Template Selection for Intra Prediction in Video Coding

Abstract

A method for coding video data includes: a threshold; a selected template, where a mode index indicates which of a plurality of templates is the selected template, each of the templates includes a different set of reconstructed samples adjacent to a current coding unit (CU) of a current picture of the video data, and determining whether the selected template is permitted based on a comparison between the threshold and an amount of reference samples within the selected template; applying a cross-component model (CCM) mode to predict chroma samples of the current CU based on the reconstructed luma samples of the current CU and the reference samples within the selected template, based on a determination that the selected template is permitted and that the CCM mode should be used; and encoding or decoding the current CU based on the predicted chroma samples of the current CU.

Description

Technical Field

[0001]

[0001] This application claims the benefit of U.S. Patent Application No. 18 / 338,756, filed Jun. 21, 2023, and U.S. Provisional Patent Application No. 63 / 377,666, filed Sep. 29, 2022, and U.S. Provisional Patent Application No. 63 / 367,709, filed Jul. 5, 2022, the entire contents of each of which are incorporated herein by reference. U.S. Patent Application No. 18 / 338,756, filed Jun. 21, 2023, claims the benefit of U.S. Provisional Patent Application No. 63 / 377,666, filed Sep. 29, 2022, and U.S. Provisional Patent Application No. 63 / 367,709, filed Jul. 5, 2022.

[0002]

[0002] This disclosure relates to video encoding and video decoding.

Background Art

[0003]

[0003] Digital video capabilities can be incorporated into a wide range of devices, including digital televisions, digital direct broadcast systems, wireless broadcast systems, personal digital assistants (PDAs), laptop or desktop computers, tablet computers, e-book readers, digital cameras, digital recording devices, digital media players, video gaming devices, video game consoles, cellular or satellite radiotelephones, so-called "smartphones," video teleconferencing devices, video streaming devices, etc. Digital video devices implement video coding techniques such as those described in standards defined by MPEG-2, MPEG-4, ITU-T H.263, ITU-T H.264 / MPEG-4, Part 10, Advanced Video Coding (AVC), ITU-T H.265 / High Efficiency Video Coding (HEVC), ITU-T H.266 / Versatile Video Coding (VVC), and extensions of such standards, as well as proprietary video codecs / formats such as AOMedia Video1 (AV1) developed by the Alliance for Open Media. By implementing such video coding techniques, video devices may transmit, receive, encode, decode, and / or store digital video information more efficiently.

[0004]

[0004] Video coding techniques include spatial (intra-picture) prediction and / or temporal (inter-picture) prediction to reduce or remove redundancy inherent in a video sequence. In the case of block-based video coding, a video slice (e.g., a video picture or a portion of a video picture) may be partitioned into video blocks, which may also be referred to as coding tree units (CTUs), coding units (CUs), and / or coding nodes. Video blocks within an intra-coded (I) slice of a picture are encoded using spatial prediction with respect to reference samples in adjacent blocks within the same picture. Video blocks within an inter-coded (P or B) slice of a picture may use spatial prediction with respect to reference samples in adjacent blocks within the same picture or temporal prediction with respect to reference samples in other reference pictures. A picture may sometimes be referred to as a frame, and a reference picture may sometimes be referred to as a reference frame.

Summary of the Invention

[0005]

[0005] Generally, the present disclosure describes techniques for template selection in video coding. A video coder (e.g., a video encoder or a video decoder) may determine whether a selected template is permitted based on a comparison of a threshold with the amount of reference samples within the selected template. A mode index may indicate which of a plurality of templates is the selected template. Each of the templates includes a different set of reconstructed samples adjacent to the current coding unit (CU) of the current picture of the video data. Based on determining that the selected template is permitted and that the convolutional cross-component model (CCCM) mode should be used, the CCCM model is applied to predict the chroma samples of the current CU based on the reconstructed luma samples of the current CU and the reference samples within the selected template. Selecting a template from among a plurality of templates, as opposed to there being only one possible template, can improve coding efficiency and potentially result in a smaller bitstream.

[0006]

[0006] In one example, the present disclosure is a method for coding video data, the method comprising a threshold value and a selected template, a mode index indicating which of a plurality of templates is the selected template, each of the templates comprising a different set of reconstructed samples adjacent to a current coding unit (CU) of a current picture of the video data, determining whether the selected template is permitted based on a comparison with an amount of reference samples in the selected template, and based on determining that the selected template is permitted and that a convolutional component - to - component model (CCCM) mode should be used, applying the CCCM mode to predict chroma samples of the current CU based on the reconstructed luma samples of the current CU and the reference samples in the selected template, and encoding or decoding the current CU based on the predicted chroma samples of the current CU.

[0007]

[0007] In another example, the present disclosure is a device for encoding or decoding video data, the device comprising a memory configured to store the video data, and one or more processors implemented in circuitry, the one or more processors determining whether a selected template is permitted based on a comparison with an amount of reference samples in the selected template, the selected template being indicated by a mode index and each of the templates comprising a different set of reconstructed samples adjacent to a current coding unit (CU) of a current picture of the video data, and based on determining that the selected template is permitted and that a convolutional component - to - component model (CCCM) mode should be used, applying the CCCM mode to predict chroma samples of the current CU based on the reconstructed luma samples of the current CU and the reference samples in the selected template, and encoding or decoding the current CU based on the predicted chroma samples of the current CU.

[0008]

[0008] In another example, the present disclosure is a non-transitory computer-readable storage medium storing instructions that, when executed, cause one or more processors to compare a threshold with an amount of reference samples within a selected template, the mode index indicating which of a plurality of templates is the selected template, each template including a different set of reconstructed samples adjacent to a current coding unit (CU) of a current picture of video data, to determine whether the selected template is permitted, and based on determining that the selected template is permitted and that a convolutional component inter-model (CCCM) mode should be used, apply the CCCM mode to predict chroma samples of the current CU based on reconstructed luma samples of the current CU and reference samples within the selected template, and encode or decode the current CU based on the predicted chroma samples of the current CU.

[0009]

[0009] In another example, the present disclosure is a device for encoding or decoding video data, the device comprising a threshold value and a selected template, wherein a mode index indicates which of a plurality of templates is the selected template, and each of the templates comprises a different set of reconstructed samples adjacent to the current coding unit (CU) of the current picture of the video data, and means for determining whether the selected template is permitted based on a comparison of the amount of reference samples within the selected template with a threshold value, and means for applying a convolutional component - to - component model (CCCM) mode to predict the chroma samples of the current CU based on the reconstructed luma samples of the current CU and the reference samples within the selected template, based on a determination that the selected template is permitted and that the CCCM mode should be used, and means for encoding or decoding the current CU based on the predicted chroma samples of the current CU.

[0010]

[0010] Details of one or more examples are set forth in the accompanying drawings and the following description. Other features, objects, and advantages will be apparent from the description, drawings, and claims.

Brief Description of the Drawings

[0011]

Figure 1

[0011] A block diagram showing an exemplary video encoding and decoding system in which the techniques of the present disclosure may be implemented.

Figure 2

[0012] A block diagram showing an exemplary video encoder in which the techniques of the present disclosure may be implemented.

Figure 3

[0013] A block diagram showing an exemplary video decoder in which the techniques of the present disclosure may be implemented.

Figure 4

[0014] A conceptual diagram showing exemplary luma and chroma samples used for the derivation of a linear model.

Figure 5

[0015] It is a conceptual diagram showing an example of classifying adjacent samples into two groups.

Figure 6

[0016] It is a conceptual diagram showing neighboring reconstructed samples used for deriving the intra mode on the chroma decoder side.

Figure 7A

[0017] It is a conceptual diagram showing a model created using an inter-component linear model.

Figure 7B

[0018] It is a conceptual diagram showing the influence of the tilt adjustment parameter.

Figure 8

[0019] It is a conceptual diagram showing the spatial part of the convolutional filter.

Figure 9

[0020] It is a conceptual diagram showing the complete template used by the current coding unit (CU) according to the technique of the present disclosure.

Figure 10A

[0021] It is a conceptual diagram showing the upper template used by the current CU including the upper left sample according to the technique of the present disclosure.

Figure 10B

[0022] It is a conceptual diagram showing the upper template used by the current CU excluding the upper left sample according to the technique of the present disclosure.

Figure 11A

[0023] It is a conceptual diagram showing the left template used by the current CU including the upper left sample according to the technique of the present disclosure.

Figure 11B

[0024] It is a conceptual diagram showing the left template used by the current CU excluding the upper left sample according to the technique of the present disclosure.

Figure 12A

[0025] It is a conceptual diagram showing the template divided from the complete template according to the technique of the present disclosure.

Figure 12B

Figure 13A

[0026] A conceptual diagram showing templates on the same side according to the techniques of the present disclosure.

Figure 13B

Figure 14

[0027] A flowchart showing an exemplary method of encoding a current block according to the techniques of the present disclosure.

Figure 15

[0028] A flowchart showing an exemplary method of decoding a current block according to the techniques of the present disclosure.

Figure 16

[0029] A flowchart showing an exemplary method of encoding or decoding video data according to the techniques of the present disclosure.

Best Mode for Carrying Out the Invention

[0012]

[0030] A video coder may use specific coding tools such as a convolutional component - to - component model (CCCM) for intra - prediction, an inter - component linear model using slope adjustment, or chroma fusion for intra - prediction in video coding. These coding tools use a set of reconstructed neighboring samples for the current coding unit (CU). However, the set of reconstructed neighboring samples used in these coding tools is fixed. In other words, these coding tools always use the same set of reconstructed neighboring samples regardless of the location of the current CU within the picture or whether another set of reconstructed neighboring samples would result in better coding efficiency.

[0013]

[0031] Generally, the present disclosure describes techniques for template selection in video coding. A video coder (e.g., a video encoder or a video decoder) may determine whether a selected template is permitted based on a comparison between a threshold and an amount of reference samples in the selected template, where a mode index indicates which of a plurality of templates is the selected template. The mode index may be signaled within a bitstream. The video encoder may select the mode index to optimize coding efficiency. Each of the templates includes a different set of reconstructed samples adjacent to a current coding unit (CU) of a current picture of video data. Based on determining that the selected template is permitted and that a convolutional component - to - component model (CCCM) mode should be used, the video coder may apply the CCCM mode to predict chroma samples of the current CU based on the reconstructed luma samples of the current CU and the reference samples in the selected template. In other examples, the video coder may use coding tools other than CCCM, such as an inter - component linear model using slope adjustment or chroma fusion. The ability to select a template from among a plurality of templates may improve coding efficiency because different templates may result in different linear models with different accuracies.

[0014]

[0032] FIG. 1 is a block diagram showing an exemplary video encoding and decoding system 100 in which the techniques of the present disclosure may be implemented. The techniques of the present disclosure generally are directed to coding (encoding and / or decoding) video data. Generally, video data includes any data for processing video. Thus, video data may include raw unencoded video, encoded video, decoded (e.g., reconstructed) video, and video metadata such as signaling data.

[0015]

[0033] As shown in FIG. 1, in this example, the system 100 includes a source device 102 that provides encoded video data to be decoded and displayed by a destination device 116. Specifically, the source device 102 provides video data to the destination device 116 via a computer-readable recording medium 110. The source device 102 and the destination device 116 may include any of a wide range of devices, such as a desktop computer, a notebook (i.e., laptop) computer, a mobile device, a tablet computer, a set-top box, a telephone handset such as a smartphone, a television, a camera, a display device, a digital media player, a video gaming console, a video streaming device, a broadcast receiver device, etc. In some cases, since the source device 102 and the destination device 116 may support wireless communication, they may be referred to as wireless communication devices.

[0016]

[0034] In the example of FIG. 1, the source device 102 includes a video source 104, a memory 106, a video encoder 200, and an output interface 108. The destination device 116 includes an input interface 122, a video decoder 300, a memory 120, and a display device 118. According to the present disclosure, the video encoder 200 of the source device 102 and the video decoder 300 of the destination device 116 may be configured to apply techniques for intra prediction in video coding. Accordingly, the source device 102 represents an example of a video encoding device, while the destination device 116 represents an example of a video decoding device. In other examples, the source device and the destination device may include other components or configurations. For example, the source device 102 may receive video data from an external video source such as an external camera. Similarly, the destination device 116 may interface with an external display device rather than including an integrated display device.

[0017]

[0035] System 100 as shown in FIG. 1 is merely an example. Generally, any digital video encoding and / or decoding device may perform techniques for intra prediction in video coding. Source device 102 and destination device 116 are merely examples of coding devices that generate encoded video data that source device 102 transmits to destination device 116. This disclosure refers to a device that performs coding (encoding and / or decoding) of data as a "coding" device. Thus, video encoder 200 and video decoder 300 represent examples of coding devices, specifically, a video encoder and a video decoder, respectively. In some examples, source device 102 and destination device 116 may operate in a substantially symmetric manner such that each of source device 102 and destination device 116 includes video encoding and decoding components. Thus, system 100 may support one-way or two-way video transmission between source device 102 and destination device 116 for, for example, video streaming, video playback, video broadcasting, or video telephony.

[0018]

[0036] Generally, video source 104 represents a source of video data (i.e., raw, unencoded video data), provides a continuous series of pictures of video data (also referred to as "frames") to video encoder 200, and video encoder 200 encodes the data of the pictures. The video source 104 of source device 102 may include a video capture device such as a video camera, a video archive containing previously captured raw video, and / or a video feed interface that receives video from a video content provider. As a further alternative, video source 104 may generate computer graphics-based data as source video, or a combination of live video, archived video, and computer-generated video. In each case, video encoder 200 encodes the captured video data, pre-captured video data, or computer-generated video data. Video encoder 200 may reorder the pictures from the received order (sometimes referred to as "display order") to the coding order for coding. Video encoder 200 may generate a bitstream containing the encoded video data. Source device 102 may then output the encoded video data via output interface 108 to computer-readable recording medium 110 for reception and / or extraction, for example, by input interface 122 of destination device 116.

[0019]

[0037] The memories 106 of the source device 102 and 120 of the destination device 116 represent general-purpose memories. In some examples, the memories 106, 120 may store raw video data, e.g., raw video from the video source 104 and raw decoded video data from the video decoder 300. Additionally or alternatively, the memories 106, 120 may store software instructions executable by, e.g., the video encoder 200 and the video decoder 300, respectively. Although the memories 106 and 120 are shown separately from the video encoder 200 and the video decoder 300 in this example, it should be understood that the video encoder 200 and the video decoder 300 may also include internal memories for functionally similar or equivalent purposes. Further, the memories 106, 120 may store, e.g., encoded video data output from the video encoder 200 and input to the video decoder 300. In some examples, portions of the memories 106, 120 may be allocated as one or more video buffers to store, e.g., raw decoded video data and / or encoded video data.

[0020]

[0038] The computer-readable recording medium 110 can represent any type of medium or device capable of transferring encoded video data from the source device 102 to the destination device 116. In one example, the computer-readable recording medium 110 represents a communication medium that enables the source device 102 to directly transmit the encoded video data to the destination device 116 in real time, for example, via a radio frequency network or a computer-based network. The output interface 108 may modulate the transmission signal including the encoded video data, and the input interface 122 may demodulate the received transmission signal according to a communication standard such as a wireless communication protocol. The communication medium may include any wireless or wired communication medium, such as a radio frequency (RF) spectrum or one or more physical transmission lines. The communication medium may form part of a packet-based network, such as a local area network, a wide area network, or a global network such as the Internet. The communication medium may include a router, a switch, a base station, or any other device that may be useful for facilitating communication from the source device 102 to the destination device 116.

[0021]

[0039] In some examples, the source device 102 may output the encoded data from the output interface 108 to the storage device 112. Similarly, the destination device 116 may access the encoded data from the storage device 112 via the input interface 122. The storage device 112 may include any of various distributed data storage media or locally accessible data storage media, such as a hard drive, a Blu-ray disk, a DVD, a CD-ROM, a flash memory, a volatile or non-volatile memory, or any other suitable digital storage medium for storing the encoded video data.

[0022]

[0040] In some examples, the source device 102 may output the encoded video data to a file server 114 or another intermediate storage device that can store the encoded video data generated by the source device 102. The destination device 116 may access the stored video data from the file server 114 via streaming or downloading.

[0023]

[0041] The file server 114 can be any type of server device that can store the encoded video data and transmit the encoded video data to the destination device 116. The file server 114 can represent a web server (e.g., for a website), a server configured to provide a file transfer protocol service (such as the File Transfer Protocol (FTP) or the File Delivery over Unidirectional Transport (FLUTE) protocol), a content delivery network (CDN) device, a hypertext transfer protocol (HTTP) server, a Multimedia Broadcast Multicast Service (MBMS) or Enhanced MBMS (eMBMS) server, and / or a network attached storage (NAS) device. Additionally or alternatively, the file server 114 can implement one or more HTTP streaming protocols such as Dynamic Adaptive Streaming over HTTP (DASH), HTTP Live Streaming (HLS), Real Time Streaming Protocol (RTSP), and HTTP Dynamic Streaming.

[0024]

[0042] The destination device 116 can access the encoded video data from the file server 114 through any standard data connection including an Internet connection. This can include a wireless channel (e.g., Wi-Fi connection), a wired connection (e.g., digital subscriber line (DSL), cable modem, etc.), or a combination of both suitable for accessing the encoded video data stored on the file server 114. The input interface 122 can be configured to operate according to any one or more of the various protocols described above for retrieving or receiving media data from the file server 114, or other such protocols for retrieving media data.

[0025]

[0043] Output interface 108 and input interface 122 may represent a wireless transmitter / receiver, a modem, a wired network component (e.g., an Ethernet card), a wireless communication component operating according to any of various IEEE 802.11 standards, or other physical components. In examples where output interface 108 and input interface 122 include wireless components, output interface 108 and input interface 122 may be configured to transfer data such as encoded video data according to cellular communication standards such as 4G, 4G-LTE (Long Term Evolution), LTE-Advanced, 5G, etc. In some examples where output interface 108 includes a wireless transmitter, output interface 108 and input interface 122 may be configured to transfer data such as encoded video data according to other wireless standards such as the IEEE 802.11 specification, the IEEE 802.15 specification (e.g., ZigBee (trademark)), the Bluetooth (trademark) standard, etc. In some examples, source device 102 and / or destination device 116 may each include a respective system-on-a-chip (SoC) device. For example, source device 102 may include an SoC device that implements functions resulting from video encoder 200 and / or output interface 108, and destination device 116 may include an SoC device that implements functions resulting from video decoder 300 and / or input interface 122.

[0026]

[0044] The techniques of the present disclosure may be applied to video coding that supports any of various multimedia applications, such as over-the-air television broadcast, cable television transmission, satellite television transmission, Internet streaming video transmission such as HTTP-based Dynamic Adaptive Streaming over HTTP (DASH), digital video encoded on a data storage medium, decoding of digital video stored on a data storage medium, or other applications.

[0027]

[0045] The input interface 122 of the destination device 116 receives an encoded video bitstream from a computer-readable recording medium 110 (e.g., a communication medium, a storage device 112, a file server 114, etc.). The encoded video bitstream may include signaling information defined by the video encoder 200 and also used by the video decoder 300, such as syntax elements having values that describe the characteristics and / or processing of video blocks or other coded units (e.g., slices, pictures, picture groups, sequences, etc.). The display device 118 displays the decoded pictures of the decoded video data to the user. The display device 118 may represent any of various display devices, such as a liquid crystal display (LCD), a plasma display, an organic light emitting diode (OLED) display, or another type of display device.

[0028]

[0046] Although not shown in FIG. 1, in some examples, the video encoder 200 and the video decoder 300 may each be integrated with an audio encoder and / or an audio decoder and may include a suitable MUX-DEMUX unit, or other hardware and / or software, to handle a multiplexed stream that includes both audio and video in a common data stream.

[0029]

[0047] Video encoder 200 and video decoder 300 may each be implemented as any of a variety of suitable encoder and / or decoder circuits, such as one or more microprocessors, digital signal processors (DSPs), application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), discrete logic, software, hardware, firmware, or any combination thereof. When the techniques are implemented partially in software, the device may store instructions for the software in a suitable non-transitory computer-readable recording medium and execute the instructions in hardware using one or more processors to perform the techniques of the present disclosure. Each of video encoder 200 and video decoder 300 may be included within one or more encoders or decoders, and any of them may be integrated as part of a combined encoder / decoder (CODEC) in their respective devices. Devices including video encoder 200 and / or video decoder 300 may include integrated circuits, microprocessors, and / or wireless communication devices such as cellular telephones.

[0030]

[0048] Video encoder 200 and video decoder 300 may operate according to a video coding standard such as ITU-T H.265, also known as High Efficiency Video Coding (HEVC), or an extended standard thereof such as multi-view and / or scalable video coding extensions. Alternatively, video encoder 200 and video decoder 300 may operate according to other proprietary or industry standards such as ITU-T H.266, also known as Versatile Video Coding (VVC). In some examples, video encoder 200 and video decoder 300 may operate according to an Essential Video Coding (EVC) codec. In other examples, video encoder 200 and video decoder 300 may operate according to a proprietary video codec / format such as AOMedia Video1 (AV1), an extension of AV1, and / or a successor version of AV1 (e.g., AV2). In other examples, video encoder 200 and video decoder 300 may operate according to other proprietary formats or industry standards. However, the techniques of the present disclosure are not limited to any particular coding standard or format. Generally, video encoder 200 and video decoder 300 can be configured to implement the techniques of the present disclosure with any video coding technique that uses intra prediction in video coding.

[0031]

[0049] Generally, video encoder 200 and video decoder 300 may perform block - based coding of pictures. The term "block" generally refers to a structure that contains data to be processed (e.g., encoded, decoded, or otherwise used in an encoding and / or decoding process). For example, a block may include a two - dimensional matrix of samples of luminance and / or chrominance data. Generally, video encoder 200 and video decoder 300 may code video data represented in a YUV (e.g., Y, Cb, Cr) format. That is, instead of coding red, green, and blue (RGB) data for samples of a picture, video encoder 200 and video decoder 300 may code a luminance component and a chrominance component, and the chrominance component may include both a red and a blue chrominance component. In some examples, video encoder 200 converts received RGB - format data to a YUV representation before encoding, and video decoder 300 converts the YUV representation to an RGB format. Alternatively, a pre - processing unit and a post - processing unit (not shown) may perform these conversions.

[0032]

[0050] This disclosure may refer to the coding (e.g., encoding and decoding) of pictures as generally including a process of encoding or decoding picture data. Similarly, this disclosure may refer to the coding of blocks of pictures as including a process of encoding or decoding data for the blocks, e.g., prediction and / or residual coding. An encoded video bitstream generally includes a series of values of syntax elements that represent coding decisions (e.g., coding modes) and the partitioning of a picture into blocks. Thus, a reference to coding a picture or a block should generally be understood as the coding values of the syntax elements that form the picture or block.

[0033]

[0051] HEVC defines various blocks, including coding units (CUs), prediction units (PUs), and transform units (TUs). According to HEVC, a video coder (such as video encoder 200) divides a coding tree unit (CTU) into CUs according to a quadtree structure. That is, the video coder divides the CTU and CU into four equal non-overlapping squares, and each node of the quadtree has either 0 or 4 child nodes. A node without child nodes may be called a "leaf node", and the CU of such a leaf node may include one or more PUs and / or one or more TUs. The video coder may further divide the PUs and TUs. For example, in HEVC, a residual quadtree (RQT) represents the division of TUs. In HEVC, PUs represent inter-prediction data and TUs represent residual data. An intra-predicted CU includes intra-prediction information such as an intra-mode indication.

[0034]

[0052] As another example, video encoder 200 and video decoder 300 may be configured to operate according to VVC. According to VVC, a video coder (such as video encoder 200) divides a picture into a plurality of coding tree units (CTUs). Video encoder 200 may divide the CTU according to a tree structure such as a quadtree-binary tree (QTBT) structure or a multi-type tree (MTT) structure. The QTBT structure eliminates the concept of multiple division types, such as the separation between the CUs, PUs, and TUs of HEVC. The QTBT structure includes two levels, namely, a first level divided according to quadtree division and a second level divided according to binary tree division. The root node of the QTBT structure corresponds to the CTU. The leaf node of the binary tree corresponds to coding units (CUs).

[0035]

[0053] In the MTT partitioning structure, blocks can be partitioned using a quadtree (QT) partition, a binary tree (BT) partition, and one or more types of triple trees (TT) (also referred to as ternary trees). A triple tree partition or ternary tree partition is a partition in which a block is divided into three sub-blocks. In some examples, the triple tree partition or ternary tree partition divides a block into three sub-blocks without dividing the original block through its center. The partitioning types (e.g., QT, BT, and TT) in the MTT can be symmetric or asymmetric.

[0036]

[0054] When operating according to the AV1 codec, the video encoder 200 and the video decoder 300 can be configured to code video data within a block. In AV1, the largest coding block that can be processed is called a superblock. In AV1, a superblock can be either 128×128 luma samples or 64×64 luma samples. However, in a successor video coding format (e.g., AV2), a superblock can be defined by a different (e.g., larger) luma sample size. In some examples, a superblock is at the top level of a block quadtree. The video encoder 200 can further partition a superblock into smaller coding blocks. The video encoder 200 can use square or non-square partitioning to partition a superblock and other coding blocks into smaller blocks. Non-square blocks can include N / 2×N, N×N / 2, N / 4×N, and N×N / 4 blocks. The video encoder 200 and the video decoder 300 can perform separate prediction and transform processes for each of the coding blocks.

[0037]

[0055] AV1 also defines tiles for video data. A tile is a rectangular array of super blocks that can be coded independently of other tiles. That is, video encoder 200 and video decoder 300 can encode and decode the coding blocks within a tile, respectively, without using video data from other tiles. However, video encoder 200 and video decoder 300 can perform filtering across tile boundaries. Tiles may be of uniform or non-uniform size. Tile-based coding may enable parallel processing and / or multi-threading for encoder and decoder implementations.

[0038]

[0056] In some examples, video encoder 200 and video decoder 300 may use a single QTBT structure or MTT structure to represent each of the luminance and chrominance components. In other examples, video encoder 200 and video decoder 300 may use two or more QTBT or MTT structures, such as one QTBT / MTT structure for the luminance component and another QTBT / MTT structure for both chrominance components (or two QTBT / MTT structures for each chrominance component).

[0039]

[0057] Video encoder 200 and video decoder 300 may be configured to use a quadtree partition, QTBT partition, MTT partition, super block partition, or other partitioning structure.

[0040]

[0058] In some examples, a CTU includes a coding tree block (CTB) of luma samples, two corresponding CTBs of chroma samples of a picture having three sample arrays, or a CTB of samples of a picture coded using three separate color planes and syntax structures for coding monochrome pictures or samples. A CTB may be an N×N block of samples for some value of N that divides the components into CTBs. A component may be a single sample from one of the one array or three arrays (luma and two chroma) that make up a picture in a 4:2:0, 4:2:2, or 4:4:4 color format, or a single sample of an array that makes up a picture in an array or monochrome format. In some examples, a coding block is an M×N block of samples for some values of M and N that divides a CTB into coding blocks.

[0041]

[0059] Blocks (e.g., CTUs or CUs) may be grouped in various ways within a picture. As an example, a block may refer to a rectangular region of CTU rows within a particular tile in the picture. A tile may be a rectangular region of CTUs within a particular tile column and a particular tile row in the picture. A tile column refers to a rectangular region of CTUs having a height equal to the height of the picture and a width specified by a syntax element (such as in a picture parameter set). A tile row refers to a rectangular region of CTUs having a height specified by a syntax element (such as in a picture parameter set) and a width equal to the width of the picture.

[0042]

[0060] In some examples, a tile may be divided into a plurality of blocks, and each of the blocks may include one or more CTU rows within the tile. A tile that is not divided into a plurality of blocks may also be referred to as a block. However, a block that is a true subset of a tile may not be referred to as a tile. The blocks within a picture may also be arranged as slices. A slice may be an integral number of blocks of a picture that may be exclusively included within a single network abstraction layer (NAL) unit. In some examples, a slice may include either some complete tiles, or only a contiguous sequence of complete blocks of one tile.

[0043]

[0061] The present disclosure may interchangeably use "N×N" and "N times N", e.g., 16×16 samples or 16 times 16 samples, to refer to the sample dimensions of a block (such as a CU or other video block) in the vertical and horizontal dimensions. Generally, a 16×16 CU has 16 samples in the vertical direction (y = 16) and 16 samples in the horizontal direction (x = 16). Similarly, an N×N CU generally has N samples in the vertical direction and N samples in the horizontal direction, where N represents a non-negative integer value. The samples within a CU may be arranged in rows and columns. Moreover, a CU does not necessarily need to have the same number of samples in the horizontal direction as in the vertical direction. For example, a CU may include N×M samples, and M is not necessarily equal to N.

[0044]

[0062] The video encoder 200 encodes video data for a CU that represents prediction and / or residual information, as well as other information. The prediction information indicates how the CU is to be predicted to form a prediction block for the CU. The residual information generally represents the per-sample difference between the samples of the CU before encoding and the prediction block.

[0045]

[0063] To predict a CU, the video encoder 200 may generally form a prediction block for the CU through inter prediction or intra prediction. Inter prediction generally refers to predicting a CU from the data of a previously coded picture, and intra prediction generally refers to predicting a CU from the data coded previously in the same picture. To perform inter prediction, the video encoder 200 may use one or more motion vectors to generate a prediction block. The video encoder 200 may generally perform a motion search to identify a reference block that exactly matches the CU with respect to the difference between the CU and the reference block. The video encoder 200 may calculate a difference metric using sum of absolute difference (SAD), sum of squared differences (SSD), mean absolute difference (MAD), mean squared differences (MSD), or other such difference calculations to determine whether the reference block exactly matches the current CU. In some examples, the video encoder 200 may predict the current CU using uni - directional prediction or bi - directional prediction.

[0046]

[0064] Some examples of VVC also provide an affine motion compensation mode that can be regarded as an inter - prediction mode. In the affine motion compensation mode, the video encoder 200 may determine two or more motion vectors representing non - translational motion, such as zoom - in or zoom - out, rotation, perspective movement, or other irregular motion types.

[0047]

[0065] To perform intra prediction, video encoder 200 may select an intra prediction mode to generate a prediction block. Some examples of VVC provide 67 intra prediction modes including various direction modes, as well as a planar mode and a DC mode. Generally, video encoder 200 selects an intra prediction mode that describes adjacent samples for the current block (e.g., a block of a CU) and predicts the samples of the current block therefrom. Assuming that video encoder 200 codes CTUs and CUs in raster scan order (left to right, top to bottom), such samples can generally be above, above and to the left, or to the left of the current block in the same picture as the current block.

[0048]

[0066] Video encoder 200 encodes data representing the prediction mode for the current block. For example, in the case of inter prediction mode, video encoder 200 may encode data indicating which of the various available inter prediction modes is used, as well as data representing motion information for the corresponding mode. In the case of uni - directional or bi - directional inter prediction, for example, video encoder 200 may use an advanced motion vector prediction (AMVP) mode or a merge mode to encode the motion vector. Video encoder 200 may use a similar mode to encode the motion vectors of the affine motion compensation mode.

[0049]

[0067] AV1 includes two general techniques for encoding and decoding coding blocks of video data. The two general techniques are intra prediction (e.g., intra-frame prediction or spatial prediction) and inter prediction (e.g., inter-frame prediction or temporal prediction). In the context of AV1, when predicting a block of the current frame of video data using an intra prediction mode, video encoder 200 and video decoder 300 do not use video data from other frames of the video data. In most intra prediction modes, video encoder 200 encodes a block of the current frame based on the difference between the sample values within the current block and the predicted values generated from reference samples within the same frame. Video encoder 200 determines the predicted values generated from reference samples based on the intra prediction mode.

[0050]

[0068] Following prediction such as intra prediction or inter prediction of a block, video encoder 200 may calculate the residual data of the block. Residual data, such as a residual block, represents the sample-by-sample difference between the block and the predicted block for that block formed using the corresponding prediction mode. Video encoder 200 may apply one or more transforms to the residual block to generate transform data in the transform domain rather than the sample domain. For example, video encoder 200 may apply a discrete cosine transform (DCT), an integer transform, a wavelet transform, or a conceptually similar transform to the residual video data. Additionally, video encoder 200 may apply a secondary transform, such as a mode-dependent non-separable secondary transform (MDNSST), a signal-dependent transform, a Karhunen-Loeve transform (KLT), etc., following the first transform. Video encoder 200 generates transform coefficients following the application of one or more transforms.

[0051]

[0069] As described above, following any transformation that generates transformation coefficients, video encoder 200 may perform quantization of the transformation coefficients. Quantization generally refers to the process of quantizing transformation coefficients to reduce, to the extent possible, the amount of data used to represent the transformation coefficients and perform further compression. By performing the quantization process, video encoder 200 may reduce the bit depth associated with some or all of the transformation coefficients. For example, video encoder 200 may truncate an n-bit value to an m-bit value during quantization, where n is greater than m. In some examples, to perform quantization, video encoder 200 may perform a right shift of the bits of the value to be quantized.

[0052]

[0070] Following quantization, video encoder 200 may scan the transformation coefficients to generate a one-dimensional vector from the two-dimensional matrix containing the quantized transformation coefficients. The scan may be designed such that transformation coefficients with higher energy (and thus lower frequency) are placed towards the front of the vector and transformation coefficients with lower energy (and thus higher frequency) are placed towards the back of the vector. In some examples, video encoder 200 may generate a serialized vector and then use a predefined scan order to scan the quantized transformation coefficients in order to entropy code the quantized transformation coefficients of the vector. In other examples, video encoder 200 may perform an adaptive scan. After scanning the quantized transformation coefficients to form a one-dimensional vector, video encoder 200 may entropy code the one-dimensional vector, for example, according to context-adaptive binary arithmetic coding (CABAC). Video encoder 200 may also entropy code the values for syntax elements that describe metadata associated with the encoded video data that video decoder 300 uses when decoding the video data.

[0053]

[0071] To perform CABAC, the video encoder 200 may assign the context within the context model to the symbol to be transmitted. The context may be related to, for example, whether the adjacent values of the symbol are zero-valued. The probability determination may be based on the context assigned to the symbol.

[0054]

[0072] The video encoder 200 may further generate syntax data such as block-based syntax data, picture-based syntax data, and sequence-based syntax data for the video decoder 300, for example, within other syntax data such as a picture header, a block header, a slice header, or a sequence parameter set (SPS), a picture parameter set (PPS), or a video parameter set (VPS). The video decoder 300 may similarly decode such syntax data to determine how to decode the corresponding video data.

[0055]

[0073] In this way, the video encoder 200 may generate a bitstream including encoded video data, for example, syntax elements describing the partitioning of a picture into blocks (e.g., CUs) and prediction information and / or residual information for the blocks. Finally, the video decoder 300 may receive the bitstream and decode the encoded video data.

[0056]

[0074] Generally, video decoder 300 performs an inverse process to the process implemented by video encoder 200 to decode the encoded video data of the bitstream. For example, video decoder 300 may use CABAC to decode the values for the syntax elements of the bitstream in a substantially similar manner that is inverse to the CABAC encoding process of video encoder 200. The syntax elements may define the partitioning of the picture into CTUs, and the partitioning information for each CTU according to the corresponding partitioning structure such as the QTBT structure, in order to define the CUs of the CTUs. The syntax elements may further define the prediction information and residual information for the blocks (e.g., CUs) of the video data.

[0057]

[0075] The residual information may be represented, for example, by quantized transform coefficients. Video decoder 300 may inverse quantize and inverse transform the quantized transform coefficients of the block to reproduce the residual block for the block. Video decoder 300 uses the signaling prediction mode (intra prediction or inter prediction) and the related prediction information (e.g., motion information for inter prediction) to form the prediction block for the block. Video decoder 300 can then combine the prediction block and the residual block (sample by sample) to reproduce the original block. Video decoder 300 may perform additional processing such as performing a deblocking process to reduce visual artifacts along the boundaries of the blocks.

[0058]

[0076] This disclosure may generally refer to "signaling" some information, such as a syntax element. The term "signaling" may generally refer to the communication of values for syntax elements and / or other data used to decode encoded video data. That is, video encoder 200 may signal values for syntax elements within a bitstream. Generally, signaling refers to generating values within a bitstream. As described above, source device 102 may transfer the bitstream to destination device 116 substantially in real time or non-real time, which may occur, for example, when storing syntax elements in storage device 112 for later retrieval by destination device 116.

[0059]

[0077] According to the techniques of this disclosure, video encoder 200 and video decoder 300 may determine whether a selected template is permitted based on a comparison of a threshold with the amount of reference samples within the selected template. A mode index may indicate which of a plurality of templates is the selected template. Each of the templates includes a different set of reconstructed samples adjacent to the current CU of the current picture of the video data. If the selected template is permitted and the CCCM mode is to be used for the current CU, video encoder 200 and video decoder 300 may apply the CCCM mode to predict the chroma samples of the current CU based on the reconstructed luma samples of the current CU and the reference samples within the selected template. If the selected template is not permitted or the CCCM mode is not to be used for the current CU, video encoder 200 and video decoder 300 may use another coding tool, such as a linear mode. The CCCM model may predict the chroma samples of the current CU based on the application of a filter to the luma samples of the current CU. The coefficients of the filter may be based on samples within the selected template. Video encoder 200 and video decoder 300 may encode or decode the current CU based on a predictor for the current CU.

[0060]

[0078] FIG. 2 is a block diagram showing an exemplary video encoder 200 that can implement the techniques of the present disclosure. FIG. 2 is provided for illustration and should not be considered as limiting the techniques widely exemplified and described in the present disclosure. For illustration purposes, the present disclosure will describe the video encoder 200 according to the techniques of VVC (ITU-T H.266 under development) and HEVC (ITU-T H.265). However, the techniques of the present disclosure can be implemented by other video coding standards, as well as video encoding devices configured for video coding formats such as successors to the AV1 and AV1 video coding formats.

[0061]

[0079] In the example of FIG. 2, the video encoder 200 includes a video data memory 230, a mode selection unit 202, a residual generation unit 204, a transform processing unit 206, a quantization unit 208, an inverse quantization unit 210, an inverse transform processing unit 212, a reconstruction unit 214, a filter unit 216, a decoded picture buffer (DPB) 218, and an entropy encoding unit 220. Any or all of the video data memory 230, the mode selection unit 202, the residual generation unit 204, the transform processing unit 206, the quantization unit 208, the inverse quantization unit 210, the inverse transform processing unit 212, the reconstruction unit 214, the filter unit 216, the DPB 218, and the entropy encoding unit 220 can be implemented in one or more processors or in processing circuitry. For example, the units of the video encoder 200 can be implemented as one or more circuits or logic elements as part of a hardware circuit, or as part of a processor, an ASIC, or an FPGA. Moreover, the video encoder 200 may include additional or alternative processors or processing circuitry to perform these and other functions.

[0062]

[0080] The video data memory 230 may store video data to be encoded by components of the video encoder 200. The video encoder 200 may receive video data stored within the video data memory 230, for example, from the video source 104 (FIG. 1). The DPB 218 may function as a reference picture memory that stores reference video data used in the prediction of subsequent video data by the video encoder 200. The video data memory 230 and the DPB 218 may be formed by any of various memory devices, such as a DRAM including a synchronous dynamic random access memory (SDRAM), a magnetoresistive RAM (MRAM), a resistive RAM (RRAM), or other types of memory devices. The video data memory 230 and the DPB 218 may be provided by the same memory device or separate memory devices. In various examples, the video data memory 230 may be on-chip with other components of the video encoder 200 or off-chip with respect to those components, as shown.

[0063]

[0081] In the present disclosure, a reference to the video data memory 230 should not be construed as being limited to the memory internal to the video encoder 200 or the memory external to the video encoder 200 unless otherwise specifically described as such. Rather, a reference to the video data memory 230 should be understood as a reference memory that stores video data received by the video encoder 200 for encoding (e.g., video data for the current block to be encoded). The memory 106 of FIG. 1 may also provide temporary storage of outputs from various units of the video encoder 200.

[0064]

[0082] The various units in FIG. 2 are shown to assist in understanding the operations performed by video encoder 200. The units may be implemented as fixed-function circuits, programmable circuits, or combinations thereof. A fixed-function circuit refers to a circuit that provides a specific function, and the operations that can be performed are pre-set. A programmable circuit refers to a circuit that can be programmed to perform various tasks and provides a flexible function in the operations that can be performed. For example, a programmable circuit may execute software or firmware that operates the programmable circuit in a manner defined by instructions of the software or firmware. A fixed-function circuit may execute software instructions (e.g., receive or output parameters), but the type of operations performed by the fixed-function circuit is generally invariant. In some examples, one or more of the units may be different circuit blocks (fixed-function or programmable), and in some examples, one or more of the units may be integrated circuits.

[0065]

[0083] Video encoder 200 may include a programmable core formed from arithmetic logic units (ALUs), elementary function units (EFUs), digital circuits, analog circuits, and / or programmable circuits. In an example where the operations of video encoder 200 are performed using software executed by a programmable circuit, memory 106 (FIG. 1) may store instructions of the software (e.g., object code) that video encoder 200 receives and executes, or another memory (not shown) within video encoder 200 may store such instructions.

[0066]

[0084] The video data memory 230 is configured to store the received video data. The video encoder 200 may extract a picture of the video data from the video data memory 230 and provide the video data to the residual generation unit 204 and the mode selection unit 202. The video data in the video data memory 230 may be raw video data to be encoded.

[0067]

[0085] The mode selection unit 202 includes a motion estimation unit 222, a motion compensation unit 224, and an intra prediction unit 226. The mode selection unit 202 may include additional functional units that perform video prediction according to other prediction modes. By way of example, the mode selection unit 202 may include a palette unit, an intra block copy unit (which may be part of the motion estimation unit 222 and / or the motion compensation unit 224), an affine unit, a linear model (LM) unit, and the like.

[0068]

[0086] Generally, the mode selection unit 202 coordinates a plurality of encoding paths to test a combination of encoding parameters and the resulting rate distortion value for such a combination. The encoding parameters may include the division of the CTU into CUs, the prediction mode for the CUs, the type of transform for the residual data of the CUs, the quantization parameter for the residual data of the CUs, and the like. The mode selection unit 202 may ultimately select a combination of encoding parameters that has a better rate distortion value than other tested combinations.

[0069]

[0087] Video encoder 200 may divide the pictures taken from video data memory 230 into a series of CTUs, and encapsulate one or more CTUs within a slice. Mode selection unit 202 may divide the CTUs of a picture according to a tree structure, such as the MTT structure, QTBT structure, superblock structure, or quadtree structure described above. As described above, video encoder 200 may form one or more CUs by dividing CTUs according to a tree structure. Such CUs are sometimes generally referred to as "video blocks" or "blocks".

[0070]

[0088] Generally, mode selection unit 202 also controls its components (e.g., motion estimation unit 222, motion compensation unit 224, and intra prediction unit 226) to generate a prediction block for the current block (e.g., the current CU, or in HEVC, the overlapping part of the PU and TU). In the case of inter prediction of the current block, motion estimation unit 222 may perform a motion search to identify one or more exactly matching reference blocks among one or more reference pictures (e.g., one or more previously coded pictures stored in DPB 218). Specifically, motion estimation unit 222 may calculate a value representing how similar a possible reference block is to the current block, according to, for example, sum of absolute differences (SAD), sum of squared differences (SSD), mean absolute difference (MAD), mean squared difference (MSD), etc. Motion estimation unit 222 may generally perform these calculations using the sample-by-sample differences between the current block and the reference block under consideration. Motion estimation unit 222 may identify the reference block having the lowest value obtained from these calculations, which indicates the reference block that most closely matches the current block.

[0071]

[0089] The motion estimation unit 222 may form one or more motion vectors (MVs) that define the position of a reference block in a reference picture relative to the position of a current block in the current picture. The motion estimation unit 222 may then provide the motion vectors to the motion compensation unit 224. For example, in the case of uni - directional inter - prediction, the motion estimation unit 222 may provide a single motion vector, while in the case of bi - directional inter - prediction, the motion estimation unit 222 may provide two motion vectors. The motion compensation unit 224 may then use the motion vectors to generate a prediction block. For example, the motion compensation unit 224 may use the motion vectors to retrieve data of the reference block. As another example, if the motion vectors have fractional - sample accuracy, the motion compensation unit 224 may interpolate values for the prediction block according to one or more interpolation filters. Moreover, in the case of bi - directional inter - prediction, the motion compensation unit 224 may retrieve data for two reference blocks identified by the respective motion vectors and combine the retrieved data, for example, through sample - by - sample averaging or weighted averaging.

[0072]

[0090] When the motion estimation unit 222 and the motion compensation unit 224 operate according to the AV1 video coding format, they may be configured to encode coding blocks of video data (e.g., both luma coding blocks and chroma coding blocks) using translational motion compensation, affine motion compensation, overlapped block motion compensation (OBMC), and / or composite inter - intra prediction.

[0073]

[0091] As another example, in the case of intra prediction or intra prediction coding, the intra prediction unit 226 may generate a prediction block from samples adjacent to the current block. For example, in the case of the direction mode, the intra prediction unit 226 may generally mathematically combine the values of adjacent samples to generate a prediction block and populate these calculated values in a direction defined across the current block. As another example, in the case of the DC mode, the intra prediction unit 226 may calculate the average of adjacent samples for the current block and generate a prediction block that includes this obtained average for each sample of the prediction block.

[0074]

[0092] When operating according to the AV1 video coding format, the intra prediction unit 226 may be configured to encode coding blocks of video data (e.g., both luma coding blocks and chroma coding blocks) using directional intra prediction, non-directional intra prediction, recursive filter intra prediction, chroma-from-luma (CFL) prediction, intra block copy (IBC), and / or color palette mode. The mode selection unit 202 may include additional functional units that perform video prediction according to other prediction modes. In the example of FIG. 2, the intra prediction unit 226 includes a CCCM unit 228 that generates a predictor using the CCCM mode according to the techniques of the present disclosure.

[0075]

[0093] The mode selection unit 202 provides the prediction block to the residual generation unit 204. The residual generation unit 204 receives the raw, unencoded version of the current block from the video data memory 230 and the prediction block from the mode selection unit 202. The residual generation unit 204 calculates the sample-by-sample difference between the current block and the prediction block. The resulting sample-by-sample difference defines the residual block for the current block. In some examples, the residual generation unit 204 may also determine the differences between the sample values within the residual block in order to generate the residual block using residual differential pulse code modulation (RDPCM). In some examples, the residual generation unit 204 may be formed using one or more subtractor circuits that perform binary subtraction.

[0076]

[0094] In an example where the mode selection unit 202 divides a CU into PUs, each PU may be associated with a luma prediction unit and a corresponding chroma prediction unit. The video encoder 200 and the video decoder 300 can support PUs of various sizes. As described above, the size of a CU may refer to the size of the luma coding block of the CU, and the size of a PU may refer to the size of the luma prediction unit of the PU. Assuming that the size of a particular CU is 2N×2N, the video encoder 200 may support PU sizes of 2N×2N or N×N for intra prediction, and 2N×2N, 2N×N, N×2N, N×N, or similar, symmetric PU sizes for inter prediction. The video encoder 200 and the video decoder 300 may also support asymmetric partitions of PU sizes of 2N×nU, 2N×nD, nL×2N, and nR×2N for inter prediction.

[0077]

[0095] In an example where the mode selection unit 202 does not further divide the CU into PUs, each CU may be associated with a luma coding block and a corresponding chroma coding block. As described above, the size of the CU may refer to the size of the luma coding block of the CU. The video encoder 200 and the video decoder 300 may support CU sizes of 2N×2N, 2N×N, or N×2N.

[0078]

[0096] As some examples, in the case of other video coding techniques such as intra block copy mode coding, affine mode coding, and linear model (LM) mode coding, the mode selection unit 202 generates a prediction block for the currently encoded block via each unit associated with the coding technique. In some examples such as palette mode coding, the mode selection unit 202 may not generate a prediction block. Instead, it may generate a syntax element indicating a way to reconstruct the block based on the selected palette. In such a mode, the mode selection unit 202 may provide these syntax elements to the entropy coding unit 220 to be encoded.

[0079]

[0097] As described above, the residual generation unit 204 receives video data for the current block and the corresponding prediction block. The residual generation unit 204 then generates a residual block for the current block. To generate the residual block, the residual generation unit 204 calculates the sample-by-sample difference between the prediction block and the current block.

[0080]

[0098] The transformation processing unit 206 applies one or more transformations to the residual block to generate a block of transformation coefficients (referred to herein as the "transformation coefficient block"). The transformation processing unit 206 may apply various transformations to the residual block to form the transformation coefficient block. For example, the transformation processing unit 206 may apply a discrete cosine transform (DCT), a directional transform, a Karhunen-Loeve transform (KLT), or a conceptually similar transform to the residual block. In some examples, the transformation processing unit 206 may perform multiple transformations, such as a secondary transformation such as a primary transformation and a rotation transformation, on the residual block. In some examples, the transformation processing unit 206 does not apply a transformation to the residual block.

[0081]

[0099] When the transformation processing unit 206 operates according to AV1, it may apply one or more transformations to the residual block to generate a block of transformation coefficients (referred to herein as the "transformation coefficient block"). The transformation processing unit 206 may apply various transformations to the residual block to form the transformation coefficient block. For example, the transformation processing unit 206 may apply a horizontal / vertical transformation combination that may include a discrete cosine transform (DCT), an asymmetric discrete sine transform (ADST), an inverse ADST (e.g., ADST in reverse order), and an identity transform (IDTX). When using the identity transform, the transformation is skipped in one of the vertical or horizontal directions. In some examples, the transformation processing may be skipped.

[0082]

[0100] The quantization unit 208 may quantize the transform coefficients in the transform coefficient block to generate a quantized transform coefficient block. The quantization unit 208 may quantize the transform coefficients of the transform coefficient block according to the quantization parameter (QP) value associated with the current block. The video encoder 200 may adjust the degree of quantization applied to the transform coefficient block associated with the current block by adjusting the QP value associated with the CU (e.g., via the mode selection unit 202). Quantization may result in loss of information, and thus the quantized transform coefficients may be less accurate than the original transform coefficients generated by the transform processing unit 206.

[0083]

[0101] The inverse quantization unit 210 and the inverse transform processing unit 212 may apply inverse quantization and inverse transform, respectively, to the quantized transform coefficient block to reconstruct the residual block from the transform coefficient block. The reconstruction unit 214 may generate a reconstructed block corresponding to the current block (which may be accompanied by a certain degree of distortion) based on the reconstructed residual block and the prediction block generated by the mode selection unit 202. For example, the reconstruction unit 214 may add the samples of the reconstructed residual block to the corresponding samples from the prediction block generated by the mode selection unit 202 to generate the reconstructed block.

[0084]

[0102] The filter unit 216 may perform one or more filter operations on the reconstructed block. For example, the filter unit 216 may perform a deblocking operation to reduce the blocking artifacts along the edges of the CU. The operation of the filter unit 216 may be skipped in some examples.

[0085]

[0103] When operating according to AV1, the filter unit 216 may perform one or more filter operations on the reconstructed block. For example, the filter unit 216 may perform a deblocking operation to reduce blockiness artifacts along the edges of the CU. In other examples, the filter unit 216 may apply a constrained directional enhancement filter (CDEF), which may be applied after deblocking and may include the application of an inseparable, non-linear, low-pass directional filter based on the estimated edge direction. The filter unit 216 may also include a loop restoration filter, which is applied after CDEF and may include a separable symmetric normalized Wiener filter or a dual self-induced filter.

[0086]

[0104] The video encoder 200 stores the reconstructed block in the DPB 218. For example, in an example where the operation of the filter unit 216 is not performed, the reconstruction unit 214 may store the reconstructed block in the DPB 218. In an example where the operation of the filter unit 216 is performed, the filter unit 216 may store the filtered reconstructed block in the DPB 218. The motion estimation unit 222 and the motion compensation unit 224 may retrieve a reference picture formed from the reconstructed (and possibly filtered) blocks from the DPB 218 to inter-predict blocks of a picture to be encoded later. In addition, the intra prediction unit 226 may use the reconstructed blocks of the current picture in the DPB 218 to intra-predict other blocks in the current picture.

[0087]

[0105] Generally, the entropy encoding unit 220 may entropy-encode syntax elements received from other functional components of the video encoder 200. For example, the entropy encoding unit 220 may entropy-encode the quantized transform coefficient blocks from the quantization unit 208. As another example, the entropy encoding unit 220 may entropy-encode prediction syntax elements (e.g., motion information for inter prediction or intra mode information for intra prediction) from the mode selection unit 202. The entropy encoding unit 220 may perform one or more entropy encoding operations on syntax elements, which are another example of video data, to generate entropy-encoded data. For example, the entropy encoding unit 220 may perform context-adaptive variable length coding (CAVLC) operations, CABAC operations, variable-to-variable (V2V) coding operations, syntax-based context-adaptive binary arithmetic coding (SBAC) operations, Probability Interval Partitioning Entropy (PIPE) coding operations, exponential Golomb coding operations, or another type of entropy encoding operation on the data. In some examples, the entropy encoding unit 220 may operate in a bypass mode where the syntax elements are not entropy-encoded.

[0088]

[0106] The video encoder 200 may output a bitstream including entropy-encoded syntax elements required to reconstruct blocks of a slice or a picture. Specifically, the entropy encoding unit 220 may output the bitstream.

[0089]

[0107] Entropy encoding unit 220 may be configured as a symbol-to-symbol adaptive multi-symbol arithmetic coder according to AV1. The syntax elements in AV1 include an alphabet of N elements, and the context (e.g., probability model) includes a set of N probabilities. Entropy encoding unit 220 may store the probabilities as n-bit (e.g., 15-bit) cumulative distribution functions (CDFs). Entropy encoding unit 220 may perform recursive scaling using an update factor based on the alphabet size to update the context.

[0090]

[0108] The operations described above are described with respect to blocks. Such descriptions should be understood as being operations on luma coding blocks and / or chroma coding blocks. As described above, in some examples, the luma coding blocks and chroma coding blocks are the luma and chroma components of the CU. In some examples, the luma coding blocks and chroma coding blocks are the luma and chroma components of the PU.

[0091]

[0109] In some examples, the operations performed on the luma coding blocks need not be repeated for the chroma coding blocks. As an example, the operation of identifying the motion vector (MV) and reference picture for the luma coding block need not be repeated to identify the MV and reference picture for the chroma block. Rather, the MV of the luma coding block may be scaled to determine the MV of the chroma block, and the reference picture may be the same. As another example, the intra prediction process may be the same for the luma coding block and the chroma coding block.

[0092]

[0110] As described above, the intra prediction unit 226 may include a CCCM unit 228. The CCCM unit 228 may determine whether the selected template is permitted based on a comparison between a threshold value and the amount of reference samples in the selected template. The video encoder 200 may signal a mode index indicating which of the plurality of templates is the selected template. Each of the templates includes a different set of reconstructed samples adjacent to the current CU of the current picture of the video data. Based on the selected template being permitted and the determination that the CCCM mode should be used to encode the current CU, the CCCM unit 228 may apply the CCCM mode to predict the chroma samples of the current CU based on the reconstructed luma samples of the current CU and the reference samples in the selected template. Other units of the video encoder 200 may use the predicted chroma samples as described above.

[0093]

[0111] Thus, the video encoder 200 represents an example of a video encoding device that includes a memory configured to store video data and one or more processing units implemented in a circuit configuration and configured to determine whether a selected template is permitted based on a comparison between a threshold value and the amount of reference samples in the selected template. Based on the selected template being permitted and the determination that the convolutional component - to - component model (CCCM) mode should be used, one or more processors may apply the CCCM mode to predict the chroma samples of the current CU based on the reconstructed luma samples of the current CU and the reference samples in the selected template. Additionally, one or more processors may encode the current CU based on the predicted chroma samples of the current CU.

[0094]

[0112] FIG. 3 is a block diagram showing an exemplary video decoder 300 that can implement the techniques of the present disclosure. FIG. 3 is provided for explanation and is not intended to limit the techniques widely exemplified and described in the present disclosure. For the sake of explanation, the present disclosure will describe the video decoder 300 according to the techniques of VVC (ITU-T H.266 under development) and HEVC (ITU-T H.265). However, the techniques of the present disclosure can be implemented by video coding devices configured for other video coding standards.

[0095]

[0113] In the example of FIG. 3, the video decoder 300 includes a coded picture buffer (CPB) memory 320, an entropy decoding unit 302, a prediction processing unit 304, an inverse quantization unit 306, an inverse transform processing unit 308, a reconstruction unit 310, a filter unit 312, and a decoded picture buffer (DPB) 314. Any or all of the CPB memory 320, the entropy decoding unit 302, the prediction processing unit 304, the inverse quantization unit 306, the inverse transform processing unit 308, the reconstruction unit 310, the filter unit 312, and the DPB 314 can be implemented in one or more processors or in processing circuitry. For example, the units of the video decoder 300 can be implemented as one or more circuits or logic elements as part of a hardware circuit, or as part of a processor, ASIC, or FPGA. Moreover, the video decoder 300 may include additional or alternative processors or processing circuitry to implement these and other functions.

[0096]

[0114] The prediction processing unit 304 includes a motion compensation unit 316 and an intra prediction unit 318. The prediction processing unit 304 may include additional units that perform prediction according to other prediction modes. By way of example, the prediction processing unit 304 may include a palette unit, an intra block copy unit (which may form part of the motion compensation unit 316), an affine unit, a linear model (LM) unit, and the like. In other examples, the video decoder 300 may include more, fewer, or different functional components.

[0097]

[0115] When the motion compensation unit 316 operates according to AV1, as described above, it may be configured to decode coding blocks of video data (e.g., both luma coding blocks and chroma coding blocks) using translational motion compensation, affine motion compensation, OBMC, and / or synthetic inter-intra prediction. The intra prediction unit 318 may be configured to decode coding blocks of video data (e.g., both luma coding blocks and chroma coding blocks) using directional intra prediction, non-directional intra prediction, recursive filter intra prediction, CFL, intra block copy (IBC), and / or color palette mode, as described above.

[0098]

[0116] The CPB memory 320 may store video data such as an encoded video bitstream to be decoded by components of the video decoder 300. The video data stored in the CPB memory 320 may be obtained, for example, from a computer-readable recording medium 110 (FIG. 1). The CPB memory 320 may include a CPB that stores encoded video data (e.g., syntax elements) from the encoded video bitstream. Also, the CPB memory 320 may store video data other than syntax elements of the coded picture, such as temporary data representing outputs from various units of the video decoder 300. The DPB 314 generally stores decoded pictures that the video decoder 300 may output and / or use as reference video data when decoding subsequent data or pictures of the encoded video bitstream. The CPB memory 320 and the DPB 314 may be formed by any of various memory devices such as DRAM, including SDRAM, MRAM, RRAM, or other types of memory devices. The CPB memory 320 and the DPB 314 may be provided by the same memory device or separate memory devices. In various examples, the CPB memory 320 may be on-chip with other components of the video decoder 300 or off-chip with respect to those components.

[0099]

[0117] Additionally or alternatively, in some examples, the video decoder 300 may retrieve the encoded video data from the memory 120 (FIG. 1). That is, the memory 120 may store data as discussed above for the CPB memory 320. Similarly, the memory 120 may store instructions to be executed by the video decoder 300 when some or all of the functions of the video decoder 300 are implemented in software to be executed by the processing circuitry of the video decoder 300.

[0100]

[0118] The various units shown in FIG. 3 are shown to assist in understanding the operations performed by the video decoder 300. The units may be implemented as fixed function circuitry, programmable circuitry, or a combination thereof. Similar to FIG. 2, fixed function circuitry refers to circuitry that provides a specific function and the operations that may be performed are pre-set. Programmable circuitry refers to circuitry that may be programmed to perform various tasks and provides a flexible function in the operations that may be performed. For example, programmable circuitry may execute software or firmware that operates the programmable circuitry in a manner defined by software or firmware instructions. Fixed function circuitry may execute software instructions (e.g., receive or output parameters), but the type of operations performed by the fixed function circuitry is generally invariant. In some examples, one or more of the units may be different circuit blocks (fixed function or programmable), and in some examples, one or more of the units may be integrated circuits.

[0101]

[0119] The video decoder 300 may include a programmable core formed from an ALU, EFU, digital circuits, analog circuits, and / or programmable circuits. In an example where the operation of the video decoder 300 is performed by software executed on a programmable circuit, on-chip memory or off-chip memory may store software instructions (e.g., object code) that the video decoder 300 receives and executes.

[0102]

[0120] The entropy decoding unit 302 may receive encoded video data from the CPB and perform entropy decoding on the video data in order to reproduce syntax elements. The prediction processing unit 304, inverse quantization unit 306, inverse transform processing unit 308, reconstruction unit 310, and filter unit 312 may generate decoded video data based on syntax elements extracted from the bitstream.

[0103]

[0121] Generally, the video decoder 300 reconstructs pictures block by block. The video decoder 300 may perform the reconstruction operation individually for each block (the currently reconstructed block, i.e., the decoded block, may sometimes be referred to as the “current block”).

[0104]

[0122] The entropy decoding unit 302 may perform entropy decoding on syntax elements that define quantized transform coefficients of a quantized transform coefficient block, as well as transform information such as a quantization parameter (QP) and / or a transform mode indication(s). The inverse quantization unit 306 may use the QP associated with the quantized transform coefficient block to determine the degree of quantization and likewise the degree of inverse quantization that the inverse quantization unit 306 should apply. The inverse quantization unit 306 may perform, for example, a bitwise left shift operation to inverse quantize the quantized transform coefficients. Thereby, the inverse quantization unit 306 may form a transform coefficient block including transform coefficients.

[0105]

[0123] After the inverse quantization unit 306 forms the transform coefficient block, the inverse transform processing unit 308 may apply one or more inverse transforms to the transform coefficient block to generate a residual block associated with the current block. For example, the inverse transform processing unit 308 may apply an inverse DCT, an inverse integer transform, an inverse Karhunen-Loeve transform (KLT), an inverse rotation transform, an inverse directional transform, or another inverse transform to the transform coefficient block.

[0106]

[0124] Furthermore, the prediction processing unit 304 generates a prediction block according to the prediction information syntax element entropy decoded by the entropy decoding unit 302. For example, if the prediction information syntax element indicates that the current block is inter-predicted, the motion compensation unit 316 may generate a prediction block. In this case, the prediction information syntax element may indicate a reference picture in the DPB 314 from which the reference block should be taken, and a motion vector that identifies the location of the reference block in the reference picture relative to the location of the current block in the current picture. The motion compensation unit 316 can generally perform the inter-prediction process in a manner substantially similar to the manner described with respect to the motion compensation unit 224 (FIG. 2).

[0107]

[0125] As another example, if the prediction information syntax element indicates that the current block is intra-predicted, the intra-prediction unit 318 may generate a prediction block according to the intra-prediction mode indicated by the prediction information syntax element. Also in this case, the intra-prediction unit 318 can generally perform the intra-prediction process in a manner substantially similar to the manner described with respect to the intra-prediction unit 226 (FIG. 2). The intra-prediction unit 318 may retrieve data of adjacent samples for the current block from the DPB 314. In the example of FIG. 3, the intra-prediction unit 318 includes a CCCM unit 322. The CCCM unit 322 may execute the CCCM mode according to the techniques of the present disclosure.

[0108]

[0126] The reconstruction unit 310 may reconstruct the current block using a prediction block and a residual block. For example, the reconstruction unit 310 may add the samples of the residual block to the corresponding samples of the prediction block to reconstruct the current block.

[0109]

[0127] The filter unit 312 may perform one or more filter operations on the reconstructed block. For example, the filter unit 312 may perform a deblocking operation to reduce blocking artifacts along the edges of the reconstructed block. The operation of the filter unit 312 is not necessarily performed in all cases.

[0110]

[0128] The video decoder 300 may store the reconstructed block in the DPB 314. For example, in cases where the operation of the filter unit 312 is not performed, the reconstruction unit 310 may store the reconstructed block in the DPB 314. In cases where the operation of the filter unit 312 is performed, the filter unit 312 may store the filtered and reconstructed block in the DPB 314. As described above, the DPB 314 may provide reference information such as samples of the current picture for intra prediction and previously decoded pictures for subsequent motion compensation to the prediction processing unit 304. Further, the video decoder 300 may output from the DPB 314 a picture (e.g., a decoded video) decoded for later display on a display device such as the display device 118 of FIG. 1.

[0111]

[0129] As described above, the intra prediction unit 318 may include a CCCM unit 332. The CCCM unit 228 may determine whether the selected template is permitted based on a comparison between a threshold value and the amount of reference samples in the selected template. The video decoder 300 may obtain, from the bitstream, a mode index indicating which of a plurality of templates is the selected template. Each of the templates includes a different set of reconstructed samples adjacent to the current CU of the current picture of the video data. Based on the selected template being permitted and the determination that the CCCM mode should be used to encode the current CU, the CCCM unit 322 may apply the CCCM mode to predict the chroma samples of the current CU based on the reconstructed luma samples of the current CU and the reference samples in the selected template. Other units of the video decoder 300 may use the predicted chroma samples as described above.

[0112]

[0130] Thus, the video decoder 300 represents an example of a video decoding device including a memory configured to store video data and one or more processing units implemented in a circuit configuration and configured to determine whether a selected template is permitted based on a comparison between a threshold value and the amount of reference samples in the selected template. Based on the selected template being permitted and the determination that the convolutional component - to - component model (CCCM) mode should be used, one or more processors may apply the CCCM mode to predict the chroma samples of the current CU based on the reconstructed luma samples of the current CU and the reference samples in the selected template. Additionally, one or more processors may decode the current CU based on the predicted chroma samples of the current CU.

[0113]

[0131] Versatile Video Coding (VVC), the latest video coding standard, was developed by the Joint Video Experts Team (JVET) of ITU-T and ISO / IEC to achieve a significant compression capability beyond HEVC for a wide range of applications. The VVC specification was finalized in July 2020 and published by both ITU-T and ISO / IEC. The VVC specification specifies the normative bitstream and picture format, high-level syntax (HLS) and coding unit-level syntax, as well as the parsing and decoding processes. VVC also specifies in the annexes the profile / tiers / levels (PTL) constraints, byte stream format, virtual reference decoder and supplementary enhancement information (SEI).

[0114]

[0132] Since April 2021, JVET has been developing Enhanced Compression Model (ECM) software to enhance the compression capability beyond VVC. The set of coding tools in the ECM software encompasses all the functional blocks within the hybrid video coding framework, including intra prediction, inter prediction, transform and coefficient coding, in-loop filtering, and entropy coding. The techniques of the present disclosure can be applied to ECM, as well as to state-of-the-art video codecs such as VVC and AV1.

[0115]

[0133] ECM-5.0 has 12 intra-modes for chroma intra-mode coding, which are classified into two chroma mode lists: the component-context linear model (CCLM) mode list and the non-CCLM mode list. The CCLM mode list includes six component-context linear model modes, namely, LM, and LM_L, LM_T, MMLM, MMLM_L, and MMLM_T. The non-CCLM mode list includes one chroma DIMD (decoder-side intra mode derivation) mode (Li et al., "EE2-1.2: On chroma intra prediction," Joint Video Experts Team (JVET) of ITU-T SG 16 WP 3 and ISO / IEC JTC 1 / SC 29, 26 Meeting, by teleconference, 20-29 April 2022, document JVET-Z0051-v2 (hereinafter, "JVET-Z0051")), and five traditional intra-modes, namely, direct mode (DM) and the default mode.

[0116]

[0134] The linear model (LM) mode derives a linear model between the luma component and the chroma component, i.e., Pred C =a×Rec L +b. Here, Pred C is the chroma predictor, and Rec Lis a luma same-position reconstruction sample. The LM mode uses a pair of adjacent reconstructed luma pixels and adjacent reconstructed chroma pixels to derive the parameters of the linear model, namely, a and b, using the linear regression approach as shown in FIG. 4. FIG. 4 is a conceptual diagram showing exemplary luma and chroma samples used for the derivation of the linear model. Specifically, FIG. 4 shows a chroma block 400 containing chroma samples and a corresponding luma block 402 containing luma samples. A set of reference samples 404 is arranged above the chroma block 400, and a set of reference samples 406 is arranged to the left of the chroma block 400. A set of reference samples 408 is arranged above the luma block 402, and a set of reference samples 410 is arranged above the luma block 402. The luma block 402 has twice the number of samples (2N) of the chroma block 400 in both the horizontal and vertical directions. For this reason, each chroma sample of the chroma block 400 (as well as each of the reference samples 404 and reference samples 406) corresponds to an intermediate position between two of the luma samples. Thus, as part of determining the linear model, a video coder (e.g., video encoder 200 or video decoder 300) can interpolate the value between a particular luma reference sample 408 and luma reference sample 410. The interpolated value is indicated as a gray-filled circle in FIG. 4. Therefore, the video coder can use the chroma and luma values corresponding to the position indicated by the gray-filled circle to determine the linear model.

[0117]

[0135] FIG. 5 is a conceptual diagram showing an example of classifying adjacent samples into two groups. The plurality of model LM (Multi-model LM, MMLM) modes includes cases where two linear models between the luma adjacent reconstruction samples and the chroma adjacent reconstruction samples are derived by classifying sample pairs into two groups using a threshold value that is the average of the luma adjacent reconstruction samples as shown in FIG. 5. In the example of FIG. 5, the first linear model (represented by line 500) models the linear relationship between the first group of chroma samples 502 and their same-position luma values. The first linear model is defined by a slope value α1 = 2 and an intercept value β1 = 1. The second linear model (represented by line 504) models the linear relationship between the second group of chroma samples 506 and their same-position luma values. The second linear model is defined by a slope value α1 = 1 / 2 and an intercept value β1 = -1.

[0118]

[0136] LM and MMLM use the left samples and the top samples to derive the linear model. LM_L and MMLM_L use only the left samples (without using the top samples) to derive the linear model. Instead, LM_T and MMLM_T use only the top samples (without using the left samples) to derive the linear model.

[0119]

[0137] FIG. 6 is a conceptual diagram showing adjacent reconstructed samples used for chroma decoder side intra mode derivation (DIMD). As shown in FIG. 6, the chroma DIMD mode derives an intra mode based on calculation of a histogram of gradient (HoG) from adjacent reconstructed luma samples of a reconstructed luma block at the same position and adjacent reconstructed chroma samples of the current chroma CU (CU in Cb and Cr components). When one of the default modes, i.e., the planar mode, the horizontal mode, the vertical mode, and the DC mode, is the same as the DM mode, at this time, the default mode is replaced with the diagonal mode. In the example of FIG. 6, block 600A includes luma samples of the current block, block 600B includes Cb samples of the current block, and block 600C includes Cr samples of the current block. Samples outside the squares 600A, 600B, and 600C are adjacent reconstructed samples.

[0120]

[0138] The signaling for the CCLM mode is 10 (LM), 110 (MMLM), 1110 (LM_L), 11110 (LM_A), 111110 (MMLM_L), 111111 (MMLM_A), and the signaling for the non-CCLM mode is 00 for DM, 010 for chroma DIMD, and 01100, 01101, 01110, and 01111 for the default mode. In other words, the CCLM flag for indicating whether the current CU uses one of the CCLM modes is signaled first. If it is the CCLM mode, the LM flag for indicating whether it is the LM mode is signaled first. If the LM flag is false, the MMLM flag for indicating whether it is the MMLM mode is further signaled, and so on. When the CCLM flag indicates that the current CU uses the non-CCLM mode, if it is the DM mode, the DM flag is signaled. If the DM flag is not true, the chroma DIMD flag for indicating whether the mode is the chroma DIMD mode is signaled. If the chroma DIMD mode is not true, the 2-bit fixed-length coding is analyzed to indicate which default mode is used.

[0121]

[0139] ECM-5.0 adopted the slope adjustment techniques for the LM mode and the MMLM mode, which were proposed in Lainema et al., "EE2-1.1: Slope Adjustment for CCLM", Joint Video Experts Team (JVET) of ITU-T SG 16 WP 3 and ISO / IEC JTC 1 / SC 29, 26 Meeting, by teleconference, 20-29 April 2022, document JVET-Z0049 (hereinafter referred to as "JVET-Z0049"), to adjust the slope of the derived linear mode as follows: chromaVal = a’ * lumaVal + b’. Here, a’ = a + u, b’ = b - u * y r where y ris the average of the reference luma samples, u is the delta value for the slope a, chromaVal is the value of the chroma sample, and lumaVal is the value of the corresponding luma sample. JVET-Z0049 is described with respect to ECM, but the techniques of JVET-Z0049 and the techniques of this disclosure may also apply to other video codecs.

[0122]

[0140] Figure 7A is a conceptual diagram showing a model created using an inter-component linear model. In the example of Figure 7A, the vertical axis corresponds to the chroma value (e.g., Cb or Cr), and the horizontal axis corresponds to the luma value. Line 700 shows the linear relationship between the luma values and their co-located chroma values. Point "b" indicates the intercept between the vertical axis and line 700. Line 702 indicates the vertical change value "a" at line 700 at a given position along the horizontal axis. Thus, the vertical change value "a" can be used to determine the slope of line 700.

[0123]

[0141] Figure 7B is a conceptual diagram showing the effect of the slope adjustment parameter using the model created using the model proposed in JVET-Z0049. In the example of Figure 7B, line 700 is the same as line 700 in Figure 7A and shows the linear relationship between the luma values and their co-located chroma values. The delta value u is, in general, an integer from -4 to 4 and is signaled within the bitstream. When one of the LM mode and the MMLM mode is used, a slope adjustment flag is signaled to indicate whether the delta value should be applied to the slope. In the example of Figure 7B, the delta value u (indicated by line 704) changes the slope of line 700, resulting in line 706 having a vertical rise of a' = a + u for the same distance along the horizontal axis as a in Figure 7B.

[0124]

[0142] In ECM-5.0, when the non-CCLM mode is selected, a chroma fusion flag as proposed in JVET-Z0051 is signaled to indicate whether predictors in the non-CCLM mode are fused with predictors in the MMLM mode. The expression "fusion of predictors" may be appropriate for the generation of predictors (e.g., prediction blocks) based on predictors generated using two or more intra prediction modes (e.g., non-LM mode, MMLM mode, etc.).

[0125]

[0143] A convolutional component inter-model (CCCM) mode that uses a 7-tap filter to predict chroma samples from luma samples has been previously proposed, in a similar spirit to that performed by the current CCLM mode. Similar to CCLM, the reconstructed luma samples are downsampled to match a lower-resolution chroma grid when chroma subsampling is used. Also, similar to CCLM, there is an option to use a single-model variant or multiple-model variants of CCCM. FIG. 8 is a conceptual diagram showing the spatial portion 800 of the convolutional filter. Listed below are the inputs to the 7-tap filter: · The central (C) luma sample at the same position as the chroma sample to be predicted · The upper / north (N), lower / south (S), left / west (W), and right / east (E) adjacent samples of the central luma sample as shown in FIG. 8. · The non-linear term P is represented as the square of the central luma sample C and scaled to the sample value range of the content. That is, P = (C * C + midVal) >> bitDepth. That is, for 10-bit content, it is calculated as follows: P = (C * C + 512) >> 10. · The bias term B represents a scalar offset between the input and the output and is set to the intermediate chroma value (512 for 10-bit content), similar to the offset term in CCLM.

[0126]

[0144] The output of the filter is the filter coefficient c iCalculated as a convolution between the predChromaVal = c0C + c1N + c2S + c3E + c4W + c5P + c6B

[0127]

[0145] The CCCM unit (e.g., the CCCM unit 228 of the video encoder 200 or the CCCM unit 322 of the video decoder 300) may determine the coefficients (c0, c1, c2, c3, c4, c5, and c6) using regression based on minimizing the mean - squared error (MSE) with respect to the reference samples of the current block (e.g., the current CU or current PU). In some examples, the CCCM unit may perform MSE minimization by calculating the autocorrelation matrix for the luma input and the cross - correlation vector between the luma input and the chroma output. The CCCM unit may perform an LDL decomposition on the autocorrelation matrix and calculate the final filter coefficients using back substitution.

[0128]

[0146] When the LM flag is true, a CCCM flag may be further signaled to indicate whether it is in the single - model CCCM mode or the normal LM mode. When the MMLM flag is true, a CCCM flag is further signaled to indicate whether it is in the multi - model CCCM mode or the MMLM mode. When the CCCM flag is true, the slope adjustment flag is not signaled and is presumed to be false (invalid) on the decoder side.

[0129]

[0147] As described above, the CCCM unit can determine coefficients for use in a 7-tap filter based on a reference sample. Conventionally, there is only one set of reference samples available for use in determining the coefficients. However, the ability to select between different patterns (i.e., templates) of reference samples can yield better results for predicting chroma samples. For example, if the current CU currently has a chroma gradient from left to right, if the coefficients are determined based on samples to the left of the current CU, the filter may yield a better prediction of the chroma samples of the current CU than the samples above the current CU. Similarly, if the current CU currently has a chroma gradient from top to bottom, if the coefficients are determined based on samples above the current CU, the filter may yield a better prediction of the chroma samples of the current CU than the samples to the left of the current CU. In yet another example, if the coefficients are determined based on at least some of the reference samples above the current CU and at least some of the reference samples to the left of the current CU, the filter may yield a better prediction of the chroma samples of the current CU. However, not all sets of reference samples may be available.

[0130]

[0148] The present disclosure proposes a method in which a template to be used in the current CU by a coding tool, such as the CCCM mode, can be selected from among a plurality of templates. The template can be one of the templates described later (but is not limited thereto).

[0131]

[0149] Full template: Adjacent samples from bottom left to top right as shown in FIG. 9. In other words, FIG. 9 is a conceptual diagram showing the full template 900 used by the current CU902 according to the technique of the present disclosure.

[0132]

[0150] An upper template limited to upper adjacent samples as shown in FIGS. 10A and 10B. Specifically, FIG. 10A is a conceptual diagram showing an upper template 1000A used by the current CU1002 including the upper left sample according to the techniques of the present disclosure. FIG. 10B is a conceptual diagram showing an upper template 1000B used by the current CU1002 excluding the upper left sample according to the techniques of the present disclosure.

[0133]

[0151] A left template limited to left adjacent samples as shown in FIGS. 11A and 11B. FIG. 11A is a conceptual diagram showing a left template 1100A used by the current CU1102 including the upper left sample according to the techniques of the present disclosure. FIG. 11B is a conceptual diagram showing a left template 1100B used by the current CU1102 excluding the upper left sample according to the techniques of the present disclosure.

[0134]

[0152] In another example of the present disclosure, the template is derived from a complete template by geometrically dividing the complete template into N equal templates. In one example, N is 2, and the complete template can be divided into two templates 1202A, 1204A for CU1200 as shown in FIG. 12A and templates 1202B, 1204B for CU1200 in FIG. 12B. FIGS. 12A and 12B are conceptual diagrams showing templates divided from a complete template according to the techniques of the present disclosure. Therefore, in FIGS. 12A and 12B, the first template (e.g., template 1202A or 1204B) and the second template (e.g., template 1204A or 1202B) do not overlap. The first template includes the upper and left samples of the current CU. The second template includes either the upper or left sample of the current CU.

[0135]

[0153] At a picture boundary, the complete template can be equal to either the upper template or the left template. In this case, all the divided templates are on the same side. FIGS. 13A and 13B show this case when N = 2. FIGS. 13A and 13B are conceptual diagrams showing templates on the same side according to the techniques of the present disclosure. Specifically, FIG. 13A shows two or more templates (1302A, 1304A) limited to adjacent reconstruction samples on the left side of the current CU1300. FIG. 13B shows two or more templates (1302B, 1304B) limited to adjacent reconstruction samples above the current CU1300.

[0136]

[0154] In another example, the derivation of the template can be applied to the upper templates (1000A, 1000B) in FIGS. 10A and 10B, and the left templates (1100A, 1100B) in FIGS. 11A and 11B.

[0137]

[0155] The number of reference samples in the complete template, template 1, and template 2 are represented as nSample_F, nSample_1, and nSample_2, respectively, where template 1 and template 2 can be derived templates divided from the complete template. In another example, template 1 is the upper template and template 2 is the left template. To infer which template is used, the following constraints are proposed: · If nSample_F < threshold1, the complete template is rejected from being used in the current CU. · If nSample_1 < threshold2, template 1 is rejected from being used in the current CU. · If nSample_2 < threshold2, template 2 is rejected from being used in the current CU.

[0138]

[0156] Note that threshold1 and threshold2 are predefined positive integers. In one example, threshold1 = threshold2. In another example, threshold1 < threshold2. In another example, threshold1 and threshold2 depend on the mode index. For example, when the mode index indicates that it is in the single model linear model mode, threshold1 and threshold2 are set to threshold1_s and threshold2_s. Instead, when the mode index indicates that it is in the multiple model linear model mode, threshold1 and threshold2 are set to threshold1_m and threshold2_m. In one example, threshold1_s and threshold1_m are the same. In another example, threshold1_s and threshold1_m are different and threshold1_s < threshold1_m. The same comparison relationship can apply to threshold2_s and threshold2_m.

[0139]

[0157] In this way, a video coder (e.g., the CCCM unit 228 of the video encoder 200 or the CCCM unit 322 of the video decoder 300) may reject one or more templates among a plurality of templates based on a comparison between the amount of samples in a template and a threshold for the plurality of templates. For example, the video coder may reject a first template (e.g., a complete template including adjacent reconstructed samples above and to the left of the current CU) based on the fact that the amount of samples (nSample_F) in the first template is less than a first threshold (threshold1). The video coder may reject a second template (e.g., template 1 limited to adjacent reconstructed samples above the current CU) based on the fact that the amount of samples (nSample_1) in the second template is less than a second threshold (threshold2). The video coder may reject a third template (e.g., template 2 limited to adjacent reconstructed samples to the left of the current CU) based on the fact that the amount of samples (nSample_2) in the third template is less than the second threshold (threshold2).

[0140]

[0158] The video coder may encode or decode a mode index indicating the selected template. In some examples, the video coder may encode or decode a mode index indicating which of the plurality of templates is used for the current CU and how many linear models are used for the current CU. For example, when the template selection method is applied to CCCM, the following signaling may apply: · First, a mode index indicating which template is used and how many linear models are used is signaled (e.g., index 0 is a single model using the complete template, index 1 is multiple models using the complete template, index 2 is a single model using template 1, index 3 is a single model using template 2, index 4 is multiple models using template 1, index 5 is multiple models using template 2). A CCCM flag is signaled to indicate whether a normal linear model is used (CCCM flag is 0) or CCCM is used (CCCM flag is 1). If the mode index indicates that multiple models using template 1 are used and nSample_1 < threshold2_m, the CCCM flag is presumed to be 0. If the mode index indicates that multiple models using template 2 are used and nSample_2 < threshold2_m, the CCCM flag is presumed to be 0. If the mode index indicates that a single model using template 1 is used and nSample_1 < threshold2_s, the CCCM flag is presumed to be 0. If the mode index indicates that a single model using template 2 is used and nSample_2 < threshold2_s, the CCCM flag is presumed to be 0.

[0141]

[0159] Therefore, the video coder may determine whether the selected template is permitted based on a comparison between thresholds (e.g., threshold1, threshold2, threshold2_s, threshold2_m) and the amount of reference samples within the selected template. The mode index may indicate which one of a plurality of templates (e.g., a full template, template 1, or template 2) is the selected template. As described above, each of the templates includes a different set of reconstructed samples adjacent to the current CU. Based on the determination that the selected template is permitted and that the CCCM mode should be used, the video coder may apply the CCCM mode to predict the chroma samples of the current CU based on the reconstructed luma samples of the current CU and the reference samples within the selected template. (e.g., because nSample_F < threshold1, nSample_1 < threshold2, or nSample_2 < threshold2, nSample_1 < threshold2_m, nSample_2 < threshold2_m, or nSample_2 < threshold2_s) If the selected template is not permitted, the CCCM flag is presumed to be 0, and thus, the CCCM mode is not used.

[0142]

[0160] Next, the chroma fusion method is described. The present disclosure proposes replacing the fusion of predictors in the non-CCLM mode and predictors in the MMLM mode with the fusion of predictors in the non-CCLM mode and predictors in the multiple-model CCCM mode. When nSample_F < threshold1_m, signaling of the chroma fusion flag is bypassed and is presumed to be 0 on the decoder side. In another example, a predictor in the non-CCLM mode is fused with one of the linear model modes based on the condition nSample_F ≥ threshold1_m. One example is that when nSample_F < threshold1_m, the predictor in the non-CCLM mode is fused with the predictor in the single-model CCCM mode, and when nSample_F ≥ threshold1_m, the predictor in the non-CCLM mode is fused with the predictor in the multiple-model CCCM mode.

[0143]

[0161] Further, the lengths of the upper and left CU boundaries (indicated as length_b, where length_b = CU_width + CU_height, CU_width is the width of the CU, and CU_height is the height of the CU) are below a threshold (indicated as threshold_f), i.e., when length_b ≤ threshold_f, it is proposed to bypass the signaling of the chroma fusion flag. The condition length_b ≤ threshold_f can be combined with one or at least two of the above-described conditions. One example is that when length_b ≤ threshold_f and nSample_F < threshold1_m, the signaling of the chroma fusion flag is bypassed.

[0144]

[0162] FIG. 14 is a flowchart showing an exemplary method of encoding a current block according to the techniques of the present disclosure. The current block may include the current CU. Although described with respect to the video encoder 200 (FIGS. 1 and 2), it should be understood that other devices may be configured to perform a method similar to the method of FIG. 14.

[0145]

[0163] In this example, the video encoder 200 first predicts the current block (1450). For example, the video encoder 200 may form a predicted block for the current block. According to the techniques of the present disclosure, the video encoder 200, as part of forming the predicted block, based on a comparison between a threshold value and the amount of reference samples in a selected template that indicates which of a plurality of templates the selected template is, in terms of the mode index, may determine whether the selected template is permitted. Based on determining that the selected template is permitted and that the CCCM mode should be used, the video decoder 300 may apply the CCCM mode to predict the chroma samples of the current block based on the reconstruction luma samples of the current block and the reference samples in the selected template.

[0146]

[0164] The video encoder 200 may then calculate a residual block for the current block (1452). To calculate the residual block, the video encoder 200 may calculate the difference between the original unencoded block and the predicted block for the current block. The video encoder 200 may then transform the residual block and quantize the transform coefficients of the residual block (1454). Next, the video encoder 200 may scan the quantized transform coefficients of the residual block (1456). During or following the scan, the video encoder 200 may entropy encode the transform coefficients (1458). For example, the video encoder 200 may encode the transform coefficients using CAVLC or CABAC. The video encoder 200 may then output the entropy encoded data of the block (1460).

[0147]

[0165] FIG. 15 is a flowchart showing an exemplary method for decoding a current block of video data according to the techniques of the present disclosure. The current block may include a current CU. Although described with respect to video decoder 300 (FIGS. 1 and 3), it should be understood that other devices may be configured to implement a method similar to the method of FIG. 15.

[0148]

[0166] Video decoder 300 may receive entropy-encoded data for the current block, such as entropy-encoded prediction information and entropy-encoded data for the transform coefficients of the residual block corresponding to the current block (1570). Video decoder 300 may entropy-decode the entropy-encoded data to determine prediction information for the current block and reproduce the transform coefficients of the residual block (1572). Video decoder 300 may predict the current block using, for example, an intra prediction mode or an inter prediction mode indicated by the prediction information for the current block to calculate a prediction block for the current block (1574). According to the techniques of the present disclosure, video decoder 300, as part of calculating the prediction block, may determine whether the selected template is permitted based on a comparison of a threshold with the amount of reference samples in the selected template, where the mode index indicates which of the plurality of templates is the selected template, and may determine. Based on determining that the selected template is permitted and that the CCCM mode should be used, video decoder 300 may apply the CCCM mode to predict the chroma samples of the current block based on the reconstructed luma samples of the current block and the reference samples in the selected template.

[0149]

[0167] The video decoder 300 may then inverse scan the reconstructed transform coefficients (1576) to generate a block of quantized transform coefficients. The video decoder 300 may then inverse quantize the transform coefficients and apply an inverse transform to the transform coefficients to generate a residual block (1578). The video decoder 300 may finally decode the current block by combining the prediction block and the residual block (1580).

[0150]

[0168] FIG. 16 is a flowchart illustrating an exemplary method of encoding or decoding video data according to the techniques of the present disclosure. In the example of FIG. 16, a CCCM unit (e.g., the CCCM unit 228 of the video encoder 200 or the CCCM unit 322 of the video decoder 300) may determine whether a selected template is permitted based on a comparison of a threshold value and the amount of reference samples within the selected template (1600). A mode index may indicate which of a plurality of templates is the selected template. Each of the templates includes a different set of reconstructed samples adjacent to the current CU of the current picture of the video data.

[0151]

[0169] For example, the plurality of templates may include a first template that includes adjacent reconstructed samples above and to the left of the current CU, a second template that is limited to adjacent reconstructed samples above the current CU, and a third template that is limited to adjacent reconstructed samples to the left of the current CU. The CCCM unit may reject the first template based on the amount of samples in the first template being less than a first threshold value. The CCCM unit may reject the second template based on the amount of samples in the second template being less than a second threshold value. The CCCM unit may reject the third template based on the amount of samples in the third template being less than the second threshold value. In some examples, the first threshold value is equal to the second threshold value. In other examples, the first threshold value is less than the second threshold value. In some examples, at least one of the first threshold value or the second threshold value depends on the mode index.

[0152]

[0170] In some examples, the plurality of templates includes two or more templates limited to adjacent reconstruction samples above the current CU (as shown in the example of FIG. 13B, for example), or two or more templates limited to adjacent reconstruction samples to the left of the current CU (as shown in the example of FIG. 13A, for example). In some examples, such as the examples of FIGS. 12A and 12B, the plurality of templates includes a non-overlapping first template and a second template, the first template includes samples above and to the left of the current CU, and the second template includes samples either above or to the left of the current CU. In some examples, the video coder may encode or decode a mode index that indicates, for example, which of the plurality of templates is used for the current CU and how many linear models are used for the current CU, as described above.

[0153]

[0171] Further, in the example of FIG. 16, the CCCM unit may apply the CCCM mode (1602) to predict the chroma samples of the current CU based on the reconstructed luma samples of the current CU and the reference samples within the selected template. For example, the CCCM unit may downsample the reconstructed luma samples of the current CU and apply a 7-tap filter to the luma samples of the downsampled luma block to predict the chroma samples of the current CU. The 7-tap filter uses the center, left, right, top, and bottom luma samples of the downsampled luma block, as well as a bias term, and a non-linear term represented as the square of the center luma sample C, scaled to the sample value range of the content. The CCCM unit may determine the coefficients of the 7-tap filter based on the reference samples within the selected template.

[0154]

[0172] A video coder (e.g., video encoder 200 or video decoder 300) including a CCCM unit may encode or decode a current CU based on predicted chroma samples for the current CU (1604). For example, the residual generation unit 204 of the video encoder 200 may generate residual data based on the predicted chroma samples for the current CU and the original chroma samples of the current CU. In this example, the conversion processing unit 206 of the video encoder 200 may apply a conversion to the residual data to generate a conversion block. The quantization unit 208 of the video encoder 200 may quantize the conversion coefficients of the conversion block. The entropy encoding unit 220 of the video encoder 200 may apply entropy encoding to the quantized conversion coefficients. In an example where the video coder is the video decoder 300, the reconstruction unit 310 may reconstruct the chroma samples of the current CU based on the predicted chroma samples for the current CU and the reconstructed residual data.

[0155]

[0173] The following is a non-limiting list of clauses according to the techniques of the present disclosure.

[0156]

[0174] Clause 1A: A method of coding video data includes selecting a template including adjacent reconstruction samples of a current coding unit (CU) of a current picture of the video data, applying a coding tool that uses the selected template to perform intra prediction to generate a predictor for the current CU, and encoding or decoding the current CU based on the predictor for the current CU.

[0157]

[0175] Clause 2A: The method according to Clause 1A, wherein selecting the template includes selecting a template from a plurality of templates including two or more of a first template including adjacent reconstruction samples above and to the left of the current CU, a second template limited to adjacent reconstruction samples above the current CU, and a third template limited to adjacent reconstruction samples to the left of the current CU.

[0158]

[0176] Clause 3A: The method according to Clause 1A, wherein selecting a template includes selecting a template from among a plurality of templates including two or more templates limited to adjacent reconstruction samples above the current CU or two or more templates limited to adjacent reconstruction samples to the left of the current CU, based on the fact that the current CU is currently at the edge of the current picture.

[0159]

[0177] Clause 4A: The method according to any one of Clauses 1A to 3A, wherein selecting a template includes rejecting one or more templates among a plurality of templates based on a comparison between the amount of samples in the template and a threshold for the plurality of templates.

[0160]

[0178] Clause 5A: The first template includes adjacent reconstruction samples above and to the left of the current CU, the second template is limited to adjacent reconstruction samples above the current CU, the third template is limited to adjacent reconstruction samples to the left of the current CU, and selecting a template includes rejecting the first template based on the fact that the amount of samples in the first template is less than a first threshold, rejecting the second template based on the fact that the amount of samples in the second template is less than a second threshold, and rejecting the third template based on the fact that the amount of samples in the third template is less than the second threshold, the method according to any one of Clauses 1A to 4A.

[0161]

[0179] Clause 6A: The method according to Clause 5A, wherein either the first threshold is equal to the second threshold or the first threshold is less than the second threshold.

[0162]

[0180] Clause 7A: The method according to Clause 5A or 6A, wherein at least one of the first threshold or the second threshold depends on a mode index.

[0163]

[0181] Clause 8A: The method according to any one of Clauses 1A to 6A, wherein the coding tool is one of a convolutional component - to - component model (CCCM) for intra prediction, an inter - component linear model using slope adjustment, or chroma fusion.

[0164]

[0182] Clause 9A: The method according to any one of Clauses 1A to 8A, wherein the coding tool is a CCCM for intra prediction, and encoding or decoding a mode index that indicates which template among a plurality of templates is used for the current CU and how many linear models are used for the current CU.

[0165]

[0183] Clause 10A: The predictor is a first predictor, the coding tool is a first coding tool, the first coding tool is in a multi - model CCCM mode, the first template includes adjacent reconstructed samples above and to the left of the current CU, the method further includes determining that a chroma fusion flag is signaled in a bitstream including an encoded representation of video data based on the amount of samples in the first template being less than a threshold, and applying a second coding tool, wherein the second coding tool is in a non - inter - component linear model mode, to perform intra prediction to generate a second predictor for the current CU, and encoding or decoding the current CU includes encoding or decoding the current CU based on the first and second predictors for the current CU, the method according to any one of Clauses 1A to 9A.

[0166]

[0184] Clause 11A: The method according to any one of Clauses 1A to 9A, further including determining that a chroma fusion flag, which indicates whether a predictor of a non - inter - component linear model (non - CCLM) model is fused with a predictor of a multi - model CCCM mode, is bypassed in a bitstream including an encoded representation of video data, at least partially based on the lengths of the upper and left boundaries of the current CU being less than a threshold.

[0167]

[0185] Clause 12A: A device for coding video data, the device comprising one or more means for implementing the method according to any one of Clauses 1A to 11A.

[0168]

[0186] Clause 13A: The device according to Clause 12A, wherein one or more means include one or more processors implemented in a circuit configuration.

[0169]

[0187] Clause 14A: The device according to Clause 12A or 14A, further comprising a memory for storing video data.

[0170]

[0188] Clause 15A: The device according to any one of Clauses 12A to 14A, further comprising a display configured to display the decoded video data.

[0171]

[0189] Clause 16A: The device according to any one of Clauses 12A to 15A, wherein the device comprises one or more of a camera, a computer, a mobile device, a broadcast receiver device, or a set-top box.

[0172]

[0190] Clause 17A: The device according to any one of Clauses 12A to 16A, wherein the device comprises a video decoder.

[0173]

[0191] Clause 18A: The device according to any one of Clauses 12A to 17A, wherein the device comprises a video encoder.

[0174]

[0192] Clause 19A: A computer-readable storage medium storing instructions which, when executed, cause one or more processors to execute the method according to any one of Clauses 1A to 11A.

[0175]

[0193] Method for coding video data, the method comprising: a threshold value; a selected template, wherein a mode index indicates which of a plurality of templates is the selected template, each of the templates comprising a different set of reconstructed samples adjacent to the current coding unit (CU) of the current picture of the video data; determining whether the selected template is permitted based on a comparison of the amount of reference samples within the selected template with the threshold value; based on determining that the selected template is permitted and that a convolutional component - to - component model (CCCM) mode should be used, applying the CCCM mode to predict the chroma samples of the current CU based on the reconstructed luma samples of the current CU and the reference samples within the selected template; and encoding or decoding the current CU based on the predicted chroma samples of the current CU.

[0176]

[0194] Clause 2B. The method according to Clause 1B, wherein the plurality of templates includes two or more of: a first template including the upper and left adjacent reconstructed samples of the current CU; a second template limited to the upper adjacent reconstructed samples of the current CU; and a third template limited to the left adjacent reconstructed samples of the current CU.

[0177]

[0195] Clause 3B. The method according to Clause 2B, wherein the threshold value is one of a first threshold value or a second threshold value, and determining whether the selected template is permitted includes rejecting the first template based on the amount of samples in the first template being less than the first threshold value, rejecting the second template based on the amount of samples in the second template being less than the second threshold value, and rejecting the third template based on the amount of samples in the third template being less than the second threshold value.

[0178]

[0196] Clause 4B. The method according to Clause 3B, wherein the first threshold value is either equal to the second threshold value or less than the second threshold value.

[0179]

[0197] The method according to clause 3B or 4B, wherein at least one of the first threshold value or the second threshold value depends on the mode index.

[0180]

[0198] The method according to any one of clauses 1B to 5B, wherein, based on the current CU being at the edge of the current picture, the plurality of templates includes either two or more templates limited to the adjacent reconstruction samples above the current CU or two or more templates limited to the adjacent reconstruction samples to the left of the current CU.

[0181]

[0199] The method according to any one of clauses 1B to 5B, wherein the plurality of templates includes a non-overlapping first template and a second template, the first template includes samples above and to the left of the current CU, and the second template includes samples either above or to the left of the current CU.

[0182]

[0200] The method according to any one of clauses 1B to 7B, wherein the method further includes encoding or decoding a mode index, and the mode index also indicates how many linear models are used for the current CU.

[0183]

[0201] The method according to any one of clauses 1B to 8B, wherein applying the CCCM mode includes determining filter coefficients based on reference samples in the selected template, downsampling the reconstructed luma samples of the current CU to generate a downsampled luma block, and applying a 7-tap filter to the luma samples of the downsampled luma block to predict the chroma samples of the current CU.

[0184]

[0202] Clause 10B. A device for encoding or decoding video data, the device comprising: a memory configured to store video data; one or more processors implemented in a circuit configuration, the one or more processors configured to compare a threshold value with an amount of reference samples within a selected template, the mode index indicating which template among a plurality of templates is the selected template, each template including a different set of reconstructed samples adjacent to the current coding unit (CU) of the current picture of the video data, and based on the comparison, determine whether the selected template is permitted, and if the selected template is permitted and it is determined that the convolutional component - to - component model (CCCM) mode should be used, apply the CCCM mode to predict chroma samples of the current CU based on the reconstructed luma samples of the current CU and the reference samples within the selected template, and encode or decode the current CU based on the predicted chroma samples of the current CU.

[0185]

[0203] Clause 11B. The device according to Clause 10B, wherein the plurality of templates includes two or more of: a first template including adjacent reconstructed samples above and to the left of the current CU; a second template limited to adjacent reconstructed samples above the current CU; and a third template limited to adjacent reconstructed samples to the left of the current CU.

[0186]

[0204] Clause 12B. The device according to Clause 11B, wherein the threshold value is one of a first threshold value or a second threshold value, and as part of the one or more processors determining whether the selected template is permitted, reject the first template based on the amount of samples in the first template being less than the first threshold value, reject the second template based on the amount of samples in the second template being less than the second threshold value, and reject the third template based on the amount of samples in the third template being less than the second threshold value.

[0187]

[0205] The device according to clause 12B, wherein either the first threshold is equal to the second threshold or the first threshold is less than the second threshold.

[0188]

[0206] The device according to clause 12B or 13B, wherein at least one of the first threshold or the second threshold depends on a mode index.

[0189]

[0207] The device according to any one of clauses 10B to 14B, wherein, based on the current CU being at the edge of the current picture, the plurality of templates includes either two or more templates limited to adjacent reconstruction samples above the current CU or two or more templates limited to adjacent reconstruction samples to the left of the current CU.

[0190]

[0208] The device according to any one of clauses 10B to 14B, wherein the plurality of templates includes a non - overlapping first template and a second template, the first template includes samples above and to the left of the current CU, and the second template includes samples either above or to the left of the current CU.

[0191]

[0209] The device according to any one of clauses 10B to 16B, wherein one or more processors are further configured to encode or decode a mode index, and the mode index also indicates how many linear models are used for the current CU.

[0192]

[0210] Clause 18B. One or more processors are configured as part of applying the CCCM mode to determine filter coefficients based on reference samples in a selected template and to downsample the reconstruction luma samples of the current CU to generate a downsampled luma block and apply a 7-tap filter to the luma samples of the downsampled luma block to predict the chroma samples of the current CU, a device according to any one of Clauses 10B to 17B.

[0193]

[0211] Clause 19B. A device according to any one of Clauses 10B to 18B, further comprising a display configured to display the decoded video data.

[0194]

[0212] Clause 20B. A device according to any one of Clauses 10B to 19B, wherein the device includes one or more of a camera, a computer, a mobile device, a broadcast receiver device, or a set-top box.

[0195]

[0213] Clause 21B. A device according to any one of Clauses 10B to 20B, wherein the device comprises a video decoder.

[0196]

[0214] Clause 22B. A device according to any one of Clauses 10B to 21B, wherein the device comprises a video encoder.

[0197]

[0215] Clause 23B. A non-transitory computer-readable storage medium storing instructions which, when executed, cause one or more processors to compare a threshold with an amount of reference samples in a selected template, the mode index indicating which of a plurality of templates is the selected template, each template including a different set of reconstructed samples adjacent to a current coding unit (CU) of a current picture of video data, to determine whether the selected template is permitted based on the comparison, and, based on determining that the selected template is permitted and that a convolutional component-context model (CCCM) mode should be used, apply the CCCM mode to predict chroma samples of the current CU based on reconstructed luma samples of the current CU and reference samples in the selected template, and encode or decode the current CU based on the predicted chroma samples of the current CU.

[0198]

[0216] Clause 24B. A device for encoding or decoding video data, the device comprising means for comparing a threshold with an amount of reference samples in a selected template, the mode index indicating which of a plurality of templates is the selected template, each template including a different set of reconstructed samples adjacent to a current coding unit (CU) of a current picture of video data, to determine whether the selected template is permitted; means for applying a convolutional component-context model (CCCM) mode to predict chroma samples of the current CU based on reconstructed luma samples of the current CU and reference samples in the selected template, based on determining that the selected template is permitted and that the CCCM mode should be used; and means for encoding or decoding the current CU based on the predicted chroma samples of the current CU.

[0199]

[0217] In some examples, it should be recognized that some of the acts or events of any of the techniques described herein may be performed in a different order, may be added, merged, or completely excluded (e.g., not all of the acts or events described are necessary for the practice of the technique). Moreover, in some examples, the acts or events may not be performed sequentially, but may be performed in parallel, for example, through multi-threading, interrupt processing, or multiple processors.

[0200]

[0218] In one or more examples, the functions described may be implemented in hardware, software, firmware, or any combination thereof. When implemented in software, the functions may be stored on or transmitted via a computer-readable recording medium as one or more instructions or codes and may be executed by a hardware-based processing unit. The computer-readable recording medium may include a computer-readable storage medium corresponding to a tangible medium such as a data storage medium, or a communication medium including any medium that facilitates transfer of a computer program from one place to another, for example, according to a communication protocol. Thus, the computer-readable recording medium generally may correspond to (1) a tangible computer-readable storage medium that is non-transitory, or (2) a communication medium such as a signal or a carrier wave. The data storage medium may be any available medium that can be accessed by one or more computers or one or more processors to retrieve instructions, codes, and / or data structures for implementing the techniques described in this disclosure. A computer program product may include a computer-readable recording medium.

[0201]

[0219] By way of example and not limitation, such a computer-readable storage medium can include RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage, or other magnetic storage devices, flash memory, or any other medium that can be used to store the desired program code in the form of instructions or data structures and that can be accessed by a computer. Also, any connection can appropriately be called a computer-readable recording medium. For example, if the instructions are transmitted from a website, server, or other remote source using coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared, radio, and microwave, then the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are included in the definition of the medium. However, it should be understood that the computer-readable storage medium and data storage medium do not include connections, carrier waves, signals, or other transient media, but rather are directed to non-transient tangible storage media. As used herein, disk and disc include compact disc (CD), laser disc, optical disc, digital versatile disc (DVD), floppy disk, and Blu-ray disc, where disk typically magnetically reproduces data, while disc optically reproduces data using a laser. Combinations of the above should also be included within the scope of computer-readable recording media.

[0202]

[0220] The commands may be executed by one or more processors, such as one or more DSPs, general-purpose microprocessors, ASICs, FPGAs, or other equivalent integrated logic circuits or discrete logic circuits. Thus, the terms "processor" and "processing circuit" as used herein may refer to either the structures described above or any other structure suitable for implementing the techniques described herein. Additionally, in some aspects, the functions described herein may be provided within dedicated hardware modules and / or software modules configured for encoding and decoding, or may be incorporated within a combined codec. Further, the techniques may be implemented entirely in one or more circuits or logic elements.

[0203]

[0221] The techniques of the present disclosure may be implemented in a variety of devices or apparatuses, including wireless handsets, integrated circuits (ICs), or sets of ICs (e.g., chip sets). To emphasize the functional aspects of devices configured to implement the disclosed techniques, various components, modules, or units have been described in this disclosure, but they do not necessarily require implementation by different hardware units. Rather, as described above, the various units may be combined in codec hardware units, or may be provided by a set of interoperable hardware units including one or more of the processors described above in cooperation with suitable software and / or firmware.

Claims

1. A method for coding video data, Based on a comparison between a threshold and the amount of reference samples in the selected template, it is determined whether the selected template is permitted, wherein the mode index indicates which of a plurality of templates is the selected template, each of the templates contains a different set of reconstructed luma samples adjacent to the current coding unit (CU) of the current picture of the video data, and the plurality of templates are A first template including adjacent reconstructed luma samples above and to the left of the current CU, The second template is currently limited to the adjacent reconstructed luma sample above the CU, or The third template is currently limited to the adjacent reconstructed luma sample on the left side of the CU. Includes two or more of the following: The threshold is either the first threshold or the second threshold, and the determination of whether the selected template is permitted is made. Rejecting the first template based on the fact that the amount of samples in the first template is less than the first threshold, Rejecting the second template based on the fact that the amount of samples in the second template is less than the second threshold, and Rejecting the third template based on the fact that the amount of samples in the third template is less than the second threshold, including, Based on the determination that the selected template is permitted and that the convolutional component-intercomponent model (CCCM) mode should be used for intraprediction, the CCCM mode is applied to predict the chroma sample of the current CU based on the reconstructed lumens sample of the current CU and the reference sample in the selected template. Encoding or decoding the current CU based on the predicted chroma sample of the current CU, Methods that include...

2. The first threshold is equal to the second threshold, or The method according to claim 1, wherein the first threshold is less than the second threshold.

3. The method according to claim 1, wherein at least one of the first threshold or the second threshold depends on the mode index.

4. Based on the fact that the current CU is at the edge of the current picture, the multiple templates are, Two or more templates limited to the adjacent reconstructed luma sample above the current CU, or Two or more templates limited to the adjacent reconstructed luma sample to the left of the current CU, The method according to claim 1, comprising either of the above.

5. The aforementioned plurality of templates include a first template and a second template that do not overlap, The first template includes the upper and left lumens of the current CU, The method according to claim 1, wherein the second template includes a lumen sample either above or to the left of the current CU.

6. The method further includes encoding or decoding the mode index, The method according to claim 1, wherein the mode index also indicates how many linear models are currently used for the CU.

7. Applying the CCCM mode means Determine the filter coefficients based on the reference samples within the selected template. Downsampling the reconstructed rumor sample of the current CU in order to generate a downsampled rumor block, and To predict the chroma sample of the current CU, a 7-tap filter is applied to the luma sample of the downsampled luma block. The method according to claim 1, including the method described in claim 1.

8. A device for encoding or decoding video data, wherein the device is A memory configured to store the aforementioned video data, One or more processors implemented in a circuit configuration, wherein the one or more processors Based on a comparison between a threshold and the amount of reference samples in the selected template, it is determined whether the selected template is permitted, wherein the mode index indicates which of the multiple templates is the selected template, each of the templates contains a different set of reconstructed luma samples adjacent to the current coding unit (CU) of the current picture of the video data, and the multiple templates are, A first template including adjacent reconstructed luma samples above and to the left of the current CU, The second template is currently limited to the adjacent reconstructed luma sample above the CU, or The third template is currently limited to the adjacent reconstructed luma sample on the left side of the CU. Includes two or more of the following: The threshold is either a first threshold or a second threshold, and the one or more processors, as part of determining whether the selected template is permitted, The first template is rejected based on the fact that the amount of samples in the first template is less than the first threshold. The second template is rejected based on the fact that the amount of samples in the second template is less than the second threshold. The third template is rejected based on the fact that the amount of samples in the third template is less than the second threshold. It is structured in such a way. Based on the determination that the selected template is permitted and that the convolutional component-intercomponent model (CCCM) mode should be used for intraprediction, the CCCM mode is applied to predict the chroma sample of the current CU based on the reconstructed lumens sample of the current CU and the reference sample in the selected template. The current CU is encoded or decoded based on the predicted chroma sample of the current CU. One or more processors configured in such a way, A device equipped with the following features.

9. The first threshold is equal to the second threshold, or The device according to claim 8, wherein the first threshold is less than the second threshold, or the other.

10. The device according to claim 8, further comprising means for carrying out the method described in any one of claims 3 to 7.

11. The device according to claim 8, further comprising a display configured to display decoded video data.

12. The device according to claim 8, wherein the device comprises one or more of a camera, a computer, a mobile device, a broadcast receiver device, or a set-top box.

13. The device according to claim 8, wherein the device comprises a video decoder.

14. The device according to claim 8, wherein the device comprises a video encoder.

15. A non-temporary computer-readable storage medium, comprising an instruction, wherein, when the instruction is executed, one or more processors, Based on a comparison between a threshold and the amount of reference samples in the selected template, it is determined whether the selected template is permitted, where the mode index indicates which of a plurality of templates is the selected template, each of the templates contains a different set of reconstructed luma samples adjacent to the current coding unit (CU) of the current picture of the video data, and the plurality of templates, A first template including adjacent reconstructed luma samples above and to the left of the current CU, The second template is currently limited to the adjacent reconstructed luma sample above the CU, or The third template is currently limited to the adjacent reconstructed luma sample on the left side of the CU. Includes two or more of the following: The threshold is one of the first threshold or the second threshold, and the instruction further, as part of determining whether the selected template is permitted to the one or more processors, Rejecting the first template based on the fact that the amount of sample in the first template is less than the first threshold, The second template is rejected based on the fact that the amount of sample in the second template is less than the second threshold, and The third template is rejected based on the fact that the amount of sample in the third template is less than the second threshold. To have them do it, Based on the determination that the selected template is permitted and that the convolutional component-intercomponent model (CCCM) mode should be used for intraprediction, the CCCM mode is applied to predict the chroma sample of the current CU based on the reconstructed lumens sample of the current CU and the reference sample in the selected template. The current CU is encoded or decoded based on the predicted chroma sample of the current CU. A non-temporary, computer-readable storage medium that stores instructions.

Images