JP2020195015A - Moving image decoding device and moving image encoding device - Google Patents

Abstract

To provide a moving image decoding device and a moving image encoding device which improve BIO processing in a case of generating a prediction image.SOLUTION: A moving image encoding device 31 comprises a prediction image generation unit 308 for generating a prediction image by motion compensation. The prediction image generation unit 308 derives a correction weighting vector relating to one of a luminance component and a color difference component with respect to a target block, refers to the derived correction weighting vector, and derives an offset value relating to the other one of the luminance component and the color difference component.SELECTED DRAWING: Figure 7

Description

Embodiments of the present invention relate to 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 methods proposed by H.264 / AVC and HEVC (High-Efficiency Video Coding).

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 the coding tree unit (sometimes called a coding unit (CU)), and a conversion unit (TU:) obtained by dividing the 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 1 and 2 can be mentioned as recent moving image coding and decoding techniques. Further, Non-Patent Document 3 discloses a BIO technique for improving the image quality by using a gradient image when deriving a predicted image from a bi-predicted motion compensation (interpolated image).

"Algorithm Description of Joint Exploration Test Model 7", JVET-L1001, Joint Video Exploration Team (JVET) of ITU-T SG 16 WP 3 and ISO / IEC JTC 1 / SC 29/WG 11, 2018-10-19 "CE4 History-based Motion Vector Prediction (Test 4.4.7)", JVET-L0266-v2, Joint Video Exploration Team (JVET) of ITU-T SG 16 WP 3 and ISO / IEC JTC 1 / SC 29/WG 11, 2018-10-4 "CE9-related: A simplified design of bi-directional optical flow (BIO)", JVET-L0591, Joint Video Exploration Team (JVET) of ITU-T SG 16 WP 3 and ISO / IEC JTC 1 / SC 29/WG 11 , 2018

In the above-mentioned techniques, there is room for improving the BIO processing when generating a predicted image.

One aspect of the present invention is to improve BIO processing in the case of generating a predicted image.

In order to solve the above problems, the moving image decoding device according to one aspect of the present invention obtains a predicted image by performing motion compensation by optical flow using a correction weight vector and an offset value for a plurality of reference images. A prediction image generation unit is provided, and the prediction image generation unit derives a correction weight vector for either a luminance component or a color difference component for a target block, and refers to the derived correction weight vector. Then, the offset values for the other components of the luminance component and the color difference component are derived.

According to one aspect of the present invention, BIO processing in the case of generating a predicted image can be improved.

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. PROD_A indicates a transmitting device equipped with a moving image encoding device, and PROD_B indicates a receiving device equipped with a moving image decoding device. It is a figure which showed the structure of the recording device which carried out the moving image coding device which concerns on this embodiment, and the reproduction device which carried out moving image decoding device. PROD_C indicates a recording device equipped with a moving image encoding device, and PROD_D indicates a playback 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 image generation part. It is a block diagram which shows the structure of the moving image coding apparatus. 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 the BIO prediction which concerns on this embodiment. It is the schematic which shows the structure of the BIO part which concerns on this embodiment. It is a figure which shows an example of the area where the BIO part which concerns on this embodiment executes BIO padding. It is a figure which shows an example of the BIO processing unit and the reading area of the BIO part which concerns on this embodiment. It is a conceptual diagram which shows an example of the BIO processing which concerns on this embodiment. It is a conceptual diagram which shows an example of the BIO processing which concerns on this embodiment.

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

FIG. 1 is a schematic view showing a configuration of an 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).

sign (a) is a function that returns the sign of a.

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 FIG. 4, the coded video sequence that defines the sequence SEQ, the coded picture that defines the picture PICT, the coded slice that defines the slice S, the coded slice data that defines the slice data, and the coded slice data, respectively. A diagram showing a coded tree unit included and a coded unit included in the coded tree unit is shown.

(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. 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 a picture PICT, as shown in the encoded video sequence of FIG. Includes Supplemental Enhancement Information (SEI).

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 the encoded picture in FIG. 4 (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 the coded slice of FIG.

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 contains a CTU, as shown in the encoded slice header of FIG. 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)
The coded tree unit of FIG. 4 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.

As CT information, CT includes a QT division flag (cu_split_flag) indicating whether or not to perform QT division, an MT division flag (split_mt_flag) indicating the presence or absence of MT division, and an MT division direction (split_mt_dir) indicating the division direction of MT division. Includes MT split type (split_mt_type) indicating the split type of MT split. cu_split_flag, split_mt_flag, split_mt_dir, split_mt_type are transmitted for each encoding node.

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

When cu_split_flag is 0 and mtt_split_cu_flag is 0, the coded node is not divided and has one CU as a node (no division in FIG. 5). 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 (BT (horizontal division) in Fig. 5), and when mtt_split_cu_vertical_flag is 1 and mtt_split_cu_binary_flag is 1, the coding node is. It is vertically divided into two coding nodes (BT (vertical division) in Fig. 5). Also, when mtt_split_cu_vertical_flag is 0 and mtt_split_cu_binary_flag is 0, the encoding node is horizontally divided into 3 coding nodes (TT (horizontal division) in Fig. 5), and when mtt_split_cu_vertical_flag is 1 and mtt_split_cu_binary_flag is 0, it is encoded. The nodes are vertically divided into three coded nodes (TT (vertical division) in FIG. 5). These are shown in the CT information in FIG.

When 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 the coding unit of FIG. 4, 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, the rectangle indicates the picture, the arrow indicates the reference relationship of the picture, the horizontal axis indicates the time, I, P, and B in the rectangle indicate the intra-picture, the single-predicted picture, the bi-predicted picture, and the numbers in the rectangle indicate the decoding 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. FIG. 6 shows an example of a 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, and thereafter, 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 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 includes 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, 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, separates and decodes each code (syntax element).

For entropy coding, a method of variable-length coding of syntax elements using a context (probability model) adaptively selected according to the type of syntax element and the surrounding situation, a predetermined table, or There is a method of variable-length coding the syntax element using a calculation formula. The former CABAC (Context Adaptive Binary Arithmetic Coding) stores a stochastic model updated for each encoded or decoded picture (slice) in memory. Then, as the initial state of the context of the P picture or the B picture, the probability model of the picture using the same slice type and the same slice level quantization parameter is set from the probability models stored in the memory. This initial state is used for encoding and decoding processing. The separated codes include prediction information for generating a prediction image, prediction error for generating a difference image, and the like.

The entropy decoding unit 301 outputs the separated codes to the parameter decoding unit 302. The separated codes are, for example, the prediction mode predMode, the merge flag merge_flag, the merge index merge_idx, the inter prediction identifier inter_pred_idc, the reference picture index refIdxLX, the prediction vector index mvp_LX_idx, the difference vector mvdLX, the 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.

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 syntactic elements included in the encoded data, for example, the merge flag merge_flag, the merge index merge_idx, and the inter-prediction identifier. Extract inter_pred_idc, reference picture index refIdxLX, prediction vector index mvp_LX_idx, and difference vector mvdLX.

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 and the prediction mode predMode and the like separated by the entropy decoding unit 301.

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 generator)
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 is used. To generate.

FIG. 8 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 compositing unit 3095 predicts 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, an OBMC unit 30953, and a BIO unit (BIOF unit, 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)
In Triangle prediction, the target CU is divided into two triangular prediction units with the diagonal or opposite diagonal as the boundary. The Triangle compositing unit 30952 generates a prediction image by applying a weighting mask process to the prediction image of each triangle prediction unit according to the position of the pixel of the target CU (rectangular block including the triangle prediction unit). For example, a triangular image is derived from a rectangular image by multiplying a mask in which the pixel of the triangular region in the rectangular region is 1 and the region other than the triangle is 0.

(BIO processing)
The BIO unit 30954 generates a predicted image by performing BIO (Bi-directional optical flow; bi-predicted gradient change) processing. In the BIO processing, a prediction image is generated by referring to the motion compensation images PredL0 and PredL1 and the gradient correction term. The BIO unit 30954 may be configured to generate a predicted image by performing weight prediction described later.

Since BIO is also referred to as BIOF (Bi-Directional Optical Flow), BIO may be replaced with BIOF in the present specification. In addition, other terms may be used.

(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, 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. In the coding process, this quantization transform coefficient is used for prediction errors such as DCT (Discrete Cosine Transform), DST (Discrete Sine Transform), and KLT (Karyhnen Loeve Transform). It is a coefficient obtained by performing frequency conversion such as, and quantizing. The inverse quantization / inverse conversion unit 311 performs inverse frequency conversion such as inverse DCT, inverse DST, and inverse KLT 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.

(BIO prediction)
Next, the details of the prediction (BIO prediction) using the BIO processing performed by the BIO unit 30954 will be described. The BIO 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. 10 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 unidirectional prediction is made (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 unidirectional prediction is performed (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 it 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 BIO processing by referring to the BIO Available Flag indicating whether or not BIO processing is performed. When the BIOAvailableFlag indicates TRUE, the BIO unit 30954 executes BIO processing to generate a bidirectional prediction image (S106). When the BIOAvailableFlag indicates FALSE, the synthesizer 3095 generates a predicted image by normal bilateral predicted image generation (S105).

The inter-prediction parameter decoding unit 303 may derive TRUE to BIOAvailableFlag 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, assuming that the target image is currPic, BIOAvailableFlag 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 BIOAvailableFlag indicates TRUE, a condition that the motion vector of the target block is not a motion vector in subblock units may be added.

Further, as a condition that BIOAvailableFlag indicates TRUE, a condition that the absolute difference sum between the L0 predicted image and the L1 predicted image of the two prediction blocks is equal to or more than a predetermined value may be added.

Further, as a condition that BIOAvailableFlag indicates TRUE, a condition that the prediction image creation mode for each block is set may be added.

In addition, as a condition that BIOAvailableFlag indicates TRUE, luma_weight_l0_flag [refIdxL0], luma_weight_l1_flag [refIdxL1], chroma_weight_l0_flag [refIdxL0], chroma_weight_l1_flag [refIdxL1] are all 0, that is, the reference picture of the target block has no brightness difference. , May be added. Here, refIdxLX (X = 0,1) is the reference picture stored in the reference picture list X of the target block, and luma_weight_lX_flag [] and chroma_weight_lX_flag [] (X = 0,1) are the brightness and color difference related to the reference picture list X. It is a flag indicating the presence or absence of the weighting coefficient of.

The details of the specific processing performed by the BIO unit 30954 will be described with reference to FIG. The BIO unit 30954 includes an L0, L1 prediction image generation unit 309541, a gradient image generation unit 309542, a correlation parameter calculation unit 309543, a motion compensation correction value derivation unit 309544, and a bidirectional prediction image generation unit 309545. .. The BIO 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 BIO processing. In the BIO section 30954, BIO processing is performed based on the L0 and L1 predicted images for each CU unit or sub CU unit shown in FIG. 9, but in order to obtain the gradient, the surroundings of the target CU or sub CU are performed. Further interpolated image information for two pixels is required. In the case of gradient image generation described later, the interpolated image information of this part is generated by using nearby pixels instead of a normal interpolation filter. When calculating the correlation parameter, this part is used as a padding area by copying the surrounding pixels as well as the outside of the picture. The unit of BIO processing is NxN pixels of CU unit or sub CU unit or less, and the processing itself is performed using pixels of (N + 2) x (N + 2) with one peripheral pixel added. Do.

The gradient image generation unit 309542 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 change of the pixel value I. It can be expressed as follows using the time change lt.

lx * Vx + ly * Vy + lt = 0
Here, the values of Vx and Vy are calculated by the gradient image generation unit 309542 from the difference between the L0 and L1 predicted images and the gradient. Hereinafter, the change in position (Vx, Vy) may be referred to as a correction weight vector (u, v).

Specifically, the gradient image generation unit 309542 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.

In the known examples in the past, there is a problem that the calculation accuracy with respect to the coded pixel bit length is not sufficient, and the coding efficiency is lowered when the pixel bit length is a certain value or more. Therefore, a parameter called Internal BitDepth, which is independent of the pixel bit length BitDepth, is defined as the calculation accuracy in the BIO section. Then, by making this value constant as shown below, it is within the range of 32-bit operation regardless of BitDepth. Here, InternalBitDepth is set to a value of 7 or more and 12 or less.

Specifically, the gradient image generation unit 309542 derives the gradient images lx0, ly0, lx1, and ly1 as follows.

lx0 [x] [y] = (PredL0 [x + 1] [y]-PredL0 [x-1] [y]) >> shift0 (Equation BIO-1)
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.

Another way to derive the gradient images lx0, ly0, lx1, ly1 is
lx0 [x] [y] = (PredL0 [x + 1] [y] >> shift0)-(PredL0 [x-1] [y] >> shift0) (Equation BIO-1B)
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)
May be. In (Equation BIO-1), if the range of the minimum and maximum values of PredL0 and PredL1 is 16 bits, the difference is 17 bits, so a 32-bit operation is required. (Equation BIO-1B) has the advantage that parallel arithmetic instructions are easy to use because all operations can be executed by 16-bit operation because the right shift is performed first.

In either case, when using an interpolation filter similar to 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 309543 derives the sum of gradient products s1, s2, s3, s5, s6 for each block of NxN pixels in the CU. Here, s1, s2, s3, s5, s6 are calculated by various product-sum operations of the block of (N + 2) * (N + 2) pixels by further using one pixel around the block.

s1 = sum (phiX [x] [y] * phiX [x] [y]) (Equation BIO-2)
s2 = sum (phiX [x] [y] * phiY [x] [y])
s3 = sum (-theta [x] [y] * phiX [x] [y])
s5 = sum (phiY [x] [y] * phiY [x] [y])
s6 = sum (-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 (N + 2) x (N + 2) pixels. Further, the sum phiX [x] [y] and phiY [x] [y] of the difference theta, L0, and L1 gradient images between the L0 and L1 predicted images are derived by the following equations. A shift operation may be performed in deriving theta, phiX, and phiY.

theta [x] [y] =-(PredL1 [x] [y] >> shift4) + (PredL0 [x] [y] >> shift4) (Equation BIO-3)
phiX [x] [y] = (lx1 [x] [y] + lx0 [x] [y]) >> shift5
phiY [x] [y] = (ly1 [x] [y] + ly0 [x] [y]) >> shift5
here,
shift4 = Max (InternalBitDepth-4, bitDept + InternalBitDepth-16)
shift5 = Max (InternalBitDepth-7, BitDepth + InternalBitDepth-19)
And.

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, when N = 4, the calculation accuracy of s1, s2, s5, which is the total of 6x6 pixel blocks, is about 23 bits regardless of BitDepth. Similarly, when N = 4, 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, so 32-bit integer arithmetic is used. realizable.

More specifically, if InternalBitDepth = 8
shift0 = 6
shift4 = Max (4, BitDepth-8)
shift5 = Max (1, BitDepth-11)
And if InternalBitDepth = 7
shift0 = 7
shift4 = Max (3, BitDepth-9)
shift5 = Max (0, BitDepth-12)
Will be.

As another configuration of the correlation parameter calculation unit 309543, the sum of gradient products s1, s2, s3, s5, s6 is obtained by the block of NxN pixels instead of the block of (N + 2) x (N + 2) pixels. May be good. When N = 4, the block is 4x4 = 16 pixels, so the calculation bits required to calculate sum are (Ceil (log2 (36))-Ceil (log2 (16)) compared to the total of 6x6 = 36 pixels. )) = 2 bits less, so
shift4 = Max (InternalBitDepth-5, bitDept + InternalBitDepth-15)
shift5 = Max (InternalBitDepth-8, BitDepth + InternalBitDepth-18)
Even if each value is 1 bit smaller, it can be realized by 32-bit integer arithmetic. 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. 13, since the unit of BIO processing and the reading area match, unlike the case of FIG. 12, the padding area for one pixel around the target CU or sub CU becomes unnecessary.

Regarding the Bilinear filter processing area in FIG. 13, it is also possible to perform so-called padding processing in which one pixel around the inside of the CU or sub-CU is copied to one outer pixel, so that the Bilinear filter processing is not performed. ..

Next, the motion compensation correction value deriving unit 309544 derives a correction weight vector (u, v) in units of NxN pixels by using the derived gradient product sum s1, s2, s3, s5, s6.

u = (s3 << 3) >> floor (log2 (s1)) (Equation BIO-4)
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 = Max (2, 1 << (13-InternalBitDepth))
Is. Since th is derived from Internal BitDepth, the pixel-by-pixel correction weight vector (u, v) is clipped by the value associated with Internal BitDepth. 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 is
th0 = Max (1, 1 << (12-InternalBitDepth))
th = th0 + floor ((Qp-32) / 6)
It may be expressed by a function of the quantization width Qp as in.

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 = Max (InternalBitDepth-7, BitDepth + InternalBitDepth-19)
And. In this case, it is not necessary to change shift0 and shift5. Specifically, when InternalBitDepth = 8,
shift4 = Max (1, BitDepth-11)
Will be.

The motion compensation correction value derivation unit 309544 derives the motion compensation correction value bdofOffset using the correction weight vector (u, v) in NxN pixel units 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 (Formula BIO-5)
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
In this case, the selection range of InternalBitDepth is 8 or more and 12 or less.
shift0 = 15-InternalBitDepth
shift5 = Max (InternalBitDepth-8, BitDepth + InternalBitDepth-20)
To change. No shift4 changes are required. Specifically, when InternalBitDepth = 8,
shift0 = 7
shift5 = Max (0, BitDepth-12)
Will be.

The bidirectional prediction image generation unit 309545 derives the pixel value Pred of the prediction image of NxN 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, there is no problem that the coding efficiency is lowered when the pixel bit length is 13 bits or more, and it can be realized by an operation of 32 bits or less regardless of the pixel bit length.

(BIO processing example 1)
Hereinafter, an example of the processing performed by the BIO unit 30954 according to the present embodiment will be described from another aspect. FIG. 14 is a conceptual diagram showing processing until the BIO unit 30954 according to this example derives the luminance Y and the offset bdofOffset for the color differences U and V when performing the BIO processing.

The BIO unit 30954 executes the following steps for the first color component (cIdx = 0, hereinafter, luminance component) of the target block. Note that cIdx is a variable for identifying color components. 0, 1, 2 indicate the first, second, and third color components, such as (Y, Cb, Cr), (R, G, B), (G, B, R), respectively.
(A1) The difference theta between the gradient images lx0, ly0, lx1, ly1 and L0, L1 predicted images of the luminance component is derived.
(A2) The correction weight vectors Vx and Vy are derived from lx0, ly0, lx1, ly1 and theta. For example, it is derived using (Equation BIO-2), (Equation BIO-3), and (Equation BIO-4).
(A3) The bdofOffset is derived from the luminance components lx0, ly0, lx1, ly1 derived in (A1) and Vx, Vy derived in (A2). For example, it is derived using (Equation BIO-5).

In addition, the BIO unit 30954 executes the following steps for the second and third color components (cIdx = 1, 2, hereinafter, color difference components) of the target block.
(B1) Gradient images of color difference components lx0, ly0, lx1, ly1 are derived.
(B2) The bdofOffset is derived from the color difference components lx0, ly0, lx1, ly1 derived in (B1) and Vx, Vy derived in (A2). That is, the motion compensation correction value deriving unit 309544 is also used when deriving Vx and Vy corresponding to the first color component (luminance component) and bdofOffset corresponding to the second and third color components (color difference component). .. For example, it is derived using (Equation BIO-5).

Further, the BIO unit 30954 sets the threshold value Th for limiting Vx and Vy to different values for the luminance component and the color difference component when the number of pixel bits differs between the luminance component and the color difference component, and Vx, The value of Vy may be corrected. For example, assuming that the threshold value for the brightness component is ThY and the threshold value for the color difference component is ThC, when the value of ThY is larger than ThC, the BIO unit 30954 logs the respective values of Vx and Vy for the color difference component. ₂ ThY --log _{2 It} may be corrected by shifting to the right by the value of ThC. The right shift corresponds to dividing the target value by a power of 2. Further, when the value of ThY is smaller than that of ThC, the BIO unit 30954 may correct each value of Vx and Vy for the color difference component by shifting left by the amount of log ₂ ThY --log ₂ ThC. The BIO unit 30954 may perform the above-mentioned correction on the bdofOffset obtained from them instead of Vx and Vy.

In other words, when the threshold value for limiting the range of values indicated by the correction weight vector is different between the luminance component and the color difference component for the target block, the prediction image generation unit describes the above-mentioned configuration example for correction. , Any one of the correction weight vector and the offset value for any one of the luminance component and the color difference component is set to a value corresponding to the threshold value corresponding to the luminance component and the threshold value corresponding to the color difference component. It may be set. The same applies to (BIO processing example 2). As a result, even when the number of pixel bits differs between the luminance component and the color difference component, BIO processing can be preferably performed.

Further, the BIO unit 30954 may correct the values of Vx and Vy when the resolutions of the luminance image and the color difference image corresponding to the predicted image are different from each other. For example, when the resolution of the predicted image is 4: 2: 0, the number of pixels in the vertical direction and the horizontal direction of the color difference image is reduced by half as compared with the luminance image. This means that the gradient of the color difference component is obtained based on the pixels that are twice as far apart as the case where the gradient of the luminance component is obtained. In order to solve this difference, the BIO unit 30954 may correct the values of Vx and Vy for the color difference component to 1/2. Note that the BIO unit 30954 may perform correction to halve the gradient in each direction instead of Vx and Vy.

Also, when the resolution of the predicted image is 4: 2: 2, the resolutions of the corresponding luminance image and the color difference image are the same in the vertical direction, so the BIO section 30954 halves only the Vx or horizontal gradient. The correction will be made.

In other words, when the prediction image generation unit determines that the resolutions of the luminance image and the color difference image are different from each other, the target block has one of the luminance component and the color difference component. Either of the correction weight vector related to the component and the gradient value used for deriving the correction weight vector may be corrected by a value corresponding to the ratio of the resolution of the luminance image and the resolution of the color difference image. The same applies to (BIO processing example 2) described later. As a result, even when the resolutions of the luminance image and the color difference image are different from each other, the BIO processing can be preferably performed.

According to the above-mentioned step, it is not necessary for the BIO unit 30954 to derive the difference theta between the L0 and L1 predicted images and Vx and Vy for the color difference component. For example, the calculations of (Equation BIO-2), (Equation BIO-3), and (Equation BIO-4) can be omitted except for the first color component (color difference component). As a result, the amount of processing in the BIO unit 30954 can be reduced. The process shown in FIG. 14 is based on the estimation that Vx and Vy related to the movement of each color component (luminance component and color difference component, respectively) are close to each other. Further, as another embodiment, the BIO unit 30954 may use the Vx and Vy derived for the color difference component when deriving the bdoOffset corresponding to the luminance component.

Further, the moving image decoding device 31 according to the present example that executes the above-described step generates a predicted image by performing motion compensation by an optical flow using a correction weight vector and an offset value for a plurality of reference images. A prediction image generation unit 308 is provided, and the prediction image generation unit 308 derives a correction weight vector for each color component (luminance component and color difference component) and a correction weight vector for any of the components of the target block, and the derived correction weight is derived. It can be said that the configuration is such that the offset values relating to the other components of the luminance component and the color difference component are derived with reference to the vector. According to the above configuration, it can be improved so as to reduce the processing amount of the BIO processing in the moving image decoding device 31.

(BIO processing example 2)
A second example of the processing performed by the BIO unit 30954 according to the present embodiment will be described. It should be noted that the duplicate description of the matters already explained in the above example will not be repeated. FIG. 15 is a conceptual diagram showing the processing until the BIO unit 30954 according to this example derives the offset bdofOffset for the luminance Y, the color difference U and V when performing the BIO processing.

The BIO unit 30954 executes the following steps for each color component (for example, luminance component and color difference component) of the target block.
(C1) The difference theta between the gradient images lx0, ly0, lx1, ly1 and L0, L1 predicted images is derived.
(C2) The correction weight vectors Vx and Vy are derived from lx0, ly0, lx1, ly1 and theta.
(C3) The bdofOffset is derived from lx0, ly0, lx1, ly1 and Vx, and Vy.

As described above, the BIO processing in this example is performed for both the color components (cIdx = 0, 1, 2, the luminance component and the luminance component), and the first color component (cIdx = 0, the luminance component) is used. It differs from the conventional BIO processing that is performed only. According to the above steps, the BIO process can be improved so as to contribute to improving the image quality of the decoded image generated by the moving image decoding device 31. The effect is particularly remarkable when the decoded image has a so-called 4: 4: 4 resolution in which the brightness and the color difference have the same resolution.

For example, when the correlation between color components is low as in RGB, it may be more efficient to separate and process the three color components. separate_colour_plane_flag is a flag indicating whether to process each color component together or separately. When the color difference format is 4: 4: 4 (for example, when chroma_format_idc = 3), separate_colour_plane_flag is encoded and decoded. If separate_colour_plane_flag = 0, the moving image coding device 11 and the moving image decoding device 31 include three color components (for example, Y, Cb, Cr) in one CTU and encode using the correlation between the color components. , Decryption process. If separate_colour_plane_flag = 1, only one color component (for example, R only, G only, B only) is included in one CTU, and the correlation between color components is not used, and each color component is separated for encoding and decoding processing. To do. In this case, three CTUs for each color component are encoded and decoded. When separate_colour_plane_flag = 0, a common motion vector is derived, but when separate_colour_plane_flag = 1, a motion vector is derived for each color component. Therefore, when separate_colour_plane_flag = 0, (BIO processing example 1) may be used to derive the bdofOffset, and when separate_colour_plane_flag = 1, (BIO processing example 2) may be used to derive the bdofOffset. Note that chroma_format_idc is a syntax element in the coded data indicating color difference sampling, chroma_format_idc = 0 is monochrome, chroma_format_idc = 1 is 4: 2: 0, chroma_format_idc = 2 is 4: 2: 2, chroma_format_idc = 3 is It may indicate 4: 4: 4. As another example, it may be determined whether or not to apply (BIO processing example 2) by referring to matrix_coeffs included in vui_parameters (). matrix_coeffs is a flag that informs the coefficients used to derive the luminance signal and the color difference signal from RGB. When matrix_coeffs = 0, it indicates that the RGB image has been encoded. Therefore, when matrix_coeffs = 0, (BIO processing example 2) may be applied to derive bdofOffset.

Further, the moving image decoding device 31 according to the present example that executes the above-described step generates a predicted image by performing motion compensation by an optical flow using a correction weight vector and an offset value for a plurality of reference images. It can be said that the prediction image generation unit 308 is provided, and the prediction image generation unit 308 is configured to derive a correction weight vector and an offset value for all the brightness components and the color difference components for the target block. According to the above configuration, it contributes to improving the image quality of the decoded image generated by the moving image decoding device 31.

In each of the above-mentioned examples, the BIO unit 30954 performs BIO processing on all of the luminance Y and the color differences U and V, or does not perform BIO processing on any of them (Early Terminaten).

Whether or not the BIO unit 30954 performs BIO processing for each component depends on the value of BIO Available Flag. When the value of BIOAvailableFlag is TRUE, FALSE may be set when the absolute value difference sum bdofBlkSumDiff of the L0 reference image refImgL0 and the L1 reference image refImgL1 of the block or subblock is smaller than the threshold value. That is, if the difference between the L0 reference image and the L1 reference image is small, BIO processing is not performed. The absolute value difference sum bdofBlkSumDiff may be obtained only from the luminance signal, and the BIO Available Flag may be changed with that value for both luminance and color difference. The absolute value difference sum bdofBlkSumDiff may be determined for each luminance and color difference. In this case, the value of BIO Available Flag may be changed for each luminance and color difference. Alternatively, the absolute value difference sum bdofBlkSumDiff may be obtained for each Y, U, V. In this case, the value of BIO Available Flag may be changed for each Y, U, V. As a result, it is possible to match whether or not the BIO treatment is applied to each component.

(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. 9 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. Further, the prediction image generation unit 101 may perform the above-mentioned BIO processing in (BIO processing example 1) and (BIO processing example 2) in the same manner as the prediction image generation unit 308.

That is, the moving image coding device 11 according to the present embodiment corresponding to (BIO processing example 1) performs motion compensation by optical flow using a correction weight vector and an offset value for a plurality of reference images. A prediction image generation unit 101 for generating a prediction image is provided, and the prediction image generation unit 101 derives a correction weight vector and an offset value for either a brightness component or a color difference component for a target block. It can be said that the offset values relating to the other components of the brightness component and the color difference component are derived with reference to the derived correction weight vector. According to the above configuration, it can be improved so as to reduce the processing amount of BIO processing in the moving image coding apparatus 11.

Further, in the above configuration, the prediction image generation unit determines the luminance component when the threshold value for limiting the range of values indicated by the correction weight vector is different between the luminance component and the color difference component for the target block. And any of the correction weight vector and the offset value for any of the components of the color difference component are set to values corresponding to the threshold value corresponding to the luminance component and the threshold value corresponding to the color difference component. May be good. As a result, even when the number of pixel bits differs between the luminance component and the color difference component, BIO processing can be preferably performed.

Further, the moving image coding device 11 according to the present embodiment corresponding to (BIO processing example 2) performs motion compensation by optical flow using a correction weight vector and an offset value for a plurality of reference images. It can be said that the predictive image generation unit 101 for generating the predictive image is provided, and the predictive image generation unit 101 derives a correction weight vector and an offset value for all the brightness components and the color difference components for the target block.

According to the above configuration, by improving the image quality of the locally decoded image generated by the moving image coding device 11, it contributes to improving the image quality of the decoded image generated by the corresponding moving image decoding device 31. ..

In the moving image coding device 11 corresponding to (BIO processing examples 1 and 2), when the prediction image generation unit determines that the resolutions of the luminance image and the color difference image are different from each other, the luminance of the target block is increased. One of the correction weight vector for any of the components and the color difference component and the gradient value used for deriving the correction weight vector depends on the ratio of the resolution of the luminance image and the resolution of the color difference image. It may be corrected by the value. As a result, even when the resolutions of the luminance image and the color difference image are different from each other, the BIO processing can be preferably performed.

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 apparatus 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, prediction mode predMode, and merge index merge_idx.

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

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 division flag, CU residual flag, 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 have 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 inter-prediction parameter coding unit 112 derives an inter-prediction parameter based on the prediction parameter input from the coding parameter determination unit 110. The inter-prediction 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 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 a program for realizing a part of the above-mentioned functions, and may be a program for realizing 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. 2 shows 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 transmitter PROD_A has a coding unit PROD_A1 that obtains encoded 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 is provided with 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 coding method for recording may be interposed between the recording medium PROD_A5 and the coding unit PROD_A1.

Further, FIG. 2 shows 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 coded 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, it is preferable to interpose a coding unit (not shown) that encodes the moving image acquired from the decoding unit PROD_B3 according to the coding method for recording 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. 3 shows a block diagram showing the configuration of the recording device PROD_C equipped with the moving image coding device 11 described above. 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 into 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, it is preferable to interpose a transmission decoding unit (not shown) between the receiving unit PROD_C5 and the coding unit PROD_C1 to decode the coded data encoded by the transmission coding method.

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.

Further, FIG. 3 shows a block showing the configuration of the reproduction 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) for encoding 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, a RAM (Random Access Memory) that expands the above program, the above program, and various types. It is equipped with a storage device (recording medium) such as a memory for storing 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 decoding device (moving image decoding device)
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 (moving image coding device)
101 Predictive image generator
102 Subtraction section
103 Conversion / Quantization Department
104 Entropy encoding section
105 Inverse quantization / inverse conversion part
107 Loop filter
110 Coded parameter determination unit
111 Parameter encoding section
112 Inter-prediction parameter encoding section
113 Intra Prediction Parameter Encoding Unit
30954 BIO section (BIOF section, BDOF section)

Claims (8)

It is equipped with a prediction image generator that generates a prediction image by performing motion compensation by optical flow using a correction weight vector and an offset value for a plurality of reference images.
The predicted image generation unit
For the target block, derive the correction weight vector for either the luminance component or the color difference component, and derive the correction weight vector.
A moving image decoding apparatus characterized in that an offset value relating to another component of the luminance component and the color difference component is derived with reference to the derived correction weight vector. The predicted image generation unit
When the threshold value for limiting the range of values indicated by the correction weight vector for the target block is different between the luminance component and the color difference component,
One of the correction weight vector and the offset value for any one of the luminance component and the color difference component is set to a value corresponding to the threshold value corresponding to the luminance component and the threshold value corresponding to the color difference component. The moving image decoding device according to claim 1, wherein the moving image decoding device is characterized. It is equipped with a prediction image generator that generates a prediction image by performing motion compensation by optical flow using a correction weight vector and an offset value for a plurality of reference images.
The predicted image generation unit
A moving image decoding device characterized by deriving a correction weight vector and an offset value for all of the luminance component and the color difference component for the target block. The predicted image generation unit
When it is determined that the resolutions of the luminance image and the color difference image are different from each other,
For the target block, one of the correction weight vector for any one of the luminance component and the color difference component and the gradient value used for deriving the correction weight vector is determined by the resolution of the luminance image and the color difference image. The moving image decoding apparatus according to any one of claims 1 to 3, wherein the value is corrected according to the ratio to the resolution of. It is equipped with a prediction image generator that generates a prediction image by performing motion compensation by optical flow using a correction weight vector and an offset value for a plurality of reference images.
The predicted image generation unit
For the target block, derive the correction weight vector for either the luminance component or the color difference component, and derive the correction weight vector.
A moving image coding apparatus characterized in that an offset value relating to another component of the luminance component and the color difference component is derived with reference to the derived correction weight vector. The predicted image generation unit
When the threshold value for limiting the range of values indicated by the correction weight vector for the target block is different between the luminance component and the color difference component,
One of the correction weight vector and the offset value for any one of the luminance component and the color difference component is set to a value corresponding to the threshold value corresponding to the luminance component and the threshold value corresponding to the color difference component. The moving image coding device according to claim 5, wherein the moving image coding apparatus is used. It is equipped with a prediction image generator that generates a prediction image by performing motion compensation by optical flow using a correction weight vector and an offset value for a plurality of reference images.
The predicted image generation unit
A moving image coding device characterized by deriving a correction weight vector and an offset value for all of the luminance component and the color difference component for the target block. The predicted image generation unit
When it is determined that the resolutions of the luminance image and the color difference image are different from each other,
For the target block, one of the correction weight vector for any one of the luminance component and the color difference component and the gradient value used for deriving the correction weight vector is determined by the resolution of the luminance image and the color difference image. The moving image coding apparatus according to any one of claims 5 to 7, wherein the value is corrected to a value corresponding to the ratio with the resolution of.

Images