DC intra-mode prediction in video coding

Abstract

This disclosure describes examples for determining samples to use for DC intra-mode prediction, such as when the samples are in a row or column that is not immediately above or immediately to the left of the current block. The samples may be aligned with the current block such that the last sample among the samples in the row above the current block is in the same column as the last column of the current block, and such that the last sample among the samples in the column to the left of the current block is in the same row as the last row of the current block.

Description

Claiming priority

[0001] Related Applications

[0001] This application claims priority to U.S. Application No. 16 / 905,352, filed June 18, 2020, which claims the benefit of U.S. Provisional Application No. 62 / 864,422, filed June 20, 2019, and U.S. Provisional Application No. 62 / 866,325, filed June 25, 2019, the entire contents of each of which are incorporated by reference. [Technical field]

[0002]

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

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

[0004]

[0004] Video coding techniques include spatial (intra-picture) prediction and / or temporal (inter-picture) prediction to reduce or remove redundancy inherent in video sequences. In 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 with respect 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 with respect to reference samples in neighboring blocks in the same picture or temporal prediction with respect to reference samples in other reference pictures. A picture may be referred to as a frame, and a reference picture may be referred to as a reference frame. Summary of the Invention

[0005]

[0005] Generally, this 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 video decoder) may utilize one or more samples in a row or column that is not directly adjacent to a current block being coded (e.g., encoded or decoded). This disclosure describes example techniques in which samples in the non-adjacent row or column are aligned with the current block.

[0006]

[0006] As an example, a sample in a non-adjacent row is aligned with the current block when the last sample in the non-adjacent row has the same x-coordinate as the last column of the current block. As an example, a sample in a non-adjacent column is aligned with the current block when the last sample in the non-adjacent column has the same y-coordinate as the last row of the current block. In some examples, the first sample in a non-adjacent row has the same x-coordinate as the first column of the current block and the first sample in a non-adjacent column has the same y-coordinate as the first row of the current block.

[0007]

[0007] There may be improvements in the video coding process by utilizing samples from non-adjacent rows or columns that are aligned with the current block. As an example, in the case of DC intra-mode prediction, samples from non-adjacent rows or columns that are aligned with the current block may generally form a better predicted block (e.g., in terms of smaller residual values) than samples from non-adjacent rows or columns that are not aligned.

[0008]

[0008] Moreover, there may be memory bandwidth benefits. When aligned samples are used for DC intra-mode prediction, the circuit for performing DC intra-mode prediction does not need to fetch the sample at the top left of the current block for DC intra-mode prediction using non-adjacent rows or columns. Since fetching occurs in chunks, not accessing the top left sample may be beneficial in reducing the amount of data read. Thus, in some examples, there may be computational efficiencies due to the video coder accessing fewer samples from memory for DC intra-mode prediction. In this way, the exemplary techniques described in this disclosure provide a technical solution to a technical problem that improves the operation of a video coder and a video coding process with a practical application for applying DC intra-mode prediction on a current block.

[0009]

[0009] In one example, this disclosure describes a method for decoding video data, the method comprising: determining samples to be used for DC intra-mode prediction for a current block, where determining the samples comprises determining a plurality of samples in at least one of non-adjacent rows of samples (wherein the non-adjacent rows of samples are two or more rows above the current block) having a last sample in the same column as the last column of the current block, or non-adjacent columns of samples (wherein the non-adjacent columns of samples are two or more columns to the left of the current block) having a last sample in the same row as the last row of the current block; and decoding the current block using DC intra-mode prediction using the determined samples.

[0010]

[0010] In one example, this disclosure describes a method for encoding video data, the method comprising: determining samples to be used for DC intra-mode prediction for a current block, where determining the samples comprises determining a plurality of samples in at least one of non-adjacent rows of samples (wherein the non-adjacent rows of samples are two or more rows above the current block) having a last sample in the same column as the last column of the current block, or non-adjacent columns of samples (wherein the non-adjacent columns of samples are two or more columns to the left of the current block) having a last sample in the same row as the last row of the current block; and encoding the current block using DC intra-mode prediction using the determined samples.

[0011]

[0011] In one example, the disclosure describes a device for decoding video data, the device comprising: a memory configured to store one or more samples of rows and columns non-adjacent to a current block; and a processing circuit, the processing circuit configured to determine samples to be used for DC intra-mode prediction for the current block, where, to determine the samples, the processing circuit is configured to determine a plurality of samples in at least one of non-adjacent rows of samples (wherein the non-adjacent rows of samples are two or more rows above the current block) having a last sample in the same column as the last column of the current block, or non-adjacent columns of samples (wherein the non-adjacent columns of samples are two or more columns to the left of the current block) having a last sample in the same row as the last row of the current block; and decoding the current block using DC intra-mode prediction using the determined samples.

[0012]

[0012] In one example, the disclosure describes a device for encoding video data, the device comprising: a memory configured to store one or more samples of rows and columns non-adjacent to a current block; and a processing circuit, the processing circuit configured to determine samples to be used for DC intra-mode prediction for the current block, where, to determine the samples, the processing circuit is configured to determine a plurality of samples in at least one of a non-adjacent row of samples (wherein the non-adjacent row of samples is two or more rows above the current block) having a last sample in the same column as the last column of the current block, or a non-adjacent column of samples (wherein the non-adjacent column of samples is two or more columns to the left of the current block) having a last sample in the same row as the last row of the current block; and encoding the current block using DC intra-mode prediction using the determined samples.

[0013]

[0013] In one example, the disclosure describes a computer-readable storage medium having stored thereon instructions that, when executed, cause one or more processors to determine samples to be used for DC intra-mode prediction for a current block, where the instructions causing the one or more processors to determine the samples include instructions that cause the one or more processors to determine a plurality of samples in at least one of non-adjacent rows of samples (wherein the non-adjacent rows of samples are two or more rows up of the current block) having a last sample that is in the same column as the last column of the current block, or non-adjacent columns of samples (wherein the non-adjacent columns of samples are two or more columns to the left of the current block) having a last sample that is in the same row as the last row of the current block; and decoding the current block using DC intra-mode prediction using the determined samples.

[0014]

[0014] In one example, the disclosure describes a device for decoding video data, the device comprising: means for determining samples to be used for DC intra-mode prediction for a current block, where the means for determining samples comprises means for determining a plurality of samples in at least one of non-adjacent rows of samples (wherein the non-adjacent rows of samples are two or more rows above the current block) having a last sample in the same column as the last column of the current block, or samples in non-adjacent columns of samples (wherein the non-adjacent columns of samples are two or more columns to the left of the current block) having a 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 determined samples.

[0015] The details of one or more examples are set forth in the accompanying drawings and the description below. Other features, objects, and advantages will become apparent from the description, drawings, and claims. [Brief description of the drawings]

[0016] [Figure 1]

[0016] FIG. 1 is a block diagram illustrating an example video encoding and decoding system in which the techniques of this disclosure may be implemented. [Figure 2A]

[0017] 1 is a conceptual diagram illustrating an exemplary Quad Tree Binary Tree (QTBT) structure. [Figure 2B] A conceptual diagram showing a corresponding coding tree unit (CTU). [Diagram 3]

[0018] 1 is a block diagram illustrating an example video encoder that may implement the techniques of this disclosure. [Figure 4]

[0019] 1 is a block diagram illustrating an example video decoder that may implement the techniques of this disclosure. [Diagram 5]

[0020] A conceptual diagram showing the direction of intra prediction, with the arrow pointing towards the reference sample. [Figure 6]

[0021] FIG. 1 is a conceptual diagram showing an example of an 8×4 rectangular block that is intra-predicted. [Figure 7A]

[0022] FIG. 13 is a conceptual diagram illustrating the mode mapping process for off-diagonal modes. [Figure 7B] FIG. 13 is a conceptual diagram illustrating the mode mapping process for off-diagonal modes. [Figure 7C] FIG. 13 is a conceptual diagram illustrating the mode mapping process for off-diagonal modes. [Figure 8]

[0023] Conceptual diagram showing 65 angle modes plus wide angle (-1 to -10 and 67 to 76). [Figure 9]

[0024] Conceptual diagram showing wide angles (-1 to -14 and 67 to 80) beyond modes 2 and 6, for a total of 93 angle modes. [Figure 10]

[0025] FIG. 13 is a diagram of a mapping table for determining angle angles for intra prediction. [Figure 11]

[0026] 1 is a conceptual diagram illustrating reference samples from multiple reference lines that may be used for intra prediction of a coding block. [Figure 12]

[0027] Conceptual diagram showing reference samples from directly adjacent rows and columns. [Figure 13]

[0028] A conceptual diagram illustrating reference samples from non-adjacent rows and columns that are not aligned with the current block. [Figure 14] A conceptual diagram illustrating reference samples from non-adjacent rows and columns that are not aligned with the current block. [Figure 15] A conceptual diagram illustrating reference samples from non-adjacent rows and columns that are not aligned with the current block. [Figure 16]

[0029] A conceptual diagram illustrating reference samples from non-adjacent rows and columns that are not aligned with the current block. [Figure 17] A conceptual diagram showing reference samples from non-adjacent rows and columns that are aligned with the current block. [Figure 18] A conceptual diagram showing reference samples from non-adjacent rows and columns that are aligned with the current block. [Figure 19] A conceptual diagram showing reference samples from non-adjacent rows and columns that are aligned with the current block. [Figure 20]

[0030] 1 is a flow chart illustrating an example method for encoding video data. [Figure 21]

[0031] 4 is a flow chart illustrating an example method for decoding video data. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017]

[0032] In video coding, a video encoder generates a predictive block for a current block and determines a residual block (e.g., a difference) between the current block and the predictive block. The video encoder signals information indicating the residual block and prediction mode information indicating how the video encoder generated the predictive block. A video decoder receives the information of the residual block and the prediction mode information. The video decoder generates the predictive block based on the prediction mode information such that the predictive block generated by the video decoder is the same as the predictive block generated by the video encoder. The video decoder adds the predictive block to the residual block to reconstruct the current block.

[0018]

[0033] An example of a prediction mode is a DC intra-prediction mode. In the DC intra-prediction mode, a video coder (e.g., a video encoder and / or a video decoder) generates a predictive block using samples in the same picture as the current block. For example, in the DC intra-prediction mode, the video coder may utilize samples in adjacent rows (e.g., the row immediately above) and / or adjacent columns (e.g., the column immediately to the left) of the current block to generate a predictive block.

[0019]

[0034] In some examples, the DC intra prediction mode utilizes samples from non-adjacent columns or rows. As an example, the non-adjacent rows of samples are two or more rows above the current block, and the non-adjacent columns of samples are two or more columns to the left of the current block. As another example, the non-adjacent rows of samples are four or more rows above the current block, and the non-adjacent columns of samples are four or more columns to the left of the current block. As another example, the non-adjacent rows of samples are three or more rows above the current block, and the non-adjacent column samples are three or more columns to the left of the current block.

[0020]

[0035] The video encoder may signal information received by the video decoder indicating which rows and / or columns should be used for DC intra prediction. For example, the information may indicate whether samples in rows and / or columns adjacent to the current block should be used, whether samples in rows and / or columns one row or one column away from the current block (e.g., one example of non-adjacent rows or columns) should be used, or whether samples in rows and / or columns three rows or three columns away from the current block (e.g., another example of non-adjacent rows or columns) should 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 should be used, whether samples in rows and / or columns one row or one column away from the current block (e.g., one example of non-adjacent rows or columns) should be used, or whether samples in rows and / or columns two rows or two columns away from the current block (e.g., another example of non-adjacent rows or columns) should be used for DC intra prediction.

[0021]

[0036] This disclosure describes example techniques for determining which samples in non-adjacent rows and / or columns should be utilized to generate a predictive block. The samples in 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 a non-adjacent row that may be utilized 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 bottom sample) of the samples in a non-adjacent column that may be utilized for DC intra prediction may be aligned with the last row (e.g., the bottom row) of the current block. In some examples, the first sample (e.g., the leftmost sample) of the samples in a non-adjacent row that may be utilized 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 top sample) of the samples in a non-adjacent column that may be utilized for DC intra prediction may be aligned with the first row (e.g., the top row) of the current block.

[0022]

[0037] In one or more examples, utilizing samples from non-adjacent rows or columns aligned with the current block may result in a better predicted block (e.g., in terms of having smaller residual values ​​in the residual block) compared to utilizing samples from non-adjacent rows or columns not aligned with the current block. Also, in some examples, the circuitry of the video coder used for DC intra prediction may not need to access samples located above and to the left of the current block, which reduces the amount of data read. In this manner, the exemplary technique may improve the overall operation of the video coder and improve the video coding process. For example, the exemplary technique provides a practical application for improving the operation of video encoders and video decoders when performing DC intra prediction of the current block.

[0023]

[0038] 1 is a block diagram illustrating an example video encoding and decoding system 100 that may implement the techniques of this disclosure. The techniques of this disclosure are generally directed to coding (encoding and / or decoding) video data. In general, video data includes any data for processing video. Thus, video data may include raw uncoded video, coded video, decoded (e.g., reconstructed) video, and video metadata, such as signaling data.

[0024]

[0039] 1, system 100 includes a source device 102 that provides encoded video data to be decoded and displayed by a destination device 116, in this example. In particular, source device 102 provides the video data to destination device 116 via a computer-readable medium 110. Source device 102 and destination device 116 may comprise any of a wide range of devices, including desktop computers, notebook (i.e., laptop) computers, tablet computers, set-top boxes, telephone handsets such as smartphones, televisions, cameras, display devices, digital media players, video game consoles, video streaming devices, and the like. In some cases, source device 102 and destination device 116 may be equipped for wireless communication and thus may be referred to as wireless communication devices.

[0025]

[0040] In the example of FIG. 1, source device 102 includes a video source 104, a memory 106, a video encoder 200, and an output interface 108. Destination device 116 includes an input interface 122, a video decoder 300, a memory 120, and a display device 118. According to this disclosure, the video encoder 200 of source device 102 and the video decoder 300 of destination device 116 may be configured to apply techniques for determining which samples to use for DC intra-mode prediction, such as when the samples are in non-adjacent rows or columns and are aligned with a current block being coded (e.g., encoded or decoded). Thus, source device 102 represents an example of a video encoding device, and destination device 116 represents an example of a video decoding device. In other examples, source and destination devices may include other components or arrangements. For example, source device 102 may receive video data from an external video source, such as an external camera. Similarly, destination device 116 may interface with an external display device rather than including an integrated display device.

[0026]

[0041] The system 100 shown in FIG. 1 is only an example. In general, any digital video encoding and / or decoding device may implement techniques for determining which samples to use for DC intra-mode prediction, such as when the samples are in non-adjacent rows or columns and aligned with the current block being coded (e.g., encoded or decoded). The source device 102 and the destination device 116 are only examples of coding devices, such as when the source device 102 generates coded video data for transmission to the destination device 116. This disclosure refers to a "coding" device as a device that performs coding (encoding and / or decoding) of data. Thus, the video encoder 200 and the video decoder 300 represent examples of coding devices, and in particular, video encoders and video decoders, respectively. In some examples, the devices 102, 116 may operate substantially symmetrically, 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 device 102 and video device 116, for example, video streaming, video playback, video broadcasting, or video telephony.

[0027]

[0042] Generally, the video source 104 represents a source of video data (i.e., raw, unencoded video data) and provides a continuous series of pictures (also called “frames”) 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 video camera, a video archive containing previously captured raw video, and / or a video feed interface for receiving video from a video content provider. As a further alternative, the video source 104 may generate computer graphics-based data or a combination of live, archival, and computer-generated video as the source video. In each case, the video encoder 200 encodes the captured, pre-captured, or computer-generated video data. The video encoder 200 may reorder the pictures from a receiving order (sometimes called a “display order”) into a coding order for coding. The video encoder 200 may generate a bitstream including the encoded video data. The source device 102 may then output the encoded video data via the output interface 108 onto a computer-readable medium 110 for receipt and / or retrieval by, for example, an input interface 122 of the destination device 116 .

[0028]

[0043] 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 memory 106, 120 may store raw video data, e.g., raw video from the video source 104 and raw decoded video data from the video decoder 300. Additionally or alternatively, the memory 106, 120 may store software instructions executable by, e.g., the video encoder 200 and the video decoder 300, respectively. Although shown separately in this example, the video encoder 200 and the video decoder 300, it should be understood that the video encoder 200 and the video decoder 300 may also include internal memory for functionally similar or equivalent purposes. Additionally, the memory 106, 120 may store encoded video data, e.g., output from the video encoder 200 and input to the video decoder 300. In some examples, portions of the memory 106, 120 may be allocated as one or more video buffers, e.g., to store raw decoded and / or encoded video data.

[0029]

[0044] The computer-readable medium 110 may represent any type of medium or device capable of transporting 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 for enabling the source device 102 to transmit the encoded video data directly 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 a transmission signal including the encoded video data, and the input interface 122 may demodulate a received transmission signal according to a communication standard such as a wireless communication protocol. The communication medium may comprise any wireless or wired communication medium, such as a radio frequency (RF) spectrum or one or more physical transmission lines. The communication medium may form part of a packet-based network, such as a local area network, a wide area network, or a global network such as the Internet. The communication medium may include routers, switches, base stations, or any other equipment that may be useful to facilitate communication from the source device 102 to the destination device 116.

[0030]

[0045] 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.

[0031]

[0046] In some examples, source device 102 may output the encoded video data to a file server 114 or another intermediate storage device, which 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 download.

[0032]

[0047] The file server 114 may be any type of server device capable of storing encoded video data and transmitting 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 File Transfer Protocol (FTP) or File Delivery over Unidirectional Transport (FLUTE) protocol), a content delivery network (CDN) device, a Hypertext Transfer Protocol (HTTP) server, a Multimedia Broadcast Multicast Service (MBMS) or enhanced MBMS (eMBMS) server, and / or a network attached storage (NAS) device. The file server 114 may additionally or alternatively implement one or more HTTP streaming protocols, such as Dynamic Adaptive Streaming over HTTP (DASH), HTTP Live Streaming (HLS), Real Time Streaming Protocol (RTSP), HTTP Dynamic Streaming, etc.

[0033]

[0048] 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, that is 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 described above for retrieving or receiving media data from the file server 114, or other such protocols for retrieving media data.

[0034]

[0049] The output interface 108 and the input interface 122 may represent a wireless transmitter / receiver, a modem, a wired networking component (e.g., an Ethernet card), a wireless communication component operating according to any of the various IEEE 802.11 standards, or other physical components. In examples in which the output interface 108 and the input interface 122 comprise wireless components, the output interface 108 and the input interface 122 may be configured to transfer data, such as encoded video data, according to a cellular communication standard, such as 4G, 4G-LTE (Long Term Evolution), LTE Advanced, 5G, etc. In some examples in which the output interface 108 comprises a wireless transmitter, the output interface 108 and the input interface 122 may be configured to transfer data, such as encoded video data, according to other wireless standards, such as the IEEE 802.11 specification, the IEEE 802.15 specification (e.g., ZigBee), the Bluetooth standard, etc. In some examples, the source device 102 and / or the destination device 116 may include respective system-on-chip (SoC) devices. For example, the source device 102 may include a SoC device for performing functions attributable to the video encoder 200 and / or the output interface 108, and the destination device 116 may include a SoC device for performing functions attributable to the video decoder 300 and / or the input interface 122.

[0035]

[0050] The techniques of this disclosure may be applied to video coding supporting any of a variety of multimedia applications, such as over-the-air television broadcast, cable television transmission, satellite television transmission, Internet streaming video transmission such as Dynamic Adaptive Streaming over HTTP (DASH), digital video encoded on a data storage medium, decoding of digital video stored on a data storage medium, or other applications.

[0036]

[0051] 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 defined by the video encoder 200 that is also used by the video decoder 300, such as syntax elements having values ​​that describe characteristics and / or processing of video blocks or other coded units (e.g., slices, pictures, groups of pictures, sequences, etc.). The display device 118 displays decoded pictures of the decoded video data to a user. The display device 118 may 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.

[0037]

[0052] 1, in some examples, the video encoder 200 and the video decoder 300 may each be integrated with an audio encoder and / or an audio decoder and may include an appropriate MUX-DEMUX unit, or other hardware and / or software, to handle multiplexed streams that include both audio and video in a common data stream. Where applicable, the MUX-DEMUX unit may conform to the ITU H.223 multiplexer protocol, or other protocols such as the User Datagram Protocol (UDP).

[0038]

[0053] The video encoder 200 and the video decoder 300 may each be implemented as any of a variety of suitable encoder and / or decoder circuits, or any combination thereof, 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, etc. When the techniques are implemented partially in software, a device may store instructions for the software on a suitable non-transitory computer-readable medium and execute the instructions in hardware using one or more processors to implement the techniques of this disclosure. Each of the video encoder 200 and the video decoder 300 may be included in one or more encoders or decoders, any of which may be integrated as part of a combined encoder / decoder (codec) in the respective device. The device including the video encoder 200 and / or the video decoder 300 may comprise an integrated circuit, a microprocessor, and / or a wireless communication device such as a cellular phone.

[0039]

[0054] The following describes some exemplary video coding standards, including 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 Multiview Video Coding (MVC) extensions.

[0040]

[0055] A state-of-the-art video coding standard, namely High Efficiency Video Coding (HEVC), was finalized by the Joint Collaboration Team on Video Coding (JCT-VC) between the ITU-T Video Coding Expert Group (VCEG) and the ISO / IEC Motion Picture Expert Group (MPEG) in April 2013. The Joint Video Expert Team (JVET), a collaborative team formed by MPEG and the VCEG in ITU-T Study Group 16, is working on a new video coding standard that will be known as Versatile Video Coding (VVC). The main objective of VVC is to provide a significant improvement in compression performance over the existing HEVC standard that will aid in the deployment of higher quality video services and emerging applications, such as 360° omnidirectional immersive multimedia and high dynamic range (HDR) video. Development of the VVC standard is expected to be completed in 2020. A recent draft of the VVC standard is described in Bross et al., “Versatile Video Coding (Draft 5),” Joint Video Experts Team (JVET) of ITU-T SG16 WP3 and ISO / IEC JTC1 / SC29 / WG11, 14th Meeting, Geneva, Switzerland, March 19-27, 2019, JVET-N1008-v8 (hereafter “VVC Draft 5”), available at http: / / phenix.it-sudparis.eu / jvet / doc_end_user / documents / 13_Marrakech / wg11 / JVET-N1001-v8.zip.

[0041]

[0056] Video encoder 200 and video decoder 300 may operate according to a video coding standard, such as ITU-T H.265, also known as High Efficiency Video Coding (HEVC), or extensions thereof, such as multiview and / or scalable video coding extensions. Alternatively, video encoder 200 and video decoder 300 may operate according to other proprietary or industry standards, such as ITU-T H.266, also known as Versatile Video Coding (VVC). A more recent draft of the VVC standard is set forth in Bross et al., "Versatile Video Coding (Draft 9)," Joint Video Experts Team (JVET) of ITU-T SG16 WP3 and ISO / IEC JTC1 / SC29 / WG11, 18th Meeting, Teleconference, April 15-24, 2020, JVET-R2001-v8 (hereinafter, "VVC Draft 9"). However, the techniques of this disclosure are not limited to any particular coding standard.

[0042]

[0057] Generally, the video encoder 200 and the video decoder 300 may perform block-based coding of pictures. The term “block” generally refers to a structure that includes data to be processed (e.g., encoded, decoded, or otherwise used in an encoding and / or decoding process). For example, a block may include a two-dimensional matrix of samples of luminance and / or chrominance data. Generally, the video encoder 200 and the video decoder 300 may code video data represented in a YUV (e.g., Y, Cb, Cr) format. That is, rather than coding red, green, and blue (RGB) data for a sample of a picture, the video encoder 200 and the video decoder 300 may code a luminance component and a chrominance component, where the chrominance component may include both red and blue hues of chrominance components. In some examples, the video encoder 200 converts received RGB format data to a YUV representation prior to encoding, and the video decoder 300 converts the YUV representation to an RGB format. Alternatively, pre-processing and post-processing units (not shown) may perform these conversions.

[0043]

[0058] This disclosure may generally refer to coding (e.g., encoding and decoding) a picture to include processes of encoding or decoding data for a picture. Similarly, this disclosure may refer to coding a block of a picture to include processes of encoding or decoding data for the block, e.g., predictive and / or residual coding. A coded video bitstream generally includes a series of values ​​for syntax elements that represent coding decisions (e.g., coding modes) and partitioning of a picture into blocks. Thus, references to coding a picture or a block should be understood generally as coding values ​​for the syntax elements that form the picture or block.

[0044]

[0059] HEVC defines various blocks, including coding units (CUs), prediction units (PUs), and transform units (TUs). According to HEVC, a video coder (such as video encoder 200) partitions coding tree units (CTUs) into CUs according to a quadtree structure. That is, the video coder partitions CTUs and CUs into four equal non-overlapping squares, and each node of the quadtree has either zero or four child nodes. A node without children may be called a "leaf node", and a CU of such a leaf node may include one or more PUs and / or one or more TUs. The video coder may further partition PUs and TUs. For example, in HEVC, a residual quadtree (RQT) represents the partition of TUs. In HEVC, a PU represents inter-predicted data, and a TU represents residual data. An intra-predicted CU includes intra-prediction information, such as an intra-mode indication.

[0045]

[0060] 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 coder (such as the video encoder 200) partitions a picture into multiple coding tree units (CTUs). The video encoder 200 may partition the CTUs according to a tree structure, such as a quad-tree binary tree (QTBT) structure or a multi-type tree (MTT) structure. The QTBT structure eliminates the concept of multiple partition types, such as the separation between CUs, PUs, and TUs in HEVC. The QTBT structure includes two levels, a first level partitioned according to a quad-tree partition and a second level partitioned according to a binary tree partition. The root node of the QTBT structure corresponds to a CTU. The leaf nodes of the binary tree correspond to coding units (CUs).

[0046]

[0061] In the MTT partition structure, blocks may be partitioned using quad tree (QT) partitions, binary tree (BT) partitions, and one or more types of triple tree (TT) partitions. Triple tree partitions are partitions in which a block is split into three sub-blocks. In some examples, triple tree partitions split a block into three sub-blocks without splitting the original block through the center. The partition types in MTT (e.g., QT, BT, and TT) may be symmetric or asymmetric.

[0047]

[0062] 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 luminance and chrominance components, and 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 luminance component and another QTBT / MTT structure for both chrominance components (or two QTBT / MTT structures for each chrominance component).

[0048]

[0063] Video encoder 200 and video decoder 300 may be configured to use quadtree partitioning, QTBT partitioning, MTT partitioning, or other partition structures in accordance with HEVC. For purposes of illustration, the description of the techniques of this disclosure is presented with respect to QTBT partitioning. However, it should be understood that the techniques of this disclosure may also be applied to video coders configured to use quadtree partitioning, or other types of partitioning as well.

[0049]

[0064] This disclosure may use "NxN" and "N by N", e.g., 16x16 samples or 16 by 16 samples, interchangeably to refer to sample dimensions of a block (such as a CU or other video block) in terms of vertical and horizontal dimensions. Generally, a 16x16 CU has 16 samples in the vertical direction (y=16) and 16 samples in the horizontal direction (x=16). Similarly, an NxN CU generally has N samples in the vertical direction and N samples in the horizontal direction, where N represents a non-negative integer value. Samples in a CU may be arranged in rows and columns. Moreover, a CU does not necessarily have to have the same number of samples in the horizontal direction as in the vertical direction. For example, a CU may comprise NxM samples, where M is not necessarily equal to N.

[0050]

[0065] The video encoder 200 encodes video data for a CU that represents prediction and / or residual information, as well as other information. The prediction information indicates how the CU should be predicted to form a predictive block for the CU. The residual information generally represents sample-by-sample differences between samples of the CU prior to encoding and the predictive block.

[0051]

[0066] To predict a CU, the video encoder 200 may generally form a predictive block for the CU through inter-prediction or intra-prediction. Inter-prediction generally refers to predicting a CU from data of a previously coded picture, while intra-prediction generally refers to predicting a CU from previously coded data of the same picture. To perform inter-prediction, the video encoder 200 may generate a predictive block using one or more motion vectors. The video encoder 200 may generally perform a motion search to identify a reference block that closely matches the CU, for example, with respect to the difference between the CU and the reference block. The video encoder 200 may calculate a difference metric using a sum of absolute differences (SAD), sum of squared differences (SSD), mean absolute difference (MAD), mean squared difference (MSD), or other such difference calculation to determine whether the reference block closely matches the current CU. In some examples, the video encoder 200 may predict the current CU using unidirectional or bidirectional prediction.

[0052]

[0067] VVC may also provide an affine motion compensation mode, which may be considered an inter prediction mode. In an affine motion compensation mode, video encoder 200 may determine two or more motion vectors that represent non-translational motion, such as zooming in or out, rotation, perspective motion, or other irregular motion types.

[0053]

[0068] To perform intra prediction, video encoder 200 may select an intra prediction mode to generate a predictive block. VVC may provide 67 intra prediction modes, including various directional modes, as well as planar and DC modes. In general, video encoder 200 selects an intra prediction mode that describes neighboring samples relative to a current block (e.g., a block of a CU) from which samples of the current block should be predicted. Such samples may generally be above, to the left of, or to the left of the current block in the same picture as the current block, assuming that video encoder 200 codes CTUs and CUs in raster scan order (left to right, top to bottom).

[0054]

[0069] Video encoder 200 encodes data representing a prediction mode for the current block. For example, in an inter prediction mode, video encoder 200 may encode data representing which of various available inter prediction modes is used, as well as motion information for the corresponding mode. For example, in unidirectional or bidirectional inter prediction, video encoder 200 may encode motion vectors using advanced motion vector prediction (AMVP) or merge mode. Video encoder 200 may use similar modes to encode motion vectors for affine motion compensation modes.

[0055]

[0070] Following prediction, such as intra- 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 sample-by-sample differences between the block and a predictive block for the block 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 the 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. Additionally, the video encoder 200 may apply a secondary transform, such as a mode-dependent non-separable secondary transform (MDNSST), a signal-dependent transform, a Karhunen-Loeve transform (KLT), etc., following the first transform. The video encoder 200 produces transform coefficients following application of the one or more transforms.

[0056]

[0071] As mentioned above, following 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 a transform coefficient is quantized to possibly reduce the amount of data used to represent that coefficient, providing further compression. By performing a quantization process, the video encoder 200 may reduce the bit depth associated with some or all of the coefficients. For example, the video encoder 200 may round 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.

[0057]

[0072] Following quantization, the video encoder 200 may scan the transform coefficients to produce a one-dimensional vector from a two-dimensional matrix including the quantized transform coefficients. The scan may be designed to place coefficients of higher energy (and therefore lower frequency) at the front of the vector and transform coefficients of lower energy (and therefore higher frequency) at the rear of the vector. In some examples, the video encoder 200 may utilize a predefined scan order to scan the quantized transform coefficients to produce a serialized vector, and then entropy code the quantized transform coefficients of the vector. In other examples, the video encoder 200 may perform an adaptive scan. After scanning the quantized transform coefficients to form a one-dimensional vector, the video encoder 200 may entropy code the one-dimensional vector, for example, according to context-adaptive binary arithmetic coding (CABAC). The video encoder 200 may also entropy code values ​​for syntax elements describing metadata associated with the encoded video data for use by the video decoder 300 in decoding the video data.

[0058]

[0073] To implement CABAC, the video encoder 200 may assign a context in a context model to a symbol to be transmitted. The context may relate, for example, to whether neighboring values ​​of the symbol are zero-valued or not. The probability determination may be based on the context assigned to the symbol.

[0059]

[0074] Video encoder 200 may further generate syntax data, such as block-based syntax data, picture-based syntax data, and sequence-based syntax data, for video decoder 300, e.g., in a picture header, block header, slice header, or other syntax data, such as a sequence parameter set (SPS), a picture parameter set (PPS), or a video parameter set (VPS). Video decoder 300 may similarly decode such syntax data to determine how to decode corresponding video data.

[0060]

[0075] In this manner, video encoder 200 may generate a bitstream including syntax elements that describe the encoded video data, e.g., partitions of a picture into blocks (e.g., CUs) and predictive and / or residual information for the blocks. Finally, video decoder 300 may receive the bitstream and decode the encoded video data.

[0061]

[0076] In general, the video decoder 300 performs an inverse process to that performed by the video encoder 200 to decode the encoded video data of the bitstream. For example, the video decoder 300 may decode values ​​for syntax elements of the bitstream using CABAC in a manner that is inverse to, but substantially similar to, the CABAC encoding process of the video encoder 200. The syntax elements may define partition information of a picture into CTUs and partitioning of each CTU according to a corresponding partition structure, such as a QTBT structure, to define the CUs of the CTU. The syntax elements may further define prediction and residual information for blocks (e.g., CUs) of video data.

[0062]

[0077] The residual information may be represented, for example, by quantized transform coefficients. The video decoder 300 may dequantize and inverse transform the quantized transform coefficients of the block to reconstruct a residual block for the block. The video decoder 300 uses the signaled prediction mode (intra- or inter-prediction) and associated prediction information (e.g., motion information for inter-prediction) to form a predictive block for the block. The video decoder 300 may then combine (sample-by-sample) the predictive block and the residual block to reconstruct the original block. The video decoder 300 may perform additional processing, such as performing a deblocking process to reduce visual artifacts along block boundaries.

[0063]

[0078] As described in more detail below, example techniques described in this disclosure relate to intra prediction, such as DC intra mode prediction. In one or more examples, a video coder (e.g., video encoder 200 or video decoder 300) may be configured to determine samples to use for DC intra mode prediction for a current block. For example, to determine the samples, the video coder may be configured to determine a number of samples in non-adjacent rows with a last sample in the non-adjacent row being in the same column as the last column of the current block, or a number of samples in non-adjacent columns with a last sample in the non-adjacent column being in the same row as the last row of the current block. In some examples, the multiple samples in non-adjacent rows or columns may have a first sample in a non-adjacent row being in the same column as the first column of the current block, or a first sample in a non-adjacent column being in the same row as the first row of the current block. In this way, samples used for DC intra mode prediction are aligned with the current block even if the samples are in non-adjacent rows or columns. The video coder may code (e.g., encode or decode) the current block using DC intra mode prediction using the determined samples.

[0064]

[0079] This disclosure may generally refer to "signaling" certain information, such as a syntax element. The term "signaling" may generally refer to communication of values ​​for syntax elements and / or other data used to decode encoded video data. That is, video encoder 200 may signal values ​​for syntax elements in a bitstream. Generally, signaling refers to generating values ​​in a bitstream. As described above, source device 102 may transport the bitstream to destination device 116 in substantially real-time or may transport the bitstream to destination device 116 in non-real-time, such as may be done when storing syntax elements in storage device 112 for later retrieval by destination device 116.

[0065]

[0080] 2A and 2B are conceptual diagrams illustrating an exemplary quad-tree binary tree (QTBT) structure 130 and corresponding coding tree unit (CTU) 132. Solid lines represent quad-tree splitting, and dotted lines indicate binary tree splitting. At each split (i.e., non-leaf) node of the binary tree, one flag is signaled to indicate which splitting type (i.e., horizontal or vertical) is used, where in this example, 0 indicates horizontal splitting and 1 indicates vertical splitting. In quad-tree splitting, there is no need to indicate the splitting type, since the quad-tree node splits the block horizontally and vertically into four sub-blocks with equal size. Thus, video encoder 200 may encode, and video decoder 300 may decode, syntax elements (such as splitting information) for the region tree level (i.e., solid lines) of QTBT structure 130 and syntax elements (such as splitting information) for the prediction tree level (i.e., dashed lines) of QTBT structure 130. Video encoder 200 may encode, and video decoder 300 may decode, video data, such as prediction and transform data, for CUs represented by terminal leaf nodes of QTBT structure 130.

[0066]

[0081] 2B may be associated with parameters that define the sizes of blocks corresponding to nodes of the QTBT structure 130 at the first and second levels. These parameters may include a CTU size (representing the size of the CTU 132 in a sample), a minimum quad tree size (MinQTSize representing the minimum allowable quad tree leaf node size), a maximum binary tree size (MaxBTSize representing the maximum allowable binary tree root node size), a maximum binary tree depth (MaxBTDepth representing the maximum allowable binary tree depth), and a minimum binary tree size (MinBTSize representing the minimum allowable binary tree leaf node size).

[0067]

[0082] 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 partitioned according to a quadtree partition. That is, the nodes at the first level are either leaf nodes (without child nodes) or have four child nodes. The example QTBT structure 130 represents such a node including a parent node and a child node with solid lines for branching. If the nodes at the first level are not larger than the maximum allowed binary tree root node size (MaxBTSize), the nodes may be further partitioned by their respective binary trees. The binary tree splitting of one node may be repeated until the nodes resulting from the split reach the minimum allowed binary tree leaf node size (MinBTSize) or the maximum allowed binary tree depth (MaxBTDepth). The example QTBT structure 130 represents such a node with dashed lines for branching. The binary tree leaf nodes are called coding units (CUs), and the CUs are used for prediction (e.g., intra-picture or inter-picture prediction) and transformation without further partitioning. As explained above, a CU may also be referred to as a "video block" or a "block."

[0068]

[0083] In one example of a QTBT partitioning structure, the CTU size is set as 128x128 (luma samples and two corresponding 64x64 chroma samples), MinQTSize is set as 16x16, MaxBTSize is set as 64x64, MinBTSize is set as 4 (for both width and height), and MaxBTDepth is set as 4. Quad tree partitioning is first applied to the CTU to generate quad tree leaf nodes. The quad tree leaf nodes can have sizes from 16x16 (i.e., MinQTSize) to 128x128 (i.e., CTU size). If the leaf quad tree node is 128x128, it is not further split by the binary tree since the size exceeds MaxBTSize (i.e., 64x64 in this example). Otherwise, the leaf quad tree node is further partitioned by the binary tree. Therefore, the quad tree leaf node is also the root node for the binary tree and has the binary tree depth as 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 implies that no further horizontal splitting is allowed. Similarly, a binary tree node having a height equal to MinBTSize implies that no further vertical splitting is allowed for that binary tree node. As mentioned above, the leaf node of the binary tree is called a CU and is further processed according to the prediction and transformation without further partitioning.

[0069]

[0084] 3 is a block diagram illustrating an example video encoder 200 that may implement the techniques of this disclosure. FIG. 3 is provided for illustrative purposes and should not be considered as limiting the techniques broadly illustrated and described in this disclosure. For illustrative purposes, this disclosure describes 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 this disclosure are not limited to these video coding standards and are generally applicable to video encoding and decoding.

[0070]

[0085] In the example of Figure 3, 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 or all of the video data memory 230, the mode selection unit 202, the 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 DPB 218, and an entropy coding unit 220 may be implemented in one or more processors or processing circuits. Moreover, the video encoder 200 may include additional or alternative processors or processing circuits for performing these and other functions.

[0071]

[0086] 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 stored in the video data memory 230, for example, from the video source 104 (FIG. 1). The DPB 218 may act as a reference picture memory that stores reference video data for use in predicting subsequent video data by the video encoder 200. The video data memory 230 and the DPB 218 may be formed by any of a variety of memory devices, such as synchronous dynamic random access memory (DRAM), including DRAM (SDRAM), magnetoresistive RAM (MRAM), resistive RAM (RRAM), or other types of memory devices. The video data memory 230 and the DPB 218 may be provided by the same memory device or separate memory devices. In various examples, the video data memory 230 may be on-chip with the other components of the video encoder 200, as shown, or off-chip relative to those components.

[0072]

[0087] In this disclosure, references to video data memory 230 should not be construed as limited to memory internal to video encoder 200 unless specifically so described, or to memory external to video encoder 200 unless specifically so described. Instead, references to video data memory 230 should be understood as a reference memory that stores video data that video encoder 200 receives for encoding (e.g., video data for a current block to be encoded). Memory 106 of FIG. 1 may also provide temporary storage of outputs from various units of video encoder 200.

[0073]

[0088] The various units in FIG. 3 are shown to aid in understanding the operations performed by the video encoder 200. The units may be implemented as fixed-function circuits, programmable circuits, or a combination thereof. A fixed-function circuit refers to a circuit that provides a specific function and is preset with respect to the operations that may be performed. A programmable circuit refers to a circuit that may be programmed to perform various tasks and to provide flexible functionality in the operations that may 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 software or firmware instructions. A fixed-function circuit may execute software instructions (e.g., to receive parameters or output parameters), but the type of operations that the fixed-function circuit performs is generally invariant. In some examples, one or more of the units may be separate circuit blocks (fixed function or programmable), and in some examples, one or more of the units may be an integrated circuit.

[0074]

[0089] The video encoder 200 may include an arithmetic logic unit (ALU), a basic functional unit (EFU), a programmable core formed of digital circuits, analog circuits, and / or programmable circuits. In examples in which the operations of the video encoder 200 are implemented using software executed by programmable circuits, the memory 106 (FIG. 1) may store object code of the software that the video encoder 200 receives and executes, or another memory (not shown) within the video encoder 200 may store such instructions.

[0075]

[0090] The video data memory 230 is configured to store the received video data. The video encoder 200 may retrieve pictures of the video data from the video data memory 230 and provide the video data to the residual generation unit 204 and the mode selection unit 202. The video data in the video data memory 230 may be raw video data to be encoded.

[0076]

[0091] 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 for performing video prediction according to other prediction modes. By way of example, the mode selection unit 202 may include a palette unit, an intra block copy unit (which may be part of the motion estimation unit 222 and / or the motion compensation unit 224), an affine unit, a linear model (LM) unit, etc.

[0077]

[0092] The mode selection unit 202 generally coordinates multiple encoding passes to test combinations of encoding parameters and resulting rate-distortion values ​​for such combinations. The encoding parameters may include partitioning of the CTU into CUs, prediction modes for the CUs, transform types for residual data of the CUs, quantization parameters for residual data of the CUs, etc. The mode selection unit 202 may finally select a combination of encoding parameters that has a rate-distortion value that is better than other tested combinations.

[0078]

[0093] Video encoder 200 may partition a picture retrieved from video data memory 230 into a series of CTUs and encapsulate one or more CTUs in a slice. Mode selection unit 202 may partition the CTUs of a picture according to a tree structure, such as the QTBT structure or quadtree structure of HEVC described above. As described above, video encoder 200 may form one or more CUs from partitioning the CTUs according to the tree structure. Such CUs may also be generally referred to as “video blocks” or “blocks.”

[0079]

[0094] In general, 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 a current block (e.g., the current CU, or in HEVC, the overlapping portion of the PU and TU). For inter prediction of the current block, the motion estimation unit 222 may perform motion search to identify one or more closely matching reference blocks in one or more reference pictures (e.g., one or more previously coded pictures stored in the DPB 218). In particular, the motion estimation unit 222 may calculate a value representing how similar a potential reference block is to the current block according to, for example, a sum of absolute differences (SAD), a sum of squared differences (SSD), a mean absolute difference (MAD), a mean squared difference (MSD), etc. The motion estimation unit 222 may generally perform these calculations using a sample-by-sample difference between the current block and the reference block under consideration. Motion estimation unit 222 may identify the reference block having the lowest value resulting from these calculations, which indicates the reference block that most closely matches the current block.

[0080]

[0095] The motion estimation unit 222 may form one or more motion vectors (MVs) that define the position of a reference block in a reference picture relative to the position of a current block in a current picture. The motion estimation unit 222 may then provide the motion vectors to the motion compensation unit 224. For example, in unidirectional inter prediction, the motion estimation unit 222 may provide a single motion vector, while in bidirectional inter prediction, the motion estimation unit 222 may provide two motion vectors. The motion compensation unit 224 may then generate a predictive block using the motion vectors. For example, the motion compensation unit 224 may use the motion vectors to retrieve data of the reference block. As another example, if the motion vectors have sub-sample precision, the motion compensation unit 224 may interpolate values ​​for the predictive block according to one or more interpolation filters. Moreover, in bidirectional inter prediction, the motion compensation unit 224 may retrieve data for the two reference blocks identified by the respective motion vectors and combine the retrieved data, for example, through sample-wise averaging or weighted averaging.

[0081]

[0096] As another example, for intra prediction, or intra predictive coding, the intra prediction unit 226 may generate a predictive block from samples neighboring a current block. For example, in a directional mode, the intra prediction unit 226 may generally mathematically combine values ​​of neighboring samples and populate these calculated values ​​in a prescribed direction across the current block to produce a predictive block. As another example, in DC intra mode prediction, the intra prediction unit 226 may calculate an average of the neighboring samples for the current block and generate a predictive block to include this resulting average for each sample of the predictive block.

[0082]

[0097] In one or more examples described in this disclosure, the intra prediction unit 226 may be configured to perform one or more of the example techniques described in this disclosure, alone or in combination with one or more other components. As an example, the mode selection unit 202 may be configured to determine that a current block of video data should be predicted utilizing DC intra mode prediction. In some examples of DC intra mode prediction, the samples used to generate the predictive block are samples in an immediately adjacent row (e.g., the row immediately above the current block) or column (e.g., the column immediately to the left of the current block).

[0083]

[0098] However, in some examples of DC intra mode prediction, the samples may be 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 are not the row 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 are not the column immediately to the left of the current block. Examples of non-adjacent rows and columns are described below with respect to the examples shown in Figures 11 to 19.

[0084]

[0099] As part of DC intra mode prediction, mode select unit 202 may generate information indicating which non-adjacent rows and / or columns contain samples that can be used for DC intra mode prediction. For example, video encoder 200 may signal a syntax element that indicates the number of rows to a non-adjacent row of samples above the current block or the number of columns to a non-adjacent column of samples to the left of the current block.

[0085]

[0100] In one or more examples, the intra prediction unit 226 may 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 may be configured to determine a plurality of samples in at least one of the samples of a non-adjacent row having a last sample in the same column as the last column of the current block. The samples of the non-adjacent row are two or more rows up of the current block. The intra prediction unit 226 may be configured to determine a sample of a non-adjacent column having a last sample in the same row as the last row of the current block. The samples of the non-adjacent column are two or more columns to the left of the current block. For example, as described in more detail with respect to Figures 16-19, the last sample (e.g., the right-most sample) from the plurality of samples in the non-adjacent row may be in the same column (e.g., have the same x-coordinate) as the last column (e.g., the column further to the right) of the current block, and the last sample (e.g., the bottom sample) from the plurality of samples in the non-adjacent column may be in the same row (e.g., have the same y-coordinate) as the last row (e.g., the bottom row) of the current block.

[0086]

[0101] In some examples, as described in more detail with respect to Figures 16 and 17, a first sample from a plurality of samples in a non-adjacent row (e.g., the sample further to the right) may be in the same column (e.g., have the same x-coordinate) as a first column (e.g., the leftmost column) of the current block, and a first sample from a plurality of samples in a non-adjacent column (e.g., the top sample) may be in the same row (e.g., have the same y-coordinate) as a first row (e.g., the top row) of the current block.

[0087]

[0102] In this manner, the intra prediction unit 226 may determine samples from non-adjacent rows or columns that are aligned with the current block and that should 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 or first sample in a non-adjacent row or column is not in the same row or column as the last or first row or column of the current block). Utilizing such samples from non-adjacent rows or columns that are not aligned with the current block may result in larger residuals and may also require additional memory accesses compared to utilizing samples from non-adjacent rows or columns that are aligned with the current block.

[0088]

[0103] 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, may intra-predictively code the current block based on the determined samples from non-adjacent rows or columns. For example, the intra-prediction unit 226 may generate a predictive block utilizing samples from non-adjacent rows and / or non-adjacent columns. The residual generation unit 204 may determine a residual block between the predictive block and the current block, which may be transformed, quantized, and entropy coded by the transform processing unit 206, the quantization unit 208, and the entropy coding unit 220, respectively.

[0089]

[0104] The mode selection unit 202 provides the prediction block to the residual generation unit 204. The residual generation unit 204 receives a raw 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 sample-by-sample differences between the current block and the prediction block. The resulting sample-by-sample differences define a residual block for the current block. In some examples, the residual generation unit 204 may also determine differences between sample values ​​in the residual block to generate the residual block using residual differential pulse code modulation (RDPCM). In some examples, the residual generation unit 204 may be formed using one or more subtractor circuits that perform binary subtraction.

[0090]

[0105] In an example where the mode selection unit 202 partitions a CU into PUs, each PU may be associated with a luma prediction unit and a corresponding chroma prediction unit. The video encoder 200 and the video decoder 300 may support PUs having various sizes. As indicated above, the size of a CU may refer to the size of the luma coding block of the CU, and the size of a PU may refer to the size of the luma prediction unit of the PU. Assuming that the size of a particular CU is 2N×2N, the video encoder 200 may support a PU size of 2N×2N or N×N for intra prediction, and a symmetric PU size of 2N×2N, 2N×N, N×2N, N×N, or the like for inter prediction. The video encoder 200 and the video decoder 300 may also support asymmetric partitioning of PU sizes of 2N×nU, 2N×nD, nL×2N, and nR×2N for inter prediction.

[0091]

[0106] In examples where the mode selection unit does not further partition CUs into PUs, each CU may be associated with a luma coding block and a corresponding chroma coding block. As noted above, the size of a CU may refer to the size of the luma coding block of the CU. Video encoder 200 and video decoder 300 may support CU sizes of 2N×2N, 2N×N, or N×2N.

[0092]

[0107] In other video coding techniques, such as intra block copy mode coding, affine mode coding, and linear model (LM) mode coding, as some examples, the mode selection unit 202 generates a predictive block for the current block being coded via a respective unit associated with the coding technique. In some examples, such as palette mode coding, the mode selection unit 202 may not generate a predictive block, but instead generate syntax elements that indicate how the block should be reconstructed based on a selected palette. In such modes, the mode selection unit 202 may provide these syntax elements to be coded to the entropy coding unit 220.

[0093]

[0108] As described above, the residual generation unit 204 receives the video data for a current block and the corresponding predictive 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 sample-by-sample differences between the predictive block and the current block.

[0094]

[0109] 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"). Transform processing unit 206 may apply various transforms to the residual block to form the transform coefficient block. For example, transform processing unit 206 may apply a discrete cosine transform (DCT), a directional transform, a Karhunen-Loeve transform (KLT), or a conceptually similar transform to the residual block. In some examples, transform processing unit 206 may perform multiple transforms on the residual block, e.g., a linear transform and a secondary transform such as a rotation transform. In some examples, transform processing unit 206 does not apply a transform to the residual block.

[0095]

[0110] 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 result in loss of information, and thus the quantized transform coefficients may have less precision than the original transform coefficients produced by transform processing unit 206.

[0096]

[0111] Inverse quantization unit 210 and inverse transform processing unit 212 may apply inverse quantization and inverse transform to the quantized transform coefficient block, respectively, to reconstruct a residual block from the transform coefficient block. Reconstruction unit 214 may produce a reconstructed block that corresponds to the current block (potentially with some distortion) based on the reconstructed residual block and the predictive block generated by mode selection unit 202. For example, reconstruction unit 214 may add samples of the reconstructed residual block to corresponding samples from the predictive block generated by mode selection unit 202 to produce a reconstructed block.

[0097]

[0112] 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 blockiness artifacts along the edges of a CU. The operations of filter unit 216 may be skipped in some examples.

[0098]

[0113] The video encoder 200 stores the reconstructed blocks in the DPB 218. For example, in examples where the operation of the filter unit 216 is not required, the reconstruction unit 214 may store the reconstructed blocks in the DPB 218. In examples where the operation of the filter unit 216 is required, the filter unit 216 may store the filtered reconstructed blocks in the DPB 218. The motion estimation unit 222 and the motion compensation unit 224 may retrieve reference pictures formed from the reconstructed (and potentially filtered) blocks from the DPB 218 to inter predict blocks of a later-encoded picture. Additionally, the intra prediction unit 226 may use the reconstructed blocks in the DPB 218 of the current picture to intra predict other blocks in the current picture.

[0099]

[0114] In general, the entropy encoding unit 220 may entropy encode syntax elements received from other functional components of the video encoder 200. For example, the entropy encoding unit 220 may entropy encode quantized transform coefficient blocks from the quantization unit 208. As another example, the entropy encoding unit 220 may entropy encode predictive syntax elements (e.g., motion information for inter prediction or intra mode information for intra prediction) from the mode selection unit 202. The entropy encoding unit 220 may perform one or more entropy encoding operations on syntax elements, which are another example of video data, to generate entropy encoded data. For example, the entropy encoding unit 220 may perform 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 partitioned entropy (PIPE) coding operation, an exponential-Golomb coding operation, or another type of entropy coding operation on the data. In some examples, the entropy encoding unit 220 may operate in a bypass mode in which syntax elements are not entropy coded.

[0100]

[0115] Video encoder 200 may output a bitstream that includes entropy-encoded syntax elements needed to reconstruct blocks of a slice or picture. In particular, entropy encoding unit 220 may output the bitstream.

[0101]

[0116] The operations described above are described with respect to blocks. Such descriptions should be understood as being 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 luma and chroma components of a CU. In some examples, the luma coding blocks and chroma coding blocks are luma and chroma components of a PU.

[0102]

[0117] In some examples, operations performed with respect to luma coding blocks do not need to be repeated for chroma coding blocks. As an example, operations for identifying motion vectors (MVs) and reference pictures for luma coding blocks do not need to be repeated to identify MVs and reference pictures for chroma blocks. Rather, the MVs for luma coding blocks may be scaled to determine the 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.

[0103]

[0118] As described above, video encoder 200 represents an example of a device configured to encode video data including a memory configured to store video data and one or more processing units implemented in a circuit configured to determine samples to use for DC intra-mode prediction for a current block, where determining the samples comprises determining a plurality of samples in non-adjacent rows with a last sample in the non-adjacent row being in the same column as the last column of the current block, or a plurality of samples in non-adjacent columns with a last sample in the non-adjacent column being in the same row as the last row of the current block. Video encoder 200 may encode the current block using DC intra-mode prediction using the determined samples.

[0104]

[0119] 4 is a block diagram illustrating an example video decoder 300 that may implement the techniques of this disclosure. FIG. 4 is provided for illustrative purposes and is not intended to limit the techniques broadly illustrated and described in this disclosure. For illustrative purposes, this disclosure describes the video decoder 300 in accordance with VVC and HEVC techniques. However, the techniques of this disclosure may be implemented by video coding devices configured for other video coding standards.

[0105]

[0120] In the example of Figure 4, the video decoder 300 includes a coded picture buffer (CPB) memory 320, an entropy decoding unit 302, a prediction processing unit 304, an inverse quantization unit 306, an inverse transform processing unit 308, a reconstruction unit 310, a filter unit 312, and a decoded picture buffer (DPB) 314. Any or all of the CPB memory 320, the entropy decoding unit 302, the prediction processing unit 304, the inverse quantization unit 306, the inverse transform processing unit 308, the reconstruction unit 310, the filter unit 312, and the DPB 314 may be implemented in one or more processors or processing circuits. Moreover, the video decoder 300 may include additional or alternative processors or processing circuits for performing these and other functions.

[0106]

[0121] Prediction processing unit 304 includes a motion compensation unit 316 and an intra prediction unit 318. Prediction processing unit 304 may include additional units for performing prediction according to other prediction modes. By way of example, prediction processing unit 304 may include a palette unit, an intra block copy unit (which may form part of motion compensation unit 316), an affine unit, a linear model (LM) unit, etc. In other examples, video decoder 300 may include more, fewer, or different functional components.

[0107]

[0122] The CPB memory 320 may store video data, such as an encoded video bitstream, to be decoded by components of the video decoder 300. The video data stored in the CPB memory 320 may be obtained, for example, from the computer-readable medium 110 (FIG. 1). The CPB memory 320 may include a CPB that stores encoded video data (e.g., syntax elements) from the encoded video bitstream. The CPB memory 320 may also store video data other than syntax elements of a coded picture, such as temporary data representing output from various units of the video decoder 300. The DPB 314 generally stores decoded pictures that the video decoder 300 may output and / or use as reference video data when decoding subsequent data or pictures of the encoded video bitstream. The CPB memory 320 and the DPB 314 may be formed by any of a variety of memory devices, such as DRAM, including SDRAM, MRAM, RRAM, or other types of memory devices. The CPB memory 320 and the DPB 314 may be provided by the same memory device or separate memory devices. In various examples, the CPB memory 320 may be on-chip with other components of the video decoder 300 or off-chip relative to those components.

[0108]

[0123] Additionally or alternatively, in some examples, video decoder 300 may retrieve coded video data from memory 120 (FIG. 1). That is, memory 120 may store data as described above along with CPB memory 320. Similarly, memory 120 may store instructions to be executed by video decoder 300 when some or all of the functionality of video decoder 300 is implemented in software to be executed by processing circuitry of video decoder 300.

[0109]

[0124] The various units shown in FIG. 4 are shown to aid in understanding the operations performed by the video decoder 300. The units may be implemented as fixed-function circuits, programmable circuits, or a combination thereof. As with FIG. 3, a fixed-function circuit refers to a circuit that provides a specific function and is preset with respect to the operations that may be performed. A programmable circuit refers to a circuit that may be programmed to perform various tasks and to provide flexible functionality in the operations that may 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 software or firmware instructions. A fixed-function circuit may execute software instructions (e.g., to receive parameters or output parameters), but the types of operations that the fixed-function circuit performs are generally unchanging. In some examples, one or more of the units may be separate circuit blocks (fixed function or programmable), and in some examples, one or more of the units may be integrated circuits.

[0110]

[0125] The video decoder 300 may include a programmable core formed from an ALU, an EFU, digital circuits, analog circuits, and / or programmable circuits. In examples in which the operations of the video decoder 300 are performed by software executing on programmable circuits, on-chip or off-chip memory may store instructions (e.g., object code) of the software that the video decoder 300 receives and executes.

[0111]

[0126] The entropy decoding unit 302 may receive the encoded video data from the CPB and entropy decode the video data to recover 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.

[0112]

[0127] In general, the video decoder 300 reconstructs a picture on a block-by-block basis. The video decoder 300 may perform a reconstruction operation on each block individually (wherein the block currently being reconstructed, i.e., the block currently being decoded, may be referred to as the “current block”).

[0113]

[0128] The entropy decoding unit 302 may entropy decode syntax elements defining the quantized transform coefficients of the quantized transform coefficient block, as well as transform information such as a quantization parameter (QP) and / or a transform mode indication(s). The inverse quantization unit 306 may use the QP associated with the quantized transform coefficient block to determine the degree of quantization and, similarly, the degree of inverse quantization that the inverse quantization unit 306 should apply. The inverse quantization unit 306 may perform, for example, a bitwise left shift operation to inverse quantize the quantized transform coefficients. The inverse quantization unit 306 may thereby form a transform coefficient block including the transform coefficients.

[0114]

[0129] 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 transform, or another inverse transform to the coefficient block.

[0115]

[0130] Further, prediction processing unit 304 generates a predictive block according to the prediction information syntax element entropy decoded by entropy decoding unit 302. For example, if the prediction information syntax element indicates that the current block is inter predicted, motion compensation unit 316 may generate a predictive block. In this case, the prediction information syntax element may indicate a reference picture in DPB 314 from which to retrieve a reference block, as well as a motion vector that identifies the location of the reference block in the reference picture relative to the location of the current block in the current picture. Motion compensation unit 316 may generally perform an inter prediction process in a manner substantially similar to that described with respect to motion compensation unit 224 (FIG. 3).

[0116]

[0131] 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 predictive block according to the intra prediction mode indicated by the prediction information syntax element. Again, the intra prediction unit 318 may generally perform an intra prediction process in a manner substantially similar to that described with respect to the intra prediction unit 226 (FIG. 3). The intra prediction unit 318 may retrieve data of neighboring samples for the current block from the DPB 314.

[0117]

[0132] In one or more examples described in this disclosure, the intra prediction unit 318 may be configured to perform one or more of the example techniques described in this disclosure, alone or in combination with one or more other components. As an example, the prediction processing unit 304 may be configured to utilize DC intra mode prediction to determine that a current block of video data should be predicted (e.g., based on receiving information signaled by the video encoder 200 indicating a prediction mode for the current block). In some examples of DC intra mode prediction, the samples used to generate the predictive block are samples in an immediately adjacent row (e.g., the row immediately above the current block) or column (e.g., the column immediately to the left of the current block).

[0118]

[0133] However, in some examples of DC intra mode prediction, the samples may be 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 are not the row 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 are not the column immediately to the left of the current block. Examples of non-adjacent rows and columns are described below with respect to the examples shown in Figures 11 to 19.

[0119]

[0134] As part of DC intra-mode prediction, prediction processing unit 304 may generate information indicating which non-adjacent rows and / or non-adjacent columns contain samples that may be used for DC intra-mode prediction. For example, video decoder 300 may receive a syntax element that indicates the number of rows to a non-adjacent row of samples above the current block or the number of columns to a non-adjacent column of samples 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 contain samples used for DC intra-mode prediction of the current block.

[0120]

[0135] In one or more examples, the intra prediction unit 318 may 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 may be configured to determine a plurality of samples in at least one of the non-adjacent row samples having a last sample in the same column as the last column of the current block. The non-adjacent row samples are two or more rows up of the current block. The intra prediction unit 318 may be configured to determine a non-adjacent column sample having a last sample in the same row as the last row of the current block. The non-adjacent column samples are two or more columns to the left of the current block. For example, as described in more detail with respect to Figures 16-19, the last sample (e.g., the right-most sample) from the plurality of samples in the non-adjacent row may be in the same column (e.g., have the same x-coordinate) as the last column (e.g., the column further to the right) of the current block, and the last sample (e.g., the bottom sample) from the plurality of samples in the non-adjacent column may be in the same row (e.g., have the same y-coordinate) as the last row (e.g., the bottom row) of the current block.

[0121]

[0136] In some examples, as described in more detail with respect to Figures 16 and 17, a first sample from a plurality of samples in a non-adjacent row (e.g., the sample further to the right) may be in the same column (e.g., have the same x-coordinate) as a first column (e.g., the leftmost column) of the current block, and a first sample from a plurality of samples in a non-adjacent column (e.g., the top sample) may be in the same row (e.g., have the same y-coordinate) as a first row (e.g., the top row) of the current block.

[0122]

[0137] In this manner, the intra prediction unit 318 may determine samples from non-adjacent rows or columns that are aligned with the current block and that should 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 or first sample in a non-adjacent row or column is not in the same row or column as the last or first row or column of the current block). Utilizing such samples from non-adjacent rows or columns that are not aligned with the current block may result in a larger residual error compared to utilizing samples from non-adjacent rows or columns that are aligned with the current block, and may also require reading additional samples.

[0123]

[0138] As described in more detail, the video decoder 300 may be configured to decode the current block using a DC intra-prediction mode that uses determined samples from non-adjacent rows or columns. For example, the intra-prediction unit 318 may generate a predictive block utilizing 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.

[0124]

[0139] The reconstruction unit 310 may reconstruct the current block using the predictive block and the residual block. For example, the reconstruction unit 310 may add samples of the residual block to corresponding samples of the predictive block to reconstruct the current block.

[0125]

[0140] Filter unit 312 may perform one or more filter operations on the reconstructed block. For example, filter unit 312 may perform a deblocking operation to reduce blockiness artifacts along edges of the reconstructed block. The operations of filter unit 312 are not necessarily performed in all examples.

[0126]

[0141] The video decoder 300 may store the reconstructed blocks in the DPB 314. As described above, the DPB 314 may provide reference information to the prediction processing unit 304, such as samples of the current picture for intra prediction and previously decoded pictures for subsequent motion compensation. Moreover, the video decoder 300 may output the decoded pictures from the DPB 314 for subsequent presentation on a display device, such as the display device 118 of FIG. 1.

[0127]

[0142] In this manner, the 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 a circuit, where the one or more processing units are configured to determine samples to use for DC intra-mode prediction for a current block, where determining the samples comprises determining a plurality of samples in non-adjacent rows with a last sample in the non-adjacent row being in the same column as the last column of the current block, or a plurality of samples in non-adjacent columns with a last sample in the non-adjacent column being in the same row as the last row of the current block. The video decoder 300 may be configured to decode the current block using DC intra-mode prediction using the determined samples.

[0128]

[0143] As described above, the exemplary techniques described in this disclosure may relate to intra prediction modes. The following describes intra prediction angles and wide-angle intra prediction. Intra prediction involves a DC prediction mode, a Planar prediction mode, and a directional (or angular) prediction mode. For a square block, the directional prediction, as shown in FIG. 5, uses directions between -135 degrees and 45 degrees of the current block in the Versatile Video Coding (VVC) Test Model 2 (VTM2) J. Chen, Y. Ye, S. Kim, "Algorithm description for Versatile Video Coding and Test Model 2 (VTM2)", the 11th JVET meeting, Ljubljana, Slovenia, July 2018, JVET-K1002.

[0129]

[0144] In VTM2, the block structure used to specify the prediction block for intra prediction is not limited to being square (width w = height h). Rectangular or non-square prediction blocks (w > h or w < h) can increase coding efficiency based on the characteristics of the content.

[0130]

[0145] In such rectangular blocks, restricting the intra prediction direction to be within -135 degrees to 45 degrees can result in a situation where farther reference samples are used instead of closer reference samples for intra prediction. Such a design may affect coding efficiency. It may be more beneficial to relax the range of the restriction so that closer reference samples (beyond the -135 degrees to 45 degrees angle) can be used for prediction. An example of such a case is given in FIG. 6. For example, FIG. 6 shows an example of an 8×4 rectangular block identified as the current block 500, where due to the restriction of the intra prediction direction to be within the range of -135 degrees to 45 degrees, closer reference samples (such as reference sample 502) are not used, but farther reference samples (such as reference sample 504) can be used.

[0131]

[0146] VTM2 also utilized a wide angle. An example of the wide angle employed in VTM2 is shown in FIG.

[0132]

[0147] During the 12th JVET meeting, changes to wide-angle intra prediction were introduced in the following documents: L. Zhao, X. Zhao, S. Liu, and X. Li, "CE3-related: Unification of angular intra prediction for square and non-square blocks," 12th JVET meeting, Macau SAR, China, October 2018, JVET-L0279; J. Chen, Y. Ye, and S. Kim, "Algorithm description for Versatile Video Coding and Test Model 3 (VTM3)," 12th JVET meeting, Macau SAR, China, October 2018, JVET-L1002; and B. Bross, J. Chen, and S. Liu, "Versatile Video Coding (Draft 3),” 12th JVET Meeting, Macau Special Administrative Region, China, October 2018, as described in JVET-L1001, and was adopted in the VVC Test Model 3.0 (VTM3).

[0133]

[0148] 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 direction is modified to cover the diagonal directions of all block shapes. Second, all angular directions are kept within the range between the lower-left diagonal direction and the upper-right diagonal direction for all block aspect ratios (square and non-square), as shown in Figures 7A-7C. Figure 7A shows that square blocks (e.g., coding unit 602) do not require angular mode remapping (e.g., angular directions between diagonal direction 604 and diagonal direction 606 are available). Figure 7B shows angular mode remapping for horizontal non-square blocks (e.g., coding unit 612). For example, there may be mode mapping of mode A and mode B outside the diagonal direction 614 to be within the diagonal direction 614 and diagonal direction 616. Figure 7C shows angular remapping for vertical non-square blocks (e.g., coding unit 622). For example, there may be a mode mapping of Mode A and Mode B outside of diagonal direction 624 to be within diagonal direction 624 and diagonal direction 626 .

[0134]

[0149] Furthermore, the number of reference samples in the top reference row and left reference column is limited to 2*width+1 and 2*height+1 for all block shapes. In FIG. 9 (for example, for FIG. 8) an illustration of the wider angle adopted in VTM3 is provided. Although VTM3 defines 95 modes, for any block size, only 67 modes can be allowed. The exact modes allowed depend on the ratio of block width to height. The allowance of the exact modes is done by restricting the mode range for some block sizes.

[0135]

[0150] Figure 10 specifies a mapping table between predModeIntra and intra prediction angle parameter intraPredAngle in VTM3 as described in JVET-L1001. Angular modes corresponding to the diagonals of non-square blocks, vertical and horizontal modes, and square block diagonal modes are utilized. In Figure 10, angular modes with positive intraPredAngle values ​​are referred to as positive angular modes (mode index <18 or >50), and angular modes with negative intraPredAngle values ​​are referred to as negative angular modes (mode index >18 and <50).

[0136]

[0151] The inverse angle parameter invAngle is derived based on intraPredAngle as follows:

[0137]

number

[0138]

[0152] 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 in the VTM3 specification.

[0139] [Table 1]

[0140]

[0153] The following describes prediction of multiple reference lines. Samples in the neighborhood of a coding block are used for intra prediction of the block. Typically, the reconstructed reference sample lines closest to the left and top boundaries of the coding block are used as reference samples for intra prediction. However, VVC WD4 also allows other samples in the neighborhood of the coding block to be used as reference samples. Figure 11 shows the reference sample lines that can be used for intra prediction. For each coding block, an index is signaled indicating the reference line to be used.

[0141]

[0154] In VVC WD4, only reference lines with MRLIdx equal to 0, 1 and 3 may be used. The index to the reference line used to code the block (values ​​0, 1 and 2 indicate lines with MRLIdx 0, 1 and 3, respectively) is coded using a shortened unary codeword. Planar and DC modes are not used since the reference lines used have MRLIdx>0.

[0142]

[0155] For example, in FIG. 11, for a current block 700, intra prediction unit 226 of video encoder 200 and intra prediction unit 318 of video decoder 300 may determine which rows and columns include reference samples that may be used for intra prediction. In FIG. 11, reference sample 702 refers to a reference sample from the row above current block 700, and reference sample 704 refers to a reference sample from the column to the left of current block 700. Video encoder 200 may signal a syntax element (e.g., MRLIdx) that indicates the number of rows to a non-adjacent row of samples above the current block or the number of columns to a non-adjacent column of samples to the left of the current block. Similarly, video decoder 300 may receive a syntax element (e.g., MRLIdx) that indicates the number of rows to a non-adjacent row of samples above the current block or the number of columns to a non-adjacent column of samples to the left of the current block. For example, if MRLIdx is equal to 0, the samples in the row immediately above and column immediately to the left of the current block 700 may be utilized. If MRLIdx is equal to 1, the samples in the non-adjacent row or column that is two rows above or two columns to the left of the current block 700 may be utilized. If MRLIdx is equal to 3, the samples in the non-adjacent row or column that is four rows above or four columns to the left of the current block 700 may be utilized.

[0143]

[0156] The following describes DC intra prediction mode. DC intra prediction mode is one of the prediction modes where 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 the derivation is as follows (copied from section 8.4.5.2.11 of JVET WD5):

[0144] The inputs to this process are: - variable nTbW, which specifies the transformation block width; - variable nTbH, which specifies the transformation block height, - a variable refIdx that specifies the intra prediction reference line index, - the adjacent samples p[x][y], where x=-1-refIdx, y=-1-refIdx..nTbH-refIdx-1 and x=-refIdx..nTbW-1-refIdx, y=-1-refIdx.

[0145] The output of this process is the predicted samples predSamples[x][y], where x=0..nTbW-1 and y=0..nTbH-1.

[0146] The values ​​of the predicted samples predSamples[x][y], where x=0..nTbW-1 and y=0..nTbH-1, are derived by the following sequence of steps: 1. The variable dcVal is derived as follows: - When nTbW is equal to nTbH,

[0147]

number

[0148] - When nTbW is greater than nTbH,

[0149]

number

[0150] - When nTbW is smaller than nTbH,

[0151]

number

[0152] 2. The predicted samples predSamples[x][y] are derived as follows:

[0153]

number

[0154]

[0157] Some of the techniques used for DC intra-mode prediction may have technical problems that adversely affect the coding process. For example, if a directly adjacent reference line (e.g., row or column) is used for prediction, i.e., MRLIdx is equal to 0, the DC value may 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 as shown in FIG. 12.

[0155]

[0158] 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. As shown in Figures 13 and 14, when MRLIdx>0 (e.g., indicating that the reference sample is from a non-adjacent row or column), the reference sample is shifted by an offset from the boundary of the block (and thus is misaligned). In Figure 13, MRLIdx is equal to 1, and as shown, the samples that may be used for DC intra prediction for the current block 708 are misaligned by one sample. In Figure 14, MRLIdx is equal to 3, and as shown, the samples that may be used for DC intra prediction for the current block 710 are misaligned by three samples.

[0156]

[0159] If one or more of the boundaries is small (e.g., 4x4 blocks), the misalignment is more severe, and as shown in Figure 15, for MRLIdx = 3, there is only one sample overlap. For example, Figure 15 shows a current block 712. In this case, the misalignment of samples used to intra predict the current block 712 is three samples. Since the current block 712 is 4x4 as shown in Figure 15, there is only one sample from the samples in the left column of the current block that aligns with the top row of the current block 712, and only one sample from the samples in the row above the current block that aligns with the first column of the current block 712.

[0157]

[0160] Such mismatches may result in less accurate prediction of DC values ​​and therefore poor and / or less optimal DC prediction. Although the figure shows square blocks here, such mismatches also occur in VVC for rectangular blocks, except in one direction (top or left, based on the aspect ratio).

[0158]

[0161] This disclosure describes example techniques for improving the design of DC intra-mode prediction. The example techniques may be implemented separately or together. In general, a video coder may determine a sample to be used for DC intra-mode prediction for a current block. To determine the sample, the video coder may be configured to determine a number of samples in non-adjacent rows with the last sample in the non-adjacent row being in the same column as the last column of the current block, or a number of samples in non-adjacent columns with the last sample in the non-adjacent column being in the same row as the last row of the current block.

[0159]

[0162] For example, as shown in Figures 16-19, dark blocks indicate reference samples from non-adjacent rows or columns (e.g., non-adjacent lines) of samples used for DC intra-mode prediction (e.g., intra-predicting in DC mode). For non-adjacent rows, the last sample in the non-adjacent row (e.g., right-most) may be in the same column as the last column of the current block being coded. For non-adjacent columns, the last sample in the non-adjacent column (e.g., bottom-most) may be in the same row as the last row of the current block being coded.

[0160]

[0163] In some examples, the first sample in a non-adjacent row (e.g., the leftmost) may be in the same column as the first column of the current block being coded. However, in some examples, the first sample in a non-adjacent row may be in the column to the left of the first column of the current block being coded. In some examples, the first sample in a non-adjacent row (e.g., the topmost) may be in the same row as the first row of the current block being coded. However, in some examples, the first sample in a non-adjacent column may be in the row above the first row of the current block being coded.

[0161]

[0164] For example, a video coder (e.g., video encoder 200 or video decoder 300) may be configured to determine a sample to use for DC intra prediction for a current block 714 of Figure 16. To determine the sample, the video coder may be configured to determine multiple samples in at least one of a non-adjacent row of samples (e.g., row 716 of Figure 16) whose last sample 722 is in the same column as the last column of the current block 714, or a non-adjacent column of samples (e.g., column 718) whose last sample 726 is in the same row as the last row of the current block 714.

[0162]

[0165] For example, in FIG. 16, sample 722 is in the same column as the last column of the current block 714 and is the last sample of the multiple samples in row 716, and sample 726 is in the same row as the last row of the current block 714 and is the last sample of the multiple samples in column 718. There may be additional samples to the right of sample 722 in row 716 and additional samples below sample 726 in column 718. However, the 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. In FIG. 16, non-adjacent rows of samples (e.g., samples in row 716) are two or more rows above the current block 714, and non-adjacent columns of samples (e.g., samples in column 718) are two or more columns to the left of the current block 714.

[0163]

[0166] The video coder may be configured to code (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 generate a predictive block based on the multiple samples, determine a residual block, and reconstruct the current block 714 based on the residual block and the predictive block, where the residual block indicates a difference between the current block 714 and the predictive block. The video encoder 200 may be configured to generate a predictive block based on the multiple samples, determine a residual block, and signal information indicating the residual block, where the residual block indicates a difference between the current block 714 and the predictive block.

[0164]

[0167] 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 row of samples (e.g., row 716) whose last sample 722 is in the same column as the last column of the current block 714 includes a first sample 720 that is in the same column as the first column of the current block 714. Also, in some examples, a non-adjacent column of samples (e.g., column 718) whose last sample 726 is in the same row as the last row of the current block 714 includes a first sample 724 that is in the same row as the first row of the current block 714. There may be a sample to the left of sample 720 and a sample above sample 724. However, in some examples, in the case of intra prediction, the samples from rows 716 used for DC intra mode prediction may be limited to samples that align with the leftmost and rightmost columns of the current block 714, and the samples from columns 718 used for DC intra mode prediction may be limited to samples that align with the topmost and bottommost rows of the current block 714.

[0165]

[0168] Current block 714 in Figure 16 may be considered a first block, and current block 728 in Figure 17 may be considered a second block. In some examples, the alignment of samples of current block 728 may be similar to that of current block 714, but the rows and columns whose samples are utilized for DC intra-mode prediction may be further away from current block 728 compared to current block 714.

[0166]

[0169] For example, a video coder (e.g., video encoder 200 or video decoder 300) may be configured to determine a sample to use for DC intra prediction for a current block 728 of Figure 17. To determine the sample, the video coder may be configured to determine multiple samples in at least one of a non-adjacent row of samples (e.g., row 730 of Figure 17) whose last sample 736 is in the same column as the last column of the current block 728, or a non-adjacent column of samples (e.g., column 732) whose last sample 740 is in the same row as the last row of the current block 728.

[0167]

[0170] For example, in FIG. 17, sample 736 is in the same column as the last column of the current block 728 and is the last sample of the multiple samples in row 730, and sample 740 is in the same row as the last row of the current block 728 and is the last sample of the multiple samples in column 732. There may be additional samples to the right of sample 736 in row 730 and additional 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. In FIG. 17, non-adjacent rows of samples (e.g., samples in row 730) are four or more rows above the current block 728, and non-adjacent columns of samples (e.g., samples in column 732) are four or more columns to the left of the current block 728.

[0168]

[0171] The video coder may be configured to intra-predictively code (e.g., encode or decode) the current block 728 based on the determined samples. For example, the video decoder 300 may be configured to generate a predictive block based on the plurality of samples, determine a residual block, and reconstruct the current block 728 based on the residual block and the predictive block, where the residual block indicates a difference between the current block 728 and the predictive block. The video encoder 200 may be configured to generate a predictive block based on the plurality of samples, determine a residual block, and signal information indicative of the residual block, where the residual block indicates a difference between the current block 728 and the predictive block.

[0169]

[0172] 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 row of samples (e.g., row 730) whose last sample 736 is in the same column as the last column of the current block 728 includes a first sample 734 that is in the same column as the first column of the current block 728. Also, in some examples, a non-adjacent column of samples (e.g., column 732) whose last sample 740 is in the same row as the last row of the current block 728 includes a first sample 738 that is in the same row as the first row of the current block 728. There may be a sample to the left of sample 734 and a sample above sample 738. However, in some examples, for intra prediction, the samples from rows 730 used for DC intra mode prediction may be limited to samples that align with the leftmost and rightmost columns of the current block 728, and the samples from columns 732 used for DC intra mode prediction may be limited to samples that align with the topmost and bottommost rows of the current block 728.

[0170]

[0173] In the examples of Figures 16 and 17, for MRLIdx greater than 0, the video coder may use reference samples aligned with block boundaries for DC prediction. Let (x0, y0) denote the position of the top-left sample of the current block 714 or current block 728, and let nW and nH denote the width and height of the current block 714 or 728, respectively. Let MRLIdx denote the index into the reference line. The top reference sample used for DC prediction may include a sample at location (x, y0-MRLIdx-1), where x=x0..x0+nW-1. The left reference sample used for DC prediction may include a sample at location (x0-MRLIdx-1, y), where y=y0..y0+nH-1. For example, reference samples used for MRLIdx equal to 1 and reference samples used for MRLIdx equal to 3 are shown in Figures 16 and 17, respectively.

[0171]

[0174] For MRLIdx greater than 0, the video coder uses reference samples aligned with block boundaries for DC prediction, and may further use additional reference samples for more accurate prediction. Let (x0, y0) denote the position of the top-left sample of the current block, and let nW and nH denote the width and height of the block. Let MRLIdx denote the index into the reference line. The top reference samples used for DC prediction may include samples at location (x-MRLIdx, y0-MRLIdx-1), where x=x0..x0+nW+MRLIdx-1. The left reference samples used for DC prediction include samples at location (x0-MRLIdx-1, y-MRLIdx), where y=y0..y0+nH+MRLIdx-1. For example, reference samples used for MRLIdx equal to 1 and reference samples used for MRLIdx equal to 3 are shown in FIG. 19 with current block 742 and FIG. 20 with current block 744, respectively.

[0172]

[0175] In some examples, the reference sample at position (x0-MRLIdx-1, y0-MRLIdx-1) may be used along with both the top and left reference samples above or to the left in the calculation of the DC value for the current block. The video coder may use a weighted average of the reference samples, with weights determined by one or more of the following factors: block size, aspect ratio, width, height, MRLIdx, intra mode of neighboring blocks, etc.

[0173]

[0176] Let valSumTop be the sum of the top reference sample values ​​of the current block used for DC prediction for a particular MRLIdx. Let valSumLeft be the sum of the left reference sample values ​​of the current block used for DC prediction for a particular MRLIdx. The DC value used for DC intra prediction is obtained as dcVal=(wT*valSumTop+wL*valSumLeft+off)>>sh, where off indicates an offset and sh indicates a shift (in some examples, the above calculation using off and sh may be replaced with a division operation). wT and wL are weights associated with the top and left reference samples and may be derived according to block characteristics. For example, wT and wL may be specified as follows:

[0174] [Table 2]

[0175] 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)である。

[0176]

[0177] 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 refer to a specific set of weights to be used for the upper reference sample and the left reference sample. In some examples, the reference sample positions used in the DC value calculation may be considered in separate DC modes. Multiple DC modes may be defined, where each DC mode may refer to a specific set of neighbors to be used for the upper reference sample and the left reference sample.

[0177]

[0178] The following references are available: S. De Luxan Hernandez, H. Schwarz, D. Marpe, T. Wiegand (HHI) "CE3: Line-based intra coding mode", JVET-L0076, S. De Luxan Hernandez, 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, SHKim, "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 intra mode list construction process", JVET-M0528, and J. Yao, J. Zhu, W. Cai, K. Kazui, "Non-CE3: Intra prediction information coding", JVET-M0210 may also provide some information for intra prediction.

[0178]

[0179] The following is an example technique in which reference samples that may be used for DC prediction are aligned with the top and left boundaries of a predicted block (e.g., such as those in Figures 16 and 17): The following is a proposed change to the specification (e.g., VVC Draft 5): Bold (underlined below) double brackets ([[...]]) indicate removal / deletion. 8.4.5.2.12 INTRA_DC Intra Prediction Mode Specifications The inputs to this process are: - variable nTbW, which specifies the transformation block width; - variable nTbH, which specifies the transformation block height, - a variable refIdx that specifies the intra prediction reference line index, - x=-1-refIdx, y=-1-refIdx..nTbH [[-refIdx]] -1 and x=-refIdx..nTbW-1 [[-refIdx]] , the neighboring sample p[x][y], where y=-1-refIdx.

[0179] The output of this process is the predicted samples predSamples[x][y], where x=0..nTbW-1, y=0..nTbH-1.

[0180] The values ​​of the predicted samples predSamples[x][y], where x=0..nTbW-1 and y=0..nTbH-1, are derived by the following sequence of steps: 3. The variable dcVal is derived as follows: - When nTbW is equal to nTbH,

[0181]

number

[0182] - When nTbW is greater than nTbH,

[0183]

number

[0184] - When nTbW is smaller than nTbH,

[0185]

number

[0186] 4. The predicted samples predSamples[x][y] are derived as follows:

[0187]

number

[0188]

[0180] Figure 19 is a flowchart illustrating an example method for encoding a current block. The current block may comprise a current CU. Although described with respect to video encoder 200 (Figures 1 and 3), it should be understood that other devices may be configured to perform a method similar to that of Figure 19. A memory (e.g., 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.

[0189]

[0181] A processing circuit of the video encoder 200 (e.g., the processing circuit 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 use for DC intra mode prediction for the current block, where, to determine the samples, the processing circuit may be configured to determine a plurality of samples in at least one of non-adjacent rows of samples having a last sample in the same column as the last column of the current block, where the non-adjacent rows of samples are two or more rows up of the current block, or non-adjacent columns of samples having a last sample in the same row as the last row of the current block, where the non-adjacent columns of samples are two or more columns to the left of the current block (800). In some examples, a non-adjacent row of samples having a last sample in the same column as the last column of the current block includes a first sample in the same column as the first column of the current block, and / or a non-adjacent column of samples having a last sample in the same row as the last row of the current block includes a first sample in the same row as the first row of the current block.

[0190]

[0182] As an example, coordinates for the top-left sample of the current block are (x0, y0), nW is the width of the current block, nH is the height of the current block, and MRLIdx indicates the number of rows to a non-adjacent row of samples above the current block or the number of columns to a non-adjacent column of samples 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 row of samples having coordinates (x, y0-MRLIdx-1), where x=x0...x0+nW-1, or a non-adjacent column of samples having coordinates (x0-MRLIdx-1, y), where y=y0...y0+nH-1.

[0191]

[0183] A processing circuit of the video encoder 200 may generate a predictive block based on the plurality of samples (802). The processing circuit of the video encoder 200 may determine a residual block indicating a difference between the predictive block and the current block (804). The processing circuit of the video encoder 200 may signal information indicating the residual block (806). The processing circuit of the video encoder 200 may also signal a syntax element (e.g., MRLIdx) indicating a number of rows to a non-adjacent row of samples above the current block or a number of columns to a non-adjacent column of samples to the left of the current block (808).

[0192]

[0184] Figure 20 is a flow chart illustrating an example method for decoding a current block of video data. The current block may comprise a current CU. Although described with respect to video decoder 300 (Figures 1 and 4), it should be understood that other devices may be configured to perform a method similar to that of Figure 20. 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 a row or column that is non-adjacent to the current block. The processing circuitry of the video decoder 300 may receive a syntax element (e.g., MRLIdx) that indicates a number of rows to a non-adjacent row of samples above the current block or a number of columns to a non-adjacent column of samples to the left of the current block (900).

[0193]

[0185] A processing circuit of the video decoder 300 (e.g., the processing circuit includes intra prediction unit 318, prediction processing unit 304, and one or more other components of the video decoder 300) may be configured to determine a sample to use for DC intra mode prediction for the current block, where, to determine the sample, the processing circuit may be configured to determine a number of samples in at least one of non-adjacent rows of samples (wherein the non-adjacent rows of samples are two or more rows up of the current block) having a last sample in the same column as the last column of the current block, or non-adjacent columns of samples (wherein the non-adjacent columns of samples are two or more columns to the left of the current block) having a last sample in the same row as the last row of the current block (902). In some examples, a non-adjacent row of samples having a last sample in the same column as the last column of the current block includes a first sample in the same column as the first column of the current block, and / or a non-adjacent column of samples having a last sample in the same row as the last row of the current block includes a first sample in the same row as the first row of the current block.

[0194]

[0186] As an example, coordinates for the top-left sample of a current block are (x0, y0), nW is the width of the current block, nH is the height of the current block, and MRLIdx indicates the number of rows to a non-adjacent row of samples above the current block or the number of columns to a non-adjacent column of samples 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 row of samples having coordinates (x, y0-MRLIdx-1), where x=x0...x0+nW-1, or a non-adjacent column of samples having coordinates (x0-MRLIdx-1, y), where y=y0...y0+nH-1.

[0195]

[0187] The processing circuitry of the video decoder 300 may generate a predictive block based on the multiple samples (904). The processing circuitry of the video decoder 300 may determine a residual block indicating a difference between the predictive 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 predictive block (908).

[0196]

[0188] One or more examples are described below. The example techniques may be used alone or in combination.

[0197]

[0189] Example 1. A method for coding video data, the method comprising: determining a sample to be used for DC intra-mode prediction for a current block, wherein determining the sample comprises determining a plurality of samples in non-adjacent rows having a last sample in the non-adjacent row that is in the same column as the last column of the current block, or a plurality of samples in non-adjacent columns having a last sample in the non-adjacent column that is in the same row as the last row of the current block, and intra-predictive coding the current block based on the determined samples.

[0198] Example 2. The method of example 1, wherein intra-predictive coding comprises intra-predictive decoding the current block.

[0199]

[0191] Example 3. The method described in Example 2, wherein intra-prediction decoding comprises determining a predictive block based on a plurality of samples, determining a residual block, the residual block indicating a difference between the current block and the predictive block, and reconstructing the current block based on the residual block and the predictive block.

[0200] Example 4. The method of example 1, wherein intra-predictive coding comprises intra-predictive coding the current block.

[0201]

[0193] Example 5. A method as described in Example 4, in which intra-predictive coding comprises determining a predictive block based on a plurality of samples, determining a residual block, and signaling information indicating the residual block, the residual block indicating a difference between the current block and the predictive block.

[0202]

[0194] Example 6. A method as described in any of Examples 1 to 5, wherein a plurality of samples in a non-adjacent row having a last sample in the non-adjacent row in the same column as the last column of the current block, or a plurality of samples in a non-adjacent column having a last sample in the non-adjacent column in the same row as the last row of the current block, comprises a plurality of samples in a non-adjacent row having a first sample in the non-adjacent row that is in the same column as the first column of the current block, or a plurality of samples in a non-adjacent column having a first sample in the non-adjacent column that is in the same row as the first row of the current block.

[0203]

[0195] Example 7. A method as described in any of Examples 1 to 5, wherein the plurality of samples in a non-adjacent row having a last sample in the non-adjacent row that is in the same column as the last column of the current block, or the plurality of samples in a non-adjacent column having a last sample in the non-adjacent column that is in the same row as the last row of the current block, comprises a plurality of samples in a non-adjacent row having a first sample in the non-adjacent row that is in the column to the left of the first column of the current block, or a plurality of samples in a non-adjacent column having a first sample in the non-adjacent column that is in the row above the first row of the current block.

[0204]

[0196] Example 8. A device for coding video data, the device comprising: a memory configured to store one or more samples of rows and columns that are not adjacent to a current block; and a video coder comprising at least one of fixed function or programmable circuitry, wherein the video coder is configured to implement a method according to any one or combination of Examples 1 to 7.

[0205]

[0197] Example 9. The device of Example 8, further comprising a display configured to display the decoded video data.

[0206]

[0198] Example 10. A device as described in any of Examples 8 and 9, wherein the device comprises one or more of a camera, a computer, a mobile device, a broadcast receiver device, or a set-top box.

[0207]

[0199] Example 11. A computer-readable storage medium having stored thereon instructions that, when executed, cause one or more processors to perform the method described in any of Examples 1-7.

[0208]

[0200] Example 12. A device for coding video data, the device comprising means for performing the method according to any one of Examples 1 to 7.

[0209]

[0201] In accordance with the above examples, it should be appreciated that some acts or events of any of the techniques described herein may be performed in a different sequence, added, merged, or omitted entirely (e.g., not all described acts or events may be necessary to practice the techniques). Moreover, in some examples, acts or events may be performed simultaneously rather than sequentially, for example, through multi-threaded processing, interrupt processing, or multiple processors.

[0210]

[0202] In one or more examples, the described functions may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions may be stored on or transmitted via a computer-readable medium as one or more instructions or code and executed by a hardware-based processing unit. The computer-readable medium may include a computer-readable storage medium, which corresponds to a tangible medium, such as a data storage medium, or may include a communication medium, including any medium that enables the transfer of a computer program from one place to another, for example, according to a communication protocol. In this manner, the computer-readable medium may generally correspond to (1) a tangible computer-readable storage medium that is non-transitory, or (2) a communication medium, such as a signal or carrier wave. The data storage medium may be any available medium that can be accessed by one or more computers or one or more processors to retrieve instructions, code and / or data structures for implementation of the techniques described in this disclosure. A computer program product may include a computer-readable medium.

[0211]

[0203] By way of example and not limitation, such computer-readable storage media may comprise RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, flash memory, or any other medium that may be used to store desired program code in the form of instructions or data structures and that may be accessed by a computer. Also, any connection is properly referred to as a computer-readable medium. For example, if instructions are transmitted from a website, server, or other remote source using coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared, radio, and microwave, the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are included in the definition of the medium. However, it should be understood that computer-readable storage media and data storage media do not include connections, carrier waves, signals, or other transitory media, but instead cover non-transitory tangible storage media. As used herein, disk and disc include compact disc (CD), laser disc, optical disc, digital versatile disc (DVD), floppy disk and Blu-ray disc, where disks typically reproduce data magnetically and discs reproduce data optically with lasers. Combinations of the above should also be included within the scope of computer readable media.

[0212]

[0204] The 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. Thus, the terms "processor" and "processing circuitry" as used herein may refer to any of the above structures, or any other structures suitable for implementing the techniques described herein. Furthermore, in some aspects, the functionality described herein may be provided in dedicated hardware and / or software modules configured for encoding and decoding, or incorporated into a composite codec. Also, the techniques may be fully implemented in one or more circuits or logic elements.

[0213]

[0205] The techniques of the present disclosure may be implemented in a wide variety of devices or apparatuses, including wireless handsets, integrated circuits (ICs) or sets of ICs (e.g., chipsets). In this disclosure, various components, modules, or units have been described to highlight functional aspects of devices configured to implement the disclosed techniques, but the components, modules, or units do not necessarily require realization by different hardware units. Rather, as described above, the various units may be combined in a codec hardware unit or provided by a collection of interoperable hardware units, including one or more processors described above, along with suitable software and / or firmware.

[0214]

[0206] Various examples have been described. These and other examples are within the scope of the following claims. The invention as described in the claims of the original application is set forth below. [C1] 1. A method for decoding video data, comprising the steps of: determining a sample to use for DC intra mode prediction for the current block, wherein determining the sample includes: non-adjacent rows of samples having their last sample in the same column as the last column of the current block, where the non-adjacent rows of samples are two or more rows above the current block; or non-adjacent columns of samples having a last sample in the same row as a last row of the current block, where the non-adjacent columns of samples are two or more columns to the left of the current block; determining a plurality of samples in at least one of decoding the current block using DC intra-mode prediction using the determined samples; and A method comprising: [C2] the non-adjacent rows of samples having the last sample in the same column as the last column of the current block include a first sample in the same column as a first column of the current block; or the non-adjacent columns of samples having the last sample in the same row as the last row of the current block include a first sample in the same row as a first row of the current block; The method according to claim 1, wherein the method is at least one of: [C3] the current block comprises a first block, the non-adjacent rows of samples comprise a first non-adjacent row of samples, and the non-adjacent columns of samples comprise a first non-adjacent column of samples, the method comprising: determining samples to use for DC intra mode prediction for a second block, wherein determining the samples to use for DC intra mode prediction for the second block comprises: a second non-adjacent row of samples having a first sample in a first column of the second block and a last sample in the same column as the last column of the current block, where the second non-adjacent row of samples is four or more rows up in the second block; or a second non-adjacent column of samples having a first sample in a first row of the second block and a last sample in the same row as a last row of the second block, where the second non-adjacent column of samples is four or more left columns of the second block; determining a plurality of samples in at least one of decoding the second block using DC intra-mode prediction using the determined samples to be used for DC intra-mode prediction for the second block; and The method of claim C1, further comprising: [C4] receiving a syntax element indicating a number of rows to the non-adjacent row of samples above the current block or a number of columns to the non-adjacent column of samples to the left of the current block; The method of claim C1, further comprising: [C5] where the coordinates for a top-left sample of the current block are (x0,y0), nW is the width of the current block, nH is the height of the current block, and MRLIdx indicates the number of rows to the non-adjacent row of samples above the current block or the number of columns to the non-adjacent column of samples to the left of the current block, and the method comprises: the non-adjacent rows of samples having coordinates (x,y0-MRLIdx-1), where x=x0...x0+nW-1; or said non-adjacent columns of samples having coordinates (x0-MRLIdx-1,y), where y=y0...y0+nH-1; The method of claim 1, further comprising determining at least one of: [C6] performing a weighted average of the determined samples; The method of C1, wherein decoding the current block comprises decoding the current block using DC intra-mode prediction using the weighted average of the determined samples. [C7] To decrypt, 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; reconstructing the current block based on the residual block and the predicted block; The method of claim C1, comprising: [C8] 1. A method for encoding video data, comprising the steps of: determining a sample to use for DC intra mode prediction for the current block, wherein determining the sample includes: non-adjacent rows of samples having their last sample in the same column as the last column of the current block, where the non-adjacent rows of samples are two or more rows above the current block; or non-adjacent columns of samples having a last sample in the same row as a last row of the current block, where the non-adjacent columns of samples are two or more columns to the left of the current block; determining a plurality of samples in at least one of encoding the current block using DC intra-mode prediction using the determined samples; and A method comprising: [C9] the non-adjacent rows of samples having the last sample in the same column as the last column of the current block include a first sample in the same column as a first column of the current block; or the non-adjacent columns of samples having the last sample in the same row as the last row of the current block include a first sample in the same row as a first row of the current block; 9. The method according to claim 8, wherein the method is at least one of: [C10] the current block comprises a first block, the non-adjacent rows of samples comprise a first non-adjacent row of samples, and the non-adjacent columns of samples comprise a first non-adjacent column of samples, the method comprising: determining samples to use for DC intra mode prediction for a second block, wherein determining the samples to use for DC intra mode prediction for the second block comprises: a second non-adjacent row of samples having a first sample in a first column of the second block and a last sample in the same column as the last column of the current block, where the second non-adjacent row of samples is four or more rows up in the second block; or a second non-adjacent column of samples having a first sample in a first row of the second block and a last sample in the same row as a last row of the second block, where the second non-adjacent column of samples is four or more left columns of the second block; determining a plurality of samples in at least one of encoding the second block using DC intra-mode prediction using the determined samples to be used for DC intra-mode prediction for the second block; and The method of C8, further comprising: [C11] signaling a syntax element indicating a number of rows to the non-adjacent row of samples above the current block or a number of columns to the non-adjacent column of samples to the left of the current block; The method of C8, further comprising: [C12] where the coordinates for a top-left sample of the current block are (x0, y0), nW is the width of the current block, nH is the height of the current block, and MRLIdx indicates the number of rows to the non-adjacent row of samples above the current block or the number of columns to the non-adjacent column of samples to the left of the current block, said method comprising: said non-adjacent rows of samples having coordinates (x,y0-MRLIdx-1), where x=x0...x0+nW-1; or said non-adjacent columns of samples having coordinates (x0-MRLIdx-1,y), where y=y0...y0+nH-1; The method of claim 8, further comprising determining at least one of: [C13] performing a weighted average of the determined samples; The method of C8, wherein encoding the current block comprises encoding the current block using DC intra-mode prediction using the weighted average of the determined samples. [C14] To encode, 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; signaling information indicative of the residual block; The method of C8, comprising: [C15] 1. A device for decoding video data, comprising: a memory configured to store one or more samples of non-adjacent rows and columns of the current block; A processing circuit; The processing circuitry comprises: determining a sample to use for DC intra mode prediction for the current block, where to determine the sample, the processing circuitry comprises: non-adjacent rows of samples having their last sample in the same column as the last column of the current block, where the non-adjacent rows of samples are two or more rows above the current block; or non-adjacent columns of samples having a last sample in the same row as a last row of the current block, where the non-adjacent columns of samples are two or more columns to the left of the current block; and configured to determine a plurality of samples in at least one of: decoding the current block using DC intra-mode prediction using the determined samples; and A device configured to: [C16] the non-adjacent rows of samples having the last sample in the same column as the last column of the current block include a first sample in the same column as a first column of the current block; or the non-adjacent columns of samples having the last sample in the same row as the last row of the current block include a first sample in the same row as a first row of the current block; The device according to C15, wherein the device is at least one of: [C17] the current block comprises a first block, the non-adjacent rows of samples comprise a first non-adjacent row of samples, and the non-adjacent columns of samples comprise a first non-adjacent column of samples, and the processing circuitry: determining samples to use for DC intra mode prediction for a second block, where to determine the samples to use for DC intra mode prediction for the second block, the processing circuitry a second non-adjacent row of samples having a first sample in a first column of the second block and a last sample in the same column as a last column of the current block, where the second non-adjacent row of samples is four or more rows up in the second block; or a second non-adjacent column of samples having a first sample in a first row of the second block and a last sample in the same row as a last row of the second block, where the second non-adjacent column of samples is four or more left columns of the second block; and configured to determine a plurality of samples in at least one of: decoding the second block using DC intra-mode prediction using the determined samples to be used for DC intra-mode prediction for the second block; and The device of claim 15, configured to: [C18] The processing circuitry includes: receiving a syntax element indicating a number of rows to the non-adjacent row of samples above the current block or a number of columns to the non-adjacent column of samples to the left of the current block; 20. The device of claim 15, configured as follows: [C19] where the coordinates for the top left sample of the current block are (x0, y0), nW is the width of the current block, nH is the height of the current block, and MRLIdx indicates the number of rows to the non-adjacent row of samples above the current block or the number of columns to the non-adjacent column of samples to the left of the current block, and the processing circuitry said non-adjacent rows of samples having coordinates (x,y0-MRLIdx-1), where x=x0...x0+nW-1; or said non-adjacent columns of samples having coordinates (x0-MRLIdx-1,y), where y=y0...y0+nH-1; The device of claim 15, configured to determine at least one of: [C20] The processing circuitry includes: configured to perform a weighted average of the determined samples; The device of C15, wherein, to decode the current block, the processing circuitry is configured to decode the current block using DC intra-mode prediction using the weighted average of the determined samples. [C21] To decode, the processing circuitry: 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; reconstructing the current block based on the residual block and the predicted block; The device of claim 15, configured to: [C22] The device of C15, further comprising a display configured to display the decoded video data. [C23] The device of C15, wherein the device comprises one or more of a camera, a computer, a mobile device, a broadcast receiver device, or a set-top box. [C24] 1. A device for encoding video data, comprising: a memory configured to store one or more samples of non-adjacent rows and columns of the current block; A processing circuit; The processing circuitry comprises: determining a sample to use for DC intra mode prediction for the current block, where to determine the sample, the processing circuitry: non-adjacent rows of samples having their last sample in the same column as the last column of the current block, where the non-adjacent rows of samples are two or more rows above the current block; or non-adjacent columns of samples having a last sample in the same row as a last row of the current block, where the non-adjacent columns of samples are two or more columns to the left of the current block; and configured to determine a plurality of samples in at least one of: encoding the current block using DC intra-mode prediction using the determined samples; and A device configured to: [C25] the non-adjacent rows of samples having the last sample in the same column as the last column of the current block include a first sample in the same column as a first column of the current block; or the non-adjacent columns of samples having the last sample in the same row as the last row of the current block include a first sample in the same row as a first row of the current block; The device according to C24, wherein the device is at least one of: [C26] To encode, the processing circuitry 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; signaling information indicative of the residual block; 23. The device of claim 22, configured to: [C27] A computer-readable storage medium having stored thereon instructions that, when executed, cause one or more processors to: determining samples to use for DC intra mode prediction for a current block, wherein the instructions causing the one or more processors to determine the samples may further include causing the one or more processors to: non-adjacent rows of samples having their last sample in the same column as the last column of the current block, where the non-adjacent rows of samples are two or more rows above the current block; or non-adjacent columns of samples having a last sample in the same row as a last row of the current block, where the non-adjacent columns of samples are two or more columns to the left of the current block; determining a plurality of samples in at least one of: decoding the current block using DC intra-mode prediction using the determined samples; and A computer-readable storage medium for causing a computer to perform the above steps. [C28] 1. A device for decoding video data, comprising: means for determining a sample to use for DC intra mode prediction for a current block, wherein the means for determining the sample comprises: non-adjacent rows of samples having their last sample in the same column as the last column of the current block, where the non-adjacent rows of samples are two or more rows above the current block; or non-adjacent columns of samples having a last sample in the same row as a last row of the current block, where the non-adjacent columns of samples are two or more columns to the left of the current block; means for determining a plurality of samples in at least one of means for decoding the current block using DC intra-mode prediction using the determined samples; A device comprising:

Claims

1. 1. A method for decoding video data, comprising the steps of: determining samples for generating DC values ​​to be used for DC intra-mode prediction for a current block, wherein the determining the samples comprises determining a plurality of samples among at least one of an above reference sample or a left reference sample of the current block; the above reference samples comprise a non-adjacent row of samples having a first sample in the same column as a first column of the current block and a last sample in the same column as a last column of the current block, and an additional sample to the left of the first sample in the non-adjacent row of samples, where the non-adjacent row of samples is two or more rows above the current block; the left reference samples comprise a non-adjacent column of samples having a first sample in the same row as a first row of the current block and a last sample in the same row as a last row of the current block, and an additional sample above the first sample in the non-adjacent column of samples, where the non-adjacent column of samples is two or more columns to the left of the current block; decoding the current block using DC intra-mode prediction using the DC value; and A method comprising:

2. the current block comprises a first block, the non-adjacent rows of samples comprise a first non-adjacent row of samples, and the non-adjacent columns of samples comprise a first non-adjacent column of samples, the method comprising: determining samples to use for DC intra mode prediction for a second block, wherein determining the samples to use for DC intra mode prediction for the second block includes: a second non-adjacent row of samples having a first sample in a first column of the second block and a last sample in the same column as the last column of the second block, where the second non-adjacent row of samples is four or more rows up of the second block; or a second non-adjacent column of samples having a first sample in a first row of the second block and a last sample in the same row as a last row of the second block, where the second non-adjacent column of samples is four or more left columns of the second block; determining a plurality of samples in at least one of decoding the second block using DC intra-mode prediction using the determined samples to be used for DC intra-mode prediction for the second block; and The method of claim 1 further comprising:

3. receiving a syntax element indicating a number of rows to the non-adjacent row of samples above the current block or a number of columns to the non-adjacent column of samples to the left of the current block; and / or performing a weighted average of the determined samples; Further equipped with 2. The method of claim 1, wherein decoding the current block comprises decoding the current block using DC intra-mode prediction that uses the weighted average of the determined samples.

4. To decrypt, 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; reconstructing the current block based on the residual block and the predicted block; The method of claim 1 , comprising:

5. 1. A method for encoding video data, comprising the steps of: determining samples for generating DC values ​​to be used for DC intra-mode prediction for a current block, wherein the determining the samples comprises determining a plurality of samples among at least one of an above reference sample or a left reference sample of the current block; the above reference samples comprise a non-adjacent row of samples having a first sample in the same column as a first column of the current block and a last sample in the same column as a last column of the current block, and an additional sample to the left of the first sample in the non-adjacent row of samples, where the non-adjacent row of samples is two or more rows above the current block; the left reference samples comprise a non-adjacent column of samples having a first sample in the same row as a first row of the current block and a last sample in the same row as a last row of the current block, and an additional sample above the first sample in the non-adjacent column of samples, where the non-adjacent column of samples is two or more columns to the left of the current block; encoding the current block using DC intra-mode prediction using the DC value; and A method comprising:

6. the current block comprises a first block, the non-adjacent rows of samples comprise a first non-adjacent row of samples, and the non-adjacent columns of samples comprise a first non-adjacent column of samples, the method comprising: determining samples to use for DC intra mode prediction for a second block, wherein determining the samples to use for DC intra mode prediction for the second block includes: a second non-adjacent row of samples having a first sample in a first column of the second block and a last sample in the same column as the last column of the second block, where the second non-adjacent row of samples is four or more rows up of the second block; or a second non-adjacent column of samples having a first sample in a first row of the second block and a last sample in the same row as a last row of the second block, where the second non-adjacent column of samples is four or more left columns of the second block; determining a plurality of samples in at least one of encoding the second block using DC intra-mode prediction using the determined samples to be used for DC intra-mode prediction for the second block; and The method of claim 5 further comprising:

7. signaling a syntax element indicating the number of rows to the non-adjacent row of samples above the current block or the number of columns to the non-adjacent column of samples to the left of the current block; and / or performing a weighted average of the determined samples; Further equipped with The method of claim 5 , wherein encoding the current block comprises encoding the current block using DC intra-mode prediction using the weighted average of the determined samples.

8. where the coordinates for the top left sample of the current block are (x0, y0), nW is the width of the current block, nH is the height of the current block, and MRLIdx indicates the number of rows to the non-adjacent row of samples above the current block or the number of columns to the non-adjacent column of samples to the left of the current block; Determining the non-adjacent rows of samples comprises determining samples having coordinates (x, y0-MRLIdx-1), where x=x0...x0+nW-1; and / or Determining the non-adjacent columns of samples comprises determining samples having coordinates (x0-MRLIdx-1,y), where y=y0...y0+nH-1; The method according to claim 1 or 5.

9. To encode, 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; signaling information indicative of the residual block; The method of claim 5 comprising:

10. 1. A device for decoding video data, comprising: a memory configured to store one or more samples of non-adjacent rows and columns of a current block; A processing circuit; The processing circuitry comprises: determining a sample for generating a DC value to be used for DC intra-mode prediction for a current block, where to determine the sample, the processing circuit is configured to determine a plurality of samples among at least one of an above reference sample or a left reference sample of the current block; the above reference samples comprise a non-adjacent row of samples having a first sample in the same column as a first column of the current block and a last sample in the same column as a last column of the current block, and an additional sample to the left of the first sample in the non-adjacent row of samples, where the non-adjacent row of samples is two or more rows above the current block; the left reference samples comprise a non-adjacent column of samples having a first sample in the same row as a first row of the current block and a last sample in the same row as a last row of the current block, and an additional sample above the first sample in the non-adjacent column of samples, where the non-adjacent column of samples is two or more columns to the left of the current block; decoding the current block using DC intra-mode prediction using the DC value; and A device configured to:

11. The device of claim 10 , wherein the processing circuitry is configured to perform the method of any one of claims 2 , 3 , 4 , or 8 .

12. and / or a display configured to display the decoded video data. The device of claim 10 , wherein the device comprises one or more of a camera, a computer, a mobile device, a broadcast receiver device, or a set-top box.

13. 1. A device for encoding video data, comprising: a memory configured to store one or more samples of non-adjacent rows and columns of a current block; A processing circuit; The processing circuitry comprises: determining a sample for generating a DC value to be used for DC intra-mode prediction for a current block, where to determine the sample, the processing circuit is configured to determine a plurality of samples among at least one of an above reference sample or a left reference sample of the current block; the above reference samples comprise a non-adjacent row of samples having a first sample in the same column as a first column of the current block and a last sample in the same column as a last column of the current block, and an additional sample to the left of the first sample in the non-adjacent row of samples, where the non-adjacent row of samples is two or more rows above the current block; the left reference samples comprise a non-adjacent column of samples having a first sample in the same row as a first row of the current block and a last sample in the same row as a last row of the current block, and an additional sample above the first sample in the non-adjacent column of samples, where the non-adjacent column of samples is two or more columns to the left of the current block; encoding the current block using DC intra-mode prediction using the DC value; and A device configured to:

14. 14. A device according to claim 13, wherein the processing circuitry is configured to carry out a method according to any one of claims 6 to 9.

15. 10. A computer readable storage medium having stored thereon instructions which, when executed, cause one or more processors to perform the method of any one of claims 1-4 or 5-9.

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