Joint coding of motion vector differences

Abstract

Coding using joint coding of motion vector differences includes encoding a motion vector difference by encoding a motion vector precision value for the motion vector difference, obtaining a scaled motion vector difference in accordance with the motion vector precision value and the motion vector difference, determining a shell index value, encoding the shell index value, encoding a sign of the motion vector difference vertical component value, in response to a determination that the shell index value is other than zero, encoding the scaled motion vector difference horizontal component value, and, in response to a determination that an unsigned motion vector difference horizontal component value is greater than zero, encoding a sign of the motion vector difference horizontal component value, including the encoded block data in an encoded bitstream, and outputting the encoded bitstream.

Description

JOINT CODING OF MOTION VECTOR DIFFERENCESCROSS-REFERENCE TO RELATED APPLICATION^ )

[0001] This application claims priority to and the benefit of U.S. Provisional Application Patent Serial No. 63 / 549,829, filed February 05, 2024, 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 joint coding of motion vector differences and aspects of systems, methods, and apparatuses for encoding and decoding using framewise advanced motion vector difference coding.

[0004] Variations in these and other aspects will be described in additional detail hereafter.

[0005] An aspect is a method for encoding using joint coding of motion vector differences.Encoding using joint coding of motion vector differences may include generating reconstructed block data by decoding a current block from a current frame from an encoded bitstream. Decoding the current block may include obtaining a motion vector for decoding the current block by obtaining a shell index value by decoding encoded shell index data from the encoded bitstream, obtaining an unsigned motion vector difference horizontal component value by decoding encoded unsigned motion vector difference horizontal component value data from the encoded bitstream, obtaining, as an unsigned motion vector difference vertical component value, a result of subtracting the unsigned motion vector difference horizontalcomponent value from the shell index value, in response to a determination that the unsigned motion vector difference vertical component value is greater than zero, obtaining a motion vector difference vertical component sign by decoding encoded motion vector difference vertical component sign data from the encoded bitstream, in response to a determination that the unsigned motion vector difference horizontal component value is greater than zero, obtaining a motion vector difference horizontal component sign by decoding encoded motion vector difference horizontal component sign data from the encoded bitstream, and obtaining, as the motion vector, a sum of the motion vector difference and a predicted motion vector for the current block. The method may include including the reconstructed block data in a reconstructed frame; and outputting the reconstructed frame.

[0006] Another aspect is an apparatus for encoding using joint coding of motion vector differences, the apparatus comprising a memory including computer executable instructions for encoding an input video stream, and a processor that executes the instructions to perform the method for encoding using joint coding of motion vector differences.

[0007] Another aspect is a non-transitory computer-readable storage medium having stored thereon an encoded bitstream, the encoded bitstream comprising encoded shell index data indicating a shell index value for obtaining a motion vector difference for obtaining a motion vector for decoding a current block from a current frame, encoded unsigned motion vector difference horizontal component value data indicating an unsigned motion vector difference horizontal component value for obtaining the motion vector, encoded motion vector difference horizontal component sign data indicating a motion vector difference horizontal component sign, wherein a combination of the motion vector difference horizontal component sign and the unsigned motion vector difference horizontal component value is a motion vector difference horizontal component value of a motion vector difference for obtaining the motion vector, and encoded motion vector difference vertical component sign data indicating a motion vector difference vertical component sign, wherein a combination of the motion vector difference vertical component sign and a result of subtracting the unsigned motion vector difference horizontal component value from the shell index value is a motion vector difference vertical component value of the motion vector difference.

[0008] Another aspect is a method for decoding using joint coding of motion vector differences. Decoding using joint coding of motion vector differences may include generating encoded block data by encoding a current block from a current frame from an input video stream. Encoding the current block may include obtaining a motion vector difference by subtracting a predicted motion vector from a motion vector used to encode the current block,wherein the motion vector difference includes a motion vector difference vertical component value and a motion vector difference horizontal component value; and obtaining encoded motion vector difference data by encoding the motion vector difference. Encoding the motion vector difference may include obtaining a scaled motion vector difference in accordance with a motion vector precision value for the motion vector difference and the motion vector difference, wherein obtaining the scaled motion vector difference includes obtaining a scaled motion vector difference vertical component value and a scaled motion vector difference horizontal component value, determining, as a shell index value, a sum of an absolute value of the scaled motion vector difference horizontal component value and an absolute value of the scaled motion vector difference vertical component value, obtaining encoded shell index data by encoding the shell index value, obtaining encoded unsigned motion vector difference horizontal component value data by encoding an unsigned motion vector difference horizontal component value, in response to a determination that an unsigned motion vector difference vertical component value is greater than zero, encoding a sign of the motion vector difference vertical component value, and in response to a determination that the unsigned motion vector difference horizontal component value is greater than zero, encoding a sign of the motion vector difference horizontal component value. The method may include including the encoded block data in an encoded bitstream and outputting the encoded bitstream.

[0009] Another aspect is an apparatus for decoding using joint coding of motion vector differences, the apparatus comprising a memory including computer executable instructions for decoding an encoded video stream, and a processor that executes the instructions to perform the method of decoding using joint coding of motion vector differences.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 thisdisclosure.

[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 flowchart diagram of an example of encoding using joint coding of motion vector differences in accordance with implementations of this disclosure.

[0018] FIG. 8 is a block diagram of an example of shell indices.

[0019] FIG. 9 is a flowchart diagram of an example of decoding using joint coding of motion vector differences in accordance with implementations of this disclosure.

[0020] FIG. 10 is a flowchart diagram of an example of encoding using frame-wise advanced motion vector difference coding in accordance with implementations of this disclosure.

[0021] FIG. 11 is a flowchart diagram of an example of decoding using the frame-wise advanced motion vector difference coding mode in accordance with implementations of this disclosure.DETAILED DESCRIPTION

[0022] 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 someimplementations, the accuracy, efficiency, or both, of coding a block using either interprediction or intra-prediction may be limited.

[0023] 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.

[0024] 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.

[0025] 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.

[0026] 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.

[0027] The data 112 can include information, such as input audio data, encoded audiodata, 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.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] The electronic communication unit 140 can transmit, receive, or transmit andreceive 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.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] Although shown as separate units, the electronic communication unit 140, the electronic communication interface 142, the user interface 130, the power source 160, orportions 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.

[0036] 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.

[0037] 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.

[0038] 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.

[0039] 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.

[0040] 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, thecomputing 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.

[0041] 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.

[0042] 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.

[0043] 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 acommunication 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.

[0044] 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 210B 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.

[0045] 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.

[0046] 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 andcan 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.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] 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 transformunit 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.

[0051] 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.

[0052] 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.

[0053] 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., direct current (DC)) coefficient at the top-left of the matrix and the highest frequency coefficient at the bottom-right of the matrix.

[0054] 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 bitstream404 can be formatted using various techniques, such as run-length encoding (RLE) and zerorun coding.

[0055] 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.

[0056] 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.

[0057] 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.

[0058] The decoder 500 may receive a compressed bitstream 502, such as the compressedbitstream 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.

[0059] 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.

[0060] 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 570.

[0061] 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 twochrominance 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.

[0062] 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.

[0063] 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 becoded 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.

[0064] 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.

[0065] 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.

[0066] 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.

[0067] 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.

[0068] In some implementations, reducing temporal redundancy may include identifying aportion 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.

[0069] 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 / (. y. Similarly, a pixel of the search area of the reference frame may be indicated based on location using Cartesian coordinates as rx, 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.

[0070] 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 thetop left corner of a rendering of the frame as an image.

[0071] 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.

[0072] 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.

[0073] 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-distortioncost, 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.

[0074] 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.

[0075] 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.

[0076] 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 basedon 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.

[0077] FIG. 7 is a flowchart diagram of an example of encoding using joint coding of motion vector differences 700 in accordance with implementations of this disclosure. Encoding using joint coding of motion vector differences 700 may be implemented in an encoder, such as the encoder 400 shown in FIG. 4.

[0078] Encoding using joint coding of motion vector differences 700 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. 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.

[0079] Encoding using joint coding of motion vector differences 700 includes obtaining a current block (at 710), obtaining motion vector difference data (at 720), obtaining encoded motion vector difference data (at 725), and outputting the encoded bitstream (at 730).

[0080] A current block is obtained (at 710). Obtaining the current block (at 710) includes obtaining a current frame and obtaining the current block from the current frame), such as in accordance with a block-coding order. The current frame is a frame from the input video, or input video stream. In some implementations, the input video stream may include one or more sequences of frames. A sequence of frames may have a defined cardinality, or number, of 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, may obtain the input video stream. The current frame may be obtained (at 710) 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.

[0081] Although not shown expressly in FIG. 7, encoding using joint coding of motion vector differences 700 includes other aspects of video coding for encoding the current block. For example, encoding using joint coding of motion vector differences 700 includes obtaining, or determining, a prediction coding mode, such as an inter prediction coding mode, which includes obtaining, such as prior to coding the current block, a set, list, or array, ofcandidate, or reference, motion vectors (ref_mvs), such as from one or more context blocks for coding the current block, such as neighboring previously coded blocks, collocated previously coded blocks, or a combination thereof, which may be referred to as a dynamic reference list (DRL). In another example, encoding using joint coding of motion vector differences 700 includes obtaining a predicted motion vector, which is an optimal candidate, or reference, motion vector, for the current block, from the dynamic reference list, obtaining a motion vector for the current block, obtaining encoded block data by encoding the current block using the motion vector, and including the encoded block data in an encoded, or output, bitstream. The predicted motion vector includes a horizontal (x or column) component (ref_mv.col) and a vertical (y or row) component ref_mv. row), which may be expressed using relative Cartesian coordinates. The motion vector includes a horizontal (x) component (mv.col) and a vertical (y) component (mv.row), which may be expressed using relative Cartesian coordinates.

[0082] Motion vector difference data is obtained (at 720). Obtaining the motion vector difference data includes obtaining a motion vector difference, or differential motion vector, by subtracting the predicted motion vector from the motion vector used to encode the current block.

[0083] The motion vector difference (MVD) includes a horizontal (x or column) component (MVD. col) and a vertical (y or row) component (MVD. row), which may be expressed using relative Cartesian coordinates. Obtaining the horizontal (x or column) component (MVD. co I) of the motion vector difference may be expressed as MVD. col = mv.col - ref_mv.col. Obtaining the vertical (y or row) component (MVD. row) of the motion vector difference may be expressed as MVD. row = mv.row - ref_mv.row.

[0084] The motion vector difference (MVD) may be coded using a motion vector precision from a defined set of available precisions, such as one eighth (1 / 8) of a pixel, one quarter (1 / 4) of a pixel, one half (1 / 2) of a pixel, one (1) pixel, two (2) pixels, four (4) pixels, or eight (8) pixels. The motion vector precision may be indicated by a motion vector precision value (pb_mv -precision) as shown in Table 1.[Table 1]

[0085] Encoded motion vector difference data is obtained (at 725) by encoding the motion vector difference.

[0086] In some implementations, obtaining the encoded motion vector difference data may include obtaining encoded motion vector precision value data by encoding the motion vector precision value.

[0087] In some encoders, obtaining the encoded motion vector difference data may include encoding a joint quaternary symbol (mv Joint) for the motion vector difference. In some implementations, the vertical component (MVD.row) of the motion vector difference is zero, the horizontal component (MV D. col) of the motion vector difference is zero, and the joint quaternary symbol is zero (0). In some implementations, the vertical component (MVD.row) of the motion vector difference is zero, the horizontal component (MV D. col) of the motion vector difference is non-zero, and the joint quaternary symbol is one (1). In some implementations, the vertical component (MVD.row) of the motion vector difference is nonzero, the horizontal component (MV D. col) of the motion vector difference is zero, and the joint quaternary symbol is two (2). In some implementations, the vertical component (MVD.row) of the motion vector difference is non-zero, the horizontal component (MVD.col) of the motion vector difference is non-zero, and the joint quaternary symbol is three (3). The vertical component (MVD.row) of the motion vector difference may be non-zero and the sign (mv_sigr) of the vertical component (MVD.row) of the motion vector difference is non-zero is encoded, a motion vector class value (mv_class) for the motion vector difference is encoded, and a shell offset value is encoded. The motion vector class value (mv_class) indicates a class of the motion vector difference, wherein a relatively high motion vector class value indicates that the motion vector difference is relatively large. The motion vector class value (mv_class) categorizes the motion vector difference into a defined set of classes, respectively representing a corresponding range of motion vector difference values. For example, the motion vector class may be from a defined set of motion vector classes, such as eleven motion vector classes. The shell offset value is a difference between an integer pixel motion vector difference and a base value of the associated motion vector class.

[0088] In an encoder implementing encoding using joint coding of motion vectordifferences 700, obtaining the encoded motion vector difference data (at 725) includes obtaining an encoded motion vector precision value (at 740), obtaining a scaled motion vector difference (at 750), obtaining an encoded shell index value (at 760), determining whether the shell index value is other than zero (at 770), obtaining an encoded scaled motion vector difference horizontal component value (at 780), and obtaining encoded signs (at 790).

[0089] Obtaining the encoded motion vector precision data (at 740) includes obtaining the motion vector precision value (pb_mv jirecision) for the motion vector difference (MVD) and encoding the motion vector precision value (pb_mv jirecision).

[0090] Obtaining the scaled motion vector difference (at 750) includes obtaining the scaled motion vector difference in accordance with the motion vector precision value and the motion vector difference.

[0091] Obtaining the scaled motion vector difference includes obtaining a scaled motion vector difference horizontal component value. Obtaining the scaled motion vector difference horizontal component value includes obtaining, as the scaled motion vector difference horizontal component value (scaledMVD.cobb a result of right bit-shifting (») the absolute value of the motion vector difference horizontal component value (\MVD.col\, abs(MVD.col), or an unsigned motion vector difference horizontal component value) by a result of subtracting the motion vector precision value (pb_mv jirecision) from the maximum motion vector precision value, six (6), which may be expressed as the following: scaledMVD.col = abs(MVD.col) » (6 - pb_mv_precision).

[0092] Obtaining the scaled motion vector difference includes obtaining a scaled motion vector difference vertical component value. Obtaining the scaled motion vector difference vertical component value includes obtaining, as the scaled motion vector difference vertical component value (scaledMVD.rowb a result of right bit-shifting (») the absolute value of the motion vector difference vertical component value (\MVD.row\, abs(MVD.row), or an unsigned motion vector difference vertical component value) by a result of subtracting the motion vector precision value (pb_mv jirecision) from the maximum motion vector precision value, six (6), which may be expressed as the following: scaledMVD.row = abs(MVD.row) » (6 - pb_mv_precision).

[0093] Obtaining the encoded shell index value (at 760) includes determining a shell index value (shell_index, n, or shell index data).

[0094] Determining the shell index value includes obtaining, as the shell index value, a sum of an absolute value of the scaled motion vector difference horizontal component value and an absolute value of the scaled motion vector difference vertical component value, whichmay be expressed as the following: shelljndex = \scaledMVD.row\ + \scaledMVD.col\.

[0095] Obtaining the encoded shell index value includes obtaining encoded shell index data by encoding the shell index value.

[0096] In some implementations, encoding the shell index value (n) includes encoding the shell index value (n) using Rice-Golomb coding or exponential Golomb coding.

[0097] In some implementations, encoding the shell index value (n) includes encoding the shell index value (n) using class based arithmetic coding. Class based arithmetic coding of the shell index value includes representing the shell index value using two symbols, including a shell class symbol (encoded shell class data) and a shell offset symbol (encoded shell offset data).

[0098] For example, class based arithmetic coding of the shell index value may include obtaining a shell class value (shell_class) corresponding to the shell index value from defined shell class to shell index range mapping data, as shown in Table 2.[Table 2]

[0099] For example, a shell index value, such as five (5), in the range from four to seven, inclusive, ([4, 7]) corresponds to the shell class value two (2). In another example, a shellindex value, such as twenty-one (5), in the range from sixteen to thirty-one, inclusive, ([16, 31]) corresponds to the shell class value four (4). The shell class symbol is obtained by arithmetic coding the shell class value. The context for arithmetic coding the shell class value may be derived from the shell class value. In some implementations, the context for arithmetic coding the shell class value may be derived from the motion vector precision value, which may be expressed as ctx_idx = pb_mv precision. Table 2 shows shell class to shell index range mapping data for one eighth pixel precision, other values for other precisions may be used.

[0100] Class based arithmetic coding of the shell index value may include obtaining, as a shell offset value shell _off set), a result of subtracting a shell class base index value {shell_class_base_index) corresponding to the shell index value, as shown in Table 2, from the shell index value, which may be expressed as the following shell_offset = shell_index - shell _class_base_index. The shell class base index value is a minimal value of the shell index range of values represented by the shell class. The shell offset symbol is obtained by arithmetic coding the shell offset value. The context for arithmetic coding the shell offset value may be derived from the shell class value.

[0101] In some implementations, obtaining the shell class value may omit using the defined shell class to shell index range mapping data. In implementations that omit using the defined shell class to shell index range mapping data, for shell index values that are less than two, obtaining the shell class value may include obtaining zero as the shell class value. In implementations that omit using the defined shell class to shell index range mapping data, for shell index values that are greater than or equal to two, obtaining the shell class value includes obtaining, as the shell class value, a binary logarithm of the shell index value. In implementations that omit using the defined shell class to shell index range mapping data, wherein the shell class value is zero, class based arithmetic coding of the shell index value may include obtaining zero as the shell class base index value. In implementations that omit using the defined shell class to shell index range mapping data, wherein the shell class value is other than zero, class based arithmetic coding of the shell index value may include obtaining, as the shell class base index value, a result of left bit-shifting one (1) by the shell class value, which may be expressed as shell_class_base_index = (1 « (shell_class)).

[0102] In some implementations, the shell class value may be less than two (2) and a, such as one, binary symbol (encoded shell offset value data) may be used to code the shell offset value. A context for arithmetic coding the shell offset value may be obtained, identified, or derived in accordance with the shell class value, which may be expressed as ctx_idx =shell_class.

[0103] In some implementations, the shell class value may be two (2), truncated unary coding may be used for binarization, to obtain bin data, as shown in Table 3, wherein the bin data includes one or more binary values corresponding to respective bin index values, and respective bins indicated by the bin data may be context coded, such as on a per-bin basis, wherein the context is obtained, identified, or derived in accordance with a corresponding bin index value, which may be expressed as ctx_idx = bin ndex.[Table 3]

[0104] In some implementations, the shell class value may be greater than two (2) and bits of the shell offset value, such as on a per-bit basis from the least significant bit to the most significant bit, may be context coded, wherein a respective bit position is associated with a corresponding context. Coding the bits of the shell offset value may include identifying, calculating, or determining, as a number, count, or cardinality of bits for the shell offset value, the shell class value. Coding the bits of the shell offset value on a per-bit basis may include iterating through the bits by bit position, wherein a coding context is identified for a respective bit position (i) and the corresponding bit (shell_offset » i) is encoded using the coding context, which may be expressed as the following: const int num_of_bits_for_this_offset = shell_class; for (inti = 0; i < num_of_bits_for_this_offset; ++i) ctxjdx = i;Encode (shell_cls_offset » i) & 1 with context ctxjdx.

[0105] In some implementations, determining whether the shell index value is other than zero (at 770) includes determining that the shell index value is zero, and obtaining the encoded scaled motion vector difference horizontal component value (at 780) and obtaining encoded signs (at 790) are omitted for the current block, as indicated by the directional line labeled “NO” from determining whether the shell index (n) is other than zero (at 770) to outputting the encoded bitstream (at 730).

[0106] In some implementations, determining whether the shell index value is other than zero (at 770) includes determining that the shell index value is other than zero, as indicatedby the directional line labeled “YES” from determining whether the shell index (n) is other than zero (at 770) to obtaining the encoded scaled motion vector difference horizontal component value (at 780).

[0107] The encoded scaled motion vector difference horizontal component value is obtained (at 780), such as in response to determining that the shell index value is other than zero (at 770). The scaled motion vector difference horizontal component value (scaledMVD.col) is in a range from zero (0) to the shell index value ([0, shell _index]). The scaled motion vector difference horizontal component value (scaledMVD.col) may be coded using quasi-uniform coding with an alphabet size that is a sum of one and the shell index value (1 + shell_index).

[0108] The scaled motion vector difference horizontal component value (scaledMVD.col) may be relatively close to zero, which corresponds with vertical motion vector differences. The scaled motion vector difference horizontal component value (scaledMVD.col) may be relatively close to the shell index value, which corresponds with horizontal motion vector differences. The scaled motion vector difference horizontal component value (scaledMVD.col) may be coded using adaptive entropy coding. Coding the scaled motion vector difference horizontal component value (scaledMVD.col) using adaptive entropy coding may include dividing the range [0, shell_index\ for the scaled motion vector difference horizontal component value (scaledMVD.col) into a defined cardinality ( / ?) of range classes, and using an adaptive entropy coder to code a range class for the scaled motion vector difference horizontal component value (scaledMVD.col) and coding a quasi-uniform code indicating the relative value of the scaled motion vector difference horizontal component value (scaledMVD.col) within the range class.

[0109] In some implementations, the shell class value is relatively low and the scaled motion vector difference horizontal component value (scaledMVD.col) may be coded using arithmetic coding, in view of the relatively small range.

[0110] In some implementations, obtaining the encoded scaled motion vector difference horizontal component value (at 780) is omitted, skipped, or excluded and encoded unsigned motion vector difference horizontal component value (\MVD.col\) data is obtained (at 780). The unsigned motion vector difference horizontal component value (\MVD.col\) is in the range from zero to the shell index value ([0, shell _index]). The unsigned motion vector difference horizontal component value (\MVD.col\) may be relatively close to zero, which corresponds with vertical motion vector differences. The unsigned motion vector difference horizontal component value (\MVD.col\) may be relatively close to the shell index value,- l-which corresponds with horizontal motion vector differences.

[0111] Obtaining the encoded unsigned motion vector difference horizontal component value data (at 780) includes obtaining a motion vector difference horizontal component pair index value (mvd_col _j)air_index). Obtaining the motion vector difference horizontal component pair index value (mvd_col _j)air_index) may include obtaining, as a maximum motion vector difference horizontal component pair index value (max_mvd_col _j)air_index), a result of right bit-shifting the shell index value shell _index') by one (shell_index >> 1). Obtaining the motion vector difference horizontal component pair index value (mvd_col jiair _index) may include determining whether the unsigned motion vector difference horizontal component value (\MVD.col\) is less than or equal to the maximum motion vector difference horizontal component pair index value (max_mvd_col _pair_index).

[0112] In response to determining that the unsigned motion vector difference horizontal component value (\MVD.col\) is less than or equal to the maximum motion vector difference horizontal component pair index value (max_mvd_col _pair_index), obtaining the motion vector difference horizontal component pair index value (mvd_col _pair_index) includes obtaining, as the motion vector difference horizontal component pair index value (mvd_col _pair _index) , the unsigned motion vector difference horizontal component value (\MVD.col\).

[0113] In response to determining that the unsigned motion vector difference horizontal component value (\MVD.col\) is greater than the maximum motion vector difference horizontal component pair index value (max_mvd_col _pair_index), obtaining the motion vector difference horizontal component pair index value (mvd_col _pair_index) includes obtaining, as the motion vector difference horizontal component pair index value (mvd_col _pair _index) , a result of subtracting the unsigned motion vector difference horizontal component value (\MVD.col\) from the shell index value (shell_index - \MVD.col\).

[0114] Obtaining the encoded unsigned motion vector difference horizontal component value (\MVD.col\) data (at 780) includes signaling, such as by including in the encoded bitstream, encoded data indicating a greater than zero (greaterJJ) bit, flag, or other syntax element (greater than zero flag value) to indicate whether the motion vector difference horizontal component pair index value (mvd_col _pair_index) is greater than zero, such as using a, such as one, corresponding entropy coding context.

[0115] Obtaining the encoded unsigned motion vector difference horizontal component value (\MVD.col\) data (at 780) includes, wherein the greater than zero (greaterJJ) flag indicates that the motion vector difference horizontal component pair index value(mvd_col _pair_index) is greater than zero (grealer ) == 1), signaling, such as by including in the encoded bitstream, a greater than one greater _1) bit, flag, or other syntax element (greater than one flag value) to indicate whether the motion vector difference horizontal component pair index value (mvd_col jiairjndexj greater than one, such as using a, such as one, corresponding entropy coding context.

[0116] Obtaining the encoded unsigned motion vector difference horizontal component value (\MVD.col\) data (at 780) includes, wherein the greater than one (greater J) flag indicates that the motion vector difference horizontal component pair index value (mvd_col jiairjndexj than one and a maximum offset value (max_offset_value) is greater than two (grealer == 1 && max_offset_value > 2), signaling, such as by including in the encoded bitstream, a result of subtracting two (2) from the motion vector difference horizontal component pair index value (mvd_col _pair_index) (mvd_col _pair_index - 2), such as using quasi-uniform coding.

[0117] Obtaining the encoded unsigned motion vector difference horizontal component value (\MVD.col\) data (at 780) includes signaling, such as by including in the encoded bitstream, a bit, flag, or other syntax element to indicate whether the unsigned motion vector difference horizontal component value (\MVD.col\) is greater than the maximum motion vector difference horizontal component pair index value (\MVD.col\ > max_mvd_col _pair_index), such as using an entropy coding context (ctxjdx) identified, derived, or selected, from four available entropy coding contexts, or cumulative distribution functions, in accordance with the shell class value (shell _class), such as by determining a minimum value among the shell class value (shell _clas s') and three (3), which may be expressed as ctxjdx = min (shell_class, 3).

[0118] Obtaining the encoded signs (at 790) includes determining whether the unsigned motion vector difference vertical component value (\MVD.row\) is greater than zero.

[0119] In some implementations, determining whether the unsigned motion vector difference vertical component value (\MVD.row\) is greater than zero includes determining that the unsigned motion vector difference vertical component value (\MVD.row\) is greater than zero (abJMVD.row) > 0). Obtaining the encoded signs (at 790) includes, in response to determining that that unsigned motion vector difference vertical component value is greater than zero, encoding the sign of the motion vector difference vertical component value.

[0120] Obtaining the encoded signs (at 790) includes determining whether the unsigned motion vector difference horizontal component value (MVD.col) is greater than zero.

[0121] In some implementations, determining whether the unsigned motion vectordifference horizontal component value (MVD.col) is greater than zero includes determining that the unsigned motion vector difference horizontal component value (MVD.col) is greater than zero (abs(Af VD.col) > 0). Obtaining the encoded signs (at 790) includes, in response to determining that that unsigned motion vector difference horizontal component value is greater than zero, encoding the sign of the motion vector difference horizontal component value.

[0122] In some implementations, encoding using joint coding of motion vector differences 700 may include deriving a maximum value of the shell class from the motion vector precision value. For relatively high motion vector difference values, relatively high motion vector precisions, such as one eighth (1 / 8) or one fourth (1 / 4), are unlikely. For relatively low motion vector difference values, relatively high motion vector precisions, such as four or eight, are unlikely. The resource utilization, or signaling overhead, for signaling the shell class value may be reduced by omitting, skipping, or excluding using some shell class values for some motion vector precisions. For example, the motion vector precision may be one eighth (1 / 8) pixel and the shell class value may be limited to within the range from zero to four, inclusive, ([0, 4]). In another example, the motion vector precision may be one fourth (1 / 4) pixel and the shell class value may be limited to within the range from zero to five, inclusive, ([0, 5]).

[0123] Although encoding using joint coding of motion vector differences 700 is described with respect to using one motion vector for the current block, in some implementations, encoding using joint coding of motion vector differences 700 may include coding the current block using compound prediction, or bi-prediction, wherein the current block is encoded using a first motion vector and a second motion vector, as is otherwise described herein.

[0124] Outputting the encoded bitstream (at 730) includes including the encoded motion vector precision data, the encoded shell index value, the scaled motion vector difference horizontal component value , the sign of the motion vector difference vertical component value, the sign of the motion vector difference horizontal component value, or a combination thereof, in the encoded block data for the current block, and including the encoded block data for the current block in the encoded bitstream.

[0125] A broken directional line between output (at 730) and obtaining the current block (at 710) is shown to indicate that obtaining a current block (at 710), obtaining a motion vector difference (at 720), obtaining encoded motion vector difference data (at 725), and outputting (at 730), or a combination thereof, may be performed on a per-block basis for the currentframe.

[0126] In an example, an apparatus may include a non-transitory computer readable medium and a processor configured to execute instructions stored on the non-transitory computer readable medium to generate reconstructed block data, wherein, to generate the reconstructed block data, the processor executes the instructions to decode a current block from a current frame from an encoded bitstream, wherein, to decode the current block, the processor is configured to execute the instructions to obtain a motion vector, wherein, to obtain the motion vector, the processor is configured to execute the instructions to obtain a shell index value, wherein, to obtain the shell index value, the processor is configured to execute the instructions to decode encoded shell index data from the encoded bitstream; obtain an unsigned motion vector difference horizontal component value, wherein, to obtain the unsigned motion vector difference horizontal component value, the processor is configured to execute the instructions to decode encoded unsigned motion vector difference horizontal component value data from the encoded bitstream; obtain, as an unsigned motion vector difference vertical component value, a result of a subtraction of the unsigned motion vector difference horizontal component value from the shell index value; in response to a determination that the unsigned motion vector difference vertical component value is greater than zero, obtain a motion vector difference vertical component sign, wherein, to obtain the motion vector difference vertical component sign, the processor is configured to execute the instructions to decode encoded motion vector difference vertical component sign data from the encoded bitstream; in response to a determination that the unsigned motion vector difference horizontal component value is greater than zero, obtain a motion vector difference horizontal component sign, wherein, to obtain the motion vector difference horizontal component sign, the processor is configured to decode encoded motion vector difference horizontal component sign data from the encoded bitstream; and obtain, as the motion vector, a sum of the motion vector difference and a predicted motion vector for the current block; wherein the processor is configured to execute the instructions to include the reconstructed block data in a reconstructed frame; and output the reconstructed frame.

[0127] FIG. 8 is a block diagram of an example of shell indices 800, such as for encoding using joint coding of motion vector differences, such as the encoding using joint coding of motion vector differences 700 shown in FIG. 7 or the decoding using joint coding of motion vector differences 900 shown in FIG. 9.

[0128] The vector space of the absolute value of the motion vector difference may beorganized, represented, or expressed, as successive concentric shells Snindexed by a shell distance parameter n. A respective integer motion vector difference corresponds to a respective shell index value (n), such that a sum of the absolute value of the horizontal component (ABS(AZVD.COL) or I MVD.CC)L\) and the absolute value of the vertical component (ABS(A / VD.7?0W) or I MVD.ROW) is equal to the shell index value (n), which may be expressed as the following: n = | M D.ROW\ + | MVD.COL | .

[0129] FIG. 8 shows a first shell 810 having a shell index value of one (n=l), a second shell 820 having a shell index value of two (n=2), a third shell 830 having a shell index value of three (n=3), a fourth shell 840 having a shell index value of four (n=4), a fifth shell 850 having a shell index value of five (n=5), a sixth shell 860 having a shell index value of six (n=6), a seventh shell 870 having a shell index value of seven (n=7), and an eighth shell 880 having a shell index value of eight (n=8). Although eight shells are shown for simplicity, other numbers, or cardinalities, of shells may be used.

[0130] FIG. 9 is a flowchart diagram of an example of decoding using joint coding of motion vector differences 900 in accordance with implementations of this disclosure. Decoding using joint coding of motion vector differences 900 may be implemented in a decoder, such as the decoder 500 shown in FIG. 5.

[0131] Decoding using joint coding of motion vector differences 900 includes 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.

[0132] Decoding using joint coding of motion vector differences 900 includes obtaining the encoded bitstream (at 910), obtaining a motion vector difference (MVD) for decoding the current block (at 920), and outputting an output video stream (at 930).

[0133] The encoded bitstream is obtained (at 910). Obtaining the encoded bitstream includes identifying a current frame to decode from the encoded bitstream to generate a current reconstructed frame, which includes identifying a current block from the current frame to decode from the encoded bitstream to generate a current reconstructed block (reconstructed block data) to include in the current reconstructed frame. For example, the decoder, or a component thereof, such as an intra / inter prediction unit of the decoder, such as the entropy decoding unit 510 shown in FIG. 5, may obtain the input video stream. The current frame may be obtained (at 910) subsequent to decoding one or more other frames,such as a frame sequentially preceding the current frame, 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 decoding the current frame. Although not shown separately in FIG. 9, decoding using joint coding of motion vector differences 900 may include decoding, reconstructing, or both, one or more portions of the current frame prior to decoding, reconstructing, or both, the current block.

[0134] The motion vector difference (MVD), which is a decoded, or reconstructed, motion vector difference, for decoding the current block is obtained (at 920). Obtaining the motion vector difference for decoding the current block (at 920) includes obtaining a motion vector precision value (at 940), obtaining a shell index value (at 950), obtaining a scaled motion vector difference value (at 960), obtaining unsigned motion vector difference component values (at 970), and obtaining motion vector difference component signs (at 980).

[0135] Obtaining the motion vector precision value (at 940) includes obtaining the motion vector precision value {pb_mv _precisior) by decoding an encoded motion vector precision value from the encoded bitstream.

[0136] In some implementations, obtaining the shell index value (at 950) includes decoding an encoded shell index value (n) from the encoded bitstream using Rice-Golomb coding or exponential Golomb coding.

[0137] In some implementations, obtaining the shell index value (at 950) includes decoding the encoded shell index value (n) from the encoded bitstream using class based arithmetic coding.

[0138] Decoding the encoded shell index value (n) from the encoded bitstream using using class based arithmetic coding may include obtaining a shell class value by decoding an encoded shell class value (encoded shell class data) from the encoded bitstream, such as by decoding a shell class symbol representing the shell class value using arithmetic coding.

[0139] Obtaining the shell index value using class based arithmetic coding may include obtaining a shell class base index value {shell _class_base_index) corresponding to the shell index value, as shown in Table 2, in accordance with the shell class value. Obtaining the shell class base index value {shell _class_base_index) may be similar to obtaining the shell class base index value {shell_class_base_index) as shown (at 760) in FIG. 7, except as is described herein or as is otherwise clear from context.

[0140] Obtaining the shell index value using class based arithmetic coding may include obtaining a shell offset value by decoding an encoded shell offset value (at 960) from the encoded bitstream, such as by decoding a shell offset symbol representing the shell offsetvalue using arithmetic coding.

[0141] In some implementations, obtaining the shell offset value includes determining whether the shell class value is less than two. In response to a determination that the shell class value is less than two, obtaining the shell offset value includes decoding encoded shell offset data using a coding context identified in accordance with the shell class value.

[0142] In response to a determination that the shell class value is two, obtaining the shell offset value includes decoding one or more bin values, wherein decoding a respective bin value from the one or more bin values includes identifying a cumulative distribution function for decoding the respective bin value in accordance with a bin index of the respective bin value, and obtaining the shell offset value by reconstructing the shell offset value using truncated unary coding in accordance with the bin values. In response to a determination that the shell class value is greater than two, obtaining the shell offset value includes decoding the shell offset value on a per-bit basis, wherein decoding the shell offset value on a per-bit basis includes decoding a respective bit of the shell offset value using a coding context corresponding to a bit position of the respective bit.

[0143] Obtaining the shell index value using class based arithmetic coding may include obtaining, as the shell index value, a sum of the shell offset value and the shell class base index value, which may be expressed as the following: shell_index = shell_offset + class_base_index.

[0144] In some implementations, obtaining the shell index value may include obtaining the shell index value by decoding encoded shell index data, such as encoded shell index data including the encoded shell class data, the encoded shell class data, or both.

[0145] Obtaining the scaled motion vector difference value (at 960) includes determining whether the shell index value is other than zero (shell_index <> 0).

[0146] Obtaining the scaled motion vector difference value (at 960) includes, in response to a determination that the shell index value is zero, obtaining zero as a scaled motion vector difference horizontal component value of the scaled motion vector difference value.

[0147] Obtaining the scaled motion vector difference value (at 960) includes, in response to a determination that the shell index value is zero, obtaining zero as a scaled motion vector difference vertical component value of the scaled motion vector difference value.

[0148] Obtaining the scaled motion vector difference value (at 960) includes, in response to a determination that the shell index value is other than, such as greater than or less than, zero, obtaining the scaled motion vector difference horizontal component value by decoding an encoded scaled motion vector difference horizontal component value from the encodedbitstream.

[0149] In some implementations, decoding the encoded scaled motion vector difference horizontal component value from the encoded bitstream may include using quasi-uniform coding.

[0150] In some implementations, decoding the encoded scaled motion vector difference horizontal component value from the encoded bitstream may include using adaptive entropy coding as described herein.

[0151] In some implementations, decoding the encoded scaled motion vector difference horizontal component value from the encoded bitstream may include using arithmetic coding as described herein.

[0152] Obtaining the scaled motion vector difference value (at 960) includes, in response to a determination that the shell index value is other than, such as greater than or less than, zero, obtaining, as the scaled motion vector difference vertical component value, a result of subtracting the scaled motion vector difference vertical component value from the shell index value.

[0153] Obtaining the unsigned motion vector difference component values (at 970), which are the absolute values of the motion vector difference component values, includes obtaining, as an unsigned motion vector difference horizontal component value, a result of left bitshifting («) the scaled motion vector difference horizontal component value (scaledMVD.col) by a result of subtracting the motion vector precision value(pb_mv jirecision) from the maximum motion vector precision value, such as six (6), which may be expressed as the following: abs MVD. col) = scaledMVD. col « (6- pb_mv_precision ).

[0154] Obtaining the unsigned motion vector difference component values (at 970) includes obtaining, as an unsigned motion vector difference vertical component value, a result of left bit- shifting («) the scaled motion vector difference vertical component value (scaledMVD.row) by a result of subtracting the motion vector precision value(pb_mv -precision) from the maximum motion vector precision value, such as six (6), which may be expressed as the following: abs(MVD.row) = scaledMVD.row « (6 - pb_mv_precision ).

[0155] In some implementations, decoding the encoded scaled motion vector difference horizontal component value (at 960) is omitted, skipped, or excluded, obtaining the unsigned motion vector difference component values (at 970) using the encoded scaled motion vector difference component values is omitted, skipped, or excluded, and obtaining the unsignedmotion vector difference component values (at 970) includes obtaining the unsigned motion vector difference horizontal component value (\MVD.col\) by decoding encoded unsigned motion vector difference horizontal component value (\MVD.col\) data (at 970).

[0156] Decoding the encoded unsigned motion vector difference horizontal component value (\MVD.col\) data (at 970) includes obtaining a motion vector difference horizontal component pair index value (mvd_col _pair_index).

[0157] Obtaining the motion vector difference horizontal component pair index value (mvd_col _pair_index) includes reading, extracting, decoding, or otherwise accessing, such as from the encoded bitstream, encoded greater than zero flag data indicating a greater than zero (grealer_0) bit, flag, or other syntax element indicating whether the motion vector difference horizontal component pair index value (mvd_col _pair _index) is greater than zero, such as using a, such as one, corresponding entropy coding context.

[0158] Obtaining the motion vector difference horizontal component pair index value (mvd_col _pair _index) includes, in response to a determination that the greater than zero (grealer_0) flag indicates that the motion vector difference horizontal component pair index value (mvd_col _pair _index) is less than or equal to zero (grealer_0 == 0, other than greater than zero), obtaining zero as the motion vector difference horizontal component pair index value mvd_col jjair -index).

[0159] Obtaining the motion vector difference horizontal component pair index value (mvd_col _pair _index) includes reading, extracting, decoding, or otherwise accessing, such as from the encoded bitstream, wherein, or in response to a determination that, the greater than zero (grealer_0) flag indicates that the motion vector difference horizontal component pair index value (mvd_col _pair _index) is greater than zero (greater _0 == 1), encoded greater than one flag data indicating a greater than one (greater _7) bit, flag, or other syntax element indicating whether the motion vector difference horizontal component pair index value (mvd_col _pair _index) is greater than one, such as using a, such as one, corresponding entropy coding context.

[0160] Obtaining the motion vector difference horizontal component pair index value (mvd_col _pair _index) includes, in response to a determination that the greater than one (greater _7) flag value indicates that the motion vector difference horizontal component pair index value (mvd_col _j)air_index) is less than or equal to one (greater_l == 0), obtaining one as the motion vector difference horizontal component pair index value (mvd_col _j)air_index).

[0161] Obtaining the motion vector difference horizontal component pair index value (mvd_col jiair _index) includes, in response to a determination that the greater than one(grealer_l) flag value indicates that the motion vector difference horizontal component pair index value (mvd_col _pair_index) is greater than one and wherein a maximum offset value (max_(>llset_vcilue) is less than or equal to two (greater _1 == 1 && max_offset_value <= 2), obtaining two as the motion vector difference horizontal component pair index value (mvd_col jjair_index).

[0162] Obtaining the motion vector difference horizontal component pair index value (mvd_col _pair_index) includes reading, extracting, decoding, or otherwise accessing, such as from the encoded bitstream, wherein, or in response to a determination that, the greater than one (greater _7) flag indicates that the motion vector difference horizontal component pair index value (mvd_col _j)air_index) is greater than one and wherein a maximum offset value (max _offset _value) is greater than two (greater _1 == 1 && max_offset_value > 2), an encoded value indicating a result of subtracting two (2) from the motion vector difference horizontal component pair index value (mvd_col _j)air_index - 2), such as using quasiuniform coding, and obtaining, as the motion vector difference horizontal component pair index value (mvd_col _pair_index), a result of adding two (2) to the data indicating the result of subtracting two (2) from the motion vector difference horizontal component pair index value.

[0163] Obtaining the motion vector difference horizontal component pair index value (mvd_col jiair _index) (at 970) includes obtaining a greater than maximum value indicating whether the unsigned motion vector difference horizontal component value (\MVD.col\) is greater than the maximum motion vector difference horizontal component pair index value (\MVD.col\ > max_mvd_col _pair_index), by reading, extracting, decoding, or otherwise accessing, such as from the encoded bitstream, encoded greater than maximum data indicating a bit, flag, or other syntax element, such as using an entropy coding context (clx_idx) identified, derived, or selected, from a defined number, count, or cardinality, such as four, available entropy coding contexts, or cumulative distribution functions, in accordance with the shell class value (shell -Class'), such as by determining a minimum value among the shell class value (shell -Class') and three (3), which may be expressed as ctx_idx = min (shell_class, 3).

[0164] Obtaining the unsigned motion vector difference component values (at 970) includes, in response to a determination that the greater than maximum value indicates that the unsigned motion vector difference horizontal component value is greater than the maximum motion vector difference horizontal component pair index value, obtaining, as the unsigned motion vector difference horizontal component value, a result of subtracting themotion vector difference horizontal component pair index value (mvd_col _pair_index) from the shell index value.

[0165] Obtaining the unsigned motion vector difference component values (at 970) includes, in response to a determination that the greater than maximum value indicates that the unsigned motion vector difference horizontal component value is less than or equal to the maximum motion vector difference horizontal component pair index value, obtaining, as the unsigned motion vector difference horizontal component value, the motion vector difference horizontal component pair index value mvd_col _pair_index).

[0166] Obtaining the unsigned motion vector difference component values (at 970) includes obtaining, as the unsigned motion vector difference vertical component value, a result of subtracting the unsigned motion vector difference horizontal component value from the shell index value.

[0167] Obtaining the motion vector difference component signs (at 980) includes obtaining a motion vector difference horizontal component sign and a motion vector difference vertical component sign.

[0168] Obtaining the motion vector difference horizontal component sign includes, in response to a determination that the unsigned motion vector difference horizontal component value is greater than zero, obtaining the motion vector difference horizontal component sign by decoding an encoded motion vector difference horizontal component sign from the encoded bitstream.

[0169] Obtaining the motion vector difference vertical component sign includes, in response to a determination that the unsigned motion vector difference vertical component value is greater than zero, obtaining the motion vector difference vertical component sign by decoding an encoded motion vector difference vertical component sign from the encoded bitstream.

[0170] Although not expressly shown in FIG. 9, decoding using joint coding of motion vector differences 900 includes obtaining a motion vector predictor for decoding the current block, obtaining the motion vector for decoding the current block by combining, such as by adding, the motion vector predictor and the motion vector difference (MVD), obtaining decoded residual data, such as by decoding encoded residual data from the encoded bitstream, obtaining a prediction block in accordance with the motion vector, and obtaining a reconstructed block by combining the prediction block and the decoded residual data. The reconstructed block data for the current block is included in reconstructed frame data for the current frame, which is included in an output video stream, such as the output video stream504 shown in FIG. 5, which is output (at 930).

[0171] A broken directional line between output (at 930) and obtaining a motion vector difference (at 920) is shown (at 932) to indicate that decoding using joint coding of motion vector differences 900 may be performed on a per-block basis for the blocks from the current frame.

[0172] Although not shown expressly in FIG. 9, in some implementations, decoding using joint coding of motion vector differences 900 includes obtaining, or determining, that the prediction coding mode for the current block is compound prediction, or bi-prediction, wherein the current block is encoded using a first motion vector and a second motion vector, which includes obtaining a first motion vector difference (MVD) for the current block, obtaining a second motion vector difference MVD for the current block, obtaining the motion vector for the current block as the first motion vector using the first motion vector difference (MVD), obtaining the second motion vector for the current block using the second motion vector difference MVD, and obtaining the decoded block data by decoding the current block using the first motion vector and the second motion vector.

[0173] In an example, an apparatus may include a non-transitory computer readable medium and a processor configured to execute instructions stored on the non-transitory computer readable medium to generate encoded block data, wherein, to generate the encoded block data, the processor is configured to execute the instructions to encode a current block from a current frame from an input video stream, wherein, to encode the current block the processor is configured to execute the instructions to obtain, as a motion vector difference, a result of subtraction of a predicted motion vector from a motion vector used to encode the current block, wherein the motion vector difference includes a motion vector difference vertical component value and a motion vector difference horizontal component value; and obtain encoded motion vector difference data, wherein, to obtain the encoded motion vector difference data, the processor is configured to execute the instructions to encode the motion vector difference, wherein, to encode the motion vector difference, the processor is configured to execute the instructions to: obtain a scaled motion vector difference in accordance with a motion vector precision value for the motion vector difference and the motion vector difference, wherein, to obtain the scaled motion vector difference, the processor is configured to execute the instructions to, obtain a scaled motion vector difference vertical component value and a scaled motion vector difference horizontal component value; determine, as a shell index value, a sum of an absolute value of the scaled motion vector difference horizontal component value and an absolute value of the scaledmotion vector difference vertical component value; obtain encoded shell index data, wherein, to obtain the encoded shell index data, the processor is configured to execute the instructions to encode the shell index value; obtain encoded unsigned motion vector difference horizontal component value data, wherein, to obtain the encoded unsigned motion vector difference horizontal component value data, the processor is configured to execute the instructions to encode an unsigned motion vector difference horizontal component value; in response to a determination that an unsigned motion vector difference vertical component value is greater than zero, encode a sign of the motion vector difference vertical component value; and in response to a determination that the unsigned motion vector difference horizontal component value is greater than zero, encode a sign of the motion vector difference horizontal component value; wherein the processor is configured to execute the instructions to include the encoded block data in an encoded bitstream; and output the encoded bitstream.

[0174] FIG. 10 is a flowchart diagram of an example of encoding using frame-wise advanced motion vector difference coding 1000 in accordance with implementations of this disclosure. Encoding using frame-wise advanced motion vector difference coding 1000 may be implemented in an encoder, such as the encoder 400 shown in FIG. 4.

[0175] Encoding using frame-wise advanced motion vector difference coding 1000 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. 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.

[0176] In some encoders, the motion vector difference for a current block may be signaled by encoding a motion vector class value and encoding data, such as one or more bits, indicating an offset from a base value of the motion vector class. The base value of a motion vector class is the minimal value represented by the motion vector class. The motion vector class value (mv_class) indicates a class of the motion vector difference, or a respective component thereof, wherein a relatively high motion vector class value indicates that the motion vector difference is relatively large. The motion vector class value (mv_class) categorizes the motion vector differences into a defined set of classes, respectively representing a corresponding range of motion vector difference values. For example, the motion vector class may be from a defined set of motion vector classes, such as elevenmotion vector classes, as shown in Table 4. Other class structures may be used.[Table 4]

[0177] In some encoders, the motion vector difference is signaled using advanced motion vector difference mode (AMVD). Using the advanced motion vector difference mode includes, for motion vector classes other than the first, or minimal, motion vector class (MV_CLASS_0), signaling the motion vector class, and omitting, skipping, or excluding signaling data indicating an offset from the base value of the motion vector class. For motion vector classes other than the first motion vector class (MV_CLASS_O), one motion vector difference value, such as the base value of the motion vector class, is available for the motion vector class and other values within the range of values for the motion vector class are unavailable. An example of available motion vector difference values for the motion vector classes are shown in Table 5. Other class structures may be used.[Table 5]

[0178] Encoding using frame-wise advanced motion vector difference coding 1000 is similar to advanced motion vector difference mode, except as is described herein or as is otherwise clear from context.

[0179] Encoding using frame-wise advanced motion vector difference coding 1000 includes obtaining a current frame (at 1010), obtaining encoded motion vector difference set data for the current frame (at 1020), obtaining encoded block data (at 1030), and outputting the encoded bitstream (at 1040).

[0180] Although not shown expressly in FIG. 10, encoding using frame-wise advanced motion vector difference coding 1000 includes other aspects of video coding for encoding the current block. For example, encoding using frame- wise advanced motion vector difference coding 1000 includes obtaining, or determining, a prediction coding mode, such as an inter prediction coding mode, which includes obtaining, such as prior to coding the current block, a set, list, or array, of candidate, or reference, motion vectors (ref_mvs), such as from one or more context blocks for coding the current block, such as neighboring previously coded blocks, collocated previously coded blocks, or a combination thereof, which may be referred to as a dynamic reference list (DRL). In another example, encoding using frame- wise advanced motion vector difference coding 1000 includes obtaining a predicted motion vector, which is an optimal candidate, or reference, motion vector, for the current block, from the dynamic reference list, obtaining a motion vector for the current block, obtaining encoded block data by encoding the current block using the motion vector, and including the encoded block data in an encoded, or output, bitstream. The predicted motion vector includes a horizontal (x or column) component (ref_mv.col) and a vertical (y or row) component ref_mv. row), which may be expressed using relative Cartesian coordinates. The motion vector includes a horizontal (x) component (mv.col) and a vertical (y) component (mv.row), which may be expressed using relative Cartesian coordinates.

[0181] The current frame is obtained (at 1010). The current frame is a frame from the input video, or input video stream. In some implementations, the input video stream may include one or more sequences of frames. A sequence of frames may have a defined cardinality, or number, of frames. For example, the encoder, or a component thereof, such asan intra / inter prediction unit of the encoder, such as the intra / inter prediction unit 410 shown in FIG. 4, may obtain the input video stream. The current frame may be obtained (at 1010) 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.

[0182] Obtaining the encoded motion vector difference set data for the current frame (at 1020) includes obtaining defined sets of available motion vector difference values (MVD_sets). A set, or array, of available motion vector difference values may include a defined cardinality, such as nine (9), available motion vector difference values, which may be identified, or indexed, within the respective set, or array, of available motion vector difference values in accordance with a motion vector difference set index value. A defined set of available motion vector difference values (motion vector difference set) may be identified, or indicated, by a corresponding motion vector difference set value (mvdsef). An example of defined sets of available motion vector difference values (MVD_sets) is shown in Table 6. Other sets of available motion vector difference values may be used.[Table 6

[0183] Obtaining the encoded motion vector difference set data for the current frame (at 1020) includes obtaining a motion vector difference set value (mvdsef), indicating a defined set of available motion vector differences, for the current frame from the defined sets of available motion vector difference values (MVD_sets), as shown in Table 6.

[0184] Obtaining the encoded motion vector difference set data for the current frame (at 1020) includes obtaining the encoded motion vector difference set data by encoding the motion vector difference set value (mvdsef) for the current frame, such as in a header for the current frame, such as using a ternary symbol.

[0185] Obtaining the encoded block data (at 1030) includes obtaining a current block from the current frame, such as in accordance with a block-coding order and encoding the currentblock.

[0186] Encoding the current block includes obtaining a motion vector difference value for the current block as described herein.

[0187] Encoding the current block includes obtaining encoded motion vector difference mode data for the current block (at 1050) and obtaining encoded motion vector difference set index data (at 1060).

[0188] Obtaining the encoded motion vector difference mode data for the current block (at 1050) includes determining whether advanced motion vector difference mode is active for the current block.

[0189] Obtaining the encoded motion vector difference mode data for the current block (at 1050) includes encoding an advanced motion vector difference mode value indicating whether advanced motion vector difference mode is active for the current block.

[0190] In some implementations, in response to a determination that advanced motion vector difference mode is inactive, or unavailable, for the current block, obtaining the encoded motion vector difference mode data for the current block includes encoding an advanced motion vector difference mode value indicating that advanced motion vector difference mode is inactive, or unavailable, for the current block. In response to a determination that advanced motion vector difference mode is inactive, or unavailable, for the current block, obtaining encoded motion vector difference set index data (at 1060) may be omitted, or skipped, for the current block as indicated by the broken directional line from obtaining the encoded motion vector difference mode data for the current block (at 1050) to output (at 1040).

[0191] In some implementations, in response to a determination that advanced motion vector difference mode is active, or available, for the current block, obtaining the encoded motion vector difference mode data for the current block includes encoding an advanced motion vector difference mode value indicating that advanced motion vector difference mode is active, or available, for the current block.

[0192] Obtaining the encoded motion vector difference set index data (at 1060), such as in response to a determination that advanced motion vector difference mode is active, or available, for the current block, includes obtaining a motion vector difference set index value from the motion vector difference set indicated by the motion vector difference set value (obtained at 1020) in accordance with the motion vector difference for the current block, as shown in Table 6. For example, the motion vector difference set value (mvdsef) may be one (1), the motion vector difference set index value may be three (3), and the available motionvector difference value eight (8) may be used as the motion vector difference.

[0193] Obtaining the encoded motion vector difference set index data (at 1060), such as in response to a determination that advanced motion vector difference mode is active, or available, for the current block, includes encoding the motion vector difference set index value for the current block, such as using a 9-ary symbol or syntax element.

[0194] In some implementations, obtaining the defined sets of available motion vector difference values may be omitted, the motion vector difference set indicated as mvdsetO in Table 6 may be obtained as the motion vector difference set, and obtaining the encoded motion vector difference set data may be omitted. In some implementations, the motion vector difference vertical component value (MV D. row) is other than zero, the motion vector difference set index value for the motion vector difference vertical component value is signaled using an, such as one, 8-ary symbol, and the motion vector difference vertical component sign is signaled. In some implementations, the motion vector difference horizontal component value (A / VD.coZ) is other than zero, the motion vector difference set index value for the motion vector difference horizontal component value is signaled using an, such as one, 8-ary symbol, and the motion vector difference horizontal component sign is signaled.

[0195] Outputting the encoded bitstream (at 1040) includes including the encoded block data for the current block in the encoded frame data for the current frame, including the encoded frame data for the current frame in the encoded bitstream, and outputting the encoded bitstream.

[0196] In an example, a method includes generating encoded frame data by encoding a current frame from an input video stream, wherein encoding the current frame includes: encoding a motion vector difference set value for the current frame, wherein the motion vector difference set value indicates a motion vector difference set from defined sets of available motion vector difference values; generating encoded block data by encoding a current block from the current frame, wherein encoding the current block includes: encoding an advanced motion vector difference mode value, wherein the advanced motion vector difference mode value indicates whether advanced motion vector difference mode is active for the current block; in response to a determination that advanced motion vector difference mode is active for the current block, encoding a motion vector difference set index value from the motion vector difference set; and including the encoded block data in the encoded frame data; including the encoded frame data in an encoded bitstream; and outputting the encoded bitstream.

[0197] In an example, an apparatus may include a non-transitory computer readable medium and a processor configured to execute instructions stored on the non-transitory computer readable medium to generate encoded frame data, wherein, to generate the encoded frame data, the processor is configured to execute the instructions to encode a current frame from an input video stream, wherein, to encode the current frame, the processor is configured to execute the instructions to: encode a motion vector difference set value for the current frame, wherein the motion vector difference set value indicates a motion vector difference set from defined sets of available motion vector difference values; generate encoded block data, wherein, to generate the encoded block data, the processor is configured to execute the instructions to encode a current block from the current frame, wherein, to encode the current block, the processor is configured to execute the instructions to: encode an advanced motion vector difference mode value, wherein the advanced motion vector difference mode value indicates whether advanced motion vector difference mode is active for the current block; in response to a determination that advanced motion vector difference mode is active for the current block, encode a motion vector difference set index value from the motion vector difference set; and include the encoded block data in the encoded frame data; wherein the processor is configured to execute the instructions to include the encoded frame data in an encoded bitstream; and output the encoded bitstream.

[0198] FIG. 11 is a flowchart diagram of an example of decoding using the frame-wise advanced motion vector difference coding mode 1100 in accordance with implementations of this disclosure. Decoding using the frame- wise advanced motion vector difference coding mode 1100 may be implemented in a decoder, such as the decoder 500 shown in FIG. 5.

[0199] Decoding using frame- wise advanced motion vector difference coding 1100 includes 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.

[0200] Decoding using frame- wise advanced motion vector difference coding 1100 is similar to advanced motion vector difference mode, except as is described herein or as is otherwise clear from context.

[0201] Decoding using frame- wise advanced motion vector difference coding 1100 includes decoding a current frame (at 1110), obtaining motion vector difference set data for the current frame (at 1120), decoding current block data (at 1130), and outputting a reconstructed video stream (at 1140).

[0202] The current frame is decoded (at 1110). Decoding the current frame includesobtaining encoded frame data for the current frame and decoding the encoded frame data.

[0203] Obtaining the motion vector difference set data for the current frame (at 1120) includes obtaining the defined sets of available motion vector difference values (MVD_sets), as shown in Table 6.

[0204] Obtaining the motion vector difference set data for the current frame (at 1120) includes obtaining a motion vector difference set value (mvdsef), indicating a defined set of available motion vector differences, for the current frame from the defined sets of available motion vector difference values (MVD_sets as shown in Table 6, by decoding the encoded motion vector difference set value (mvdsef) for the current frame, such as from the header for the current frame, such as using a ternary symbol.

[0205] Decoding the current block data (at 1130) includes obtaining an advanced motion vector difference mode value for the current block (at 1150) and obtaining a motion vector difference set index value (at 1160).

[0206] Obtaining the advanced motion vector difference mode value for the current block (at 1150) includes obtaining encoded motion vector difference mode data for the current block from the encoded bitstream data for the current block and decoding the encoded motion vector difference mode data.

[0207] Obtaining the motion vector difference mode data for the current block (at 1150) includes determining whether advanced motion vector difference mode is active for the current block in accordance with the advanced motion vector difference mode value for the current block.

[0208] In some implementations, in response to a determination that advanced motion vector difference mode is inactive, or unavailable, for the current block, obtaining the motion vector difference set index value (at 1160) may be omitted, or skipped, for the current block as indicated by the broken directional line from obtaining advanced motion vector difference mode value for the current block (at 1150) to output (at 1140).

[0209] Obtaining the motion vector difference set index value (at 1160), such as in response to a determination that advanced motion vector difference mode is active, or available, for the current block, includes decoding the motion vector difference set index value from the encoded block data for the current block, such as using a 9-ary symbol or syntax element.

[0210] Outputting the reconstructed video stream (at 1140) includes including the decoded block data for the current block in the decoded frame data for the current frame, including the decoded frame data for the current frame in the reconstructed video stream, and outputtingthe reconstructed video stream. Some aspects of decoding are omitted from the description of FIG. 11 for brevity and simplicity.

[0211] In an example, a method includes decoding a current frame from an encoded bitstream, wherein decoding the current frame includes: decoding a motion vector difference set value for the current frame, wherein the motion vector difference set value indicates a motion vector difference set from defined sets of available motion vector difference values; decoding a current block from the current frame, wherein decoding the current block includes: decoding an advanced motion vector difference mode value, wherein the advanced motion vector difference mode value indicates whether advanced motion vector difference mode is active for the current block; in response to a determination that advanced motion vector difference mode is active for the current block, decoding a motion vector difference set index value from the motion vector difference set; and including the current block in the current frame; including data of the current frame in an output video stream; and outputting the output video stream.

[0212] In an example, an apparatus may include a non-transitory computer readable medium and a processor configured to execute instructions stored on the non-transitory computer readable medium to decode a current frame from an encoded bitstream, wherein, to decode the current frame, the processor is configured to execute the instructions to a motion vector difference set value for the current frame, wherein the motion vector difference set value indicates a motion vector difference set from defined sets of available motion vector difference values; decode a current block from the current frame, wherein, to decode the current block, the processor is configured to execute the instructions to: decode an advanced motion vector difference mode value, wherein the advanced motion vector difference mode value indicates whether advanced motion vector difference mode is active for the current block; in response to a determination that advanced motion vector difference mode is active for the current block, decode a motion vector difference set index value from the motion vector difference set; and include the current block in the current frame; wherein the processor is configured to execute the instructions to include data of the current frame in an output video stream; and output the output video stream.

[0213] 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.

[0214] 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-dimensionalarray or vector, except as expressly described herein or otherwise clear from context.

[0215] 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. 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.

[0216] 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.

[0217] 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 usedinterchangeably. 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.

[0218] 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.

[0219] 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.

[0220] 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.

[0221] 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.

[0222] 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

CLAIMSWhat is claimed is:

1. A method comprising: generating reconstructed block data by decoding a current block from a current frame from an encoded bitstream, wherein decoding the current block includes obtaining a motion vector for decoding the current block by: obtaining a shell index value by decoding encoded shell index data from the encoded bitstream; obtaining an unsigned motion vector difference horizontal component value by decoding encoded unsigned motion vector difference horizontal component value data from the encoded bitstream; obtaining, as an unsigned motion vector difference vertical component value, a result of subtracting the unsigned motion vector difference horizontal component value from the shell index value; in response to a determination that the unsigned motion vector difference vertical component value is greater than zero, obtaining a motion vector difference vertical component sign by decoding encoded motion vector difference vertical component sign data from the encoded bitstream; in response to a determination that the unsigned motion vector difference horizontal component value is greater than zero, obtaining a motion vector difference horizontal component sign by decoding encoded motion vector difference horizontal component sign data from the encoded bitstream; and obtaining, as the motion vector, a sum of the motion vector difference and a predicted motion vector for the current block; including the reconstructed block data in a reconstructed frame; and outputting the reconstructed frame.

2. The method of claim 1, wherein decoding the encoded shell index data includes: obtaining a shell class value by decoding encoded shell class data from the encoded bitstream using a cumulative distribution function corresponding to a motion vector precision value for the current block; obtaining a shell class base index value in accordance with the shell class value, wherein obtaining the shell class base index value includes:in response to a determination that the shell class value is zero, obtaining zero as the shell class base index value; or in response to a determination that the shell class value is greater than zero, obtaining, as the shell class base index value, a result of left bit-shifting one by the shell class value; obtaining a shell offset value by decoding encoded shell offset data from the encoded bitstream; and obtaining, as the shell index value, a sum of the shell offset value and the shell class base index value.

3. The method of claim 2, wherein obtaining the shell offset value includes: in response to a determination that the shell class value is less than two: obtaining the shell offset value by decoding the encoded shell offset data using a coding context identified in accordance with the shell class value; in response to a determination that the shell class value is two: decoding one or more bin values, wherein decoding a respective bin value from the one or more bin values includes identifying a cumulative distribution function for decoding the respective bin value in accordance with a bin index of the respective bin value; and obtaining the shell offset value by reconstructing the shell offset value using truncated unary coding in accordance with the one or more bin values; or in response to a determination that the shell class value is greater than two: obtaining the shell offset value by decoding the shell offset value on a per-bit basis, wherein decoding the shell offset value on a per-bit basis includes decoding a respective bit of the shell offset value using a coding context corresponding to a bit position of the respective bit.

4. The method of claim 1, wherein decoding the encoded unsigned motion vector difference horizontal component value data includes: obtaining a motion vector difference horizontal component pair index value, wherein obtaining the motion vector difference horizontal component pair index includes: obtaining a greater than zero flag value indicating whether the motion vector difference horizontal component pair index value is greater than zero by decoding encoded greater than zero flag data from the encoded bitstream.

5. The method of claim 4, wherein obtaining the motion vector difference horizontal component pair index includes: in response to a determination that the greater than zero flag indicates that the motion vector difference horizontal component pair index value is other than greater than zero, obtaining zero as the motion vector difference horizontal component pair index value.

6. The method of claim 4, wherein obtaining the motion vector difference horizontal component pair index includes: in response to a determination that the greater than zero flag indicates that the motion vector difference horizontal component pair index value is greater than zero, obtaining a greater than one flag value indicating whether the motion vector difference horizontal component pair index value is greater than one by decoding encoded greater than one flag data from the encoded bitstream.

7. The method of claim 6, wherein obtaining the motion vector difference horizontal component pair index includes: in response to a determination that the greater than one flag value indicates that the motion vector difference horizontal component pair index value is less than or equal to one, obtaining one as the motion vector difference horizontal component pair index value.

8. The method of claim 6, wherein obtaining the motion vector difference horizontal component pair index includes: in response to a determination that the greater than one flag value indicates that the motion vector difference horizontal component pair index value is greater than one, and wherein a maximum offset value is less than or equal to two, obtaining two as the motion vector difference horizontal component pair index value.

9. The method of claim 6, wherein obtaining the motion vector difference horizontal component pair index includes: in response to a determination that the greater than one flag value indicates that the motion vector difference horizontal component pair index value is greater than one, and wherein a maximum offset value is greater than two:obtaining a value for obtaining the motion vector difference horizontal component pair index value by decoding an encoded value for obtaining the motion vector difference horizontal component pair index value from the encoded bitstream; and obtaining, as the motion vector difference horizontal component pair index value, a result of adding two to the value for obtaining the motion vector difference horizontal component pair index value.

10. The method of claim 4, wherein obtaining the motion vector difference horizontal component pair index includes: obtaining a greater than maximum value indicating whether the unsigned motion vector difference horizontal component value is greater than a maximum motion vector difference horizontal component pair index value by decoding encoded greater than maximum data from the encoded bitstream; and in response to a determination that the greater than maximum value indicates that the unsigned motion vector difference horizontal component value is greater than the maximum motion vector difference horizontal component pair index value, obtaining, as the unsigned motion vector difference horizontal component value, a result of subtracting the motion vector difference horizontal component pair index value from the shell index value; or in response to a determination that the greater than maximum value indicates that the unsigned motion vector difference horizontal component value is less than or equal to the maximum motion vector difference horizontal component pair index value, obtaining, as the unsigned motion vector difference horizontal component value, the motion vector difference horizontal component pair index value.

11. A method comprising: generating encoded block data by encoding a current block from a current frame from an input video stream, wherein encoding the current block includes: obtaining a motion vector difference by subtracting a predicted motion vector from a motion vector used to encode the current block, wherein the motion vector difference includes a motion vector difference vertical component value and a motion vector difference horizontal component value; and obtaining encoded motion vector difference data by encoding the motion vector difference, wherein encoding the motion vector difference includes:obtaining a scaled motion vector difference in accordance with a motion vector precision value for the motion vector difference and the motion vector difference, wherein obtaining the scaled motion vector difference includes obtaining a scaled motion vector difference vertical component value and a scaled motion vector difference horizontal component value; determining, as a shell index value, a sum of an absolute value of the scaled motion vector difference horizontal component value and an absolute value of the scaled motion vector difference vertical component value; obtaining encoded shell index data by encoding the shell index value; obtaining encoded unsigned motion vector difference horizontal component value data by encoding an unsigned motion vector difference horizontal component value; in response to a determination that an unsigned motion vector difference vertical component value is greater than zero, encoding a sign of the motion vector difference vertical component value; and in response to a determination that the unsigned motion vector difference horizontal component value is greater than zero, encoding a sign of the motion vector difference horizontal component value; including the encoded block data in an encoded bitstream; and outputting the encoded bitstream.

12. The method of claim 11, wherein encoding the shell index value includes: obtaining encoded shell class data by encoding a shell class value, wherein encoding the shell class value includes: in response to determining that the shell index value is less than two, obtaining zero as the shell class value; and in response to determining that the shell index value is greater than or equal to two, obtaining, as the shell class value, a binary logarithm of the shell index value; obtaining a shell class base index value in accordance with the shell class value by: in response to a determination that the shell class value is zero, obtaining zero as the shell class base index value; or in response to a determination that the shell class value is greater than zero, obtaining, as the shell class base index value, a result of left bit-shifting one by the shell class value;obtaining, as a shell offset value, a result of subtracting the shell class base index value from the shell index value; and obtaining encoded shell offset data by encoding the shell offset value.

13. The method of claim 12, wherein encoding the shell offset value includes: in response to a determination that the shell class value is less than two: identifying a coding context for encoding the shell offset value in accordance with the shell class value; and obtaining encoded shell offset value data by encoding the shell offset value using the coding context for encoding the shell offset value; in response to a determination that the shell class value is two: obtaining encoded shell offset value data by: obtaining bin data by binarizing the shell offset value using truncated unary coding, wherein the bin data includes one or more binary values corresponding to respective bin index values; and obtaining the encoded shell offset value data by encoding the bin data on a per-bin basis, wherein encoding the bin data includes, for a respective bin, identifying a coding context in accordance with the corresponding bin index value; or in response to a determination that the shell class value is greater than two: obtaining the encoded shell offset value data by encoding the shell offset value on a per-bit basis, wherein encoding the shell offset value on a per-bit basis includes, encoding a respective bit using a coding context corresponding to a bit position of the bit.

14. The method of claim 11, wherein encoding the unsigned motion vector difference horizontal component value includes: obtaining, as a maximum motion vector difference horizontal component pair index value, a result of right bit-shifting the shell index value by one; and in response to determining that the unsigned motion vector difference horizontal component value is less than or equal to the maximum motion vector difference horizontal component pair index value, obtaining, as the motion vector difference horizontal component pair index value, the unsigned motion vector difference horizontal component value; orin response to determining that the unsigned motion vector difference horizontal component value is greater than the maximum motion vector difference horizontal component pair index value, obtaining, as the motion vector difference horizontal component pair index value, a result of subtracting the unsigned motion vector difference horizontal component value from the shell index value.

15. The method of claim 14, wherein encoding the unsigned motion vector difference horizontal component value includes: including, in the encoded block data, data indicating whether the motion vector difference horizontal component pair index value is greater than zero.

16. The method of claim 15, wherein encoding the unsigned motion vector difference horizontal component value includes: in response to a determination that the motion vector difference horizontal component pair index value is greater than zero, including, in the encoded block data, data indicating whether the motion vector difference horizontal component pair index value is greater than one.

17. The method of claim 16, wherein encoding the unsigned motion vector difference horizontal component value includes: in response to a determination that the motion vector difference horizontal component pair index value is greater than one, including, in the encoded block data, a result of subtracting two from the motion vector difference horizontal component pair index value, the result coded using quasi-uniform coding.

18. The method of claim 14, wherein encoding the unsigned motion vector difference horizontal component value includes: including, in the encoded block data, data indicating whether the unsigned motion vector difference horizontal component value is greater than the maximum motion vector difference horizontal component pair index value using a context identified in accordance with a minimum value among three and a shell class value.

19. The method of claim 11, wherein: obtaining the scaled motion vector difference vertical component value includes:obtaining, as the scaled motion vector difference vertical component value, a result of right bit- shifting the unsigned motion vector difference vertical component value by a result of subtracting the motion vector precision value from a maximum motion vector precision value; and obtaining the scaled motion vector difference horizontal component value includes: obtaining, as the scaled motion vector difference horizontal component value, a result of right bit-shifting the unsigned motion vector difference horizontal component value by the result of subtracting the motion vector precision value from the maximum motion vector precision value.

20. A non-transitory computer-readable storage medium having stored thereon an encoded bitstream comprising: encoded shell index data indicating a shell index value for obtaining a motion vector difference for obtaining a motion vector for decoding a current block from a current frame; encoded unsigned motion vector difference horizontal component value data indicating an unsigned motion vector difference horizontal component value for obtaining the motion vector; encoded motion vector difference horizontal component sign data indicating a motion vector difference horizontal component sign, wherein a combination of the motion vector difference horizontal component sign and the unsigned motion vector difference horizontal component value is a motion vector difference horizontal component value of a motion vector difference for obtaining the motion vector; and encoded motion vector difference vertical component sign data indicating a motion vector difference vertical component sign, wherein a combination of the motion vector difference vertical component sign and a result of subtracting the unsigned motion vector difference horizontal component value from the shell index value is a motion vector difference vertical component value of the motion vector difference.

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