermined rule.

The merge candidate derivation unit 30361 derives the merge candidate by using the motion vector of the decoded adjacent block and the reference picture index refIdxLX as they are. In addition, the merge candidate derivation unit 30361 may apply the spatial merge candidate derivation process, the time merge candidate derivation process, the pairwise merge candidate derivation process, and the zero merge candidate derivation process described later.

As the space merge candidate derivation process, the merge candidate derivation unit 30361 reads the prediction parameters stored in the prediction parameter memory 307 and sets them as merge candidates according to a predetermined rule. The reference picture can be specified, for example, by all or part of adjacent blocks within a predetermined range from the target block (for example, all or a part of blocks in contact with the target block's left A1, right B1, upper right B0, lower left A0, and upper left B2, respectively. ) Are the prediction parameters. Each merge candidate is called A1, B1, B0, A0, B2.

Here, A1, B1, B0, A0, and B2 are motion information derived from the block including the following coordinates, respectively.

A1: (xCb --1, yCb + cbHeight --1)
B1: (xCb + cbWidth --1, yCb --1)
B0: (xCb + cbWidth, yCb --1)
A0: (xCb --1, yCb + cbHeight)
B2: (xCb ―― 1, yCb ―― 1)
As the time merge derivation process, the merge candidate derivation unit 30361 reads the prediction parameter of the lower right CBR of the target block or the prediction parameter of the block C in the reference image including the center coordinate from the prediction parameter memory 307 and sets it as the merge candidate Col. Merge candidate list Store in mergeCandList [].

The pairwise derivation unit derives the pairwise candidate avgK and stores it in the merge candidate list mergeCandList [].

The merge candidate derivation unit 30361 derives zero merge candidates Z0, ..., ZM in which the reference picture index refIdxLX is 0 ... M and the X and Y components of the motion vector mvLX are both 0, and stores them in the merge candidate list.

The order in which the merge candidate derivation unit 30361 or the pairwise derivation unit stores each merge candidate in the merge candidate list mergeCandList [] is, for example, spatial merge candidate (A1, B1, B0, A0, B2), time merge candidate Col, pairwise candidate. AvgK, Zero Merge candidate ZeroCandK. Reference blocks that are not available (blocks are intra-predicted, etc.) are not stored in the merge candidate list.
i = 0
if (availableFlagA1)
mergeCandList [i ++] = A1
if (availableFlagB1)
mergeCandList [i ++] = B1
if (availableFlagB0)
mergeCandList [i ++] = B0
if (availableFlagA0)
mergeCandList [i ++] = A0
if (availableFlagB2)
mergeCandList [i ++] = B2
if (availableFlagCol)
mergeCandList [i ++] = Col
if (availableFlagAvgK)
mergeCandList [i ++] = avgK
if (i <MaxNumMergeCand)
mergeCandList [i ++] = ZK
The upper left coordinates of the target block are (xCb, yCb), the width of the target block is cbWidth, and the height of the target block is cbHeight.

The merge candidate selection unit 30362 selects the merge candidate N indicated by the merge index merge_idx from the merge candidates included in the merge candidate list by the following formula.

N = mergeCandList [merge_idx]
Here, N is a label indicating a merge candidate, and takes A1, B1, B0, A0, B2, Col, AvgK, ZeroCandK, and the like. The movement information of the merge candidates indicated by the label N (mvLXN [0], mvLXN [1]) is indicated by predFlagLXN and refIdxLXN.

The merge candidate selection unit 30362 selects the motion information (mvLXN [0], mvLXN [1]), predFlagLXN, and refIdxLXN of the selected merge candidates as the inter-prediction parameters of the target block. The merge candidate selection unit 30362 stores the selected inter-prediction parameter in the prediction parameter memory 307 and outputs it to the prediction image generation unit 308.

(MMVD Prediction Unit 30373)
The MMVD prediction unit 30373 derives a motion vector by adding the difference vector mvdLX to the center vector mvdLX (motion vector of the merge candidate) derived by the merge candidate derivation unit 30361.

The MMVD prediction unit 30376 derives the motion vector mvLX [] using the merge candidate mergeCandList [] and the syntax base_candidate_idx, direction_idx, and distance_idx that decode or encode the coded data from the coded data. Furthermore, the syntax distance_list_idx for selecting the distance table may be encoded or decoded.

The MMVD prediction unit 30376 selects the center vector mvLN [] with base_candidate_idx.

N = mergeCandList [base_candidate_idx]
The MMVD prediction unit 30376 derives the base distance (mvdUnit [0], mvdUnit [1]) and the distance DistFromBaseMV.

dir_table_x [] = {8, -8, 0, 0, 6, -6, -6, 6}
dir_table_y [] = {0, 0, 8, -8, 6, -6, 6, -6}
mvdUnit [0] = dir_table_x [direction_idx]
mvdUnit [1] = dir_table_y [direction_idx]
DistFromBaseMV = DistanceTable [distance_idx]
The MMVD prediction unit 30376 derives the difference vector refineMv [].

firstMv [0] = (DistFromBaseMV << shiftMMVD) * mvdUnit [0]
firstMv [1] = (DistFromBaseMV << shiftMMVD) * mvdUnit [1]
Here, shiftMMVD is a value for adjusting the magnitude of the difference vector so as to match the accuracy MVPREC of the motion vector in the motion compensation unit 3091 (interpolation unit).

refineMvL0 [0] = firstMv [0]
refineMvL0 [1] = firstMv [1]
refineMvL1 [0] = -firstMv [0]
refineMvL1 [1] = -firstMv [1]
Finally, the MMVD prediction unit 30376 derives the motion vector of the MMVD merge candidate from the difference vector refineMvLX and the center vector mvLXN as follows.

mvL0 [0] = mvL0N [0] + refineMvL0 [0]
mvL0 [1] = mvL0N [1] + refineMvL0 [1]
mvL1 [0] = mvL1N [0] + refineMvL1 [0]
mvL1 [1] = mvL1N [1] + refineMvL1 [1]
(AMVP forecast)
FIG. 9B is a schematic diagram showing the configuration of the AMVP prediction parameter derivation unit 3032 according to the present embodiment. The AMVP prediction parameter derivation unit 3032 includes a vector candidate derivation unit 3033 and a vector candidate selection unit 3034. The vector candidate derivation unit 3033 derives the prediction vector candidate from the motion vector mvLX of the decoded adjacent block stored in the prediction parameter memory 307 based on the reference picture index refIdxLX, and stores it in the prediction vector candidate list mvpListLX [].

The vector candidate selection unit 3034 selects the motion vector mvpListLX [mvp_LX_idx] indicated by the prediction vector index mvp_LX_idx from the prediction vector candidates of the prediction vector candidate list mvpListLX [] as the prediction vector mvpLX. The vector candidate selection unit 3034 outputs the selected prediction vector mvpLX to the addition unit 3038.

The addition unit 3038 calculates the motion vector mvLX by adding the prediction vector mvpLX input from the AMVP prediction parameter derivation unit 3032 and the decoded difference vector mvdLX. The addition unit 3038 outputs the calculated motion vector mvLX to the prediction image generation unit 308 and the prediction parameter memory 307.

mvLX [0] = mvpLX [0] + mvdLX [0]
mvLX [1] = mvpLX [1] + mvdLX [1]
The motion vector accuracy mode amvr_mode is a syntax for switching the accuracy of the motion vector derived in the AMVP mode. For example, in amvr_mode = 0, 1, 2, the accuracy is switched between 1/4 pixel, 1 pixel, and 4 pixels.

When the accuracy of the motion vector is 1/16, it is derived from amvr_mode as shown below to change the motion vector difference of 1/4, 1, 4 pixel accuracy to the motion vector difference of 1/16 pixel accuracy. MvShift (= 1 << amvr_mode) may be used for inverse quantization.

mvdLX [0] = mvdLX [0] << (MvShift + 2)
mvdLX [1] = mvdLX [1] << (MvShift + 2)
Further, the parameter decoding unit 302 may derive mvdLX [] by decoding the following syntax.
・ Abs_mvd_greater0_flag
・ Abs_mvd_minus2
・ Mvd_sign_flag
To decrypt. Then, the parameter decoding unit 302 decodes the difference vector lMvd [] from the syntax by using the following equation.

lMvd [compIdx] = abs_mvd_greater0_flag [compIdx] * (abs_mvd_minus2 [compIdx]
] + 2) * (1-2 * mvd_sign_flag [compIdx])
Furthermore, the decoded difference vector lMvd [] is for translational MVD (MotionModelIdc [x] [y] ==
Set to mvdLX for 0), and set to mvdCpLX for control point MVD (MotionModelIdc [x] [y]! = 0).

if (MotionModelIdc [x] [y] == 0)
mvdLX [x0] [y0] [compIdx] = lMvd [compIdx]
else else
mvdCpLX [x0] [y0] [compIdx] = lMvd [compIdx] << 2
(DMVR)
Next, the DMVR (Decoder side Motion Vector Refinement) process performed by the DMVR unit 30375 will be described. The DMVR unit 30375 indicates that the merge flag merge_flag applies the merge prediction mode to the target CU, or the skip flag skip_flag indicates that the skip mode is applied, the merge prediction unit 30374. The motion vector mvLX of the target CU derived by is corrected by using the reference image.

Specifically, when the prediction parameter derived by the merge prediction unit 30374 is bi-prediction, the motion vector is corrected by using the prediction image derived from the motion vector corresponding to the two reference pictures. The corrected motion vector mvLX is supplied to the inter-prediction image generation unit 309.

(Triangle prediction)
Next, the Triangle prediction will be described. In Triangle prediction, the target CU is divided into two triangular prediction units with the diagonal or opposite diagonal as the boundary. The prediction image in each triangle prediction unit is derived by applying a weighting mask process to each pixel of the prediction image of the target CU (rectangular block including the triangle prediction unit) according to the pixel position. For example, a triangular image can be derived from a rectangular image by multiplying a mask in which the pixels of the triangular region in the rectangular region are 1 and the region other than the triangle is 0. Further, after the inter-prediction image is generated, the adaptive weighting process is applied to both regions sandwiching the diagonal line, and the adaptive weighting process using the two predicted images is performed to 1 of the target CU (rectangular block). Two predicted images are derived. This process is called Triangle composition process. Then, the transformation (inverse transformation) and the quantization (inverse quantization) processing are applied to the entire target CU. Note that Triangle prediction is applied only in the merge prediction mode or skip mode.

The Triangle prediction unit 30377 derives prediction parameters corresponding to the two triangular regions used for the Triangle prediction and supplies them to the inter-prediction image generation unit 309. In Triangle prediction, in order to simplify the process, a configuration that does not use bi-prediction may be used. In this case, the inter-prediction parameters for unidirectional prediction are derived in one triangular region. The derivation of the two predicted images and the composition using the predicted images are performed by the motion compensation unit 3091 and the Triangle composition unit 30952.

The loop filter 305 is a filter provided in the coding loop, which removes block distortion and ringing distortion to improve image quality. The loop filter 305 applies filters such as a deblocking filter, a sample adaptive offset (SAO), and an adaptive loop filter (ALF) to the decoded image of the CU generated by the addition unit 312.

The reference picture memory 306 stores the decoded image of the CU generated by the addition unit 312 at a predetermined position for each target picture and the target CU.

The prediction parameter memory 307 stores the prediction parameters at a predetermined position for each CTU or CU to be decoded. Specifically, the prediction parameter memory 307 stores the parameters decoded by the parameter decoding unit 302, the prediction mode predMode decoded by the entropy decoding unit 301, and the like.

The prediction mode predMode, prediction parameters, and the like are input to the prediction image generation unit 308. Further, the prediction image generation unit 308 reads the reference picture from the reference picture memory 306. The prediction image generation unit 308 generates a prediction image of a block or a subblock by using the prediction parameter and the read reference picture (reference picture block) in the prediction mode indicated by the prediction mode predMode. Here, the reference picture block is a set of pixels on the reference picture (usually called a block because it is rectangular), and is an area to be referred to for generating a predicted image.

(Inter-prediction image generation unit 309)
When the prediction mode predMode indicates the inter-prediction mode, the inter-prediction image generation unit 309 uses the inter-prediction parameter input from the inter-prediction parameter decoding unit 303 and the reference picture read out, and the inter-prediction block or sub-block prediction image To generate.

FIG. 10 is a schematic view showing the configuration of the inter-prediction image generation unit 309 included in the prediction image generation unit 308 according to the present embodiment. The inter-prediction image generation unit 309 includes a motion compensation unit (prediction image generation device) 3091 and a composition unit 3095.

(Motion compensation)
The motion compensation unit 3091 (interpolated image generation unit 3091) is based on the inter-prediction parameters (prediction list usage flag predFlagLX, reference picture index refIdxLX, motion vector mvLX) input from the inter-prediction parameter decoding unit 303. An interpolated image (motion compensation image) is generated by reading from 306 the block at the position shifted by the motion vector mvLX from the position of the target block in the reference picture RefPicLX specified by the reference picture index refIdxLX. Here, when the accuracy of the motion vector mvLX is not integer accuracy, a motion compensation image is generated by applying a filter called a motion compensation filter for generating pixels at decimal positions.

First, the motion compensation unit 3091 derives the integer position (xInt, yInt) and the phase (xFrac, yFrac) corresponding to the coordinates (x, y) in the prediction block by the following equations.

xInt = xPb + (mvLX [0] >> (log2 (MVPREC))) + x
xFrac = mvLX [0] & (MVPREC -1)
yInt = yPb + (mvLX [1] >> (log2 (MVPREC))) + y
yFrac = mvLX [1] & (MVPREC -1)
Here, (xPb, yPb) is the upper left coordinate of the bW * bH size block, x = 0… bW-1, y = 0… bH-1, and MVPREC is the accuracy of the motion vector mvLX (1 / MVPREC). Pixel accuracy) is shown. For example, MVPREC = 16.

The motion compensation unit 3091 derives a temporary image temp [] [] by performing horizontal interpolation processing on the reference picture refImg using an interpolation filter. The following Σ is the sum of k = 0..NTAP-1 with respect to k, shift1 is the normalization parameter that adjusts the range of values, offset1 = 1 << (shift1-1).

temp [x] [y] = (ΣmcFilter [xFrac] [k] * refImg [xInt + k-NTAP / 2 + 1] [yInt] + offset1) >> shift1
Subsequently, the motion compensation unit 3091 derives the interpolated image Pred [] [] by vertically interpolating the temporary image temp [] []. The following Σ is the sum of k = 0..NTAP-1 with respect to k, shift2 is the normalization parameter that adjusts the range of values, offset2 = 1 << (shift2-1).

Pred [x] [y] = (ΣmcFilter [yFrac] [k] * temp [x] [y + k-NTAP / 2 + 1] + offset2) >> shift2
The above interpolation image generation process may be represented by Interpolation (refImg, xPb, yPb, bW, bH, mvLX).

(Synthesis part)
The synthesis unit 3095 makes a prediction by referring to the interpolated image supplied from the motion compensation unit 3091, the inter-prediction parameter supplied from the inter-prediction parameter decoding unit 303, and the intra-image supplied from the intra-prediction image generation unit 310. An image is generated, and the generated predicted image is supplied to the addition unit 312.

The compositing unit 3095 includes a combined intra / inter compositing unit 30951, a Triangle compositing unit 30952, and a BDOF unit 30954.

(Combined intra / inter compositing process)
The Combined intra / inter combine unit 30951 generates a prediction image by using a unidirectional prediction image in AMVP, a prediction image in the skip mode or the merge prediction mode, and an intra prediction image in combination.

(Triangle composition process)
The Triangle compositing unit 30952 generates a prediction image using the above-mentioned Triangle prediction.

(BDOF processing)
The BDOF unit 30954 generates a predicted image by performing BDOF (Bi-directional optical flow; bi-predicted gradient change) processing. Details of the BDOF section 30954 will be described later.

(Weight prediction)
In weight prediction, a block prediction image is generated by multiplying the motion compensation image PredLX by a weighting coefficient. When one of the prediction list usage flags (predFlagL0 or predFlagL1) is 1 (single prediction) and weight prediction is not used, the motion compensation image PredLX (LX is L0 or L1) is adjusted to the number of pixel bits bitDepth. I do.

Pred [x] [y] = Clip3 (0, (1 << bitDepth) -1, (PredLX [x] [y] + offset1) >> shift1)
Here, shift1 = 14-bitDepth and offset1 = 1 << (shift1-1).
If both of the reference list usage flags (predFlagL0 and predFlagL1) are 1 (bipred BiPred) and weight prediction is not used, the motion compensation images PredL0 and PredL1 are averaged to match the number of pixel bits. Do.

Pred [x] [y] = Clip3 (0, (1 << bitDepth) -1, (PredL0 [x] [y] + PredL1 [x] [y] + offset2) >> shift2)
Here, shift2 = 15-bitDepth, offset2 = 1 << (shift2-1).

Further, in the case of simple prediction and weight prediction, the synthesis unit 3095 derives the weight prediction coefficient w0 and the offset o0 from the coded data, and performs the processing of the following equation.

Pred [x] [y] = Clip3 (0, (1 << bitDepth) -1, ((PredLX [x] [y] * w0 + 2 ^ (log2WD-1)) >> log2WD) + o0)
Here, log2WD is a variable indicating a predetermined shift amount.

Further, in the case of double prediction BiPred and weight prediction, the synthesis unit 3095 derives the weight prediction coefficients w0, w1, o0, and o1 from the coded data, and performs the processing of the following equation.

Pred [x] [y] = Clip3 (0, (1 << bitDepth) -1, (PredL0 [x] [y] * w0 + PredL1 [x] [y] * w1 + ((o0 + o1 + 1) <<log2WD))>> (log2WD + 1))
Then, the predicted image of the generated block is output to the addition unit 312.

The inverse quantization / inverse conversion unit 311 inversely quantizes the quantization conversion coefficient input from the entropy decoding unit 301 to obtain the conversion coefficient. This quantization transform coefficient is obtained by performing frequency transformation such as DCT (Discrete Cosine Transform), DST (Discrete Sine Transform), etc. on the prediction error in the coding process. It is a coefficient. The inverse quantization / inverse conversion unit 311 performs inverse frequency conversion such as inverse DCT and inverse DST on the obtained conversion coefficient, and calculates a prediction error. The inverse quantization / inverse conversion unit 311 outputs the prediction error to the addition unit 312.

The addition unit 312 adds the prediction image of the block input from the prediction image generation unit 308 and the prediction error input from the inverse quantization / inverse conversion unit 311 for each pixel to generate a decoded image of the block. The addition unit 312 stores the decoded image of the block in the reference picture memory 306, and outputs the decoded image to the loop filter 305.

(BDOF prediction)
Next, the details of the prediction (BDOF prediction) using the BDOF processing performed by the BDOF unit 30954 will be described. The BDOF unit 30954 generates a prediction image by referring to two prediction images (a first prediction image and a second prediction image) and a gradient correction term in the bi-prediction mode.

FIG. 11 is a flowchart illustrating a flow of processing for deriving a predicted image.

When the inter-prediction parameter decoding unit 303 determines that the L0 is unidirectional prediction (inter_pred_idc is 0 in S101), the motion compensation unit 3091 generates the L0 prediction image Pred L0 [x] [y] (S102). When the inter-prediction parameter decoding unit 303 determines that the L1 is unidirectional prediction (inter_pred_idc is 1 in S101), the motion compensation unit 3091 generates the L1 prediction image Pred L1 [x] [y] (S103). On the other hand, when the inter-prediction parameter decoding unit 303 determines that the mode is in the bi-prediction mode (inter_pred_idc is 2 in S101), the process continues to the following S104. In S104, the synthesis unit 3095 determines the necessity of BDOF processing by referring to the bdofFlag indicating whether or not to perform BDOF processing. When bdofFlag indicates TRUE, the BDOF unit 30954 executes BDOF processing to generate a bidirectional predicted image (S106). When bdofFlag indicates FALSE, the synthesizer 3095 generates a predicted image by normal bilateral predicted image generation (S105).

The bdofFlag indicating whether to perform BDOF processing is set to TRUE under the following conditions.

The inter-prediction parameter decoding unit 303 may derive TRUE to bdofFlag when the L0 reference image refImgL0 and the L1 reference image refImgL1 are different reference images and the two pictures are in opposite directions with respect to the target picture. .. Specifically, when the target image is currPic, bdofFlag indicates TRUE when the condition that DiffPicOrderCnt (currPic, refImgL0) * DiffPicOrderCnt (currPic, refImgL1) <0 is satisfied. Here, DiffPicOrderCnt () is a function that derives the difference between the POCs (Picture Order Count: picture display order) of two images as follows.

DiffPicOrderCnt (picA, picB) = PicOrderCnt (picA)-PicOrderCnt (picB)
As a condition that bdofFlag indicates TRUE, a condition that the target block is not a subblock prediction (affine prediction) may be added.

Further, as a condition that bdofFlag indicates TRUE, a condition that neither L0 prediction nor L1 prediction performs weighted prediction may be added in the weighted prediction. Specifically, luma_weight_l0_flag [, which indicates whether or not the luminance weighting coefficient w0 and the offset o0 exist in the L0 prediction picture.
If both refIdxL0] and luma_weight_l1_flag [refIdxL1], which indicates whether or not the luminance weighting coefficient w1 and offset o1 exist in the L1 predicted picture, are FALSE, the condition is that bdofFlag indicates TRUE.

The content of the specific processing performed by the BDOF unit 30954 when the bdofFlag is TRUE will be described with reference to FIG. The BDOF unit 30954 includes an L0, L1 prediction image generation unit 309541, a flag setting unit 309542, a gradient image generation unit 309543, a correlation parameter calculation unit 309544, a motion compensation correction value derivation unit 309545, and a bidirectional prediction image generation unit. It is equipped with 309546. The BDOF unit 30954 generates a prediction image from the interpolated image received from the motion compensation unit 3091 and the inter-prediction parameter received from the inter-prediction parameter decoding unit 303, and outputs the generated prediction image to the addition unit 312. The process of deriving the motion compensation correction value bdofOffset (motion compensation correction image) from the gradient image and modifying and deriving the predicted images of PredL0 and PredL1 is called a bidirectional gradient change process.

First, the L0, L1 prediction image generation unit 309541 generates L0, L1 prediction images used for BDOF processing. Here, the CU is divided into sub-blocks. As a result, parallel processing in units of subblocks is possible, and the amount of memory required for one processing can be reduced.

Specifically, the basic size of the subblock may be 16x16. For example, when the size of the CU is cbWidth and cbHeight, the number of horizontal subblocks numSbX and the number of vertical subblocks numSbY in the CU, the subblock sizes sbWidth and sbHeight are derived as follows.

numSbX = (cbWidth> 16)? (CbWidth >> 4): 1
numSbY = (cbHeight> 16)? (CbHeight >> 4): 1
sbWidth = cbWidth / numSbX
sbHeight = cbHeight / numSbY
Next, BDOF processing is performed based on the L0 and L1 predicted images for each subblock shown in FIG. 14, but in order to obtain the gradient, interpolated image information for one pixel around the subblock is additionally required. And. For this interpolated image information, in the gradient image generation described later, nearby pixels are used instead of a normal interpolation filter. In other cases, it is a padding area in which surrounding pixels are copied, as in the case of the outside of the picture. The unit of BDOF processing is 4x4 pixels less than or equal to the subblock unit, and the processing itself is performed using 6x6 pixels including one peripheral pixel.

In the flag setting unit 309542, set the value of the flag sbBdofFlag indicating whether or not to perform BDOF processing in units of subblocks and the value of the flag bdofUtilizationFlag [xIdx] [yIdx] indicating whether or not to perform BDOF processing in units of 4x4 pixels. Do. Here, let the number of pixels of the width and height of the subblock be sbWidth and sbHeight. xIdx is the horizontal address of the 4x4 pixel block, which takes a value from 0 to (sbWidth >> 2) -1, and yIdx is a value from 0 to (sbHeight >> 2) -1, 4x4. The vertical address of the pixel block. For sbBdofFlag and bdofUtilizationFlag [xIdx] [yIdx], BDOF processing is performed in the case of TRUE, and bidirectional prediction processing is performed in the case of FALSE.

First, the threshold value sbDiffThres for each subblock, the threshold value bdofBlkDiffThres for each 4x4 pixel block, and the sum of the absolute values of the differences for each subblock sbSumDiff are derived as follows.

sbDiffThres = 4 * sbWidth * sbHeight
bdofBlkDiffThres = 128
In the present embodiment, since sbDiffThres is 4 per pixel and bdofBlkDiffThres is 128 = 8 * 4 * 4, a value of 8 per pixel is set as the threshold value, but other values may be used. For example, double the values, sbDiffThres = 8 * sbWidth * sbHeight, bdofBlkDiffThres = 256. Further, by setting sbDiffThres = 0, switching in units of subblocks may be turned off, and by setting bdofBlkDiffThres = 0, switching in units of 4x4 pixel blocks may be turned off.

First, set the value of sbSumDiff as follows.

sbSumDiff = 0
Then, loop the loop of xIdx = 0 .. (sbWidth >> 2) -1 and yIdx = 0 .. (sbHeight >> 2) -1 for each 4x4 pixel block, and the absolute difference value in 4x4 pixel units. The sum bdofBlkSumDiff and bdofUtilizationFlag [xIdx] [yIdx] are derived as follows.

bdofBlkSumDiff
= sum4 (Abs ((PredL0 [(xIdx << 2) + 1 + i] [(yIdx << 2) + 1 + j] >> shift4)
? (PredL1 [(xIdx << 2) + 1 + i] [(yIdx << 2) + 1 + j] >> shift4))) (Equation BDOF-1)
shift4 = Max (InternalBitDepth-4, bitDepth + InternalBitDepth-16)
bdofUtilizationFlag [xIdx] [yIdx] = (bdofBlkSumDiff> = bdofBlkDiffThres)
sbSumDiff + = bdofBlkSumDiff
That is, the sum of the absolute values of the differences between the value obtained by shifting PredL0 by shift4 and the value obtained by shifting PredL1 by shift4 is derived. In (Equation BDOF-1), (x, y) = ((xIdx << 2) + 1 + i,
Instead of yIdx << 2) + 1 + j), the value (hx, vy) obtained by further clipping (x, y) with the size of CU (nCbW, nCbH) may be used. In this case, the pixels that exceed the boundary are derived by padding.

hx = Clip3 (1, nCbW, x)
vy = Clip3 (1, nCbH, y)
Here, sum4 () is a function that calculates the sum of 4x4 pixel blocks with the arguments i = 0.3 and j = 0.3, and shift4 is the same as shift4 defined by the correlation parameter calculation unit 309544 described later. It shall be. Note that InternalBitDepth is a parameter of calculation accuracy in the BDOF section, and is a constant value independent of the input pixel bit length bitDepth, and is a value of 7 or more and 12 or less. For example, when InternalBitDepth = 8, shift4 becomes shift4 = Max (4, bitDepth-8).

When using the same interpolation filter as HEVC, the values of PredL0 and PredL1 have a calculation accuracy of 14 bits in the range of bitDepth of 8 to 12 bits, and when InternalBitDepth = 8, shift4 = Max (4, bitDepth-8). ) = 4, and the absolute value sum of the differences after shifting PredL0 and PredL1 shown in (Equation BDOF-1) to the right with shift4 is calculated by calculating the absolute difference sum with a precision of 10 bits regardless of bitDepth. Will be there.

In the prior art literature, bdofBlkDiff directly calculated the sum of the absolute differences between PredL0 and PredL1 without right-shifting. However, in the present embodiment, it is the same as the calculation of the difference of theta [x] [y] (Equation BDOF-2) calculated by the correlation parameter calculation unit 309544 of the BDOF unit 30954 described later, and the flag setting unit 309542 is used. The processing can be shared between the threshold value determination and the derivation of the predicted image of the BDOF unit 30954. As a result, in the prior art document, the calculation of the flag setting unit 309542 simply required an additional calculation amount, but in the present embodiment, since the difference calculation can be shared, the additional part is the sum of absolute values. Since only the required part is required, the amount of calculation can be significantly reduced.

bdofUtilizationFlag [xIdx] [yIdx] is set to TRUE if bdofBlkSumDiff is bdofBlkDiffThres or higher, and FALSE otherwise.

The value of sbSumDiff is the total value of bdofBlkSumDiff.

Finally, sbBdofFlag is set to FALSE if sbSumDiff is less than sbDiffThres, otherwise set to TRUE.

Since the difference calculation is shared, the flag setting unit 309542 can set the values of sbBdofFlag and bdofUtilizationFlag [xIdx] [yIdx] with a smaller amount of processing by such a configuration.

As another embodiment of the flag setting unit 309542, bdofBlkSumDiff is calculated by the following equation.

bdofBlkSumDiff
= sum42 (Abs ((PredL0 [(xIdx << 2) + 1 + i] [(yIdx << 2) + 1 + 2 * j] >> shift4)
? (PredL1 [(xIdx << 2) + 1 + i] [(yIdx << 2) + 1 + 2 * j] >> shift4)))
Here, sum42 () is a function that calculates the sum of 4x2 pixel blocks with the arguments i = 0.3 and j = 0.1. bdofBlkSumDiff may be the sum of the absolute values of the differences of 4x2 pixels with one line skipped. In this case, sbDiffThres and bdofBlkDiffThres are set to use half the values of the above-described embodiment as follows.

sbDiffThres = 2 * sbWidth * sbHeight
bdofBlkDiffThres = 64
With such a configuration, the amount of calculation of bdofBlkSumDiff can be halved. Since it is not an operation that directly affects the prediction image generation, there is almost no performance degradation due to processing reduction.

FIG. 13 is a probe chart illustrating a process by which the BDOF unit 30954 generates a predicted image. First, in the flag setting (S201), the values of the flag sbBdofFlag indicating whether or not to perform BDOF processing in units of subblocks and the flag bdofUtilizationFlag [xIdx] [yIdx] indicating whether or not to perform BDOF processing in units of 4x4 pixels. Set. Next, the determination of sbBdofFlag (S202) is performed, if it is FALSE, the subblock unit bidirectional prediction image generation (S203) is performed, and if it is TRUE, the subblock unit BDOF processing (S204)-(S210) is performed. Loop1 ((S204) to (S210)) is a loop of addresses in the vertical direction, and Loop2 ((S205) to (S209)) is a loop of addresses in the horizontal direction. bdofUtilizationFlag [xIdx] [yIdx] is determined (S206), if it is FALSE, 4x4 pixel unit bidirectional prediction image generation (S207) is performed, and if TRUE, 4x4 pixel unit BDOF processing (S208) is performed.

In this flow chart, it is determined whether or not BDOF processing is performed in two stages of a subblock unit and a 4x4 pixel block unit, but it may be realized only in the subblock unit or only in the 4x4 pixel block unit.

The gradient image generation unit 309543 generates a gradient image. In the optical flow, it is assumed that the pixel value at each point does not change, only the position changes. This is the change of the pixel value I in the horizontal direction (horizontal gradient value lx) and the change Vx of its position, and the change of the pixel value I in the vertical direction (vertical gradient value ly) and the change Vy of its position, and the pixel value I. It can be expressed as follows using the time change lt.

lx * Vx + ly * Vy + lt = 0
Hereafter, the change in position (Vx, Vy) is called the correction weight vector (u, v).

Specifically, the gradient image generation unit 309543 derives the gradient images lx0, ly0, lx1, and ly1 from the following equations. lx0 and lx1 show the slope along the horizontal direction, and ly0 and ly1 show the slope along the vertical direction.

Specifically, the gradient image generation unit 309543 derives the gradient images lx0, ly0, lx1, and ly1 as follows.

lx0 [x] [y] = (PredL0 [x + 1] [y]-PredL0 [x-1] [y]) >> shift0 (Equation BDOF-3)
ly0 [x] [y] = (PredL0 [x] [y + 1]-PredL0 [x] [y-1]) >> shift0
lx1 [x] [y] = (PredL1 [x + 1] [y]-PredL1 [x-1] [y]) >> shift0
ly1 [x] [y] = (PredL1 [x] [y + 1]-PredL1 [x] [y-1]) >> shift0
Here, shift0 = 14-InternalBitDepth.

As another method for deriving the gradient images lx0, ly0, lx1, and ly1, the following equation may be set.

lx0 [x] [y] = (PredL0 [x + 1] [y] >> shift0)-(PredL0 [x-1] [y] >> shift0) (Equation BDOF-4)
ly0 [x] [y] = (PredL0 [x] [y + 1] >> shift0)-(PredL0 [x] [y-1] >> shift0)
lx1 [x] [y] = (PredL1 [x + 1] [y] >> shift0)-(PredL1 [x-1] [y] >> shift0)
ly1 [x] [y] = (PredL1 [x] [y + 1] >> shift0)-(PredL1 [x] [y-1] >> shift0)
In the case of (Equation BDOF-3), if the range of the minimum and maximum values of PredL0 and PredL1 is 16 bits, the difference is 17 bits, so 32-bit operation is required, but (Equation BDOF-4) In the case of, since the right shift is performed first, all operations can be executed by 16-bit operations, so there is an advantage that parallel operation instructions are easy to use.

In either case, when using the same interpolation filter as HEVC, the values of PredL0 and PredL1 have a calculation accuracy of 14 bits if bitDepth is in the range of 8 to 12 bits, and the range of minimum and maximum values is. It is 16 bits. If bitDepth is greater than 12, the calculation accuracy is (bitDepth + 2) bits, and the range between the minimum and maximum values is (bitDepth + 4) bits. In this embodiment, shift 0, which is a value corresponding to Internal BitDepth, is shifted to the right. Therefore, the calculation accuracy of the gradient images lx0, ly0, lx1, and ly1 is (InternalBitDepth + 1) bits when BitDedepth is 8 or more and 12 or less, and (bitDepth + InternalBitDepth-11) when bitDepth is 13 or more. ..

Next, the correlation parameter calculation unit 309544 derives the sum of gradient products s1, s2, s3, s5, and s6 for each block of 4x4 pixels in the subblock. Here, s1, s2, s3, s5, s6 are calculated from the sum of the pixels of the block of 6x6 pixels by further using one pixel around the block.

s1 = sum6 (phiX [x] [y] * phiX [x] [y])
s2 = sum6 (phiX [x] [y] * phiY [x] [y])
s3 = sum6 (-theta [x] [y] * phiX [x] [y])
s5 = sum6 (phiY [x] [y] * phiY [x] [y])
s6 = sum6 (-theta [x] [y] * phiY [x] [y])
Here, sum (a) represents the sum of a with respect to the coordinates (x, y) in the block of 6x6 pixels.

theta [x] [y] =-(PredL1 [x] [y] >> shift4) + (PredL0 [x] [y] >> shift4) (Equation BDOF-2)
phiX [x] [y] = (lx1 [x] [y] + lx0 [x] [y]) >> shift5
phiY [x] [y] = (ly1 [x] [y] + ly0 [x] [y]) >> shift5
That is, theta [x] [y] is derived from the difference between the value obtained by shifting PredL0 [x] [y] by shift4 and the value obtained by shifting PredL1 [x] [y] by shift4. This is the same as the difference value calculated in (Equation BDOF-1).
Here, shift4 and shift5 are derived as follows.

shift4 = Max (InternalBitDepth-4, bitDept + InternalBitDepth-16)
shift5 = Max (InternalBitDepth-7, bitDepth + InternalBitDepth-19)
In (Equation BDOF-2), the value (hx, vy) clipped by the size of CU (nCbW, nCbH) may be used instead of (x, y). In this case, the pixels that exceed the boundary are derived by padding. Further, x and y may be in the range of x = xSb-1..xSb + 4, y = ySb-1..ySb + 4, respectively.

xSb = (xIdx << 2) +1, ySb = (yIdx << 2) +1
hx = Clip3 (1, nCbW, x)
vy = Clip3 (1, nCbH, y)
At this time, the calculation accuracy of the value of theta is always (19-InternalBitDepth) bits when bitDepth is 8 or more. Also, if the bitDepth of the image is 8 or more, the calculation accuracy of phiX and phiY is always 9 bits. Therefore, the calculation accuracy of s1, s2, and s5, which is the total of 6x6 pixel blocks, is about 23 bits regardless of bitDepth. Similarly, the calculation accuracy of s3 and s6, which is the total of 6x6 pixel blocks, is about (33-InternalBitDepth) bits. The minimum and maximum values of PredL0 and PredL1 are in the 16-bit range when bitDepth is 8 or more and 12 or less, and in the (bitDepth + 4) bit range when bitDepth is 13 bits or more. realizable.

More specifically, when InternalBitDepth = 8, it is realized by the following formula.

shift0 = 6
shift4 = Max (4, bitDepth-8)
shift5 = Max (1, bitDepth-11)
When InternalBitDepth = 7, it is realized by the following formula.

shift0 = 7
shift4 = Max (3, bitDepth-9)
shift5 = Max (0, bitDepth-12)
As another configuration of the correlation parameter calculation unit 309544, the sum of gradient products s1, s2, s3, s5, s6 may be obtained by a block of 4x4 pixels instead of a block of 6x6 pixels. Since it is a block of 4x4 = 16 pixels, the number of operation bits required to calculate sum is (Ceil (log2 (36))-Ceil (log2 (16))) = 2 bits less than the total of 6x6 = 36 pixels. I'm sorry.

shift4 = Max (InternalBitDepth-5, bitDept + InternalBitDepth-15)
shift5 = Max (InternalBitDepth-8, bitDepth + InternalBitDepth-18)
Therefore, even if each value is 1 bit smaller as in the above equation, it can be realized by 32-bit integer operation. However, in this case, the value of InternalBitDepth shall be 8 or more and 12 or less. In addition, the amount of calculation of the sum of gradient products can be reduced. As shown in FIG. 15, since the unit of BDOF processing and the reading area match, unlike the case of FIG. 14, the padding area for one pixel around the target subblock becomes unnecessary.

Next, the motion compensation correction value deriving unit 309545 derives a correction weight vector (u, v) in units of 4x4 pixels by using the derived gradient product sum s1, s2, s3, s5, s6.

u = (s3 << 3) >> floor (log2 (s1))
v = ((s6 << 3)-((((u * s2m) << 12) + u * s2s) >> 1)) >> floor (log2 (s5))
Here, s2m = s2 >> 12, s2s = s2 & ((1 << 12) -1).

The range of u and v may be further limited by using a clip as follows.

u = s1> 0? Clip3 (-th, th,-(s3 << 3) >> floor (log2 (s1))): 0
v = s5> 0? Clip3 (-th, th, ((s6 << 3)-((((u * s2m) << 12) + u * s2s) >> 1))) >> floor (log2 (s5) ))): 0
Here, th is expressed by the following equation.

th = Max (2, 1 << (13-InternalBitDepth))
Since th is a value independent of bitDepth, the pixel-by-pixel correction weight vector (u, v) is clipped by the value related to InternalBitDepth. Regardless of the pixel bit length bitDepth, for example, if InternalBitDepth = 8, then th = 1 << (13-8) = 32. If InternalBitDepth = 7, then th = 1 << (13-7) = 64.

At this time, since the correction weight vector (u, v) for each pixel can be considered as a value related to the accuracy of the motion vector and the quantization width, a threshold for limiting the correction weight vector (u, v). The value th may be expressed by a function of the quantization width Qp as shown in the following equation.

th0 = Max (1, 1 << (12-InternalBitDepth))
th = th0 + floor ((Qp-32) / 6)
Note that the sum of gradient products s3 and s6 may be derived by the following equation without performing the left 3-bit shift.

u = s3 >> floor (log2 (s1))
v = (s6-((((u * s2m) << 12) + u * s2s) >> 1)) >> floor (log2 (s5))
However, shift4 is derived by the following formula.

shift4 = Max (InternalBitDepth-7, bitDepth + InternalBitDepth-19)
In this case, it is not necessary to change shift0 and shift5. Specifically, when InternalBitDepth = 8, shift4 is derived by the following equation.

shift4 = Max (1, bitDepth-11)
The motion compensation correction value deriving unit 309545 derives the motion compensation correction value bdofOffset using the correction weight vector (u, v) in units of 4x4 pixels and the gradient images lx0, ly0, lx1, and ly1.

bdofOffset [x] [y] = ((lx1 [x] [y] -lx0 [x] [y]) * u + (ly1 [x] [y] -ly0 [x] [y]) * v + 1) >> 1
Alternatively, the bdofOffset may be derived as follows using a round function.

bdofOffset [x] [y] = Round (((lx1 [x] [y] -lx0 [x] [y]) * u) >> 1) + Round (((ly1 [x] [y] -ly0 [ x] [y]) * v) >> 1)
Alternatively, by devising the shift0 value of the right shift value of the gradient images lx0, ly0, lx1, and ly1, it can be derived without using the right shift or the round function as follows.

bdofOffset [x] [y] = (lx1 [x] [y] -lx0 [x] [y]) * u + (ly1 [x] [y]-ly0 [x] [y]) * v
shift0 = 15-InternalBitDepth
shift5 = Max (InternalBitDepth-8, bitDepth + InternalBitDepth-20)
In this case, the selection range of InternalBitDepth is 8 or more and 12 or less, and shift4 does not need to be changed. Specifically, in the case of InternalBitDepth = 8, the following formula is obtained.

shift0 = 7
shift5 = Max (0, bitDepth-12)
The bidirectional prediction image generation unit 309546 derives the pixel value Pred of the prediction image of 4x4 pixels by the following equation using the above parameters.

Pred [x] [y] = Clip3 (0, (1 << bitDepth) -1, (PredL0 [x] [y] + PredL1 [x] [y] + bdofOffset [x] [y] + offset2) >> shift2)
Here, shift2 = Max (3,15-bitDepth), offset2 = 1 << (shift2-1).

With the above configuration, it is possible to reduce the amount of calculation for setting a flag indicating whether or not to perform BDOF processing in units of subblocks and a flag indicating whether or not to perform BDOF processing in units of 4x4 pixels. it can.

(Configuration of moving image encoding device)
Next, the configuration of the moving image coding device 11 according to the present embodiment will be described. FIG. 16 is a block diagram showing the configuration of the moving image coding device 11 according to the present embodiment. The moving image coding device 11 includes a prediction image generation unit 101, a subtraction unit 102, a conversion / quantization unit 103, an inverse quantization / inverse conversion unit 105, an addition unit 106, a loop filter 107, and a prediction parameter memory (prediction parameter storage unit). , Frame memory) 108, reference picture memory (reference image storage unit, frame memory) 109, coding parameter determination unit 110, parameter coding unit 111, and entropy coding unit 104.

The prediction image generation unit 101 generates a prediction image for each CU, which is a region in which each picture of the image T is divided. The prediction image generation unit 101 has the same operation as the prediction image generation unit 308 described above, and the description thereof will be omitted.

The subtraction unit 102 subtracts the pixel value of the predicted image of the block input from the prediction image generation unit 101 from the pixel value of the image T to generate a prediction error. The subtraction unit 102 outputs the prediction error to the conversion / quantization unit 103.

The conversion / quantization unit 103 calculates the conversion coefficient by frequency conversion for the prediction error input from the subtraction unit 102, and derives the quantization conversion coefficient by quantization. The conversion / quantization unit 103 outputs the quantization conversion coefficient to the entropy coding unit 104 and the inverse quantization / inverse conversion unit 105.

The inverse quantization / inverse conversion unit 105 is the same as the inverse quantization / inverse conversion unit 311 (FIG. 7) in the moving image decoding device 31, and the description thereof will be omitted. The calculated prediction error is output to the addition unit 106.

A quantization conversion coefficient is input to the entropy coding unit 104 from the conversion / quantization unit 103, and a coding parameter is input from the parameter coding unit 111. Coding parameters include, for example, codes such as reference picture index refIdxLX, prediction vector index mvp_LX_idx, difference vector mvdLX, motion vector accuracy mode amvr_mode, prediction mode predMode, and merge index merge_idx.

The entropy coding unit 104 entropy-encodes the division information, the prediction parameters, the quantization conversion coefficient, and the like to generate a coded stream Te and outputs it.

The parameter coding unit 111 includes a header coding unit 1110 (not shown), a CT information coding unit 1111, a CU coding unit 1112 (prediction mode coding unit), an inter prediction parameter coding unit 112, and an intra prediction parameter coding unit 112. It has 113. The CU coding unit 1112 further includes a TU coding unit 1114.

The outline operation of each module will be described below. The parameter coding unit 111 performs parameter coding processing such as header information, division information, prediction information, and quantization conversion coefficient.

The CT information coding unit 1111 encodes QT, MT (BT, TT) division information and the like from the coded data.

The CU coding unit 1112 encodes CU information, prediction information, TU split flag split_transform_flag, CU residual flags cbf_cb, cbf_cr, cbf_luma and the like.

The TU coding unit 1114 encodes the QP update information (quantization correction value) and the quantization prediction error (residual_coding) when the TU includes a prediction error.

The CT information coding unit 1111 and the CU coding unit 1112 include inter-prediction parameters (prediction mode predMode, merge flag merge_flag, merge index merge_idx, inter-prediction identifier inter_pred_idc, reference picture index refIdxLX, prediction vector index mvp_LX_idx, difference vector mvdLX). The vector elements such as the intra prediction parameter and the quantization conversion coefficient are supplied to the entropy coding unit 104.

(Structure of inter-prediction parameter coding unit)
The parameter coding unit 112 derives an inter-prediction parameter based on the prediction parameter input from the coding parameter determination unit 110. The parameter coding unit 112 includes a configuration that is partially the same as the configuration in which the inter-prediction parameter decoding unit 303 derives the inter-prediction parameter.

The configuration of the prediction parameter coding unit 112 will be described. As shown in FIG. 17, parameter coding control unit 1121, merge prediction unit 30374, subblock prediction unit (affin prediction unit) 30372, DMVR unit 30375, MMVD prediction unit 30376, Triangle prediction unit 30377, AMVP prediction parameter derivation unit 3032, It is configured to include a subtraction unit 1123. The merge prediction unit 30374 includes a merge prediction parameter derivation unit 3036. The parameter coding control unit 1121 includes a merge index derivation unit 11211 and a vector candidate index derivation unit 11212. Further, the parameter coding control unit 1121 derives merge_idx, affine_flag, base_candidate_idx, distance_idx, direction_idx, etc. in the merge index derivation unit 11211, and derives mvpLX, etc. in the vector candidate index derivation unit 11212. The merge prediction parameter derivation unit 3036, the AMVP prediction parameter derivation unit 3032, the affine prediction unit 30372, the MMVD prediction unit 30376, and the Triangle prediction unit 30377 may be collectively referred to as a motion vector derivation unit (motion vector derivation device). The parameter coding unit 112 outputs the motion vector (mvLX, subMvLX), the reference picture index refIdxLX, the inter-prediction identifier inter_pred_idc, or the information indicating these to the prediction image generation unit 101. Further, the parameter coding unit 112 outputs merge_flag, skip_flag, merge_idx, inter_pred_idc, refIdxLX, mvp_lX_idx, mvdLX, amvr_mode, and affine_flag to the entropy coding unit 104.

The merge index derivation unit 11211 derives the merge index merge_idx and outputs it to the merge prediction parameter derivation unit 3036 (merge prediction unit). The vector candidate index derivation unit 11212 derives the prediction vector index mvp_lX_idx.

The merge prediction parameter derivation unit 3036 derives the inter prediction parameter based on the merge index merge_idx.

The AMVP prediction parameter derivation unit 3032 derives the prediction vector mvpLX based on the motion vector mvLX. The AMVP prediction parameter derivation unit 3032 outputs the prediction vector mvpLX to the subtraction unit 1123. The reference picture index refIdxLX and the prediction vector index mvp_lX_idx are output to the entropy encoding unit 104.

The affine prediction unit 30372 derives the inter-prediction parameter (affine prediction parameter) of the subblock.

The subtraction unit 1123 generates the difference vector mvdLX by subtracting the prediction vector mvpLX, which is the output of the AMVP prediction parameter derivation unit 3032, from the motion vector mvLX input from the coding parameter determination unit 110. The difference vector mvdLX is output to the entropy encoding unit 104.

The addition unit 106 generates a decoded image by adding the pixel value of the prediction image of the block input from the prediction image generation unit 101 and the prediction error input from the inverse quantization / inverse conversion unit 105 for each pixel. The addition unit 106 stores the generated decoded image in the reference picture memory 109.

The loop filter 107 applies a deblocking filter, SAO, and ALF to the decoded image generated by the addition unit 106. The loop filter 107 does not necessarily have to include the above three types of filters, and may have, for example, a configuration of only a deblocking filter.

The prediction parameter memory 108 stores the prediction parameters generated by the coding parameter determination unit 110 at positions predetermined for each target picture and CU.

The reference picture memory 109 stores the decoded image generated by the loop filter 107 at a predetermined position for each target picture and CU.

The coding parameter determination unit 110 selects one set from the plurality of sets of coding parameters. The coding parameter is the above-mentioned QT, BT or TT division information, prediction parameter, or a parameter to be coded generated in connection with these. The prediction image generation unit 101 generates a prediction image using these coding parameters.

The coding parameter determination unit 110 calculates an RD cost value indicating the magnitude of the amount of information and the coding error for each of the plurality of sets. The coding parameter determination unit 110 selects the set of coding parameters that minimizes the calculated cost value. As a result, the entropy coding unit 104 outputs the selected set of coding parameters as the coding stream Te. The coding parameter determination unit 110 stores the determined coding parameter in the prediction parameter memory 108.

A part of the moving image coding device 11 and the moving image decoding device 31 in the above-described embodiment, for example, the entropy decoding unit 301, the parameter decoding unit 302, the loop filter 305, the predicted image generation unit 308, and the inverse quantization / reverse. Conversion unit 311, addition unit 312, prediction image generation unit 101, subtraction unit 102, conversion / quantization unit 103, entropy coding unit 104, inverse quantization / inverse conversion unit 105, loop filter 107, coding parameter determination unit 110 , The parameter coding unit 111 may be realized by a computer. In that case, the program for realizing this control function may be recorded on a computer-readable recording medium, and the program recorded on the recording medium may be read by the computer system and executed. The "computer system" referred to here is a computer system built into either the moving image coding device 11 or the moving image decoding device 31, and includes hardware such as an OS and peripheral devices. Further, the "computer-readable recording medium" refers to a portable medium such as a flexible disk, a magneto-optical disk, a ROM, or a CD-ROM, or a storage device such as a hard disk built in a computer system. Furthermore, a "computer-readable recording medium" is a medium that dynamically holds a program for a short period of time, such as a communication line when a program is transmitted via a network such as the Internet or a communication line such as a telephone line. In that case, a program may be held for a certain period of time, such as a volatile memory inside a computer system serving as a server or a client. Further, the above-mentioned program may be for realizing a part of the above-mentioned functions, and may further realize the above-mentioned functions in combination with a program already recorded in the computer system.

Further, a part or all of the moving image coding device 11 and the moving image decoding device 31 in the above-described embodiment may be realized as an integrated circuit such as an LSI (Large Scale Integration). Each functional block of the moving image coding device 11 and the moving image decoding device 31 may be made into a processor individually, or a part or all of them may be integrated into a processor. Further, the method of making an integrated circuit is not limited to LSI, and may be realized by a dedicated circuit or a general-purpose processor. Further, when an integrated circuit technology that replaces an LSI appears due to advances in semiconductor technology, an integrated circuit based on this technology may be used.

Although one embodiment of the present invention has been described in detail with reference to the drawings, the specific configuration is not limited to the above, and various design changes and the like are made without departing from the gist of the present invention. It is possible to do.

[Application example]
The moving image coding device 11 and the moving image decoding device 31 described above can be mounted on and used in various devices for transmitting, receiving, recording, and reproducing moving images. The moving image may be a natural moving image captured by a camera or the like, or an artificial moving image (including CG and GUI) generated by a computer or the like.

First, it will be described with reference to FIG. 2 that the moving image coding device 11 and the moving image decoding device 31 described above can be used for transmitting and receiving moving images.

FIG. 2A is a block diagram showing the configuration of the transmission device PROD_A equipped with the moving image coding device 11. As shown in the figure, the transmission device PROD_A has a coding unit PROD_A1 that obtains coded data by encoding a moving image, and a modulation signal by modulating a carrier with the coded data obtained by the coding unit PROD_A1. It includes a modulation unit PROD_A2 to obtain and a transmission unit PROD_A3 to transmit the modulation signal obtained by the modulation unit PROD_A2. The moving image coding device 11 described above is used as the coding unit PROD_A1.

The transmitter PROD_A has a camera PROD_A4 for capturing a moving image, a recording medium PROD_A5 for recording a moving image, an input terminal PROD_A6 for inputting a moving image from the outside, and a moving image as a source of the moving image to be input to the coding unit PROD_A1. , An image processing unit A7 for generating or processing an image may be further provided. In the figure, the configuration in which the transmitter PROD_A has all of these is illustrated, but some of them may be omitted.

The recording medium PROD_A5 may be a recording of an unencoded moving image, or a moving image encoded by a recording coding method different from the transmission coding method. It may be a thing. In the latter case, a decoding unit (not shown) that decodes the coded data read from the recording medium PROD_A5 according to the recording coding method may be interposed between the recording medium PROD_A5 and the coding unit PROD_A1.

FIG. 2B is a block diagram showing the configuration of the receiving device PROD_B equipped with the moving image decoding device 31. As shown in the figure, the receiving device PROD_B is obtained by a receiving unit PROD_B1 that receives a modulated signal, a demodulating unit PROD_B2 that obtains encoded data by demodulating the modulated signal received by the receiving unit PROD_B1, and a demodulating unit PROD_B2. It includes a decoding unit PROD_B3 that obtains a moving image by decoding the coded data. The moving image decoding device 31 described above is used as the decoding unit PROD_B3.

The receiving device PROD_B is a display PROD_B4 for displaying the moving image, a recording medium PROD_B5 for recording the moving image, and an output terminal for outputting the moving image to the outside as a supply destination of the moving image output by the decoding unit PROD_B3. It may also have PROD_B6. In the figure, the configuration in which the receiving device PROD_B is provided with all of these is illustrated, but some of them may be omitted.

The recording medium PROD_B5 may be used for recording an unencoded moving image, or may be encoded by a recording encoding method different from the transmission coding method. You may. In the latter case, a coding unit (not shown) that encodes the moving image acquired from the decoding unit PROD_B3 according to the recording coding method may be interposed between the decoding unit PROD_B3 and the recording medium PROD_B5.

The transmission medium for transmitting the modulated signal may be wireless or wired. Further, the transmission mode for transmitting the modulated signal may be broadcasting (here, a transmission mode in which the destination is not specified in advance) or communication (here, transmission in which the destination is specified in advance). Refers to an aspect). That is, the transmission of the modulated signal may be realized by any of wireless broadcasting, wired broadcasting, wireless communication, and wired communication.

For example, a broadcasting station (broadcasting equipment, etc.) / receiving station (television receiver, etc.) of terrestrial digital broadcasting is an example of a transmitting device PROD_A / receiving device PROD_B that transmits and receives modulated signals by radio broadcasting. Further, a broadcasting station (broadcasting equipment, etc.) / receiving station (television receiver, etc.) of cable television broadcasting is an example of a transmitting device PROD_A / receiving device PROD_B that transmits and receives modulated signals by wired broadcasting.

In addition, servers (workstations, etc.) / clients (television receivers, personal computers, smartphones, etc.) such as VOD (Video On Demand) services and video sharing services using the Internet are transmitters that send and receive modulated signals via communication. This is an example of PROD_A / receiver PROD_B (usually, in LAN, either wireless or wired is used as a transmission medium, and in WAN, wired is used as a transmission medium). Here, personal computers include desktop PCs, laptop PCs, and tablet PCs. Smartphones also include multifunctional mobile phone terminals.

The client of the video sharing service has a function of decoding the encoded data downloaded from the server and displaying it on the display, as well as a function of encoding the moving image captured by the camera and uploading it to the server. That is, the client of the video sharing service functions as both the transmitting device PROD_A and the receiving device PROD_B.

Next, it will be described with reference to FIG. 3 that the moving image coding device 11 and the moving image decoding device 31 described above can be used for recording and reproducing a moving image.

FIG. 3A is a block diagram showing the configuration of the recording device PROD_C equipped with the above-mentioned moving image coding device 11. As shown in the figure, the recording device PROD_C has a coding unit PROD_C1 that obtains coded data by encoding a moving image and a writing unit PROD_C2 that writes the coded data obtained by the coding unit PROD_C1 to the recording medium PROD_M. And have. The moving image coding device 11 described above is used as the coding unit PROD_C1.

The recording medium PROD_M may be of a type built in the recording device PROD_C, such as (1) HDD (Hard Disk Drive) or SSD (Solid State Drive), or (2) SD memory. It may be of a type that is connected to the recording device PROD_C, such as a card or USB (Universal Serial Bus) flash memory, and (3) DVD (Digital Versatile Disc: registered trademark) or BD (Blu-ray). It may be loaded in a drive device (not shown) built in the recording device PROD_C, such as Disc (registered trademark).

Further, the recording device PROD_C has a camera PROD_C3 that captures a moving image, an input terminal PROD_C4 for inputting a moving image from the outside, and a reception for receiving the moving image as a source of the moving image to be input to the coding unit PROD_C1. A unit PROD_C5 and an image processing unit PROD_C6 for generating or processing an image may be further provided. In the figure, the configuration provided by the recording device PROD_C is illustrated, but some of them may be omitted.

The receiving unit PROD_C5 may receive an unencoded moving image, or receives coded data encoded by a transmission coding method different from the recording coding method. It may be something to do. In the latter case, a transmission decoding unit (not shown) that decodes the coded data encoded by the transmission coding method may be interposed between the receiving unit PROD_C5 and the coding unit PROD_C1.

Examples of such a recording device PROD_C include a DVD recorder, a BD recorder, and an HDD (Hard Disk Drive) recorder (in this case, the input terminal PROD_C4 or the receiving unit PROD_C5 is the main source of moving images). .. In addition, a camcorder (in this case, the camera PROD_C3 is the main source of moving images), a personal computer (in this case, the receiving unit PROD_C5 or the image processing unit C6 is the main source of moving images), and a smartphone (this In this case, the camera PROD_C3 or the receiver PROD_C5 is the main source of moving images) is also an example of such a recording device PROD_C.

FIG. 3B is a block showing the configuration of the playback device PROD_D equipped with the above-mentioned moving image decoding device 31. As shown in the figure, the playback device PROD_D includes a reading unit PROD_D1 that reads the coded data written in the recording medium PROD_M, and a decoding unit PROD_D2 that obtains a moving image by decoding the coded data read by the reading unit PROD_D1. , Is equipped. The moving image decoding device 31 described above is used as the decoding unit PROD_D2.

The recording medium PROD_M may be of a type built into the playback device PROD_D, such as (1) HDD or SSD, or (2) SD memory card, USB flash memory, or the like. It may be of a type connected to the playback device PROD_D, or may be loaded into a drive device (not shown) built in the playback device PROD_D, such as (3) DVD or BD. Good.

Further, the playback device PROD_D has a display PROD_D3 for displaying the moving image, an output terminal PROD_D4 for outputting the moving image to the outside, and a transmitting unit for transmitting the moving image as a supply destination of the moving image output by the decoding unit PROD_D2. It may also have PROD_D5. In the figure, the configuration in which the playback device PROD_D is provided with all of these is illustrated, but some of them may be omitted.

The transmission unit PROD_D5 may transmit an unencoded moving image, or transmits coded data encoded by a transmission coding method different from the recording coding method. It may be something to do. In the latter case, it is preferable to interpose a coding unit (not shown) that encodes the moving image by a coding method for transmission between the decoding unit PROD_D2 and the transmitting unit PROD_D5.

Examples of such a playback device PROD_D include a DVD player, a BD player, an HDD player, and the like (in this case, the output terminal PROD_D4 to which a television receiver or the like is connected is the main supply destination of moving images). .. In addition, a television receiver (in this case, display PROD_D3 is the main supply destination of moving images) and digital signage (also called electronic signage or electronic bulletin board, etc., and display PROD_D3 or transmitter PROD_D5 is the main supply destination of moving images. (Before), desktop PC (in this case, output terminal PROD_D4 or transmitter PROD_D5 is the main supply destination of moving images), laptop or tablet PC (in this case, display PROD_D3 or transmitter PROD_D5 is video) An example of such a playback device PROD_D is a smartphone (in this case, the display PROD_D3 or the transmitter PROD_D5 is the main supply destination of the moving image), which is the main supply destination of the image.

(Hardware realization and software realization)
Further, each block of the moving image decoding device 31 and the moving image coding device 11 described above may be realized in hardware by a logic circuit formed on an integrated circuit (IC chip), or may be realized by a CPU (Central Processing). It may be realized by software using Unit).

In the latter case, each of the above devices is a CPU that executes instructions of a program that realizes each function, a ROM (Read Only Memory) that stores the above program, and a RAM (Random) that expands the above program.
Access Memory), a storage device (recording medium) such as a memory for storing the above programs and various data. Then, an object of the embodiment of the present invention is a record in which the program code (execution format program, intermediate code program, source program) of the control program of each of the above devices, which is software for realizing the above-mentioned functions, is recorded readable by a computer. It can also be achieved by supplying the medium to each of the above devices and having the computer (or CPU or MPU) read and execute the program code recorded on the recording medium.

Examples of the recording medium include tapes such as magnetic tapes and cassette tapes, magnetic disks such as floppy (registered trademark) disks / hard disks, and CD-ROMs (Compact Disc Read-Only Memory) / MO disks (Magneto-Optical discs). ) / MD (Mini Disc) / DVD (Digital Versatile Disc: registered trademark) / CD-R (CD Recordable) / Blu-ray Disc (registered trademark) and other disks including magneto-optical disks, IC cards (memory cards) (Including) / Cards such as optical cards, mask ROM / EPROM (Erasable Programmable Read-Only Memory) / EEPROM (Electrically Erasable and Programmable Read-Only Memory: registered trademark) / Semiconductor memories such as flash ROM, or PLD ( Logic circuits such as Programmable logic device) and FPGA (Field Programmable Gate Array) can be used.

Further, each of the above devices may be configured to be connectable to a communication network, and the above program code may be supplied via the communication network. This communication network is not particularly limited as long as it can transmit the program code. For example, Internet, Intranet, Extranet, LAN (Local Area Network), ISDN (Integrated Services Digital Network), VAN (Value-Added Network), CATV (Community Antenna television / Cable Television) communication network, Virtual Private network (Virtual Private) Network), telephone line network, mobile communication network, satellite communication network, etc. can be used. Further, the transmission medium constituting this communication network may be any medium as long as it can transmit the program code, and is not limited to a specific configuration or type. For example, even wired such as IEEE (Institute of Electrical and Electronic Engineers) 1394, USB, power line carrier, cable TV line, telephone line, ADSL (Asymmetric Digital Subscriber Line) line, infrared data such as IrDA (Infrared Data Association) and remote control , BlueTooth (registered trademark), IEEE802.11 wireless, HDR (High Data Rate), NFC (Near Field Communication), DLNA (Digital Living Network Alliance: registered trademark), mobile phone network, satellite line, terrestrial digital broadcasting network, etc. It is also available wirelessly. The embodiment of the present invention can also be realized in the form of a computer data signal embedded in a carrier wave in which the program code is embodied by electronic transmission.

The embodiment of the present invention is not limited to the above-described embodiment, and various modifications can be made within the scope of the claims. That is, an embodiment obtained by combining technical means appropriately modified within the scope of the claims is also included in the technical scope of the present invention.

The embodiment of the present invention is suitably applied to a moving image decoding device that decodes encoded data in which image data is encoded, and a moving image coding device that generates encoded data in which image data is encoded. be able to. Further, it can be suitably applied to the data structure of the coded data generated by the moving image coding device and referenced by the moving image decoding device.

31 Image decoder
301 Entropy Decryptor
302 Parameter decoder
3020 Header decoder
303 Inter prediction parameter decoding unit
304 Intra Prediction Parameter Decoder
308 Prediction image generator
309 Inter-prediction image generator
310 Intra prediction image generator
311 Inverse quantization / inverse conversion
312 Addition part
11 Image coding device
101 Predictive image generator
102 Subtraction section
103 Conversion / Quantization Department
104 Entropy encoding section
105 Inverse quantization / inverse conversion
107 Loop filter
110 Coded parameter determination unit
111 Parameter encoding section
112 Inter-prediction parameter encoding section
113 Intra Prediction Parameter Encoding Unit
1110 Header encoding
1111 CT information coding unit
1112 CU encoding unit (prediction mode encoding unit)
1114 TU coder
30954 BDOF section
309541 L0, L1 Prediction image generator
309542 Flag setting section
309543 Gradient image generator
309544 Correlation parameter calculation unit
309545 Motion compensation correction value derivation unit
309546 Bidirectional prediction image generator

Claims (4)

It has a predictive image generator using bidirectional gradient change processing that generates a predictive image by gradient change from two interpolated images.
The predicted image generation unit
The L0 and L1 prediction generators that generate the L0 prediction image and the L1 prediction image for each coding unit from the two interpolated images,
From the L0 prediction image and the L1 prediction image, a flag setting unit for determining whether or not bidirectional gradient change processing is performed for each coding unit, and
A gradient image generator that generates four gradient images in the horizontal direction and the vertical direction from the L0 predicted image and the L1 predicted image.
A correlation parameter calculation unit that calculates the correlation parameter for each processing unit from the product-sum calculation of the L0 prediction image, the L1 prediction image, and the four gradient images.
A motion compensation correction value deriving unit that derives a value for correcting a bidirectional prediction image from the gradient image and the correlation parameter.
It has a bidirectional prediction image generation unit that generates a prediction image from the L0 prediction image, the L1 prediction image, and the motion compensation correction value.
A moving image decoding device characterized in that the flag setting unit and the correlation parameter calculation unit have the same calculation accuracy of the difference between the L0 predicted image and the L1 predicted image. The moving image according to claim 1, wherein the flag setting unit and the correlation parameter calculation unit of the moving image decoding device make the calculation accuracy of the difference between the L0 predicted image and the L1 predicted image constant regardless of the pixel bit length. Decryptor. It has a predictive image generator using bidirectional gradient change processing that generates a predictive image from two interpolated images by a gradient change.
The predicted image generation unit
The L0 and L1 prediction generators that generate the L0 prediction image and the L1 prediction image for each coding unit from the two interpolated images,
From the L0 prediction image and the L1 prediction image, a flag setting unit for determining whether or not bidirectional gradient change processing is performed for each coding unit, and
A gradient image generator that generates four gradient images in the horizontal direction and the vertical direction from the L0 predicted image and the L1 predicted image.
A correlation parameter calculation unit that calculates the correlation parameter for each processing unit from the product-sum calculation of the L0 prediction image, the L1 prediction image, and the four gradient images.
A motion compensation correction value deriving unit that derives a value for correcting a bidirectional prediction image from the gradient image and the correlation parameter.
It has a bidirectional prediction image generation unit that generates a prediction image from the L0 prediction image, the L1 prediction image, and the motion compensation correction value.
A moving image coding device characterized in that the flag setting unit and the correlation parameter calculation unit make the calculation accuracy of the difference between the L0 predicted image and the L1 predicted image the same. A moving image characterized by making the calculation accuracy of the difference between the L0 predicted image and the L1 predicted image constant regardless of the pixel bit length in the flag setting unit and the correlation parameter calculation unit of the moving image encoding device according to claim 3. Image encoding device.

Images