Decoder-side intra-mode derivation for constructing the most probable mode list in video coding

Abstract

A method for decoding video data includes deriving a list of intra modes for a current block of the video data and using decoder-side intra mode derivation (DIMD) using reconstructed samples of neighboring blocks, constructing a most probable mode (MPM) list for the current block, and predicting the current block using candidates selected from the constructed MPM list, wherein constructing the MPM list comprises inserting at least one intra mode from the derived list of intra modes into the MPM list.

Description

[Technical Field]

[0001]

[0001] This application claims priority to U.S. Patent Application No. 17 / 502,875, filed October 15, 2021, and U.S. Provisional Patent Application No. 63 / 129,004, filed December 22, 2020, the entire contents of which are incorporated herein by reference. U.S. Patent Application No. 17 / 502,875, filed October 15, 2021, claims the benefit of U.S. Provisional Patent Application No. 63 / 129,004, filed December 22, 2020.

[0002] FIELD OF THE DISCLOSURE

[0002] This disclosure relates to video encoding and video 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 gaming devices, video game consoles, cellular or satellite radiotelephones, so-called "smartphones," video teleconferencing devices, video streaming devices, etc. Digital video devices implement video coding techniques, such as those described in standards defined by MPEG-2, MPEG-4, ITU-T H.263, ITU-T H.264 / MPEG-4, Part 10, Advanced Video Coding (AVC), ITU-T H.265 / High Efficiency Video Coding (HEVC), 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 coding video data using derived intra mode deviation (DIMD). To perform intra mode coding without DIMD, a video coder (e.g., a video encoder and / or a video decoder) may build a list of intra mode candidates (e.g., a most probable mode (MPM) list) and signal which candidate from the list is to be used as the intra mode for a current block. To perform intra mode coding with DIMD, a video decoder may implicitly derive an intra mode for a current block based on reconstructed samples of neighboring blocks and predict the current block based on a mixture of the derived intra modes. A video encoder may determine whether to predict a current block using DIMD and signal a syntax element indicating whether the current block is predicted using DIMD or a list (e.g., not predicted using DIMD). However, implementations of DIMD may present various drawbacks. For example, implementations of DIMD prediction may involve a video encoder determining whether to perform intra prediction using mixed prediction from multiple DIMD-derived modes or from a single mode. Such implementations may sacrifice robustness, where the optimal prediction mode is one of the DIMD-derived modes, but the optimal prediction may be from only a single prediction (e.g., as opposed to mixed prediction from a DIMD-derived mode).

[0006] According to one or more techniques of this disclosure, a video coder (e.g., a video encoder and / or a video decoder) may include one or more of the DIMD derived modes as candidate intra modes in a most probable mode (MPM) list. For example, the video coder may perform DIMD mode derivation to derive one or more DIMD modes and include the one or more derived DIMD modes in a list of intra mode candidates. The video coder may signal which candidate from the list is to be used as the intra mode for the current block. For example, if one of the DIMD modes included in the list is an optimal prediction mode, the video encoder may signal that the particular DIMD mode should be used as the intra mode for the current block. Use of a more optimal mode may reduce the number of bits used to represent video data. Thus, in this manner, the techniques of this disclosure may improve coding efficiency.

[0007]

[0007] In one example, a method for decoding video data includes deriving a list of intra modes using reconstructed samples of adjacent blocks for a current block of video data and using DIMD, constructing a most probable mode (MPM) list for the current block, and predicting the current block using candidates selected from the constructed MPM list, wherein constructing the MPM list comprises inserting at least one intra mode from the derived list of intra modes into the MPM list.

[0008]

[0008] In another example, an encoding method includes deriving a list of intra modes for a current block of video data and using DIMD using reconstructed samples of neighboring blocks, constructing an MPM list for the current block, wherein constructing the MPM list comprises inserting at least one intra mode from the derived list of intra modes into the MPM list, selecting a candidate intra mode for the current block and from the MPM list, and encoding one or more syntax elements specifying the candidate intra mode for the current block.

[0009]

[0009] In another example, a device for decoding video data includes a memory configured to store video data and one or more processors implemented in a circuit, wherein the one or more processors are configured to: derive a list of intra modes for a current block of video data using DIMD and reconstructed samples of neighboring blocks; construct an MPM list for the current block; and predict the current block using candidates selected from the constructed MPM list, wherein constructing the MPM list comprises inserting at least one intra mode from the derived list of intra modes into the MPM list.

[0010]

[0010] In another example, a device for encoding video data includes a memory configured to store the video data and one or more processors implemented in a circuit, wherein the one or more processors are configured to: derive a list of intra modes for a current block of video data and using DIMD using reconstructed samples of adjacent blocks; construct an MPM list for the current block, wherein constructing the MPM list comprises inserting at least one intra mode from the derived list of intra modes into the MPM list; select a candidate intra mode for the current block and from the MPM list; and encode one or more syntax elements specifying the candidate intra mode for the current block.

[0011] 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 explanation of the drawings]

[0012] [Figure 1]

[0012] FIG. 1 is a block diagram illustrating an example video encoding and decoding system that may implement the techniques of this disclosure. [Figure 2A]

[0013] 1 is a conceptual diagram illustrating an exemplary quad-tree binary tree (QTBT) structure. [Figure 2B] A conceptual diagram showing the corresponding coding tree unit (CTU). [Figure 3]

[0014] 1 is a block diagram illustrating an example video encoder that may implement the techniques of this disclosure. [Figure 4]

[0015] 1 is a block diagram illustrating an example video decoder that may implement the techniques of this disclosure. [Figure 5]

[0016] 1 is a conceptual diagram illustrating a set of pixels on which a video coder may perform gradient analysis. [Figure 6]

[0017] 1 is a graph showing an example of orientation index mapping using horizontal and vertical gradients. [Figure 7]

[0018] Graph showing the selection of the two most possible prediction modes. [Figure 8]

[0019] 1 is a conceptual diagram illustrating an example prediction for a decoder side intra mode derivation (DIMD) mode. [Figure 9A]

[0020] 1 is a flow diagram illustrating an example technique for intra-block decoding. [Figure 9B]

[0021] 1 is a flow diagram illustrating an example technique for intra-block decoding using DIMD. [Figure 10]

[0022] 1 is a flow diagram illustrating an example technique for intra-block decoding using DIMD most probable mode (MPM) list building, in accordance with one or more techniques of this disclosure. [Figure 11]

[0023] 1 is a flow diagram illustrating an example technique for MPM list construction, in accordance with one or more techniques of this disclosure. [Figure 12]

[0024] 10 is a flow diagram illustrating an example technique for deriving a list of intra-modes via DIMD, in accordance with one or more techniques of this disclosure. [Figure 13]

[0025] FIG. 10 is a conceptual diagram showing an example of adjacent blocks. [Figure 14]

[0026] 10 is a flow diagram illustrating an example technique for adding a DIMD derivation mode into an MPM list, in accordance with one or more techniques of this disclosure. [Figure 15]

[0027] 10 is a flowchart illustrating an example method for encoding a current block, in accordance with techniques of this disclosure. [Figure 16]

[0028] 10 is a flowchart illustrating an example method for decoding a current block, in accordance with techniques of this disclosure. [Figure 17]

[0029] 1 is a flowchart illustrating an example technique for encoding video data using DIMD, in accordance with one or more techniques of this disclosure. [Figure 18]

[0030] 1 is a flowchart illustrating an example technique for decoding video data using DIMD, in accordance with one or more techniques of this disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0013]

[0031] Video coding standards include ITU-T H.261, ISO / IEC MPEG-1 Visual, ITU-T H.262 or ISO / IEC MPEG-2 Visual, ITU-T H.263, ISO / IEC MPEG-4 Visual (MPEG-4 Part 2), ITU-T H.264 (also known as ISO / IEC MPEG-4 AVC) including its Scalable Video Coding (SVC) extension and Multiview Video Coding (MVC) extension, ITU-T H.265 (also known as ISO / IEC MPEG-4 HEVC) with its extensions, and Video Coding (VVC) Standardization Activity (also known as ITU-T H.266).

[0014]

[0032] JVET-L0164 "CE3-related: Decoder-side Intra Mode Derivation," Joint Video Experts Team (JVET) of ITU-T SG16 WP3 and ISO / IEC JTC 1 / SC29 / WG11, 12th Meeting: Macao, China, October 3-12, 2018, Document: JVET-L0164 (available at https: / / jvet-experts.org / doc_end_user / documents / 12_Macao / wg11 / JVET-L0164-v2.zip), JVET-M0094 "CE3: Decoder-side Intra Mode Derivation (tests 3.1.1, 3.1.2, 3.1.3 and 3.1.4)," ITU-T SG16 WP3 and ISO / IEC JTC Joint Video Experts Team (JVET) with 1 / SC29 / WG11, 13th Meeting: Marrakech, Morocco, January 9-18, 2019, Document: JVET-M0094 (https: / / jvet-experts.org / doc_end_user / documents / 13_Marrakech / wg11 / JVET-M0094-v2.zip), JVET-N0342 "Non-CE3: Decoder-side Intra Mode Derivation with Prediction Fusion" ITU-T SG16 WP3 and ISO / IEC JTC Joint Video Experts Team (JVET) with WG11 / SC29 / WG11, 14th Meeting: Geneva, Switzerland, March 19-29, 2019, Document: JVET-N0342 (https: / / jvet-experts.org / doc_end_user / documents / 14_Geneva / wg11 / JVET-N0342-v5.In JVET-O0449, "Non-CE3: Decoder-side Intra Mode Derivation with Prediction Fusion Using Planar," Joint Video Experts Team (JVET) of ITU-T SG16 WP3 and ISO / IEC JTC 1 / SC29 / WG11, 15th Meeting: Gothenburg, Sweden, July 3–12, 2019, document: JVET-O0449 (https: / / jvet-experts.org / doc_end_user / documents / 15_Gothenburg / wg11 / JVET-O0449-v2.zip), decoder-side intra mode derivation (DIMD) is proposed as a coding tool for intra prediction. The difference from existing intra prediction tools is that when implementing DIMD, the video coder may not explicitly signal the intra mode. Instead, the video coder may implicitly derive the intra mode using reconstructed samples of neighboring blocks. The purpose is to improve coding efficiency by eliminating the need for intra mode signaling. Note that DIMD may only be applied to luma; for chroma, classical intra coding modes may be applied.

[0015]

[0033] In some examples, to perform DIMD for a current block, the video coder may perform a gradient calculation to derive one or more possible modes (e.g., M1 and M2). The video coder may then predict the current block using each of the derived one or more possible modes to generate an intermediate predictive block and generate an output prediction according to the intermediate predictive block. Details of an example DIMD workflow are as follows.

[0016]

[0034] The video coder may perform gradient calculations on reconstructed samples of neighboring blocks. To derive an intra prediction mode for a block, the video coder may select a set of neighboring pixels from neighboring reconstructed luma samples, as shown in FIG. 5. The video coder may then apply the gradient calculation to a center pixel of every 3×3 window formed by the set of neighboring pixels. Note that if a neighboring pixel is not reconstructed, its gradient value may not be calculated.

[0017]

[0035] The video coder may perform gradient calculations using a Sobel filter (denoted as "Mx", "My"). Dot generation between these two filters and each 3x3 window (denoted as "W") may be performed to derive horizontal and vertical gradients (denoted as "Gx", "Gy"), respectively. The following may be examples of such filters:

[0018]

number

[0019]

[0036] The video coder may map the gradient values ​​to directions. For example, the video coder may map G x and G y can be used to derive the intensity (G) and orientation (O) for each window.

[0020]

number

[0021]

[0037] In some examples, to reduce the computational cost of the arctangent operation ("atan"), the orientation may be represented by an index value (in the range of 2 to 66) using a mapping table "atan", which may be estimated by comparing Gy / Gx with the mapping table, and G y / G x If atan[i], atan[i+1] is in the range (atan[i], atan[i+1]), then the orientation is assigned the value "i". Note that the intensity G is 0 and O is assigned to 0 by default (planar mode). Figure 6 is a graph showing an example of orientation index mapping using horizontal and vertical gradients.

[0022]

[0038] In the example of FIG. 6, for a given 3×3 window, it (eg, the index values) satisfies:

[0023]

number

[0024]

[0039] The orientation may be mapped to a prediction direction 60 .

[0025]

[0040] The video coder may perform a selection of the two most likely modes. The video coder may accumulate intensity values ​​for each orientation index of all 3x3 windows. The video coder may select the top two directions with the highest sums as the two most likely modes (the mode with the highest sum is denoted as the first mode "M1" and the second highest as the second mode "M2"). Note that if the values ​​are all 0, the planar mode is selected. Figure 7 is a graph illustrating the selection of the two most likely prediction modes. In the example of Figure 7, 18 and 24 are the first and second highest sums of amplitude, respectively, so the video coder may select mode 18 in the first mode M1 and mode 24 as the second mode M2.

[0026]

[0041] The video coder may perform DIMD prediction. As shown in FIG. 8, if the sum of the amplitudes of the second most likely mode is 0 (e.g., Σamplitude[M2]==0), the video coder may perform regular intra prediction, which may be performed in mode M1; otherwise, the video coder may generate an output prediction block as a weighted sum of three prediction blocks (M1, M2, and the planar mode). This is sometimes referred to as performing mixed prediction (e.g., because modes are mixed to generate a single prediction). As an example, the video coder may generate weights for each of the prediction blocks (e.g., ω1 for M1, ω2 for M2, and ω3 for the planar mode) according to the following equation:

[0027]

number

[0028]

[0042] The video coder may generate intermediate prediction blocks (e.g., Pred1 for M1, Pred2 for M2, and Pred3 for planar mode) based on the reference pixels. The video coder may apply weights to the intermediate prediction blocks to generate output prediction blocks according to the following equations:

[0029]

number

[0030]

[0043] A video coder may perform signaling of a DIMD mode. Figure 9A is a flow diagram illustrating an example intra-coding process for VVC, and Figure 9B is a modification to the process of Figure 9A when DIMD is included. As shown in Figure 9B, a video decoder may parse a DIMD flag. If the DIMD flag is true (e.g., has a value of 1), the video decoder may derive an intra-prediction mode and perform prediction as described above. If the DIMD flag is false (e.g., has a value of 0), the video decoder may parse an intra-prediction mode from the bitstream (e.g., build an MPM list and signal an index into the MPM list) and perform prediction accordingly. Thus, in the example of Figure 9B, if the DIMD flag is false, the video decoder may not perform DIMD intra-mode derivation.

[0031]

[0044] The above-described DIMD mechanism may exhibit one or more drawbacks. For example, the potential of DIMD may not be fully utilized for several reasons. For example, DIMD prediction implicitly determines whether prediction is a mixed prediction from multiple modes or from a single mode. The above-described DIMD mechanism may sacrifice robustness, where the optimal prediction mode is a DIMD-derived mode, but the optimal prediction may be from only a single prediction. For another example, in other cases, the optimal intra-mode may differ from the DIMD-derived mode, but the difference is small (one or two index differences). Using normal mode index coding requires more bits, while using a DIMD-derived mode does not lead to the best RD performance.

[0032]

[0045] According to one or more techniques of this disclosure, a video coder (e.g., a video encoder and / or a video decoder) may insert a DIMD derivation mode into an MPM list. Accordingly, the video coder may code a block using the DIMD derivation mode in the MPM list for intra prediction.

[0033]

[0046] 10 is a flow diagram illustrating an example technique for intra-block decoding using DIMD most probable mode (MPM) list building in accordance with one or more techniques of this disclosure. A comparison of FIG. 10 with FIG. 9B reveals some differences. For example, compared to the JVET DIMD design (FIG. 9), a video coder implementing the techniques of this disclosure (FIG. 10) may perform DIMD mode derivation regardless of whether the current block is predicted using a DIMD mode, and the derived mode is added to the MPM list (the MPM list building process is therefore postponed until after the DIMD process).

[0034]

[0047] For blocks with a DIMD flag equal to true, the video coder may perform DIMD prediction as described above. For blocks with a DIMD flag equal to false, the video coder may perform normal intra prediction and add a DIMD derivation mode into the MPM list. Thus, the video coder may use the DIMD derivation mode for prediction for blocks with an MPM flag equal to true.

[0035]

[0048] By implementing the technique of FIG. 10, a video coder can further expand the potential of DIMD and contribute to improved coding efficiency, and a block can perform normal prediction by using a DIMD derivation mode and selecting a DIMD derivation mode (or a DIMD derivation mode with an offset) in the MPM list.

[0036]

[0049] 11 is a flow diagram illustrating an example technique for MPM list construction / derivation in accordance with one or more techniques of this disclosure. The technique of FIG. 11 may be implemented by a video coder, such as video encoder 200 and / or video decoder 300.

[0037]

[0050] As shown in FIG. 11 , in step 1 (1102), the video coder may derive a list of intra modes using reconstructed samples of neighboring blocks via DIMD. In step 2 (1104), the video coder may add prediction modes from neighboring blocks to the MPM list. In step 3 (1106), the video coder may add the list of intra modes derived by DIMD to the MPM list. In step 4 (1108), the video coder may use the list of candidates to add additional candidates to the MPM list. An exemplary method is to add multiple offsets (in the range of -3 to 3) to all candidates in the list or to some of the candidates in the list (e.g., the first three candidates). In step 5 (1110), the video coder may add (e.g., insert) a default intra mode (such as a DC, planar, horizontal, or vertical mode) to the MPM list.

[0051] 11 indicates a step in which the video coder may insert, into the MPM list and after at least one intra mode from the derived list of intra modes, an additional intra mode candidate, which may be one or more default candidates. Additionally or alternatively, step 2 may indicate a step in which the video coder may insert, into the MPM list and before at least one intra mode from the derived list of intra modes, one or more intra mode candidates that are prediction modes from neighboring blocks of the current block.

[0038]

[0052] 12 is a flow diagram illustrating an example technique for deriving a list of intra modes via DIMD, according to one or more techniques of this disclosure. The technique of FIG. 12 may be implemented by a video coder, such as video encoder 200 and / or video decoder 300. The technique of FIG. 12 may be an example of step 1 (1102) of the technique of FIG. 11.

[0039]

[0053] At 1202, the video coder may calculate horizontal and vertical gradient values ​​for each window of neighboring blocks as Gx and Gy. FIG. 5 shows example windows. At 1204, for each set of horizontal and vertical gradient values, the video coder may derive an intensity value (|Gx| + |Gy|) and an orientation value (Gy / Gx) and map each orientation to an intra mode within the range of 2 to 66 (an example process is given above). The video coder may also calculate the intensity value as the sum of the absolute value of the horizontal gradient value and the absolute value of the vertical gradient value, and the intensity value may also be calculated as the sum of the squared value of the horizontal gradient value and the squared value of the vertical gradient value. At 1206, for each intra mode, the video coder may accumulate its corresponding intensity value. At 1208, the video coder may sort the intra modes according to the accumulated intensity value from high to low. The DIMD list may be a sorted list of intra modes or may include only a portion of the list. The DIMD list can filter out intra modes with a sum of intensity values ​​equal to 0. The DIMD list can filter out intra modes with a sum of intensity values ​​less than a threshold. The size of the list can be 0, 1, 2, or more. The first candidate can be set to DC or planar mode if all sums of intensity values ​​are 0.

[0040]

[0054] 11, the video coder may add the intra-prediction modes of neighboring blocks into the MPM list at 1104. Exemplary neighboring blocks are the left, top, top-left, top-right, and bottom-left blocks, as shown in FIG.

[0041]

[0055] 14 is a flow diagram illustrating an example technique for adding a DIMD derivation mode into an MPM list in accordance with one or more techniques of this disclosure. The technique of FIG. 14 may be implemented by a video coder, such as video encoder 200 and / or video decoder 300. The technique of FIG. 14 may be an example of step 3 of the technique of FIG. 11.

[0042]

[0056] At 1402, the video coder may add a first candidate with the highest sum of intensities (denoted as "M1" as described above) into the MPM list. At 1404, the video coder may determine whether a sum of intensities of a second candidate (denoted as "M2" as described above) is 0, and if it is determined to be 0, the second candidate may be skipped; otherwise, 1406 is performed. At 1406, the video coder may add the second candidate into the MPM list.

[0043]

[0057] Some exemplary variations and / or alternatives are as follows: 1) At 1404, the video coder may determine whether the sum of intensities of the second candidate is less than a threshold. If it is less than the threshold, the video coder may skip the second candidate; otherwise, the video coder may add the second candidate during MPM list construction. 2) The condition in 1404 may also be applied to the first candidate. 3) The order of the techniques in Figure 11 may be swapped with each other or in an interleaved manner. For example, 1106 may be performed before 1104, or DIMD-derived modes and intra modes from neighboring blocks may be added in an interleaved manner. 4) When the coder performs 1104 before 1102, the list of intra modes derived by the DIMD may be pruned by intra modes from neighboring blocks, for example, if an intra mode was already added to the MPM list in 1104, the intra mode may be skipped when creating the list of intra modes for the DIMD list. 5) In 4), if an intra mode has already been added to the MPM list in 1104, the mode and offset (offset value can be -3 to 3) equal to the intra mode is skipped when creating the list of intra modes in the DIMD list. 6) The list of intra-modes derived by DIMD can also be sorted in a different order (e.g., sum of intensity values ​​from low to high, and keeping the last few candidates). 7) Each candidate added in the MPM list may be pruned to avoid duplicate modes being added in the MPM list. 8) The first candidate may be skipped if it is equal to a DC or planar mode.

[0044]

[0058] Some other exemplary variations and / or alternatives are as follows: 1) The DIMD flag can be signaled after the MPM flag 2) The DIMD flag can be signaled as one of the MPM indices 3) There can be only one mode derived by DIMD added in the MPM list. 4) There can be more than two modes derived by DIMD that are added to the MPM list. 5) DIMD can be applied to chroma blocks as well 6) DIMD derivation modes can also be added in the chroma MPM list 7) Intra prediction can always use a single prediction mode 8) In case 7), the DIMD flag may not be signaled. 9) DIMD prediction may only use a single mode 10) DIMD predictions can be mixed predictions of derived and planar modes 11) DIMD predictions can be mixed predictions of derived mode(s) and DC modes 12) DIMD may use predicted samples instead of reconstructed samples for mode derivation 13) If a block is of DIMD mode, its prediction mode derived by DIMD may be used for MPM list construction of neighboring blocks. 14) If the block is of DIMD mode, the default mode (DC or Planar) may be used for building the MPM list of neighboring blocks.

[0045]

[0059] 1 is a block diagram illustrating an example video encoding and decoding system 100 that may implement techniques of this disclosure. The techniques of this disclosure are generally directed to coding (encoding and / or decoding) video data. Generally, the video data includes some data for processing the video. Thus, the video data may include raw uncoded video, coded video, decoded (e.g., reconstructed) video, and video metadata, such as signaling data.

[0046]

[0060] 1, system 100 includes a source device 102 that, in this example, provides encoded video data to be decoded and displayed by a destination device 116. 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, mobile devices, tablet computers, set-top boxes, telephone handsets such as smartphones, televisions, cameras, display devices, digital media players, video gaming consoles, video streaming devices, broadcast receiver devices, etc. In some cases, source device 102 and destination device 116 may be equipped for wireless communication and therefore may be referred to as wireless communication devices.

[0047]

[0061] In the example of FIG. 1 , source device 102 includes video source 104, memory 106, video encoder 200, and output interface 108. Destination device 116 includes input interface 122, video decoder 300, memory 120, and display device 118. According to this disclosure, video encoder 200 of source device 102 and video decoder 300 of destination device 116 may be configured to apply techniques for intra-mode derivation for most probable mode list construction. 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, the source device and destination device 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.

[0048]

[0062] The system 100 shown in FIG. 1 is merely an example. In general, any digital video encoding and / or decoding device may implement techniques for intra-mode derivation for most probable mode list construction. Source device 102 and destination device 116 are merely examples of coding devices, such that source device 102 generates coded video data for transmission to destination device 116. This disclosure refers to a “coding” device as a device that performs coding (encoding and / or decoding) of data. Accordingly, video encoder 200 and video decoder 300 represent examples of coding devices, specifically, video encoders and video decoders, respectively. In some examples, source device 102 and destination device 116 may operate substantially symmetrically, such that each of source device 102 and destination device 116 includes video encoding and video decoding components. Thus, system 100 may support one-way or two-way video transmission between source device 102 and destination device 116, for example, video streaming, video playback, video broadcasting, or video telephony.

[0049]

[0063] Generally, 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 video encoder 200, which encodes the data for the pictures. Video source 104 of source device 102 may include a video capture device, such as a video camera, a video archive containing previously captured live video, and / or a video feed interface for receiving video from a video content provider. As a further alternative, video source 104 may generate computer-graphics-based data as source video, or a combination of live, archived, and computer-generated video. In each case, video encoder 200 encodes the captured, pre-captured, or computer-generated video data. Video encoder 200 may rearrange the pictures from their received order (sometimes referred to as “display order”) into a coding order for coding. Video encoder 200 may generate a bitstream including the encoded video data. Source device 102 may then output the encoded video data onto computer-readable medium 110 via output interface 108 for receipt and / or retrieval by, for example, input interface 122 of destination device 116.

[0050]

[0064] Memory 106 of source device 102 and memory 120 of destination device 116 represent general-purpose memory. In some examples, memory 106, 120 may store raw video data, e.g., raw video from video source 104 and raw decoded video data from video decoder 300. Additionally or alternatively, memory 106, 120 may store software instructions executable by video encoder 200 and video decoder 300, respectively, for example. While memory 106 and memory 120 are shown separate from video encoder 200 and video decoder 300 in this example, it should be understood that video encoder 200 and video decoder 300 may also include internal memory for functionally similar or equivalent purposes. Additionally, memory 106, 120 may store encoded video data, e.g., output from video encoder 200 and input to video decoder 300. In some examples, portions of the memory 106, 120 may be allocated as one or more video buffers, for example, to store raw decoded and / or encoded video data.

[0051]

[0065] 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 in accordance with 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 in facilitating communication from the source device 102 to the destination device 116.

[0052]

[0066] 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.

[0053]

[0067] In some examples, source device 102 may output the encoded video data to 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.

[0054]

[0068] 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 file transfer protocol services (e.g., 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.

[0055]

[0069] Destination device 116 may access the encoded video data from 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 file server 114. 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 file server 114, or other such protocols for retrieving media data.

[0056]

[0070] Output interface 108 and 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 output interface 108 and input interface 122 comprise wireless components, output interface 108 and 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 output interface 108 comprises a wireless transmitter, output interface 108 and input interface 122 may be configured to transfer data, such as encoded video data, according to other wireless standards, such as the IEEE 802.11 specification, the IEEE 802.15 specification (e.g., ZigBee), the Bluetooth standard, etc. In some examples, source device 102 and / or destination device 116 may include respective system-on-chip (SoC) devices. For example, the source device 102 may include an SoC device for performing functions attributed to the video encoder 200 and / or the output interface 108, and the destination device 116 may include an SoC device for performing functions attributed to the video decoder 300 and / or the input interface 122.

[0057]

[0071] 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.

[0058]

[0072] The input interface 122 of the destination device 116 receives the encoded video bitstream from the computer-readable medium 110 (e.g., a communication medium, a storage device 112, a file server 114, etc.). The encoded video bitstream may include signaling information defined by the video encoder 200 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 liquid crystal display (LCD), a plasma display, an organic light-emitting diode (OLED) display, or another type of display device.

[0059]

[0073] 1, in some examples, video encoder 200 and video decoder 300 may each be integrated with an audio encoder and / or 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).

[0060]

[0074] 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. Devices including the video encoder 200 and / or the video decoder 300 may comprise integrated circuits, microprocessors, and / or wireless communication devices such as cellular phones.

[0061]

[0075] 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 draft of the VVC standard is set forth in Bross et al., "Versatile Video Coding (Draft 10)," Joint Video Experts Team (JVET) of ITU-T SG16 WP3 and ISO / IEC JTC1 / SC29 / WG11, 20th Meeting, Teleconference, October 7-16, 2020, JVET-T2001-v2 (hereinafter, "VVC Draft 10"). However, the techniques of this disclosure are not limited to any particular coding standard.

[0062]

[0076] 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 containing data to be processed (e.g., encoded, decoded, or otherwise used in the encoding and / or decoding process). For example, a block may include a two-dimensional matrix of luminance and / or chrominance data samples. Generally, the video encoder 200 and the video decoder 300 may code video data represented in YUV (e.g., Y, Cb, Cr) format. That is, rather than coding red, green, and blue (RGB) data for a picture sample, 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-formatted 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.

[0063]

[0077] This disclosure may generally refer to coding (e.g., encoding and decoding) a picture to include the process of encoding or decoding data for a picture. Similarly, this disclosure may refer to coding a block of a picture to include the process 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 the partitioning of a picture into blocks. Thus, references to coding a picture or a block should generally be understood as coding values ​​for the syntax elements that form the picture or block.

[0064]

[0078] 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 child nodes may be referred to as 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 partitioning 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.

[0065]

[0079] As another example, video encoder 200 and video decoder 300 may be configured to operate according to VVC. According to VVC, a video coder (such as video encoder 200) partitions a picture into multiple coding tree units (CTUs). 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 quad-tree partitioning and a second level partitioned according to binary tree partitioning. The root node of the QTBT structure corresponds to a CTU. The leaf nodes of the binary tree correspond to coding units (CUs).

[0066]

[0080] In the MTT partitioning structure, blocks may be partitioned using quad tree (QT) partitioning, binary tree (BT) partitioning, and one or more types of triple tree (TT) (also called ternary tree (TT)) partitioning. Triple tree or ternary tree partitioning is a partitioning in which a block is split into three sub-blocks. In some examples, triple tree or ternary tree partitioning divides a block into three sub-blocks without splitting the original block through the center. The partitioning types in MTT (e.g., QT, BT, and TT) can be symmetric or asymmetric.

[0067]

[0081] 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).

[0068]

[0082] Video encoder 200 and video decoder 300 may be configured to use quadtree partitioning, QTBT partitioning, MTT partitioning, or other partition structures according to HEVC. For illustrative purposes, 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.

[0069]

[0083] In some examples, a CTU includes a coding tree block (CTB) of luma samples, two corresponding CTBs of chroma samples for a picture with three sample arrays, or a CTB of samples for a monochrome picture, or a picture coded using three separate color planes and syntax structures used to code the samples. The CTB may be an N×N block of samples, for some value of N such that the division of the components into the CTB is partitioned. A component is an array or a single sample from one of three arrays (luma and two chroma) that configure the picture in 4:2:0, 4:2:2, or 4:4:4 color format, or an array or a single sample of an array that configures the picture in monochrome format. In some examples, a coding block is an M×N block of samples, for some value of M and N such that the division of the CTB into coding blocks is partitioned.

[0070]

[0084] Blocks (e.g., CTUs or CUs) may be grouped in various ways in a picture. As an example, a brick may refer to a rectangular region of a CTU row within a particular tile in a picture. A tile may be a rectangular region of a CTU within a particular tile column and a particular tile row in a picture. A tile column refers to a rectangular region of a CTU having a height equal to the height of the picture and a width specified by a syntax element (e.g., in a picture parameter set). A tile row refers to a rectangular region of a CTU having a height specified by a syntax element (e.g., in a picture parameter set) and a width equal to the width of the picture.

[0071]

[0085] In some examples, a tile may be partitioned into multiple bricks, each of which may contain one or more CTU rows within the tile. A tile that is not partitioned into multiple bricks may also be referred to as a brick. However, a brick that is a true subset of a tile may not be referred to as a tile.

[0072]

[0086] The bricks in a picture may also be arranged into slices. A slice may be an integer number of bricks of a picture that may be contained entirely in a single Network Abstraction Layer (NAL) unit. In some examples, a slice includes either several complete tiles or only a continuous sequence of complete bricks of one tile.

[0073]

[0087] This disclosure may use "N x N" and "N by N" interchangeably to refer to the sample dimensions of a block (such as a CU or other video block) in terms of the vertical and horizontal dimensions, e.g., 16 x 16 samples or 16 by 16 samples. Generally, a 16 x 16 CU has 16 samples in the vertical direction (y = 16) and 16 samples in the horizontal direction (x = 16). Similarly, an N x N CU generally has N samples in the vertical direction and N samples in the horizontal direction, where N represents a non-negative integer value. 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 N x M samples, where M is not necessarily equal to N.

[0074]

[0088] Video encoder 200 encodes video data for a CU, which represents prediction and / or residual information and 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 the samples of the CU prior to encoding and the predictive block.

[0075]

[0089] 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 motion search to identify a reference block that closely matches the CU, e.g., 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), a sum of squared differences (SSD), a mean absolute difference (MAD), a 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 prediction or bidirectional prediction.

[0076]

[0090] Some examples of VVC 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.

[0077]

[0091] To perform intra prediction, video encoder 200 may select an intra prediction mode to generate a predicted block. Some examples of VVC provide 67 intra prediction modes, including various directional modes, as well as planar and DC modes. Generally, 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, above-left, 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).

[0078]

[0092] 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.

[0079]

[0093] Following prediction, such as intra-prediction or inter-prediction, of a block, the video encoder 200 may calculate residual data for the block. The residual data, such as a residual block, represents 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. Furthermore, the video encoder 200 may apply a secondary transform, such as a mode-dependent non-separable secondary transform (MDNSST), a signal-dependent transform, or a Karhunen-Loeve transform (KLT), following the first transform. The video encoder 200 produces transform coefficients following application of the one or more transforms.

[0080]

[0094] As described 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 transform coefficients are quantized to possibly reduce the amount of data used to represent the transform coefficients, thereby providing further compression. By performing the quantization process, the video encoder 200 may reduce the bit depth associated with some or all of the transform 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.

[0081]

[0095] Following quantization, the video encoder 200 may scan the transform coefficients to create a one-dimensional vector from a two-dimensional matrix including the quantized transform coefficients. The scan may be designed to place higher energy (and therefore lower frequency) transform coefficients at the front of the vector and lower energy (and therefore higher frequency) transform coefficients at the back of the vector. In some examples, the video encoder 200 may utilize a predefined scan order to scan the quantized transform coefficients to create a serialized vector and then entropy code the quantized transform coefficients of the vector. In other examples, the video encoder 200 may perform adaptive scanning. 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.

[0082]

[0096] To implement CABAC, 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 values. A probability determination may be based on the context assigned to the symbol.

[0083]

[0097] 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, a block header, a slice header, or other syntax data, such as a sequence parameter set (SPS), a picture parameter set (PPS), or a video parameter set (VPS). Video decoder 300 may similarly decode such syntax data to determine how to decode corresponding video data.

[0084]

[0098] In this manner, video encoder 200 may generate a bitstream including syntax elements that describe encoded video data, e.g., partitions of a picture into blocks (e.g., CUs) and prediction and / or residual information for the blocks. Finally, video decoder 300 may receive the bitstream and decode the encoded video data.

[0085]

[0099] Generally, video decoder 300 performs an inverse process to that performed by video encoder 200 to decode encoded video data of a bitstream. For example, video decoder 300 may decode values ​​for syntax elements of a bitstream using CABAC in a manner that is reverse to, but substantially similar to, the CABAC encoding process of video encoder 200. The syntax elements may define partition information for partitioning a picture into CTUs and the partitioning of each CTU according to a corresponding partition structure, such as a QTBT structure, to define CUs of the CTU. The syntax elements may further define prediction and residual information for blocks of video data (e.g., CUs).

[0086]

[0100] 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 the predictive block and the residual block (sample by sample) 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.

[0087]

[0101] According to one or more techniques of this disclosure, a video coder (e.g., a video encoder and / or a video decoder) may insert a DIMD derivation mode into an MPM list. Accordingly, the video coder may code a block using the DIMD derivation mode in the MPM list for intra prediction.

[0088]

[0102] This disclosure may generally refer to “signaling” certain information, such as syntax elements. 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 mentioned 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 to storage device 112 for later retrieval by destination device 116.

[0089]

[0103] According to one or more techniques of this disclosure, the encoder 200 and / or the decoder 300 may insert one or more derived DIMD modes into an MPM list. For example, the encoder 200 and / or the decoder 300 may implement the technique of FIG. 10.

[0090]

[0104] 2A and 2B are conceptual diagrams illustrating an exemplary quad-tree binary tree (QTBT) structure 130 and a 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, the quad-tree node splits a block horizontally and vertically into four sub-blocks of equal size, so there is no need to indicate the splitting type. 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.

[0091]

[0105] 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 the sample), a minimum quadtree size (MinQTSize, representing the minimum allowable quadtree 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).

[0092]

[0106] The root node of the QTBT structure corresponding to a CTU may have four child nodes at the first level of the QTBT structure, each of which may be partitioned according to quadtree partitioning. That is, a node at the first level is either a leaf node (with no child nodes) or has four child nodes. The example QTBT structure 130 represents a node including a parent node and child nodes with solid lines for branching. If a node at the first level is not larger than the maximum allowable binary tree root node size (MaxBTSize), the node may be further partitioned by its respective binary tree. The binary tree splitting of a node may be repeated until the node resulting from the split reaches the minimum allowable binary tree leaf node size (MinBTSize) or the maximum allowable binary tree depth (MaxBTDepth). The example QTBT structure 130 represents a node with dashed lines for branching. The binary tree leaf nodes are called coding units (CUs), and CUs are used for prediction (e.g., intra-picture or inter-picture prediction) and transform without further partitioning. As explained above, a CU may also be referred to as a "video block" or "block."

[0093]

[0107] In one example of a QTBT partitioning structure, the CTU size is set as 128x128 (luma sample and two corresponding 64x64 chroma samples), MinQTSize is set as 16x16, MaxBTSize is set as 64x64, MinBTSize (for both width and height) is set as 4, and MaxBTDepth is set as 4. Quad-tree partitioning is first applied to the CTU to generate a quad-tree leaf node. The quad-tree leaf node may have a size from 16x16 (i.e., MinQTSize) to 128x128 (i.e., CTU size). If the quad-tree leaf node is 128x128, the leaf quad-tree node is not further split by the binary tree because its size exceeds MaxBTSize (i.e., 64x64 in this example). Otherwise, the quad-tree leaf node is further partitioned by the binary tree. Therefore, the quadtree leaf node is also the root node for the binary tree and has a binary tree depth of 0. When the binary tree depth reaches MaxBTDepth (4 in this example), no further splitting is allowed. A binary tree node with a width equal to MinBTSize (4 in this example) implies that no further vertical splitting (i.e., width division) is allowed for that binary tree node. Similarly, a binary tree node with a height equal to MinBTSize implies that no further horizontal splitting (i.e., height division) is allowed for that binary tree node. As mentioned above, the leaf nodes of the binary tree are called CUs and are further processed according to the prediction and transformation without further division.

[0094]

[0108] 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 limiting of the techniques broadly illustrated and described in this disclosure. For illustrative purposes, this disclosure describes video encoder 200 in accordance with VVC (ITU-T H.266 under development) and HEVC (ITU-T H.265) techniques. However, the techniques of this disclosure may be implemented by video encoding devices configured for other video coding standards.

[0095]

[0109] 3, the video encoder 200 includes a video data memory 230, a mode select 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 select unit 202, the residual generation unit 204, the transform processing unit 206, the quantization unit 208, the inverse quantization unit 210, the inverse transform processing unit 212, the reconstruction unit 214, the filter unit 216, the DPB 218, and the entropy coding unit 220 may be implemented in one or more processors or processing circuits. For example, the units of video encoder 200 may be implemented as one or more circuits or logic elements, as part of a hardware circuit, or as part of a processor, ASIC, or FPGA. Moreover, video encoder 200 may include additional or alternative processors or processing circuits for performing these and other functions.

[0096]

[0110] Video data memory 230 may store video data to be encoded by components of video encoder 200. Video encoder 200 may receive video data stored in video data memory 230, for example, from video source 104 (FIG. 1). DPB 218 may serve as a reference picture memory that stores reference video data for use in predicting subsequent video data by video encoder 200. Video data memory 230 and 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. Video data memory 230 and DPB 218 may be provided by the same memory device or separate memory devices. In various examples, video data memory 230 may be on-chip with other components of video encoder 200, as shown, or off-chip relative to those components.

[0097]

[0111] 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, nor should they be construed as limited 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.

[0098]

[0112] The various units in FIG. 3 are shown to aid in understanding the operations performed by 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 can 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 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 integrated circuits.

[0099]

[0113] Video encoder 200 may include an arithmetic logic unit (ALU), a basic functional unit (EFU), a digital circuit, an analog circuit, and / or a programmable core formed from programmable circuitry. In examples in which the operations of video encoder 200 are implemented using software executed by programmable circuitry, memory 106 (FIG. 1) may store instructions (e.g., object code) of the software that video encoder 200 receives and executes, or another memory (not shown) within video encoder 200 may store such instructions.

[0100]

[0114] The video data memory 230 is configured to store 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.

[0101]

[0115] The mode select unit 202 includes a motion estimation unit 222, a motion compensation unit 224, and an intra prediction unit 226. The mode select unit 202 may include additional functional units for performing video prediction according to other prediction modes. By way of example, the mode select 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.

[0102]

[0116] 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 CTUs into CUs, prediction modes for CUs, transform types for residual data of CUs, quantization parameters for residual data of CUs, etc. Mode selection unit 202 may ultimately select a combination of encoding parameters that has a rate-distortion value that is better than other tested combinations.

[0103]

[0117] Video encoder 200 may partition a picture retrieved from video data memory 230 into a series of CTUs, encapsulating one or more CTUs in a slice. Mode select unit 202 may partition the CTUs of the picture according to a tree structure, such as the QTBT structure or quadtree structure of HEVC described above. As described above, 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.”

[0104]

[0118] Generally, the mode select unit 202 also controls its components (e.g., the motion estimation unit 222, the motion compensation unit 224, and the intra prediction unit 226) to generate a prediction block for the current block (e.g., the current CU, or in HEVC, the overlapping portion of the PU and TU). For inter prediction of the current block, the motion estimation unit 222 may perform a motion search to identify one or more closely matching reference blocks in one or more reference pictures (e.g., one or more previously 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, the sum of absolute differences (SAD), the sum of squared differences (SSD), the mean absolute difference (MAD), the mean squared difference (MSD), etc. The motion estimation unit 222 may generally perform these calculations using sample-by-sample differences between the current block and the reference block under consideration. Motion estimation unit 222 may identify the reference block with the lowest value resulting from these calculations, which indicates the reference block that most closely matches the current block.

[0105]

[0119] The motion estimation unit 222 may form one or more motion vectors (MVs) that define the position of a reference block in a reference picture relative to the position of a current block in the current picture. The motion estimation unit 222 may then provide the motion vectors to the motion compensation unit 224. For example, in 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.

[0106]

[0120] As another example, for intra prediction, or intra-predictive coding, intra prediction unit 226 may generate a predictive block from samples neighboring a current block. For example, in a directional mode, intra prediction unit 226 may generally mathematically combine values ​​of neighboring samples and populate these calculated values ​​in a defined direction across the current block to produce a predictive block. As another example, in a DC mode, intra prediction unit 226 may calculate an average of neighboring samples for the current block and generate a predictive block to include this resulting average for each sample of the predictive block.

[0107]

[0121] The mode select unit 202 provides the predictive 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 predictive block from the mode select unit 202. The residual generation unit 204 calculates sample-by-sample differences between the current block and the predictive 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.

[0108]

[0122] In examples in which mode select unit 202 partitions CUs into PUs, each PU may be associated with a luma prediction unit and a corresponding chroma prediction unit. Video encoder 200 and 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 the size of a particular CU is 2N×2N, 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. Video encoder 200 and video decoder 300 may also support asymmetric partitioning for PU sizes of 2N×nU, 2N×nD, nL×2N, and nR×2N for inter prediction.

[0109]

[0123] In examples where mode select unit 202 does not further partition CUs into PUs, each CU may be associated with a luma coding block and a corresponding chroma coding block. As described above, the size of a CU may refer to the size of the luma coding block of the CU. Video encoder 200 and video decoder 300 may support CU sizes of 2N×2N, 2N×N, or N×2N.

[0110]

[0124] In other video coding techniques, such as intra block copy mode coding, affine mode coding, and linear model (LM) mode coding, as some examples, mode select 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, mode select 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, mode select unit 202 may provide these syntax elements to entropy coding unit 220 to be coded.

[0111]

[0125] As described above, the residual generation unit 204 receives the video data for the 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.

[0112]

[0126] 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 quadratic transform, such as a rotation transform. In some examples, transform processing unit 206 does not apply a transform to the residual block.

[0113]

[0127] 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 select 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 a loss of information, and therefore, the quantized transform coefficients may have lower precision than the original transform coefficients produced by the transform processing unit 206.

[0114]

[0128] Inverse quantization unit 210 and inverse transform processing unit 212 may apply inverse quantization and inverse transform, respectively, to the quantized transform coefficient block to reconstruct a residual block from the transform coefficient block. 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 select 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 select unit 202 to produce the reconstructed block.

[0115]

[0129] 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. In some examples, the operations of filter unit 216 may be skipped.

[0116]

[0130] Video encoder 200 stores the reconstructed blocks in DPB 218. For example, in examples where the operations of filter unit 216 are not performed, reconstruction unit 214 may store the reconstructed blocks in DPB 218. In examples where the operations of filter unit 216 are performed, filter unit 216 may store the filtered reconstructed blocks in DPB 218. Motion estimation unit 222 and motion compensation unit 224 may retrieve reference pictures formed from the reconstructed (and potentially filtered) blocks from DPB 218 to inter-predict blocks of a later-encoded picture. Furthermore, intra-prediction unit 226 may use the reconstructed blocks in DPB 218 of the current picture to intra-predict other blocks in the current picture.

[0117]

[0131] Generally, entropy encoding unit 220 may entropy encode syntax elements received from other functional components of video encoder 200. For example, entropy encoding unit 220 may entropy encode quantized transform coefficient blocks from quantization unit 208. As another example, 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 mode select unit 202. 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, 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, entropy encoding unit 220 may operate in a bypass mode in which syntax elements are not entropy coded.

[0118]

[0132] 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.

[0119]

[0133] The operations described above are described with respect to blocks. Such descriptions should be understood as operations for luma coding blocks and / or chroma coding blocks. As described above, in some examples, the luma coding blocks and chroma coding blocks are 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.

[0120]

[0134] In some examples, operations performed with respect to luma coding blocks need not be repeated for chroma coding blocks. As one example, operations for identifying motion vectors (MVs) and reference pictures for luma coding blocks need not be repeated to identify MVs and reference pictures for chroma blocks. Rather, MVs for luma coding blocks may be scaled to determine MVs for chroma blocks, and the reference pictures may be the same. As another example, the intra prediction process may be the same for luma coding blocks and chroma coding blocks.

[0121]

[0135] Video encoder 200 represents an example of a device configured to encode video data, including a memory configured to store the video data and one or more processing units implemented in a circuit, the one or more processing units configured to: derive a list of intra modes for a current block of video data using decoder-side intra mode derivation (DIMD) and using reconstructed samples of neighboring blocks; construct a most probable mode (MPM) list for the current block that includes at least one intra mode from the derived list of intra modes; and predict the current block using a candidate selected from the constructed MPM list.

[0122]

[0136] 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 (ITU-T H.266 under development) and HEVC (ITU-T H.265) techniques. However, the techniques of this disclosure may be implemented by video coding devices configured for other video coding standards.

[0123]

[0137] 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. For example, the units of the video decoder 300 may be implemented as one or more circuits or logic elements, as part of a hardware circuit, or as part of a processor, ASIC, or FPGA. Moreover, the video decoder 300 may include additional or alternative processors or processing circuits for performing these and other functions.

[0124]

[0138] 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.

[0125]

[0139] CPB memory 320 may store video data, such as an encoded video bitstream, to be decoded by components of video decoder 300. The video data stored in CPB memory 320 may be retrieved, for example, from computer-readable medium 110 (FIG. 1). CPB memory 320 may include a CPB that stores encoded video data (e.g., syntax elements) from the encoded video bitstream. CPB memory 320 may also store video data other than syntax elements of coded pictures, such as temporary data representing output from various units of video decoder 300. DPB 314 generally stores decoded pictures that video decoder 300 may output and / or use as reference video data when decoding subsequent data or pictures of the encoded video bitstream. CPB memory 320 and DPB 314 may be formed by any of a variety of memory devices, such as DRAM, including SDRAM, MRAM, RRAM, or other types of memory devices. 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.

[0126]

[0140] 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 in conjunction 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.

[0127]

[0141] The various units shown in FIG. 4 are shown to aid in understanding the operations performed by 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 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.

[0128]

[0142] 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.

[0129]

[0143] 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.

[0130]

[0144] Generally, video decoder 300 reconstructs a picture on a block-by-block basis. Video decoder 300 may perform a reconstruction operation on each block individually (where the block currently being reconstructed, i.e., decoded, may be referred to as the “current block”).

[0131]

[0145] The entropy decoding unit 302 may entropy decode syntax elements defining the quantized transform coefficients of a quantized transform coefficient block, as well as transform information such as a quantization parameter (QP) and / or a transform mode indication(s). The inverse quantization unit 306 may use the QP associated with the quantized transform coefficient block to determine the degree of quantization and, similarly, the degree of inverse quantization to 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.

[0132]

[0146] After the inverse quantization unit 306 forms the transform coefficient blocks, the inverse transform processing unit 308 may apply one or more inverse transforms to the transform coefficient blocks to generate residual blocks 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 transform coefficient blocks.

[0133]

[0147] 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 the 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 the inter-prediction process in a manner substantially similar to that described with respect to motion compensation unit 224 (FIG. 3).

[0134]

[0148] As another example, if the prediction information syntax element indicates that the current block is intra-predicted, intra prediction unit 318 may generate a predictive block according to the intra-prediction mode indicated by the prediction information syntax element. Again, intra prediction unit 318 may generally perform the intra-prediction process in a manner substantially similar to that described with respect to intra prediction unit 226 (FIG. 3). Intra prediction unit 318 may retrieve data of neighboring samples for the current block from DPB 314.

[0135]

[0149] 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.

[0136]

[0150] Filter unit 312 may perform one or more filter operations on the reconstructed blocks. For example, filter unit 312 may perform a deblocking operation to reduce blockiness artifacts along the edges of the reconstructed blocks. The operations of filter unit 312 may not be performed in all instances.

[0137]

[0151] The video decoder 300 may store the reconstructed blocks in the DPB 314. For example, in examples where the operations of filter unit 312 are not performed, reconstruction unit 310 may store the reconstructed blocks in the DPB 314. In examples where the operations of filter unit 312 are performed, filter unit 312 may store the filtered 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 (e.g., decoded video) from the DPB 314 for subsequent presentation on a display device, such as display device 118 of FIG. 1.

[0138]

[0152] 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, the one or more processing units configured to: derive a list of intra modes for a current block of video data using decoder-side intra mode derivation (DIMD) and using reconstructed samples of neighboring blocks; construct a most probable mode (MPM) list for the current block that includes at least one intra mode from the derived list of intra modes; and predict the current block using a candidate selected from the constructed MPM list.

[0139]

[0153] 15 is a flowchart illustrating an example method for encoding a current block in accordance with the techniques of this disclosure. The current block may comprise a current CU. Although described with respect to video encoder 200 (FIGS. 1 and 3), it should be understood that other devices may be configured to implement a method similar to that of FIG.

[0140]

[0154] In this example, video encoder 200 first predicts the current block (350). For example, video encoder 200 may form a predictive block for the current block. Video encoder 200 may then calculate a residual block for the current block (352). To calculate the residual block, video encoder 200 may calculate the difference between the original uncoded block and the predictive block for the current block. Video encoder 200 may then transform the residual block and quantize the transform coefficients of the residual block (354). Next, video encoder 200 may scan the quantized transform coefficients of the residual block (356). During or following the scan, video encoder 200 may entropy code the transform coefficients (358). For example, video encoder 200 may code the transform coefficients using CAVLC or CABAC. Video encoder 200 may then output entropy-coded data for the block (360).

[0141]

[0155] 16 is a flowchart illustrating an example method for decoding a current block of video data in accordance with the techniques of this disclosure. The current block may comprise a current CU. Although described with respect to video decoder 300 (FIGS. 1 and 4), it should be understood that other devices may be configured to implement a method similar to that of FIG.

[0142]

[0156] The video decoder 300 may receive entropy-coded data for the current block, such as entropy-coded prediction information and entropy-coded data for the transform coefficients of the residual block corresponding to the current block (370). The video decoder 300 may entropy decode the entropy-coded data to determine prediction information for the current block and to reconstruct the transform coefficients of the residual block (372). The video decoder 300 may predict the current block, e.g., using the intra-prediction or inter-prediction mode indicated by the prediction information for the current block, to calculate a predictive block for the current block (374). The video decoder 300 may then inverse scan the reconstructed transform coefficients to create a block of quantized transform coefficients (376). The video decoder 300 may then dequantize the transform coefficients and apply an inverse transform to the transform coefficients to produce a residual block (378). The video decoder 300 may finally decode the current block by combining the predictive block and the residual block (380).

[0143]

[0157] 17 is a flowchart illustrating an example technique for encoding video data using DIMD, in accordance with one or more techniques of this disclosure. Although described with respect to video encoder 200 (FIGS. 1 and 3), it should be understood that other devices may be configured to implement a method similar to that of FIG.

[0144]

[0158] Video encoder 200 may derive a list of decoder-side intra mode derivation (DIMD) intra modes for a current block of video data using reconstructed samples of neighboring blocks (1702). For example, intra prediction unit 226 may derive the DIMD intra modes using the techniques described above with reference to FIG. 7 to obtain a first DIMD intra mode M1 and a second DIMD intra mode M2.

[0145]

[0159] Video encoder 200 may construct a most probable mode (MPM) list for the current block that includes at least one intra-mode from the DIMD modes (1704). For example, intra-prediction unit 226 may construct the MPM list using the techniques described above with reference to Figure 11. The constructed MPM list may include one or both of a first DIMD intra-mode M1 and a second DIMD intra-mode M2.

[0146]

[0160] Video encoder 200 may determine whether to predict the current block using DIMD (1706). For example, mode select unit 202 may perform analysis to determine an optimal coding mode for the current block (e.g., a coding mode that uses the fewest bits to represent the current block). To determine the optimal coding mode, mode select unit 202 may test encoding the current block using various modes. If mode select unit 202 determines that encoding the current block using DIMD is optimal, mode select unit 202 may decide to encode the current block using DIMD. Similarly, if mode select unit 202 determines to encode the current block using one of the derived DIMD modes in the MPM list, mode select unit 202 may decide not to encode the current block using DIMD.

[0147]

[0161] Video encoder 200 may encode an indication of whether the current block is predicted using DIMD. For example, entropy encoding unit 220 may encode, for the current block, a DIMD flag having a value indicating whether DIMD is enabled for the current block of video data. As an example, in response to determining not to predict the current block using DIMD (the “No” branch of 1706), video encoder 200 may encode the DIMD flag with a false (e.g., 0) value to indicate that the current block is not predicted using DIMD (1708). As another example, in response to determining to predict the current block using DIMD (the “Yes” branch of 1706), video encoder 200 may encode the DIMD flag with a true (e.g., 1) value to indicate that the current block is predicted using DIMD (1714).

[0148]

[0162] Video encoder 200 may encode one or more syntax elements that indicate a selected intra mode from the MPM list (1710). For example, entropy encoding unit 220 may encode a syntax element having a value that indicates an index in the MPM list of the selected intra mode.

[0149]

[0163] In some examples, as described above, video encoder 200 may include a reconstruction loop in which blocks of video data are reconstructed to be used as references when predicting subsequent blocks. As an example, if the current block is not predicted using DIMD, video encoder 200 may predict the current block using a selected intra mode (1712). For example, intra prediction unit 226 may generate a predictive block using samples in the direction specified by the selected intra mode. As another example, if the current block is predicted using DIMD, video encoder 200 may predict the current block using DIMD (1716). For example, intra prediction unit 226 may predict the current block using the techniques described above with reference to FIG. 8.

[0150]

[0164] 18 is a flowchart illustrating an example technique for decoding video data using DIMD, in accordance with one or more techniques of this disclosure. Although described with respect to video decoder 300 (FIGS. 1 and 4), it should be understood that other devices may be configured to implement a method similar to that of FIG.

[0151]

[0165] The video decoder 300 may derive a list of decoder-side intra mode derivation (DIMD) intra modes for a current block of video data using reconstructed samples of neighboring blocks (1802). For example, the intra prediction unit 318 may derive the DIMD intra modes using the techniques described above with reference to FIG. 7 to obtain a first DIMD intra mode M1 and a second DIMD intra mode M2.

[0152]

[0166] The video decoder 300 may construct a most probable mode (MPM) list for the current block that includes at least one intra-mode from the DIMD modes (1804). For example, the intra-prediction unit 318 may construct the MPM list using the techniques described above with reference to Figure 11. The constructed MPM list may include one or both of the first DIMD intra-mode M1 and the second DIMD intra-mode M2.

[0153]

[0167] The video decoder 300 may determine whether to predict the current block using DIMD (1806). For example, the entropy decoding unit 302 may decode, for the current block, a DIMD flag having a value indicating whether DIMD is enabled for the current block of video data. Based on the value of the DIMD flag, the intra prediction unit 318 may determine whether to predict the current block using DIMD. As an example, if the value of the flag is true (e.g., 1), the intra prediction unit 318 may determine to predict the current block using DIMD. As another example, if the value of the flag is false (e.g., 0), the intra prediction unit 318 may determine not to predict the current block using DIMD. As mentioned above, in some examples, the video decoder 300 may derive a list of DIMD intra modes regardless of the value of the DIMD flag.

[0154]

[0168] If the video decoder 300 determines not to predict the current block using DIMD (the “No” branch of 1806), the entropy decoding unit 302 may decode one or more syntax elements that indicate a selected intra mode from the MPM list (e.g., that indicate an index in the MPM list) (1808). For example, the entropy decoding unit 302 may decode an intra_luma_mpm_idx syntax element that specifies the index in the MPM list of the selected intra mode.

[0155]

[0169] The video decoder 300 may predict the current block using a candidate selected from the constructed MPM list (1810). For example, the intra prediction unit 318 may generate a predictive block for the current block using a selected intra mode from the MPM list. The reconstruction unit 310 may combine the predictive block with the residual block (e.g., similar to 380 of FIG. 16).

[0156]

[0170] If the video decoder 300 determines to predict the current block using DIMD (the "Yes" branch of 1806), the entropy decoding unit 302 may predict the current block using DIMD (1812). For example, the intra prediction unit 318 may predict the current block using the techniques described above with reference to FIG. 8.

[0157]

[0171] The following numbered clauses may represent one or more examples of this disclosure.

[0158]

[0172] Clause 1A. A method for decoding video data, the method comprising: deriving a list of intra modes for a current block of the video data and using decoder-side intra mode derivation (DIMD) using reconstructed samples of neighboring blocks; constructing a most probable mode (MPM) list for the current block that includes at least one intra mode from the derived list of intra modes; and predicting the current block using candidates selected from the constructed MPM list.

[0159]

[0173] Clause 2A. The method of clause 1A, wherein deriving the list of intra-modes using the DIMD comprises deriving the list of intra-modes using the DIMD regardless of the value of a DIMD flag.

[0160]

[0174] Clause 3A. The method of clause 1A or clause 2A, wherein constructing the MPM list comprises inserting into the MPM list a first candidate from a list of intra-modes derived using DIMD, and selectively inserting into the MPM list a second candidate from the list of intra-modes derived using DIMD based on a sum of the strengths of the second candidate.

[0161]

[0175] Clause 4A. The method of clause 3A, wherein constructing the MPM list further comprises inserting an additional intra-mode candidate into the MPM list and after the first candidate.

[0162]

[0176] Clause 5A. A device for coding video data, the device comprising one or more means for performing the method according to any of clauses 1A to 4A.

[0163]

[0177] Clause 6A. The device of clause 5A, wherein the one or more means comprises one or more processors implemented in circuitry.

[0164]

[0178] Clause 7A. The device of any of clauses 5A and 6A, further comprising a memory for storing video data.

[0165]

[0179] Clause 8A. The device of any of clauses 5A to 7A, further comprising a display configured to display the decoded video data.

[0166]

[0180] Clause 9A. The device of any of clauses 5A to 8A, wherein the device comprises one or more of a camera, a computer, a mobile device, a broadcast receiver device, or a set-top box.

[0167]

[0181] Clause 10A. A computer-readable storage medium having stored thereon instructions that, when executed, cause one or more processors to perform a method according to any of clauses 1A to 4A.

[0168]

[0182] Clause 1B. A method for decoding video data, the method comprising: deriving a list of intra modes for a current block of the video data and using decoder-side intra mode derivation (DIMD) using reconstructed samples of neighboring blocks; constructing a most probable mode (MPM) list for the current block; and predicting the current block using candidates selected from the constructed MPM list, wherein constructing the MPM list comprises inserting at least one intra mode from the derived list of intra modes into the MPM list.

[0169]

[0183] Clause 2B. The method of clause 1B, further comprising decoding, for the current block, a DIMD flag having a value indicating whether DIMD is enabled for the current block of video data, wherein deriving the list of intra modes using the DIMD comprises deriving the list of intra modes using the DIMD regardless of the value of the DIMD flag.

[0170]

[0184] Clause 3B. The method of clause 1B, wherein inserting at least one intra mode from the derived list of intra modes into the MPM list comprises inserting a first candidate from the list of intra modes derived using DIMD into the MPM list, and selectively inserting a second candidate from the list of intra modes derived using DIMD into the MPM list.

[0171]

[0185] Clause 4B. The method of clause 3B, wherein selectively inserting a second candidate comprises selectively inserting a second candidate into the MPM list based on a sum of strengths of the second candidate from a list of intra-modes derived using DIMD.

[0172]

[0186] Clause 5B. The method of clause 1B, wherein constructing the MPM list further comprises inserting additional intra-mode candidates into the MPM list and after at least one intra-mode from the derived list of intra-modes.

[0173]

[0187] Clause 6B. The method of clause 5B, wherein inserting additional intra-mode candidates comprises inserting one or more default candidates into the MPM list and after at least one intra-mode from the derived list of intra-modes.

[0174]

[0188] Clause 7B. The method described in Clause 5B, wherein constructing the MPM list further comprises inserting one or more intra-mode candidates that are prediction modes from neighboring blocks of the current block into the MPM list and before at least one intra-mode from the derived list of intra-modes.

[0175]

[0189] Clause 8B. A method of encoding video data, the method comprising: deriving a list of intra modes for a current block of video data and using decoder-side intra mode derivation (DIMD) using reconstructed samples of neighboring blocks; constructing a most probable mode (MPM) list for the current block, wherein constructing the MPM list comprises inserting at least one intra mode from the derived list of intra modes into the MPM list; selecting a candidate intra mode for the current block and from the MPM list; and encoding one or more syntax elements that specify the candidate intra modes for the current block.

[0176]

[0190] Clause 9B. The method of clause 8B, further comprising: encoding, for the current block, a DIMD flag having a value indicating whether DIMD is enabled for the current block of video data, wherein deriving the list of intra modes using the DIMD comprises deriving the list of intra modes using the DIMD regardless of the value of the DIMD flag.

[0177]

[0191] Clause 10B. The method of clause 8B, wherein inserting at least one intra mode from the derived list of intra modes into the MPM list comprises inserting a first candidate from the list of intra modes derived using DIMD into the MPM list, and selectively inserting a second candidate from the list of intra modes derived using DIMD into the MPM list.

[0178]

[0192] Clause 11B. The method of clause 10B, wherein selectively inserting a second candidate comprises selectively inserting a second candidate into the MPM list based on a sum of strengths of the second candidate from a list of intra-modes derived using DIMD.

[0179]

[0193] Clause 12B. The method of clause 8B, wherein constructing the MPM list further comprises inserting additional intra-mode candidates into the MPM list and after at least one intra-mode from the derived list of intra-modes.

[0180]

[0194] Clause 13B. The method of clause 12B, wherein inserting additional intra-mode candidates comprises inserting one or more default candidates into the MPM list and after at least one intra-mode from the derived list of intra-modes.

[0181]

[0195] Clause 14B. The method described in Clause 12B, wherein constructing the MPM list further comprises inserting one or more intra-mode candidates that are prediction modes from neighboring blocks of the current block into the MPM list and before at least one intra-mode from the derived list of intra-modes.

[0182]

[0196] Clause 15B. A device for decoding video data, the device comprising: a memory configured to store the video data; and one or more processors implemented in circuitry, the one or more processors configured to: derive a list of intra modes for a current block of the video data using decoder-side intra mode derivation (DIMD) and using reconstructed samples of neighboring blocks; construct a most probable mode (MPM) list for the current block; and predict the current block using candidates selected from the constructed MPM list, wherein constructing the MPM list comprises inserting at least one intra mode from the derived list of intra modes into the MPM list.

[0183]

[0197] Clause 16B. The device of clause 15B, wherein the one or more processors are further configured to: decode, for the current block, a DIMD flag having a value indicating whether DIMD is enabled for the current block of video data; and wherein, to derive a list of intra modes using the DIMD, the one or more processors are configured to derive a list of intra modes using the DIMD regardless of the value of the DIMD flag.

[0184]

[0198] Clause 17B. The device of Clause 15B, wherein to insert at least one intra-mode from the derived list of intra-modes into the MPM list, one or more processors are configured to insert into the MPM list a first candidate from the list of intra-modes derived using the DIMD, and selectively insert into the MPM list a second candidate from the list of intra-modes derived using the DIMD.

[0185]

[0199] Clause 18B. The device of clause 17B, wherein to selectively insert the second candidate, the one or more processors are configured to selectively insert the second candidate into the MPM list based on a sum of strengths of the second candidate from the list of intra-modes derived using DIMD.

[0186]

[0200] Clause 19B. The device of clause 15B, wherein to construct the MPM list, the one or more processors are configured to insert additional intra-mode candidates into the MPM list and after at least one intra-mode from the derived list of intra-modes.

[0187]

[0201] Clause 20B. The device of clause 19B, wherein to insert additional intra-mode candidates, the one or more processors are configured to insert one or more default candidates into the MPM list and after at least one intra-mode from the derived list of intra-modes.

[0188]

[0202] Clause 21B. The device of Clause 19B, wherein the one or more processors are configured to: insert, into the MPM list and before at least one intra mode from the derived list of intra modes, one or more intra mode candidates that are prediction modes from neighboring blocks of the current block, to construct the MPM list.

[0189]

[0203] Clause 22B. A device for encoding video data, the device comprising: a memory configured to store the video data; and one or more processors implemented in circuitry, the one or more processors configured to: derive, for a current block of video data, and using decoder-side intra mode derivation (DIMD), a list of intra modes using reconstructed samples of neighboring blocks; construct a most probable mode (MPM) list for the current block, wherein constructing the MPM list comprises inserting at least one intra mode from the derived list of intra modes into the MPM list; select candidate intra modes for the current block and from the MPM list; and encode, for the current block, one or more syntax elements specifying the candidate intra modes.

[0190]

[0204] Clause 23B. The device of clause 22B, wherein the one or more processors are further configured to: encode, for the current block, a DIMD flag having a value indicating whether DIMD is enabled for the current block of video data; and wherein, to derive a list of intra modes using the DIMD, the one or more processors are configured to derive a list of intra modes using the DIMD regardless of the value of the DIMD flag.

[0191]

[0205] Clause 24B. The device of Clause 22B, wherein to insert at least one intra-mode from the derived list of intra-modes into the MPM list, one or more processors are configured to insert into the MPM list a first candidate from the list of intra-modes derived using the DIMD, and selectively insert into the MPM list a second candidate from the list of intra-modes derived using the DIMD.

[0192]

[0206] Clause 25B. The device of clause 24B, wherein to selectively insert the second candidate, the one or more processors are configured to selectively insert the second candidate into the MPM list based on a sum of strengths of the second candidate from the list of intra-modes derived using DIMD.

[0193]

[0207] Clause 26B. The device of clause 22B, wherein to construct the MPM list, the one or more processors are configured to insert additional intra-mode candidates into the MPM list and after at least one intra-mode from the derived list of intra-modes.

[0194]

[0208] Clause 27B. The device of clause 26B, wherein to insert additional intra-mode candidates, the one or more processors are configured to insert one or more default candidates into the MPM list and after at least one intra-mode from the derived list of intra-modes.

[0195]

[0209] Clause 28B. The device of clause 26B, wherein the one or more processors are configured to: insert, into the MPM list and before at least one intra mode from the derived list of intra modes, one or more intra mode candidates that are prediction modes from neighboring blocks of the current block, to construct the MPM list.

[0196]

[0210] Clause 1C. A method for decoding video data, the method comprising: deriving a list of intra modes for a current block of the video data and using decoder-side intra mode derivation (DIMD) using reconstructed samples of neighboring blocks; constructing a most probable mode (MPM) list for the current block; and predicting the current block using candidates selected from the constructed MPM list, wherein constructing the MPM list comprises inserting at least one intra mode from the derived list of intra modes into the MPM list.

[0197]

[0211] Clause 2C. The method of clause 1C, further comprising decoding, for the current block, a DIMD flag having a value indicating whether DIMD is enabled for the current block of video data, wherein deriving the list of intra modes using the DIMD comprises deriving the list of intra modes using the DIMD regardless of the value of the DIMD flag.

[0198]

[0212] Clause 3C. The method of clause 1C or 2C, wherein inserting at least one intra mode from the derived list of intra modes into the MPM list comprises inserting into the MPM list a first candidate from the list of intra modes derived using DIMD, and selectively inserting into the MPM list a second candidate from the list of intra modes derived using DIMD.

[0199]

[0213] Clause 4C. The method of clause 3C, wherein selectively inserting the second candidate comprises selectively inserting the second candidate into the MPM list based on a sum of strengths of the second candidate from a list of intra-modes derived using DIMD.

[0200]

[0214] Clause 5C. The method of any of clauses 1C to 4C, wherein constructing the MPM list further comprises inserting additional intra-mode candidates into the MPM list and after at least one intra-mode from the derived list of intra-modes.

[0201]

[0215] Clause 6C. The method of clause 5C, wherein inserting additional intra-mode candidates comprises inserting one or more default candidates into the MPM list and after at least one intra-mode from the derived list of intra-modes.

[0202]

[0216] Clause 7C. The method of clause 5C or 6C, wherein constructing the MPM list further comprises inserting one or more intra-mode candidates, which are prediction modes from neighboring blocks of the current block, into the MPM list and before at least one intra-mode from the derived list of intra-modes.

[0203]

[0217] Clause 8C. A method of encoding video data, the method comprising: deriving a list of intra modes for a current block of video data and using decoder-side intra mode derivation (DIMD) using reconstructed samples of neighboring blocks; constructing a most probable mode (MPM) list for the current block, wherein constructing the MPM list comprises inserting at least one intra mode from the derived list of intra modes into the MPM list; selecting a candidate intra mode for the current block and from the MPM list; and encoding one or more syntax elements that specify the candidate intra modes for the current block.

[0204]

[0218] Clause 9C. The method of clause 8C, further comprising: encoding, for the current block, a DIMD flag having a value indicating whether DIMD is enabled for the current block of video data, wherein deriving the list of intra modes using the DIMD comprises deriving the list of intra modes using the DIMD regardless of the value of the DIMD flag.

[0205]

[0219] Clause 10C. The method of clause 8C or 9C, wherein inserting at least one intra mode from the derived list of intra modes into the MPM list comprises inserting into the MPM list a first candidate from the list of intra modes derived using DIMD, and selectively inserting into the MPM list a second candidate from the list of intra modes derived using DIMD.

[0206]

[0220] Clause 11C. The method of clause 10C, wherein selectively inserting a second candidate comprises selectively inserting a second candidate into the MPM list based on a sum of strengths of the second candidate from a list of intra-modes derived using DIMD.

[0207]

[0221] Clause 12C. The method of any of clauses 8C to 11C, wherein constructing the MPM list further comprises inserting additional intra-mode candidates into the MPM list and after at least one intra-mode from the derived list of intra-modes.

[0208]

[0222] Clause 13C. The method of clause 12C, wherein inserting additional intra-mode candidates comprises inserting one or more default candidates into the MPM list and after at least one intra-mode from the derived list of intra-modes.

[0209]

[0223] Clause 14C. The method of clause 12C or 13C, wherein constructing the MPM list further comprises inserting one or more intra-mode candidates, which are prediction modes from neighboring blocks of the current block, into the MPM list and before at least one intra-mode from the derived list of intra-modes.

[0210]

[0224] Clause 15C. A device for decoding video data, the device comprising: a memory configured to store the video data; and one or more processors implemented in circuitry, the one or more processors configured to: derive a list of intra modes for a current block of the video data using decoder-side intra mode derivation (DIMD) and using reconstructed samples of neighboring blocks; construct a most probable mode (MPM) list for the current block; and predict the current block using candidates selected from the constructed MPM list, wherein constructing the MPM list comprises inserting at least one intra mode from the derived list of intra modes into the MPM list.

[0211]

[0225] Clause 16C. The device of clause 15C, wherein the one or more processors are further configured to: decode, for the current block, a DIMD flag having a value indicating whether DIMD is enabled for the current block of video data; and wherein, to derive a list of intra modes using the DIMD, the one or more processors are configured to derive a list of intra modes using the DIMD regardless of the value of the DIMD flag.

[0212]

[0226] Clause 17C. The device of clause 15C or 16C, wherein to insert at least one intra-mode from the derived list of intra-modes into the MPM list, one or more processors are configured to insert into the MPM list a first candidate from the list of intra-modes derived using the DIMD, and selectively insert into the MPM list a second candidate from the list of intra-modes derived using the DIMD.

[0213]

[0227] Clause 18C. The device of clause 17C, wherein to selectively insert the second candidate, the one or more processors are configured to selectively insert the second candidate into the MPM list based on a sum of strengths of the second candidate from the list of intra-modes derived using DIMD.

[0214]

[0228] Clause 19C. The device of any of clauses 15C to 18C, wherein, to construct the MPM list, the one or more processors are configured to insert additional intra-mode candidates into the MPM list and after at least one intra-mode from the derived list of intra-modes.

[0215]

[0229] Clause 20C. The device of clause 19C, wherein to insert additional intra-mode candidates, the one or more processors are configured to insert one or more default candidates into the MPM list and after at least one intra-mode from the derived list of intra-modes.

[0216]

[0230] Clause 21C. The device of clause 19C or 20C, wherein the one or more processors are configured to: insert, into the MPM list and before at least one intra mode from the derived list of intra modes, one or more intra mode candidates that are prediction modes from neighboring blocks of the current block, to construct the MPM list.

[0217]

[0231] Clause 22C. A device for encoding video data, the device comprising: a memory configured to store the video data; and one or more processors implemented in circuitry, the one or more processors configured to: derive, for a current block of video data, and using decoder-side intra mode derivation (DIMD), a list of intra modes using reconstructed samples of neighboring blocks; construct a most probable mode (MPM) list for the current block, wherein constructing the MPM list comprises inserting at least one intra mode from the derived list of intra modes into the MPM list; select candidate intra modes for the current block and from the MPM list; and encode, for the current block, one or more syntax elements specifying the candidate intra modes.

[0218]

[0232] Clause 23C. The device of clause 22C, wherein the one or more processors are further configured to: encode, for the current block, a DIMD flag having a value indicating whether DIMD is enabled for the current block of video data; and wherein, to derive a list of intra modes using the DIMD, the one or more processors are configured to derive a list of intra modes using the DIMD regardless of the value of the DIMD flag.

[0219]

[0233] Clause 24C. The device of clause 22C or 23C, wherein to insert at least one intra-mode from the derived list of intra-modes into the MPM list, one or more processors are configured to insert into the MPM list a first candidate from the list of intra-modes derived using the DIMD, and selectively insert into the MPM list a second candidate from the list of intra-modes derived using the DIMD.

[0220]

[0234] Clause 25C. The device of clause 24C, wherein to selectively insert the second candidate, the one or more processors are configured to selectively insert the second candidate into the MPM list based on a sum of strengths of the second candidate from the list of intra-modes derived using DIMD.

[0221]

[0235] Clause 26C. The device of any of clauses 22C to 25C, wherein, to construct the MPM list, the one or more processors are configured to insert additional intra-mode candidates into the MPM list and after at least one intra-mode from the derived list of intra-modes.

[0222]

[0236] Clause 27C. The device of clause 26C, wherein to insert additional intra-mode candidates, the one or more processors are configured to insert one or more default candidates into the MPM list and after at least one intra-mode from the derived list of intra-modes.

[0223]

[0237] Clause 28C. The device of clause 26C or 27C, wherein the one or more processors are configured to: insert, into the MPM list and before at least one intra mode from the derived list of intra modes, one or more intra mode candidates that are prediction modes from neighboring blocks of the current block, to construct the MPM list.

[0224]

[0238] Clause 1D. A computer-readable storage medium storing instructions that, when executed, cause one or more processors of a video coder to perform the method of any of clauses 1C through 7C.

[0225]

[0239] Clause 1E. A computer-readable storage medium storing instructions that, when executed, cause one or more processors of a video coder to perform the method of any of clauses 8C to 14C.

[0226]

[0240] It should be appreciated that, depending on the example, some acts or events of any of the techniques described herein may be performed in a different sequence, added, merged, or entirely excluded (e.g., not all described acts or events may be required to practice the techniques). Moreover, in some examples, acts or events may be performed simultaneously rather than sequentially, for example, through multithreaded processing, interrupt processing, or multiple processors.

[0227]

[0241] In one or more examples, the functions described may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions may be stored on or transmitted via a computer-readable medium as one or more instructions or code and executed by a hardware-based processing unit. Computer-readable media may include computer-readable storage media, which correspond to tangible media such as data storage media, or communication media, including any medium that facilitates transfer of a computer program from one place to another, for example, according to a communications protocol. In this manner, computer-readable media may generally correspond to (1) tangible computer-readable storage media that is non-transitory, or (2) a communication medium such as a signal or carrier wave. Data storage media 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 implementing the techniques described in this disclosure. A computer program product may include a computer-readable medium.

[0228]

[0242] 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 can be used to store desired program code in the form of instructions or data structures and that can be accessed by a computer. Also, any connection is properly termed 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 within the definition of 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 discs (CDs), laser discs, optical discs, digital versatile discs (DVDs), floppy discs, and Blu-ray discs, 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.

[0229]

[0243] The instructions may be executed by one or more processors, such as one or more DSPs, general-purpose microprocessors, ASICs, FPGAs, or other equivalent integrated circuits or discrete logic circuits. Accordingly, the terms "processor" and "processing circuitry" as used herein may refer to any of the above structures or any other structure 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 combined codec. Also, the techniques may be fully implemented in one or more circuits or logic elements.

[0230]

[0244] The techniques of this 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). Although various components, modules, or units have been described in this disclosure to highlight functional aspects of devices configured to implement the disclosed techniques, those 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.

[0231]

[0245] Various examples have been described. These and other examples are within the scope of the following claims. The inventions described in the claims of the present application as originally filed are set forth below. [C1] 1. A method for decoding video data, the method comprising: deriving a list of intra modes for a current block of video data and using decoder-side intra mode derivation (DIMD) using reconstructed samples of neighboring blocks; constructing a Most Probable Mode (MPM) list for the current block, wherein constructing the MPM list comprises inserting at least one intra-mode from the derived list of intra-modes into the MPM list; predicting the current block using a candidate selected from the constructed MPM list; A method comprising: [C2] further comprising decoding, for the current block, a DIMD flag having a value indicating whether DIMD is enabled for the current block of video data, wherein deriving the list of intra modes using DIMD comprises deriving the list of intra modes using DIMD regardless of the value of the DIMD flag. The method described in C1. [C3] inserting the at least one intra-mode from the derived list of intra-modes into the MPM list; inserting into the MPM list a first candidate from the list of intra modes derived using DIMD; selectively inserting into the MPM list a second candidate from the list of intra modes derived using DIMD; The method of claim C1, comprising: [C4] The method of C3, wherein selectively inserting the second candidate comprises selectively inserting the second candidate into the MPM list based on a sum of strengths of the second candidate from the list of intra modes derived using DIMD. [C5] constructing the MPM list, inserting additional intra-mode candidates into the MPM list and after the at least one intra-mode from the derived list of intra-modes. The method of C1, further comprising: [C6] inserting the additional intra mode candidate The method of C5, comprising inserting one or more default candidates into the MPM list and after the at least one intra mode from the derived list of intra modes. [C7] constructing the MPM list, inserting one or more candidate intra modes, which are prediction modes from neighboring blocks of the current block, into the MPM list and before the at least one intra mode from the derived list of intra modes. The method of C5, further comprising: [C8] 1. A method for encoding video data, the method comprising: deriving a list of intra modes for a current block of video data and using decoder-side intra mode derivation (DIMD) using reconstructed samples of neighboring blocks; constructing a Most Probable Mode (MPM) list for the current block, wherein constructing the MPM list comprises inserting at least one intra mode from the derived list of intra modes into the MPM list; selecting a candidate intra mode for the current block and from the MPM list; encoding, for the current block, one or more syntax elements that specify the candidate intra modes; A method comprising: [C9] encoding, for the current block, a DIMD flag having a value indicating whether DIMD is enabled for the current block of video data, wherein deriving the list of intra modes using DIMD comprises deriving the list of intra modes using DIMD regardless of a value of the DIMD flag. The method described in C8. [C10] inserting the at least one intra-mode from the derived list of intra-modes into the MPM list; inserting into the MPM list a first candidate from the list of intra modes derived using DIMD; selectively inserting into the MPM list a second candidate from the list of intra modes derived using DIMD; The method of claim C8, comprising: [C11] The method of C10, wherein selectively inserting the second candidate comprises selectively inserting the second candidate into the MPM list based on a sum of strengths of the second candidate from the list of intra modes derived using DIMD. [C12] constructing the MPM list, inserting additional intra-mode candidates into the MPM list and after the at least one intra-mode from the derived list of intra-modes. The method of C8, further comprising: [C13] inserting the additional intra mode candidate The method of C12, comprising inserting one or more default candidates into the MPM list and after the at least one intra mode from the derived list of intra modes. [C14] constructing the MPM list, inserting one or more candidate intra modes, which are prediction modes from neighboring blocks of the current block, into the MPM list and before the at least one intra mode from the derived list of intra modes. The method of C12, further comprising: [C15] 1. A device for decoding video data, said device comprising: a memory configured to store video data; one or more processors implemented in the circuit; wherein the one or more processors: deriving a list of intra modes for a current block of video data and using decoder-side intra mode derivation (DIMD) using reconstructed samples of neighboring blocks; constructing a Most Probable Mode (MPM) list for the current block, wherein constructing the MPM list comprises inserting at least one intra-mode from the derived list of intra-modes into the MPM list; predicting the current block using a candidate selected from the constructed MPM list; A device configured to: [C16] the one or more processors: and further configured to: for the current block, decode a DIMD flag having a value indicating whether DIMD is enabled for the current block of video data, wherein to derive the list of intra modes using DIMD, the one or more processors are configured to derive the list of intra modes using DIMD regardless of the value of the DIMD flag. The device described in C15. [C17] to insert the at least one intra-mode from the derived list of intra-modes into the MPM list, the one or more processors: inserting into the MPM list a first candidate from the list of intra modes derived using DIMD; selectively inserting into the MPM list a second candidate from the list of intra modes derived using DIMD; 16. The device of claim 15, configured to: [C18] The device of C17, wherein, to selectively insert the second candidate, the one or more processors are configured to selectively insert the second candidate into the MPM list based on a sum of strengths of the second candidate from the list of intra modes derived using DIMD. [C19] To construct the MPM list, the one or more processors: inserting additional intra-mode candidates into the MPM list and after the at least one intra-mode from the derived list of intra-modes. 16. The device of claim 15, configured to: [C20] To insert the additional intra-mode candidate, the one or more processors: The device of C19, configured to insert one or more default candidates into the MPM list and after the at least one intra mode from the derived list of intra modes. [C21] To construct the MPM list, the one or more processors: inserting one or more candidate intra modes, which are prediction modes from neighboring blocks of the current block, into the MPM list and before the at least one intra mode from the derived list of intra modes. 20. The device of claim 19, configured to: [C22] 1. A device for encoding video data, said device comprising: a memory configured to store video data; one or more processors implemented in the circuit; wherein the one or more processors: deriving a list of intra modes for a current block of video data and using decoder-side intra mode derivation (DIMD) using reconstructed samples of neighboring blocks; constructing a Most Probable Mode (MPM) list for the current block, wherein constructing the MPM list comprises inserting at least one intra mode from the derived list of intra modes into the MPM list; selecting a candidate intra mode for the current block and from the MPM list; encoding, for the current block, one or more syntax elements that specify the candidate intra modes; A device configured to: [C23] the one or more processors: and further configured to: for the current block, encode a DIMD flag having a value indicating whether DIMD is enabled for the current block of video data, wherein to derive the list of intra modes using DIMD, the one or more processors are configured to derive the list of intra modes using DIMD regardless of the value of the DIMD flag. The device described in C22. [C24] to insert the at least one intra-mode from the derived list of intra-modes into the MPM list, the one or more processors: inserting into the MPM list a first candidate from the list of intra modes derived using DIMD; selectively inserting into the MPM list a second candidate from the list of intra modes derived using DIMD; 23. The device of claim 22, configured to: [C25] The device of C24, wherein, to selectively insert the second candidate, the one or more processors are configured to selectively insert the second candidate into the MPM list based on a sum of strengths of the second candidate from the list of intra modes derived using DIMD. [C26] To construct the MPM list, the one or more processors: inserting additional intra-mode candidates into the MPM list and after the at least one intra-mode from the derived list of intra-modes. 23. The device of claim 22, configured to: [C27] To insert the additional intra-mode candidate, the one or more processors: The device of C26, configured to insert one or more default candidates into the MPM list and after the at least one intra mode from the derived list of intra modes. [C28] To construct the MPM list, the one or more processors: inserting one or more candidate intra modes, which are prediction modes from neighboring blocks of the current block, into the MPM list and before the at least one intra mode from the derived list of intra modes. 20. The device of claim 19, wherein the device is configured to:

Claims

1. 1. A method for decoding video data, the method comprising: deriving a list of intra modes for a current block of video data and using decoder-side intra mode derivation (DIMD) using reconstructed samples of neighboring blocks; constructing a Most Probable Mode (MPM) list for the current block, wherein constructing the MPM list comprises inserting at least one intra mode from the derived list of intra modes into the MPM list, and inserting the at least one intra mode from the derived list of intra modes into the MPM list comprises: inserting into the MPM list a first candidate from the list of intra modes derived using DIMD; selectively inserting into the MPM list a second candidate from the list of intra-modes derived using DIMD. predicting the current block using a candidate selected from the constructed MPM list; A method comprising:

2. further comprising decoding, for the current block, a DIMD flag having a value indicating whether DIMD is enabled for the current block of video data, wherein deriving the list of intra modes using DIMD comprises deriving the list of intra modes using DIMD regardless of a value of the DIMD flag. The method of claim 1.

3. 1. A method for encoding video data, the method comprising: deriving a list of intra modes for a current block of video data and using decoder-side intra mode derivation (DIMD) using reconstructed samples of neighboring blocks; constructing a Most Probable Mode (MPM) list for the current block, wherein constructing the MPM list comprises inserting at least one intra mode from the derived list of intra modes into the MPM list, and inserting the at least one intra mode from the derived list of intra modes into the MPM list comprises: inserting into the MPM list a first candidate from the list of intra modes derived using DIMD; selectively inserting into the MPM list a second candidate from the list of intra-modes derived using DIMD. selecting a candidate intra mode for the current block and from the MPM list; encoding, for the current block, one or more syntax elements that specify the candidate intra modes; A method comprising:

4. 2. The method of claim 1, wherein selectively inserting the second candidate comprises selectively inserting the second candidate into the MPM list based on a sum of strengths of the second candidate from the list of intra modes derived using DIMD.

5. The method of claim 3, wherein selectively inserting the second candidate comprises selectively inserting the second candidate into the MPM list based on a sum of strengths of the second candidate from the list of intra modes derived using DIMD.

6. constructing the MPM list, inserting additional intra-mode candidates into the MPM list and after the at least one intra-mode from the derived list of intra-modes. The method of claim 1 further comprising:

7. Constructing the MPM list comprises: inserting additional intra-mode candidates into the MPM list and after the at least one intra-mode from the derived list of intra-modes. The method of claim 3 further comprising:

8. inserting the additional intra mode candidate The method of claim 6 , comprising inserting one or more default candidates into the MPM list and after the at least one intra-mode from the derived list of intra-modes.

9. The method of claim 8, wherein inserting the additional intra mode candidate comprises: The method of claim 7 , comprising inserting one or more default candidates into the MPM list and after the at least one intra-mode from the derived list of intra-modes.

10. constructing the MPM list, inserting one or more candidate intra modes, which are prediction modes from neighboring blocks of the current block, into the MPM list and before the at least one intra mode from the derived list of intra modes. The method of claim 6 further comprising:

11. Constructing the MPM list comprises: inserting one or more candidate intra modes, which are prediction modes from neighboring blocks of the current block, into the MPM list and before the at least one intra mode from the derived list of intra modes. The method of claim 7 further comprising:

12. encoding, for the current block, a DIMD flag having a value indicating whether DIMD is enabled for the current block of video data, wherein deriving the list of intra modes using DIMD comprises deriving the list of intra modes using DIMD regardless of a value of the DIMD flag. The method of claim 3.

13. 1. A device for decoding video data, said device comprising: a memory configured to store video data; one or more processors implemented in the circuit; wherein the one or more processors: deriving a list of intra modes for a current block of video data and using decoder-side intra mode derivation (DIMD) using reconstructed samples of neighboring blocks; constructing a Most Probable Mode (MPM) list for the current block, wherein constructing the MPM list comprises inserting at least one intra mode from the derived list of intra modes into the MPM list, wherein to insert the at least one intra mode from the derived list of intra modes into the MPM list, the one or more processors: inserting into the MPM list a first candidate from the list of intra modes derived using DIMD; selectively inserting into the MPM list a second candidate from the list of intra modes derived using DIMD. predicting the current block using a candidate selected from the constructed MPM list; A device configured to:

14. the one or more processors: and further configured to: for the current block, decode a DIMD flag having a value indicating whether DIMD is enabled for the current block of video data, wherein to derive the list of intra modes using DIMD, the one or more processors are configured to derive the list of intra modes using DIMD regardless of the value of the DIMD flag. The device of claim 13.

15. 1. A device for encoding video data, said device comprising: a memory configured to store video data; one or more processors implemented in the circuit; wherein the one or more processors: deriving a list of intra modes for a current block of video data and using decoder-side intra mode derivation (DIMD) using reconstructed samples of neighboring blocks; constructing a Most Probable Mode (MPM) list for the current block, wherein constructing the MPM list comprises inserting at least one intra mode from the derived list of intra modes into the MPM list, wherein to insert the at least one intra mode from the derived list of intra modes into the MPM list, the one or more processors: inserting into the MPM list a first candidate from the list of intra modes derived using DIMD; selectively inserting into the MPM list a second candidate from the list of intra modes derived using DIMD; selecting a candidate intra mode for the current block and from the MPM list; encoding, for the current block, one or more syntax elements that specify the candidate intra modes; A device configured to:

16. the one or more processors: further configured to: encode, for the current block, a DIMD flag having a value indicating whether DIMD is enabled for the current block of video data, wherein to derive the list of intra modes using DIMD, the one or more processors are configured to derive the list of intra modes using DIMD regardless of the value of the DIMD flag.

16. The device of claim 15.

17. 14. The device of claim 13, wherein to selectively insert the second candidate, the one or more processors are configured to selectively insert the second candidate into the MPM list based on a sum of strengths of the second candidate from the list of intra-modes derived using DIMD.

18. The device of claim 15, wherein, to selectively insert the second candidate, the one or more processors are configured to selectively insert the second candidate into the MPM list based on a sum of strengths of the second candidate from the list of intra-modes derived using DIMD.

19. To construct the MPM list, the one or more processors: inserting additional intra-mode candidates into the MPM list and after the at least one intra-mode from the derived list of intra-modes. configured to: To insert the additional intra-mode candidate, the one or more processors:

14. The device of claim 13, configured to insert one or more default candidates into the MPM list and after the at least one intra-mode from the derived list of intra-modes.

20. To construct the MPM list, the one or more processors: inserting additional intra-mode candidates into the MPM list and after the at least one intra-mode from the derived list of intra-modes. configured to: To insert the additional intra-mode candidate, the one or more processors:

16. The device of claim 15, configured to insert one or more default candidates into the MPM list and after the at least one intra-mode from the derived list of intra-modes.

21. To construct the MPM list, the one or more processors: inserting an additional intra-mode candidate into the MPM list and after the at least one intra-mode from the derived list of intra-modes; inserting one or more candidate intra modes, which are prediction modes from neighboring blocks of the current block, into the MPM list and before the at least one intra mode from the derived list of intra modes; 20. The device of claim 19 configured to:

22. To construct the MPM list, the one or more processors: inserting an additional intra-mode candidate into the MPM list and after the at least one intra-mode from the derived list of intra-modes; inserting one or more candidate intra modes, which are prediction modes from neighboring blocks of the current block, into the MPM list and before the at least one intra mode from the derived list of intra modes; 21. The device of claim 20 configured to:

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