DC intra mode prediction in video coding

Abstract

This disclosure describes examples for determining samples to be used for DC intra mode prediction, such as where the samples are located in rows or columns that are not immediately above or not immediately on the left side of the current block. The samples may be aligned with the current block such that the last one of the samples in a row above the current block is in the same column as the last column of the current block, and such that the last one of the samples in a column left of the current block is in the same row as the last row of the current block.

Description

[0001] This application is a divisional application of the application filed on December 13, 2021, with application number 202080043173.5 and invention name “DC intra-frame mode prediction in video decoding”.

[0002] Related Applications

[0003] This application claims priority to U.S. Application No. 16 / 905,352, filed on June 18, 2020, which claims the benefit of U.S. Provisional Patent Application 62 / 864,422, filed on June 20, 2019, and U.S. Provisional Patent Application 62 / 866,325, filed on June 25, 2019, the entire contents of each of the above applications are incorporated by reference. Technical Field

[0004] The present disclosure relates to video encoding and video decoding. Background Art

[0005] Digital video capabilities may be incorporated into a wide variety of devices, including digital televisions, digital live broadcast systems, wireless broadcast systems, personal digital assistants (PDAs), laptop or desktop computers, tablet computers, e-book readers, digital cameras, digital recording devices, digital media players, video game devices, video game consoles, cellular or satellite radio telephones (so-called "smart phones"), video teleconferencing devices, video streaming devices, etc. Digital video devices implement video coding techniques (such as those described in the 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), and extensions of such standards). By implementing such video coding techniques, video devices may more efficiently send, receive, encode, decode, and / or store digital video information.

[0006] Video coding techniques include spatial (intra-picture) prediction and / or temporal (inter-picture) prediction to reduce or remove redundancy inherent in video sequences. For 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 in an intra-coded (I) slice of a picture are encoded using spatial prediction relative to reference samples in neighboring blocks in the same picture. Video blocks in an inter-coded (P or B) slice of a picture may use spatial prediction relative to reference samples in neighboring blocks in the same picture or temporal prediction relative to reference samples in other reference pictures. Pictures may be referred to as frames, and reference pictures may be referred to as reference frames. Summary of the invention

[0007] In summary, the present disclosure describes techniques for DC intra mode prediction, including improvements to determining samples for DC intra mode prediction. For example, in one or more examples, for DC intra mode prediction, a video coder (e.g., a video encoder or a video decoder) may utilize one or more samples in rows or columns that are not directly adjacent to a current block being coded (e.g., encoded or decoded). The present disclosure describes example techniques in which samples in non-adjacent rows or columns are aligned with the current block.

[0008] As an example, when the last sample in a non-contiguous row has the same x-coordinate as the last column of the current block, the samples of the non-contiguous row are aligned with the current block. As an example, when the last sample in a non-contiguous column has the same y-coordinate as the last row of the current block, the samples of the non-contiguous column are aligned with the current block. In some examples, the first sample in a non-contiguous row has the same x-coordinate as the first column of the current block, and the first sample in a non-contiguous column has the same y-coordinate as the first row of the current block.

[0009] By utilizing samples from non-adjacent rows or columns that are aligned with the current block, the video decoding process can be improved. As an example, for DC intra-mode prediction, samples from non-adjacent rows or columns that are aligned with the current block can generally form a better predicted block (e.g., in terms of smaller residual values) than misaligned samples from non-adjacent rows or columns.

[0010] In addition, there can be memory bandwidth benefits. If aligned samples are used for DC intra-frame mode prediction, the circuit used to perform DC intra-frame mode prediction does not need to utilize non-adjacent rows or columns to extract samples to the upper left of the current block for DC intra-frame mode prediction. Since the extraction is performed in chunks, not accessing the upper left sample may be beneficial in reducing the amount of data read. Therefore, in some examples, there can be computational efficiency because the video decoder accesses fewer samples from the memory for DC intra-frame mode prediction. In this way, the example technology described in the present disclosure provides a technical solution to a technical problem that improves the operation of a video decoder and a video decoding process, and has practical application for applying DC intra-frame prediction on a current block.

[0011] In one example, the present disclosure describes a method for decoding video data, the method comprising: determining samples to be used for DC intra-frame mode prediction for a current block, wherein determining the samples comprises determining multiple samples of at least one of the following: a non-adjacent sample row having a last sample in the same column as a last column of the current block, wherein the non-adjacent sample row is more than one row above the current block, or a non-adjacent sample column having a last sample in the same row as the last row of the current block, wherein the non-adjacent sample column is more than one column to the left of the current block; and using the determined samples, decoding the current block using DC intra-frame mode prediction.

[0012] In one example, the present disclosure describes a method for encoding video data, the method comprising: determining samples to be used for DC intra-frame mode prediction for a current block, wherein determining the samples comprises determining multiple samples of at least one of the following: a non-adjacent sample row having a last sample in the same column as a last column of the current block, wherein the non-adjacent sample row is more than one row above the current block, or a non-adjacent sample column having a last sample in the same row as the last row of the current block, wherein the non-adjacent sample column is more than one column to the left of the current block; and encoding the current block using DC intra-frame mode prediction using the determined samples.

[0013] In one example, the present disclosure describes a device for decoding video data, the device comprising: a memory configured to store one or more samples of rows and columns that are non-adjacent to a current block; and a processing circuit configured to: determine samples to be used for DC intra-frame mode prediction for the current block, wherein, to determine the samples, the processing circuit is configured to determine multiple samples of at least one of the following: a non-adjacent sample row having a last sample in the same column as a last column of the current block, wherein the non-adjacent sample row is more than one row above the current block, or a non-adjacent sample column having a last sample in the same row as the last row of the current block, wherein the non-adjacent sample column is more than one column to the left of the current block; and use the determined samples to decode the current block using DC intra-frame mode prediction.

[0014] In one example, the present disclosure describes a device for encoding video data, the device comprising: a memory configured to store one or more samples of rows and columns that are non-adjacent to a current block; and a processing circuit configured to: determine samples to be used for DC intra-frame mode prediction for the current block, wherein, to determine the samples, the processing circuit is configured to determine multiple samples of at least one of the following: a non-adjacent sample row having a last sample in the same column as a last column of the current block, wherein the non-adjacent sample row is more than one row above the current block, or a non-adjacent sample column having a last sample in the same row as the last row of the current block, wherein the non-adjacent sample column is more than one column to the left of the current block; and using the determined samples, encode the current block using DC intra-frame mode prediction.

[0015] In one example, the present disclosure describes a computer-readable storage medium having instructions stored thereon that, when executed, cause one or more processors to perform the following operations: determine samples to be used for DC intra-frame mode prediction for a current block, wherein the instructions causing the one or more processors to determine the samples include instructions causing the one or more processors to determine multiple samples of at least one of the following: a non-adjacent sample row having a last sample in the same column as a last column of the current block, wherein the non-adjacent sample row is more than one row above the current block, or a non-adjacent sample column having a last sample in the same row as the last row of the current block, wherein the non-adjacent sample column is more than one column to the left of the current block; and using the determined samples, decode the current block using DC intra-frame mode prediction.

[0016] In one example, the present disclosure describes a device for decoding video data, the device comprising: a unit for determining samples to be used for DC intra-frame mode prediction for a current block, wherein the unit for determining the samples comprises a unit for determining multiple samples of at least one of the following: a non-adjacent sample row having a last sample in the same column as a last column of the current block, wherein the non-adjacent sample row is more than one row above the current block, or a non-adjacent sample column having a last sample in the same row as the last row of the current block, wherein the non-adjacent sample column is more than one column to the left of the current block; and a unit for decoding the current block using DC intra-frame mode prediction using the determined samples.

[0017] The details of one or more examples are set forth in the accompanying drawings and the description below. Other features, objects, and advantages will be apparent from the description, drawings, and claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is a block diagram illustrating an example video encoding and decoding system that may perform the techniques of this disclosure.

[0019] Figure 2A and Figure 2B is a conceptual diagram illustrating an example quadtree binary tree (QTBT) structure and a corresponding coding tree unit (CTU).

[0020] Figure 3 is a block diagram illustrating an example video encoder that may perform the techniques of this disclosure.

[0021] Figure 4 is a block diagram illustrating an example video decoder that may perform the techniques of this disclosure.

[0022] Figure 5 is a conceptual diagram showing the direction of intra prediction, where arrows point to reference samples.

[0023] Figure 6 is a conceptual diagram illustrating an example of an intra-predicted 8x4 rectangular block.

[0024] Fig. 7A -7C is a conceptual diagram showing a mode mapping process for modes outside the diagonal direction range.

[0025] Figure 8 is a conceptual diagram showing wide angles (-1 to -10 and 67 to 76) in addition to the 65 angle mode.

[0026] Fig. 9is a conceptual diagram showing wide angles (-1 to -14 and 67 to 80) beyond modes 2 and 6 (93 angle modes in total).

[0027] Fig.10 is a mapping table used to determine the angles used for intra prediction.

[0028] Fig.11 is a conceptual diagram illustrating reference samples from multiple reference lines that can be used for intra prediction of a coding block.

[0029] Fig.12 is a conceptual diagram showing reference samples from directly adjacent rows and columns.

[0030] Fig.13 –15 is a conceptual diagram showing reference samples from non-adjacent rows and columns that are not aligned with the current block.

[0031] Fig.16 –19 is a conceptual diagram showing reference samples from non-adjacent rows and columns aligned with the current block.

[0032] Fig. 20 is a flow chart illustrating an example method of encoding video data.

[0033] Fig.21 is a flow chart illustrating an example method of decoding video data. DETAILED DESCRIPTION

[0034] In video decoding, a video encoder generates a prediction block for a current block and determines a residual block (e.g., difference) between the current block and the prediction block. The video encoder signals information indicating the residual block and prediction mode information indicating how the video encoder generates the prediction block. The video decoder receives the information of the residual block and the prediction mode information. The video decoder generates a prediction block based on the prediction mode information so that the prediction block generated by the video decoder is the same as the prediction block generated by the video encoder. The video decoder adds the prediction block to the residual block to reconstruct the current block.

[0035] An example of a prediction mode is a DC intra prediction mode. In the DC intra prediction mode, a video decoder (e.g., a video encoder and / or a video decoder) generates a prediction block using samples in the same picture as the current block. For example, for the DC intra prediction mode, the video decoder may generate a prediction block using samples in an adjacent row (e.g., a row directly above) and / or an adjacent column (e.g., a column directly to the left) of the current block.

[0036] In some examples, the DC intra prediction mode utilizes samples from non-adjacent columns or rows. As one example, the non-adjacent sample row is more than one row above the current block, and the non-adjacent sample column is more than one column to the left of the current block. As another example, the non-adjacent sample row is more than three rows above the current block, and the non-adjacent sample column is more than three columns to the left of the current block. As another example, the non-adjacent sample row is more than two rows above the current block, and the non-adjacent sample column is more than two columns to the left of the current block.

[0037] The video encoder may signal the video decoder received information indicating which row and / or column is used for DC intra prediction. For example, the information may indicate whether samples in rows and / or columns adjacent to the current block are to be used for DC intra prediction, whether samples in rows and / or columns (e.g., one example of non-adjacent rows or columns) are to be used for DC intra prediction, or whether samples in rows and / or columns (e.g., another example of non-adjacent rows or columns) are to be used for DC intra prediction. In another case, the information may indicate whether samples in rows and / or columns adjacent to the current block are to be used for DC intra prediction, whether samples in rows and / or columns (e.g., one example of non-adjacent rows or columns) are to be used for DC intra prediction, or whether samples in rows and / or columns (e.g., another example of non-adjacent rows or columns) are to be used for DC intra prediction.

[0038] The present disclosure describes example techniques for determining which samples in non-adjacent rows and / or columns should be used to generate a prediction block. The samples in the non-adjacent rows and / or columns may be aligned with the current block. For example, the last sample (e.g., the rightmost sample) of the samples in the non-adjacent rows that may be used for DC intra prediction may be aligned with the last column (e.g., the rightmost column) of the current block. The last sample (e.g., the bottommost sample) of the samples in the non-adjacent columns that may be used for DC intra prediction may be aligned with the last row (e.g., the bottommost row) of the current block. In some examples, the first sample (e.g., the leftmost sample) of the samples in the non-adjacent rows that may be used for DC intra prediction may be aligned with the first column (e.g., the leftmost column) of the current block, and the first sample (e.g., the topmost sample) of the samples in the non-adjacent columns that may be used for DC intra prediction may be aligned with the first row (e.g., the topmost row) of the current block.

[0039] In one or more examples, using samples from non-adjacent rows or columns that are aligned with the current block can produce a better predicted block (e.g., in terms of having a smaller residual value in the residual block) than using samples from non-adjacent rows or columns that are not aligned with the current block. In addition, in some examples, the circuitry of a video decoder for DC intra-frame prediction may not need to access samples located at the top and left of the current block, which reduces the amount of data read. In this way, the example techniques can improve the overall operation of the video decoder and improve the video decoding process. For example, the example techniques provide practical applications for improving the operation of a video encoder and a video decoder when performing DC intra-frame prediction of a current block.

[0040] Figure 1 1 is a block diagram illustrating an example video encoding and decoding system 100 that can perform the techniques of the present disclosure. In general, the techniques of the present disclosure relate to decoding (encoding and / or decoding) video data. Generally, video data includes any data used to process video. Thus, video data can include original unencoded video, encoded video, decoded (e.g., reconstructed) video, and video metadata (e.g., signaling data).

[0041] like Figure 1 As shown, in this example, system 100 includes a source device 102 that provides encoded video data to be decoded and displayed by a destination device 116. Specifically, source device 102 provides the video data to destination device 116 via computer-readable medium 110. Source device 102 and destination device 116 may include any of a wide variety of devices, including desktop computers, notebook computers (i.e., laptop computers), tablet computers, set-top boxes, telephone handsets such as smart phones, televisions, cameras, display devices, digital media players, video game consoles, video streaming devices, etc. In some cases, source device 102 and destination device 116 may be equipped for wireless communication and, therefore, may be referred to as wireless communication devices.

[0042] exist Figure 1In the example of , 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 can be configured to apply a technique for determining which samples to use for DC intra-frame mode prediction (e.g., where the samples are located in non-adjacent rows or columns and are aligned with the current block being decoded (e.g., encoded or decoded)). Therefore, the source device 102 represents an example of a video encoding device, and 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 arrangements. 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 be docked with an external display device instead of including an integrated display device.

[0043] like Figure 1 The system 100 shown is only one example. In general, any digital video encoding and / or decoding device can perform techniques for determining which samples to use for DC intra-mode prediction (e.g., where the samples are located in non-adjacent rows or columns and are aligned with a current block being decoded (e.g., encoded or decoded)). The source device 102 and the destination device 116 are only examples of such decoding devices, where the source device 102 generates decoded video data for transmission to the destination device 116. The present disclosure refers to a "decoding" device as a device that performs decoding (e.g., encoding and / or decoding) of data. Therefore, the video encoder 200 and the video decoder 300 represent examples of decoding devices (specifically, a video encoder and a video decoder, respectively). In some examples, the devices 102 and 116 can operate in a substantially symmetrical manner, such that each of the devices 102, 116 includes video encoding and decoding components. Thus, system 100 may support one-way or two-way video transmission between video devices 102, 116, for example, for video streaming, video playback, video broadcasting, or video telephony.

[0044] Typically, the video source 104 represents the source of video data (i.e., the original, unencoded video data), and provides a series of pictures (also referred to as "frames") of the order of the video data to the video encoder 200, which encodes the data for the pictures. The video source 104 of the source device 102 may include a video capture device, such as a camera, a video archive unit containing previously captured original video, and / or a video feed interface for receiving video from a video content provider. As another alternative, the video source 104 may generate computer graphics-based data as the source video, or a combination of real-time video, archived video, and computer-generated video. In each case, the video encoder 200 may encode captured, pre-captured, or computer-generated video data. The video encoder 200 may rearrange the pictures from the received order (sometimes referred to as "display order") to a decoding order for decoding. The video encoder 200 may generate a bitstream comprising encoded video data. Source device 102 may then output the encoded video data onto computer-readable medium 110 via output interface 108 to be received and / or retrieved by, for example, input interface 122 of destination device 116 .

[0045] The memory 106 of the source device 102 and the memory 120 of the destination device 116 represent general purpose memories. In some examples, the memories 106, 120 can store original video data, for example, original video from the video source 104 and original decoded video data from the video decoder 300. In addition or alternatively, the memories 106, 120 can store software instructions that can be executed by, for example, the video encoder 200 and the video decoder 300, respectively. Although shown as separate 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 can also include internal memories for functionally similar or equivalent purposes. In addition, the memories 106, 120 can store, for example, 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 can be allocated as one or more video buffers, for example, to store original decoded and / or encoded video data.

[0046] The computer-readable medium 110 may represent any type of medium or device capable of delivering the encoded video data from the source device 102 to the destination device 116. In one example, the computer-readable medium 110 represents a communication medium that enables the source device 102 to directly send 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 according to a communication standard such as a wireless communication protocol, 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, for example, a radio frequency (RF) spectrum or one or more physical transmission lines. The communication medium may form a portion 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.

[0047] In some examples, source device 102 may output the encoded data from output interface 108 to storage device 112. Similarly, destination device 116 may access the encoded data from storage device 112 via input interface 122. Storage device 112 may include any of a variety of distributed or locally accessed data storage media, such as a hard drive, Blu-ray disc, DVD, CD-ROM, flash memory, volatile or non-volatile memory, or any other suitable digital storage medium for storing encoded video data.

[0048] In some examples, source device 102 may output the encoded video data to file server 114 or another intermediate storage device that may store the encoded video data generated by source device 102. Destination device 116 may access the stored video data from file server 114 via streaming or downloading.

[0049] The file server 114 may be any type of server device capable of storing encoded video data and sending the encoded video data to the destination device 116. The file server 114 may 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 an enhanced MBMS (eMBMS) server, and / or a network attached storage (NAS) device. The file server 114 may additionally or alternatively implement one or more HTTP streaming protocols, such as Dynamic Adaptive Streaming over HTTP (DASH), HTTP Real-time Streaming (HLS), Real-time Streaming Protocol (RTSP), HTTP Dynamic Streaming, etc.

[0050] The destination device 116 may access the encoded video data from the file server 114 through any standard data connection, including an Internet connection. This may include a wireless channel (e.g., a Wi-Fi connection), a wired connection (e.g., a digital subscriber line (DSL), a 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 may be configured to operate according to any one or more of the various protocols discussed above for retrieving or receiving media data from the file server 114, or other such protocols for retrieving media data.

[0051] Output interface 108 and input interface 122 may represent wireless transmitters / receivers, modems, wired networking components (e.g., Ethernet cards), wireless communication components that operate according to any of the 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 transmit data (such as encoded video data) according to a cellular communication standard (such as 4G, 4G-LTE (Long Term Evolution), Advanced LTE, 5G, etc.). In some examples where output interface 108 includes a wireless transmitter, output interface 108 and input interface 122 may be configured to transmit data (such as encoded video data) according to other wireless standards (such as IEEE 802.11 specifications, IEEE 802.15 specifications (e.g., ZigBee TM ), Bluetooth TMStandards, etc.) to transmit data (such as encoded video data). In some examples, source device 102 and / or destination device 116 may include corresponding system-on-chip (SoC) devices. For example, source device 102 may include a SoC device for performing the functions assigned to video encoder 200 and / or output interface 108, and destination device 116 may include a SoC device for performing the functions assigned to video decoder 300 and / or input interface 122.

[0052] The techniques of the present disclosure may be applied to video decoding to support any of a variety of multimedia applications, such as over-the-air television broadcasting, cable television transmission, satellite television transmission, Internet streaming video transmission (such as Dynamic Adaptive Streaming over HTTP (DASH)), digital video encoded onto a data storage medium, decoding of digital video stored on a data storage medium, or other applications.

[0053] The input interface 122 of the destination device 116 receives the encoded video bitstream from the computer-readable medium 110 (e.g., the storage device 112, the file server 114, etc.). The encoded video bitstream may include signaling information such as the following syntax elements defined by the video encoder 200 (which are also used by the video decoder 300): the syntax elements have values ​​that describe the characteristics and / or processing of video blocks or other decoding units (e.g., slices, pictures, groups of pictures, sequences, etc.). The display device 118 displays the decoded pictures of the decoded video data to the user. The display device 118 can represent any of a variety of display devices, such as a cathode ray tube (CRT), a liquid crystal display (LCD), a plasma display, an organic light emitting diode (OLED) display, or another type of display device.

[0054] Despite Figure 1 2. Although not shown in the drawings, 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 appropriate MUX-DEMUX units or other hardware and / or software to process multiplexed streams including both audio and video in a common data stream. If applicable, the MUX-DEMUX units may follow the ITU H.223 multiplexer protocol or other protocols such as the User Datagram Protocol (UDP).

[0055] The video encoder 200 and the video decoder 300 can 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 technology is partially implemented in software, the device can store instructions for the software in a suitable non-transitory computer-readable medium, and use one or more processors to execute the instructions in hardware to perform the technology of the present disclosure. Each of the video encoder 200 and the video decoder 300 can be included in one or more encoders or decoders, and any of the encoders or decoders can be integrated as part of a combined encoder / decoder (CODEC) in the corresponding device. The device including the video encoder 200 and / or the video decoder 300 can include an integrated circuit, a microprocessor, and / or a wireless communication device (such as a cellular phone).

[0056] Some example video coding standards are described below. Video coding standards include ITU-T H.261, ISO / IEC MPEG-1 Visual, ITU-T H.262 or ISO / IEC MPEG-2 Visual, ITU-T H.263, ISO / IEC MPEG-4 Visual, and ITU-T H.264 (also known as ISO / IEC MPEG-4 AVC), including its scalable video coding (SVC) and multi-view video coding (MVC) extensions.

[0057] The Joint Collaborative Team on Video Coding (JCT-VC) of the ITU-T Video Coding Experts Group (VCEG) and the ISO / IEC Motion Experts Group (MPEG) finalized the state-of-the-art video coding standard, High Efficiency Video Coding (HEVC), in April 2013. The Joint Video Experts Group (JVET), a collaborative group consisting of MPEG and VCEG of ITU-T Study Group 16, is working on a new video coding standard, called Versatile Video Coding (VVC). The main goal of VVC is to provide significant improvements in compression performance compared to the existing HEVC standard, thereby facilitating the deployment of higher quality video services and emerging applications, such as 360° immersive multimedia and high dynamic range (HDR) video. The development of the VVC standard is expected to be completed in 2020. The latest draft of the VVC standard is described in the following document and is available at http: / / phenix.it-sudparis.eu / jvet / doc_end_user / documents / 13_Marrakech / wg11 / J VET-N1001-v8.zip: Bross et al., "Versatile Video Coding (Draft 5)", Joint Video Experts Group (JVET) of ITU-T SG 16 WP 3 and ISO / IEC JTC 1 / SC 29 / WG 11, 14th Meeting: Geneva, Switzerland, March 19-27, 2019, JVET-N1001-v8 (hereinafter referred to as "VVC Draft 5").

[0058] The video encoder 200 and the video decoder 300 may operate in accordance with a video coding standard, such as the ITU-T H.265 standard, also known as the High Efficiency Video Coding (HEVC) standard, or extensions thereof, such as multi-view and / or scalable video coding extensions. Alternatively, the video encoder 200 and the video decoder 300 may operate in accordance with other proprietary or industry standards, such as the ITU-T H.266 standard, also known as Versatile Video Coding (VVC). The latest draft of the VVC standard is described in the following document: Bross et al., “Versatile Video Coding (Draft 9)”, Joint Video Experts Group (JVET) of ITU-T SG 16WP 3 and ISO / IEC JTC 1 / SC 29 / WG 11, 18th Meeting: by Teleconference, April 15-24, 2020, JVET-R2001-v8 (hereinafter referred to as “VVC Draft 9”). However, the techniques of the present disclosure are not limited to any particular coding standard.

[0059] Typically, the video encoder 200 and the video decoder 300 can perform block-based decoding of the picture. The term "block" generally refers to a structure that includes data to be processed (e.g., to be encoded, decoded, or otherwise used in the encoding and / or decoding process). For example, a block may include a two-dimensional matrix of samples of luminance and / or chrominance data. Typically, the video encoder 200 and the video decoder 300 can decode video data represented in a YUV (e.g., Y, Cb, Cr) format. That is, instead of decoding red, green, and blue (RGB) data for samples of a picture, the video encoder 200 and the video decoder 300 can decode luminance and chrominance components, wherein the chrominance components may include both red hue and blue hue chrominance components. In some examples, the video encoder 200 converts the received RGB formatted data to a YUV representation before encoding, and the 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.

[0060] In general, the present disclosure may relate to the decoding (e.g., encoding and decoding) of a picture to include the process of encoding or decoding data for the picture. Similarly, the present disclosure may relate to the decoding of a block of a picture to include the process of encoding or decoding data for the block (e.g., prediction and / or residual decoding). The encoded video bitstream typically includes a series of values ​​for syntax elements that represent decoding decisions (e.g., decoding modes) and partitioning of the picture into blocks. Therefore, references to decoding a picture or a block should generally be understood as decoding the values ​​of the syntax elements used to form the picture or the block.

[0061] HEVC defines various blocks, including coding units (CUs), prediction units (PUs), and transform units (TUs). According to HEVC, a video decoder (such as the video encoder 200) partitions a coding tree unit (CTU) into CUs according to a quadtree structure. That is, the video decoder partitions the CTU and CU into four equal, non-overlapping squares, and each node of the quadtree has zero or four child nodes. A node without child nodes may be referred to as 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 decoder may further partition the PU and TU. For example, in HEVC, a residual quadtree (RQT) represents the partitioning of a TU. In HEVC, a PU represents inter-frame prediction data, and a TU represents residual data. An intra-predicted CU includes intra-frame prediction information, such as an intra-frame mode indication.

[0062] As another example, the video encoder 200 and the video decoder 300 may be configured to operate according to VVC. According to VVC, a video decoder (such as the video encoder 200) partitions a picture into a plurality of coding tree units (CTUs). The video encoder 200 may partition the CTUs according to a tree structure (such as a quadtree binary tree (QTBT) structure or a multi-type tree (MTT) structure). The QTBT structure removes the concept of multiple partition types, such as the distinction between CU, PU, ​​and TU in HEVC. The QTBT structure includes two levels: a first level partitioned according to quadtree partitioning, and a second level partitioned according to binary tree partitioning. The root node of the QTBT structure corresponds to the CTU. The leaf nodes of the binary tree correspond to coding units (CUs).

[0063] In the MTT segmentation structure, blocks can be segmented using quadtree (QT) segmentation, binary tree (BT) segmentation, and one or more types of ternary tree (TT) segmentation. A ternary tree segmentation is a segmentation in which a block is split into three sub-blocks. In some examples, the ternary tree segmentation divides the block into three sub-blocks without dividing the original block through the center. The segmentation types in MTT (e.g., QT, BT, and TT) can be symmetric or asymmetric.

[0064] In some examples, the video encoder 200 and the video decoder 300 may use a single QTBT or MTT structure to represent each of the luma component and the chroma components, while in other examples, the video encoder 200 and the video decoder 300 may use two or more QTBT or MTT structures, such as one QTBT / MTT structure for the luma component and another QTBT / MTT structure for the two chroma components (or two QTBT / MTT structures for the respective chroma components).

[0065] The video encoder 200 and the video decoder 300 may be configured to use quadtree segmentation, QTBT segmentation, MTT segmentation, or other segmentation structures according to HEVC. For the purpose of explanation, the description of the technology of the present disclosure is introduced with respect to QTBT segmentation. However, it should be understood that the technology of the present disclosure may also be applied to a video decoder configured to use quadtree segmentation or also use other types of segmentation.

[0066] This disclosure may use "NxN" and "N by N" interchangeably to refer to the sample size of a block (such as a CU or other video block) in terms of vertical and horizontal dimensions, for example, 16x16 samples or 16 by 16 samples. Typically, a 16x16 CU will have 16 samples in the vertical direction (y=16) and will have 16 samples in the horizontal direction (x=16). Similarly, an NxNCU typically has N samples in the vertical direction and N samples in the horizontal direction, where N represents a non-negative integer value. The samples in a CU may be arranged in rows and columns. In addition, 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 NxM samples, where M is not necessarily equal to N.

[0067] The video encoder 200 encodes video data representing prediction and / or residual information and other information for a CU. The prediction information indicates how the CU will be predicted in order to form a prediction block for the CU. The residual information typically represents the sample-by-sample difference between the samples of the CU before encoding and the prediction block.

[0068] In order to predict a CU, the video encoder 200 can generally form a prediction block for the CU by inter-frame prediction or intra-frame prediction. Inter-frame prediction generally refers to predicting a CU based on data of a previously decoded picture, while intra-frame prediction generally refers to predicting a CU based on previously decoded data of the same picture. In order to perform inter-frame prediction, the video encoder 200 can use one or more motion vectors to generate a prediction block. The video encoder 200 can generally perform motion search to identify a reference block that closely matches the CU, for example, in terms of the difference between the CU and the reference block. The video encoder 200 can use the sum of absolute differences (SAD), the sum of squared differences (SSD), the mean absolute difference (MAD), the mean square difference (MSD), or other such difference calculations to calculate a difference metric to determine whether the reference block closely matches the current CU. In some examples, the video encoder 200 can use unidirectional prediction or bidirectional prediction to predict the current CU.

[0069] VVC also provides an affine motion compensation mode, which can be considered an inter-frame prediction mode. In the affine motion compensation mode, the video encoder 200 can determine two or more motion vectors representing non-translational motion (such as zooming in or out, rotation, perspective motion, or other irregular motion types).

[0070] In order to perform intra prediction, the video encoder 200 can select an intra prediction mode to generate a prediction block. VVC can provide sixty-seven intra prediction modes, including various directional modes, as well as plane modes and DC modes. Typically, the video encoder 200 selects an intra prediction mode that describes the neighboring samples of the current block according to which the samples of the current block (e.g., the block of the CU) are predicted. Assuming that the video encoder 200 decodes the CTU and CU in a raster scan order (from left to right, from top to bottom), such samples can typically be above, above left, or to the left of the current block in the same picture as the current block.

[0071] The video encoder 200 encodes data representing a prediction mode for the current block. For example, for an inter-frame prediction mode, the video encoder 200 may encode data representing which inter-frame prediction mode of various available inter-frame prediction modes is used and motion information for the corresponding mode. For unidirectional or bidirectional inter-frame prediction, for example, the video encoder 200 may encode motion vectors using advanced motion vector prediction (AMVP) or merge mode. The video encoder 200 may use a similar mode to encode motion vectors for affine motion compensation mode.

[0072] After a prediction such as intra prediction or inter prediction of a block, the video encoder 200 may calculate residual data for the block. The residual data (such as a residual block) represents the sample-by-sample difference between the block and a prediction block for the block, which is formed using a corresponding prediction mode. The video encoder 200 may apply one or more transforms to the residual block to produce transformed data in a transform domain rather than in a sample domain. For example, the 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. In addition, the video encoder 200 may apply a secondary transform after the first transform, such as a mode-dependent non-separable secondary transform (MDNSST), a signal-dependent transform, a Karhunen-Loeve transform (KLT), etc. The video encoder 200 generates transform coefficients after applying one or more transforms.

[0073] As described above, after any transformation to produce transform coefficients, the video encoder 200 may perform quantization of the transform coefficients. Quantization generally refers to a process in which transform coefficients are quantized to potentially reduce the amount of data used to represent the coefficients, thereby providing further compression. By performing the quantization process, the video encoder 200 may reduce the bit depth associated with some or all coefficients. For example, the video encoder 200 may round down an n-bit value to an m-bit value during quantization, where n is greater than m. In some examples, to perform quantization, the video encoder 200 may perform a bitwise right shift of the value to be quantized.

[0074] After quantization, the video encoder 200 can scan the transform coefficients to generate a one-dimensional vector from a two-dimensional matrix including the quantized transform coefficients. The scan can be designed to place coefficients of higher energy (and therefore lower frequency) in front of the vector and transform coefficients of lower energy (and therefore higher frequency) in the back of the vector. In some examples, the video encoder 200 can scan the quantized transform coefficients using a predefined scan order to generate a serialized vector, and then entropy encode the quantized transform coefficients of the vector. In other examples, the video encoder 200 can perform adaptive scanning. After scanning the quantized transform coefficients to form a one-dimensional vector, the video encoder 200 can entropy encode the one-dimensional vector, for example, according to context adaptive binary arithmetic coding (CABAC). The video encoder 200 can also entropy encode the values ​​of the syntax elements used to describe the metadata associated with the encoded video data for use by the video decoder 300 when decoding the video data.

[0075] To perform CABAC, the video encoder 200 may assign context within a context model to a symbol to be transmitted. The context may relate to, for example, whether neighboring values ​​of the symbol are zero values. The probability determination may be based on the context assigned to the symbol.

[0076] The video encoder 200 may also 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, in a picture header, a block header, a slice header, or other syntax data (such as a sequence parameter set (SPS), a picture parameter set (PPS), or a video parameter set (VPS). Likewise, the video decoder 300 may decode such syntax data to determine how to decode the corresponding video data.

[0077] In this way, the video encoder 200 can generate a bitstream that includes encoded video data, such as syntax elements describing the partitioning of a picture into blocks (e.g., CUs) and prediction and / or residual information for these blocks. Finally, the video decoder 300 can receive the bitstream and decode the encoded video data.

[0078] In general, the video decoder 300 performs a process that is the reverse of the process performed by the video encoder 200 to decode the encoded video data of the bitstream. For example, the video decoder 300 may use CABAC to decode the values ​​of the syntax elements for the bitstream in a manner substantially similar to, but reverse to, the CABAC encoding process of the video encoder 200. The syntax elements may define partitioning information for partitioning a picture into CTUs, and partitioning each CTU according to a corresponding partitioning structure (such as a QTBT structure) to define CUs of the CTUs. The syntax elements may also define prediction and residual information for a block (e.g., CU) of video data.

[0079] The residual information may be represented by, for example, quantized transform coefficients. The video decoder 300 may inverse quantize and inverse transform the quantized transform coefficients of the block to reproduce a residual block for the block. The video decoder 300 uses the signaled prediction mode (intra-frame prediction or inter-frame prediction) and related prediction information (e.g., motion information for inter-frame prediction) to form a prediction block for the block. The video decoder 300 may then combine the prediction block and the residual block (on a sample-by-sample basis) to reproduce the original block. The video decoder 300 may perform additional processing, such as performing a deblocking process to reduce visual artifacts along the boundaries of the blocks.

[0080] As described in more detail below, the example techniques described in the present disclosure relate to intra-frame prediction, such as DC intra-frame mode prediction. In one or more examples, a video decoder (e.g., video encoder 200 or video decoder 300) may be configured to determine samples to be used for DC intra-frame mode prediction for a current block. For example, to determine the samples, the video decoder may be configured to determine a plurality of samples in a non-adjacent row or non-adjacent column, which has a last sample in the same column as the last column of the current block in the non-adjacent row or has a last sample in the same row as the last row of the current block in the non-adjacent column. In some examples, a plurality of samples in a non-adjacent row or non-adjacent column may have a first sample in the same column as the first column of the current block in the non-adjacent row, or have a first sample in the same row as the first row of the current block in the non-adjacent column. In this way, samples for DC intra-frame mode prediction are aligned with the current block, even if the samples are in non-adjacent rows or columns. The video coder may code (eg, encode or decode) the current block using the determined samples using DC intra-mode prediction.

[0081] In general, the present disclosure may involve "signaling" certain information (such as syntax elements). The term "signaling" may generally refer to the transmission 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 in a bitstream. Generally, signaling refers to generating values ​​in a bitstream. As described above, source device 102 may transmit the bitstream to destination device 116 in substantially real time or not in real time (such as may occur when storing syntax elements to storage device 112 for later retrieval by destination device 116).

[0082] Figure 2A and 2B1 is a conceptual diagram showing an example quadtree binary tree (QTBT) structure 130 and a corresponding coding tree unit (CTU) 132. Solid lines represent quadtree splits, while dashed lines indicate binary tree splits. In each split (i.e., non-leaf) node of the binary tree, a flag is signaled to indicate which split type (i.e., horizontal or vertical) is used, where, in this example, 0 indicates horizontal splitting and 1 indicates vertical splitting. For quadtree splitting, since the quadtree node splits the block horizontally and vertically into 4 sub-blocks of equal size, there is no need to indicate the split type. Therefore, the video encoder 200 can encode the following, and the video decoder 300 can decode the following: syntax elements (such as split information) for the regional tree level (i.e., solid line) of the QTBT structure 130, and syntax elements (such as split information) for the prediction tree level (i.e., dashed line) of the QTBT structure 130. The video encoder 200 may encode video data (such as prediction and transform data) for a CU represented by a terminal leaf node of the QTBT structure 130 , and the video decoder 300 may decode the video data.

[0083] generally, Figure 2B The CTU 132 may be associated with parameters defining the size of blocks corresponding to nodes at the first and second levels of the QTBT structure 130. These parameters may include a CTU size (indicating the size of the CTU 132 in samples), a minimum quadtree size (MinQTSize, which indicates the minimum allowed quadtree leaf node size), a maximum binary tree size (MaxBTSize, which indicates the maximum allowed binary tree root node size), a maximum binary tree depth (MaxBTDepth, which indicates the maximum allowed binary tree depth), and a minimum binary tree size (MinBTSize, which indicates the minimum allowed binary tree leaf node size).

[0084] The root node of the QTBT structure corresponding to the CTU may have four child nodes at the first level of the QTBT structure, each of which may be segmented according to a quadtree segmentation. That is, the node of the first level is a leaf node (without child nodes) or has four child nodes. The example of the QTBT structure 130 represents such a node as including a parent node and a child node with a solid line branch. If the node of the first level is not larger than the maximum allowed binary tree root node size (MaxBTSize), the nodes may be further segmented by the corresponding binary tree. The binary tree splitting of a node may be iterated until the node generated from the split reaches the minimum allowed binary tree leaf node size (MinBTSize) or the maximum allowed binary tree depth (MaxBTDepth). The example of the QTBT structure 130 represents such a node as having a dotted line branch. The binary tree leaf node is called a coding unit (CU), which is used for prediction (e.g., intra-picture or inter-picture prediction) and transformation without any further segmentation. As discussed above, a CU may also be referred to as a "video block" or "block".

[0085] In one example of a QTBT partitioning structure, the CTU size is set to 128x128 (luminance sample and two corresponding 64x64 chrominance samples), MinQTSize is set to 16x16, MaxBTSize is set to 64x64, MinBTSize (for both width and height) is set to 4, and MaxBTDepth is set to 4. Quadtree partitioning is first applied to the CTU to generate a quadtree leaf node. The quadtree leaf node can have a size from 16x16 (i.e., MinQTSize) to 128x128 (i.e., CTU size). If the leaf quadtree node is 128x128, the leaf quadtree node will not be further split by the binary tree because the size exceeds MaxBTSize (i.e., 64x64 in this example). Otherwise, the leaf quadtree node will be further split by the binary tree. Therefore, the quadtree leaf node is also the root node for the binary tree and has a binary tree depth of 0. When the binary tree depth reaches MaxBTDepth (4 in this example), no further splitting is allowed. When a binary tree node has a width equal to MinBTSize (4 in this example), it means that no further horizontal splitting is allowed. Similarly, a binary tree node with a height equal to MinBTSize means that no further vertical splitting is allowed for the binary tree node. As described above, the leaf nodes of the binary tree are called CUs and are further processed according to prediction and transformation without further segmentation.

[0086] Figure 3 is a block diagram illustrating an example video encoder 200 that may perform the techniques of this disclosure. Figure 3The present disclosure generally illustrates the video encoder 200 in the context of video coding standards such as the HEVC video coding standard and the developing H.266 video coding standard. However, the techniques of the present disclosure are not limited to these video coding standards and are generally applicable to video encoding and decoding.

[0087] exist Figure 3 In the example of , 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 coding unit 220. Any one 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 coding unit 220 may be implemented in one or more processors or in processing circuits. In addition, the video encoder 200 may include additional or alternative processors or processing circuits to perform these and other functions.

[0088] The video data memory 230 may store video data to be encoded by the components of the video encoder 200. The video encoder 200 may receive video data from, for example, the video source 104 ( Figure 1 ) receives the video data stored in the video data memory 230. DPB 218 can act as a reference picture memory, which stores reference video data for use when subsequent video data is predicted by the video encoder 200. Video data memory 230 and DPB 218 can be formed by any of a variety of memory devices, such as dynamic random access memory (DRAM) (including synchronous DRAM (SDRAM)), magnetoresistive RAM (MRAM), resistive RAM (RRAM), or other types of memory devices. Video data memory 230 and DPB 218 can be provided by the same memory device or a separate memory device. In various examples, video data memory 230 can be on chip with other components of the video encoder 200 (as shown), or off chip relative to those components.

[0089] In the present disclosure, references to the video data memory 230 should not be interpreted as limited to memory internal to the video encoder 200 (unless specifically described as such), or to memory external to the video encoder 200 (unless specifically described as such). Rather, references 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 a current block to be encoded). Figure 1 The memory 106 may also provide temporary storage for outputs from the various units of the video encoder 200 .

[0090] Shows Figure 3 The various units of the video encoder 200 are provided to help understand the operations performed by the video encoder 200. These units may be implemented as fixed-function circuits, programmable circuits, or a combination thereof. Fixed-function circuits refer to circuits that provide specific functions and are pre-set with respect to the operations that can be performed. Programmable circuits refer to circuits that can be programmed to perform various tasks and provide flexible functions with the operations that can be performed. For example, a programmable circuit may execute software or firmware that causes the programmable circuit to operate in a manner defined by the instructions of the software or firmware. Fixed-function circuits may execute software instructions (e.g., to receive parameters or output parameters), but the types of operations performed by fixed-function circuits are generally immutable. In some examples, one or more of these units may be different circuit blocks (fixed-function or programmable), and in some examples, one or more units may be integrated circuits.

[0091] The video encoder 200 may include an arithmetic logic unit (ALU), an elementary function unit (EFU), a digital circuit, an analog circuit, and / or a programmable core formed by a programmable circuit. In an example in which the operation of the video encoder 200 is performed using software executed by a programmable circuit, the memory 106 ( Figure 1 ) may store object code for software received and executed by the video encoder 200, or another memory (not shown) within the video encoder 200 may store such instructions.

[0092] The video data memory 230 is configured to store the received video data. The video encoder 200 may retrieve the 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 the original video data to be encoded.

[0093] 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. As an 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, etc.

[0094] The mode selection unit 202 generally coordinates multiple encoding passes to test combinations of encoding parameters and the resulting rate-distortion values ​​for such combinations. The encoding parameters may include partitioning of a CTU into CUs, a prediction mode for a CU, a transform type for residual data of a CU, a quantization parameter for residual data of a CU, etc. The mode selection unit 202 may ultimately select a combination of encoding parameters that has a better rate-distortion value than other tested combinations.

[0095] The video encoder 200 may partition the picture retrieved from the video data memory 230 into a series of CTUs, and encapsulate one or more CTUs in a slice. The mode selection unit 202 may partition the CTUs of the picture according to a tree structure (such as the QTBT structure or quadtree structure of HEVC described above). As described above, the video encoder 200 may form one or more CUs by partitioning the CTUs according to the tree structure. Such CUs may also be generally referred to as "video blocks" or "blocks".

[0096] Typically, the mode selection unit 202 also controls its components (e.g., the motion estimation unit 222, the motion compensation unit 224, and the intra prediction unit 226) to generate a prediction block for the current block (e.g., the current CU, or the overlapping portion of the PU and TU in HEVC). In order to inter-predict the current block, the motion estimation unit 222 may perform a motion search to identify one or more closely matching reference blocks in one or more reference pictures (e.g., one or more previously decoded pictures stored in the DPB 218). Specifically, the motion estimation unit 222 may calculate a value representing the degree of similarity of the potential reference block to the current block, for example, based on the sum of absolute differences (SAD), the sum of squared differences (SSD), the mean absolute difference (MAD), the mean squared difference (MSD), etc. The motion estimation unit 222 may typically perform these calculations using the sample-by-sample difference between the current block and the reference block under consideration. The motion estimation unit 222 may identify the reference block with the lowest value resulting from these calculations, which indicates the reference block that most closely matches the current block.

[0097] The motion estimation unit 222 may form one or more motion vectors (MVs) that define the position of the reference block in the reference picture relative to the position of the 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, for unidirectional inter prediction, the motion estimation unit 222 may provide a single motion vector, while for bidirectional 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 for the reference block. As another example, if the motion vectors have fractional sample precision, the motion compensation unit 224 may interpolate the values ​​for the prediction block according to one or more interpolation filters. In addition, for bidirectional inter prediction, the motion compensation unit 224 may retrieve data for two reference blocks identified by the corresponding motion vectors and combine the retrieved data, for example, by sample-by-sample averaging or weighted averaging.

[0098] As another example, for intra prediction or intra prediction decoding, the intra prediction unit 226 can generate a prediction block based on samples adjacent to the current block. For example, for a directional mode, the intra prediction unit 226 can generally mathematically combine the values ​​of adjacent samples and fill these calculated values ​​across the current block in a defined direction to produce a prediction block. As another example, for a DC intra mode prediction, the intra prediction unit 226 can calculate the average of adjacent samples of the current block and generate a prediction block to include the resulting average for each sample of the prediction block.

[0099] In one or more examples described in the present disclosure, the intra prediction unit 226, alone or in combination with one or more other components, can be configured to perform one or more of the example techniques described in the present disclosure. As an example, the mode selection unit 202 can be configured to determine that a current block of video data is to be predicted using DC intra mode prediction. In some examples of DC intra mode prediction, the samples used to generate the predicted block are samples in a directly adjacent row (e.g., a row immediately above the current block) or column (e.g., a column immediately to the left of the current block).

[0100] However, in some examples of DC intra mode prediction, samples may come from non-adjacent rows and / or non-adjacent columns. Non-adjacent rows refer to rows that may be above the current block in the same picture but not immediately above the current block. Non-adjacent columns refer to columns that may be to the left of the current block in the same picture but not immediately to the left of the current block. Figure 11-19 The example shown in describes an example of non-contiguous rows and columns.

[0101] As part of DC intra mode prediction, the mode selection unit 202 may generate information indicating which of the non-adjacent rows and / or non-adjacent columns include samples that may be used for DC intra mode prediction. For example, the video encoder 200 may signal a syntax element indicating the number of rows or columns that the non-adjacent sample row is above the current block or the number of rows or columns that the non-adjacent sample column is to the left of the current block.

[0102] In one or more examples, the intra prediction unit 226 can be configured to determine a plurality of samples to be used for DC intra mode prediction for the current block. For example, the intra prediction unit 226 can be configured to determine a plurality of samples in at least one of the non-adjacent sample rows having a last sample in the same column as the last column of the current block. The non-adjacent sample row is more than one row above the current block. The intra prediction unit 226 can be configured to determine a non-adjacent sample column having a last sample in the same row as the last row of the current block. The non-adjacent sample column is more than one column to the left of the current block. For example, as described with respect to Figure 16-19 Described in more detail, the last sample (e.g., the rightmost sample) from the plurality of samples in non-adjacent rows may be in the same column (e.g., have the same x-coordinate) as the last column (e.g., the rightmost column) of the current block, and the last sample (e.g., the bottommost sample) from the plurality of samples in non-adjacent columns may be in the same row (e.g., have the same y-coordinate) as the last row (e.g., the bottommost row) of the current block.

[0103] In some examples, such as Fig.16 and 17 Described in more detail, the first sample (e.g., the rightmost sample) from the plurality of samples in non-adjacent rows may be in the same column (e.g., have the same x-coordinate) as the first column (e.g., the leftmost column) of the current block. The first sample (e.g., the topmost sample) from the plurality of samples in non-adjacent columns may be in the same row (e.g., have the same y-coordinate) as the first row (e.g., the topmost row) of the current block.

[0104] In this way, the intra prediction unit 226 can determine samples from non-adjacent rows or columns that are aligned with the current block to be used for the DC intra prediction mode. Some other techniques contemplate using samples from non-adjacent rows or columns that are not aligned with the current block (e.g., the last sample or the first sample in the non-adjacent rows or columns is not in the same row or column as the last row or column or the first row or column of the current block). Using such samples from non-adjacent rows or columns that are not aligned with the current block may result in larger residuals than using samples from non-adjacent rows or columns that are aligned with the current block, and may also require additional memory accesses.

[0105] As described in more detail, the residual generation unit 204, together with the transform processing unit 206, the quantization unit 208, and the entropy coding unit 220, can perform intra-frame prediction encoding on the current block based on the determined samples from non-adjacent rows or columns. For example, the intra-frame prediction unit 226 can generate a prediction block using samples from non-adjacent rows and / or non-adjacent columns. The residual generation unit 204 can determine a residual block between the prediction block and the current block, which can be transformed, quantized, and entropy encoded by the transform processing unit 206, the quantization unit 208, and the entropy coding unit 220, respectively.

[0106] The mode selection unit 202 provides the prediction block to the residual generation unit 204. The residual generation unit 204 receives the original uncoded version of the current block from the video data memory 230 and receives 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 a residual block for the current block. In some examples, the residual generation unit 204 can determine the difference between the sample values ​​in the residual block to generate the residual block using residual differential pulse coding modulation (RDPCM). In some examples, the residual generation unit 204 can be formed using one or more subtractor circuits that perform binary subtraction.

[0107] In an example where the mode selection unit 202 partitions the 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 may support PUs of various sizes. As noted above, the size of the CU may refer to the size of the luma coding block of the CU, and the size of the PU may refer to the size of the luma prediction unit of the PU. Assuming that the size of a particular CU is 2Nx2N, the video encoder 200 may support PU sizes of 2Nx2N or NxN for intra-frame prediction, and symmetrical PU sizes of 2Nx2N, 2NxN, Nx2N, NxN or similar sizes for inter-frame prediction. The video encoder 200 and the video decoder 300 may also support asymmetric partitioning for PU sizes of 2NxnU, 2NxnD, nLx2N, and nRx2N for inter-frame prediction.

[0108] In an example where the mode selection unit does not further split 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 a 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 a CU size of 2Nx2N, 2NxN, or Nx2N.

[0109] For other video coding techniques (such as intra block copy mode coding, affine mode coding, and linear model (LM) mode coding, to name a few examples), the mode selection unit 202 generates a prediction block for the current block being encoded via a corresponding 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, but instead generate syntax elements indicating how 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 for encoding.

[0110] As described above, the residual generation unit 204 receives video data for a current block and a 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.

[0111] The transform processing unit 206 applies one or more transforms to the residual block to generate a block of transform coefficients (referred to herein as a "transform coefficient block"). The transform processing unit 206 can apply various transforms to the residual block to form a transform coefficient block. For example, the transform processing unit 206 can 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 transform processing unit 206 can perform a variety of transforms on the residual block, for example, a primary transform and a secondary transform (such as a rotation transform). In some examples, the transform processing unit 206 does not apply a transform to the residual block.

[0112] The quantization unit 208 may quantize the transform coefficients in the transform coefficient block to produce a quantized transform coefficient block. The quantization unit 208 may quantize the transform coefficients of the transform coefficient block according to a quantization parameter (QP) value associated with the current block. The video encoder 200 (e.g., via the mode selection unit 202) 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. Quantization may cause a loss of information, and therefore, the quantized transform coefficients may have a lower precision than the original transform coefficients produced by the transform processing unit 206.

[0113] 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 a residual block from the transform coefficient block. The reconstruction unit 214 may generate a reconstructed block corresponding to the current block (although potentially with some 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 samples of the reconstructed residual block to corresponding samples of the prediction block generated by the mode selection unit 202 to generate a reconstructed block.

[0114] Filter unit 216 may perform one or more filter operations on the reconstructed block. For example, filter unit 216 may perform a deblocking operation to reduce blocking artifacts along the edge of the CU. In some examples, the operations of filter unit 216 may be skipped.

[0115] The video encoder 200 stores the reconstructed blocks in the DPB 218. For example, in an example where the operation of the filter unit 216 is not required, the reconstruction unit 214 can store the reconstructed blocks in the DPB 218. In an example where the operation of the filter unit 216 is required, the filter unit 216 can store the filtered reconstructed blocks in the DPB 218. The motion estimation unit 222 and the motion compensation unit 224 can retrieve the reference picture formed by the reconstructed (and potentially filtered) blocks from the DPB 218 to perform inter-frame prediction on the blocks of the subsequently encoded pictures. In addition, the intra-frame prediction unit 226 can use the reconstructed blocks of the current picture in the DPB 218 to perform intra-frame prediction on other blocks in the current picture.

[0116] In general, the entropy coding unit 220 may entropy encode syntax elements received from other functional components of the video encoder 200. For example, the entropy coding unit 220 may entropy encode a quantized transform coefficient block from the quantization unit 208. As another example, the entropy coding unit 220 may entropy encode a prediction syntax element (e.g., motion information for inter-frame prediction or intra-frame mode information for intra-frame prediction) from the mode selection unit 202. The entropy coding unit 220 may perform one or more entropy coding operations on syntax elements as another example of video data to generate entropy-encoded data. For example, the entropy coding unit 220 may perform a context-adaptive variable length coding (CAVLC) operation, a CABAC operation, a variable-to-variable (V2V) length coding operation, a syntax-based context-adaptive binary arithmetic coding (SBAC) operation, a probability interval partitioning entropy (PIPE) coding operation, an exponential Golomb coding operation, or another type of entropy coding operation on the data. In some examples, the entropy coding unit 220 may operate in a bypass mode in which the syntax elements are not entropy encoded.

[0117] The video encoder 200 may output a bitstream including entropy-encoded syntax elements required for reconstructing a block of a slice or picture. Specifically, the entropy encoding unit 220 may output a bitstream.

[0118] The above operations are described with respect to blocks. Such descriptions should be understood as operations for 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 components and chroma components of a CU. In some examples, the luma coding blocks and chroma coding blocks are the luma components and chroma components of a PU.

[0119] In some examples, operations performed with respect to luma coding blocks need not be repeated for chroma coding blocks. As an example, operations for identifying motion vectors (MVs) and reference pictures for luma coding blocks need not be repeated to identify MVs and reference pictures for chroma blocks. Specifically, the MVs for luma coding blocks may be scaled to determine MVs for chroma blocks, and the reference pictures may be the same. As another example, the intra prediction process may be the same for luma coding blocks and chroma coding blocks.

[0120] As described above, the video encoder 200 represents an example of a device configured to encode video data, the device including: a memory configured to store video data; and one or more processing units implemented in a circuit and configured to: determine samples to be used for DC intra-mode prediction for a current block, wherein determining the samples includes determining a plurality of samples in a non-adjacent row or non-adjacent column, wherein the non-adjacent row has a last sample in the same column as the last column of the current block, or the non-adjacent column has a last sample in the same row as the last row of the current block. The video encoder 200 can use the determined samples to encode the current block using DC intra-mode prediction.

[0121] Figure 4 is a block diagram illustrating an example video decoder 300 that may perform the techniques of this disclosure. Figure 4 It is provided for the purpose of explanation and does not limit the techniques generally illustrated and described in this disclosure. For the purpose of explanation, this disclosure describes the video decoder 300 according to the techniques of VVC and HEVC. However, the techniques of this disclosure can be performed by a video decoding device configured for other video decoding standards.

[0122] exist Figure 4In the example of , 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 one 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 may be implemented in one or more processors or in processing circuits. In addition, the video decoder 300 may include additional or alternative processors or processing circuits to perform these and other functions.

[0123] The prediction processing unit 304 includes a motion compensation unit 316 and an intra prediction unit 318. The prediction processing unit 304 may include an addition unit that performs predictions according to other prediction modes. As an 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, etc. In other examples, the video decoder 300 may include more, fewer, or different functional components.

[0124] CPB memory 320 may store video data, such as an encoded video bitstream, to be decoded by components of video decoder 300. For example, the video bitstream may be obtained from computer readable medium 110 ( Figure 1 ) obtains video data stored in CPB memory 320. CPB memory 320 may include a CPB that stores encoded video data (e.g., syntax elements) from an encoded video bitstream. In addition, CPB memory 320 may store video data other than syntax elements of decoded pictures, such as temporary data representing outputs from various units of video decoder 300. DPB 314 typically stores decoded pictures, and video decoder 300 may output decoded pictures, and / or use decoded pictures as reference video data when decoding subsequent data or pictures of the encoded video bitstream. CPB memory 320 and DPB 314 may be formed by any of a variety of memory devices, such as DRAM, including SDRAM, MRAM, RRAM or other types of memory devices. CPB memory 320 and DPB 314 may be provided by the same memory device or a separate memory device. In various examples, CPB memory 320 may be on-chip with other components of video decoder 300, or off-chip relative to those components.

[0125] Additionally or alternatively, in some examples, video decoder 300 may retrieve the video from memory 120 ( Figure 1) to retrieve the decoded video data. That is, memory 120 may utilize CPB memory 320 to store data as discussed above. Likewise, when some or all of the functions of video decoder 300 are implemented in software to be executed by processing circuitry of video decoder 300, memory 120 may store instructions to be executed by video decoder 300.

[0126] Explained in Figure 4 The various units shown in FIG. 3 are used to help understand the operations performed by the video decoder 300. These units may be implemented as fixed function circuits, programmable circuits, or a combination thereof. Figure 3 , fixed-function circuits refer to circuits that provide specific functions and are pre-set with respect to the operations that can be performed. Programmable circuits refer to circuits that can be programmed to perform various tasks and provide flexible functions with respect to the operations that can be performed. For example, a programmable circuit can execute software or firmware that causes the programmable circuit to operate in a manner defined by the instructions of the software or firmware. Fixed-function circuits can execute software instructions (e.g., to receive parameters or output parameters), but the types of operations performed by fixed-function circuits are generally immutable. In some examples, one or more of these units may be different circuit blocks (fixed-function or programmable), and in some examples, one or more units may be integrated circuits.

[0127] The video decoder 300 may include an ALU, an EFU, a digital circuit, an analog circuit, and / or a programmable core formed by a programmable circuit. In an example where the operation of the video decoder 300 is performed by software executed on the programmable circuit, an on-chip or off-chip memory may store instructions (e.g., object code) of the software received and executed by the video decoder 300.

[0128] The entropy decoding unit 302 may receive the encoded video data from the CPB and entropy decode the video data to reproduce the syntax elements. The prediction processing unit 304, the inverse quantization unit 306, the inverse transform processing unit 308, the reconstruction unit 310, and the filter unit 312 may generate decoded video data based on the syntax elements extracted from the bitstream.

[0129] Generally, the video decoder 300 reconstructs a picture block by block. The video decoder 300 may perform a reconstruction operation on each block individually (wherein a block currently being reconstructed (ie, decoded) may be referred to as a "current block").

[0130] The entropy decoding unit 302 may entropy decode syntax elements defining the quantized transform coefficients of the quantized transform coefficient block and transform information such as a quantization parameter (QP) and / or a transform mode indication. The inverse quantization unit 306 may use the QP associated with the quantized transform coefficient block to determine a degree of quantization and, likewise, determine a degree of inverse quantization for the inverse quantization unit 306 to apply. The inverse quantization unit 306 may, for example, perform a bitwise left shift operation to inverse quantize the quantized transform coefficients. The inverse quantization unit 306 may thereby form a transform coefficient block including the transform coefficients.

[0131] 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 rotational transform, an inverse directional transform, or another inverse transform to the coefficient block.

[0132] In addition, prediction processing unit 304 generates a prediction block based on the prediction information syntax elements entropy decoded by entropy decoding unit 302. For example, if the prediction information syntax elements indicate that the current block is inter-predicted, motion compensation unit 316 can generate a prediction block. In this case, the prediction information syntax elements can indicate a reference picture in DPB 314 from which to retrieve the reference block, and a motion vector that identifies the position of the reference block in the reference picture relative to the position of the current block in the current picture. Motion compensation unit 316 can generally generate a prediction block in the same manner as described for motion compensation unit 224 ( Figure 3 )The inter-frame prediction process is performed in a manner substantially similar to that described in detail above.

[0133] 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. Again, the intra-prediction unit 318 may generally generate a prediction block in the same manner as described with respect to the intra-prediction unit 226 ( Figure 3 The intra prediction process is performed in a substantially similar manner as described in the foregoing description. The intra prediction unit 318 may retrieve data of neighboring samples of the current block from the DPB 314.

[0134] In one or more examples described in the present disclosure, the intra prediction unit 318, alone or in combination with one or more other components, can be configured to perform one or more of the example techniques described in the present disclosure. As an example, the prediction processing unit 304 can be configured to determine that a current block of video data is to be predicted using DC intra mode prediction (e.g., based on receiving information indicating a prediction mode for the current block signaled by the video encoder 200). In some examples of DC intra mode prediction, the samples used to generate the prediction block are samples in an immediately adjacent row (e.g., a row immediately above the current block) or column (e.g., a column immediately to the left of the current block).

[0135] However, in some examples of DC intra mode prediction, samples may come from non-adjacent rows and / or non-adjacent columns. Non-adjacent rows refer to rows that may be above the current block but not immediately above the current block in the same picture. Non-adjacent columns refer to columns that may be to the left of the current block but not immediately to the left of the current block in the same picture. Figure 11-19 The example shown in describes an example of non-contiguous rows and columns.

[0136] As part of DC intra mode prediction, prediction processing unit 304 may generate information indicating which of the non-adjacent rows and / or non-adjacent columns includes samples that may be used for DC intra mode prediction. For example, video decoder 300 may receive a syntax element indicating the number of rows or columns of non-adjacent sample rows above a current block or the number of rows or columns of non-adjacent sample columns to the left of the current block. Prediction processing unit 304 may utilize the syntax element to determine which non-adjacent rows and / or non-adjacent columns include samples for DC intra mode prediction of the current block.

[0137] In one or more examples, the intra prediction unit 318 can be configured to determine a plurality of samples to be used for DC intra mode prediction for the current block. For example, the intra prediction unit 318 can be configured to determine a plurality of samples in at least one of the non-adjacent sample rows having a last sample in the same column as the last column of the current block. The non-adjacent sample row is more than one row above the current block. The intra prediction unit 318 can be configured to determine a non-adjacent sample column having a last sample in the same row as the last row of the current block. The non-adjacent sample column is more than one column to the left of the current block. For example, as described with respect to Figure 16-19 Described in more detail, the last sample (e.g., the rightmost sample) from the plurality of samples in non-adjacent rows may be in the same column (e.g., have the same x-coordinate) as the last column (e.g., the rightmost column) of the current block, and the last sample (e.g., the bottommost sample) from the plurality of samples in non-adjacent columns may be in the same row (e.g., have the same y-coordinate) as the last row (e.g., the bottommost row) of the current block.

[0138] In some examples, such as regarding Fig.16 and 17 Described in more detail, the first sample (e.g., the rightmost sample) from the plurality of samples in non-adjacent rows may be in the same column (e.g., have the same x-coordinate) as the first column (e.g., the leftmost column) of the current block. The first sample (e.g., the topmost sample) from the plurality of samples in non-adjacent columns may be in the same row (e.g., have the same y-coordinate) as the first row (e.g., the topmost row) of the current block.

[0139] In this way, the intra prediction unit 318 can determine samples from non-adjacent rows or columns that are aligned with the current block to be used for the DC intra prediction mode. Some other techniques contemplate using samples from non-adjacent rows or columns that are not aligned with the current block (e.g., the last sample or the first sample in the non-adjacent rows or columns is not in the same row or column as the last row or column or the first row or column of the current block). Using such samples from non-adjacent rows or columns that are not aligned with the current block may result in larger residuals than using samples from non-adjacent rows or columns that are aligned with the current block, and may also require reading additional samples.

[0140] As described in more detail, the video decoder 300 can be configured to decode the current block using the determined samples from non-adjacent rows or columns using the DC intra prediction mode. For example, the intra prediction unit 318 can generate a prediction block using samples from non-adjacent rows and / or non-adjacent columns. As described above, the entropy decoding unit 302, the inverse quantization unit 306, and the inverse transform processing unit 308 may have determined a residual block.

[0141] The reconstruction unit 310 may reconstruct the current block using the prediction block and the residual block. For example, the reconstruction unit 310 may reconstruct the current block by adding samples of the residual block to corresponding samples of the prediction block.

[0142] 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 operations of the filter unit 312 may not necessarily be performed in all examples.

[0143] The video decoder 300 may store the reconstructed blocks in the DPB 314. As discussed 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. In addition, the video decoder 300 may output decoded pictures from the DPB 314 for use in, for example, Figure 1 Subsequent presentation on a display device such as display device 118.

[0144] In this way, video decoder 300 represents an example of a video decoding device that includes: a memory configured to store video data; and one or more processing units implemented in circuitry and configured to: determine samples to be used for DC intra-mode prediction for a current block, where determining the samples includes determining a plurality of samples in a non-adjacent row or non-adjacent column that have a last sample in the same column as the last column of the current block or a last sample in the same row as the last row of the current block in the non-adjacent column. Video decoder 300 uses the determined samples to decode the current block using DC intra-mode prediction.

[0145] As described above, the example techniques described in this disclosure may relate to intra-prediction modes. Intra-prediction angles and wide-angle intra-prediction are described below. Intra-prediction includes a DC prediction mode, a planar prediction mode, and a direction (or angle) prediction mode. The direction prediction for square blocks uses directions between -135 degrees and 45 degrees for the current block in the Versatile Video Coding Test Model 2 (VTM2) (Chen, Y. Ye, S. Kim, "Algorithm description for Versatile Video Coding and Test Model 2 (VTM2)", 11th JVET Conference, Ljubljana, Slovenia, July 2018, JVET-K1002), as Figure 5 shown.

[0146] In VTM2, the block structure for specifying the prediction block for intra-prediction is not limited to square (width w = height h). Rectangular or non-square prediction blocks (w > h or w < h) can improve the decoding efficiency based on the characteristics of the content.

[0147] In such a rectangular block, restricting the intra-prediction direction within -135 degrees to 45 degrees may result in a situation where intra-prediction uses a farther reference sample instead of a nearer reference sample. This design is likely to have an impact on the decoding efficiency. It may be more beneficial to relax the restricted range so that nearer reference samples (beyond -135 to 45 degrees) can be used for prediction. An example of this situation is given in Figure 6 For example, Figure 6 shows an example of an 8x4 rectangular block identified as current block 500, where, due to the intra-prediction direction being restricted within the range of -135 degrees to 45 degrees, a nearer reference sample (e.g., reference sample 502) is not used, and a farther reference sample (e.g., reference sample 504) can be used.

[0148] VTM2 also makes use of wide angles. In Figure 8 An example of the wide angle employed in VTM2 is shown in FIG.

[0149] During the 12th JVT meeting, modifications to wide-angle intra prediction were adopted in VVC Test Model 3.0 (VTM3), as described in the following documents: L. Zhao, X. Zhao, S. Liu, X. Li, “CE3-related: Unification of angular intra prediction for square and non-square blocks,” 12th JVT Meeting, Macao SAR, China, October 2018, JVET-L0279; J. Chen, Y. Ye, S. Kim, “Algorithm description for Versatile Video Coding and Test Model 3 (VTM3),” 12th JVET Meeting, Macao SAR, China, October 2018, JVET-L1002; and B. Bross, J. Chen, S. Liu, “Versatile Video Coding (Draft3),” 12th JVET Meeting, Macao SAR, China, October 2018, JVET-L1001.

[0150] This adoption of wide-angle intra prediction includes two modifications to unify angular intra prediction for square and non-square blocks. First, the angular prediction directions are modified to cover diagonal directions for all block shapes. Second, for all block aspect ratios (square and non-square), all angular directions are kept in the range between the lower left diagonal direction and the upper right diagonal direction, e.g. Figures 7A-7C shown. Fig. 7A It is shown that a square block (eg, coding unit 602) does not require angular mode remapping (eg, angular directions between diagonal direction 604 and diagonal direction 606 are available). Figure 7B Angular mode remapping is shown for horizontal non-square blocks (eg, coding unit 612). For example, there is a mapping of modes A and B outside of diagonal direction 614 to modes within diagonal direction 614 and diagonal direction 616. Figure 7C An angular remapping is shown for a vertical non-square block, such as coding unit 622. For example, there is a mapping of modes A and B outside of diagonal direction 624 to modes within diagonal direction 624 and diagonal direction 626.

[0151] Additionally, the number of reference samples in the top reference row and left reference column is restricted to 2*width+1 and 2*height+1 for all block shapes. Fig. 9A diagram of a wider angle employed in VTM3 (e.g., relative to Figure 8 ). Although VTM3 defines 95 modes, for any block size, only 67 modes may be allowed. The exact modes allowed depend on the ratio of block width to block height. Allowing exact modes is done by limiting the range of modes for a particular block size.

[0152] Fig.10 Specifies the mapping table between predModeIntra in VTM3 and the intra prediction angle parameter intraPredAngle, as described in JVET-L1001. Angular modes corresponding to non-square block diagonals, vertical and horizontal modes, and square block diagonals are utilized. Fig.10 In the example, angle patterns with positive intraPredAngle values ​​are referred to as positive angle patterns (pattern index <18 or >50), while angle patterns with negative intraPredAngle values ​​are referred to as negative angle patterns (pattern index >18 and <50).

[0153] The reverse angle parameter invAngle is derived based on intraPredAngle as follows:

[0154]

[0155] In some examples, intraPredAngle values ​​that are multiples of 32 (0, 32, 64, 128, 256, 512) may always correspond to predictions from non-fractional reference array samples, as is the case in the VTM3 specification.

[0156] Table 1

[0157] Block aspect ratio (width / height) Diagonal Mode 1(square) 2,34,66 2 8,28,72 4 12,24,76 8 14,22,78 16 16,20,80 1 / 2 -6,40,60 1 / 4 -10,44,56 1 / 8 -12,46,54 1 / 16 -14,48,52

[0158] Multiple reference line prediction is described below. Samples in the neighborhood of a coded block are used for intra prediction of the block. Typically, the reconstructed reference sample lines closest to the left and top borders of the coded block are used as reference samples for intra prediction. However, VVC WD4 also enables other samples in the neighborhood of a coded block to be used as reference samples. Fig.11 Reference sample lines that can be used for intra prediction are shown. For each coded block, an index indicating the used reference row is signaled.

[0159] In VVC WD4, only reference lines with MRLIdx equal to 0, 1 and 3 can be used. The indices of the reference lines used to decode the block (values ​​0, 1 and 2 indicate lines with MRLIdx 0, 1 and 3, respectively) are decoded using truncated unary codewords. Planar and DC modes are not used for reference lines with MRLIdx>0.

[0160] For example, in Fig.11 In , for the current block 700, the intra prediction unit 226 of the video encoder 200 and the intra prediction unit 318 of the video decoder 300 may determine which row and which column include reference samples that may be used for intra prediction. Fig.11 , reference sample 702 refers to a reference sample from a row above the current block 700, and reference sample 704 refers to a reference sample from a column to the left of the current block 700. The video encoder 200 may signal a syntax element (e.g., MRLIdx) indicating the number of rows or columns of non-adjacent sample rows above the current block or non-adjacent sample columns to the left of the current block. Similarly, the video decoder 300 may receive a syntax element (e.g., MRLIdx) indicating the number of rows or columns of non-adjacent sample rows above the current block or non-adjacent sample columns to the left of the current block. For example, if MRLIdx is equal to 0, samples in rows and columns immediately above and to the left of the current block 700 may be utilized. If MRLIdx is equal to 1, samples in non-adjacent rows or columns two rows above or two columns to the left of the current block 700 may be utilized. If MRLIdx is equal to 3, samples in non-adjacent rows or columns four rows above or four columns to the left of the current block 700 may be utilized.

[0161] The DC intra prediction mode is described below. The DC intra prediction mode is one of the prediction modes in which the prediction block is filled with a "DC value" derived from neighboring reference samples. In VVC, reference samples near the top and left boundaries of the block are used to derive the DC value. The exact derivation depends on the aspect ratio of the block and is derived as follows (from Section 8.4.5.2.11 of JVET WD5):

[0162] The input to this process is:

[0163] – the variable nTbW, which specifies the transform block width,

[0164] – the variable nTbH, which specifies the transform block height,

[0165] – variable refIdx, which specifies the intra prediction reference row index,

[0166] – Neighboring samples p[x][y], where x=-1-refIdx, y=-1-refIdx..nTbH-refIdx-1 and x=-refIdx..nTbW-1-refIdx, y=-1-refIdx.

[0167] The output of this process is the predicted samples predSamples[x][y], where x=0..nTbW-1, y=0..nTbH-1.

[0168] The values ​​of the prediction samples predSamples[x][y] (where x=0..nTbW-1, y=0..nTbH-1) are derived by the following sequential steps:

[0169] 1. Derived variable dcVal as follows:

[0170] – When nTbW is equal to nTbH:

[0171]

[0172] – When nTbW is greater than nTbH:

[0173]

[0174] – When nTbW is less than nTbH:

[0175]

[0176] 2. Derived prediction samples predSamples[x][y] are as follows:

[0177] predSamples[x][y]=dcVal, where x=0..nTbW-1, y=0..nTbH-1

[0178] (8-117)

[0179] Some techniques for DC intra mode prediction may have technical issues that negatively affect the decoding process. For example, for the case where a directly adjacent reference line (e.g., row or column) is used for prediction (i.e., MRLIdx is equal to 0), the DC value can be calculated from samples above and to the left of the current block. The reference samples used are aligned with the top and left boundaries of the current block 706, such as Fig.12 shown.

[0180] When MRLIdx is greater than 0, the reference sample (from the corresponding line (e.g., row or column)) is no longer aligned with the top and left boundaries of the current block. Fig.13 and 14 As shown, when MRLIdx>0 (eg, indicating that the reference samples are from non-adjacent rows or columns), the reference samples are shifted from the boundary of the block by an offset (and therefore are not aligned). Fig.13 , MRLIdx is equal to 1, and as shown, the samples that can be used for DC intra prediction for the current block 708 are not aligned by 1 sample. Fig.14, MRLIdx is equal to 3, and as shown, the samples that can be used for DC intra prediction for the current block 710 are not aligned by 3 samples.

[0181] This misalignment is more severe in cases where one or more boundaries are small (e.g., 4x4 blocks), where for MRLIdx=3, only one sample overlaps, as Fig.15 For example, Fig.15 The current block 712 is shown. In this case, the misalignment of the samples used for intra prediction of the current block 712 is 3 samples. Since the current block 712 is 4x4, Fig.15 As shown, therefore, among the samples in the column to the left of the current block, only one sample is aligned with the top row of the current block 712, and among the samples in the row above the current block, only one sample is aligned with the first column of the current block 712.

[0182] This misalignment may lead to less accurate prediction of the DC value and, therefore, poorer and / or less optimal DC prediction. Although the illustrations here depict square blocks, this misalignment also occurs in the case of rectangular blocks, but in one direction in the VVC (either top or left based on the aspect ratio).

[0183] The present disclosure describes example techniques for improving the design of DC intra mode prediction. The example techniques can be implemented individually or together. In general, a video decoder can determine samples to be used for DC intra mode prediction of a current block. To determine the samples, the video decoder can be configured to determine a plurality of samples in a non-adjacent row or a non-adjacent column having a last sample in the same column as the last column of the current block in the non-adjacent row, or having a last sample in the same row as the last row of the current block in the non-adjacent column.

[0184] For example, Fig.16 As shown in FIG. 19 , the darkened blocks show reference samples from non-adjacent sample rows or columns (e.g., non-adjacent lines) for DC intra mode prediction (e.g., intra prediction in DC mode). For non-adjacent rows, the last sample (e.g., rightmost) in the non-adjacent row may be in the same column as the last column of the current block being decoded. For non-adjacent columns, the last sample (e.g., bottommost) in the non-adjacent column may be in the same row as the last row of the current block being decoded.

[0185] In some examples, the first sample in a non-contiguous row (e.g., leftmost) may be in the same column as the first column of the current block being decoded. However, in some examples, the first sample in a non-contiguous row may be in a column to the left of the first column of the current block being decoded. In some examples, the first sample in a non-contiguous row (e.g., topmost) may be in the same row as the first row of the current block being decoded. However, in some examples, the first sample in a non-contiguous column may be in a row above the first row of the current block being decoded.

[0186] For example, a video decoder (eg, video encoder 200 or video decoder 300) may be configured to determine the video signal to be used for the video signal. Fig.16 In order to determine the samples, the video decoder may be configured to determine a plurality of samples in at least one of the following: a non-adjacent sample row having a last sample 722 in the same column as the last column of the current block 714 (e.g., Fig.16 ), or a non-contiguous sample column (e.g., column 718) having a last sample 726 in the same row as the last row of the current block 714.

[0187] For example, in Fig.16 , sample 722 is the last sample of the plurality of samples in row 716 in the same column as the last column of the current block 714, and sample 726 is the last sample of the plurality of samples in column 718 in the same row as the last row of the current block 714. There may be more samples to the right of sample 722 in row 716, and there may be more samples below sample 726 in column 718. However, samples used for DC intra prediction of the current block 714 may not extend to the right of sample 722 in row 716 or below sample 726 in column 718. Fig.16 , non-adjacent sample rows (eg, samples in row 716 ) are more than one row above the current block 714 , and non-adjacent sample columns (eg, samples in column 718 ) are more than one column to the left of the current block 714 .

[0188] The video decoder may be configured to decode (e.g., encode or decode) the current block 714 using DC intra mode prediction using the determined samples. For example, the video decoder 300 may be configured to perform the following operations: generate a prediction block based on a plurality of samples; determine a residual block indicating a difference between the current block 714 and the prediction block; and reconstruct the current block 714 based on the residual block and the prediction block. The video encoder 200 may be configured to perform the following operations: generate a prediction block based on a plurality of samples; determine a residual block indicating a difference between the current block 714 and the prediction block; and signal information indicating the residual block.

[0189] In the above description, sample 722 is aligned with the last column of the current block 714, and sample 726 is aligned with the last row of the current block 714. In some examples, a non-adjacent sample row (e.g., row 716) having a last sample 722 in the same column as the last column of the current block 714 includes a first sample 720 in the same column as the first column of the current block 714. Furthermore, in some examples, a non-adjacent sample column (e.g., column 718) having a last sample 726 in the same row as the last row of the current block 714 includes a first sample 724 in the same row as the first row of the current block 714. There may be samples to the left of sample 720 and samples above sample 720. However, in some examples, for intra prediction, samples from row 716 for DC intra mode prediction may be limited to samples aligned with the leftmost and rightmost columns of the current block 714, and samples from column 718 for DC intra mode prediction may be limited to samples aligned with the topmost and bottommost rows of the current block 714.

[0190] Fig.16 The current block 714 can be regarded as the first block, and Fig.17 The current block 728 of can be considered as the second block. In some examples, the alignment of samples of the current block 728 can be similar to the alignment of the current block 714; however, compared with the current block 714, the rows and columns from which the samples used for DC intra mode prediction come can be farther away from the current block 728.

[0191] For example, a video decoder (eg, video encoder 200 or video decoder 300) may be configured to determine the video signal to be used for the video signal. Fig.17 In order to determine the samples, the video decoder may be configured to determine a plurality of samples in at least one of the following: a non-adjacent sample row having a last sample 736 in the same column as the last column of the current block 728 (e.g., Fig.17 ), or a non-contiguous sample column (e.g., column 732) having a last sample 740 in the same row as the last row of the current block 728.

[0192] For example, in Fig.17 , sample 736 is the last sample of the plurality of samples in row 730 in the same column as the last column of the current block 728, and sample 740 is the last sample of the plurality of samples in column 732 in the same row as the last row of the current block 728. There may be more samples to the right of sample 736 in row 730, and there may be more samples below sample 740 in column 732. However, the samples used for DC intra prediction of the current block 728 may not extend to the right of sample 736 in row 730 or below sample 740 in column 732. Fig.17 , non-adjacent sample rows (eg, samples in row 730 ) are more than three rows above the current block 728 , and non-adjacent sample columns (eg, samples in column 732 ) are more than three columns to the left of the current block 728 .

[0193] The video decoder may be configured to perform intra-frame prediction decoding (e.g., encoding or decoding) on ​​the current block 728 based on the determined samples. For example, the video decoder 300 may be configured to perform the following operations: generate a prediction block based on multiple samples; determine a residual block, the residual block indicating the difference between the current block 728 and the prediction block; and reconstruct the current block 728 based on the residual block and the prediction block. The video encoder 200 may be configured to perform the following operations: generate a prediction block based on multiple samples; determine a residual block, the residual block indicating the difference between the current block 728 and the prediction block; and signal information indicating the residual block.

[0194] In the above description, sample 736 is aligned with the last column of the current block 728, and sample 740 is aligned with the last row of the current block 728. In some examples, a non-adjacent sample row (e.g., row 730) having a last sample 736 in the same column as the last column of the current block 728 includes a first sample 734 in the same column as the first column of the current block 728. Furthermore, in some examples, a non-adjacent sample column (e.g., column 732) having a last sample 740 in the same row as the last row of the current block 728 includes a first sample 738 in the same row as the first row of the current block 728. There may be samples to the left of sample 734 and samples above sample 738. However, in some examples, for intra prediction, samples from row 730 for DC intra mode prediction may be limited to samples aligned with the leftmost and rightmost columns of the current block 728, and samples from column 732 for DC intra mode prediction may be limited to samples aligned with the topmost and bottommost rows of the current block 728.

[0195] exist Fig.16 and 17 In the example, for MRLIdx greater than zero, the video decoder may use reference samples aligned with the block boundary for DC prediction. Let (x0, y0) represent the position of the top left sample of the current block 714 or the current block 728, and nW and nH represent the width and height of the current block 714 or 728, respectively. Let MRLIdx represent the index of the reference line. The top reference samples for DC prediction may include samples at the following positions: (x, y0–MRLIdx-1), where x=x0..x0+nW–1. The left reference samples for DC prediction may include samples at the following positions: (x0–MRLIdx-1, y), where y=y0..y0+nH–1. For example, respectively at Fig.16 and17 Reference samples for MRLIdx equal to 1 and MRLIdx equal to 3 are shown in .

[0196] For MRLIdx greater than zero, the video decoder can use reference samples aligned with the block boundary for DC prediction, and additionally can use more reference samples for more accurate prediction. Let (x0, y0) represent the position of the top left sample of the current block, and nW and nH represent the width and height of the block. Let MRLIdx represent the index of the reference line. The top reference samples for DC prediction may include samples at the following positions: (x-MRLIdx, y0–MRLIdx-1), where x=x0..x0+nW+MRLIdx–1. The left reference samples for DC prediction include samples at the following positions: (x0–MRLIdx-1, y-MRLIdx), where y=y0..y0+nH+MRLIdx–1. For example, respectively at Fig.19 Utilize the current block 742 and Fig. 20 Reference samples for MRLIdx equal to 1 and MRLIdx equal to 3 are shown with current block 744 .

[0197] In some examples, the reference sample at position (x0-MRLIdx-1, y0-MRLIdx-1) can be used with the top or left of both the top and left reference samples to calculate the DC value for the current block. The video coder can use a weighted average of the reference samples, with the weights determined by one or more of the following factors: block size, aspect ratio, width, height, MRLIdx, intra-mode of neighboring blocks, etc.

[0198] Let valSumTop be the sum of the reference sample values ​​for DC prediction for a specific MRLIdx at the top of the current block. Let valSumLeft be the sum of the reference sample values ​​for DC prediction for a specific MRLIdx on the left side of the current block. The DC value for DC intra prediction is obtained as follows: dcVal = (wT*valSumTop+wL*valSumLeft+off)>>sh, where off represents an offset and sh represents a shift (in some examples, the above calculation using off and sh can be replaced by a division operation). wT and wL are weights associated with the top and left reference samples and can be derived as a function of block characteristics. For example, wT and wL can be specified as follows:

[0199]

[0200] The values ​​of off and sh may depend on the values ​​of wT, wL, nW, and nH. In the above example, sh=2+((nW>nH)?Log2(nW):(nW <nH?Log2(nH):Log2(2*nW)),off=1<<(sh–1)。

[0201] In some examples, DC values ​​obtained from different weights may be considered in separate DC modes. For example, multiple DC modes may be defined, where each DC mode may reference a specific set of weights for top and left reference samples. In some examples, reference sample positions used in DC value calculations may be considered in separate DC modes. Multiple DC modes may be defined, where each DC mode may reference a specific set of neighbors to be used for top and left reference samples.

[0202] The following references may also provide some information for intra prediction: S. De Luxán Hernández, H. Schwarz, D. Marpe, T. Wiegand (HHI) "CE3: Line-based intra coding mode", JVET-L0076; S. De Luxán Hernández, V. George, J. Ma, T. Nguyen, H. Schwarz, D. Marpe, T. Wiegand (HHI), "CE3: Intra Sub-Partitions Coding Mode", JVET-M0102; J. Chen, Y. Ye, S. H. Kim, "Algorithm description for Versatile Video Coding and Test Model 3 (VTM3)", JVET-L1002, Macau, China, October 2018; F. Bossen, K. Misra, "Non-CE3: A unified luma intramode list construction process", JVET-M0528; and J. Yao, J. Zhu, W. Cai, K. Kazui, "Non-CE3: Intra prediction information coding", JVET-M0210.

[0203] The following is an example technique in which the reference samples that can be used for DC prediction are aligned with the top and left boundaries of the prediction block (e.g., as Fig.16 and 17 ). Below are the proposed changes to the specification (e.g., VVC draft 5). Double brackets in bold ([[…]]) indicate removals / deletions.

[0204] 8.4.5.2.12 Specification of INTRA_DC intra prediction mode

[0205] The input to this process is:

[0206] – the variable nTbW, which specifies the transform block width,

[0207] – the variable nTbH, which specifies the transform block height,

[0208] – variable refIdx, which specifies the intra prediction reference line index,

[0209] – Neighboring samples p[x][y], where x=-1-refIdx, y=-1-refIdx..nTbH[[-refIdx]]–1, and x=-refIdx..nTbW-1[[-refIdx]], y=-1-refIdx.

[0210] The output of this process is the predicted samples predSamples[x][y], where x=0..nTbW-1, y=0..nTbH-1.

[0211] The values ​​of the prediction samples predSamples[x][y] (where x=0..nTbW-1, y=0..nTbH-1) are derived by the following sequential steps:

[0212] 3. Derived variable dcVal as follows:

[0213] – When nTbW is equal to nTbH:

[0214]

[0215] – When nTbW is greater than nTbH:

[0216]

[0217] – When nTbW is less than nTbH:

[0218]

[0219] 4. Derived prediction samples predSamples[x][y] are as follows:

[0220] predSamples[x][y]=dcVal, where x=0..nTbW-1, y=0..nTbH-1

[0221] (8-117)

[0222] Fig.192 is a flowchart illustrating an example method for encoding a current block. The current block may include a current CU. Although with respect to the video encoder 200 ( Figure 1 and Figure 3 ), but it should be understood that other devices may be configured to perform the same Fig.19 A memory (eg, memory 106, video data memory 230, DPB 218, or some other memory) may be configured to store one or more samples of rows or columns that are not adjacent to the current block.

[0223] Processing circuitry of the video encoder 200 (e.g., the processing circuitry includes the intra prediction unit 226, the mode selection unit 202, and one or more other components of the video encoder 200) may be configured to determine samples to be used for DC intra mode prediction for a current block, wherein, to determine the samples, the processing circuitry is configured to determine a plurality of samples from at least one of: a non-adjacent sample row having a last sample in the same column as a last column of the current block, wherein the non-adjacent sample row is more than one row above the current block; or a non-adjacent sample column having a last sample in the same row as a last row of the current block, wherein the non-adjacent sample column is more than one column to the left of the current block (800). In some examples, the non-adjacent sample row having a last sample in the same column as a last column of the current block includes a first sample in the same column as a first column of the current block, and / or the non-adjacent sample column having a last sample in the same row as a last row of the current block includes a first sample in the same row as a first row of the current block.

[0224] As an example, the coordinates for the top left sample of the current block are (x0, y0), nW is the width of the current block, and nH is the height of the current block, and MRLIdx indicates the number of rows or columns of non-adjacent sample rows above the current block or the number of rows or columns of non-adjacent sample columns to the left of the current block. The processing circuitry of the video encoder 200 may be configured to determine at least one of a non-adjacent sample row having coordinates (x, y0-MRLIdx-1) (where x=x0...x0+nW-1) or a non-adjacent sample column having coordinates (x0-MRLIdx-1, y) (where y=y0...y0+nH-1).

[0225] The processing circuitry of the video encoder 200 may generate a prediction block based on a plurality of samples (802). The processing circuitry of the video encoder 200 may determine a residual block indicating a difference between the prediction block and the current block (804). The processing circuitry of the video encoder 200 may signal information indicating the residual block (806). The processing circuitry of the video encoder 200 may also signal a syntax element (e.g., MRLIdx) indicating the number of rows or columns of non-adjacent sample rows above the current block or the number of rows or columns of non-adjacent sample columns to the left of the current block (808).

[0226] Fig. 20 3 is a flowchart illustrating an example method for decoding a current block of video data. The current block may include a current CU. Although with respect to the video decoder 300 ( Figure 1 and Figure 4 ), but it should be understood that other devices may be configured to perform the same Fig. 20 A method similar to the method of . A memory (e.g., memory 120, CPB memory 320, DPB 314, or some other memory) may be configured to store one or more samples of rows or columns that are not adjacent to the current block. The processing circuitry of the video decoder 300 may receive a syntax element (e.g., MRLIdx) indicating the number of rows or columns of non-adjacent sample rows above the current block or the number of rows or columns of non-adjacent sample columns to the left of the current block (900).

[0227] Processing circuitry of the video decoder 300 (e.g., the processing circuitry includes the intra prediction unit 318, the prediction processing unit 304, and one or more other components of the video decoder 300) may be configured to determine samples to be used for DC intra mode prediction for a current block, wherein, to determine the samples, the processing circuitry is configured to determine a plurality of samples from at least one of: a non-contiguous sample row having a last sample in the same column as a last column of the current block, wherein the non-contiguous sample row is more than one row above the current block; or a non-contiguous sample column having a last sample in the same row as a last row of the current block, wherein the non-contiguous sample column is more than one column to the left of the current block (902). In some examples, the non-contiguous sample row having a last sample in the same column as a last column of the current block includes a first sample in the same column as a first column of the current block, and / or the non-contiguous sample column having a last sample in the same row as a last row of the current block includes a first sample in the same row as a first row of the current block.

[0228] As an example, the coordinates for the top left sample of the current block are (x0, y0), nW is the width of the current block, and nH is the height of the current block, and MRLIdx indicates the number of rows or columns of non-adjacent sample rows above the current block or the number of rows or columns of non-adjacent sample columns to the left of the current block. The processing circuitry of the video decoder 300 may be configured to determine at least one of a non-adjacent sample row having coordinates (x, y0-MRLIdx-1) (where x=x0...x0+nW-1) or a non-adjacent sample column having coordinates (x0-MRLIdx-1, y) (where y=y0...y0+nH-1).

[0229] The processing circuitry of video decoder 300 may generate a prediction block based on the plurality of samples (904). The processing circuitry of video decoder 300 may determine a residual block indicating a difference between the prediction block and the current block (906). The processing circuitry of the video decoder may reconstruct the current block based on the residual block and the prediction block (908).

[0230] One or more examples are described below. The example techniques may be used alone or in combination.

[0231] Example 1. A method for decoding video data, the method comprising: determining samples to be used for DC intra-frame mode prediction for a current block, wherein determining the samples comprises: determining multiple samples in non-adjacent rows or non-adjacent columns, the multiple samples having a last sample in the same column as the last column of the current block in the non-adjacent rows or having a last sample in the same row as the last row of the current block in the non-adjacent columns; and using the determined samples to perform intra-frame prediction decoding on the current block.

[0232] Example 2. The method according to Example 1, wherein intra-frame prediction decoding includes: performing intra-frame prediction decoding on the current block.

[0233] Example 3. A method according to Example 2, wherein intra-frame prediction decoding includes: determining a prediction block based on the multiple samples; determining a residual block, the residual block indicating a difference between the current block and the prediction block; and reconstructing the current block based on the residual block and the prediction block.

[0234] Example 4. The method according to Example 1, wherein intra-frame prediction decoding includes: performing intra-frame prediction encoding on the current block.

[0235] Example 5. A method according to Example 4, wherein intra-frame prediction coding includes: determining a prediction block based on the multiple samples; determining a residual block, the residual block indicating a difference between the current block and the prediction block; and signaling information indicating the residual block.

[0236] Example 6. A method according to any one of Examples 1-5, wherein the multiple samples in the non-adjacent row or the non-adjacent column having the last sample in the non-adjacent row in the same column as the last column of the current block or the last sample in the non-adjacent column in the same row as the last row of the current block include: multiple samples in the non-adjacent row or the non-adjacent column having the first sample in the non-adjacent row in the same column as the first column of the current block or the first sample in the non-adjacent column in the same row as the first row of the current block.

[0237] Example 7. A method according to any one of Examples 1-5, wherein the multiple samples in the non-adjacent row or the non-adjacent column having a last sample in the same column as the last column of the current block or a last sample in the non-adjacent column having a last sample in the same row as the last row of the current block include: multiple samples in the non-adjacent row or the non-adjacent column having a first sample in a column to the left of the first column of the current block or a first sample in the non-adjacent column having a first sample in a row above the first row of the current block.

[0238] Example 8. A device for decoding video data, the device comprising: a memory configured to store one or more samples of rows and columns that are non-adjacent to a current block; and a video decoder comprising at least one of a fixed-function circuit or a programmable circuit, wherein the video decoder is configured to perform the method described in any one or combination of Examples 1-7.

[0239] Example 9. The device of Example 8, further comprising: a display configured to display the decoded video data.

[0240] Example 10. A device according to any of Examples 8 and 9, wherein the device includes one or more of a camera, a computer, a mobile device, a broadcast receiver device, or a set-top box.

[0241] Example 11. A computer-readable storage medium having instructions stored thereon, which instructions, when executed, cause one or more processors to perform a method according to any one of Examples 1-7.

[0242] Example 12. An apparatus for decoding video data, the apparatus comprising means for performing the method according to any one of Examples 1-7.

[0243] It is to be appreciated that, according to examples, certain actions or events of any of the techniques described herein may be performed in a different order, may be added, combined, or omitted entirely (e.g., not all described actions or events are necessary to implement the techniques). In addition, in some examples, actions or events may be performed concurrently rather than sequentially, such as through multithreading, interrupt handling, or multiple processors.

[0244] In one or more examples, the functions described may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions may be stored on or transmitted through a computer-readable medium as one or more instructions or codes and executed by a hardware-based processing unit. A computer-readable medium may include a computer-readable storage medium corresponding to a tangible medium such as a data storage medium or a communication medium, the communication medium including, for example, any medium that facilitates the transfer of a computer program from one place to another according to a communication protocol. In this manner, a computer-readable medium may generally correspond to (1) a non-temporary tangible computer-readable storage medium, or (2) a communication medium such as a signal or carrier wave. A data storage medium may be any available medium that can be accessed by one or more computers or one or more processors to obtain instructions, codes, and / or data structures for implementing the techniques described in the present disclosure. A computer program product may include a computer-readable medium.

[0245] By way of example and not limitation, such computer-readable storage media may include RAM, ROM, EEPROM, CD-ROM or other optical disk storage, disk storage or other magnetic storage devices, flash memory, or any other medium that can be used to store desired program code in the form of instructions or data structures and can be accessed by a computer. In addition, any connection is appropriately referred to as a computer-readable medium. For example, if a coaxial cable, optical fiber cable, twisted pair, digital subscriber line (DSL) or wireless technology (e.g., infrared, radio and microwave) is used to transmit instructions from a website, server or other remote source, then the coaxial cable, optical fiber cable, twisted pair, DSL or wireless technology (e.g., infrared, radio and microwave) is included in the definition of the medium. However, it should be understood that computer-readable storage media and data storage media do not include connections, carrier waves, signals or other temporary media, but instead relate to non-temporary tangible storage media. As used herein, disks and optical disks include compact disks (CDs), laser optical disks, optical disks, digital versatile disks (DVDs), floppy disks and blue-ray disks, wherein disks usually copy data magnetically, while optical disks use lasers to optically copy data. Combinations of the above should also be included within the scope of computer-readable media.

[0246] Instructions may be executed by one or more processors, such as one or more digital signal processors (DSPs), general-purpose microprocessors, application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other equivalent integrated or discrete logic circuits. Therefore, the terms "processor" and "processing circuitry" as used herein may refer to any of the aforementioned structures or any other structure suitable for implementing the techniques described herein. In addition, in some aspects, the functionality described herein may be provided within dedicated hardware and / or software modules configured for encoding and decoding, or incorporated into a combined codec. In addition, the techniques may be implemented entirely in one or more circuits or logic elements.

[0247] The techniques of the present disclosure may be implemented in a wide variety of devices or apparatuses, including a wireless handset, an integrated circuit (IC), or a set of ICs (e.g., a chipset). Various components, modules, or units are described in the present disclosure to emphasize the functional aspects of a device configured to perform the disclosed techniques, but do not necessarily need to be implemented by different hardware units. Specifically, as described above, the various units may be combined in a codec hardware unit, or a set of interoperable hardware units (including one or more processors as described above) provided in conjunction with appropriate software and / or firmware.

[0248] Various examples have been described. These and other examples are within the scope of the following claims.

Claims

1. A method for decoding video data, the method comprising: Determining samples for generating a DC value to be used for DC intra mode prediction for a current block, wherein determining the samples comprises determining a plurality of samples of at least one of: a non-contiguous sample row having a last sample in the same column as the last column of the current block and a first sample in the same column as the first column of the current block, wherein the non-contiguous sample row is more than one row above the current block, and wherein the non-contiguous sample row includes only the first sample in the same column as the first column of the current block, the last sample in the same column as the last column of the current block, a sample in the non-adjacent sample row between the first sample in the same column as the first column of the current block and the last sample in the same column as the last column of the current block, or a non-contiguous sample column having a last sample in the same row as the last row of the current block and a first sample in the same row as the first row of the current block, wherein the non-contiguous sample column is more than one column to the left of the current block, and wherein the non-contiguous sample column includes only the first sample in the same row as the first row of the current block, the last sample in the same row as the last row of the current block, samples in the non-contiguous sample column between the first sample in the same row as the first row of the current block and the last sample in the same row as the last row of the current block; and Using the DC value, the current block is decoded using DC intra mode prediction.

2. The method according to claim 1, wherein: The current block includes a first block, the non-adjacent sample rows include a first non-adjacent sample row, and the non-adjacent sample columns include a first non-adjacent sample column, and the method further includes: and determining samples to be used for DC intra mode prediction for a second block, wherein determining the samples to be used for DC intra mode prediction for the second block comprises determining a plurality of samples of at least one of: a second non-contiguous row of samples having a first sample in a first column of the second block and having a last sample in the same column as a last column of the second block, wherein the second non-contiguous row of samples is more than three rows above the second block, or a second non-contiguous sample column having a first sample in a first row of the second block and having a last sample in a row that is the same as a last row of the second block, wherein the second non-contiguous sample column is more than three columns to the left of the second block; and The second block is decoded using DC intra mode prediction using the determined samples to be used for DC intra mode prediction for the second block.

3. The method according to claim 1, further comprising: A syntax element is received, the syntax element indicating the number of rows or columns of the non-contiguous sample row above the current block or the number of columns of the non-contiguous sample column to the left of the current block.

4. The method according to claim 1, wherein: The coordinates for the top left sample of the current block are (x0, y0), nW is the width of the current block, and nH is the height of the current block, and MRLIdx indicates the number of rows or columns of the non-adjacent sample rows above the current block or the number of columns of the non-adjacent sample columns to the left of the current block, and the method further includes determining at least one of the following: The non-contiguous sample row with coordinates (x,y0-MRLIdx-1), where x=x0...x0+nW-1, or The non-contiguous sample columns have coordinates (x0-MRLIdx-1,y), where y=y0...y0+nH-1.

5. The method according to claim 1, further comprising: Perform a weighted average of the determined samples, The decoding of the current block comprises: using the weighted average of the determined samples and using DC intra mode prediction to decode the current block.

6. The method according to claim 1, wherein: Decoding includes: generating a prediction block based on the plurality of samples; determining a residual block, the residual block indicating a difference between the current block and the predicted block; as well as The current block is reconstructed based on the residual block and the prediction block.

7. A method for encoding video data, the method comprising: Determining samples for generating a DC value to be used for DC intra mode prediction for a current block, wherein determining the samples comprises determining a plurality of samples of at least one of: a non-contiguous sample row having a last sample in the same column as the last column of the current block and a first sample in the same column as the first column of the current block, wherein the non-contiguous sample row is more than one row above the current block, and wherein the non-contiguous sample row includes only the first sample in the same column as the first column of the current block, the last sample in the same column as the last column of the current block, a sample in the non-adjacent sample row between the first sample in the same column as the first column of the current block and the last sample in the same column as the last column of the current block, or a non-contiguous sample column having a last sample in the same row as the last row of the current block and a first sample in the same row as the first row of the current block, wherein the non-contiguous sample column is more than one column to the left of the current block, and wherein the non-contiguous sample column includes only the first sample in the same row as the first row of the current block, the last sample in the same row as the last row of the current block, samples in the non-contiguous sample column between the first sample in the same row as the first row of the current block and the last sample in the same row as the last row of the current block; and Using the DC value, the current block is encoded using DC intra mode prediction.

8. The method according to claim 7, wherein: The current block includes a first block, the non-adjacent sample rows include a first non-adjacent sample row, and the non-adjacent sample columns include a first non-adjacent sample column, and the method further includes: and determining samples to be used for DC intra mode prediction for a second block, wherein determining the samples to be used for DC intra mode prediction for the second block comprises determining a plurality of samples of at least one of: a second non-contiguous row of samples having a first sample in a first column of the second block and having a last sample in the same column as a last column of the second block, wherein the second non-contiguous row of samples is more than three rows above the second block, or a second non-contiguous sample column having a first sample in a first row of the second block and having a last sample in a row that is the same as a last row of the second block, wherein the second non-contiguous sample column is more than three columns to the left of the second block; and The second block is encoded using DC intra mode prediction using the determined samples to be used for DC intra mode prediction for the second block.

9. The method according to claim 7, further comprising: A syntax element is signaled, the syntax element indicating the number of rows or columns the non-contiguous sample row is above the current block or the number of columns the non-contiguous sample column is to the left of the current block.

10. The method according to claim 7, wherein: The coordinates for the top left sample of the current block are (x0, y0), nW is the width of the current block, and nH is the height of the current block, and MRLIdx indicates the number of rows or columns of the non-adjacent sample rows above the current block or the number of columns of the non-adjacent sample columns to the left of the current block, and the method further includes determining at least one of the following: The non-contiguous sample row with coordinates (x,y0-MRLIdx-1), where x=x0...x0+nW-1, or The non-contiguous sample columns have coordinates (x0-MRLIdx-1,y), where y=y0...y0+nH-1.

11. The method according to claim 7, further comprising: Perform a weighted average of the determined samples, The encoding of the current block comprises: using the weighted average of the determined samples and using DC intra mode prediction to encode the current block.

12. The method according to claim 7, wherein: The encoding includes: generating a prediction block based on the plurality of samples; determining a residual block, the residual block indicating a difference between the current block and the predicted block; and Information indicating the residual block is signaled.

13. A device for decoding video data, the device comprising: a memory configured to store one or more samples of rows and columns non-contiguous to a current block; as well as A processing circuit configured to: determining samples for generating a DC value to be used for DC intra mode prediction for a current block, wherein, to determine the samples, the processing circuit is configured to determine a plurality of samples of at least one of: has a last sample in the same column as the last column of the current block and non-contiguous sample rows of a first sample in the same column as the first column of the current block, wherein the non-adjacent sample row is more than one row above the current block, and wherein, the non-contiguous sample row includes only the first sample in the same column as the first column of the current block, the last sample in the same column as the last column of the current block, samples in the non-contiguous sample row between the first sample in the same column as the first column of the current block and the last sample in the same column as the last column of the current block, or has a last sample in the same row as the last row of the current block and non-adjacent sample columns of a first sample in the same row as the first row of said current block, wherein the non-adjacent sample columns are more than one column to the left of the current block, and wherein, the non-contiguous sample column includes only the first sample in the same row as the first row of the current block, the last sample in the same row as the last row of the current block, and samples in the non-contiguous sample column between the first sample in the same row as the first row of the current block and the last sample in the same row as the last row of the current block; and Using the DC value, the current block is decoded using DC intra mode prediction.

14. The device according to claim 13, wherein: The current block comprises a first block, the non-adjacent sample rows comprise a first non-adjacent sample row, and the non-adjacent sample columns comprise a first non-adjacent sample column, and the processing circuit is configured to: determining samples to be used for DC intra mode prediction for a second block, wherein, to determine the samples to be used for DC intra mode prediction for the second block, the processing circuit is configured to determine a plurality of samples of at least one of: a second non-contiguous row of samples having a first sample in a first column of the second block and having a last sample in the same column as a last column of the second block, wherein the second non-contiguous row of samples is more than three rows above the second block, or a second non-contiguous sample column having a first sample in a first row of the second block and having a last sample in a row that is the same as a last row of the second block, wherein the second non-contiguous sample column is more than three columns to the left of the second block; and The second block is decoded using DC intra mode prediction using the determined samples to be used for DC intra mode prediction for the second block.

15. The apparatus according to claim 13, wherein: The processing circuit is configured to: A syntax element is received, the syntax element indicating the number of rows or columns of the non-contiguous sample row above the current block or the number of columns of the non-contiguous sample column to the left of the current block.

16. The apparatus according to claim 13, wherein: The coordinates for the top left sample of the current block are (x0, y0), nW is the width of the current block, and nH is the height of the current block, and MRLIdx indicates the number of rows or columns of the non-adjacent sample rows above the current block or the number of columns of the non-adjacent sample columns to the left of the current block, and the processing circuit is configured to determine at least one of the following: The non-contiguous sample row with coordinates (x,y0-MRLIdx-1), where x=x0...x0+nW-1, or The non-contiguous sample columns have coordinates (x0-MRLIdx-1,y), where y=y0...y0+nH-1.

17. The apparatus according to claim 13, wherein: The processing circuit is configured to: Perform a weighted average of the determined samples, In order to decode the current block, the processing circuit is configured to: use the weighted average of the determined samples and use DC intra mode prediction to decode the current block.

18. The apparatus of claim 13, wherein: For decoding, the processing circuit is configured to: generating a prediction block based on the plurality of samples; determining a residual block, the residual block indicating a difference between the current block and the predicted block; as well as The current block is reconstructed based on the residual block and the prediction block.

19. The apparatus of claim 13, further comprising: A display configured to display the decoded video data.

20. The apparatus of claim 13, wherein: The device includes one or more of a camera, a computer, a mobile device, or a broadcast receiver device including a set-top box.

21. A device for encoding video data, the device comprising: a memory configured to store one or more samples of rows and columns non-contiguous to a current block; as well as A processing circuit configured to: determining samples for generating a DC value to be used for DC intra mode prediction for a current block, wherein, to determine the samples, the processing circuit is configured to determine a plurality of samples of at least one of: has a last sample in the same column as the last column of the current block and non-contiguous sample rows of a first sample in the same column as the first column of the current block, wherein the non-adjacent sample row is more than one row above the current block, and wherein, the non-contiguous sample row includes only the first sample in the same column as the first column of the current block, the last sample in the same column as the last column of the current block, samples in the non-contiguous sample row between the first sample in the same column as the first column of the current block and the last sample in the same column as the last column of the current block, or has the last sample in the same row as the last row of the current block and non-adjacent sample columns of a first sample in the same row as the first row of said current block, wherein the non-adjacent sample columns are more than one column to the left of the current block, and wherein, the non-contiguous sample column includes only the first sample in the same row as the first row of the current block, the last sample in the same row as the last row of the current block, and samples in the non-contiguous sample column between the first sample in the same row as the first row of the current block and the last sample in the same row as the last row of the current block; and Using the DC value, the current block is encoded using DC intra mode prediction.

22. The apparatus according to claim 21, wherein For encoding, the processing circuit is configured to: generating a prediction block based on the plurality of samples; determining a residual block, the residual block indicating a difference between the current block and the predicted block; as well as Information indicating the residual block is signaled.

23. A non-transitory computer-readable storage medium having stored thereon instructions that, when executed, cause one or more processors to: Determining samples for generating a DC value to be used for DC intra mode prediction for a current block, wherein The instructions that cause the one or more processors to determine the samples include instructions that cause the one or more processors to determine a plurality of samples of at least one of: a non-contiguous sample row having a last sample in the same column as the last column of the current block and a first sample in the same column as the first column of the current block, wherein the non-contiguous sample row is more than one row above the current block, and wherein the non-contiguous sample row includes only the first sample in the same column as the first column of the current block, the last sample in the same column as the last column of the current block, a sample in the non-adjacent sample row between the first sample in the same column as the first column of the current block and the last sample in the same column as the last column of the current block, or a non-contiguous sample column having a last sample in the same row as the last row of the current block and a first sample in the same row as the first row of the current block, wherein the non-contiguous sample column is more than one column to the left of the current block, and wherein the non-contiguous sample column includes only the first sample in the same row as the first row of the current block, the last sample in the same row as the last row of the current block, samples in the non-contiguous sample column between the first sample in the same row as the first row of the current block and the last sample in the same row as the last row of the current block; and Using the DC value, the current block is decoded using DC intra mode prediction.

24. A device for decoding video data, the device comprising: Means for determining samples for generating a DC value to be used for DC intra mode prediction for a current block, wherein the means for determining the samples comprises means for determining a plurality of samples of at least one of: a non-contiguous sample row having a last sample in the same column as the last column of the current block and a first sample in the same column as the first column of the current block, wherein the non-contiguous sample row is more than one row above the current block, and wherein the non-contiguous sample row includes only the first sample in the same column as the first column of the current block, the last sample in the same column as the last column of the current block, a sample in the non-adjacent sample row between the first sample in the same column as the first column of the current block and the last sample in the same column as the last column of the current block, or a non-contiguous sample column having a last sample in the same row as the last row of the current block and a first sample in the same row as the first row of the current block, wherein the non-contiguous sample column is more than one column to the left of the current block, and wherein the non-contiguous sample column includes only the first sample in the same row as the first row of the current block, the last sample in the same row as the last row of the current block, samples in the non-contiguous sample column between the first sample in the same row as the first row of the current block and the last sample in the same row as the last row of the current block; and Means for decoding the current block using DC intra mode prediction using the DC value.

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