EP4699308A1 - Extended intra prediction angles - Google Patents

Abstract

A reconstructed block data is generated by decoding, from an encoded bitstream, a current block of a current frame. Decoding the current block includes accessing from the encoded bitstream an angle mode value and an angle delta value, obtaining an angle refinement value, obtaining as an intra prediction angle value, a combination of the angle mode value, the angle delta value, and the angle refinement value, obtaining an intra prediction block by intra prediction in accordance with the intra prediction angle value, obtaining the reconstructed block data using the intra prediction block, including the reconstructed block data in reconstructed frame data, and outputting the reconstructed frame data.

Description

EXTENDED INTRA PREDICTION ANGLES

CROSS-REFERENCE TO RELATED APPLICATION^ )

[0001] This application claims priority to and the benefit of U.S. Provisional Application Patent Serial No. 63/468,033, filed May 22, 2023, the entire disclosure of which is hereby incorporated by reference.

BACKGROUND

[0002] Digital images and video can be used, for example, on the internet, for remote business meetings via video conferencing, high-definition video entertainment, video advertisements, or sharing of user-generated content. Due to the large amount of data involved in transferring and processing image and video data, high-performance compression may be advantageous for transmission and storage. Accordingly, it would be advantageous to provide high-resolution image and video transmitted over communications channels having limited bandwidth.

SUMMARY

[0003] This application relates to encoding and decoding of image data, video stream data, or both for transmission, storage, or both. Disclosed herein are aspects of systems, methods, and apparatuses for encoding and decoding using extended intra prediction angles (intra prediction with angle refinement).

[0004] Variations in these and other aspects will be described in additional detail hereafter. [0005] An aspect is a method for decoding using intra prediction with angle refinement.

Decoding using intra prediction with angle refinement includes generating reconstructed block data by decoding, from an encoded bitstream, a current block of a current frame. Decoding the current block includes accessing, from the encoded bitstream, an angle mode value, accessing, from the encoded bitstream, an angle delta value, obtaining an angle refinement value, obtaining, as an intra prediction angle value, a combination of the angle mode value, the angle delta value, and the angle refinement value, obtaining an intra prediction block by intra prediction in accordance with the intra prediction angle value, and obtaining the reconstructed block data using the intra prediction block. Decoding using intra prediction with angle refinement includes including the reconstructed block data in a reconstructed frame and outputting the reconstructed frame.

[0006] An aspect is an apparatus for decoding using intra prediction with angle refinement. The apparatus includes a memory and a processor configured to execute instructions stored on the memory to perform decoding using intra prediction with angle refinement. The processor may execute the instructions to generate reconstructed block data, wherein, to generate the reconstructed block data, the processor is configured to execute the instructions to decode, from an encoded bitstream, a current block of a current frame. To decode the current block the processor is configured to execute the instructions to access, from the encoded bitstream, an angle mode value, access, from the encoded bitstream, an angle delta value, obtain an angle refinement value, obtain, as an intra prediction angle value, a combination of the angle mode value, the angle delta value, and the angle refinement value, obtain an intra prediction block by intra prediction in accordance with the intra prediction angle value, and obtain the reconstructed block data in accordance with the intra prediction block. The process may execute the instructions to include the reconstructed block data in reconstructed frame data and output the reconstructed frame data.

[0007] An aspect is a non-transitory computer-readable storage medium having stored thereon an encoded bitstream comprising encoded block data including an encoded angle mode value, an encoded angle delta value, and an encoded syntax element representing a multiple reference line index value and indicating an angle refinement value.

[0008] An aspect is a method for encoding using intra prediction with angle refinement. Encoding using intra prediction with angle refinement includes generating encoded block data by encoding a current block of a current frame. Encoding the current block includes obtaining an intra prediction angle value for encoding the current block, wherein obtaining the intra prediction angle value includes obtaining a multiple reference line index value, obtaining an angle mode value, an angle delta value, and an angle refinement value, wherein the intra prediction angle value is a sum of the angle mode value, the angle delta value, and the angle refinement value, obtain intra prediction block data in accordance with the intra prediction angle value, including the angle mode value in the encoded block data, including the angle delta value in the encoded block data, and including the multiple reference line index value in the encoded block data. Encoding using intra prediction with angle refinement includes including the encoded block data in an encoded bitstream and outputting the encoded bitstream.

[0009] An aspect is an apparatus for encoding using intra prediction with angle refinement. The apparatus includes a memory and a processor configured to execute instructions stored on the memory to perform encoding using intra prediction with angle refinement. The processor may execute the instructions to generate encoded block data. To generate the encoded block data, the processor is configured to execute the instruction to encode a current block of a current frame, to encode the current block, the processor is configured to execute the instructions to obtain an intra prediction angle value to encode the current block, wherein to obtain the intra prediction angle value the processor is configured to execute the instruction to obtain a multiple reference line index value, obtain an angle mode value, an angle delta value, and an angle refinement value, wherein the intra prediction angle value is a sum of the angle mode value, the angle delta value, and the angle refinement value, intra prediction encode the current block in accordance with the intra prediction angle value, include the angle mode value in the encoded block data, include the angle delta value in the encoded block data, and include the multiple reference line index value in the encoded block data. The processor may execute the instructions to include the encoded block data in an encoded bitstream and output the encoded bitstream.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The description herein makes reference to the accompanying drawings wherein like reference numerals refer to like parts throughout the several views unless otherwise noted or otherwise clear from context.

[0011] FIG. 1 is a diagram of a computing device in accordance with implementations of this disclosure.

[0012] FIG. 2 is a diagram of a computing and communications system in accordance with implementations of this disclosure.

[0013] FIG. 3 is a diagram of a video stream for use in encoding and decoding in accordance with implementations of this disclosure.

[0014] FIG. 4 is a block diagram of an encoder in accordance with implementations of this disclosure.

[0015] FIG. 5 is a block diagram of a decoder in accordance with implementations of this disclosure.

[0016] FIG. 6 is a block diagram of a representation of a portion of a frame in accordance with implementations of this disclosure.

[0017] FIG. 7 is a flow diagram of an example of decoding using intra prediction with angle refinement. [0018] FIG. 8 is a flow diagram of an example of encoding using intra prediction with angle refinement.

DETAILED DESCRIPTION

[0019] Image and video compression schemes may include breaking an image, or frame, into smaller portions, such as blocks, and generating an output bitstream using techniques to minimize the bandwidth utilization of the information included for each block in the output. In some implementations, the information included for each block in the output may be limited by reducing spatial redundancy, reducing temporal redundancy, or a combination thereof. For example, temporal or spatial redundancies may be reduced by predicting a frame, or a portion thereof, based on information available to both the encoder and decoder, and including information representing a difference, or residual, between the predicted frame and the original frame in the encoded bitstream. The residual information may be further compressed by transforming the residual information into transform coefficients (e.g., energy compaction), quantizing the transform coefficients, and entropy coding the quantized transform coefficients. Other coding information, such as motion information, may be included in the encoded bitstream, which may include transmitting differential information based on predictions of the encoding information, which may be entropy coded to further reduce the corresponding bandwidth utilization. An encoded bitstream can be decoded to reconstruct the blocks and the source images from the limited information. In some implementations, the accuracy, efficiency, or both, of coding a block using either interprediction or intra-prediction may be limited.

[0020] Some block-based hybrid video coding techniques, or codecs, reduce spatial redundancy by performing directional intra prediction in accordance with a defined set of available prediction angles. The defined set of available prediction angles may include limited number, count, or cardinality, of available angles, such as fifty- six prediction angles. Using a limited number, count, or cardinality, of available angles, such as fifty-six prediction angles, may generate non-optimal predictions, which may cause relatively high residual values that utilize a relatively large number of bits to code, resulting in relatively low coding gain. Increasing the number of prediction angles may improve prediction accuracy. Expressly signaling more accurate prediction angles may result in relatively high mode signaling cost, which may negate the benefit of improved prediction accuracy.

[0021] The encoding and decoding using intra prediction with angle refinement described herein improves on video coding techniques, or codecs, with fewer available intra prediction angles and video coding techniques, or codecs, that less efficiently signal intra prediction angles by having up to one hundred sixty eight available angles, to improve prediction accuracy, and by signaling an angle refinement, or increment, value with another syntax element, such as a multiple reference line index value, to reduce signaling overhead.

[0022] FIG. 1 is a diagram of a computing device 100 in accordance with implementations of this disclosure. The computing device 100 shown includes a memory 110, a processor 120, a user interface (UI) 130, an electronic communication unit 140, a sensor 150, a power source 160, and a bus 170. As used herein, the term “computing device” includes any unit, or a combination of units, capable of performing any method, or any portion or portions thereof, disclosed herein.

[0023] The computing device 100 may be a stationary computing device, such as a personal computer (PC), a server, a workstation, a minicomputer, or a mainframe computer; or a mobile computing device, such as a mobile telephone, a personal digital assistant (PDA), a laptop, or a tablet PC. Although shown as a single unit, any one element or elements of the computing device 100 can be integrated into any number of separate physical units. For example, the user interface 130 and processor 120 can be integrated in a first physical unit and the memory 110 can be integrated in a second physical unit.

[0024] The memory 110 can include any non-transitory computer-usable or computer- readable medium, such as any tangible device that can, for example, contain, store, communicate, or transport data 112, instructions 114, an operating system 116, or any information associated therewith, for use by or in connection with other components of the computing device 100. The non-transitory computer-usable or computer-readable medium can be, for example, a solid-state drive, a memory card, removable media, a read-only memory (ROM), a random-access memory (RAM), any type of disk including a hard disk, a floppy disk, an optical disk, a magnetic or optical card, an application- specific integrated circuits (ASICs), or any type of non-transitory media suitable for storing electronic information, or any combination thereof.

[0025] Although shown a single unit, the memory 110 may include multiple physical units, such as one or more primary memory units, such as random-access memory units, one or more secondary data storage units, such as disks, or a combination thereof. For example, the data 112, or a portion thereof, the instructions 114, or a portion thereof, or both, may be stored in a secondary storage unit and may be loaded or otherwise transferred to a primary storage unit in conjunction with processing the respective data 112, executing the respective instructions 114, or both. In some implementations, the memory 110, or a portion thereof, may be removable memory.

[0026] The data 112 can include information, such as input audio data, encoded audio data, decoded audio data, or the like. The instructions 114 can include directions, such as code, for performing any method, or any portion or portions thereof, disclosed herein. The instructions 114 can be realized in hardware, software, or any combination thereof. For example, the instructions 114 may be implemented as information stored in the memory 110, such as a computer program, which may be executed by the processor 120 to perform any of the respective methods, algorithms, aspects, or combinations thereof, as described herein. [0027] Although shown as included in the memory 110, in some implementations, the instructions 114, or a portion thereof, may be implemented as a special purpose processor, or circuitry, that can include specialized hardware for carrying out any of the methods, algorithms, aspects, or combinations thereof, as described herein. Portions of the instructions 114 can be distributed across multiple processors on the same machine or different machines or across a network such as a local area network, a wide area network, the Internet, or a combination thereof.

[0028] The processor 120 can include any device or system capable of manipulating or processing a digital signal or other electronic information now-existing or hereafter developed, including optical processors, quantum processors, molecular processors, or a combination thereof. For example, the processor 120 can include a special purpose processor, a central processing unit (CPU), a digital signal processor (DSP), a plurality of microprocessors, one or more microprocessor in association with a DSP core, a controller, a microcontroller, an Application Specific Integrated Circuit (ASIC), a Field Programmable Gate Array (FPGA), a programmable logic array, programmable logic controller, microcode, firmware, any type of integrated circuit (IC), a state machine, or any combination thereof. As used herein, the term “processor” includes a single processor or multiple processors.

[0029] The user interface 130 can include any unit capable of interfacing with a user, such as a virtual or physical keypad, a touchpad, a display, a touch display, a speaker, a microphone, a video camera, a sensor, or any combination thereof. For example, the user interface 130 may be an audio-visual display device, and the computing device 100 may present audio, such as decoded audio, using the user interface 130 audio-visual display device, such as in conjunction with displaying video, such as decoded video. Although shown as a single unit, the user interface 130 may include one or more physical units. For example, the user interface 130 may include an audio interface for performing audio communication with a user, and a touch display for performing visual and touch-based communication with the user.

[0030] The electronic communication unit 140 can transmit, receive, or transmit and receive signals via a wired or wireless electronic communication medium 180, such as a radio frequency (RF) communication medium, an ultraviolet (UV) communication medium, a visible light communication medium, a fiber optic communication medium, a wireline communication medium, or a combination thereof. For example, as shown, the electronic communication unit 140 is operatively connected to an electronic communication interface 142, such as an antenna, configured to communicate via wireless signals.

[0031] Although the electronic communication interface 142 is shown as a wireless antenna in FIG. 1, the electronic communication interface 142 can be a wireless antenna, as shown, a wired communication port, such as an Ethernet port, an infrared port, a serial port, or any other wired or wireless unit capable of interfacing with a wired or wireless electronic communication medium 180. Although FIG. 1 shows a single electronic communication unit 140 and a single electronic communication interface 142, any number of electronic communication units and any number of electronic communication interfaces can be used. [0032] The sensor 150 may include, for example, an audio-sensing device, a visible lightsensing device, a motion sensing device, or a combination thereof. For example, lOOthe sensor 150 may include a sound-sensing device, such as a microphone, or any other soundsensing device now existing or hereafter developed that can sense sounds in the proximity of the computing device 100, such as speech or other utterances, made by a user operating the computing device 100. In another example, the sensor 150 may include a camera, or any other image-sensing device now existing or hereafter developed that can sense an image such as the image of a user operating the computing device. Although a single sensor 150 is shown, the computing device 100 may include a number of sensors 150. For example, the computing device 100 may include a first camera oriented with a field of view directed toward a user of the computing device 100 and a second camera oriented with a field of view directed away from the user of the computing device 100.

[0033] The power source 160 can be any suitable device for powering the computing device 100. For example, the power source 160 can include a wired external power source interface; one or more dry cell batteries, such as nickel-cadmium (NiCd), nickel-zinc (NiZn), nickel metal hydride (NiMH), lithium-ion (Li-ion); solar cells; fuel cells; or any other device capable of powering the computing device 100. Although a single power source 160 is shown in FIG. 1, the computing device 100 may include multiple power sources 160, such as a battery and a wired external power source interface. [0034] Although shown as separate units, the electronic communication unit 140, the electronic communication interface 142, the user interface 130, the power source 160, or portions thereof, may be configured as a combined unit. For example, the electronic communication unit 140, the electronic communication interface 142, the user interface 130, and the power source 160 may be implemented as a communications port capable of interfacing with an external display device, providing communications, power, or both.

[0035] One or more of the memory 110, the processor 120, the user interface 130, the electronic communication unit 140, the sensor 150, or the power source 160, may be operatively coupled via a bus 170. Although a single bus 170 is shown in FIG. 1, a computing device 100 may include multiple buses. For example, the memory 110, the processor 120, the user interface 130, the electronic communication unit 140, the sensor 150, and the bus 170 may receive power from the power source 160 via the bus 170. In another example, the memory 110, the processor 120, the user interface 130, the electronic communication unit 140, the sensor 150, the power source 160, or a combination thereof, may communicate data, such as by sending and receiving electronic signals, via the bus 170.

[0036] Although not shown separately in FIG. 1, one or more of the processor 120, the user interface 130, the electronic communication unit 140, the sensor 150, or the power source 160 may include internal memory, such as an internal buffer or register. For example, the processor 120 may include internal memory (not shown) and may read data 112 from the memory 110 into the internal memory (not shown) for processing.

[0037] Although shown as separate elements, the memory 110, the processor 120, the user interface 130, the electronic communication unit 140, the sensor 150, the power source 160, and the bus 170, or any combination thereof can be integrated in one or more electronic units, circuits, or chips.

[0038] FIG. 2 is a diagram of a computing and communications system 200 in accordance with implementations of this disclosure. The computing and communications system 200 shown includes computing and communication devices 100A, 100B, 100C, access points 210A, 210B, and a network 220. For example, the computing and communication system 200 can be a multiple access system that provides communication, such as voice, audio, data, video, messaging, broadcast, or a combination thereof, to one or more wired or wireless communicating devices, such as the computing and communication devices 100A, 100B, 100C. Although, for simplicity, FIG. 2 shows three computing and communication devices 100A, 100B, 100C, two access points 210A, 210B, and one network 220, any number of computing and communication devices, access points, and networks can be used. [0039] A computing and communication device 100A, 100B, 100C can be, for example, a computing device, such as the computing device 100 shown in FIG. 1. For example, the computing and communication devices 100A, 100B may be user devices, such as a mobile computing device, a laptop, a thin client, or a smartphone, and the computing and communication device 100C may be a server, such as a mainframe or a cluster. Although the computing and communication device 100A and the computing and communication device 100B are described as user devices, and the computing and communication device 100C is described as a server, any computing and communication device may perform some or all of the functions of a server, some, or all, of the functions of a user device, or some or all of the functions of a server and a user device. For example, the server computing and communication device 100C may receive, encode, process, store, transmit, or a combination thereof audio data and one or both of the computing and communication device 100A and the computing and communication device 100B may receive, decode, process, store, present, or a combination thereof the audio data.

[0040] Each computing and communication device 100A, 100B, 100C, which may include a user equipment (UE), a mobile station, a fixed or mobile subscriber unit, a cellular telephone, a personal computer, a tablet computer, a server, consumer electronics, or any similar device, can be configured to perform wired or wireless communication, such as via the network 220. For example, the computing and communication devices 100A, 100B, 100C can be configured to transmit or receive wired or wireless communication signals. Although each computing and communication device 100A, 100B, 100C is shown as a single unit, a computing and communication device can include any number of interconnected elements. [0041] Each access point 210A, 210B can be any type of device configured to communicate with a computing and communication device 100A, 100B, 100C, a network 220, or both via wired or wireless communication links 180A, 180B, 180C. For example, an access point 210A, 210B can include a base station, a base transceiver station (BTS), a Node- B, an enhanced Node-B (eNode-B), a Home Node-B (HNode-B), a wireless router, a wired router, a hub, a relay, a switch, or any similar wired or wireless device. Although each access point 210A, 210B is shown as a single unit, an access point can include any number of interconnected elements.

[0042] The network 220 can be any type of network configured to provide services, such as voice, data, applications, voice over internet protocol (VoIP), or any other communications protocol or combination of communications protocols, over a wired or wireless communication link. For example, the network 220 can be a local area network (LAN), wide area network (WAN), virtual private network (VPN), a mobile or cellular telephone network, the Internet, or any other means of electronic communication. The network can use a communication protocol, such as the transmission control protocol (TCP), the user datagram protocol (UDP), the internet protocol (IP), the real-time transport protocol (RTP) the HyperText Transport Protocol (HTTP), or a combination thereof.

[0043] The computing and communication devices 100A, 100B, 100C can communicate with each other via the network 220 using one or more a wired or wireless communication links, or via a combination of wired and wireless communication links. For example, as shown the computing and communication devices 100A, 100B can communicate via wireless communication links 180A, 180B, and computing and communication device 100C can communicate via a wired communication link 180C. Any of the computing and communication devices 100A, 100B, 100C may communicate using any wired or wireless communication link, or links. For example, a first computing and communication device 100A can communicate via a first access point 210A using a first type of communication link, a second computing and communication device 100B can communicate via a second access point 21 OB using a second type of communication link, and a third computing and communication device 100C can communicate via a third access point (not shown) using a third type of communication link. Similarly, the access points 210A, 210B can communicate with the network 220 via one or more types of wired or wireless communication links 230A, 230B. Although FIG. 2 shows the computing and communication devices 100A, 100B, 100C in communication via the network 220, the computing and communication devices 100A, 100B, 100C can communicate with each other via any number of communication links, such as a direct wired or wireless communication link.

[0044] In some implementations, communications between one or more of the computing and communication device 100A, 100B, 100C may omit communicating via the network 220 and may include transferring data via another medium (not shown), such as a data storage device. For example, the server computing and communication device 100C may store audio data, such as encoded audio data, in a data storage device, such as a portable data storage unit, and one or both of the computing and communication device 100A or the computing and communication device 100B may access, read, or retrieve the stored audio data from the data storage unit, such as by physically disconnecting the data storage device from the server computing and communication device 100C and physically connecting the data storage device to the computing and communication device 100A or the computing and communication device 100B. [0045] Other implementations of the computing and communications system 200 are possible. For example, in an implementation, the network 220 can be an ad-hoc network and can omit one or more of the access points 210A, 210B. The computing and communications system 200 may include devices, units, or elements not shown in FIG. 2. For example, the computing and communications system 200 may include many more communicating devices, networks, and access points.

[0046] FIG. 3 is a diagram of a video stream 300 for use in encoding and decoding in accordance with implementations of this disclosure. A video stream 300, such as a video stream captured by a video camera or a video stream generated by a computing device, may include a video sequence 310. The video sequence 310 may include a sequence of adjacent frames 320. Although three adjacent frames 320 are shown, the video sequence 310 can include any number of adjacent frames 320.

[0047] Each frame 330 from the adjacent frames 320 may represent a single image from the video stream. Although not shown in FIG. 3, a frame 330 may include one or more segments, tiles, or planes, which may be coded, or otherwise processed, independently, such as in parallel. A frame 330 may include one or more tiles 340. Each of the tiles 340 may be a rectangular region of the frame that can be coded independently. Each of the tiles 340 may include respective blocks 350. Although not shown in FIG. 3, a block can include pixels. For example, a block can include a 16x16 group of pixels, an 8x8 group of pixels, an 8x16 group of pixels, or any other group of pixels. Unless otherwise indicated herein, the term ‘block’ can include a superblock, a macroblock, a segment, a slice, or any other portion of a frame. A frame, a block, a pixel, or a combination thereof can include display information, such as luminance information, chrominance information, or any other information that can be used to store, modify, communicate, or display the video stream or a portion thereof.

[0048] FIG. 4 is a block diagram of an encoder 400 in accordance with implementations of this disclosure. Encoder 400 can be implemented in a device, such as the computing device 100 shown in FIG. 1 or the computing and communication devices 100A, 100B, 100C shown in FIG. 2, as, for example, a computer software program stored in a data storage unit, such as the memory 110 shown in FIG. 1. The computer software program can include machine instructions that may be executed by a processor, such as the processor 120 shown in FIG. 1, and may cause the device to encode video data as described herein. The encoder 400 can be implemented as specialized hardware included, for example, in computing device 100.

[0049] The encoder 400 can encode an input video stream 402, such as the video stream 300 shown in FIG. 3, to generate an encoded (compressed) bitstream 404. In some implementations, the encoder 400 may include a forward path for generating the compressed bitstream 404. The forward path may include an intra/inter prediction unit 410, a transform unit 420, a quantization unit 430, an entropy encoding unit 440, or any combination thereof. In some implementations, the encoder 400 may include a reconstruction path (indicated by the broken connection lines) to reconstruct a frame for encoding of further blocks. The reconstruction path may include a dequantization unit 450, an inverse transform unit 460, a reconstruction unit 470, a filtering unit 480, or any combination thereof. Other structural variations of the encoder 400 can be used to encode the video stream 402.

[0050] For encoding the video stream 402, each frame within the video stream 402 can be processed in units of blocks. Thus, a current block may be identified from the blocks in a frame, and the current block may be encoded.

[0051] At the intra/inter prediction unit 410, the current block can be encoded using either intra-frame prediction, which may be within a single frame, or inter-frame prediction, which may be from frame to frame. Intra-prediction may include generating a prediction block from samples in the current frame that have been previously encoded and reconstructed. Interprediction may include generating a prediction block from samples in one or more previously constructed reference frames. Generating a prediction block for a current block in a current frame may include performing motion estimation to generate a motion vector indicating an appropriate reference portion of the reference frame.

[0052] The intra/inter prediction unit 410 may subtract the prediction block from the current block (raw block) to produce a residual block. The transform unit 420 may perform a block-based transform, which may include transforming the residual block into transform coefficients in, for example, the frequency domain. Examples of block-based transforms include the Karhunen-Loeve Transform (KLT), the Discrete Cosine Transform (DCT), the Singular Value Decomposition Transform (SVD), and the Asymmetric Discrete Sine Transform (ADST). In an example, the DCT may include transforming a block into the frequency domain. The DCT may include using transform coefficient values based on spatial frequency, with the lowest frequency (i.e., DC) coefficient at the top-left of the matrix and the highest frequency coefficient at the bottom-right of the matrix.

[0053] The quantization unit 430 may convert the transform coefficients into discrete quantum values, which may be referred to as quantized transform coefficients or quantization levels. The quantized transform coefficients can be entropy encoded by the entropy encoding unit 440 to produce entropy-encoded coefficients. Entropy encoding can include using a probability distribution metric. The entropy-encoded coefficients and information used to decode the block, which may include the type of prediction used, motion vectors, and quantizer values, can be output to the compressed bitstream 404. The compressed bitstream 404 can be formatted using various techniques, such as run-length encoding (RLE) and zerorun coding.

[0054] The reconstruction path can be used to maintain reference frame synchronization between the encoder 400 and a corresponding decoder, such as the decoder 500 shown in FIG. 5. The reconstruction path may be similar to the decoding process discussed below and may include decoding the encoded frame, or a portion thereof, which may include decoding an encoded block, which may include dequantizing the quantized transform coefficients at the dequantization unit 450 and inverse transforming the dequantized transform coefficients at the inverse transform unit 460 to produce a derivative residual block. The reconstruction unit 470 may add the prediction block generated by the intra/inter prediction unit 410 to the derivative residual block to create a decoded block. The filtering unit 480 can be applied to the decoded block to generate a reconstructed block, which may reduce distortion, such as blocking artifacts. Although one filtering unit 480 is shown in FIG. 4, filtering the decoded block may include loop filtering, deblocking filtering, or other types of filtering or combinations of types of filtering. The reconstructed block may be stored or otherwise made accessible as a reconstructed block, which may be a portion of a reference frame, for encoding another portion of the current frame, another frame, or both, as indicated by the broken line at 482. Coding information, such as deblocking threshold index values, for the frame may be encoded, included in the compressed bitstream 404, or both, as indicated by the broken line at 484.

[0055] Other variations of the encoder 400 can be used to encode the compressed bitstream 404. For example, a non-transform-based encoder 400 can quantize the residual block directly without the transform unit 420. In some implementations, the quantization unit 430 and the dequantization unit 450 may be combined into a single unit.

[0056] FIG. 5 is a block diagram of a decoder 500 in accordance with implementations of this disclosure. The decoder 500 can be implemented in a device, such as the computing device 100 shown in FIG. 1 or the computing and communication devices 100A, 100B, 100C shown in FIG. 2, as, for example, a computer software program stored in a data storage unit, such as the memory 110 shown in FIG. 1. The computer software program can include machine instructions that may be executed by a processor, such as the processor 120 shown in FIG. 1, and may cause the device to decode video data as described herein. The decoder 500 can be implemented as specialized hardware included, for example, in computing device 100.

[0057] The decoder 500 may receive a compressed bitstream 502, such as the compressed bitstream 404 shown in FIG. 4, and may decode the compressed bitstream 502 to generate an output video stream 504. The decoder 500 may include an entropy decoding unit 510, a dequantization unit 520, an inverse transform unit 530, an intra/inter prediction unit 540, a reconstruction unit 550, a filtering unit 560, or any combination thereof. Other structural variations of the decoder 500 can be used to decode the compressed bitstream 502.

[0058] The entropy decoding unit 510 may decode data elements within the compressed bitstream 502 using, for example, Context Adaptive Binary Arithmetic Decoding, to produce a set of quantized transform coefficients. The dequantization unit 520 can dequantize the quantized transform coefficients, and the inverse transform unit 530 can inverse transform the dequantized transform coefficients to produce a derivative residual block, which may correspond to the derivative residual block generated by the inverse transform unit 460 shown in FIG. 4. Using header information decoded from the compressed bitstream 502, the intra/inter prediction unit 540 may generate a prediction block corresponding to the prediction block created in the encoder 400. At the reconstruction unit 550, the prediction block can be added to the derivative residual block to create a decoded block. The filtering unit 560 can be applied to the decoded block to reduce artifacts, such as blocking artifacts, which may include loop filtering, deblocking filtering, or other types of filtering or combinations of types of filtering, and which may include generating a reconstructed block, which may be output as the output video stream 504.

[0059] Other variations of the decoder 500 can be used to decode the compressed bitstream 502. For example, the decoder 500 can produce the output video stream 504 without the deblocking filtering unit 560.

[0060] FIG. 6 is a block diagram of a representation of a portion 600 of a frame, such as the frame 330 shown in FIG. 3, in accordance with implementations of this disclosure. As shown, the portion 600 of the frame includes four 64x64 blocks 610, in two rows and two columns in a matrix or Cartesian plane. In some implementations, a 64x64 block may be a maximum coding unit, N=64. Each 64x64 block may include four 32x32 blocks 620. Each 32x32 block may include four 16x16 blocks 630. Each 16x16 block may include four 8x8 blocks 640. Each 8x8 block 640 may include four 4x4 blocks 650. Each 4x4 block 650 may include 16 pixels, which may be represented in four rows and four columns in each respective block in the Cartesian plane or matrix. The pixels may include information representing an image captured in the frame, such as luminance information, color information, and location information. In some implementations, a block, such as a 16x16 pixel block as shown, may include a luminance block 660, which may include luminance pixels 662; and two chrominance blocks 670, 680, such as a U or Cb chrominance block 670, and a V or Cr chrominance block 680. The chrominance blocks 670, 680 may include chrominance pixels 690. For example, the luminance block 660 may include 16x16 luminance pixels 662 and each chrominance block 670, 680 may include 8x8 chrominance pixels 690 as shown. Although one arrangement of blocks is shown, any arrangement may be used. Although FIG. 6 shows NxN blocks, in some implementations, NxM blocks may be used. For example, 32x64 blocks, 64x32 blocks, 16x32 blocks, 32x16 blocks, or any other size blocks may be used. In some implementations, Nx2N blocks, 2NxN blocks, or a combination thereof may be used.

[0061] In some implementations, video coding may include ordered block-level coding. Ordered block-level coding may include coding blocks of a frame in an order, such as rasterscan order, wherein blocks may be identified and processed starting with a block in the upper left comer of the frame, or portion of the frame, and proceeding along rows from left to right and from the top row to the bottom row, identifying each block in turn for processing. For example, the 64x64 block in the top row and left column of a frame may be the first block coded and the 64x64 block immediately to the right of the first block may be the second block coded. The second row from the top may be the second row coded, such that the 64x64 block in the left column of the second row may be coded after the 64x64 block in the rightmost column of the first row.

[0062] In some implementations, coding a block may include using quad-tree coding, which may include coding smaller block units within a block in raster- scan order. For example, the 64x64 block shown in the bottom left comer of the portion of the frame shown in FIG. 6, may be coded using quad-tree coding wherein the top left 32x32 block may be coded, then the top right 32x32 block may be coded, then the bottom left 32x32 block may be coded, and then the bottom right 32x32 block may be coded. Each 32x32 block may be coded using quad- tree coding wherein the top left 16x16 block may be coded, then the top right 16x16 block may be coded, then the bottom left 16x16 block may be coded, and then the bottom right 16x16 block may be coded. Each 16x16 block may be coded using quad- tree coding wherein the top left 8x8 block may be coded, then the top right 8x8 block may be coded, then the bottom left 8x8 block may be coded, and then the bottom right 8x8 block may be coded. Each 8x8 block may be coded using quad-tree coding wherein the top left 4x4 block may be coded, then the top right 4x4 block may be coded, then the bottom left 4x4 block may be coded, and then the bottom right 4x4 block may be coded. In some implementations, 8x8 blocks may be omitted for a 16x16 block, and the 16x16 block may be coded using quad-tree coding wherein the top left 4x4 block may be coded, then the other 4x4 blocks in the 16x16 block may be coded in raster- scan order.

[0063] In some implementations, video coding may include compressing the information included in an original, or input, frame by, for example, omitting some of the information in the original frame from a corresponding encoded frame. For example, coding may include reducing spectral redundancy, reducing spatial redundancy, reducing temporal redundancy, or a combination thereof.

[0064] In some implementations, reducing spectral redundancy may include using a color model based on a luminance component (Y) and two chrominance components (U and V or Cb and Cr), which may be referred to as the YUV or YCbCr color model, or color space. Using the YUV color model may include using a relatively large amount of information to represent the luminance component of a portion of a frame and using a relatively small amount of information to represent each corresponding chrominance component for the portion of the frame. For example, a portion of a frame may be represented by a high- resolution luminance component, which may include a 16x16 block of pixels, and by two lower resolution chrominance components, each of which represents the portion of the frame as an 8x8 block of pixels. A pixel may indicate a value, for example, a value in the range from 0 to 255, and may be stored or transmitted using, for example, eight bits. Although this disclosure is described in reference to the YUV color model, any color model may be used. [0065] In some implementations, reducing spatial redundancy may include transforming a block into the frequency domain using, for example, a discrete cosine transform (DCT). For example, a unit of an encoder, such as the transform unit 420 shown in FIG. 4, may perform a DCT using transform coefficient values based on spatial frequency.

[0066] In some implementations, reducing temporal redundancy may include using similarities between frames to encode a frame using a relatively small amount of data based on one or more reference frames, which may be previously encoded, decoded, and reconstructed frames of the video stream. For example, a block or pixel of a current frame may be similar to a spatially corresponding block or pixel of a reference frame. In some implementations, a block or pixel of a current frame may be similar to block or pixel of a reference frame at a different spatial location and reducing temporal redundancy may include generating motion information indicating the spatial difference, or translation, between the location of the block or pixel in the current frame and corresponding location of the block or pixel in the reference frame.

[0067] In some implementations, reducing temporal redundancy may include identifying a portion of a reference frame that corresponds to a current block or pixel of a current frame. For example, a reference frame, or a portion of a reference frame, which may be stored in memory, may be searched to identify a portion for generating a prediction to use for encoding a current block or pixel of the current frame with maximal efficiency. For example, the search may identify a portion of the reference frame for which the difference in pixel values between the current block and a prediction block generated based on the portion of the reference frame is minimized and may be referred to as motion searching. In some implementations, the portion of the reference frame searched may be limited. For example, the portion of the reference frame searched, which may be referred to as the search area, may include a limited number of rows of the reference frame. In an example, identifying the portion of the reference frame for generating a prediction may include calculating a cost function, such as a sum of absolute differences (SAD), between the pixels of portions of the search area and the pixels of the current block.

[0068] In some implementations, the spatial difference between the location of the portion of the reference frame for generating a prediction in the reference frame and the current block in the current frame may be represented as a motion vector. The difference in pixel values between the prediction block and the current block may be referred to as differential data, residual data, a prediction error, or as a residual block. In some implementations, generating motion vectors may be referred to as motion estimation, and a pixel of a current block may be indicated based on location using Cartesian coordinates as /_x, _y. Similarly, a pixel of the search area of the reference frame may be indicated based on location using Cartesian coordinates as r_x, _y. A motion vector (MV) for the current block may be determined based on, for example, a SAD between the pixels of the current frame and the corresponding pixels of the reference frame.

[0069] Although described herein with reference to matrix or Cartesian representation of a frame for clarity, a frame may be stored, transmitted, processed, or any combination thereof, in any data structure such that pixel values may be efficiently represented for a frame or image. For example, a frame may be stored, transmitted, processed, or any combination thereof, in a two-dimensional data structure such as a matrix as shown, or in a onedimensional data structure, such as a vector array. In an implementation, a representation of the frame, such as a two-dimensional representation as shown, may correspond to a physical location in a rendering of the frame as an image. For example, a location in the top left corner of a block in the top left comer of the frame may correspond with a physical location in the top left corner of a rendering of the frame as an image.

[0070] In some implementations, block-based coding efficiency may be improved by partitioning input blocks into one or more prediction partitions, which may be rectangular, including square, partitions for prediction coding. In some implementations, video coding using prediction partitioning may include selecting a prediction partitioning scheme from among multiple candidate prediction partitioning schemes. For example, in some implementations, candidate prediction partitioning schemes for a 64x64 coding unit may include rectangular size prediction partitions ranging in sizes from 4x4 to 64x64, such as 4x4, 4x8, 8x4, 8x8, 8x16, 16x8, 16x16, 16x32, 32x16, 32x32, 32x64, 64x32, or 64x64. In some implementations, video coding using prediction partitioning may include a full prediction partition search, which may include selecting a prediction partitioning scheme by encoding the coding unit using each available candidate prediction partitioning scheme and selecting the best scheme, such as the scheme that produces the least rate-distortion error. [0071] In some implementations, encoding a video frame may include identifying a prediction partitioning scheme for encoding a current block, such as block 610. In some implementations, identifying a prediction partitioning scheme may include determining whether to encode the block as a single prediction partition of maximum coding unit size, which may be 64x64 as shown, or to partition the block into multiple prediction partitions, which may correspond with the sub-blocks, such as the 32x32 blocks 620 the 16x16 blocks 630, or the 8x8 blocks 640, as shown, and may include determining whether to partition into one or more smaller prediction partitions. For example, a 64x64 block may be partitioned into four 32x32 prediction partitions. Three of the four 32x32 prediction partitions may be encoded as 32x32 prediction partitions and the fourth 32x32 prediction partition may be further partitioned into four 16x16 prediction partitions. Three of the four 16x16 prediction partitions may be encoded as 16x16 prediction partitions and the fourth 16x16 prediction partition may be further partitioned into four 8x8 prediction partitions, each of which may be encoded as an 8x8 prediction partition. In some implementations, identifying the prediction partitioning scheme may include using a prediction partitioning decision tree.

[0072] In some implementations, video coding for a current block may include identifying an optimal prediction coding mode from multiple candidate prediction coding modes, which may provide flexibility in handling video signals with various statistical properties and may improve the compression efficiency. For example, a video coder may evaluate each candidate prediction coding mode to identify the optimal prediction coding mode, which may be, for example, the prediction coding mode that minimizes an error metric, such as a rate-distortion cost, for the current block. In some implementations, the complexity of searching the candidate prediction coding modes may be reduced by limiting the set of available candidate prediction coding modes based on similarities between the current block and a corresponding prediction block. In some implementations, the complexity of searching each candidate prediction coding mode may be reduced by performing a directed refinement mode search. For example, metrics may be generated for a limited set of candidate block sizes, such as 16x16, 8x8, and 4x4, the error metric associated with each block size may be in descending order, and additional candidate block sizes, such as 4x8 and 8x4 block sizes, may be evaluated.

[0073] In some implementations, block-based coding efficiency may be improved by partitioning a current residual block into one or more transform partitions, which may be rectangular, including square, partitions for transform coding. In some implementations, video coding, such as video coding using transform partitioning, may include selecting a uniform transform partitioning scheme. For example, a current residual block, such as block 610, may be a 64x64 block and may be transformed without partitioning using a 64x64 transform.

[0074] Although not expressly shown in FIG. 6, a residual block may be transform partitioned using a uniform transform partitioning scheme. For example, a 64x64 residual block may be transform partitioned using a uniform transform partitioning scheme including four 32x32 transform blocks, using a uniform transform partitioning scheme including sixteen 16x16 transform blocks, using a uniform transform partitioning scheme including sixty-four 8x8 transform blocks, or using a uniform transform partitioning scheme including 256 4x4 transform blocks.

[0075] In some implementations, video coding, such as video coding using transform partitioning, may include identifying multiple transform block sizes for a residual block using multiform transform partition coding. In some implementations, multiform transform partition coding may include recursively determining whether to transform a current block using a current block size transform or by partitioning the current block and multiform transform partition coding each partition. For example, the bottom left block 610 shown in FIG. 6 may be a 64x64 residual block, and multiform transform partition coding may include determining whether to code the current 64x64 residual block using a 64x64 transform or to code the 64x64 residual block by partitioning the 64x64 residual block into partitions, such as four 32x32 blocks 620, and multiform transform partition coding each partition. In some implementations, determining whether to transform partition the current block may be based on comparing a cost for encoding the current block using a current block size transform to a sum of costs for encoding each partition using partition size transforms.

[0076] FIG. 7 is a flow diagram of an example of decoding using intra prediction with angle refinement 700. Decoding using intra prediction with angle refinement 700 may be implemented by a decoder, such as the decoder 500 shown in FIG. 5. Decoding using intra prediction with angle refinement 700 includes block-based hybrid video coding as described herein.

[0077] Decoding using intra prediction with angle refinement 700 includes generating reconstructed video data by decoding an encoded bitstream, such as the compressed bitstream 502 shown in FIG. 5, or one or more portions thereof, to generate a reconstructed video, or a portion thereof, such as the output video stream 504 shown in FIG. 5.

[0078] Decoding using intra prediction with angle refinement 700 includes obtaining an encoded bitstream (at 710), accessing an angle mode value (at 720), accessing an angle delta value (at 730), obtaining an angle refinement value (at 740), obtaining a current intra prediction angle value (at 750), obtaining an intra prediction block (at 760), obtaining a reconstructed block (at 770), and outputting a reconstructed frame (at 780). One or more aspects of decoding using intra prediction with angle refinement 700 may be omitted from the description herein for simplicity and brevity.

[0079] The decoder, or a component thereof, such as an entropy decoding unit of the decoder, such as the entropy decoding unit 510 shown in FIG. 5, receives, reads, obtains, or otherwise accesses, an encoded bitstream (at 710), or one or more portions thereof, such as the compressed bitstream 502 shown in FIG. 5 or the compressed bitstream 404 shown in FIG. 4.

[0080] Obtaining the encoded bitstream includes identifying a current frame from a current sequence of frames to decode from the encoded bitstream to generate a current reconstructed frame. Obtaining the encoded bitstream includes identifying a current block of the current frame to decode from the encoded bitstream to generate a current reconstructed block for the current reconstructed frame.

[0081] The decoder, or a component thereof, extracts, reads, decodes, or otherwise accesses, from the encoded bitstream, the angle mode, or group, value (at 720) for decoding the current block (current angle mode).

[0082] The encoded bitstream includes, for the current block, which is an intra coded block, data, which may be encoded data, such as one or more encoded symbols, indicating an angle mode value for angular, or directional, intra prediction for the current block. The angle mode value indicates an angle (primary angle) for angular, or directional, intra prediction for the current block. The angle mode value is a value from a defined set of available angle mode values (available angle modes), such as a defined set of available angle mode values including eight available angle mode values, corresponding to eight angular intra prediction modes.

[0083] For example, the defined set of available angle mode values may include a first angle mode value indicating a forty-five degree angle mode corresponding to forty-five degree angular prediction, a second angle mode value indicating a sixty-seven degree angle mode corresponding to sixty-seven degree angular prediction, a third angle mode value indicating a ninety degree angle mode corresponding to ninety degree angular prediction, a fourth angle mode value indicating a one hundred thirteen degree angle mode corresponding to hundred thirteen degree angular prediction, a fifth angle mode value indicating a one hundred thirty-five degree angle mode corresponding to one hundred thirty-five degree angular prediction, a sixth angle mode value indicating a one hundred fifty- seven degree angle mode corresponding to one hundred fifty-seven degree angular prediction, a seventh angle mode value indicating a one hundred eighty degree angle mode corresponding to one hundred eighty degree angular prediction, and an eighth angle mode value indicating a two hundred three degree angle mode corresponding to two hundred three degree angular prediction. The available angle mode values represent angles (degrees) and may be expressed as {45, 67, 90, 113, 135, 157, 180, 203}. Other angle mode values corresponding to other directional prediction angles may be used.

[0084] The decoder, or a component thereof, extracts, reads, decodes, or otherwise accesses, from the encoded bitstream, the angle delta value (at 730) (angle_delta) for decoding the current block.

[0085] The encoded bitstream includes, for the current block, data, which may be encoded data, indicating an angle delta value for angular, or directional, intra prediction for the current block. The angle delta value, or angular offset, is a value from a defined set of available angle delta values, such as a defined set of available angle delta values including seven available angle delta values. The angle dental value indicates an angular offset, such as a number of degrees, relative to the angle indicated by the current angle mode, corresponding to seven angular intra predictions modes per angle mode, corresponding, in combination, to fifty- six directional intra prediction angles. [0086] For example, the defined set of available angle delta values may include a first angle delta value indicating a delta, or offset, of negative nine (-9) degrees from the angle indicated by the current angle mode (negative nine degree angle delta value), a second angle delta value indicating a delta, or offset, of negative six (-6) degrees from the angle indicated by the current angle mode (negative six degree angle delta value), a third angle delta value indicating a delta, or offset, of negative three (-3) degrees from the angle indicated by the current angle mode (negative three degree angle delta value), a fourth angle delta value indicating a delta, or offset, of zero (0) degrees from the angle indicated by the current angle mode (zero degree angle delta value), a fifth angle delta value indicating a delta, or offset, of positive three (3 or +3) degrees from the angle indicated by the current angle mode (three degree angle delta value), a sixth angle delta value indicating a delta, or offset, of positive six (6 or +6) degrees from the angle indicated by the current angle mode (six degree angle delta value), and a seventh angle delta value indicating a delta, or offset, of positive nine (9 or +9) degrees from the angle indicated by the current angle mode (nine degree angle delta value). The available angle delta values represent angular offsets from the angle indicated by the current angle mode and may be expressed as {-9, -6, -3, 0, +3, +6, +9}. Other angle delta values corresponding to other directional prediction angles may be used.

[0087] In implementations that omit intra prediction with angle refinement as described herein, the current intra prediction angle for directional intra prediction for the current block is obtained as a combination, such as a sum, of the directional prediction angle indicated by the current angle mode value and the angular offset indicated by the current angle delta value, which may be expressed as the following:

Angle = primary mode {45, 67, 90, 113, 135, 157, 180, 203} + angle_delta {-9, -6, -3, 0, +3, +6, +9}.

[0088] In implementations that include intra prediction with angle refinement as described herein, the decoder, or a component thereof, obtains, determines, calculates, or otherwise identifies, the angle refinement value (at 740) for decoding the current block.

[0089] The angle refinement value indicates an angle refinement, or adjustment, such as plus one degree (one degree angle refinement value), zero degrees (zero degree angle refinement value), or minus one degree (negative one degree angle refinement value), relative to the angle corresponding to the combination of the angle mode value (obtained at 720) and the angle delta value (obtained at 720), from a defined set of available angle refinement values, such as three available angle refinement values, which may be expressed as {-1, 0, 1 ], corresponding to three direction intra predictions angles per angle from the fifty-six angular modes identified by the combination of the angle mode value and the angle delta value, corresponding to one hundred sixty eight (168) available intra prediction angles in accordance with the combination of the angle mode value, the angle delta value, and the angle refinement value (angle_refinement).

[0090] The current intra prediction angle (Angle) for intra prediction of the current block may be obtained, such as by the decoder, or a component thereof, as a combination, such as a summation, of the angle indicated by the angular prediction mode (angle mode value obtained at 720), the angular offset (angle delta value obtained at 730), and the angle refinement (angle refinement value obtained at 740), which may be expressed as the following:

Angle = primary mode {45, 67, 90, 113, 135, 157, 180, 203} + angle_delta {-9, -6, -3, 0, +3, +6, +9} + angle_refinement {-l, 0, 1}.

[Equation 1] [0091] In some implementations, the encoded bitstream may include singly encoded data, such as one or more singly encoded syntax elements indicating the angle refinement and the decoder may obtain the angle refinement value by decoding, such as entropy decoding, the singly encoded syntax elements indicating the angle refinement from the encoded bitstream. [0092] In some implementations, singly encoded an indication, such as data, such as one or more singly encoded syntax elements, indicating the angle refinement may be absent, omitted, or otherwise unavailable, from the encoded bitstream and the encoded bitstream may include jointly coded data, which may be entropy coded data, such as one or more jointly coded syntax elements, indicating another coding parameter, such as a multiple reference line index value (mrl_index) for intra prediction for the current block, and the angle refinement value may be obtained in accordance with the jointly coded syntax element or elements.

[0093] For example, the encoded bitstream may include, for the current block, data, which may be entropy coded data, such as an entropy coded multiple reference line index value syntax element, indicating a multiple reference line index value (mrl_index) for intra prediction for the current block, and the angle refinement value may be obtained in accordance with the multiple reference line index value.

[0094] Directional, or angular, intra prediction includes predicting the current block using available, such as previously reconstructed, pixel values from one or more available, such as previously reconstructed, blocks adjacent, such as immediately adjacent, to the current block in accordance with the current intra prediction angle. [0095] For example, the available pixel values may include previously reconstructed pixel values from a row, or line, of previously reconstructed pixel values from a previously reconstructed block immediately above the current block, a previously reconstructed block immediately above and to the left of the current block, a previously reconstructed block immediately above and to the right of the current block, or a combination thereof. In another example, the available pixel values may include previously reconstructed pixel values from a column, or line, of pixel values from a previously reconstructed block immediately to the left of the current block, a previously reconstructed block immediately above and to the left of the current block, a previously reconstructed block immediately below and to the left of the current block, or a combination thereof.

[0096] The previously reconstructed pixel values for intra prediction of the current block may be identified, or selected, from a set, collection, or group, of one or more available lines of previously reconstructed pixel values identified as available intra prediction reference lines.

[0097] For example, a first available intra prediction reference line (reference line zero (0)) may include previously reconstructed pixel values from a row of previously reconstructed pixels vertically immediately adjacent to the current block, such as from the previously reconstructed block immediately above the current block, the previously reconstructed block immediately above and to the left of the current block, and the previously reconstructed block immediately above and to the right of the current block, and from a column of previously reconstructed pixels horizontally immediately adjacent to the current block, such as from the previously reconstructed block immediately to the left of the current block and the previously reconstructed block immediately below and to the left of the current block.

[0098] A second available intra prediction reference line (reference line one (1)) may include previously reconstructed pixel values from a row of previously reconstructed pixels vertically immediately adjacent to the first available intra prediction reference line, distal to the current block, such as from the previously reconstructed block immediately above the current block, the previously reconstructed block immediately above and to the left of the current block, and the previously reconstructed block immediately above and to the right of the current block, and from a column of previously reconstructed pixels horizontally immediately adjacent to the first available intra prediction reference line, distal to the current block, such as from the previously reconstructed block immediately to the left of the current block and the previously reconstructed block immediately below and to the left of the current block.

[0099] A third available intra prediction reference line (reference line two (2)) may include previously reconstructed pixel values from a row of previously reconstructed pixels vertically immediately adjacent to the second available intra prediction reference line, distal to the current block, such as from the previously reconstructed block immediately above the current block, the previously reconstructed block immediately above and to the left of the current block, and the previously reconstructed block immediately above and to the right of the current block, and from a column of previously reconstructed pixels horizontally immediately adjacent to the second available intra prediction reference line, distal to the current block, such as from the previously reconstructed block immediately to the left of the current block and the previously reconstructed block immediately below and to the left of the current block.

[0100] A fourth available intra prediction reference line (reference line three (3)) may include previously reconstructed pixel values from a row of previously reconstructed pixels vertically immediately adjacent to the third available intra prediction reference line, distal to the current block, such as from the previously reconstructed block immediately above the current block, the previously reconstructed block immediately above and to the left of the current block, and the previously reconstructed block immediately above and to the right of the current block, and from a column of previously reconstructed pixels horizontally immediately adjacent to the third available intra prediction reference line, distal to the current block, such as from the previously reconstructed block immediately to the left of the current block and the previously reconstructed block immediately below and to the left of the current block.

[0101] In implementations that omit, exclude, or avoid, intra prediction with angle refinement as described herein, such as wherein multiple reference line selection is disabled, or otherwise unavailable, the first available intra prediction reference line may be used for intra prediction and the second intra prediction reference line, the third intra prediction reference line, and the fourth intra prediction reference line may be unavailable.

[0102] In implementations that include intra prediction with angle refinement as described herein, the decoder, or a component thereof, extracts, reads, decodes, or otherwise accesses, from the encoded bitstream, the multiple reference line index value, such as by decoding, such as entropy decoding, the entropy coded multiple reference line index value syntax. [0103] Obtaining the angle refinement value (at 740) includes obtaining the angle refinement value in accordance with the multiple reference line index value syntax element accessed from the encoded bitstream or the corresponding multiple reference line index value. Obtaining the angle refinement value in accordance with a multiple reference line index value syntax element accessed from the encoded bitstream or the corresponding multiple reference line index value includes using, as the angle refinement value, a result of using the multiple reference line index value as an index value to a defined array, index, or other data structure, of angle refinement values (mrl_index_to_delta). The defined array, index, or other data structure, of angle refinement values has a size corresponding to the number, count, or cardinality of available intra prediction reference lines, such as four (4). For example, the defined array, index, or other data structure, of angle refinement values may include a first value of zero (0), a second value of one (1), a third value of negative one (-1), and a fourth value of zero (0), which may be expressed as the following: const int mrl_index_to_delta[4] = {0, 1, -1, 0}.

[0104] Data identifying the angle refinement value for the current block, such as expressly, other than the multiple reference line index, is absent, omitted, or otherwise unavailable, from the encoded bitstream. In some implementations, the angle refinement value may be obtained, or derived, from other data, which may include another syntax element signaled in the bitstream.

[0105] Obtaining the angle refinement value (angle_refinement) in accordance with a multiple reference line index value syntax element accessed from the encoded bitstream or the corresponding multiple reference line index value (mrl_index) using the defined array, index, or other data structure, of angle refinement values (mrl_index_to_delta) may be expressed as the following: angle_refinement += mrljndex_to_delta[mrljndex].

[0106] In some implementations, the current intra prediction angle (p_angle) for decoding the current block may be obtained by combining, such as summing, the angle indicated by the angular prediction mode (angle mode value obtained at 720), the angular offset (angle delta value obtained at 730), and the angle refinement value, which may be expressed as the following: p_angle = primary mode, p_angle += angle_delta, p_angle += mrljndex_to_delta[mrljndex].

[Equation 2] [0107] In some implementations, obtaining the angle refinement value (at 740) includes decoding the multiple reference line index value syntax element from the encoded bitstream using a current multiple reference line index value coding context from a plurality of available multiple reference line index value coding contexts.

[0108] The decoder, or a component thereof, obtains the current multiple reference line index value coding context (at 740), including a cumulative density function or probability distribution, for decoding the multiple reference line index value for decoding the current block. The current multiple reference line index value coding context may be one of a defined set of available multiple reference line index value coding contexts for decoding the multiple reference line index value.

[0109] In some implementations, the available multiple reference line index value coding contexts for decoding the multiple reference line index value include three available multiple reference line index value coding contexts, such as a first available multiple reference line index value coding context (context zero (0)), a second available multiple reference line index value coding context (context one (1)), and a third available multiple reference line index value coding context (context two (2)). Other coding contexts may be used.

[0110] In some implementations, obtaining the current multiple reference line index value coding context includes obtaining the current multiple reference line index value coding context in accordance with the respective multiple reference line index value used to code one or more, such as two, neighboring blocks, such as a block above the current block and a block to the left of the current block.

[0111] To obtain, or determine, the current multiple reference line index value coding context, the decoder, or a component thereof, obtains, or accesses, the multiple reference line index value used to code the neighboring blocks.

[0112] To obtain, or determine, the current multiple reference line index value coding context, the decoder, or a component thereof, determines whether a first multiple reference line index value for a first previously coded neighboring block is greater than zero.

[0113] To obtain, or determine, the current multiple reference line index value coding context, the decoder, or a component thereof, determines whether a second multiple reference line index value for a second previously coded neighboring block is greater than zero.

[0114] In some implementations, the decoder, or the component thereof, determines that the first multiple reference line index value for the first previously coded neighboring block is less than or equal to zero and determines that the second multiple reference line index value for the second previously coded neighboring block is less than or equal to zero. In response to determining that the first multiple reference line index value for the first previously coded neighboring block is less than or equal to zero and the second multiple reference line index value for the second previously coded neighboring block is less than or equal to zero, the decoder, or a component thereof, uses the first multiple reference line index value coding context (context zero (0)) as the current multiple reference line index value coding context. [0115] In some implementations, the decoder, or the component thereof, determines that the first multiple reference line index value for the first previously coded neighboring block is less than or equal to zero and determines that the second multiple reference line index value for the second previously coded neighboring block is greater than zero. In response to determining that the first multiple reference line index value for the first previously coded neighboring block is less than or equal to zero and the second multiple reference line index value for the second previously coded neighboring block is greater than zero, the decoder, or a component thereof, uses the second multiple reference line index value coding context (context one (1)) as the current multiple reference line index value coding context.

[0116] In some implementations, the decoder, or the component thereof, determines that the first multiple reference line index value for the first previously coded neighboring block is greater than zero and determines that the second multiple reference line index value for the second previously coded neighboring block is less than or equal to zero. In response to determining that the first multiple reference line index value for the first previously coded neighboring block is greater than zero and the second multiple reference line index value for the second previously coded neighboring block is less than or equal to zero, the decoder, or a component thereof, uses the second multiple reference line index value coding context (context one (1)) as the current multiple reference line index value coding context.

[0117] In some implementations, the decoder, or the component thereof, determines that the first multiple reference line index value for the first previously coded neighboring block is greater than zero and determines that the second multiple reference line index value for the second previously coded neighboring block is greater than zero. In response to determining that the first multiple reference line index value for the first previously coded neighboring block is greater than zero and the second multiple reference line index value for the second previously coded neighboring block is greater than zero, the decoder, or a component thereof, uses the third multiple reference line index value coding context (context two (2)) as the current multiple reference line index value coding context.

[0118] The decoder, or a component thereof, extracts, reads, decodes, or otherwise accesses, from the encoded bitstream, such as by decoding, such as entropy decoding, the multiple reference line index value using the current multiple reference line index value coding context. [0119] The decoder, or a component thereof, obtains the intra prediction angle value (at 750). The decoder, or the component thereof, obtains, as the intra prediction angle value, a combination, such as a sum, of the angle mode value, the angle delta value, and the angle refinement value, as shown in Equation 1 or Equation 2. The intra prediction angle value indicates an intra prediction angle from the one hundred sixty-eight (168) available intra prediction angles.

[0120] In some implementations, decoding using intra prediction with angle refinement 700 includes using an angle-to-slope, or direction derivative, table (dr_intra_derivative). The direction derivative table is used to determine slope for intra prediction. The direction derivative table values may be stored in fixed point Q10.6 format, indicating ten (10) bits for the integer part and six (6) bits for the decimal, or fractional, part. So that predictions from left and above use matching slope, a property is met that may be expressed as the following: dr Jntra_derivative [angle] = (64*64)/ dr_intra_derivative[90-angle].

[0121] In the absence of using the angle refinement, a direction derivative table is defined, wherein the delimiter “//” indicates that data to the right of the delimiter is comment data indicating an approximate angle, and wherein zero values are unused, as follows: static const intl6_t dr_intra_derivative[90] = {

0, 0, 0, //

1023, 0, 0, // 3, ...

547, 0, 0, // 6, ...

372, 0, 0, 0, 0, // 9, ...

273, 0, 0, // 14, ...

215, 0, 0, // 17, ...

178, 0, 0, // 20, ...

151, 0, 0, // 23, ... (113 & 203 are base angles)

132, 0, 0, // 26, ...

116, 0, 0, // 29, ...

102, 0, 0, 0, // 32, ...

90, 0, 0, // 36, ...

80, 0, 0, // 39, ...

71, 0, 0, // 42, ...

64, 0, 0, // 45, ... (45 & 135 are base angles)

57, 0, 0, // 48, ...

51, 0, 0, // 51, ... 45, 0, 0, 0, // 54, ...

40, 0, 0, // 58, ...

35, 0, 0, // 61, ...

31, 0, 0, // 64, ...

27, 0, 0, 11 67, ... (67 & 157 are base angles)

23, 0, 0, // 70, ...

19, 0, 0, // 73, ...

15, 0, 0, 0, 0, // 76, ...

11, 0, 0, // 81, ...

7, 0, 0, // 84, ...

3, 0, 0, // 87, ....

[0122] In the presence of, or using, the angle refinement, the direction derivative table is defined, wherein the delimiter “//” indicates that data to the right of the delimiter is comment data indicating an approximate angle, and wherein the asterisk symbol indicates an unused value, as follows: static const intl6_t dr_intra_derivative[90] = {

0, 4096, 2048, // *, 0.9, 1.8,

1365, 1024, 819, // 2.7, 3.6, 4.5,

682, 585, 512, // 5.4, 6.2, 7.1,

455, 409, 409, 409, 372, // 8.0, 8.9, *, *, 9.8,

341, 292, 273, // 10.6, 12.4, 13.2,

256, 227, 215, // 14.0, 15.7, 16.6,

204, 186, 178, // 17.4, 19.0, 19.8,

170, 157, 151, // 20.6, 22.2, 23.0,

146, 136, 132, // 23.7, 25.2, 25.9,

128, 117, 110, // 26.6, 28.7, 30.2,

107, 99, 97, 97, // 30.9, 32.9, *, 33.4,

93, 87, 83, // 34.5, 36.3, 37.6,

81, 77, 74, // 38.3, 39.7, 40.9,

73, 69, 66, // 41.2, 42.8, 44.1,

64, 62, 59, // 45.0, 45.9, 47.3,

56, 55, 53, // 48.8, 49.3, 50.4,

50, 49, 47, // 52.0, 52.6, 53.7,

44, 42, 42, 41, // 55.5, 56.7, *, 57.4,

-SO- 38, 37, 35, // 59.3, 60.0, 61.3,

32, 31, 30, // 63.4, 64.2, 64.9, 28, l, 26, // 66.4, 67.1, 67.9, 24, 23, 22, // 69.4, 70.2, 71.0, 20, 19, 18, // 72.6, 73.5, 74.3, 16, 15, 14, // 76.0, 76.8, 77.7,

12, 11, 10, 10, 10, // 79.4, 80.2, *, *, 81.1,

9, 8, 7, // 82.0, 82.9, 83.8, 6, 5, 4, // 84.6, 85.5, 86.4, 3, 2, 1, // 87.3, 88.2, 89.1, };■

[0123] The decoder, or a component thereof, obtains the intra prediction block (at 760). To obtain the intra prediction block the decoder, or the component thereof, predicts the intra prediction block for the current block by intra predicting pixel values for the intra prediction block using, or in accordance with, the current intra prediction angle value, such as based on previously reconstructed pixel values from the intra prediction reference line indicated by the current multiple reference line index value.

[0124] The decoder, or a component thereof, obtains a reconstructed block, or reconstructed block data, (at 770) using the intra prediction block, such as by combining a reconstructed residual block with the intra prediction block.

[0125] The decoder, or a component thereof, includes the reconstructed block in a reconstructed frame.

[0126] The decoder, or a component thereof, outputs the reconstructed frame (at 780) including the reconstructed block, such as for storage or presentation.

[0127] FIG. 8 is a flow diagram of an example of encoding using intra prediction with angle refinement 800. Encoding using intra prediction with angle refinement 800 may be implemented by an encoder, such as the encoder 400 shown in FIG. 4.

[0128] Encoding using intra prediction with angle refinement 800 includes encoding an input video steam, such as the input video stream 402 shown in FIG. 4, or one or more portions thereof, to generate an encoded (compressed) output bitstream, such as the encoded (compressed) bitstream 404 shown in FIG. 4.

[0129] In block-based hybrid video coding, to reduce, or minimize, the resource utilization, such as bandwidth utilization, for signaling, storing, or both, compressed, or encoded, video data, redundant data, such as spatially redundant data, temporally redundant data, or both, is omitted or excluded from the compressed, or encoded, data.

[0130] Encoding using intra prediction with angle refinement 800 includes obtaining a current block (at 810), obtaining encoded block data (at 820), and outputting an encoded bitstream (at 830).

[0131] Input video data is obtained (at 810). The input video data includes a frame or a sequence of frames (input frames). For example, the encoder, or a component thereof, such as an intra/inter prediction unit of the encoder, such as the intra/inter prediction unit 410 shown in FIG. 4, receives, reads, obtains, or otherwise accesses, an input frame or an input video stream (at 810), such as the input video steam 402 shown in FIG. 4, or one or more portions thereof. The encoder, or a component thereof, identifies the input frame, or a frame from the input video stream, as a current frame. The current frame may be obtained (at 810) subsequent to encoding one or more other frames, such as a frame sequentially preceding the current frame in the input video stream, and generating, or otherwise obtaining, a corresponding reconstructed frame (or frames), or one or more portions thereof, for use as a reference frame (or frames) for encoding the current frame.

[0132] The encoder, or a component thereof, obtains the current block from the current frame. The current block for encoding is obtained (at 810) from the current frame. The current block may be obtained (at 810) subsequent to encoding one or more other blocks, such as a block sequentially preceding the current block in the current frame, in accordance with a block coding order for coding the current frame, and generating, or otherwise obtaining, a corresponding reconstructed block, or one or more portions thereof.

[0133] The encoder, or a component thereof, obtains encoded block data (at 820) by encoding the current block.

[0134] Encoding the current block includes obtaining a directional, or angular, intra prediction angle value (at 840), obtaining an angle mode value, an angle delta value, and an angle refinement value (at 850), obtaining intra prediction block data (at 860), including the angle mode value and the angle delta value in the encoded block data (at 870), and including a multiple reference line index value syntax element in the encoded block data (at 880). [0135] The encoder, or a component thereof, obtains a directional intra prediction angle value (at 840) for encoding the current block. Obtaining the intra prediction angle value includes performing rate distortion optimization, which includes identifying the intra prediction angle value for encoding the current block from multiple available intra prediction angle values.

[0136] Obtaining the directional intra prediction angle value includes multiple reference line selection (MRLS) to identify, or obtain, a multiple reference line index value indicating an intra prediction reference line for intra prediction for the current block. For example, the encoder may evaluate one or more of the available combinations of a directional intra prediction angle value from the available directional intra prediction angle values, such as the 168 available directional intra prediction angle values as described herein, and the available intra prediction reference lines, such the four available intra prediction reference lines as described herein.

[0137] In some implementations, the encoder may determine that one or more of the intra prediction reference lines are unavailable for coding the current block and may omit, skip, or avoid evaluating the unavailable available intra prediction reference lines. For example, the encoder determines, such as based on rate distortion optimization, that encoding the current block using the first intra prediction reference line (reference line zero (0)) corresponds with a more optimal rate distortion optimization result than encoding the current block using the second intra prediction reference line (reference line one (1)) and, in response, determines that the third intra prediction reference line (reference line two (2)) and fourth intra prediction reference line (reference line three (3)) are unavailable for encoding the current block.

[0138] In some implementations, the encoder determines that the four intra prediction reference lines are available for encoding the current block. For example, on a condition that, or in response to determining that, a first coding cost, or rate distortion optimization result, for encoding the current block with reference to the first intra prediction reference line (reference line zero (0)) immediately adjacent to the current block is less than a second coding cost, or rate distortion optimization result, for encoding the current block with reference to a second intra prediction reference line (reference line one (1)) immediately adjacent to the first intra prediction reference line, obtaining the multiple reference line index value includes obtaining, as the multiple reference line index value, a multiple reference line index value corresponding to a minimal cost value among the first coding cost, the second coding cost, a third coding cost, or rate distortion optimization result, for encoding the current block with reference to a third intra prediction reference line (reference line two (2)) immediately adjacent to the second intra prediction reference line, and a fourth coding cost, or rate distortion optimization result, for encoding the current block with reference to a fourth intra prediction reference line (reference line three (3)) immediately adjacent to the third intra prediction reference line.

[0139] The encoder, or a component thereof, obtains an angle mode value, an angle delta value, and an angle refinement value (at 850) in accordance with the directional intra prediction angle value, such as in accordance with Equation 1 or Equation 2.

[0140] The encoder, or a component thereof, obtains the intra prediction block data (at 860) using directional intra prediction in accordance with the intra prediction angle value. The encoder, or a component thereof, obtains residual block data by subtracting the intra prediction block data from the current block data. The encoder, or a component thereof, includes encoded, such as entropy coded, residual data in the encoded block data.

[0141] The encoder, or a component thereof, includes the angle mode value in the encoded block data (at 870), such as by encoding, such as entropy coding, one or more syntax elements representing the angle mode value to obtain encoded data for the angle mode value and including the encoded data for the angle mode value in the encoded block data.

[0142] The encoder, or a component thereof, includes the angle delta value in the encoded block data (at 870), such as by encoding, such as entropy coding, one or more syntax elements representing the angle delta value to obtain encoded data for the angle delta value and including the encoded data for the angle delta value in the encoded block data.

[0143] The encoder, or a component thereof, includes the multiple reference line index value in the encoded block data (at 880).

[0144] Including the multiple reference line index value in the encoded block data includes obtaining a multiple reference line index value syntax element representing the multiple reference line index value.

[0145] Including the multiple reference line index value in the encoded block data includes obtaining a current multiple reference line index value coding context for entropy coding the multiple reference line index value syntax element. Obtaining the current multiple reference line index value coding context is similar to obtaining the current multiple reference line index value coding context as described with respect to FIG. 7, except as is described herein or as is otherwise clear from context.

[0146] Including the multiple reference line index value in the encoded block data includes entropy coding the multiple reference line index value syntax element in accordance with a cumulative distribution function, or probability distribution, indicated by the current multiple reference line index value coding context to obtain encoded multiple reference line index value syntax element data and including the encoded multiple reference line index value syntax element data in the encoded block data. The multiple reference line index value syntax element jointly codes, or indicates, the intra prediction reference line and the angle refinement value in the encoded block data for the current block.

[0147] The encoder omits, excludes, avoids, or skips, including data in the encoded bitstream, such as the encoded block data, other than the multiple reference line index value, that indicates the angle refinement value.

[0148] The encoder, or a component thereof, outputs the encoded bitstream (at 830). Outputting the encoded bitstream (at 830) includes including the encoded block data (obtained at 820) in the encoded bitstream. Outputting the encoded bitstream (at 830) includes storing, transmitting, such as to a decoder, or both, the encoded bitstream.

[0149] As used herein, the terms “optimal”, “optimized”, “optimization”, or other forms thereof, are relative to a respective context and are not indicative of absolute theoretic optimization unless expressly specified herein.

[0150] As used herein, the term “set” indicates a distinguishable collection or grouping of zero or more distinct elements or members that may be represented as a one-dimensional array or vector, except as expressly described herein or otherwise clear from context.

[0151] The words “example” or “exemplary” are used herein to mean serving as an example, instance, or illustration. Any aspect or design described herein as “example” or “exemplary” not necessarily to be construed as preferred or advantageous over other aspects or designs. Rather, use of the words “example” or “exemplary” is intended to present concepts in a concrete fashion. As used in this application, the term “or” is intended to mean an inclusive “or” rather than an exclusive “or”. That is, unless specified otherwise, or clear from context, “X includes A or B” is intended to mean any of the natural inclusive permutations. That is, if X includes A; X includes B; or X includes both A and B, then “X includes A or B” is satisfied under any of the foregoing instances. In addition, the articles “a” and “an” as used in this application and the appended claims should generally be construed to mean “one or more” unless specified otherwise or clear from context to be directed to a singular form. Moreover, use of the term “an embodiment” or “one embodiment” or “an implementation” or “one implementation” throughout is not intended to mean the same embodiment or implementation unless described as such.

[0152] As used herein, the terms “determine” and “identify”, or any variations thereof, includes selecting, ascertaining, computing, looking up, receiving, determining, establishing, obtaining, or otherwise identifying or determining in any manner whatsoever using one or more of the devices shown in FIG. 1. As used herein, the term “obtain”, or any variation thereof, includes selecting, ascertaining, computing, looking up, receiving, determining, establishing, accessing, reading, calculating, generating, or otherwise identifying in any manner whatsoever using one or more of the devices shown in FIG. 1, or one or more components thereof. As used herein, the term “access”, or any variation thereof, includes selecting, ascertaining, computing, looking up, receiving, determining, obtaining, reading, calculating, extracting, or otherwise identifying in any manner whatsoever using one or more of the devices shown in FIG. 1, or one or more components thereof. As used herein, the terminology “generating”, or any variations thereof, includes combining, calculating, computing, aggregating, rendering, laying out, drawing, or otherwise producing in any manner whatsoever using one or more of the devices shown and described herein. As used herein, the terminology “receiving” includes receiving via a network, retrieving from memory, or otherwise ascertaining the identified information.

[0153] Further, for simplicity of explanation, although the figures and descriptions herein may include sequences or series of steps or stages, elements of the methods disclosed herein can occur in various orders and/or concurrently. Additionally, elements of the methods disclosed herein may occur with other elements not explicitly presented and described herein. Furthermore, one or more elements of the methods described herein may be omitted from implementations of methods in accordance with the disclosed subject matter.

[0154] The implementations of the transmitting computing and communication device 100A and/or the receiving computing and communication device 100B (and the algorithms, methods, instructions, etc. stored thereon and/or executed thereby) can be realized in hardware, software, or any combination thereof. The hardware can include, for example, computers, intellectual property (IP) cores, application-specific integrated circuits (ASICs), programmable logic arrays, optical processors, programmable logic controllers, microcode, microcontrollers, servers, microprocessors, digital signal processors or any other suitable circuit. In the claims, the term “processor” should be understood as encompassing any of the foregoing hardware, either singly or in combination. The terms “signal” and “data” are used interchangeably. Further, portions of the transmitting computing and communication device 100A and the receiving computing and communication device 100B do not necessarily have to be implemented in the same manner.

[0155] Further, in one implementation, for example, the transmitting computing and communication device 100A or the receiving computing and communication device 100B can be implemented using a computer program that, when executed, carries out any of the respective methods, algorithms and/or instructions described herein. In addition, or alternatively, for example, a special purpose computer/processor can be utilized which can contain specialized hardware for carrying out any of the methods, algorithms, or instructions described herein.

[0156] The transmitting computing and communication device 100A and receiving computing and communication device 100B can, for example, be implemented on computers in a real-time video system. Alternatively, the transmitting computing and communication device 100A can be implemented on a server and the receiving computing and communication device 100B can be implemented on a device separate from the server, such as a hand-held communications device. In this instance, the transmitting computing and communication device 100A can encode content using an encoder 400 into an encoded video signal and transmit the encoded video signal to the communications device. In turn, the communications device can then decode the encoded video signal using a decoder 500. Alternatively, the communications device can decode content stored locally on the communications device, for example, content that was not transmitted by the transmitting computing and communication device 100A. Other suitable transmitting computing and communication device 100A and receiving computing and communication device 100B implementation schemes are available. For example, the receiving computing and communication device 100B can be a generally stationary personal computer rather than a portable communications device and/or a device including an encoder 400 may also include a decoder 500.

[0157] Further, all or a portion of implementations can take the form of a computer program product accessible from, for example, a tangible computer-usable or computer- readable medium. A computer-usable or computer-readable medium can be any device that can, for example, tangibly contain, store, communicate, or transport the program for use by or in connection with any processor. The medium can be, for example, an electronic, magnetic, optical, electromagnetic, or a semiconductor device. Other suitable mediums are also available.

[0158] It will be appreciated that aspects can be implemented in any convenient form. For example, aspects may be implemented by appropriate computer programs which may be carried on appropriate carrier media which may be tangible carrier media (e.g., disks) or intangible carrier media (e.g. communications signals). Aspects may also be implemented using suitable apparatus which may take the form of programmable computers running computer programs arranged to implement the methods and/or techniques disclosed herein. Aspects can be combined such that features described in the context of one aspect may be implemented in another aspect.

[0159] The above-described implementations have been described in order to allow easy understanding of the application are not limiting. On the contrary, the application covers various modifications and equivalent arrangements included within the scope of the appended claims, which scope is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structure as is permitted under the law.

Claims

CLAIMS What is claimed is:

1. A method comprising: generating reconstructed block data by decoding, from an encoded bitstream, a current block of a current frame, wherein decoding the current block includes: accessing, from the encoded bitstream, an angle mode value; accessing, from the encoded bitstream, an angle delta value; obtaining an angle refinement value; obtaining, as an intra prediction angle value, a combination of the angle mode value, the angle delta value, and the angle refinement value; obtaining an intra prediction block by intra prediction in accordance with the intra prediction angle value; and obtaining the reconstructed block data using the intra prediction block; including the reconstructed block data in reconstructed frame data; and outputting the reconstructed frame data.

2. The method of claim 1, wherein: obtaining the angle refinement value includes obtaining the angle refinement value in accordance with a multiple reference line index value syntax element accessed from the encoded bitstream, wherein the multiple reference line index value syntax element indicates an intra prediction reference line for intra predicting the current block, and wherein an indication, other than the multiple reference line index value syntax element, indicating the angle refinement value is absent from the encoded bitstream.

3. The method of claim 2, wherein decoding the current block includes decoding the multiple reference line index value syntax element from the encoded bitstream using a current multiple reference line index value coding context from a plurality of available multiple reference line index value coding contexts.

4. The method of claim 3, wherein decoding the current block includes: obtaining the current multiple reference line index value coding context from the plurality of available multiple reference line index value coding contexts.

5. The method of claim 4, wherein obtaining the current multiple reference line index value coding context includes: determining whether a first multiple reference line index value for a first previously coded neighboring block is greater than zero; and determining whether a second multiple reference line index value for a second previously coded neighboring block is greater than zero.

6. The method of claim 5, wherein obtaining the current multiple reference line index value coding context includes: using a first multiple reference line index value coding context as the current multiple reference line index value coding context in response to determining that: the first multiple reference line index value is less than or equal to zero; and the second multiple reference line index value is less than or equal to zero.

7. The method of claim 5, wherein obtaining the current multiple reference line index value coding context includes: using a second multiple reference line index value coding context as the current multiple reference line index value coding context in response to determining that: the first multiple reference line index value is less than or equal to zero; and the second multiple reference line index value is greater than zero.

8. The method of claim 5, wherein obtaining the current multiple reference line index value coding context includes: using a third multiple reference line index value coding context as the current multiple reference line index value coding context in response to determining that: the first multiple reference line index value is greater than zero; and the second multiple reference line index value is greater than zero.

9. The method of claim 1, wherein: the angle mode value is from a defined set of available angle modes.

10. The method of claim 9, wherein: the defined set of available angle modes includes a forty-five degree angle mode, a sixty- seven degree angle mode, a ninety degree angle mode, a one hundred thirteen degree angle mode, a one hundred thirty-five degree angle mode, a one hundred fifty- seven degree angle mode, a one hundred eighty degree angle mode, and a two hundred three degree angle mode.

11. The method of claim 1, wherein: the angle delta value is from a defined set of available angle delta values.

12. The method of claim 11, wherein: the defined set of available angle delta values includes a negative nine degree angle delta value, a negative six degree angle delta value, a negative three degree angle delta value, a zero degree angle delta value, a three degree angle delta value, a six degree angle delta value, and a nine degree angle delta value.

13. The method of claim 1, wherein: the angle refinement value is from a defined set of available angle refinement values.

14. The method of claim 13, wherein: the defined set of available angle refinement values includes a negative one degree angle refinement value, a zero degree angle refinement value, and a one degree angle refinement value.

15. A non-transitory computer-readable storage medium having stored thereon an encoded bitstream comprising: encoded block data including: an encoded angle mode value; an encoded angle delta value; and an encoded syntax element representing a multiple reference line index value and indicating an angle refinement value.

16. A method comprising: generating encoded block data by encoding a current block of a current frame, wherein encoding the current block includes: obtaining an intra prediction angle value for encoding the current block, wherein obtaining the intra prediction angle value includes obtaining a multiple reference line index value; obtaining an angle mode value, an angle delta value, and an angle refinement value, wherein the intra prediction angle value is a sum of the angle mode value, the angle delta value, and the angle refinement value; obtain intra prediction block data in accordance with the intra prediction angle value; including the angle mode value in the encoded block data; including the angle delta value in the encoded block data; and including the multiple reference line index value in the encoded block data; including the encoded block data in an encoded bitstream; and outputting the encoded bitstream.

17. The method of claim 16, wherein: on a condition that a first coding cost for encoding the current block with reference to a first intra prediction reference line immediately adjacent to the current block is less than a second coding cost for encoding the current block with reference to a second intra prediction reference line immediately adjacent to the first intra prediction reference line: obtaining the multiple reference line index value includes obtaining, as the multiple reference line index value, a multiple reference line index value corresponding to a minimal cost value among the first coding cost, the second coding cost, a third coding cost for encoding the current block with reference to a third intra prediction reference line immediately adjacent to the second intra prediction reference line, and a fourth coding cost for encoding the current block with reference to a fourth intra prediction reference line immediately adjacent to the third intra prediction reference line.

18. The method of claim 16, wherein encoding the current block includes: obtaining a current multiple reference line index value coding context from a plurality of available multiple reference line index value coding contexts, wherein obtaining the current multiple reference line index value coding context includes: determining whether a first multiple reference line index value for a first previously coded neighboring block is greater than zero; and determining whether a second multiple reference line index value for a second previously coded neighboring block is greater than zero; and encoding a multiple reference line index value syntax element representing the multiple reference line index value using the current multiple reference line index value coding context.

19. The method of claim 18, wherein obtaining the current multiple reference line index value coding context includes: using a second multiple reference line index value coding context as the current multiple reference line index value coding context in response to determining that: the first multiple reference line index value is less than or equal to zero; and the second multiple reference line index value is greater than zero.

20. The method of claim 18, wherein obtaining the current multiple reference line index value coding context includes: using a third multiple reference line index value coding context as the current multiple reference line index value coding context in response to determining that: the first multiple reference line index value is greater than zero; and the second multiple reference line index value is greater than zero.