DIMD coding using non-angular candidates

Abstract

Decoder side intra mode derivation saves on an amount of coding bits by letting a decoder autonomously predict which intra-prediction mode (i.e. e.g. which angle of prediction) would work as a good predictor for reconstructing a current block (possibly with correction bits improving the prediction). Thereto, the decoder must construct a histogram of likely intra—prediction modes. It may reused well—working IPMs from adjacent blocks. If e. g. an upper-left (primary) block was itself DIMDpredicted, it will already have a set of IPMs, and a histogram, which can be kept in memory e. g. until the present intra—picture is entirely reconstructed. So one could add a few of those IPMs to the histogram of the current block. But oftentimes many of the neighboring blocks are predicted by manners which do not use angular IPMs, like e. g. intra-block copy, but such methods may depend on another, reference block somewhere else in the already partially reconstructed current intra—picture. According to the present innovation, one may then add IPMs from at least one secondary block which is in the neighborhood of that reference block. Fig. 27B

Description

DIMD CODING USING NONANGULAR CANDIDATES FIELD OF THE INVENTION The invention relates to compression of data which specify images, such as for e.g. MPEG compression standards. BACKGROUND OF THE INVENTION A succession of increasingly capable video compression standardized codecs has evolved from MPEG1 and MPEG2 to the previous standardized MPEG codec: Versatile Video Coding. VVC has a lot of capabilities (tools) to compress data for various applications (e. g. movie streaming versus remote teaching by video conferencing) and various quality levels and demands (e. g. bit-rate, computational load etc.), to serve such apparatuses ranging from cheap television sets to high end mobile phones. It can cater nicely for all of those situations, but things can always be improved, and bit rate saving may always be benecial at least for some applications (e. g. travelers having purchased a limited data budget eSIM). Currently the video coding researchers have grouped to study a possible next generation video standard, which is being done under the Enhanced Coding Model (ECM) effort. In particular, one is looking at what can be improved about spatial prediction of blocks in e. g. an intra predicted image (which doesnt need data from previously reconstructed images, but only from its own previously reconstructed blocks). VVC would lean heavily on specifying exactly what (according to the encoder) would be the best spatial manner of prediction (e. g. continue pixels in a diagonally striped pattern from a previously reconstructed pixel on such a stripe in the direction of the stripe), in the compressed data that is sent to a decoder (either directly e. g. streamed, or indirectly via storage in some memory like a bluray disk, or a hard disk of some server farm). But that would require a lot of bits. Although coming at a cost of increased computation for decoders, for some applications it may be good if at least for some blocks the decoder may gure out by itself what the best prediction angle (intra-prediction mode IPM) would be. This can be done as was proposed based on a histogram of gradients in a neighboring region of the currently being predicted block, by Decoder side intra mode derivation (DIMD). This yields a number of IPMs, from which one may construct a best predictor, eg. typically by optimally weighting a couple of the IPMs. It may however still be improved to have more and / or better IPMs. SUMMARY OF THE INVENTION Because, if one were only to use neighboring blocks of a current to be decoded block which themselves were DIMD predicted, one would have too few intra-prediction modes in the merged histogram for constructing a best prediction predictor for the current block, the present inventors propose a method of decoding a current block (2700) of a video image using decoder side intra mode derivation (DIMD), which derives a set of intra-prediction modes which are represented in a histogram wherein for each intra-prediction mode (Ml , M2) there is a corresponding amplitude (Al , A2), the method comprising: selecting a primary block (2704) from a neighborhood directly adjacent to the current block which comprises already decoded pixels; - when said primary block is predicted from a corresponding reference block (2724) by shifting the block over a block vector to the primary block, selecting a secondary block (2730) in a neighborhood of the reference block; when the secondary block comprises at least one angular intraprediction mode adding that angular intraprediction mode to the histogram and determining a new amplitude for that intra prediction mode; determining a predictor for the current block based on one or more intraprediction modes from the histogram; and reconstructing pixel colors of the current block based on the predictor. A useful embodiment is the method wherein the secondary block and a tertiary block (2810) partially overlap with the reference block and wherein the selection of the secondary block is dependent on an absolute amount of pixels or a relative amount of pixels which is relative to a size of the secondary and / or reference block, which pixels lie within both the secondary block and the reference block. Further useful embodiments are: The method wherein the secondary block is only selected if the absolute or relative amount of pixels is above a threshold. The method wherein the decoder side intra mode derivation is one of a gradient-based decoder side intra mode derivation, occurrence-based intra coding (OBIC), merged intra mode derivation (MIMD) and DIMD merge list mode. The method wherein the secondary block angular intraprediction mode is added if the secondary block is predicted by one of a gradientbased decoder side intra mode derivation, occurrence based intra coding (OBIC), merged intra mode derivation (MIMD) and DIMD merge list mode. The method wherein the primary block is predicted by one of Intra Block Copy (IBC), Reorderedreconstruction Intra Block Copy (RR-IBC), lntra Template Matching Prediction (IntraTMP) mode, or Reorderedreconstruction Intra Template Matching Prediction (RR-TMP). The method wherein the primary block is selected according to a fixed order of selecting neighboring blocks of the current block. The method wherein the new amplitude is determined based on at least a scaled version of an original amplitude that the at least one angular intra-prediction mode has in the secondary block. The method wherein there is additionally added to the histogram at least one intra- prediction mode from a block taken from a list of history-based candidate blocks. The method wherein in addition to an amplitude, for an intra-prediction mode taken from a secondary block at least one of a weight and a location-dependency indicator may be added to the histogram for the current block. A video decoder comprising a memory and a processor arranged to decode a current block (2700) of a video image using decoder side intra mode derivation (DIMD), which derives a set of intra-prediction modes which are represented in a histogram wherein for each intra-prediction mode (M1, M2) there is a corresponding amplitude (Al, A2), processor being arranged to: select a primary block (2704) from a neighborhood directly adjacent to the current block which comprises already decoded pixels; - when said primary block is predicted from a corresponding reference block (2724) by shifting the block over a block vector to the primary block, select a secondary block (2730) in a neighborhood of the reference block; when the secondary block comprises at least one angular intraprediction mode, add that angular intraprediction mode to the histogram and determine a new amplitude for that intraprediction mode; - determine a predictor for the current block based on one or more intra-prediction modes from the histogram; and reconstruct pixel colors of the current block based on the predictor. The video decoder wherein the processor is arranged select the secondary block depending on an absolute amount of pixels or a relative amount of pixels which is relative to a size of the secondary and / or reference block, which pixels lie within both the secondary block and the reference block. The video decoder wherein the processor is arranged to determine the new amplitude of an intra-prediction mode in the histogram of the current block based on at least a scaled version of an original amplitude that the at least one angular intra-prediction mode has in the secondary block. A method of encoding a current block (2700) of a video image using decoder side intra mode derivation (DIMD), which derives a set of intraprediction modes which are represented in a histogram wherein for each intraprediction mode (M1, M2) there is a corresponding amplitude (A1, A2), the method comprising: selecting a primary block (2704) from a neighborhood directly adjacent to the current block which comprises already decoded pixels; - when said primary block is predicted from a corresponding reference block (2724) by shifting the block over a block vector to the primary block, selecting a secondary block (2730) in a neighborhood of the reference block; when the secondary block comprises at least one angular intraprediction mode adding that angular intra-prediction mode to the histogram and determining a new amplitude for that intra- prediction mode; - determining a predictor for the current block based on one or more intra-prediction modes from the histogram; and reconstructing pixel colors of the current block based on the predictor. The method of encoding wherein the secondary block and a tertiary block (2810) partially overlap with the reference block and wherein the selection of the secondary block is dependent on an absolute amount of pixels or a relative amount of pixels which is relative to a size of the secondary and / or reference block, which pixels lie within both the secondary block and the reference block. A video encoder comprising a memory and a processor arranged to decode a current block (2700) of a video image using decoder side intra mode derivation (DIMD), which derives a set of intra-prediction modes which are represented in a histogram wherein for each intra-prediction mode (M1, M2) there is a corresponding amplitude (Al, A2), processor being arranged to: select a primary block (2704) from a neighborhood directly adjacent to the current block which comprises already decoded pixels; - when said primary block is predicted from a corresponding reference block (2724) by shifting the block over a block vector to the primary block, select a secondary block (2730) in a neighborhood of the reference block; when the secondary block comprises at least one angular intraprediction mode, add that angular intraprediction mode to the histogram and determine a new amplitude for that intraprediction mode; - determine a predictor for the current block based on one or more intra-prediction modes from the histogram; and reconstruct pixel colors of the current block based on the predictor. The Video encoder wherein the processor is arranged select the secondary block depending on an absolute amount of pixels or a relative amount of pixels which is relative to a size of the secondary and / or reference block, which pixels lie within both the secondary block and the reference block. A computer software product in a tangible memory, comprising code which when performed on a processor executes any embodiment of the decoding method. A computer software product in a tangible memory, comprising code which when performed on a processor executes any embodiment of the decoding method 14. A digital video signal, comprising data specifying an encoding a current block (2700) of a video image using decoder side intra mode derivation (DIMD), which is based on a set of intra-prediction modes which are represented in a histogram wherein for each intraprediction mode (M1, M2) there is a corresponding amplitude (Al, A2), wherein the data comprises an indicator that a decoder should: select a primary block (2704) from a neighborhood directly adjacent to the current block which comprises already decoded pixels; - when said primary block is predicted from a corresponding reference block (2724) by shifting the block over a block vector to the primary block, select a secondary block (2730) in a neighborhood of the reference block; - when the secondary block comprises at least one angular intra-prediction mode add that angular intra-prediction mode to the histogram and determining a new amplitude for that intra-prediction mode; - determine a predictor for the current block based on one or more intra-prediction modes from the histogram; and reconstruct pixel colors of the current block based on the predictor. BRIEF DESCRIPTION OF THE DRAWINGS Some features are shown by way of example, and not by limitation, in the accompanying drawings. In the drawings, like numerals reference similar elements. FIG. 1 shows an example video coding / decoding system in which embodiments of the present disclosure may be implemented. FIG. 2 shows an example encoder in which embodiments of the present disclosure may be implemented. FIG. 3 shows an example decoder in which embodiments of the present disclosure may be implemented. FIG. 4 shows an example quadtree partitioning of a coding tree block (CTB). FIG. 5 shows an example quadtree corresponding to the example quadtree partitioning of the CTB in FIG. 4. FIG. 6 show examples of binary tree and ternary tree partitions. FIG. 7 shows an example of combined quadtree and multi-type tree partitioning of a CTB. FIG. 8 shows an example tree corresponding to the combined quadtree and multi-type tree partitioning of the CTB shown in FIG. 7. FIG. 9 shows an example set of reference samples determined for intra prediction of a current block. FIG. 10A and FIG. 10B show example intra prediction modes. FIG. 11 shows an example of a current block and corresponding reference samples. FIG. 12 shows an example of applying an intra prediction mode (eg., an angular mode) for prediction of a current block. FIG. 13A shows an example of inter prediction performed for a current block in a current picture. FIG. 13B shows an example motion vector. FIG. 14 shows an example of biprediction performed for a current block. FIG. 15A shows example spatial candidate neighboring blocks relative to a current block being coded. FIG. 15B shows example locations of two temporal, colocated blocks relative to a current block. FIG. 16A shows an example of intra block copy (IBC). FIG. 16B shows an example of Reconstruction-Reordered Intra Block Copy (RR-IBC). FIG. 17 shows an example of intra template matching prediction (IntraTMP) for predicting or determining a current block, according to some embodiments. FIG. 18 shows an example of decoder-side intra mode derivation (DIMD) for coding a current block, according to some embodiments. FIG. 19 shows an example of a template (eg., template area) for computing a histogram of gradient (HoG) used in DIMD, according to some embodiments. FIG. 20 shows an example owchart of the DIMD predictor derivation process, according to some embodiments. FIG. 21 shows an example of neighboring blocks of a current block used to determine a histogram, according to some embodiments. FIG. 22A shows an example owchart of a method for determining a merged HoG (MHoG) for a current block, according to some embodiments. FIG. 22B shows an example owchart of a method for determining a histogram of occurrences (HoC) for a current block, according to some embodiments. FIG. 23A shows an example of DIMD information from a plurality of (previously reconstructed) neighboring blocks of a current block, according to some embodiments. FIG. 23B shows an example graphical representation of combining the DIMD information from the plurality of neighboring blocks of FIG. 23A to generate an MHoG if the block was previously coded using the MIMD mode, according to some embodiments. FIG. 23C shows an example graphical representation of combining the DIMD information from the plurality of neighboring blocks of FIG. 23A to generate an HoC if the block was previously coded using the OBIC mode, according to some embodiments. FIG. 24A shows an example owchart of the DIMD Merge List mode for deriving a list of DIMD merge candidates, according to some embodiments. FIG. 24B shows a owchart of an example process for generating a history-based table of DIMD merge candidates, according to some embodiments. FIG. 25 shows an example of a matrix-based intra prediction (MIP) mode, according to some embodiments. FIG. 26 shows an example of templatebased intra mode derivation (TIMD) for coding a current block, according to some embodiments. FIG. 27A shows an example of a current block and neighboring blocks being coded in DIMDbased modes and nonangular modes, according to some embodiments. FIG. 27B shows an example of obtaining DIMD information from neighboring blocks of a current block that are not coded using a DIMDbased mode, according to some embodiments. FIG. 28A shows an example of a target block overlapping a reference block indicated by a BV obtained by a nonangular mode used to code candidate block, according to some embodiments. FIG. 28B shows an example of a plurality of target blocks overlapping reference block indicated by a BV obtained by a non-angular mode, according to some embodiments. FIG. 29 shows an example of a plurality of reference blocks indicated by a plurality of respective BVs obtained by an IntraTMP mode with fusion used to code candidate block, according to some embodiments. FIG. 30 shows an example of a target block overlapping a reference block indicated by a BV obtained by a non-angular mode associated with ipping in a direction and used to code candidate block, according to some embodiments. FIG. 31 shows a owchart of an example method for selecting DIMD merge candidates from neighboring blocks of a current block to generate a histogram used by a DIMDbased mode to code the current block, according to some embodiments. FIG. 32 shows a owchart of an example method for coding a current block based on an intrabased coding mode using blocks coded in a nonangular (coding) mode, according to some embodiment. FIG. 33 illustrates a block diagram of an example computer system in which embodiments of the present disclosure may be implemented. DETAILED DESCRIPTION In the following description, numerous specic details are set forth in order to provide a thorough understanding of the disclosure. However, it will be apparent to those skilled in the art that the disclosure, including structures, systems, and methods, may be practiced without these specic details. The description and representation herein are the common means used by those experienced or skilled in the art to most effectively convey the substance of their work to others skilled in the art. In other instances, well-known methods, procedures, components, and circuitry have not been described in detail to avoid unnecessarily obscuring aspects of the disclosure. References in the specication to one embodiment, an embodiment, an example embodiment, etc., indicate that the embodiment described may include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it is within the knowledge of one skilled in the art to affect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described. Also, it is noted that individual embodiments may be described as a process which is depicted as a owchart, a ow diagram, a data ow diagram, a structure diagram, or a block diagram. Although a owchart may describe the operations as a sequential process, many of the operations can be performed in parallel or concurrently. In addition, the order of the operations may be rearranged. A process is terminated when its operations are completed, but could have additional steps not included in a gure. A process may correspond to a method, a function, a procedure, a subroutine, a subprogram, etc. When a process corresponds to a function, its termination can correspond to a return of the function to the calling function or the main function. The term computer-readable medium includes, but is not limited to, portable or non- portable storage devices, optical storage devices, and various other mediums capable of storing, containing, or carrying instruction(s) and / or data. A computer-readable medium may include a non- transitory medium in which data can be stored and that does not include carrier waves and / or transitory electronic signals propagating wirelessly or over wired connections. Examples of a non-transitory medium may include, but are not limited to, a magnetic disk or tape, optical storage media such as compact disk (CD) or digital versatile disk (DVD), ash memory, memory or memory devices. A computerreadable medium may have stored thereon code and / or machine-executable instructions that may represent a procedure, a function, a subprogram, a program, a routine, a subroutine, a module, a software package, a class, or any combination of instructions, data structures, or program statements. A code segment may be coupled to another code segment or a hardware circuit by passing and / or receiving information, data, arguments, parameters, or memory contents. Information, arguments, parameters, data, etc. may be passed, forwarded, or transmitted via any suitable means including memory sharing, message passing, token passing, network transmission, or the like. Furthermore, embodiments may be implemented by hardware, software, rmware, middleware, microcode, hardware description languages, or any combination thereof. When implemented in software, rmware, middleware or microcode, the program code or code segments to perform the necessary tasks (eg., a computer-program product) may be stored in a computer-readable or machine- readable medium. A processor(s) may perform the necessary tasks. A video sequence, comprising multiple pictures / frames, may be represented in digital form for storage and / or transmission. Representing a video sequence in digital form may require a large quantity of bits. Large data sizes that may be associated with video sequences may require signicant resources for storage and / or transmission. Video encoding may be used to compress a size of a video sequence for more efcient storage and / or transmission. Video decoding may be used to decompress a compressed video sequence for display and / or other forms of consumption. FIG. 1 shows an example video coding / decoding system 100 in which embodiments of the present disclosure may be implemented. Video coding / decoding system 100 comprises a source device 102, a transmission medium 104, and a destination device 106. Source device 102 encodes a video sequence 108 into a bitstream 110 for more efcient storage and / or transmission. Source device 102 may store and / or send / transmit bitstream 110 to destination device 106 via transmission medium 104. Destination device 106 decodes bitstream 110 to display video sequence 108. Destination device 106 may receive bitstream 110 from source device 102 via transmission medium 104. Source device 102 and / or destination device 106 may be any of a plurality of different devices (e. g., a desktop computer, laptop computer, tablet computer, smart phone, wearable device, television, camera, video gaming console, set top box, video streaming device, etc.). Source device 102 may comprise (e.g., for encoding video sequence 108 into bitstream 110) one or more of a video source 112, an encoder 114, and / or an output interface 116. Video source 112 may provide and / or generate video sequence 108 based on a capture of a natural scene and / or a synthetically generated scene. A synthetically generated scene may be a scene comprising computer generated graphics and / or screen content. Video source 112 may comprise a video capture device (e.g., a video camera), a video archive comprising previously captured natural scenes and / or synthetically generated scenes, a video feed interface to receive captured natural scenes and / or synthetically generated scenes from a video content provider, and / or a processor to generate synthetic scenes. A video sequence, such as video sequence 108, may comprise a series of pictures (also referred to as frames). A video sequence may achieve an impression of motion based on successive presentation of pictures of the video sequence using a constant time interval or variable time intervals between the pictures. A picture may comprise one or more sample arrays of intensity values. The intensity values may be taken (e. g., measured, determined, provided) at a series of regularly spaced locations within a picture. A color picture may comprise (e.g., typically comprises) a luminance sample array and two chrominance sample arrays. The luminance sample array may comprise intensity values representing the brightness (e. g., luma component, Y) of a picture. The chrominance sample arrays may comprise intensity values that respectively represent the blue and red components of a picture (e. g., chroma components, Cb and Cr) separate from the brightness. Other color picture sample arrays may be possible based on different color schemes (e. g., a red, green, blue (RGB) color scheme). A pixel, in a color picture, may refer to / comprise / be associated with all intensity values (e.g., luma component, chroma components), for a given location, in the sample arrays (e.g., three sample arrays are used for one luma component and two chroma components, respectively) used to represent color pictures. A monochrome picture may comprise a single, luminance sample array. A pixel, in a monochrome picture, may refer to / comprise / be associated with the intensity value (e.g., luma component) at a given location in the single, luminance sample array used to represent monochrome pictures. Encoder 114 may encode video sequence 108 into bitstream 110. Encoder 114 may apply / use (eg., to encode video sequence 108) one or more prediction techniques to reduce redundant information in video sequence 108. Redundant information is information that may be predicted at a decoder and need not be transmitted to the decoder for accurate decoding of video sequence 108. For example, encoder 114 may apply spatial prediction (e. g., intraframe or intra prediction), temporal prediction (e. g., interframe prediction or inter prediction), interlayer prediction, and / or other prediction techniques to reduce redundant information in video sequence 108. Encoder 114 may partition pictures comprising video sequence 108 into rectangular regions referred to as blocks, for example, before applying one or more prediction techniques. Encoder 114 may then encode a block using the one or more of the prediction techniques. For temporal prediction, encoder 114 may search for a block similar to the block being encoded in another picture (e. g., referred to as a reference picture) of video sequence 108. The block determined during the search (e.g., referred to as a prediction block) may then be used to predict the block being encoded. For spatial prediction, encoder 114 may form a prediction block based on data from reconstructed neighboring samples of the block to be encoded within the same picture of Video sequence 108. A reconstructed sample refers to a sample that was encoded and then decoded. Encoder 114 may determine a prediction error (e.g., also referred to as a residual) based on the difference between a block being encoded and a prediction block. The prediction error may represent non-redundant information that may be sent / transmitted to a decoder for accurate decoding of video sequence 108. Encoder 114 may apply a transform to the prediction error (eg. using a discrete cosine transform (DCT), or any other transform) to generate transform coefcients. Encoder 114 may form bitstream 110 based on the transform coefcients and other information used to determine prediction blocks using / based on prediction types, motion vectors, and / or prediction modes. Encoder 114 may perform one or more of quantization and entropy coding of the transform coefcients and / or the other information used to determine the prediction blocks, for example, before forming bitstream 110. The quantization and / or the entropy coding may further reduce the quantity of bits needed to store and / or transmit video sequence 108. Output interface 116 may be congured to write and / or store bitstream 110 onto transmission medium 104 for transmission to destination device 106. In addition or altematively, output interface 116 may be congured to send / transmit, upload, and / or stream bitstream 110 to destination device 106 via transmission medium 104. Output interface 116 may comprise a wired and / or a wireless transmitter congured to send / transmit, upload, and / or stream bitstream 110 in accordance with one or more proprietary, open-source, and / or standardized communication protocols (e. g., Digital Video Broadcasting (DVB) standards, Advanced Television Systems Committee (ATSC) standards, Integrated Services Digital Broadcasting (ISDB) standards, Data Over Cable Service Interface Specication (DOCSIS) standards, 3rd Generation Partnership Project (3 GPP) standards, Institute of Electrical and Electronics Engineers (IEEE) standards, Internet Protocol (IP) standards, Wireless Application Protocol (WAP) standards, and / or any other communication protocol). Transmission medium 104 may comprise wireless, wired, and / or computer readable medium. For example, transmission medium 104 may comprise one or more wires, cables, air interfaces, optical discs, ash memory, and / or magnetic memory. In addition or alternatively, transmission medium 104 may comprise one or more networks (e. g., the intemet) or le servers congured to store and / or send / transmit encoded video data. Destination device 106 may decode bitstream 110 into video sequence 108 for display. Destination device 106 may comprise one or more of an input interface 118, a decoder 120, and / or a Video display 122. Input interface 118 may be congured to read bitstream 110 stored on transmission medium 104 by source device 102. In addition or alternatively, input interface 118 may be congured to receive, download, and / or stream bitstream 110 from source device 102 via transmission medium 104. Input interface 118 may comprise a wired and / or a wireless receiver congured to receive, download, and / or stream bitstream 110 in accordance with one or more proprietary, opensource, standardized communication protocols, and / or any other communication protocol (e.g., such as referenced herein). Decoder 120 may decode video sequence 108 from encoded bitstream 110. The decoder 120 may generate prediction blocks for pictures of video sequence 108 in a similar manner as encoder 114 and determine the prediction errors for the blocks, for example, to decode video sequence 108. Decoder 120 may generate the prediction blocks using / based on prediction types, prediction modes, and / or motion vectors received in bitstream 110. Decoder 120 may determine the prediction errors using the transform coefcients received in bitstream 110. Decoder 120 may determine the prediction errors by weighting transform basis functions using the transform coefcients. Decoder 120 may combine the prediction blocks and the prediction errors to decode video sequence 108. Video sequence 108 at the destination device 106 may be, or may not necessarily be, the same video sequence sent, such as video sequence 108 as sent by the source device 102. Decoder 120 may decode a video sequence that approximates video sequence 108, for example, because of lossy compression of video sequence 108 by encoder 114 and / or errors introduced into encoded bitstream 110 during transmission to destination device 106. Video display 122 may display video sequence 108 to a user. Video display 122 may comprise a cathode rate tube (CRT) display, a liquid crystal display (LCD), a plasma display, a light emitting diode (LED) display, and / or any other display device suitable for displaying video sequence 108. Video coding / decoding system 100 is merely an example and video encoding / decoding systems different from the video coding / decoding system 100 and / or modied versions of the video coding / decoding system 100 may similarly perform the methods and processes as described herein. For example, the video coding / decoding system 100 may comprise other components and / or arrangements. For example, video source 112 may be external to source device 102. Similarly, video display 122 may be external to destination device 106 or omitted altogether (e. g., if video sequence 108 is intended for consumption by a machine and / or storage device). In an example, source device 102 may further comprise a video decoder and destination device 106 may further comprise a video encoder. For example, source device 102 may be congured to further receive an encoded bitstream from destination device 106 to support two-way video transmission between the devices. Encoder 114 and / or decoder 120 may operate according to one or more proprietary or industry video coding standards. For example, encoder 114 and / or decoder 120 may operate in accordance with one or more proprietary, opensource, and / or standardized protocols (e. g., International Telecommunications Union Telecommunication Standardization Sector (ITUT) H.263, ITUT H.264 and Moving Picture Expert Group (MPEG)-4 Visual (also known as Advanced Video Coding (AVC)), ITUT H.265 and MPEGH Part 2 (also known as High Efciency Video Coding (HEVC)), ITUT H.265 and MPEG-I Part 3 (also known as Versatile Video Coding (VVC)), the WebM VP8 and VP9 codecs, and / or AOMedia Video 1 (AVl), and / or any other video coding protocol). FIG. 2 shows an example encoder. Encoder 200 as shown in FIG. 2 may implement one or more processes described herein. Encoder 200 may encode a video sequence 202 into a bitstream 204 for more efcient storage and / or transmission. Encoder 200 may be implemented in video coding / decoding system 100 as shown in FIG. 1 (eg., as encoder 114) or in any computing, communication, or electronic device (eg., desktop computer, laptop computer, tablet computer, smart phone, wearable device, television, camera, video gaming console, set-top box, video streaming device, etc.). Encoder 200 may comprise one or more of an inter prediction unit 206, an intra prediction unit 208, combiners 210 and 212, a transform and quantization unit (TR + Q) 214, an inverse transform and quantization unit (iTR + iQ) 216, an entropy coding unit 218, one or more lters 220, and / or a buffer 222. Encoder 200 may partition pictures (e. g., frames) of (e.g., comprising) video sequence 202 into blocks and encode video sequence 202 on a block-by-block basis. Encoder 200 may perform / apply a prediction technique on a block being encoded using either inter prediction unit 206 or intra prediction unit 208. Inter prediction unit 206 may perform inter prediction by searching for a block similar to the block being encoded in another, reconstructed picture (e.g., a reference picture) of video sequence 202. A reconstructed picture refers to a picture that was encoded and then decoded. The block determined during the search (e. g., referred to as a prediction block) may then be used to predict the block being encoded to remove redundant information. Inter prediction unit 206 may exploit temporal redundancy or similarities in scene content from picture to picture in video sequence 202 to determine the prediction block. For example, scene content between pictures of video sequence 202 may be similar except for differences due to motion and / or afne transformation of the screen content over time. Intra prediction unit 208 may perform intra prediction by forming a prediction block based on data from reconstructed neighboring samples of the block to be encoded within the same picture of video sequence 202. A reconstructed sample refers to a sample that was encoded and then decoded. Intra prediction unit 208 may exploit spatial redundancy or similarities in scene content within a picture of video sequence 202 to determine the prediction block. For example, the texture of a region of scene content in a picture may be similar to the texture in the immediate surrounding area of the region of the scene content in the same picture. Combiner 210 may determine a prediction error (e. g., referred to as a residual) based on the difference between the block being encoded and the prediction block. The prediction error may represent non-redundant information that may be sent / transmitted to a decoder for accurate decoding of video sequence 202. Transform and quantization unit (TR + Q) 214 may transform and quantize the prediction error. Transform and quantization unit 214 may transform the prediction error into transform coefcients by applying, for example, a DCT to reduce correlated information in the prediction error. Transform and quantization unit 214 may quantize the coefcients by mapping data of the transform coefcients to a predened set of representative values. Transform and quantization unit 214 may quantize the coefcients to reduce irrelevant information in bitstream 204. The irrelevant information refers to information that may be removed from the coefcients without producing visible and / or perceptible distortion in video sequence 202 after decoding (e.g., at a receiving device). Entropy coding unit 218 may apply one or more entropy coding methods to the quantized transform coefcients to further reduce the bit rate. For example, entropy coding unit 218 may apply context adaptive variable length coding (CAVLC), context adaptive binary arithmetic coding (CABAC), and / or syntax-based context-based binary arithmetic coding (SBAC). The entropy coded coefcients may be packed to form bitstream 204. l3 Inverse transform and quantization unit (iTR + iQ) 216 may inverse quantize and inverse transform the quantized transform coefcients to determine a reconstructed prediction error. Combiner 212 may combine the reconstructed prediction error with the prediction block to form a reconstructed block. Filter(s) 220 may lter the reconstructed block, for example, using a deblocking lter and / or a sample-adaptive offset (SAO) lter. Buffer 222 may store the reconstructed block for prediction of one or more other blocks in the same and / or different picture of video sequence 202. Encoder 200 may further comprise an encoder control unit. The encoder control unit may be congured to control one or more units of encoder 200 as shown in FIG. 2. The encoder control unit may control the one or more units of encoder 200 such that bitstream 204 may be generated in conformance with the requirements of one or more proprietary coding protocols, industry video coding standards, and / or any other video cording protocol. For example, the encoder control unit may control the one or more units of encoder 200 such that bitstream 204 may be generated in conformance with one or more of ITUT H.263, AVC, HEVC, VVC, VP8, VP9, AVl, and / or any other video coding standard / format. The encoder control unit may be congured to attempt to minimize (or reduce) the bitrate of bitstream 204 and / or maximize (or increase) the reconstructed video quality (e. g., within the constraints of a proprietary coding protocol, industry video coding standard, and / or any other video cording protocol). For example, the encoder control unit may be congured to attempt to minimize or reduce the bitrate of bitstream 204 such that the reconstructed video quality does not fall below a certain level / threshold, and / or to maximize or increase the reconstructed video quality such that the bitrate of bitstream 204 does not exceed a certain level / threshold. The encoder control unit may determine / control one or more of: partitioning of the pictures of video sequence 202 into blocks, whether a block is inter predicted by inter prediction unit 206 or intra predicted by intra prediction unit 208, a motion vector for inter prediction of a block, an intra prediction mode among a plurality of intra prediction modes for intra prediction of a block, ltering performed by lter(s) 220, and / or one or more transform types and / or quantization parameters applied by transform and quantization unit 214. The encoder control unit may determine / control one or more of the above based on a ratedistortion measure for a block or picture being encoded. The encoder control unit may determine / control one or more of the above to reduce the rate- distortion measure for a block or picture being encoded. The prediction type used to encode a block (intra or inter prediction), prediction information of the block (intra prediction mode if intra predicted, motion vector, etc.), and / or transform and / or quantization parameters, may be sent to entropy coding unit 218 to be further compressed (e. g., to reduce the bitrate). For example, entropy coding unit 218 may apply context adaptive variable length coding (CAVLC), context adaptive binary arithmetic coding (CABAC), and / or syntaxbased context based binary arithmetic coding (SBAC) to achieve further compression. The prediction type, prediction information, and / or transform and / or quantization parameters may be packed with the prediction error to form bitstream 204. Encoder 200 is merely an example and encoders different from encoder 200 and / or modied versions of encoder 200 may perform the methods and processes as described herein. For example, encoder 200 may comprise other components and / or arrangements. One or more of the components shown in FIG. 2 may be optionally included in encoder 200 (e.g., entropy coding unit 218 and / or lters(s) 220). FIG. 3 shows an example decoder. A decoder 300 as shown in FIG. 3 may implement one or more processes described herein. Decoder 300 may decode a bitstream 302 into a decoded video sequence 304 for display and / or some other form of consumption. Decoder 300 may be implemented in video coding / decoding system 100 in FIG. 1 and / or in a computing, communication, or electronic device (e. g., desktop computer, laptop computer, tablet computer, smart phone, wearable device, television, camera, video gaming console, settop box, and / or video streaming device). Decoder 300 may comprise an entropy decoding unit 306, an inverse transform and quantization (iTR + iQ) unit 308, a combiner 310, one or more lters 312, a buffer 314, an inter prediction unit 316, and / or an intra prediction unit 318. Decoder 300 may comprise a decoder control unit congured to control one or more units of decoder 300. The decoder control unit may control the one or more units of decoder 300 such that bitstream 302 is decoded in conformance with the requirements of one or more proprietary coding protocols, industry video coding standards, and / or any other communication protocol. For example, the decoder control unit may control the one or more units of decoder 300 such that the bitstream 302 is decoded in conformance with one or more of ITU-T H.263, AVC, HEVC, VVC, VP8, VP9, AVl, and / or any other video coding standard / format. The decoder control unit may determine / control one or more of: whether a block is inter predicted by inter prediction unit 316 or intra predicted by intra prediction unit 318, a motion vector for inter prediction of a block, an intra prediction mode among a plurality of intra prediction modes for intra prediction of a block, ltering performed by lter(s) 312, and / or one or more inverse transform types and / or inverse quantization parameters to be applied by inverse transform and quantization unit 308. One or more of the control parameters used by the decoder control unit may be packed in bitstream 302. Entropy decoding unit 306 may entropy decode the bitstream 302. For example, entropy decoding unit 306 may apply context adaptive variable length coding (CAVLC), context adaptive binary arithmetic coding (CABAC), and syntaxbased contextbased binary arithmetic coding (SBAC) to decompress the prediction type used to encode a block (intra or inter prediction), prediction information of the block (intra prediction mode if intra predicted, motion vector, etc.), and transform and quantization parameters. Inverse transform and quantization unit 308 may inverse quantize and / or inverse transform the quantized transform coefcients to determine a decoded prediction error. Combiner 310 may combine the decoded prediction error with a prediction block to form a decoded block. The prediction block may be generated by intra prediction unit 318 or inter prediction unit 316 (e. g., as described above with respect to encoder 200 in FIG 2). Filter(s) 312 may lter the decoded block, for example, using a deblocking lter and / or a sample-adaptive offset (SAO) lter. Buffer 314 may store the decoded block for prediction of one or more other blocks in the same and / or different picture of the video sequence in bitstream 302. Decoded video sequence 304 may be output from lter(s) 312 as shown in FIG. 3. Decoder 300 is merely an example and decoders different from decoder 300 and / or modied versions of decoder 300 may perform the methods and processes as described herein. For example, decoder 300 may have other components and / or arrangements. One or more of the components shown in FIG. 3 may be optionally included in decoder 300 (e.g., entropy decoding unit 306 and / or lters(s) 312). Although not shown in FIGS. 2 and 3, each of encoder 200 and decoder 300 may further comprise an intra block copy unit in addition to inter prediction and intra prediction units. The intra block copy unit may perform / operate similar to an inter prediction unit but may predict blocks within the same picture. For example, the intra block copy unit may exploit repeated patterns that appear in screen content. The screen content may include computer generated text, graphics, animation, etc. Video encoding and / or decoding may be performed on a blockbyblock basis. The process of partitioning a picture into blocks may be adaptive based on the content of the picture. For example, larger block partitions may be used in areas of a picture with higher levels of homogeneity to improve coding efciency. A picture (e. g., in HEVC, or any other coding standard / format) may be partitioned into non-overlapping square blocks, which may be referred to as coding tree blocks (CTBs). The CTBs may comprise samples of a sample array. A CTB may have a size of 2nx2n samples, where n may be specied by a parameter of the encoding system. For example, n may be 4, 5, 6, or any other value. A CTB may have any other size. A CTB may be further partitioned by a recursive quadtree partitioning into coding blocks (CBS) of half vertical and half horizontal size. The CTB may form the root of the quadtree. A CB that is not split further as part of the recursive quadtree partitioning may be referred to as a leaf CB of the quadtree, and otherwise may be referred to as a non-leaf CB of the quadtree. A CB may have a minimum size specied by a parameter of the encoding system. For example, a CB may have a minimum size of 4x4, 8x8, 16x16, 32x32, 64x64 samples, or any other minimum size. A CB may be further partitioned into one or more prediction blocks (PBs) for performing inter and / or intra prediction. A PB may be a rectangular block of samples on which the same prediction type / mode may be applied. A CB may also be further partitioned into intra subpartitions (ISP) where the reconstructed samples of each subpartition are available to generate the prediction of the next subpartition. For example, a CB may be split into 2 to 4 subpartitions. For transformations, a CB may be partitioned into one or more transform blocks (TBS). A TB may be a rectangular block of samples that may determine / indicate an applied transform size. FIG. 4 shows an example quadtree partitioning of a CTB 400. FIG. 5 shows an example quadtree 500 corresponding to the example quadtree partitioning of CTB 400 in FIG. 4. As shown in the examples of FIGS. 4 and 5, CTB 400 may rst be partitioned into four CBs of half vertical and half horizontal size. Three of the resulting CBS of the rst level partitioning of CTB 400 are leaf CBs. The three leaf CBs of the rst level partitioning of CTB 400 are respectively labeled 7, 8, and 9 in FIGS. 4 and 5. The non-leaf CB of the rst level partitioning of CTB 400 is partitioned into four sub-CBS of half vertical and half horizontal size. Three of the resulting sub-CBS of the second level partitioning of CTB 400 are leaf CBs. The three leaf CBS of the second level partitioning of CTB 400 are respectively labeled 0, 5, and 6 in FIGS. 4 and 5. Finally, The non-leaf CB of the second level partitioning of CTB 400 is partitioned into four leaf CBS of half vertical and half horizontal size. The four leaf CBs are respectively labeled 1, 2, 3, and 4 in FIGS. 4 and 5. The example CTB 400 of FIG. 4 is partitioned into 10 leaf CBs respectively labeled 0-9, but may be partitioned into other quantities of leaf CBs. The 10 leaf CBs may correspond to 10 CB leaf nodes (e. g., 10 CB leaf nodes of quadtree 500 as shown in FIG. 5). In other examples, a CTB may be partitioned into a different number of leaf CBS. The resulting quadtree partitioning of CTB 400 may be scanned using a z-scan (e. g., left-to-right, toptobottom) to form the sequence order for encoding / decoding the CB leaf nodes. A numeric label (e. g., indicator, index) of each CB leaf node in FIGS. 4 and 5 may correspond to the sequence order for encoding / decoding. For example, CB leaf node 0 may be encoded / decoded rst and CB leaf node 9 may be encoded / decoded last. Although not shown in FIGS. 4 and 5, each CB leaf node may comprise one or more PBS and / or TBS. A picture, in VVC (or in any other coding standard / format), may be partitioned in a similar manner (such as in HEVC). A picture may be rst partitioned into nonoverlapping square CTBS. The CTBS may then be partitioned, using a recursive quadtree partitioning, into CBS of half vertical and half horizontal size. A quadtree leaf node (e.g., in VVC) may be further partitioned by a binary tree or ternary tree partitioning (or any other partitioning) into CBS of unequal SizeS. FIG. 6 shows example binary tree and ternary tree partitions. A binary tree partition may divide a parent block in half in either a vertical direction 602 or a horizontal direction 604. The resulting partitions may be half in Size as compared to the parent block. In other examples, the resulting partitions may correspond to sizes that are less than and / or greater than half of the parent block size. A temary tree partition may divide a parent block into three parts in either a vertical direction 606 or a horizontal direction 608. FIG. 6 shows an example in which the middle partition may be twice as large as the other two end partitions in the ternary tree partitions. In other examples, partitions may be of other sizes relative to each other and to the parent block. Binary and ternary tree partitions are examples of multitype tree partitioning. Multitype tree partitions may comprise partitioning a parent block into other quantities of smaller blocks. The block partitioning strategy (e.g., in VVC) may be referred to as a combination of quadtree and multitype tree partitioning (quadtree + multitype tree partitioning) because of the addition of binary and / or ternary tree partitioning to quadtree partitioning. FIG. 7 shows an example of combined quadtree and multi-type tree partitioning of a CTB 700. FIG. 8 shows an example tree 800 corresponding to the combined quadtree and multi-type tree partitioning of CTB 700 shown in FIG. 7. In both FIGS. 7 and 8, quadtree splits are shown in solid lines and multi-type tree splits are shown in dashed lines. For ease of explanation, CTB 700 is shown with the same quadtree partitioning as the CTB 400 described in FIG. 4, and a description of the quadtree partitioning of CTB 700, which iS Similar to that for CTB 400, is omitted. The quadtree partitioning of the CTB 700 iS merely an example and a CTB may be quadtree partitioned in a manner different from the CTB 700. Additional multi-type tree partitions of CTB 700 may be made relative to three leaf CBs Shown in FIG. 4. The three leaf CBs in FIG. 4 that are shown in FIG. 7 as being further partitioned may be leaf CBS 5, 8, and 9. The three leaf CBS may be further partitioned using one or more binary and / or ternary tree partitions. The leaf CB 5 of FIG. 4 may be partitioned into two CBS based on a vertical binary tree partitioning. The two resulting CBS may be leaf CBs respectively labeled 5 and 6 in FIGS. 7 and 8. The leaf CB 8 of FIG. 4 may be partitioned into three CBs based on a vertical ternary tree partition. Two of the three resulting CBS may be leaf CBS respectively labeled 9 and 14 in F IGS. 7 and 8. The remaining, nonleaf CB may be partitioned rst into two CBS based on a horizontal binary tree partition. One of the two CBS may be a leaf CB labeled 10. The other of the two CBS may be further partitioned into three CBS based on a vertical ternary tree partition. The resulting three CBS may be leaf CBS respectively labeled 11, 12, and 13 in F IGS. 7 and 8. The leaf CB 9 of FIG. 4 may be partitioned into three CBS based on a horizontal ternary tree partition. Two of the three CBS may be leaf CBS respectively labeled 15 and 19 in FIGS. 7 and 8. The remaining, nonleaf CB may be partitioned into three CBS based on another horizontal ternary tree partition. The resulting three CBs may all be leaf CBS respectively labeled 16, 17, and 18 in FIGS. 7 and 8. Altogether, CTB 700 may be partitioned into 20 leaf CBs respectively labeled 0-19. The 20 leaf CBS may correspond to 20 leaf nodes (e. g., 20 leaf nodes of tree 800 shown in FIG. 8). The resulting combination of quadtree and multi-type tree partitioning of the CTB 700 may be scanned using a z-scan (left-to-right, top-to-bottom) to form the sequence order for encoding / decoding the CB leaf nodes. A numeric label of each CB leaf node in FIGS. 7 and 8 may correspond to the sequence order for encoding / decoding, with CB leaf node 0 encoded / decoded rst and CB leaf node 19 encoded / decoded last. Although not shown in FIGS. 7 and 8, it should be noted that each CB leaf node may comprise one or more PBs and / or TBS. A coding standard / format (e. g., HEVC, VVC, or any other coding Standard / format) may dene various units (e.g., in addition to specifying various blocks (e.g., CTBS, CBS, PBS, TBS)). Blocks may comprise a rectangular area of samples in a sample array. Units may comprise the collocated blocks of samples from the different sample arrays (e.g., luma and chroma sample arrays) that form a picture as well as syntax elements and prediction data of the blocks. A coding tree unit (CTU) may comprise the collocated CTBS of the different sample arrays and may form a complete entity in an encoded bitstream. A coding unit (CU) may comprise the collocated CBS of the different sample arrays and syntax structures used to code the samples of the CBS. A prediction unit (PU) may comprise the collocated PBS of the different sample arrays and syntax elements used to predict the PBS. A transform unit (TU) may comprise TBS of the different samples arrays and syntax elements used to transform the TBS. A block may refer to any of a CTB, CB, PB, TB, CTU, CU, PU, and / or TU (e.g., in the context of HEVC, VVC, or any other coding format / standard). A block may be used to refer to similar data structures in the context of any video coding format / Standard / protocol. For example, a block may refer to a macroblock in the AVC standard, a macroblock or a sub-block in the VP8 coding format, a l8 superblock or a sub-block in the VP9 coding format, and / or a superblock or a sub-block in the AVl coding format. In intra prediction, samples of a block to be encoded (e.g., also referred to as a current block) may be predicted from samples in a line of samples immediately adjacent to the current block. For example, the line of samples may include samples of the column immediately adjacent to the left-most column of the current block and samples of the row immediately adjacent to the top-most row of the current block. The samples from the immediately adjacent column and row may be jointly referred to as reference samples. Each sample of the current block may be predicted (e. g., in an intra prediction mode) by proj ecting the position of the sample in the current block in a given direction to a point along the reference samples. The sample may be predicted by interpolating between the two closest reference samples of the projection point if the projection does not fall directly on a reference sample. A prediction error (e. g., referred to as a residual) may be determined for the current block based on differences between the predicted sample values and the original sample values of the current block. Predicting samples and determining a prediction error based on a difference between the predicted samples and original samples may be performed (e. g., at an encoder) for a plurality of different intra prediction modes (e. g., including non-directional intra prediction modes). The encoder may select one of the plurality of intra prediction modes and its corresponding prediction error to encode the current block. The encoder may send an indication of the selected prediction mode and its corresponding prediction error to a decoder for decoding of the current block. The decoder may decode the current block by predicting the samples of the current block, using the intra prediction mode indicated by the encoder, and / or combining the predicted samples with the prediction error. FIG. 9 shows an example set of reference samples 902 determined for intra prediction of a current block 904. Current block 904 may correspond to a block being encoded and / or decoded. Current block 904 may correspond to block 3 of partitioned CTB 700 as shown in FIG. 7. AS described herein, the numeric labels 0-19 of the blocks of partitioned CTB 700 may correspond to the sequence order for encoding / decoding the blocks and may be used as such in the example of FIG. 9. In some embodiments, reference samples 902 may include a line of samples immediately adjacent to current block 904 and include samples from a column and a row immediately adjacent to current block 904. For example, the line of samples may include reference samples to the left and / or above current block 904. In some embodiments, reference samples 902 may be obtained (or selected) from a reference line of multiple reference lines (MRL), which may include a line of samples adjacent to current block 904 and also a line of nonadj acent samples. The MRL may include reference lines identied by corresponding reference line indices that indicate an i-th line of samples adjacent to current block 904 such that the Oth line indicates the reference line immediate adjacent (or closest) to current block 904 and a higher numbered íth line indicates a line of samples further away from current block 904. An encoder may select a reference line from a set of MRL and signal an MLR index in the bitstream to indicate the selected reference line. For example, the encoder may signal a codeword encoding the l9 MRL index. The decoder may decode the codeword to determine the MRL index that identies a specic reference line used in intra prediction of current block 904. For current block 904 that is w x h samples in size, reference samples 902 may comprise: 2w samples (or any other quantity of samples) of an i-th row (eg., indicated by an MRL index) adjacent to the top-most row of current block 904, 2h samples (or any other quantity of samples) of the i-th column adjacent to the left-most column of current block 904, and the top left neighboring corner sample(s) extending from the i-th column and i-th row with respect to current block 904. Current block 904 may be square, such that w = h = s. In other examples, a current block need not be square, such that w ;& h. Available samples from neighboring blocks of current block 904 may be used for constructing the set of reference samples 902. Samples may not be available for constructing the set of reference samples 902, for example, if the samples lie outside the picture of the current block, the samples are part of a different slice of the current block (eg., if the concept of slices is used), and / or the samples belong to blocks that have been inter coded and constrained intra prediction is indicated. Intra prediction may not be dependent on inter predicted blocks, for example, if constrained intra prediction is indicated. Samples that may not be available for constructing the set of reference samples 902 may comprise samples in blocks that have not already been encoded and reconstructed at an encoder and / or decoded at a decoder based on the sequence order for encoding / decoding. Restriction of such samples from inclusion in the set of reference samples 902 may allow identical prediction results to be determined at both the encoder and decoder. In the example of FIG. 9, samples from neighboring blocks 0, l, 2, and 8 may be available to construct reference samples 902 given that these blocks are encoded and reconstructed at an encoder and decoded at a decoder prior to coding of current block 904. The samples from neighboring blocks 0, l, 2, and 8 may be available to construct reference samples 902, for example, if there are no other issues (e. g., as mentioned above) preventing the availability of the samples from the neighboring blocks 0, l, 2, and 8. The portion of reference samples 902 from neighboring block 6 may not be available due to the sequence order for encoding / decoding (e.g., because the block 6 may not have already been encoded and reconstructed at the encoder and / or decoded at the decoder based on the sequence order for encoding / decoding). In some examples, unavailable samples from reference samples 902 may be lled with one or more of the available reference samples 902. For example, an unavailable reference sample may be lled with a nearest available reference sample. The nearest available reference sample may be determined by moving in a clockwise direction through reference samples 902 from the position of the unavailable reference. The reference samples 902 may be lled with the midvalue of the dynamic range of the picture being coded, for example, if no reference samples are available. Samples of current block 904 may be intra predicted based on reference samples 902, for example, based on (e. g., after) determination and (optionally) ltering of reference samples 902. In some examples, a ltering scheme (e.g., a ltering algorithm) may be applied to reference samples 902 to improve prediction accuracy. The ltering scheme may be one of a plurality of lter types including at least: a smoothing lter (or reference sample smoothing lter) or an interpolation lter. In some examples, if reference samples of a given block are to be ltered, only one of the plurality of lter types iS selected (e.g., activated) to be applied to the reference samples. For example, if the smoothing lter iS selected (e.g., activated), the interpolation lter is not selected (e.g., disabled) or vice versa. Many encoders / decoders may support a plurality of intra prediction modes in accordance with one or more video coding standards. For example, HEVC supports 35 intra prediction modes, including a planar mode, a direct current (DC) mode, and 33 angular modes. VVC supports 67 intra prediction modes, including a planar mode, a DC mode, and 65 angular modes. Planar and DC modes may be used to predict smooth and gradually changing regions of a picture. Angular modes may be used to predict directional structures in regions of a picture. Any quantity of intra prediction modes may be supported. FIGS. 10AB show example intra prediction modes. FIG. 10A shows 35 intra prediction modes, such as supported by HEVC. The 35 intra prediction modes may be indicated / identied by indices 0 to 34. Prediction mode 0 may correspond to planar mode. Prediction mode 1 may correspond to DC mode. Prediction modes 2-34 may correspond to angular modes. Prediction modes 2-18 may be referred to as horizontal prediction modes because the principal source of prediction is in the horizontal direction. Prediction modes 1934 may be referred to as vertical prediction modes because the principal source of prediction is in the vertical direction. FIG. 10B Shows 67 intra prediction modes, such as supported by VVC. The 67 intra prediction modes may be indicated / identied by indices 0 to 66. Prediction mode 0 may correspond to planar mode. Prediction mode 1 corresponds to DC mode. Prediction modes 2-66 may correspond to angular modes. Prediction modes 2-34 may be referred to as horizontal prediction modes because the principal source of prediction is in the horizontal direction. Prediction modes 35-66 may be referred to as vertical prediction modes because the principal source of prediction is in the vertical direction. Some of the intra prediction modes illustrated in FIG. 10B may be adaptively replaced by wide-angle directions because blocks in VVC need not be squares. FIG. 11 shows a current block 904 and corresponding reference samples 902 from FIG. 9. To further describe how intra prediction modes are applied to determine a prediction (e. g., a prediction block) of current block 904, FIG. 11 shows current block 904 and reference samples 902, from a reference line among a set of multiple reference lines (MRL) 908912, in a twodimensional x, y plane, where a sample may be referenced as p [x] [y]. To Simplify the prediction process, reference samples 902 may be placed in two, onedimensional arrays. The reference samples 902 belonging to a reference line I from the set of MRL 908-912, above the current block 904, may be placed in the one-dimensional array mfl [x]: mmx] = P[I + x] [11:06 î U} (1) The reference samples 902 belonging to reference line ], to the left of current block 904, may be placed in the one-dimensional array TEE-2U]: FF-fab] = P[1][l+ JF]! (T E U} (2) The variable [ represents how many lines away the selected reference line is from current block. For example, if reference line #0 908 is selected, then I is set to 1 to indicate the reference line adjacent to current block 904. For example, if reference line #1 910 is selected, then l is set to 2. For example, if reference line #2 912 is selected, then l is set to 3. In some examples, if MRL is not activated or selected, then reference samples 902 may be from reference line #0 908 that is immediately adjacent to current block 904. In this example, the variable l in Equations (l) and (2) is set to l. The prediction process may comprise determination of a predicted sample p[x] [y] (e.g., a predicted value) at a location [x] [y] in current block 904. For planar mode, a sample at the location [x] [y] in current block 904 may be predicted by determining / calculating the mean of two interpolated values. The rst of the two interpolated values may be based on a horizontal linear interpolation at the location [x] [y] in current block 904. The second of the two interpolated values may be based on a vertical linear interpolation at location [x] [y] in current block 904. The predicted sample p[x] [y] in current block 904 may be determined / calculated as: 1 FEB] = fxlb] + v[x][?] + S]. (3) where hExHy] = (5 x 1] - refzb'] + (x + 1) 'ref1[s] (4) may be the horizonal linear interpolation at the location [x] [y] in current block 904 and 1?[Mlbr] = (5 - ÿ 1) ' MEDIC] + (Y + 1) 'MÆS] (5) may be the vertical linear interpolation at the location [x] [y] in current block 904. s may be equal to a length of a side (e.g., a number of samples on a side) of the current block 904. For DC mode, a sample at a location [x] [y] in current block 904 may be predicted by the mean of the reference samples 902. The predicted sample p[x] [y] in current block 904 may be determined / calculated as: 1 3-1 3-1 pmm = ; Zwam +Zffzbf1 . (6) FD _}'=D For angular modes, a sample at a location [x] [y] in current block 904 may be predicted by projecting the location [x] [y] in a direction specied by a given angular mode to a point on the horizontal or vertical line of samples comprising reference samples 902. The sample at the location [x] [y] may be predicted by interpolating between the two closest reference samples of the projection point if the projection does not fall directly on a reference sample. The direction specied by the angular mode may be given by an angle (p dened relative to the yaxis for vertical prediction modes (e.g., modes 1934 in HEVC and modes 3566 in VVC). The direction specied by the angular mode may be given by an angle (p dened relative to the xaxis for horizontal prediction modes (e. g., modes 21 8 in HEVC and modes 2-34 in VVC). FIG. 12 shows an example of applying an intra prediction mode (eg., an angular mode such as vertical prediction mode 906) for prediction of a current block 904. FIG. 12 specically shows prediction of a sample at a location [x] [y] in current block 904 for a vertical prediction mode 906. Vertical prediction mode 906 may be given by an angle (p with respect to the vertical axis. The location [x] [y] in current block 904, in vertical prediction modes, may be projected to a point (e. g., referred to as a projection point) on the horizontal line of reference samples rug-fl [x]. The reference samples 902 are only partially shown in FIG. 12 and shown as being from a reference line with reference line index of 0 for ease of illustration. Reference samples 902 may be from another reference line of the set of MRL, as explained in FIG. 9. As shown in FIG. 12, the projection point on the horizontal line of reference samples n°.-fl [x] may not be exactly on a reference sample. A predicted sample p [x] [y] in current block 904 may be determined / calculated by linearly interpolating between the two reference samples, for example, if the projection point falls at a fractional sample position between two reference samples. The predicted sample p [x] DJ] may be determined / calculated as: p[x][y] = (1 if] - Tef1[x+ i,- + 1] + i;- refx + i,- + 2]. (7) it. may be the integer part of the horizontal displacement of the projection point relative to the location [x] [y]. i.:- may be determined / calculated as a function of the tangent of the angle (p of the vertical prediction mode 906 as: i,- = L(J='+ Ü ' tamp]- (8) if may be the fractional part of the horizontal displacement of the projection point relative to the location [x] [y] and may be determined / calculated aS: (9) 1] - tam], 1) 'tan al] - L(ÿ+ if = (@+ where |_ - ] iS the integer oor function. For horizontal prediction modes, a location [x][y] of a sample in current block 904 may be projected onto the vertical line of reference samples rgfz [y]. A predicted sample ;:

[33] [);]for horizontal prediction modes may be determined / calculated as: PDC] [J] = (1 _ if} ' Tfzfÿ+ ii + 1] + lrf' refZDr-I i: + 2]- (10) it. may be the integer part of the vertical displacement of the proj ection point relative to the location [x] [y]. iimay be determined / calculated as a function of the tangent of the angle (p of the horizontal prediction mode as: il- =|_(x+1]-tancp]. (11) if may be the fractional part of the vertical displacement of the projection point relative to the location [x] [y]. ifmay be determined / calculated as: if =((x+1]-tanqa] |_(x+ ljl-tanrp], (12) where |_ - J is the integer oor function. The interpolation functions given by Equations (7) and (10) may be implemented by an encoder and / or a decoder (e.g., encoder 200 in FIG. 2 and / or decoder 300 in FIG. 3). The interpolation functions may be implemented by nite impulse response (FIR) lters. For example, the interpolation functions may be implemented as a set of two-tap FIR lters. The coefcients of the two-tap FIR lters may be respectively given by (l-ii) and if. The predicted sample p [x] [y], in angular intra prediction, may be calculated with some predened level of sample accuracy (e. g., 1 / 32 sample accuracy, or accuracy dened by any other metric). For l / 32 sample accuracy, the set of two-tap FIR interpolation lters may comprise up to 32 different two-tap FIR interpolation lters _ one for each of the 32 possible values of the fractional part of the projected displacement ij. In other examples, different levels of sample accuracy may be used. In some examples, the FIR lters may be used for predicting chroma samples and / or luma samples. For example, the two-tap interpolation FIR lter may be used for predicting chroma samples and a same and / or a different interpolation technique / lter may be used for luma samples. For example, a fourtap FIR lter may be used to determine a predicted value of a luma sample. Coefcients of the four tap FIR lter may be determined based on il (e.g., similar to the two-tap FIR lter). For 1 / 32 sample accuracy, a set of 32 different four-tap FIR lters may comprise up to 32 different four-tap FIR lters _ one for each of the 32 possible values of the fractional part of the projected displacement II]. In other examples, different levels of sample accuracy may be used. The set of four-tap FIR lters may be stored in a look-up table (LUT) and referenced based on ii. A predicted sample ;: [x] [y], for vertical prediction modes, may be determined based on the four-tap FIR lter as: 3 (13) Mac] Ly] = Zeta] - matx + Haix +f1. |E=IZI where fT[i], i = 0. . .3, may be the lter coefcients, and Mx is integer displacement. A predicted sample p [x] Ly], for horizontal prediction modes, may be determined based on the four-tap FIR lter as: 3 (14) ptx1m= ZfTIil-mfzbf+ Haix +£1- |E=EI Supplementary reference samples may be determined / constructed if the location [x] [y] of a sample in current block 904 to be predicted is projected to a negative x coordinate. The location [x] [y] of a sample may be projected to a negative x coordinate, for example, if negative vertical prediction angles (p are used. The supplementary reference samples may be determined / constructed by projecting the reference samples in refz [y] in the vertical line of reference samples 902 to the horizontal line of reference samples 902 using the negative vertical prediction angle (p. Supplementary reference samples may be similarly determined / constructed, for example, if the location [x] [y] of a sample in current block 904 to be predicted is projected to a negative y coordinate. The location [x] [y] of a sample may be projected to a negative y coordinate, for example, if negative horizontal prediction angles (p are used. The supplementary reference samples may be determined / constructed by projecting the reference samples in refl

[35] on the horizontal line of reference samples 902 to the vertical line of reference samples 902 using the negative horizontal prediction angle (p. An encoder may determine / predict samples of a current block being encoded (e.g., current block 904) for a plurality of intra prediction modes (e. g., using one or more of the functions described herein). For example, an encoder may determine / predict samples of a current block for each of 35 intra prediction modes in HEVC and / or 67 intra prediction modes in VVC and / or including extended intra prediction modes from WAIP for rectangular blocks. The encoder may determine, for each intra prediction mode applied, a corresponding prediction error for the current block based on a difference (e.g., sum of squared differences (SSD), sum of absolute differences (SAD), or sum of absolute transformed differences (SATD)) between the prediction samples, generated from reference samples 902 of a reference line (e. g., from a set of MRL), determined for the intra prediction mode and the original samples of the current block. The encoder may determine / select one of the intra prediction modes to encode the current block based on the determined prediction errors. For example, the encoder may determine / select one of the intra prediction modes that results in the smallest prediction error for the current block. In some examples, the encoder may determine / select the intra prediction mode and the associated reference line to encode the current block based on a rate-distortion measure (e. g., Lagrangian rate-distortion cost) determined using the prediction errors. The encoder may signal, in the bitstream to a decoder for decoding of the current block, an indication of the determined / selected intra prediction mode and an indication of the associated MRL index (which may indicate a reference line index). The encoder may also signal in the bitstream to the decoder a corresponding prediction error (e.g., residual) of the intra prediction mode. A decoder may determine / predict samples of a current block being decoded (e.g., current block 904) for an intra prediction mode. For example, a decoder may receive an indication of a reference line (e. g., a reference line index or an MRL index associated with the reference line index) and an intra prediction mode (e. g., an angular intra prediction mode) from an encoder for a current block. The decoder may retrieve a set of reference samples and perform intra prediction based on the MRL index and the intra prediction mode indicated by the encoder for the current block in a similar manner (e. g., as described above for the encoder). For example, the decoder may obtain the reference samples from a reference line indicated / identied by the decoded MRL index. In some examples, when MRL is not enabled / activated / selected, the reference line has reference line index 0 and is immediately adjacent to the current block. In these examples, no indication of MRL index is signaled. The decoder may add predicted values of the samples (e. g., determined based on the intra prediction mode) of the current block to a residual of the current block to reconstruct the current block. In some examples, a decoder need not receive an indication of an angular intra prediction mode from an encoder for a current block. Instead, the decoder may determine an intra prediction mode through other decoder-side means (eg., by applying template-based intra mode derivation (TIMD) tool / technique). While various examples herein correspond to intra prediction modes in HEVC and VVC, the methods, devices, and systems as described herein may be applied to / used for other intra prediction modes (eg., as used in other video coding standards / formats, such as VP8, VP9, AVl, etc.). Intra prediction may exploit correlations between spatially neighboring samples in the same picture of a video sequence to perform video compression. Inter prediction is another coding tool that may be used to perform video compression. Inter prediction may exploit correlations in the time domain between blocks of samples in different pictures of a video sequence. For example, an object may be seen across multiple pictures of a video sequence. The object may move (e.g., by some translation and / or afne motion) or remain stationary across the multiple pictures. A current block of samples in a current picture being encoded may have / be associated with a corresponding block of samples in a previously decoded picture. The corresponding block of samples may accurately predict the current block of samples. The corresponding block of samples may be displaced from the current block of samples, for example, due to movement of the object, represented in both blocks, across the respective pictures of the blocks. The previously decoded picture may be a reference picture. The corresponding block of samples in the reference picture may be a reference block for motion compensated prediction. An encoder may use a block matching technique to estimate the displacement (or motion) of the object and / or to determine the reference block in the reference picture. Similar to intra prediction, an encoder may determine a difference between a current block and a prediction for a current block. An encoder may determine a difference, for example, based on / after determining / generating a prediction for a current block (e. g., using inter prediction). The difference may be a prediction error (e.g., a residual). The encoder may store and / or send (e. g., signal), in / via a bitstream, the prediction error and / or other related prediction information. The prediction error and / or other related prediction information may be used for decoding and / or other forms of consumption. A decoder may decode the current block by predicting the samples of the current block (e. g., by using the related prediction information) and combining the predicted samples with the prediction error. FIG. 13A shows an example of inter prediction. The inter prediction may be performed for a current block 1300 in a current picture 1302 being encoded. An encoder (e. g., encoder 200 as shown in FIG. 2) may perform inter prediction to determine and / or generate a reference block 1304 in a reference picture 1306. Reference block 1304 may be used to predict the current block 1300. Reference pictures (e. g., reference picture 1306) may be prior decoded pictures available at the encoder and / or a decoder. Availability of a prior decoded picture may depend / be based on whether the prior decoded picture iS available in a decoded picture buffer, at the time, current block 1300 is being encoded and / or decoded. The encoder may search the one or more reference pictures 1306 for a block (e.g., a candidate reference block) that is Similar (or substantially similar) to current block 1300. The encoder may determine the best matching block from the blocks (e.g., candidate reference blocks) tested during the searching process. The best matching block may be a reference block 1304. The encoder may determine that reference block 1304 is the best matching reference block based on one or more cost criteria. The one or more cost criteria may comprise a rate-distortion criterion (eg., Lagrangian rate-distortion cost). The one or more cost criteria may be based on a difference (e. g., SSD, SAD, and / or SATD) between prediction samples of reference block 1304 and original samples of current block 1300. The encoder may search for reference block 1304 within a reference region (e. g., a search range 1308). The reference region (e.g., a search range 1308) may be positioned around a collocated block (or position) 1310, of current block 1300, in reference picture 1306. Collocated block 1310 may have a same position in the reference picture 1306 as the current block 1300 in the current picture 1302. The reference region (e.g., search range 1308) may at least partially extend outside of reference picture 1306. Constant boundary extension may be used, for example, if the reference region (e. g., search range 1308) extends outside of reference picture 1306. The constant boundary extension may be used such that values of the samples in a row or a column of reference picture 1306, immediately adjacent to a portion of the reference region (eg., search range 1308) extending outside of reference picture 1306, may be used for sample locations outside of reference picture 1306. A subset of potential positions, or all potential positions, within the reference region (e.g., search range 1308) may be searched for reference block 1304. The encoder may utilize one or more search implementations to determine and / or generate the reference block 1304. For example, the encoder may determine a set of candidate search positions based on motion information of neighboring blocks (e. g., a motion vector 1312) to the current block 1300. One or more reference pictures may be searched by the encoder during inter prediction to determine and / or generate the best matching reference block. The reference pictures searched by the encoder may be included in (e.g., added to) one or more reference picture lists. For example, in HEVC and VVC (and / or in one or more other communication protocols), two reference picture lists may be used (eg., a reference picture list 0 and a reference picture list 1). A reference picture list may include one or more pictures. The reference picture 1306 of reference block 1304 may be indicated by a reference index pointing into a reference picture list comprising reference picture 1306. FIG. 13B shows an example motion vector. A displacement between reference block 1304 and current block 1300 may be interpreted as an estimate of the motion between reference block 1304 and current block 1300 across their respective pictures. The displacement may be represented by a motion vector 1312. For example, motion vector 1312 may be indicated by a horizontal component (MVx) and a vertical component (MVy) relative to the position of current block 1300. A motion vector (e. g., motion vector 1312) may have fractional or integer resolution. A motion vector with fractional resolution may point between two samples in a reference picture to provide a better estimation of the motion of current block 1300. For example, a motion vector may have 1 / 2, 1 / 4, 1 / 8, 1 / 16, 1 / 32, or any other fractional sample resolution. Interpolation between the two samples at integer positions may be used to generate a reference block and its corresponding samples at fractional positions, for example, if a motion vector points to a non-integer sample value in the reference picture. The interpolation may be performed by a lter with two or more taps. The encoder may determine a difference (e.g., a corresponding sample-by-sample difference) between reference block 1304 and current block 1300. The encoder may determine the difference between reference block 1304 and current block 1300, for example, based on / after reference block 1304 is determined and / or generated, using inter prediction, for current block 1300. The difference may be a prediction error (e. g., a residual). The encoder may store and / or send (e.g., Signal), in / via a bitstream, the prediction error and / or related motion information. The prediction error and / or the related motion information may be used for decoding (e. g., decoding current block 1300) and / or other forms of consumption. The motion information may comprise the motion vector 1312 and a reference indicator / index. The reference indicator may indicate the reference picture 1306 in a reference picture list. In other examples, the motion information may comprise an indication of motion vector 1312 and / or an indication of the reference indicator / index. The reference indicator may indicate reference picture 1306 in the reference picture list comprising reference picture 1306. A decoder may decode current block 1300 by determining and / or generating the reference block 1304, which may correspond to / form (e. g., be considered as) a prediction of the current block 1300. The decoder may determine and / or generate the reference block 1304, for example, based on the related motion information. The decoder may decode current block 1300 based on combining the prediction (e.g., a reference block) with the prediction error (eg., a residual block). Inter prediction, as shown in FIG. 13A, may be performed using one reference picture 1306 as a source of a prediction for current block 1300. Inter prediction based on a prediction of a current block using a single picture may be referred to as uni-prediction. Inter prediction of a current block, using bi-prediction, may be based on two pictures (e.g., the source of prediction may be from the two pictures). Bi-prediction may be useful, for example, if a video sequence comprises fast motion, camera panning, zooming, and / or scene changes. Bi-prediction also may be useful to capture fade outs of one scene or fade outs from one scene to another, where two pictures may effectively be displayed simultaneously with different levels of intensity. One or both of uniprediction and biprediction may be available / used for performing inter prediction (e. g., at an encoder and / or at a decoder). Performing a specic type of inter prediction (e.g., uniprediction and / or biprediction) may depend on a slice type of current block. For example, for P slices, only uniprediction may be available / used for performing inter prediction. For B slices, either uni prediction or biprediction may be available / used for performing inter prediction. An encoder may determine and / or generate a reference block, for predicting a current block, from a reference picture list 0, for example, if the encoder is using uniprediction. An encoder may determine and / or generate a rst reference block, for predicting a current block, from a reference picture list 0 and determine and / or generate a second reference block, for predicting the current block, from a reference picture list 1, for example, if the encoder is using bi-prediction. FIG. 14 shows an example of bi-prediction. Two reference blocks 1402 and 1404 may be used to predict a current block 1400. Reference block 1402 may be in a reference picture of one of reference picture list 0 or reference picture list 1. Reference block 1404 may be in a reference picture of another one of reference picture list 0 or reference picture list 1. As shown in FIG. 14, reference block 1402 may be in a rst picture that precedes (e.g., in time) a current picture of current block 1400, and the reference block 1404 may be in a second picture that succeeds (e.g., in time) the current picture of current block 1400. The rst picture may precede the current picture in terms of a picture order count (POC). The second picture may succeed the current picture in terms of the POC. In other examples, the reference pictures may both precede or both succeed the current picture in terms of POC. A POC may be / indicate an order in which pictures are output (eg., from a decoded picture buffer). A POC may be / indicate an order in which pictures are generally intended to be displayed. Pictures that are output may not necessarily be displayed but may undergo different processing and / or consumption (eg., transcoding). The two reference blocks determined and / or generated using / for biprediction may correspond to (e. g., be comprised in) a same reference picture. The reference picture may be included in both the reference picture list 0 and the reference picture list 1, for example, if the two reference blocks correspond to the same reference picture. A congurable weight and / or offset value may be applied to one or more inter prediction reference blocks. An encoder may enable the use of weighted prediction using a ag in a picture parameter set (PPS). The encoder may send / signal the weight and / or offset parameters in a slice segment header for current block 1400. Different weight and / or offset parameters may be sent / signaled for luma and / or chroma components. The encoder may determine and / or generate the reference blocks 1402 and 1404 for the current block 1400 using inter prediction. The encoder may determine a difference between current block 1400 and each of reference blocks 1402 and 1404. The differences may be prediction errors or residuals. The encoder may store and / or send / signal, in / via a bitstream, the prediction errors and / or their respective related motion information. The prediction errors and their respective related motion information may be used for decoding and / or other forms of consumption. The motion information for reference block 1402 may comprise a motion vector 1406 and / or a reference indicator / index. The reference indicator may indicate a reference picture, of the reference block 1402, in a reference picture list. In some examples, the motion information for reference block 1402 may comprise an indication of motion vector 1406 and / or an indication of the reference index. The reference index may indicate the reference picture, of reference block 1402, in the reference picture list. The motion information for reference block 1404 may comprise a motion vector 1408 and / or a reference index / indicator. The reference indicator may indicate a reference picture, of the reference block 1404, in a reference picture list. The motion information for reference block 1404 may comprise an indication of motion vector 1408 and / or an indication of the reference index. The reference index may indicate the reference picture, of the reference block 1404, in the reference picture list. A decoder may decode current block 1400 by determining and / or generating the reference blocks 1402 and 1404. The decoder may determine and / or generate the reference blocks 1402 and 1404, for example, based on the respective related motion information for the reference blocks 1402 and 1404. The reference blocks 1402 and 1404 may correspond to / form (e.g., be considered as) the prediction (e.g., used to generate a prediction block) of the current block 1400. The decoder may decode the current block 1400 based on combining the prediction with the prediction errors. Motion information may be predictively coded, for example, before being stored and / or sent / Signaled in / via a bit stream (e.g., in HEVC, VVC, and / or other video coding standards / formats / protocols). The motion information for a current block may be predictively coded based on motion information of one or more blocks neighboring the current block. The motion information of the neighboring block(s) may often correlate with the motion information of the current block because the motion of an object represented in the current block is often the same as (or similar to) the motion of objects in the neighboring block(s). Motion information prediction techniques (such as those in HEVC and VVC) may comprise advanced motion vector prediction (AMVP) and / or inter prediction block merging (e. g., merge mode). An encoder (e. g., encoder 200 as Shown in FIG. 2), may code a motion vector. The encoder may code the motion vector (e.g., using AMVP) as a difference between a motion vector of a current block being coded and a motion vector predictor (MVP). An encoder may determine / select the MVP from a list of candidate MVPS. The candidate MVPs may be / correspond to previously decoded motion vectors of neighboring blocks in the current picture of the current block, and / or blocks at or near the collocated position of the current block in other reference pictures. The encoder and / or a decoder may reciprocally generate and / or determine the list of candidate MVPS. The encoder may determine / select an MVP from the list of candidate MVPs. Then, the encoder may send / signal, in / via a bitstream, an indication of the selected MVP and / or a motion vector difference (MVD). The encoder may indicate the selected MVP in the bitstream using an index / indicator. The index may indicate the selected MVP in the list of candidate MVPS. The MVD may be determined / calculated based on a difference between the motion vector of the current block and the selected MVP. For example, for a motion vector (e. g., comprising a horizontal component (MVx) and a vertical component (MVy)) that indicates a position relative to a position of the current block being coded, the MVD may be represented by two components I'ul'IFJDJr and MVD}, IWI-TDr and MVD}, may be determined / calculated as: MVD;r = mvr MVP}, (15) mm,. = MV}. MVP}, (16) MVDx and MVDy may respectively represent horizontal and vertical components of the MVD. MVPx and MVPy may respectively represent horizontal and vertical components of the MVP. A decoder (e. g., decoder 300 as shown in FIG. 3) may decode the motion vector by adding the MVD to the MVP indicated in / via the bitstream. The decoder may decode the current block by determining and / or generating the reference block. The decoder may determine and / or generate the reference block, for example, based on the decoded motion vector. The reference block may correspond to / form (e.g., be considered as) the prediction of the current block (e. g., a prediction block). The decoder may decode the current block by combining the prediction with the prediction error. The list of candidate MVPS (e.g., in HEVC, VVC, and / or one or more other communication protocols), for AMVP, may comprise two or more candidates (e.g., candidates A and B). Candidates A and B may comprise: up to two (or any other quantity of) spatial candidate MVPS determined / derived from ve (or any other quantity of) spatial neighboring blocks of a current block being coded; one (or any other quantity of) temporal candidate MVP determined / derived from two (or any other quantity of) temporal, colocated blocks (e. g., if both of the two spatial candidate MVPS are not available or are identical); and / or zero motion vector candidate MVPS (e. g., if one or both of the spatial candidate MVPS or temporal candidate MVPs are not available). Other quantities of spatial candidate MVPs, spatial neighboring blocks, temporal candidate MVPs, and / or temporal, co-located blocks may be used for the list of candidate MVPs. FIG. ISA shows example spatial candidate neighboring blocks for a current block. For example, ve (or any other quantity of) spatial candidate neighboring blocks may be located relative to a current block 1500 being encoded. The ve spatial candidate neighboring blocks may be A0, AI, B0, BI, and B2. FIG. ISB shows temporal, colocated blocks for the current block. For example, two (or any other quantity of) temporal, co-located blocks may be located relative to current block 1500 being coded. The two temporal, co-located blocks may be C0 and C1. The two temporal, co-located blocks may be in one or more reference pictures that may be different from the current picture of current block 1500. An encoder (eg., encoder 200 as shown in FIG. 2) may code a motion vector using inter prediction block merging (eg., a merge mode). For example, the encoder (eg., using merge mode) may reuse the same motion information of a neighboring block (eg., one of neighboring blocks A0, A1 , B0, B], and B2) for inter prediction of a current block. For example, the encoder (e. g., using merge mode) may reuse the same motion information of a temporal, co-located block (e. g., one of temporal, colocated blocks C0 and C1) for inter prediction of a current block. An MVD need not be sent (e.g., indicated, signaled) for the current block because the same motion information as that of a neighboring block or a temporal, colocated block may be used for the current block (e.g., at the encoder and / or a decoder). A signaling overhead for sending / signaling the motion information of the current block may be reduced because the MVD need not be indicated for the current block. The encoder and / or the decoder may reciprocally generate a candidate list of motion information from neighboring blocks or temporal, co located blocks of the current block (e. g., in a manner similar to AMVP). The encoder may determine to use (e. g., inherit) motion information, of one neighboring block or one temporal, colocated block in the candidate list, for predicting motion information of the current block being coded. The encoder may signal / send, in / via a bitstream, an indication of the determined motion information from the candidate list. For example, the encoder may signal / send an indicator / index. The index may indicate the determined motion information in the list of candidate motion information. The encoder may signal / send the index to indicate the determined motion information. A list of candidate motion information for merge mode (e.g., in HEVC, VVC, or any other coding formats / standards / protocols) may comprise: up to four (or any other quantity of) spatial merge candidates derived / determined from ve (or any other quantity of) spatial neighboring blocks (e. g., as shown in FIG. 15A); one (or any other quantity of) temporal merge candidate derived from two (or any other quantity of) temporal, colocated blocks (e.g., as shown in FIG. 15B); and / or additional merge candidates comprising bipredictive candidates and zero motion vector candidates. In some examples, the spatial neighboring blocks and the temporal, co-located blocks used for merge mode may be the same as the spatial neighboring blocks and the temporal, colocated blocks used for AMVP. Inter prediction may be performed in other ways and variants than those described herein. For example, motion information prediction techniques other than AMVP and merge mode may be used. While various examples herein correspond to inter prediction modes, such as used in HEVC and VVC, the methods, devices, and systems as described herein may be applied to / used for other inter prediction modes (e.g., as used for other video coding standards / formats such as VP8, VP9, AVI, etc.). History- based motion vector prediction (HMVP), combined intra / inter prediction mode (CIIP), and / or merge mode with motion vector difference (MMVD) (e.g., as described in VVC) may be performed / used and are within the scope of the present disclosure. A block matching operation (or technique) may be applied / used (e.g., in inter prediction) to determine a reference block in a different picture than that of a current block being coded (e. g., encoded and / or decoded). A block matching operation also may be applied / used to determine a reference block in a same picture as that of a current block being coded. The reference block, in a same picture as that of the current block, as determined using block matching may often not accurately predict the current block (e. g., for camera captured videos). Prediction accuracy for screen content videos may not be similarly impacted, for example, if a reference block in the same picture as that of the current block is used for encoding. Screen content videos may comprise, for example, computer generated text, graphics, animation, etc. Screen content videos may comprise (e. g., may often comprise) repeated patterns (e. g., repeated patterns of text and / or graphics) within the same picture. Using a reference block (e. g., as determined using block matching), in a same picture as that of a current block being encoded, may provide efcient compression for screen content videos. A prediction technique may be used (e. g., in HEVC, VVC, and / or any other coding standards / formats / protocols) to exploit correlation between blocks of samples within a same picture (e. g., of screen content videos). The prediction technique may be intra block copy (IBC) or current picture referencing (CPR). An encoder may apply / use a block matching technique (e. g., similar to inter prediction) to determine a displacement vector (e. g., a block vector (BV)). The BV may indicate a relative position of a reference block (e.g., in accordance with intra block compensated prediction), that best matches the current block, from a position of the current block. For example, the relative position of the reference block may be a relative position of a top-left corner (or any other point / sample) of the reference block. The BV may indicate a relative displacement from the current block to the reference block that best matches the current block. The encoder may determine the best matching reference block from blocks tested during a searching process (e. g., in a manner similar to that used for inter prediction). The encoder may determine that a reference block is the best matching reference block based on one or more cost criteria. The one or more cost criteria may comprise a rate-distortion criterion (eg., Lagrangian rate- distortion cost). The one or more cost criteria may be based on, for example, one or more differences (e. g., an SSD, an SAD, an SATD, and / or a difference determined based on a haSh function) between the prediction samples of the reference block and the original samples of the current block. A reference block may correspond to / comprise prior decoded blocks of samples (e.g., reconstructed samples) of the current picture. The reference block may comprise decoded blocks of samples of the current picture prior to being processed by inloop ltering operations (e. g., deblocking and / or SAO ltering). FIG. 16A shows an example of IBC (e.g., an IBC mode). The example shown in FIG. 16A may correspond to screen content. The rectangular portions / sections with arrows beginning at their boundaries may be the current blocks being encoded. The rectangular portions / sections that the arrows point to may be the reference blocks for predicting the respective current blocks. A reference block may be determined and / or generated, for a current block, using IBC. The encoder may determine a difference (eg., a corresponding sample-by-sample difference) between the reference block and the current block. The difference may be a prediction error or residual. The encoder may store and / or send / signal, in / via a bitstream the prediction error and / or related prediction information. The prediction error and / or the related prediction information may be used for decoding and / or other forms of consumption. The prediction information may comprise a BV. The prediction information may comprise an indication of the BV. A decoder (e.g., decoder 300 as shown in FIG. 3), may decode the current block by determining and / or generating the reference block. The decoder may determine and / or generate the current block, for example, based on the prediction information (e. g., the BV). The reference block may correspond to / form (e.g., be considered as) the prediction (e. g., a prediction block) of the current block. The decoder may decode the current block by combining the prediction (e. g., prediction block) with the prediction error (e. g., residual or residual block). A BV may be predictively coded (e. g., in HEVC, VVC, and / or any other coding standards / formats / protocols) before being stored and / or sent / signaled in / via a bitstream. For example, the BV for a current block may be predictively coded based on a BV of one or more blocks neighboring the current block. For example, an encoder may predictively code a BV using the merge mode (e. g., in a manner similar to as described herein for inter prediction), AMVP (e. g., as described herein for inter prediction), or a technique similar to AMVP. The technique similar to AMVP may be BV prediction and difference coding (or AMVP for IBC). An encoder (e. g., encoder 200 as Shown in FIG. 2) performing BV prediction and coding may code a BV as a difference between the BV of a current block being coded and a block vector predictor (BVP). An encoder may select / determine the BVP from a list of candidate BVPs. The candidate BVPS may comprise / correspond to previously decoded BVs of neighboring blocks in the current picture of the current block. The encoder and / or a decoder may reciprocally generate or determine the list of candidate BVPs. The encoder may send / signal, in / via a bitstream, an indication of the selected BVP and a block vector difference (BVD). The encoder may indicate the selected BVP in the bitstream using an index / indicator. The index may indicate (e. g., point to) the selected BVP in the list of candidate BVPS. The BVD may be determined / calculated based on a difference between a BV of the current block and the selected BVP. For example, for a BV (e. g., represented by a horizontal component (BVx) and a vertical component (BVy)) that indicates a position relative to a position of the current block being coded, the BVD may be represented by two components BVDI and BVDy. BVDI and BVD}, may be determined / calculated as: BVD,r = Bar,r Eva (17) BVD}, = BV}, BVP}. (18) BVDx and BVDy may respectively represent horizontal and vertical components of the BVD. BVPx and BVPy may respectively represent horizontal and vertical components of the BVP. A decoder (e. g., decoder 300 as shown in F IG. 3), may decode the BV by adding the BVD to the BVP indicated in / via the bitstream. The decoder may decode the current block by determining and / or