Video decoding apparatus, video coding apparatus

Abstract

This invention aims to enhance precision by adding the EIP merge modes in TIMD and DIMD method. This invention enriches the number and variety of selectable candidate intra prediction modes in TIMD and DIMD, thereby enabling the generation of higher precision prediction images. This invention also achieves the effect of accelerating the codec process by disabling prediction tools with lower gains (the combination of TIMD and ISP, and the combination of TIMD and MRL).

Description

VIDEO DECODING APPARATUS, VIDEO CODING APPARATUS

[0001] The embodiments of the present invention relate to, a video decoding apparatus, a video coding apparatus.

[0002] A video coding apparatus which generates coded data by coding a video, and a video decoding apparatus which generates decoded images by decoding the coded data are used for efficient transmission or recording of videos.

[0003] For example, specific video coding schemes include H.264 / AVC, High-Efficiency Video Coding (HEVC), and Versatile Video Coding (VVC) schemes, and the like.

[0004] In such a video coding scheme, images (pictures) constituting a video are managed in a hierarchical structure including slices obtained by splitting an image, coding tree units (CTUs) obtained by splitting a slice, units of coding (coding units; which is referred to as CUs) obtained by splitting a coding tree unit, and transform units (TUs) obtained by splitting a coding unit, and are coded / decoded for each CU.

[0005] In such a video coding scheme, usually, a prediction image is generated based on a local decoded image that is obtained by coding / decoding an input image (a source image), and prediction error components (which may be referred to also as “difference images” or “residual images”) obtained by subtracting the prediction image from the input image are coded. Generation methods of prediction images include an inter-picture prediction (an inter-prediction) and an intra-picture prediction (intra prediction).

[0006] In recent video coding and decoding techniques, NPL1 introduces an enhancement TIMD method. In this method, TIMD derives two or three intra prediciton modes, as well as correspinding weights. The weighted blend of the prediction images is used as the prediction result for the current block.

[0007] NPL2 introduces DIMD method, DIMD derives five angular modes and one nonAngular mode, and their weights. The weighted blend of the prediction images is used as the prediction result for the current block.

[0008] NPL3 introduces EIP method. EIP method utilizes an extrapolation filter to establish a functional relationship between the target pixel value and the 15 surrounding pixel values. This relationship forms a function model that can predict the target pixel value from the 15 inputs.

[0009] NPL 1: P.Andrivan, M.Blestel, “EE2-1.20: TIMD fusion with non-angular predictor”, JVET-AG0092, JVET 33th Meeting, Online, 17-26 January 2024 NPL 2: K. Naser, etc, “EE2-1.4: IntraTMP extension to DIMD”, JVET-AG0146, JVET 33th Meeting, Online, 17-26 January 2024 NPL 3: L. Xu, etc, “EE2-2.7: An extrapolation filter-based intra prediction mode”, JVET-AF0080, JVET 32th Meeting, Hannover DE, 13-20 Oct 2023

[0010] The TIMD and DIMD methods derive one or more intra prediction modes, and the weighted fusion of these modes is used to produce the prediction result for the current block. The derived prediction modes are categorized into two types: angular and non-angular modes. In the ECM software, a new non-angular mode, known as the EIP mode, is utilized. However, the TIMD and DIMD methods do not include the EIP mode as a candidate for fusion.

[0011] The aim of this invention is to enhance prediction accuracy by incorporating EIP modes into the candidate list of TIMD and DIMD method.

[0012] According to an aspect of the present invention, the quality of the codecs can be improved without adding additional calculations.

[0013] FIG. 1 is a schematic diagram illustrating a configuration of an image transmission system according to the present embodiment.FIG. 2 is a diagram showing the hierarchical structure of the coded stream data.FIG. 3 is a schematic diagram showing the type of intra-prediction mode (mode number).FIG. 4 is a schematic diagram of the video decoding apparatus.FIG. 5 shows the structure of the intra prediction image generation unit.FIG. 6 is a diagram showing the details of the TIMD Prediction Unit.FIG. 7 is a diagram showing the position of template area and reference area used in timd.FIG. 8 shows position of the blocks adjacent to current block.FIG. 9 shows position of the blocks non-adjacent to current block.FIG. 10 is a block diagram showing the structure of a video coding apparatus.FIG. 11 is a diagram showing the reference area and filter used in Dimd.FIG. 12 is a diagram showing the structrue of DIMD Prediction Unit 31046.FIG. 13 is a diagram showing the partition of ISP.FIG. 14 shows the original and new syntax of the combination of timd and isp.FIG. 15 shows the position of reference lines and current block.FIG. 16 shows the original and new syntax of the combination of timd and MRL.FIG. 17 shows a syntax example of coding unit.

[0014] First Embodiment Hereinafter, embodiments of the present disclosure is described with reference to the drawings.

[0015] FIG. 1 is a schematic diagram illustrating a configuration of an image transmission system 1 according to the present embodiment.

[0016] The image transmission system 1 is a system in which a coding stream obtained by coding a coding target image is transmitted, the transmitted coding stream is decoded, and an image is displayed. The image transmission system 1 includes a video coding apparatus (image coding apparatus) 11, a network 21, a video decoding apparatus (image decoding apparatus) 31, and a video display apparatus (image display apparatus) 41.

[0017] An image T is input to the video coding apparatus 11.

[0018] The network 21 transmits a coding stream Te generated by the video coding apparatus 11 to the video decoding apparatus 31. The network 21 is the Internet, a Wide Area Network (WAN), a Local Area Network (LAN), or a combination thereof. The network 21 is not necessarily limited to a bidirectional communication network, and may be a unidirectional communication network configured to transmit broadcast waves of digital terrestrial television broadcasting, satellite broadcasting or the like. Furthermore, the network 21 may be substituted by a storage medium in which the coding stream Te is recorded, such as a Digital Versatile Disc (DVD: trademark) or a Blu-ray Disc (BD: trademark).

[0019] The video decoding apparatus 31 decodes each of the coding streams Te transmitted from the network 21 and generates one or multiple decoded images Td which are decoded.

[0020] The video display apparatus 41 displays all or part of the one or multiple decoded images Td generated by the video decoding apparatus 31. For example, the video display apparatus 41 includes a display device such as a liquid crystal display and an organic Electro-Luminescence (EL) display. Forms of the display include a stationary type, a mobile type, an HMD type, and the like. In addition, in a case that the video decoding apparatus 31 has a high processing capability, an image having high image quality is displayed, and in a case that the apparatus only has a lower processing capability, an image which does not require high processing capability and display capability is displayed.

[0021] Operator Operators and notations used in the present specification is described below.

[0022] >> is an arithmetic right bit shift, << is an arithmetic left bit shift, & is a bitwise AND, | is a bitwise OR, ^ is a bitwise XOR, |= is an OR assignment operator, and || indicates a logical sum.

[0023] x ? y : z is a ternary operator to take y in a case that x is TRUE (other than 0) and take z in a case that x is FALSE (0).

[0024] Clip3(x, y, z) is a function to clip z in a value equal to or greater than x and less than or equal to y, and a function to return x in a case that z is less than x (z < x), return y in a case that z is greater than y (z > y), and return z in other cases.

[0025] abs(a) is a function that returns the absolute value of a.

[0026] Int(a) is a function that returns the integer value of a.

[0027] floor(a) is a function that returns the maximum integer equal to or less than a.

[0028] ceil(a) is a function that returns the minimum integer equal to or greater than a.

[0029] a / d represents division of a by d (round down decimal places).

[0030] x = y..z represents x takes on integer values starting from y to z, inclusive, with x, y, and z being integer numbers and z being greater than or equal to y.

[0031] Structure of Coding Stream Te Prior to the detailed description of the video coding apparatus 11 and the video decoding apparatus 31 according to the present embodiment, a data structure of the coding stream Te generated by the video coding apparatus 11 and decoded by the video decoding apparatus 31 is described.

[0032] FIG. 2 is a diagram illustrating a hierarchical structure of data of the coding stream Te. The coding stream Te includes a sequence and multiple pictures constituting the sequence illustratively. (a) to (f) of FIG. 2 are diagrams illustrating a coded video sequence defining a sequence SEQ, a coded picture prescribing a picture PICT, a coding slice prescribing a slice S, a coding slice data prescribing slice data, a coding tree unit included in the coding slice data, and a coding unit (CU) included in each coding tree unit, respectively.

[0033] Coded Video Sequence In the coded video sequence (CVS, coding stream), a set of data referred to by the video decoding apparatus 31 to decode the coded sequence sequences to be processed is defined. As illustrated in FIG. 2, the CVS includes a Video Parameter Set (VPS), a Sequence Parameter Set (SPS), a Picture Parameter Set (PPS), a picture (PICT), and Supplemental Enhancement Information (SEI).

[0034] In the video parameter set VPS, in a video including multiple layers, a set of coding parameters common to multiple videos and a set of coding parameters associated with the multiple layers and an individual layer included in the video are defined.

[0035] In the sequence parameter set SPS, a set of coding parameters referred to by the video decoding apparatus 31 to decode a target sequence is defined. For example, a width and a height of a picture are defined. Note that multiple SPSs may exist. In that case, any of multiple SPSs is selected from the PPS.

[0036] In the picture parameter set PPS, a set of coding parameters referred to by the video decoding apparatus 31 to decode each picture in a target sequence is defined. For example, a reference value (pic_init_qp_minus26) of a quantization step size used for decoding of a picture and a flag (weighted_pred_flag) indicatingan application of a weighted prediction are included. Note that multiple PPSs may exist. In that case, any of multiple PPSs is selected from each picture in a target sequence.

[0037] Coded Picture In the coded picture, a set of data referred to by the video decoding apparatus 31 to decode the picture PICT to be processed is defined. As illustrated in FIG. 2, the picture PICT includes a slice 0 to a slice NS-1 (NS is the total number of slices included in the picture PICT).

[0038] Note that in a case that it is not necessary to distinguish each of the slice 0 to the slice NS-1 below, subscripts of reference signs may be omitted. In addition, the same applies to other data with subscripts included in the coding stream Te which is described below.

[0039] Coding Slice In the coding slice, a set of data referred to by the video decoding apparatus 31 to decode the slice S to be processed is defined. As illustrated in FIG. 2, the slice includes a slice header and a slice data.

[0040] The slice header includes a coding parameter group referred to by the video decoding apparatus 31 to determine a decoding method for a target slice. Slice type specification information (slice_type) indicating a slice type is one example of a coding parameter included in the slice header.

[0041] Examples of slice types that may be specified by the slice type specification information include (1) I slice using only an intra prediction in coding, (2) P slice using a unidirectional prediction or an intra prediction in coding, and (3) B slice using a unidirectional prediction, a bidirectional prediction, or an intra prediction in coding, and the like. Note that the inter prediction is not limited to a uni-prediction and a bi-prediction, and the prediction image may be generated by using a larger number of reference pictures. Hereinafter, in a case that a slice is referred to as the P or B slice, the slice indicates a slice that includes a block in which the inter prediction may be used.

[0042] Note that, the slice header may include a reference to the picture parameter set PPS (pic_parameter_set_id).

[0043] Coding Slice Data In the coding slice data, a set of data referred to by the video decoding apparatus 31 to decode the slice data to be processed is defined. The slice data include CTUs as illustrated in FIG. 2. The CTU is a block of a fixed size (for example, 64 x 64) constituting a slice.

[0044] Coding Tree Unit In FIG. 2, a set of data referred to by the video decoding apparatus 31 to decode the CTU to be processed is defined. The CTU is split into coding units CUs, each of which is a basic unit of coding processing, by a recursive Quad Tree split (QT split), Binary Tree split (BT split), or Ternary Tree split (TT split). The BT split and the TT split are collectively referred to as a Multi Tree split (MT split). Nodes of a tree structure obtained by recursive quad tree splits are referred to as Coding Nodes. Intermediate nodes of a quad tree, a binary tree, and a ternary tree are coding nodes, and the CTU itself is also defined as the highest coding node.

[0045] Coding Unit As illustrated in FIG. 2, a set of data referred to by the video decoding apparatus 31 to decode the coding unit to be processed is defined. Specifically, the CU includes a CU header CUH, a prediction parameter, a transform parameter, a quantization transform coefficient, and the like. In the CU header, a prediction mode and the like are defined.

[0046] There are cases that the prediction processing is performed in units of CU or performed in units of sub-CU obtained by further splitting the CU. In a case that the sizes of the CU and the sub-CU are equal to each other, the number of sub-CUs in the CU is one. In a case that the CU is larger in size than the sub-CU, the CU is split into sub-CUs. For example, in a case that the CU has a size of 8 x 8, and the sub-CU has a size of 4 x 4, the CU is split into four sub-CUs which include two horizontal splits and two vertical splits.

[0047] There are two types of predictions (prediction modes), which are an intra prediction and an inter prediction. The intra prediction refers to a prediction in an identical picture, and the inter prediction refers to prediction processing performed between different pictures (for example, between pictures of different display times).

[0048] Transform and quantization processing is performed in units of CU, but the quantization transform coefficient may be subjected to entropy coding in units of subblock such as 4 x 4.

[0049] Prediction parameter A prediction image is derived by a prediction parameter accompanying a block. The prediction parameter includes prediction parameters of the intra prediction and the inter prediction.

[0050] The prediction parameter of the intra prediction is described below. The intra prediction parameter includes a luma intra prediction mode IntraPredModeY and a chroma intra prediction mode IntraPredModeC. FIG. 3 is a schematic diagram indicating types (mode numbers) of the intra prediction mode. As illustrated in the diagram, for example, there are 67 types (0 to 66) of intra prediction modes. Additionally there are 28 types (-14 to -1 and 67 to 80) of intra prediction modes depend on the aspect ratio of CU. For example, a planar prediction (0), a DC prediction (1), and Angular predictions (2 to 66) are present. Furthermore, for chroma, CCLM (Cross Component Linear Model) prediction mode (81 to 83),MMLM (Multi Mode Linear Model) prediction mode, and LM (Linear Model) prediction modemay be added.

[0051] Configuration of video decoding apparatus A configuration of the video decoding apparatus 31 (FIG. 4) according to the present embodiment is described.

[0052] The video decoding apparatus 31 includes an entropy decoding unit 301, a parameter decoding unit (prediction image decoding apparatus) 302, a loop filter 305, a reference picture memory 306, a prediction parameter memory 307, a prediction image generation unit 308, an inverse quantization and inverse transform processing unit 311, an addition unit 312, and a prediction parameter derivation unit 320. Note that a configuration in which the loop filter 305 is not included in the video decoding apparatus 31 is also used in accordance with the video coding apparatus 11 described later.

[0053] 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), and the CU decoding unit 3022 further includes a TU decoding unit 3024. These may be collectively referred to as a decoding module. The header decoding unit 3020 decodes, from coded data, parameter set information such as the VPS, the SPS, and the PPS, and a slice header (slice information). The CT information decoding unit 3021 decodes a CT from coded data. The CU decoding unit 3022 decodes a CU from coded data. In a case that a TU includes a prediction error, the TU decoding unit 3024 decodes QP update information (quantization correction value) and a quantization prediction error (residual_coding) from coded data.

[0054] Furthermore, an example in which a CTU and a CU are used as units of processing is described below, but the processing is not limited to this example, and processing in units of sub-CU may be performed. Alternatively, by replacing the CTU and the CU by a block and replacing the sub-CU by a subblock, and processing in units of blocks or subblocks may be performed.

[0055] The entropy decoding unit 301 performs entropy decoding on the coding stream Te input from the outside and separates and decodes individual codes (syntax elements). The separated codes include prediction information to generate a prediction image, a prediction error to generate a difference image, and the like. Entropy coding has a variable length coding method for syntax elements according to the context (probability model) adaptively selected according to the type of syntax elements and the surrounding conditions, and a variable length coding method for syntax elements using a predetermined table or formula.

[0056] The parameter decoding unit 302 notifies the entropy decoding unit 301 of which syntax elements need be decoded. The entropy decoding unit 301 outputs the syntax element to the prediction parameter derivation unit 320.

[0057] Configuration of Prediction Parameter Derivation Unit 320 The prediction parameter derivation unit 320 may derive the prediction parameters based on the output of the paremater decoding unit 302 and the prediction parematers which saved in the prediction parameter memory 307. The derived prediction parameters is output into the prediction image generation unit 308 and also is saved in the prediction parameter memory 307. The prediction parameter derivetion unit may derive different prediction mode for the Luma and Chroma prediction.

[0058] The loop filter 305 is a filter provided in the coding loop, and is a filter that removes block distortion and ringing distortion and improves image quality. The loop filter 305 applies a filter such as a deblocking filter (DF), a Sample Adaptive Offset (SAO), and an Adaptive Loop Filter (ALF) on a decoded image of a CU generated by the addition unit 312.

[0059] The reference picture memory 306 stores the decoded image of the CU generated by the addition unit 312 in a predetermined position for each target picture and target CU.

[0060] The prediction parameter memory 307 stores prediction parameters in a predetermined position for each CTU or CU to be decoded. Specifically, the prediction parameter memory 307 stores a parameter derived by the prediction parameter derivation unit 320, a prediction mode predMode separated by the entropy decoding unit 301, and the like.

[0061] The prediction image generation unit 308 receives input of the prediction parameter derived by the prediction parameter deviation unit 320, and the like. In addition, the prediction image generation unit 308 reads a 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 refers to a set of pixels (referred to as a block because they are normally rectangular) on a reference picture and is a region that is referred to to generate a prediction image.

[0062] Prediction Image Generation Unit 308 In a case that the prediction mode predMode indicates an intra prediction mode, the intra prediction image generation unit 310 performs an intra prediction by using an intra prediction parameter (luma intra prediction mode IntraPredModeY and / or chroma intra prediction mode IntraPredModeC) input from the prediction parameter derivation unit 320 and reference pixels read from the reference picture memory 306. In a case that the prediction mode predMode indicates an inter prediction mode, the inter prediction image generation unit performs an inter prediction by using an inter prediction parameter input from the prediction parameter derivation unit 320 and reference pixels read from the reference picture memory 306.

[0063] Specifically, the prediction image generation unit 308 reads, from the reference picture memory 306, a neighbouring block in a predetermined range from a target block on a target picture. The predetermined range is neighbouring blocks on the left, the top left, the top, and the top right of the target block, and the region referred to is different depending on the intra prediction mode.

[0064] The prediction image generation unit 308 generates a prediction image of the target block with reference to the read decoded pixel values and the prediction mode indicated by predMode, IntraPredModeY and / or IntraPredModeC. The prediction image generation unit 308 outputs the generated prediction image of the block to the addition unit 312.

[0065] The generation of the prediction image based on the intra prediction mode is described below. In the Planar prediction, the DC prediction, and the Angular prediction, a decoded peripheral region adjacent to (proximate to) the prediction target block is configured as a reference region R. Then, the pixels on the reference region R are extrapolated in a specific direction to generate the prediction image. For example, the reference region R may be configured as an L-shaped region including the left and top (or further, top left, top right, bottom left) of the prediction target block.

[0066] Intra prediction image generation unit 310 A configuration of the intra prediction image generation unit 310 is described using FIG. 5. The intra prediction image generation unit 310 includes a reference sample filter unit 3103 (second reference image configuration unit), an intra prediction unit 3104), and a prediction image corrector 3105 (prediction image corrector, filter switching unit, weight coefficient changing unit).

[0067] Based on each reference pixel (unfiltered reference image) on the reference region R, a filtered reference image generated by applying a reference pixel filter (first filter), and the intra prediction mode, the intra prediction unit 3104 generates a prediction image of the target block, and outputs the generated image to the prediction image corrector 3105. The prediction image corrector 3105 corrects the prediction image in accordance with the intra prediction mode, and outputs a corrected prediction image.

[0068] Hereinafter, the units included in the intra prediction image generation unit 310 is described.

[0069] Reference sample filter unit 3103 The reference sample filter unit 3103 applies the reference pixel filter (first filter) to the unfiltered reference image to derive a filtered reference image s[x][y] at each position (x, y) on the reference region R, in accordance with the intra prediction mode. Specifically, a low pass filter is applied to the unfiltered reference image at each position (x, y) and its surroundings, and a filtered reference image is derived. Note that the low pass filter need not necessarily be applied in all the intra prediction modes, and the low pass filter may be applied in some intra prediction modes. Note that the filter applied to an unfiltered reference image on a reference region R in the reference sample filter unit 3103 is referred to as the “reference pixel filter (first filter)”, whereas a filter that corrects the prediction image in the prediction image corrector 3105 described below is referred to as a “boundary filter (second filter)”.

[0070] Configuration of intra prediction unit 3104 The intra prediction unit 3104 generates, based on the intra prediction mode, the unfiltered reference image, and the filtered reference pixel value, a prediction image (prediction pixel value, uncorrected prediction image) of the prediction target block, and outputs a generated image to the prediction image corrector 3105. The intra prediction unit 3104 includes a Planar prediction unit 31041, a DC prediction unit 31042, an Angular prediction unit 31043, an LM prediction unit 31044, an MIP prediction unit (Matrix-based Intra Prediction) 31045, a DIMD (Decoder side Intra Mode Derivation) prediction unit 31046, and a newMPMList (Most Probable Mode List) generation unit 31047 in the inside thereof. Also the intra prediction unit 3104 may include a TIMD (Template based Intra Mode Derivation) prediction unit 31048, shown in FIG. 5. The intra prediction unit 3104 selects a specific predictor in accordance with the intra prediction mode, and inputs an unfiltered reference image and a filtered reference image thereto. The relationship between the intra prediction mode and the corresponding predictor is as follows.

[0071] - Planar prediction ... Planar prediction unit 31041 - DC prediction ... DC prediction unit 31042 - Angular prediction ... Angular prediction unit 31043 - LM prediction ... LM prediction unit 31044 - MIP prediction ... MIP prediction unit 31045 - DIMD prediction ... DIMD prediction unit 31046 - TIMD prediction ... TIMD prediction unit 31047 Planar prediction The Planar prediction unit 31041 generates a prediction image q[x][y] by linearly adding multiple filtered reference images s[x][y] in accordance with the distance between the prediction pixel position and the reference pixel position, and outputs the generated image to the prediction image corrector 3105.

[0072] DC prediction The DC prediction unit 31042 derives a DC prediction value corresponding to the average value of the filtered reference image s[x][y], and outputs a prediction image q[x][y], which takes the DC prediction value as a pixel value.

[0073] Angular prediction The Angular prediction unit 31043 generates a prediction image q[x][y] using the filtered reference image s[x][y] in a prediction direction (reference direction) indicated by the intra prediction mode, and outputs the generated image to the prediction image corrector 3105.

[0074] LM prediction The LM prediction unit 31044 predicts the pixel value of the chroma based on the pixel value of luma. More specifically, a linear model is used to generate a prediction chroma image (Cb, Cr) based on the decoded luma image. As an example of LM prediction, there is a CCLM (cross component linear model prediction) prediction. CCLM prediction is a prediction method using a linear model to predict chroma from luma to same block.

[0075] MIP prediction The MIP prediction unit 31045 generates a prediction image q[x][y] by the product sum operation on the reference sample s[x][y] and the weight matrix derived from the neighboring region, and outputs the prediction image q[x][y] to the prediction image corrector 3105.

[0076] DIMD prediction The DIMD prediction unit 31046 employs a prediction method that generates prediction images using decoder-side derived (not signaled) intra prediction modes. During the encoding and decoding process, the DIMD method utilizes neighborhood information to derive multiple suitable intra prediction modes for the target block, along with the corresponding weights for each mode. Subsequently, the DIMD prediction unit 31046 utilizes these intra prediction modes to generate prediction images.

[0077] TIMD prediction The TIMD method is an intra prediction technique used to generate prediction images using derived intra prediction modes. The TIMD prediction unit 31047 is derives suitable intra prediction modes for the target block by assuming that the direction and appropriate intra prediction mode of the template area (TA) neighboring the target block should be similar to the direction and appropriate intra prediction mode of the target block. Specifically, the unit derives one or more intra prediction modes for the the template area (TA) by trying an intra prediction using images from the reference region (Reference Area of Template Area, RATA) near the template area (TA) to generate prediction images (tpredSamples). If the cost (such as the absolute difference sum, SAD) between tpredSamples and the reconstructed pixels (tempSamples) of the TA region is small, the intra prediction mode candidates are selected as timd intra prediction modes. The TIMD prediction unit 31047. The TIMD prediction unit 31047 employs these timd intra prediction modes to generate prediction image for the current block.

[0078] Configuration of prediction image corrector 3105 The prediction image corrector 3105 corrects the prediction image output from the intra prediction unit 3104 in accordance with the intra prediction mode. Specifically, the prediction image corrector 3105 derives, by performing weighted addition (weighted-averaging) on the unfiltered reference image and the prediction image for each pixel of the prediction image, in accordance with the distance between the reference region R and the target prediction pixel, the prediction image (corrected prediction image) Pred in which the prediction image is modified. Note that in some intra prediction modes (for example, Planar prediction, DC prediction, or the like), the prediction image corrector 3105 may not correct the prediction image, and the output of the intra prediction unit 3104 may be used as the prediction image.

[0079] (TIMD prediction) The parameter decoding unit 302 decodes signaled data to determine the TIMD flag (timd_flag) for each block. A block can be a Coding Unit (CU), Transform Unit (TU), sub-block, etc. If the timd_flag for the target block is 0, then the parameter decoding unit 302 decodes syntax elements related to intra prediction modes. However, if timd_flag is 1, the parameter decoding unit 302 may skip decoding syntax elements related to intra prediction modes from the encoded data. When timd_flag is 1, the prediction image of the current block is derived using the TIMD method, which may calculate timdMode, timdSecondMode, timdNonAngMode, timdWeight1, timdWeight2, and timdWeight3 based on the surrounding samples of the current block. The TIMD prediction image is then derived based on these parameters.

[0080] TIMD prediction unit 31047 FIG. 6 shows the structure of the TIMD prediction unit 31047 in this embodiment.

[0081] The TIMD prediction unit 31047 comprises the Reference Sample Derivation Unit 4701, Template Derivation Unit 4702, Weights Derivation Unit 4703, Intra Prediction Unit 4704, and Prediction Mode Derivation Device 4710. The Prediction Mode Derivation Device 4710 consists of the Candidate Derivation Unit 4711 and the Intra Prediction Mode Derivation Unit 4717. The Intra Prediction Mode Derivation Unit 4717 is composed of the Template Prediction Image Generation Unit 4713, the Template Cost Derivation Unit 4714, and the Comparison Unit 4715. TIMD prediction unit 31047 executes the following steps: (STEP1) Generate tpredSamples for the template area using the specified intra prediction mode and the reference area RATA.

[0082] (STEP1-1) Generate tpredSamples for all candidate modes.

[0083] (STEP1-2) Calculate the cost values corresponding to the difference between each generated tpredSamples (prediction image of the template area) and tempSamples (reconstructed image of the template area).

[0084] (STEP2) Choose the candidate modes with the minimum cost, i.e., the intra prediction mode corresponding to the tpredSamples deemed to have the highest prediction accuracy, as the prediction mode for TIMD.

[0085] (STEP3) Generate the prediction image using the selected intra prediction mode.

[0086] The processing of (STEP1)~(STEP3) is described in detail below: (Reference Area and Template Area) FIG. 7 illustrates the template area (TA) and the reference area (RATA) used in TIMD method. The template area (TA) corresponds to the region adjacent to the current block, while the reference area (RATA) is used as a reference when generating the template prediction image (tpredSamples). The tpredSamples will be compared to the reconstructed image (tempSamples) of the template area to determine the cost. The internal prediction mode and weights of TIMD are determined based on the cost, and the prediction result is obtained accordingly.

[0087] Template Derivation Unit 4702 The Template Derivation Unit 4702 exports the template image tempSamples. FIG. 7 shows the spatial relationship between the template area TA and the current block. The template area TA consists of a L-shaped region with already decoded pixels, represented by recSamples. The template area can be subdivided into two parts: the above part and left part. Given that the coordinates of the above-left corner pixel of the current block are denoted as (x0, y0), the template area can be defined as follows: (Above template area) tempSamples[i][j] = recSamples[x0+i][y0+j] (i=0..cbWidth-1, j=-tH..-1) (Left template area) tempSamples[i][j] = recSamples[x0+i][y0+j] (i=-tW..-1, j=0..cbHeight-1) The region on recSamples used for deriving tempSamples is represented by the set of coordinates (i, j). Here, tW and tH denote the width and height of the template area, respectively. tW and tH may be positive integers greater than 0, such as 1, 2, 3, 4, etc.

[0088] The Reference Sample Derivation Unit 4701 The Reference Sample Derivation Unit 4701 extracts reference samples refUnit for the reference area RATA. This operation may alternatively be performed by the reference sample filtering unit 3103.

[0089] refUnit[x][y] = recSamples[x0+x][y0+y] Where x=-rW-1, y=-1-rH..refH-1, x=-rW..refW-1, y=-1-rH. Here, rW and rH represent the width and height of the RATA region. In FIG. 7, tW=1, tH=1. refW=2*cbWidth, refH=2*cbHeight. The Reference Sample derivation Unit 4701 may apply filtering to the reference samples refUnit[x][y] to derive reference samples p[x][y].

[0090] Prediction Mode Derivation Device 4710 The Prediction Mode Derivation Device 4710 consists of the Candidate Derivation Unit 4711 and the Intra Prediction Mode Derivation Unit 4717.

[0091] Candidate Derivation Unit 4711 The Candidate Derivation Unit 4711 initially derives candidate lists candList1, candList2, and candList3 from the adjacent and non-adjacent blocks to the target block. candList1 may include angular prediction modes, planar prediction mode, and DC prediction mode from MPM list, and intra prediction modes derived by the DIMD method. candList2 may include extended angular prediction modes, with indices numbered [-1,-14] and [67,80] as shown in FIG. 3. candList3 may include EIP (extrapolation-based intra prediction) merge modes.

[0092] When deriving candList3, both adjacent and non-adjacent blocks of the current block are used. If a neighbouring block with top left location being (xNb, yNb), is predicted using the EIP method (e.g. EipFlag[xNb][yNb] == 1), spatial adjacent, spatial non-adjacent, temporal and history candidates are added to candList3. As shown in FIG. 8, spatial adjacent blocks of the current block include A0, A1, B0, B1, B2, etc., located at the bottom-left, left, above-right, above, and above-left of the current block, respectively. Here, the coordinates of the pixel in top-left corner of the current block are (xCb, yCb), and the width and height of the current block are cbWidth and cbHeight, respectively.

[0093] A0: (xCb-1, yCb+cbHeight) A1: (xCb-1, yCb+cbHeight-1) B0: (xCb+cbWidth, yCb-1) B1: (xCb+cbWidth-1, yCb-1) B2: (xCb-1, yCb-1) As illustrated in FIG. 9, there are a total of 18 non-adjacent blocks of the current block. The non-adjacent blocks include blocks containing the following pixels: (xCb-cbWidth-1, yCb+2*cbHeight-1) (xCb-2*cbWidth-1, yCb+3*cbHeight-1) (xCb-3*cbWidth-1, yCb+4*cbHeight-1) (xCb-4*cbWidth-1, yCb+5*cbHeight-1) (xCb-cbWidth-1, yCb-cbHeight / 2) (xCb-2*cbWidth-1, yCb-cbHeight / 2) (xCb-3*cbWidth-1, yCb-cbHeight / 2) (xCb-cbWidth-1, yCb-cbHeight-1) (xCb-2*cbWidth-1, yCb-2*cbHeight-1) (xCb-3*cbWidth-1, yCb-3*cbHeight-1) (xCb-4*cbWidth-1, yCb-4*cbHeight-1) (xCb+cbWidth / 2, yCb-cbHeight-1) (xCb+cbWidth / 2, yCb-2*cbHeight-1) (xCb+cbWidth / 2, yCb-3*cbHeight-1) (xCb+2*cbWidth-1, yCb-cbHeight-1) (xCb+3*cbWidth-1, yCb-2*cbHeight-1) (xCb+4*cbWidth-1, yCb-3*cbHeight-1) (xCb+5*cbWidth-1, yCb-4*cbHeight-1) FIG. 9 is an example in the case of (xCb, yCb) = (0, 0).

[0094] The exploration order of these blocks is not specified.

[0095] Intra Prediction Mode Derivation Unit 4717 Intra Prediction Mode Derivation Unit 4717 is comprised of the Template Prediction Image Generation Unit 4713, the Template Cost Derivation Unit 4714, and the Comparison Unit 4715. The input to the Intra Prediction Mode Derivation Unit 4717 consists of candList1[], candList2[], and candList3[] from the outputs of the Candidate Derivation Unit 4711. For the inputs candList1[], candList2[], and candList3[], the Intra Prediction Mode Derivation Unit 4717 merges candList1[] and candList2[] into a candidate prediction mode list named timdOriCandList[], and uses candList3[] as timdEipCandList[]. Within the Intra Prediction Mode Derivation Unit 4717, there is a loop / iterative proecss that iterates over each candidate prediction mode present in timdOriCandList[], timdAddiAngCandList[], and timdEipCandList[]. The timdAddiAngCandList[] are derived using the loop / iterative process based on the elements in timdOriCandList[]. The exploration / scanning process starts with exploring / scanning the elements in timdOriCandList[], followed by exploring the elements in timdAddiAngCandList[], and finally, exploring the elements in timdEipCandList[]. In each iteration, the unique candidate is added into the candidate list in which unique is checked whether the target exploring candidate exists in the candidate list, if not exist (unique is TRUE), the target one is inserted to the candidate list. Otherwise (if exist, unique is FALSE), the target one is not inserted to the candidate list.

[0096] For each candidate prediction mode, the unit generates the prediction image for the template area, calculates the cost based on the differences between the prediction image and the reconstructed image in the template area, and compares the costs of prediction images to determine the best (the least cost) intra prediction mode as timdMode, the second best (the second least cost) intra prediciton mode as timdSecondMode, and stores timdMode, timdSecondMode and correspoding costs as timdCost1 (the cost of timdMode) and timdCost2 (the cost of timdSecondMode). These specific operations are carried out within the Template Prediction Image Generation Unit 4713, the Template Cost Derivation Unit 4714, and the Comparison Unit 4715.

[0097] Template Prediction Image Generation Unit 4713 The Template Prediction Image Generation Unit 4713 generates the prediction image (tpredSamples) for the template area based on the pixels in the reference area and the specified prediction modes. The Template Prediction Image Generation Unit 4713 may generate prediction image based on the prediction image (TIMD prediction image) using timd intra prediciton mode (timdMode, timdSecondMode) and the prediction image (EIP prediction image) using EIP. The prediction image is derived by weighting TIMD prediction images and EIP prediction image. The input to this unit includes the reference area pixels refUnit[][] output by the Reference Sample Derivation Unit 4701, as well as timdOriCandList[] and timdEipCandList[]. The Template Prediction Image Generation Unit 4713 inputs refUnit[][] and each candidate from timdOriCandList[] and timdEipCandList[] into the Intra prediction unit 4704. The Intra prediction unit 4704 calculates tpredSamples based on the inputs and returns it to the Template Prediction Image Generation Unit 4713.

[0098] Intra prediction unit 4704 The Intra prediction unit 4704 generates the intra prediction image within the specified region based on the input reference pixels and the specified intra prediction mode. In the TIMD method, it generates the prediction image tpredSamples for the template area.

[0099] Template Cost Derivation Unit 4714 The Template Cost Derivation Unit 4714 calculates the difference between tpredSamples and tempSamples (reconstructed image of the template area). This difference can be represented using SATD cost or SAD cost, or other metrics. The Template Cost Derivation Unit 4714 sets the current intra prediction mode from the TIMD candidate intra prediction modes, corresponding to the current tpredSamples as curMode and sets the calculated cost (difference value) as curModeCost. curMode and curModeCost are then output to the Comparison Unit 4715.

[0100] Comparison Unit 4715 The Comparison Unit 4715 updates timdMode, timdSecondMode, timdNonAngMode, timdCost1, timdCost2, and timdCost3 based on the input curMode and curModeCost. In the initial stage (i.e., the first time loop in the Intra prediction mode derivation unit 4717, exploring the first element in timdOriCandList[]), timdMode, timdSecondMode and timdNonAngMode are set to be planar mode, and timdCost1, timdCost2 and timdCost3 and their initial costs are set to be a predefined maximum value, e.g. MAX_UINT64, where MAX_UINT64 represents the maximum value that an unsigned 64-bit integer can hold. Then, for each loop, curMode and curModeCost are processed as follows: (Embodiment1) (Embodiment2) In another embodiment, an alternative method is described below. After all candidate modes in timdOriCandList have been explored, the following operations are performed. A list timdAddiAngCandList[] with a maximum length of 4 is generated based on the current timdMode and timdSecondMode. The candidate modes in this list are numbered as timdMode-1, timdMode+1, timdSecondMode-1, and timdSecondMode+1, where timdMode-1, timdMode+1, timdSecondMode-1, and timdSecondMode+1 may belong to the interval [2, NMAX]. Then, for each candidate mode belonging to timdAddiAngCandList, the following operations are performed with the obtained curMode and curModeCost: Finally, for each candidate mode belonging to timdEipCandList, the following operations are performed with the obtained curMode and curModeCost: After exploring all candidate lists, the Intra Prediction Mode Derivation Unit 4717 outputs a set of intra prediciotn modes and corresponding costs, namelytimdMode, timdSecondMode, timdNonAngMode, timdCost1, timdCost2, and timdCost3, to the Weights Derivation Unit 4703.

[0101] Weights Derivation Unit 4703 Weights Derivation Unit 4703 calculates timdWeight1, timdWeight2, and timdWeight3 based on timdCost1, timdCost2, and timdCost3. The calculation process is as follows: sumWeight is a positive integer that is a power of 2, such as 32, 64, 128, etc.

[0102] These weights are then output from the Weights Derivation Unit 4703.

[0103] <Fusion of two> The prediction result of the target block may be generated by two timd intra prediction mode fusion (weighting). The timd intra prediction mode may be the best one (timdMode) and the second best (timdSecondMode). Using the intra prediction unit 4704 or intra prediction image generation unit 310, generate the prediction images predImage1 and predImage2 for the target block area corresponding to the intra prediction modes timdMode, timdSecondMode <Fusion of three> The prediction result of the target block may be generated by three timd intra prediction fusion. The timd intra prediction mode may be the best one (timdMode), the second best (timdSecondMode) and timdNonAngMode. Using the intra prediction unit 4704 or intra prediction image generation unit 310, generate the prediction images predImage1, predImage2 and predImage3 for the target block area corresponding to the intra prediction modes timdMode, timdSecondMode and timdNonAngMode. Only when timdMode and timdSecondMode is not the same with timdNonAngMode, the prediction result is made by three modes fusion.

[0104] predImage[x][y] = (predImage1[x][y] * timdWeight1 + predImage2[x][y] * timdWeight2 + predImage3[x][y] * timdWeight3 + offset) >> shiftVal where shiftVal is a positive integer, such as 5, 6, 7, etc.

[0105] offset = 1<<(shiftVal-1) Or weights can be calculated as follows: score1 = timdCost2 * timdCost3 score2 = timdCost1 * timdCost3 score3 = timdCost1 * timdCost2 sum = score1 + score2 + score3 baseWeight = 32, 64 or 128, etc timdWeight1 = (score1 / sum) * baseWeight timdWeight2 = (score2 / sum) * baseWeight timdWeight3 = baseWeight - weight1 - weight2 (Combination of TIMD and MRL (multi reference line)) (Multi reference line) The basic intra prediction calculates the prediction value of the current block by using only the most neighboring left column and the most neighboring upper row of the current block as reference samples. MRL (Multi-Reference Line) extends the reference. In MRL, N (N>1) reference lines (e.g. N = 6, N can be 4, 5, 6) are set and stored in the reference line list MRLList, with MRLList=[0,1,3,5,7,12]. Here MRLList[k] contains the distance table from the current block, which respresent MRLList[k]+1 column on the left (x = xC - MRLList[k]-1) and the MRLList[k]+1 row above the current block (y = yC - MRLList[k]-1) as reference. Specifically, MRLList[0] represents using the first column on the left (x = xC - 1) and the first row above the current block (y = yC - 1) as reference, MRLList[2] represents using the second column on the left and the second row above the current block as reference, and so on, MRLList[5] represents using the 13th column on the left (x = xC - 13) and the 13th row (y = yC - 13) above the current block as reference. FIG. 15 shows the positional relationship between the current block and each reference line. It is worth noting that when the current block is located in the first row / column of the CTU, MRL cannot be used. The Combination of TIMD and MRL means both TIMD and MRL are used simultaneously. The TIMD parameters (timdMode, timdSecondMode, timdNonAngMode, timdWeight1, timdWeight2, and timdWeight3) are employed to predict the current block from the specified reference lines (MRLList[]).The syntax element intra_luma_ref_idx is used to select MRLList[]. refIdx = (cIdx==0) ? MRLList[intra_luma_ref_idx] : 0. cIdx is the color component index in which 0, 1, 2 may correspond to Y, Cb, Cr respectively.

[0106] The Reference Sample Derivation Unit 4701 extracts reference samples refUnit for the reference area.

[0107] refUnit[x][y] = recSamples[x0+x][y0+y] Where x = -1-refIdx, y = -1-refIdx..refH-1 and x = -refIdx..refW-1, y = -1- refIdx. The Reference Sample derivation Unit 4701 may apply filtering to the reference samples refUnit[x][y] to derive reference samples p[x][y], with x=-1-refIdx, y=-1-refIdx..refH-1 and x=-refIdx..refW-1, y=-1-refIdx. The prediction image generation unit 308 derives prediction image, predSamples as follows.

[0108] intraPredAngle is derived using angleTable[] and IntraPredModeY as intraPredAngle = angleTable[IntraPredModeY].

[0109] (Syntax improvement) This invention prohibits the combination of TIMD and MRL. Modifications have been made to the encoding and decoding syntax elements of the TIMD method, as shown in FIG. 16. When timd_flag is 0, it indicates that the current block is not predicted using the TIMD method, and the parameter decoding unit 302 decodes syntax elements related to intra prediction modes. In this case, the values of MRL_mode are irrelevant to the TIMD method. When timd_flag is 1, it signals that the current block is predicted using the TIMD method. In this case, MRL_mode is encoded and decoded. MRL_mode has six possible values, each corresponding to six reference lines. Specifically, when the binValue of MRL_mode is 0, 10, 110, 1110, 11110, and 11111, it represents using the 1st, 2nd, 4th, 6th, 8th, and 13th lines adjacent to the current block as reference, respectively. In this invention, due to the prohibition of the combination of TIMD and MRL, the encoding and decoding operations for MRL_mode are not performed when timd_flag is 1.

[0110] FIG. 17 shows syntax examples for TIMD and MRL exclusion. The parameter decoding unit 302 decodes timd_flag. If timd_flag == FALSE (e.g. 0), the parameter decoding unit 302 decodes intra_luma_ref_idx from the coded video data. If timd_flag == TRUE (e.g. 1), the intra_luma_ref_idx doesn’t present in the coded video data. If the syntax element of intra_luma_ref_idx is not present, intra_luma_ref_idx is infered to be 0, which spcifies MRL is not used (only first column or first row is used). If intra_luma_ref_idx is equal to 0, The parameter decoding unit 302 decodes intra_mpm_flag. If intra_luma_ref_idx is not equal to 0, intra_mpm_flag may not present in the coded video data. If intra_mpm_flag is not present, intra_mpm_flag is infered to be 1, which specifies MPM is always used.

[0111] (Combination of TIMD and ISP (Intra Sub-Partitions)) (Intra Sub-Partitions) ISP (Intra Sub-Partitions) is a tool for intra prediction. When ISP is available, the current block is divided vertically or horizontally into 2 or 4 sub-blocks based on the size of the current block. FIG. 13 illustrates the current block and its sub-blocks. The minimum size of a block that allows the use of the ISP mode is 4x8 (or 8x4), as each sub-block is required to have at least 16 samples / pixels. Therefore, if the block is less than or equal to 4x8 (or 8x4), it is divided into 2 sub-blocks (NumIntraSubPartitions = 2); otherwise, it is divided into 4 sub-blocks (NumIntraSubPartitions = 4). In the encoder, the sub-blocks are encoded sequentially from top to bottom (or left to right). After encoding the previous sub-block, inverse transform and quantization are performed, and the prediction pixels are added to generate the reconstructed pixels for the prediction of the next sub-block. The combination of TIMD and ISP refers to predict each sub-block using the TIMD method, with each sub-block using the same TIMD parameters (timdMode, timdSecondMode, timdNonAngMode, timdWeight1, timdWeight2, and timdWeight3).

[0112] (Syntax improvement) This invention prohibits the combination of TIMD and ISP. Modifications have been made to the encoding and decoding syntax elements of the TIMD method, as shown in FIG. 14. When timd_flag is 0, it indicates that the current block is not predicted using the TIMD method, then the parameter decoding unit 302 decodes syntax elements related to intra prediction modes. In this case, the values of isp_flag (intra_subpartitions_mode_flag) and isp_mode (intra_subpartitions_split_flag) are irrelevant to the TIMD method. When timd_flag is 1, it signals that the current block is predicted using the TIMD method. In this case, isp_flag is encoded and decoded. If isp_flag is 0, it means the current block is not partitioned, indicating that ISP is not used. If isp_flag is 1, it means ISP is applied to the current block. When isp_flag is 1, isp_mode is encoded and decoded, where isp_mode being 0 or 1 represents horizontal or vertical partitioning of the current block. In this invention, due to the prohibition of the combination of TIMD and ISP, the encoding and decoding operations for isp_flag and isp_mode are not performed when timd_flag is 1.

[0113] FIG. 17 also shows syntax examples for TIMD and ISP exclusion. The parameter decoding unit 302 decodes timd_flag. If timd_flag == FALSE (e.g. 0), the parameter decoding unit 302 decodes intra_subpartitions_mode_flag from the coded video data. If timd_flag == TRUE (e.g. 1), the intra_subpartitions_mode_flag may not present in the coded video data. If the syntax element of intra_subpartitions_mode_flag is not present, intra_subpartitions_mode_flag is infered to 0, which specifies ISP is not applied.

[0114] The parameter decoding unit 302 derives IntraSubPartitionsSplitType as follows : Here, IntraSubPartitionsSplitType = 0, 1, 2 corresponds to ISP_NO_SPLIT, ISP_HOR_SPLIT, ISP_VER_SPLIT.

[0115] If intra_subpartitions_mode_flag is equal to 0, IntraSubPartitionsSplitType is set equal to be 0.

[0116] Otherwise, the IntraSubPartitionsSplitType is set equal to be 1 + intra_subpartitions_split_flag.

[0117] The parameter decoding unit 302 derives the number of subblock NumIntraSubPartitions as follows.

[0118] - If IntraSubPartitionsSplitType is equal to ISP_NO_SPLIT, NumIntraSubPartitions is set equal to 1.

[0119] - Otherwise, if one of the following conditions is TRUE, NumIntraSubPartitions is set equal to 2: 　- cbWidth is equal to 4 and cbHeight is equal to 8, 　- cbWidth is equal to 8 and cbHeight is equal to 4.

[0120] - Otherwise, NumIntraSubPartitions is set equal to 4.

[0121] (DIMD prediction) The parameter decoding unit 302 decodes signaled data to determine the DIMD flag (dimd_flag) for each block. A block may be a Coding Unit (CU), Transform Unit (TU), sub-block, etc. If the dimd_flag for the target block is 0, then the parameter decoding unit 302 decodes syntax elements related to intra prediction modes. However, if dimd_flag is 1, the parameter decoding unit 302 may skip decoding syntax elements related to intra prediction modes from the encoded data. When dimd_flag is 1, the prediction image of the current block is derived using the DIMD method, which may calculate dimdMode1, dimdMode2, dimdMode3, dimdMode4, dimdMode5, dimdMode6, dimdWeight1, dimdWeight2, dimdWeight3, dimdWeight4, dimdWeight5, and dimdWeight6 based on the surrounding samples of the current block. The DIMD prediction image is then derived based on these parameters. FIG. 12 shows the structrue of DIMD prediction unit 31046.

[0122] (DIMD reference area) (Reference sample derivation unit 310460) The reference sample derivation unit 310460 derives reference samples from neibouring samples of the target block. FIG. 11(a) shows the spatial relationship between the reference samples and the current block. The reference samples have two parts RDL and RDT. Set the coordinates of above-left corner pixel in current block is (x, y). The area of RDL is the pixel with coordinate of (x + i, y + j), x=-3..-1, y=-3..cbHeight. The area of RDT is the pixel with coordinate of (x + i, y + j), x=-3..cbWidth, y=-3..-1. The RDTL is the combination of RDL and RDT.

[0123] (Histogram generation) (Gradient derivation unit 310461) The gradient derivation unit 310461 uses 3x3 filter for gradient derivation. FIG. 11(b) show the 3x3 filter. The angular mode derivation unit 310462 derives gradient Dx and Dy from the each point P of the RDTL of the target block, derives modeVal and conducts histogram counting operation. The target point P is the pixel with coordinates of (x + i, y + j), i=-2, j=-2..cbHeight-1 or i=-2..cbWidht-1, j=-2.

[0124] The gradient derivation unit 310461 derives pixel gradient Dx and Dy using the pixel values P[x][y] for a given position (x, y) in the reference samples.

[0125] Dx = P[x-1][y+1] + 2*P[x][y+1] + P[x+1][y+1] - P[x-1][y-1] - 2*P[x][y-1] - P[x+1][y-1] Dy = P[x-1][y-1] + 2*P[x-1][y] + P[x-1][y+1] - P[x+1][y-1] - 2*P[x+1][y] - P[x+1][y+1] The gradient derivation unit 310461 derives signx, signy, xgty and quadrant as follows.

[0126] absx = abs(Dx) absy = abs(Dy) signx = Dx < 0 ? 1 : 0 signy = Dy < 0 ? 1 : 0 xgty = absx > absy ? 1 : 0 quadrant = xgty ? ( (signx^signy) ? 1 : 0 ) : ( (signx^signy) ? 2 : 3) Here, inequality sign (>, <) may be replaced by (>=, <=). The angular information may be derived from the signx, signy, and xgty. ^ means an XOR calculation. The quadrant is represented by the value from 0 to 3, {Ra, Rb, Rc, Rd} = {0, 1, 2, 3}. The value of the quadrant is not limited to the above.

[0127] The angular mode derivation unit 310462 derives iRatio.

[0128] iRatio = R_UNIT * absy / absx R_UNIT is the exponential power of 2 (1<<shiftR), e.g. R_UNIT = 65536 when shiftR = 16. The division may be replaced with “multiplied by its reciprocal”. The reciprocal is derived by a LUT.

[0129] e.g. LUT[k] = R_UNIT / k, iRatio = absy * LUT[absx] The angular mode derivation unit 310462 converts the derived pixel gradient to an angular prediction mode, modeVal by seaching angular mode corresponding to the iRatio.

[0130] The angular mode derivation unit 310462 counts the number of angular prediction mode modeVal derived from the reference region. It may build a histogram HistMode[] as follows.

[0131] HistMode[modeVal] += N, N may be 1 or absx + absy. If HistMode[modeVal] += absx + absy, then HistMode stores the sum of gradients for all target pixels P corresponding to the angular mode.

[0132] (angular modes derivation) Angular mode derivation unit 310462 derives angular mode from HistMode. dimdMode1, dimdMode2, dimdMode3, dimdMode4, and dimdMode5 are derived from HistMode, representing the angular modes with the highest, second-highest, third-highest, fourth-highest, and fifth-highest gradient sums in HistMode, respectively.

[0133] dimdMode1 = modeVal (HistMode[modeVal] have the hightst value in HistMode) dimdMode2 = modeVal (HistMode[modeVal] have the second-hightst value in HistMode) dimdMode3 = modeVal (HistMode[modeVal] have the third-hightst value in HistMode) dimdMode4 = modeVal (HistMode[modeVal] have the fourth-hightst value in HistMode) dimdMode5 = modeVal (HistMode[modeVal] have the fifth-hightst value in HistMode) The corresponding gradient sums are stored in gSum1, gSum2, gSum3, gSum4, and gSum5. The corresponding weights, dimdWeight1, dimdWeight2, dimdWeight3, dimdWeight4, and dimdWeight5 are exported as follows: sumWeight is a positive integer that is a power of 2, such as 32, 64, 128, etc.

[0134] sum = gSum1 + gSum2 + gSum3 + gSum4 + gSum5 dimdweight1 = gSum1 / sum * (sumWeight- KK) dimdweight2 = gSum2 / sum * (sumWeight- KK) dimdweight3 = gSum3 / sum * (sumWeight- KK) dimdweight4 = gSum4 / sum * (sumWeight- KK) dimdweight5 = sumWeight - KK - dimdweight1 - dimdweight2 - dimdweight3 - dimdweight4.

[0135] KK may be 16 or a positive interger value.

[0136] (non-angular mode derivation) (Non-angular mode derivation unit 310464) Non-angular mode derivation unit 310464 exports the non-angular mode required in the DIMD method. First, a mode list is generated, which includes PLANAR, DC and EIP merge modes. The EIP merge modes are obtained from both adjacent and non-adjacent blocks relative to the current block. The modes in the mode list are selected using template matching cost, with the template positions illustrated as TA in FIG. 7. The resulting mode is named dimdNonAngMode and is assigned a fixed weight, dimdNonAngModeWeight, which is a positive integer less than sumWeight. It is important to note that the value of dimdNonAngModeWeight must remain consistent with KK.

[0137] (prediction image generation) (Prediction image generation unit 310463) The prediction image for the current block is obtained by calculating the weighted sum of six intra prediction modes derived by DIMD (5 angular modes and 1 non-angular mode). First, the corresponding prediction images predImage1, predImage2, predImage3, predImage4, predImage5, and predImageNonAng are generated based on dimdMode1, dimdMode2, dimdMode3, dimdMode4, dimdMode5, and dimdNonAngMode. The prediction result is then calculated as follows: The inverse quantization and inverse transform processing unit 311 performs inverse quantization on a quantization transform coefficient input from the prediction parameter derivation unit 320 to calculate a transform coefficient. This quantization transform coefficient is a coefficient obtained by performing a frequency transform such as a Discrete Cosine Transform (DCT), a Discrete Sine Transform (DST), or the like on prediction errors to quantize in coding processing. The inverse quantization and inverse transform processing unit 311 performs an inverse frequency transform such as an inverse DCT, an inverse DST, or the like on the calculated transform coefficient to calculate a prediction error. The inverse quantization and inverse transform processing unit 311 outputs the prediction error to the addition unit 312.

[0138] The addition unit 312 adds the prediction image of the block input from the intra prediction image generation unit 310 and the prediction error input from the inverse quantization and inverse transform processing unit 311 for each pixel and generates 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 image to the loop filter 305.

[0139] Configuration of video coding apparatus Next, a configuration of the video coding apparatus 11 according to the present embodiment is described. FIG. 10 is a block diagram illustrating a conuration of the video coding apparatus 11 according to the present embodiment. The video coding apparatus 11 is configured to include a prediction image generation unit 101, a subtraction unit 102, a transform and quantization processing unit 103, an inverse quantization and inverse transform processing unit 105, an addition unit 106, a loop filter 107, a prediction parameter memory (a prediction parameter storage unit, a frame memory) 108, a reference picture memory (a reference image storage unit, a frame memory) 109, a coding parameter determination unit 110, a parameter coding unit 111, prediction parameter derivation unit 120, and an entropy coding unit 104.

[0140] The prediction image generation unit 101 generates a prediction image for each CU that is a region obtained by splitting each picture of the image T. The operation of the prediction image generation unit 101 is the same as that of the intra prediction image generation unit 310 already described, and thus descriptions thereof is omitted.

[0141] The subtraction unit 102 subtracts a pixel value of the prediction image of the block input from the prediction image generation unit 101 from a pixel value of the image T to generate a prediction error. The subtraction unit 102 outputs the prediction error to the transform and quantization processing unit 103.

[0142] The transform and quantization processing unit 103 calculates a transform coefficient by performing a frequency transform on the prediction error input from the subtraction unit 102, and derives a quantization transform coefficient by quantization. The transform and quantization proceessing unit 103 outputs the quantization transform coefficient to the entropy coding unit 104 and the inverse quantization and inverse transform processing unit 105.

[0143] The inverse quantization and inverse transform processing unit 105 is the same as the inverse quantization and inverse transform processing unit 311 (FIG. 4) in the video decoding apparatus 31, and descriptions thereof are omitted. The calculated prediction error is output to the addition unit 106.

[0144] To the entropy coding unit 104, the quantization transform coefficient is input from the transform and quantization processing unit 103, and coding parameters are input from the parameter coding unit 111. The entropy coding unit 104 performs entropy coding on split information, the prediction parameters, the quantization transform coefficient, and the like to generate and output the coding stream Te.

[0145] The parameter coding unit 111 instructs the entropy coding unit 104 to encode the prediction parameters and quantization coefficients, derived from the prediction parameter derivation unit 120.

[0146] The prediction parameter derivation unit 120 derives the syntax element from the parameters inputted from the coding parameter determination unit 110. Some parts of the prediction parameter derivation unit 120 have the same structure as the prediction parameter derivation unit 320.

[0147] The addition unit 106 adds a 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 and inverse transform processing unit 105 to each other for each pixel, and generates a decoded image. The addition unit 106 stores the generated decoded image in the reference picture memory 109.

[0148] The loop filter 107 applies a deblocking filter, an SAO, and an ALF to the decoded image generated by the addition unit 106. Note that the loop filter 107 need not necessarily include the above-described three types of filters, and may have a configuration of only the deblocking filter, for example.

[0149] The prediction parameter memory 108 stores the prediction parameters generated by the prediction parameter derivation unit 120 for each target picture and CU at a predetermined position. It may stores the transform coefficients created by the transform and quantization processing unit 103.

[0150] The reference picture memory 109 stores the decoded image generated by the loop filter 107 for each target picture and CU at a predetermined position.

[0151] The coding parameter determination unit 110 selects one set among multiple sets of coding parameters. A coding parameter refers to the above-mentioned QT, BT, or TT split information, the prediction parameter, or a parameter to be coded, the parameter being generated in association therewith. The prediction image generation unit 101 generates the prediction image by using these coding parameters.

[0152] The coding parameter determination unit 110 calculates, for each of the multiple sets, an RD cost value indicating the magnitude of an amount of information and a coding error. The RD cost value is, for example, the sum of a code amount and the value obtained by multiplying a coefficient λ by a square error. The coding parameter determination unit 110 selects a set of coding parameters of which cost value calculated is a minimum value. With this configuration, the entropy coding unit 104 outputs the selected set of coding parameters as the coding stream Te. The coding parameter determination unit 110 outputs the determined coding parameters in the parameter coding unit 111, the prediction parameter derivation unit 120, the prediction image generation unit 101.

[0153] Note that, some of the video coding apparatus 11 and the video decoding apparatus 31 in the above-described embodiment, for example, the entropy decoding unit 301, the parameter decoding unit 302, the loop filter 305, the intra prediction image generation unit 310, the inverse quantization and inverse transform processing unit 311, the addition unit 312, the prediction parameter derivation unit 320, the prediction image generation unit 101, the subtraction unit 102, the transform and quantization processing unit 103, the entropy coding unit 104, the inverse quantization and inverse transform processing unit 105, the loop filter 107, the coding parameter determination unit 110, and the parameter coding unit 111, the prediction parameter derivation unit 120, may be realized by a computer. In that case, this configuration may be realized by recording a program for realizing such control functions on a computer-readable recording medium and causing a computer system to read the program recorded on the recording medium for execution. Note that the “computer system” mentioned here refers to a computer system built into either the video coding apparatus 11 or the video decoding apparatus 31 and is assumed to include an OS and hardware components such as a peripheral apparatus. Furthermore, a “computer-readable recording medium” refers to a portable medium such as a flexible disk, a magneto-optical disk, a ROM, a CD-ROM, and the like, and a storage device such as a hard disk built into the computer system. Moreover, the “computer-readable recording medium” may include a medium that dynamically stores a program for a short period of time, such as a communication line in a case that the program is transmitted over a network such as the Internet or over a communication line such as a telephone line, and may also include a medium that stores the program for a fixed period of time, such as a volatile memory included in the computer system functioning as a server or a client in such a case. Furthermore, the above-described program may be one for realizing some of the above-described functions, and also may be one capable of realizing the above-described functions in combination with a program already recorded in a computer system.

[0154] Furthermore, a part or all of the video coding apparatus 11 and the video decoding apparatus 31 in the embodiment described above may be realized as an integrated circuit such as a Large Scale Integration (LSI). Each function block of the video coding apparatus 11 and the video decoding apparatus 31 may be individually realized as processors, or part or all may be integrated into processors. The circuit integration technique is not limited to LSI, and the integrated circuits for the functional blocks may be realized as dedicated circuits or a multi-purpose processor. In a case that with advances in semiconductor technology, a circuit integration technology with which an LSI is replaced appears, an integrated circuit based on the technology may be used.

[0155] The embodiment of the present disclosure has been described in detail above referring to the drawings, but the specific configuration is not limited to the above embodiments and various amendments may be made to a design that fall within the scope that does not depart from the gist of the present disclosure.

[0156] The embodiment of the present invention may be applied to a video decoding device that decodes encoded data of image data, and a video encoding device that generates encoded data from image data. In addition, the data structure of the encoded data is generated by the video encoding device and referenced by the video decoding device.

[0157] 31 Image decoding apparatus 301 Entropy decoding unit 302 Parameter decoding unit 310 Prediction image generation unit 3104 Intra prediction unit 31046 DIMD prediction unit 310460 Reference sample derivation unit 310461 Gradient derivation unit 310462 Angular mode derivation unit 310463 Prediction image generation unit 310464 Non-angular mode derivation unit 31047 TIMD prediction unit 4701 Reference sample derivation unit 4702 Template derivation unit 4710 Prediction Mode Derivation Device 4711 Candidate derivation unit 4717 Intra prediction mode derivation unit 4713 Template prediction image generation unit 4714 Template cost derivation unit 4715 Comparition unit 4703 Weights Derivation unit 4704 Intra prediction unit 311 Inverse quantization and inverse transform processing unit 312 Addition unit 11 Image coding apparatus 101 Prediction image generation unit 102 Subtraction unit 103 Transform and quantization processing unit 104 Entropy coding unit 105 Inverse quantization and inverse transform processing unit 107 Loop filter 110 Coding parameter determination unit 111 Parameter coding unit <Cross Reference> This patent application claims priority on JP Patent Application No. 2024-105379 filed on June 28, 2024, the entire contents of which are hereby incorporated by reference.

Claims

1. A video decoding apparatus for generating a prediction image, the video decoding apparatus comprising a TIMD prediction unit and a DIMD prediction unit that utilizes the weighted fusion results of single-frame intra prediction modes as the prediction output.

2. A video decoding apparatus of claim 1, wherein the video decoding apparatus further comprising a TIMD prediction unit configured to derive intra prediction modes, which include angular modes, DC mode, planar mode, and EIP merge modes.

3. A video decoding apparatus of claim 1, wherein the video decoding apparatus further comprising a DIMD prediction unit configured to derive intra prediction modes, which include angular modes, DC mode, planar mode, and EIP merge modes.

4. A video coding apparatus comprising a TIMD prediction unit and a DIMD prediction unit configured to derive a plural intra predicition modes and derive prediction image by weighted fusing these intra prediction modes.

5. A video coding and decoding device in which the combination of TIMD and ISP, as well as the combination of TIMD and MRL, are disabled, and when using the TIMD method, encoding and decoding operations are not performed on ISP and MRL.

Images