Multi-class restoration filtering

Abstract

Encoding using multi-class restoration filtering includes identifying a current restoration unit of the current frame, obtaining a reference restoration filter parameters superset identifier from the encoded bitstream for the current restoration unit, obtaining, in accordance with the reference restoration filter parameters superset identifier, as a current reference restoration filter parameters superset, a defined reference restoration filter parameters superset or a reference restoration filter parameters superset from a dynamic reference restoration filters buffer, wherein the dynamic reference restoration filters buffer includes reference restoration filter parameters supersets previously used for restoration filtering a reference frame of the current frame or for restoration filtering a second restoration unit of the current frame, obtaining a filtered restoration unit by filtering the restoration unit using restoration filter parameters obtained from the current reference restoration filter parameters superset, including the filtered restoration unit in the reconstructed frame data, and outputting the reconstructed frame data.

Description

MULTI-CLASS RESTORATION FILTERINGBACKGROUND

[0001] 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

[0002] 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 multi-class restoration filtering.

[0003] Variations in these and other aspects will be described in additional detail hereafter.

[0004] An aspect is a method for decoding using multi-class restoration filtering.Decoding using multi-class restoration filtering includes generating reconstructed frame data by decoding an encoded bitstream. Decoding the encoded bitstream may include obtaining decoded frame data for a current frame by decoding encoded frame data from the encoded bitstream, obtaining the reconstructed frame data by restoration filtering the decoded frame data and outputting the reconstructed frame data. Restoration filtering the decoded frame data may include identifying a current restoration unit of the current frame, obtaining a reference restoration filter parameters superset identifier from the encoded bitstream for the current restoration unit, obtaining, in accordance with the reference restoration filter parameters superset identifier, as a current reference restoration filter parameters superset, a defined reference restoration filter parameters superset or a reference restoration filter parameters superset from a dynamic reference restoration filters buffer, wherein the dynamic reference restoration filters buffer includes reference restoration filter parameters supersets previously used for restoration filtering a reference frame of the current frame or for restoration filtering a second restoration unit of the current frame, obtaining a filtered restoration unit by filtering the restoration unit using restoration filter parameters obtained from the current reference restoration filter parameters superset, and including the filtered restoration unit in thereconstructed frame data.

[0005] An aspect is an apparatus for decoding using multi-class restoration filtering. The apparatus for decoding using multi-class restoration filtering includes a non-transitory computer-readable medium (non-transitory computer-readable storage medium), or a memory, and a processor configured to execute instructions stored on the non-transitory computer readable medium to perform multi-class restoration filtering.

[0006] An aspect is a computer readable medium including an encoded bitstream, the encoded bitstream comprising encoded frame data for a current frame and a reference restoration filter parameters superset identifier for a restoration unit of the current frame, wherein the reference restoration filter parameters superset identifier identifies a defined reference restoration filter parameters superset or a reference restoration filter parameters superset from a dynamic reference restoration filters buffer, wherein the dynamic reference restoration filters buffer includes reference restoration filter parameters supersets previously used for restoration filtering a reference frame of the current frame or for restoration filtering a second restoration unit of the current frame. The encoded bitstream may include a reference restoration filter modification flag indicating whether to modify the current reference restoration filter parameters superset, and a restoration filtering classes subset identifier that identifies a current restoration filtering classes subset from a defined cardinality of restoration filtering classes subsets, wherein a respective restoration filtering classes subset includes a respective subset of restoration filtering classes. The restoration filtering classes subset identifier may be an index value with respect to an index of the defined cardinality of restoration filtering classes subsets. The restoration filtering classes subset identifier may include one or more restoration filtering classes subset branch identifiers. The zero or more restoration filtering classes subset branch identifiers may be binary. The encoded bitstream may include a reference restoration filter modification type flag that indicates modification in accordance with the defined reference restoration filter parameters superset or in accordance with signaled restoration filter parameters modification data. The encoded bitstream may include the restoration filter parameters modification data. The restoration filter parameters modification data may include a set of restoration filter parameters. The restoration filter parameters modification data may include differential restoration filter parameters indicating a difference between modified centroid restoration filter parameters and centroid restoration filter parameters with respect to the current restoration filtering classes subset.

[0007] An aspect is a method for encoding using multi-class restoration filtering.

[0008] An aspect is an apparatus for encoding using multi-class restoration filtering.BRIEF DESCRIPTION OF THE DRAWINGS

[0009] 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.

[0010] FIG. 1 is a diagram of a computing device in accordance with implementations of this disclosure.

[0011] FIG. 2 is a diagram of a computing and communications system in accordance with implementations of this disclosure.

[0012] FIG. 3 is a diagram of a video stream for use in encoding and decoding in accordance with implementations of this disclosure.

[0013] FIG. 4 is a block diagram of an encoder in accordance with implementations of this disclosure.

[0014] FIG. 5 is a block diagram of a decoder in accordance with implementations of this disclosure.

[0015] FIG. 6 is a block diagram of a representation of a portion of a frame in accordance with implementations of this disclosure.

[0016] FIG. 7 is a diagram of an example of a restoration filter in accordance with implementations of this disclosure.

[0017] FIG. 8 is a diagram of an example of restoration filtering classes subsets in accordance with implementations of this disclosure.

[0018] FIG. 9 is a diagram of an example of hierarchical restoration filtering classes subsets in accordance with implementations of this disclosure.

[0019] FIG. 10 is a diagram of an example of binary symmetrical hierarchical restoration filtering classes subsets in accordance with implementations of this disclosure.

[0020] FIG. 11 is a flowchart diagram of an example of decoding using multi-class restoration filtering in accordance with implementations of this disclosure.

[0021] FIG. 12 is a diagram of an example of coding restoration filter modification data in accordance with implementations of this disclosure.

[0022] FIG. 13 is a flowchart diagram of an example of encoding using multi-class restoration filtering in accordance with implementations of this disclosure.DETAILED DESCRIPTION

[0023] Image and video compression schemes may include breaking an image, or frame,into smaller portions, such as blocks, and generating an output bitstream using techniques to minimize the bandwidth utilization of the information included for each block in the output. In some implementations, the information included for each block in the output may be limited by reducing spatial redundancy, reducing temporal redundancy, or a combination thereof. For example, temporal or spatial redundancies may be reduced by predicting a frame, or a portion thereof, based on information available to both the encoder and decoder, and including information representing a difference, or residual, between the predicted frame and the original frame in the encoded bitstream. The residual information may be further compressed by transforming the residual information into transform coefficients (e.g., energy compaction), quantizing the transform coefficients, and entropy coding the quantized transform coefficients. Other coding information, such as motion information, may be included in the encoded bitstream, which may include transmitting differential information based on predictions of the encoding information, which may be entropy coded to further reduce the corresponding bandwidth utilization. An encoded bitstream can be decoded to reconstruct the blocks and the source images from the limited information. In some implementations, the accuracy, efficiency, or both, of coding a block using either interprediction or intra-prediction may be limited.

[0024] Block-based hybrid video coding techniques, or codecs, to improve coding efficiency, image quality, or both, may in-loop restoration filter, such as deblocking filter, one or more decoded images to improve image quality. Subsequent to restoration filtering, a reconstructed frame may be stored and used as a reference frame for coding another frame. For example, in-loop filtering may include Wiener filtering, wherein pixels of a frame are filtered using a two-dimensional (2D) linear filter having a shape, such as a diamond or a star, centered on a center pixel and using filter coefficients that are expressly signaled in the bitstream. In some codecs, multiple restoration filters are available. Restoration filters, and the parameters thereof, may be signaled on a per restoration unit (RU) basis. One or more restoration units may be identified for a frame, and restoration filter, or loop filter, parameters may be signaled on a per restoration unit basis.

[0025] In some codecs, a restoration filter may be subject to one or more constraints, such as symmetry constraints, such as origin-symmetry or origin anti-symmetry, which may reduce the number, count, or cardinality, of coefficients to signal for the filter. In some codecs, a dynamic list of filters previously used for a frame may be maintained and the parameters for restoration filtering a restoration unit may be signaled by an index value referring to the filters previously used for the frame. In some codecs, for restoration of arestoration unit a reference restoration filter may be signaled by an index value referring to the filters previously used for the frame and a difference between the coefficients of the filter used by the encoder for restoration filtering the restoration unit and the coefficients of the reference restoration filter may be signaled as differential restoration filter coefficients or parameters. The decoder decodes the index of the reference restoration filter, decodes the differential restoration filter coefficients, and adds the differential restoration filter coefficients to the filter coefficients of the reference restoration filter to obtain the filter coefficients of the restoration filter for the restoration unit. In some codecs, pixels, or small, such as 4x4, blocks of pixels, may be classified, such as based on edge strength, directionality, or both, and restoration filters may be identified based on pixel class. The number, count, or cardinality, of classes (C) is the number, count, or cardinality, sets of filter parameters signaled on a per restoration unit basis. The signaling cost for signaling restoration filters, including signaling restoration filter coefficients, may reduce coding efficiency.

[0026] In some codecs, per-class filter parameters may be determined, trained, or defined, such as based on training data, prior to coding a current frame or video, such that signaling restoration filter parameters may be omitted, avoided, or skipped. Using determined, trained, or defined, per-class filter parameters may reduce the signaling cost for signaling restoration filters and may reduce image quality or accuracy.

[0027] The encoding and decoding using multi-class restoration filtering described herein improves on video coding techniques, or codecs, by improving coding efficiency relative to image quality or accuracy. Encoding and decoding using multi-class restoration filtering includes using determined, trained, or defined, per-class filter parameters and expressly signaled filter parameters.

[0028] 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.

[0029] 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 thecomputing 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.

[0030] 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.

[0031] 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.

[0032] The data 112 can include information, such as input audio data, encoded audio data, decoded audio data, or the like. The instructions 114 can include directions, such as code, for performing any method, or any portion or portions thereof, disclosed herein. The instructions 114 can be realized in hardware, software, or any combination thereof. For example, the instructions 114 may be implemented as information stored in the memory 110, such as a computer program, which may be executed by the processor 120 to perform any of the respective methods, algorithms, aspects, or combinations thereof, as described herein.

[0033] 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 acombination thereof.

[0034] 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.

[0035] 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.

[0036] The electronic communication unit 140 can transmit, receive, or transmit and receive signals via a wired or wireless electronic communication medium 180, such as a radio frequency (RF) communication medium, an ultraviolet (UV) communication medium, a visible light communication medium, a fiber optic communication medium, a wireline communication medium, or a combination thereof. For example, as shown, the electronic communication unit 140 is operatively connected to an electronic communication interface 142, such as an antenna, configured to communicate via wireless signals.

[0037] 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 electroniccommunication units and any number of electronic communication interfaces can be used.

[0038] 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.

[0039] 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.

[0040] Although shown as separate units, the electronic communication unit 140, the electronic communication interface 142, the user interface 130, the power source 160, or portions thereof, may be configured as a combined unit. For example, the electronic communication unit 140, the electronic communication interface 142, the user interface 130, and the power source 160 may be implemented as a communications port capable of interfacing with an external display device, providing communications, power, or both.

[0041] 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.

[0042] 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.

[0043] 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.

[0044] 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.

[0045] A computing and communication device 100A, 100B, 100C can be, for example, a computing device, such as the computing device 100 shown in FIG. 1. For example, the computing and communication devices 100A, 100B may be user devices, such as a mobile computing device, a laptop, a thin client, or a smartphone, and the computing and communication device 100C may be a server, such as a mainframe or a cluster. Although the computing and communication device 100A and the computing and communication device 100B are described as user devices, and the computing and communication device 100C is described as a server, any computing and communication device may perform some or all of the functions of a server, some, or all, of the functions of a user device, or some or all of the functions of a server and a user device. For example, the server computing and communication device 100C may receive, encode, process, store, transmit, or a combination thereof audio data and one or both of the computing and communication device 100A and the computing and communication device 100B may receive, decode, process, store, present, or a combination thereof the audio data.

[0046] 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.

[0047] 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.

[0048] The network 220 can be any type of network configured to provide services, such as voice, data, applications, voice over internet protocol (VoIP), or any other communications protocol or combination of communications protocols, over a wired or wireless communication link. For example, the network 220 can be a local area network (LAN), wide area network (WAN), virtual private network (VPN), a mobile or cellular telephone network, the Internet, or any other means of electronic communication. The network can use a communication protocol, such as the transmission control protocol (TCP), the user datagram protocol (UDP), the internet protocol (IP), the real-time transport protocol (RTP) the HyperText Transport Protocol (HTTP), or a combination thereof.

[0049] 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 device100A can communicate via a first access point 210A using a first type of communication link,a second computing and communication device 100B can communicate via a second access point 21 OB using a second type of communication link, and a third computing and communication device 100C can communicate via a third access point (not shown) using a third type of communication link. Similarly, the access points 210A, 210B can communicate with the network 220 via one or more types of wired or wireless communication links 230A, 230B. Although FIG. 2 shows the computing and communication devices 100A, 100B, 100C in communication via the network 220, the computing and communication devices 100A, 100B, 100C can communicate with each other via any number of communication links, such as a direct wired or wireless communication link.

[0050] 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.

[0051] Other implementations of the computing and communications system 200 are possible. For example, in an implementation, the network 220 can be an ad-hoc network and can omit one or more of the access points 210A, 210B. The computing and communications system 200 may include devices, units, or elements not shown in FIG. 2. For example, the computing and communications system 200 may include many more communicating devices, networks, and access points.

[0052] 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.

[0053] 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 moresegments, 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.

[0054] 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.

[0055] The encoder 400 can encode an input video stream 402, such as the video stream 300 shown in FIG. 3, to generate an encoded (compressed) bitstream 404. In some implementations, the encoder 400 may include a forward path for generating the compressed bitstream 404. The forward path may include an intra / inter prediction unit 410, a transform unit 420, a quantization unit 430, an entropy encoding unit 440, or any combination thereof. In some implementations, the encoder 400 may include a reconstruction path (indicated by the broken connection lines) to reconstruct a frame for encoding of further blocks. The reconstruction path may include a dequantization unit 450, an inverse transform unit 460, a reconstruction unit 470, a filtering unit 480, or any combination thereof. Other structural variations of the encoder 400 can be used to encode the video stream 402.

[0056] 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.

[0057] 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 fromsamples 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.

[0058] The intra / inter prediction unit 410 may subtract the prediction block from the current block (raw block) to produce a residual block. The transform unit 420 may perform a block-based transform, which may include transforming the residual block into transform coefficients in, for example, the frequency domain. Examples of block-based transforms include the Karhunen-Loeve Transform (KLT), the Discrete Cosine Transform (DCT), the Singular Value Decomposition Transform (SVD), and the Asymmetric Discrete Sine Transform (ADST). In an example, the DCT may include transforming a block into the frequency domain. The DCT may include using transform coefficient values based on spatial frequency, with the lowest frequency (i.e., DC) coefficient at the top-left of the matrix and the highest frequency coefficient at the bottom-right of the matrix.

[0059] The quantization unit 430 may convert the transform coefficients into discrete quantum values, which may be referred to as quantized transform coefficients or quantization levels. The quantized transform coefficients can be entropy encoded by the entropy encoding unit 440 to produce entropy-encoded coefficients. Entropy encoding can include using a probability distribution metric. The entropy-encoded coefficients and information used to decode the block, which may include the type of prediction used, motion vectors, and quantizer values, can be output to the compressed bitstream 404. The compressed bitstream 404 can be formatted using various techniques, such as run-length encoding (RLE) and zerorun coding.

[0060] 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 asblocking 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.

[0061] 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.

[0062] 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.

[0063] The decoder 500 may receive a compressed bitstream 502, such as the compressed bitstream 404 shown in FIG. 4, and may decode the compressed bitstream 502 to generate an output video stream 504. The decoder 500 may include an entropy decoding unit 510, a dequantization unit 520, an inverse transform unit 530, an intra / inter prediction unit 540, a reconstruction unit 550, a filtering unit 560, or any combination thereof. Other structural variations of the decoder 500 can be used to decode the compressed bitstream 502.

[0064] 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, theintra / 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.

[0065] Other variations of the decoder 500 can be used to decode the compressed bitstream 502. For example, the decoder 500 can produce the output video stream 504 without the deblocking filtering unit 560.

[0066] FIG. 6 is a block diagram of a representation of a portion 600 of a frame, such as the frame 330 shown in FIG. 3, in accordance with implementations of this disclosure. As shown, the portion 600 of the frame includes four 64x64 blocks 610, in two rows and two columns in a matrix or Cartesian plane. In some implementations, a 64x64 block may be a maximum coding unit, N=64. Each 64x64 block may include four 32x32 blocks 620. Each 32x32 block may include four 16x16 blocks 630. Each 16x16 block may include four 8x8 blocks 640. Each 8x8 block 640 may include four 4x4 blocks 650. Each 4x4 block 650 may include 16 pixels, which may be represented in four rows and four columns in each respective block in the Cartesian plane or matrix. The pixels may include information representing an image captured in the frame, such as luminance information, color information, and location information. In some implementations, a block, such as a 16x16 pixel block as shown, may include a luminance block 660, which may include luminance pixels 662; and two chrominance blocks 670, 680, such as a U or Cb chrominance block 670, and a V or Cr chrominance block 680. The chrominance blocks 670, 680 may include chrominance pixels 690. For example, the luminance block 660 may include 16x16 luminance pixels 662 and each chrominance block 670, 680 may include 8x8 chrominance pixels 690 as shown.Although one arrangement of blocks is shown, any arrangement may be used. Although FIG. 6 shows NxN blocks, in some implementations, NxM blocks may be used. For example, 32x64 blocks, 64x32 blocks, 16x32 blocks, 32x16 blocks, or any other size blocks may be used. In some implementations, Nx2N blocks, 2NxN blocks, or a combination thereof may be used.

[0067] 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 upperleft 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.

[0068] In some implementations, coding a block may include using quad-tree coding, which may include coding smaller block units within a block in raster- scan order. For example, the 64x64 block shown in the bottom left comer of the portion of the frame shown in FIG. 6, may be coded using quad-tree coding wherein the top left 32x32 block may be coded, then the top right 32x32 block may be coded, then the bottom left 32x32 block may be coded, and then the bottom right 32x32 block may be coded. Each 32x32 block may be coded using quad- tree coding wherein the top left 16x16 block may be coded, then the top right 16x16 block may be coded, then the bottom left 16x16 block may be coded, and then the bottom right 16x16 block may be coded. Each 16x16 block may be coded using quad- tree coding wherein the top left 8x8 block may be coded, then the top right 8x8 block may be coded, then the bottom left 8x8 block may be coded, and then the bottom right 8x8 block may be coded. Each 8x8 block may be coded using quad-tree coding wherein the top left 4x4 block may be coded, then the top right 4x4 block may be coded, then the bottom left 4x4 block may be coded, and then the bottom right 4x4 block may be coded. In some implementations, 8x8 blocks may be omitted for a 16x16 block, and the 16x16 block may be coded using quad-tree coding wherein the top left 4x4 block may be coded, then the other 4x4 blocks in the 16x16 block may be coded in raster- scan order.

[0069] 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.

[0070] 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 smallamount 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.

[0071] 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.

[0072] 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.

[0073] In some implementations, reducing temporal redundancy may include identifying a portion of a reference frame that corresponds to a current block or pixel of a current frame. For example, a reference frame, or a portion of a reference frame, which may be stored in memory, may be searched to identify a portion for generating a prediction to use for encoding a current block or pixel of the current frame with maximal efficiency. For example, the search may identify a portion of the reference frame for which the difference in pixel values between the current block and a prediction block generated based on the portion of the reference frame is minimized and may be referred to as motion searching. In some implementations, the portion of the reference frame searched may be limited. For example, the portion of the reference frame searched, which may be referred to as the search area, may include a limited number of rows of the reference frame. In an example, identifying the portion of the reference frame for generating a prediction may include calculating a cost function, such as a sum of absolute differences (SAD), between the pixels of portions of the search area and thepixels of the current block.

[0074] 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.

[0075] Although described herein with reference to matrix or Cartesian representation of a frame for clarity, a frame may be stored, transmitted, processed, or any combination thereof, in any data structure such that pixel values may be efficiently represented for a frame or image. For example, a frame may be stored, transmitted, processed, or any combination thereof, in a two-dimensional data structure such as a matrix as shown, or in a onedimensional data structure, such as a vector array. In an implementation, a representation of the frame, such as a two-dimensional representation as shown, may correspond to a physical location in a rendering of the frame as an image. For example, a location in the top left corner of a block in the top left comer of the frame may correspond with a physical location in the top left corner of a rendering of the frame as an image.

[0076] 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 andselecting the best scheme, such as the scheme that produces the least rate-distortion error.

[0077] 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.

[0078] In some implementations, video coding for a current block may include identifying an optimal prediction coding mode from multiple candidate prediction coding modes, which may provide flexibility in handling video signals with various statistical properties and may improve the compression efficiency. For example, a video coder may evaluate each candidate prediction coding mode to identify the optimal prediction coding mode, which may be, for example, the prediction coding mode that minimizes an error metric, such as a rate-distortion cost, for the current block. In some implementations, the complexity of searching the candidate prediction coding modes may be reduced by limiting the set of available candidate prediction coding modes based on similarities between the current block and a corresponding prediction block. In some implementations, the complexity of searching each candidate prediction coding mode may be reduced by performing a directed refinement mode search. For example, metrics may be generated for a limited set of candidate block sizes, such as 16x16, 8x8, and 4x4, the error metric associated with each block size may be in descending order, and additional candidate block sizes, such as 4x8 and 8x4 block sizes, may be evaluated.

[0079] 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.

[0080] 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 2564x4 transform blocks.

[0081] In some implementations, video coding, such as video coding using transform partitioning, may include identifying multiple transform block sizes for a residual block using multiform transform partition coding. In some implementations, multiform transform partition coding may include recursively determining whether to transform a current block using a current block size transform or by partitioning the current block and multiform transform partition coding each partition. For example, the bottom left block 610 shown in FIG. 6 may be a 64x64 residual block, and multiform transform partition coding may include determining whether to code the current 64x64 residual block using a 64x64 transform or to code the 64x64 residual block by partitioning the 64x64 residual block into partitions, such as four 32x32 blocks 620, and multiform transform partition coding each partition. In some implementations, determining whether to transform partition the current block may be based on comparing a cost for encoding the current block using a current block size transform to a sum of costs for encoding each partition using partition size transforms.

[0082] FIG. 7 is a diagram of an example of a restoration filter 700 in accordance with implementations of this disclosure. The restoration filter 700 may be implemented by an encoder, such as the encoder 400 shown in FIG. 4. The restoration filter 700 may be implemented by a decoder, such as the decoder 500 shown in FIG. 5.

[0083] For example, the restoration filter 700 may be a Wiener filter. Filtering a frame, or a restoration unit thereof, using the restoration filter 700 includes filtering pixel values of the frame, or restoration unit, using a two-dimensional linear filter. The restoration filter 700 is shown in FIG. 7 as having a diamond shape centered on the current pixel 710 being filtered. Other shapes, such as star or square, may be used.

[0084] FIG. 8 is a diagram of an example of restoration filtering classes subsets 800 inaccordance with implementations of this disclosure. The restoration filtering classes subsets 800 may be implemented by an encoder, such as the encoder 400 shown in FIG. 4. The restoration filtering classes subsets 800 may be implemented by a decoder, such as the decoder 500 shown in FIG. 5.

[0085] The restoration filtering classes subsets 800 includes ten (10) subsets (S) of sixteen classes for classifying pixels, or classification group of pixels, wherein a classification group of pixels includes a block, such as a 4x4 block, of pixels.

[0086] The restoration filtering classes subsets 800 include a fist subset (So) 802, a second subset (Si) 812, a third subset (S2) 822, a fourth subset (S3) 832, a fifth subset (S4) 842, a sixth subset (S5) 852, a seventh subset (Sg) 862, an eighth subset (S7) 872, a ninth subset (Sg) 882, and a tenth subset (S9) 892.

[0087] The fist subset (So) 802 includes a first restoration filtering class (0), a second restoration filtering class (1), a third restoration filtering class (2), a fourth restoration filtering class (3), a fifth restoration filtering class (4), a sixth restoration filtering class (5), a seventh restoration filtering class (6), an eighth restoration filtering class (7), a ninth restoration filtering class (8), a tenth restoration filtering class (9), an eleventh restoration filtering class (10), a twelfth restoration filtering class (11), a thirteenth restoration filtering class (12), a fourteenth restoration filtering class (13), a fifteenth restoration filtering class (14), and a sixteenth restoration filtering class (15).

[0088] The second subset (Si) 812 includes the first restoration filtering class (0), the second restoration filtering class (1), the fifth restoration filtering class (4), the seventh restoration filtering class (6), and the twelfth restoration filtering class (11).

[0089] The third subset (S2) 822 includes the third restoration filtering class (2), the sixth restoration filtering class (5), the eighth restoration filtering class (7), the fourteenth restoration filtering class (13), and the sixteenth restoration filtering class (15).

[0090] The fourth subset (S3) 832 includes the fourth restoration filtering class (3), the ninth restoration filtering class (8), the tenth restoration filtering class (9), and the thirteenth restoration filtering class (12).

[0091] The fifth subset (S4) 842 includes the first restoration filtering class (0), the ninth restoration filtering class (8), and the twelfth restoration filtering class (11).

[0092] The sixth subset (S5) 852 includes the fifth restoration filtering class (4), the thirteenth restoration filtering class (12), and the fourteenth restoration filtering class (13).

[0093] The seventh subset (Sg) 862 includes the third restoration filtering class (2), the seventh restoration filtering class (6), and the sixteenth restoration filtering class (15).

[0094] The eighth subset (S7) 872 includes the second restoration filtering class (1), the sixth restoration filtering class (5), the tenth restoration filtering class (9), and the eleventh restoration filtering class (10).

[0095] The ninth subset (Sg) 882 includes the fifth restoration filtering class (4), the tenth restoration filtering class (9), the eleventh restoration filtering class (10), the twelfth restoration filtering class (11), and the fifteenth restoration filtering class (14).

[0096] The tenth subset (S9) 892 includes the fourth restoration filtering class (3), the eighth restoration filtering class (7), and the fifteenth restoration filtering class (14).

[0097] FIG. 9 is a diagram of an example of hierarchical restoration filtering classes subsets 900 in accordance with implementations of this disclosure. The hierarchical restoration filtering classes subsets 900 may be implemented by an encoder, such as the encoder 400 shown in FIG. 4. The hierarchical restoration filtering classes subsets 900 may be implemented by a decoder, such as the decoder 500 shown in FIG. 5.

[0098] The hierarchical restoration filtering classes subsets 900 includes ten (10) subsets (S) of sixteen hierarchical classes for classifying pixels, or classification group of pixels, wherein a classification group of pixels includes a block, such as a 4x4 block, of pixels, arranged in a tree structure wherein a respective subset corresponds to a respective node of the tree.

[0099] The hierarchical restoration filtering classes subsets 900 include a fist subset (So) 902, a second subset (Si) 912, a third subset (S2) 922, a fourth subset (S3) 932, a fifth subset (S4) 942, a sixth subset (S5) 952, a seventh subset (Se) 962, an eighth subset (S7) 972, a ninth subset (Sg) 982, and a tenth subset (S9) 992.

[0100] The fist subset (So) 902 corresponds to the root node of the tree (root hierarchical restoration filtering class). The fist subset (So) 902 includes a first restoration filtering class (0), a second restoration filtering class (1), a third restoration filtering class (2), a fourth restoration filtering class (3), a fifth restoration filtering class (4), a sixth restoration filtering class (5), a seventh restoration filtering class (6), an eighth restoration filtering class (7), a ninth restoration filtering class (8), a tenth restoration filtering class (9), an eleventh restoration filtering class (10), a twelfth restoration filtering class (11), a thirteenth restoration filtering class (12), a fourteenth restoration filtering class (13), a fifteenth restoration filteringclass (14), and a sixteenth restoration filtering class (15).

[0101] The second subset (Si) 912 depends from, and is a proper subset of, the fist subset(So) 902. The second subset (Si) 912 includes the first restoration filtering class (0), the second restoration filtering class (1), the fifth restoration filtering class (4), the seventh restoration filtering class (6), the twelfth restoration filtering class (11), and the fifteenth restoration filtering class (14).

[0102] The third subset (S2) 922 depends from, and is a proper subset of, the fist subset (So) 902. The third subset (S2) 922 includes the third restoration filtering class (2), the sixth restoration filtering class (5), the eighth restoration filtering class (7), the fourteenth restoration filtering class (13), and the sixteenth restoration filtering class (15).

[0103] The fourth subset (S3) 932 depends from, and is a proper subset of, the fist subset(50) 902. The fourth subset (S3) 932 includes the fourth restoration filtering class (3), the ninth restoration filtering class (8), the tenth restoration filtering class (9), the eleventh restoration filtering class (10), and the thirteenth restoration filtering class (12).

[0104] The fifth subset (S4) 942 depends from, and is a proper subset of, the second subset(51) 912. The fifth subset (S4) 942 includes the fifth restoration filtering class (4), the twelfth restoration filtering class (11), and the fifteenth restoration filtering class (14).

[0105] The sixth subset (S5) 952 depends from, and is a proper subset of, the second subset (Si) 912. The sixth subset (S5) 952 includes the first restoration filtering class (0), the second restoration filtering class (1), and the seventh restoration filtering class (6).

[0106] The seventh subset (Sg) 962 depends from, and is a proper subset of, the third subset (S2) 922. The seventh subset (Sg) 962 includes the third restoration filtering class (2), the eighth restoration filtering class (7), and the sixteenth restoration filtering class (15).

[0107] The eighth subset (S7) 972 depends from, and is a proper subset of, the third subset(52) 922. The eighth subset (S7) 972 includes the sixth restoration filtering class (5), and the fourteenth restoration filtering class (13).

[0108] The ninth subset (Sg) 982 depends from, and is a proper subset of, the fourth subset(53) 932. The ninth subset (Sg) 982 includes the fourth restoration filtering class (3), and the eleventh restoration filtering class (10).

[0109] The tenth subset (S9) 992 depends from, and is a proper subset of, the fourth subset (S3) 932. The tenth subset (S9) 992 includes the ninth restoration filtering class (8), the tenthrestoration filtering class (9), and the thirteenth restoration filtering class (12).

[0110] A respective subset (Si) from the subsets (S) may be coded, or signaled, using a corresponding subset index value obtained from the root node of the tree, corresponding to the fist subset (So) 902, down to the node corresponding to the respective subset (Si).

[0111] FIG. 10 is a diagram of an example of binary symmetrical hierarchical restoration filtering classes subsets 1000 in accordance with implementations of this disclosure. The binary symmetrical hierarchical restoration filtering classes subsets 1000 may be implemented by an encoder, such as the encoder 400 shown in FIG. 4. The binary symmetrical hierarchical restoration filtering classes subsets 1000 may be implemented by a decoder, such as the decoder 500 shown in FIG. 5.

[0112] The binary symmetrical hierarchical restoration filtering classes subsets 1000 include fifteen (15) subsets (S) of sixteen hierarchical classes for classifying pixels, or classification group of pixels, wherein a classification group of pixels includes a block, such as a 4x4 block, of pixels, arranged in a tree structure wherein a respective subset corresponds to a respective node of the tree.

[0113] The binary symmetrical hierarchical restoration filtering classes subsets 1000 include a fist subset (So) 1010, a second subset (Si) 1020, a third subset (S2) 1022, a fourth subset (S3) 1030, a fifth subset (S4) 1032, a sixth subset (S5) 1034, a seventh subset (Sg) 1036, an eighth subset (S7) 1040, a ninth subset (Sg) 1042, a tenth subset (S9) 1044, an eleventh subset (S10) 1046, a twelfth subset (S11) 1050, a thirteenth subset (S12) 1052, a fourteenth subset (S13) 1054, and a fifteenth subset (S14) 1056.

[0114] The fist subset (So) 1010 corresponds to the root node of the tree. The fist subset (So) 1010 includes a first restoration filtering class (0), a second restoration filtering class (1), a third restoration filtering class (2), a fourth restoration filtering class (3), a fifth restoration filtering class (4), a sixth restoration filtering class (5), a seventh restoration filtering class (6), an eighth restoration filtering class (7), a ninth restoration filtering class (8), a tenth restoration filtering class (9), an eleventh restoration filtering class (10), a twelfth restoration filtering class (11), a thirteenth restoration filtering class (12), a fourteenth restoration filtering class (13), a fifteenth restoration filtering class (14), and a sixteenth restoration filtering class (15).

[0115] The second subset (Si) 1020 depends from, and is a proper subset of, the fist subset (So) 1010. The second subset (Si) 1020 includes the first restoration filtering class (0),the second restoration filtering class (1), the third restoration filtering class (2), the fourth restoration filtering class (3), the fifth restoration filtering class (4), the sixth restoration filtering class (5), the seventh restoration filtering class (6), and the eighth restoration filtering class (7).

[0116] The third subset (S2) 1022 depends from, and is a proper subset of, the fist subset (So) 1010. The third subset (S2) 1022 includes the ninth restoration filtering class (8), the tenth restoration filtering class (9), the eleventh restoration filtering class (10), the twelfth restoration filtering class (11), the thirteenth restoration filtering class (12), the fourteenth restoration filtering class (13), the fifteenth restoration filtering class (14), and the sixteenth restoration filtering class (15).

[0117] The fourth subset (S3) 1030 depends from, and is a proper subset of, the second subset (Si) 1020. The fourth subset (S3) 1030 includes the first restoration filtering class (0), the second restoration filtering class (1), the third restoration filtering class (2), and the fourth restoration filtering class (3).

[0118] The fifth subset (S4) 1032 depends from, and is a proper subset of, the second subset (Si) 1020. The fifth subset (S4) 1032 includes the fifth restoration filtering class (4), the sixth restoration filtering class (5), the seventh restoration filtering class (6), and the eighth restoration filtering class (7).

[0119] The sixth subset (S5) 1034 depends from, and is a proper subset of, the third subset (S2) 1022. The sixth subset (S5) 1034 includes the ninth restoration filtering class (8), the tenth restoration filtering class (9), the eleventh restoration filtering class (10), and the twelfth restoration filtering class (11).

[0120] The seventh subset (Sg) 1036 depends from, and is a proper subset of, the third subset (S2) 1022. The seventh subset (Sg) 1036 includes the thirteenth restoration filtering class (12), the fourteenth restoration filtering class (13), the fifteenth restoration filtering class (14), and the sixteenth restoration filtering class (15).

[0121] The eighth subset (S7) 1040 depends from, and is a proper subset of, the fourth subset (S3) 1030. The eighth subset (S7) 1040 includes the first restoration filtering class (0), and the second restoration filtering class (1).

[0122] The ninth subset (Sg) 1042 depends from, and is a proper subset of, the fourth subset (S3) 1030. The ninth subset (Sg) 1042 includes the third restoration filtering class (2),and the fourth restoration filtering class (3).

[0123] The tenth subset (S9) 1044 depends from, and is a proper subset of, the fifth subset (S4) 1032. The tenth subset (S9) 1044 includes the fifth restoration filtering class (4), and the sixth restoration filtering class (5).

[0124] The eleventh subset (S 10) 1046 depends from, and is a proper subset of, the fifth subset (S4) 1032. The fourth subset (S3) 1030 includes the seventh restoration filtering class (6), and the eighth restoration filtering class (7).

[0125] The twelfth subset (S11) 1050 depends from, and is a proper subset of, the sixth subset (S5) 1034. twelfth subset (S11) 1050 includes the ninth restoration filtering class (8), and the tenth restoration filtering class (9).

[0126] The thirteenth subset (S 12) 1052 depends from, and is a proper subset of, the sixth subset (S5) 1034. The thirteenth subset (S12) 1052 includes the eleventh restoration filtering class (10), and the twelfth restoration filtering class (11).

[0127] The fourteenth subset (S13) 1054 depends from, and is a proper subset of, the seventh subset (Sg) 1036. The fourteenth subset (S13) 1054 includes the thirteenth restoration filtering class (12), and the fourteenth restoration filtering class (13).

[0128] The fifteenth subset (S14) 1056 depends from, and is a proper subset of, the seventh subset (Sg) 1036. The fifteenth subset (S14) 1056 includes the fifteenth restoration filtering class (14), and the sixteenth restoration filtering class (15).

[0129] A respective subset (Si) from the subsets (S) may be coded, or signaled, using data, such as bits, encoded in accordance with a binary encoding scheme from the root node of the tree, corresponding to the fist subset (So) 1010, down to the node corresponding to the respective subset (Si).

[0130] FIG. 11 is a flowchart diagram of an example of decoding using multi-class restoration filtering 1100 in accordance with implementations of this disclosure. Decoding using multi-class restoration filtering 1100 may be implemented in a decoder, such as the decoder 500 shown in FIG. 5. Decoding using multi-class restoration filtering 1100 includes block-based hybrid video coding as described herein.

[0131] Decoding using multi-class restoration filtering 1100 includes generating reconstructed video data by decoding an encoded bitstream, such as the compressed bitstream 502 shown in FIG. 5, or one or more portions thereof, to generate a reconstructed video, or aportion thereof, such as the output video stream 504 shown in FIG. 5.

[0132] Decoding the encoded bitstream, or one or more portions thereof, for decoding using multi-class restoration filtering 1100, includes obtaining decoded fame data (at 1110), obtaining reconstructed frame data including restoration filtering (at 1120), and outputting reconstructed frame data (at 1130). One or more aspects of decoding using multi-class restoration filtering 1100 may be omitted from the description herein for simplicity and brevity.

[0133] Obtaining the decoded fame data (at 1110) for a current frame includes obtaining an encoded bitstream, or a portion thereof. 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 encoded bitstream, or the portion thereof. Obtaining the decoded fame data (at 1110) includes identifying a current frame, such as from a current sequence of frames, to decode from the encoded bitstream to generate the decoded fame data for the current frame. Obtaining the decoded fame data (at 1110) includes obtaining the decoded fame data by decoding data from the encoded bitstream. For example, on a per-block basis for the current frame, the decoder may entropy decode quantized transform coefficients for a current block of the current frame, such as shown (at 510) in FIG. 5, dequantize the quantized transform coefficients for the current block to obtain transform coefficients for the current block, such as shown (at 520) in FIG. 5, inverse transform the transform coefficients for the current block to obtain residual data for the current block, such as shown (at 530) in FIG. 5, obtain prediction block data for the current block, such as shown (at 540) in FIG. 5, obtain the decoded block data for the current block by combining, such as adding, the prediction block data for the current block and the residual data for the current block, and include the decoded block data for the current block in the decoded frame data.

[0134] Obtaining reconstructed frame data (at 1120) includes restoration filtering the decoded fame data for the current frame. Restoration filtering the decoded fame data for the current frame includes identifying a current restoration unit of the current frame (at 1140), obtaining a reference restoration filter (RRF) identifier (at 1142), obtaining a current reference restoration filter parameters superset (at 1144), obtaining a reference restoration filter modification flag (at 1146), determining whether the reference restoration filter modification flag indicates modification of the current reference restoration filter parameters superset (at 1148), obtaining a restoration filtering classes subset identifier (at 1150), obtaining a current restoration filtering classes subset (Si) (at 1152), obtaining a reference- l-restoration filter modification type flag (at 1154), determining whether the reference restoration filter modification type flag indicates a modification of the reference restoration filter parameters of the current restoration filtering classes subset (Si) in accordance with defined parameters (at 1156), obtaining signaled modification data (at 1158), obtaining modified restoration filter parameters (at 1160), and obtaining a filtered restoration unit (at 1162).

[0135] One or more restoration units are defined, or determined, for the current frame. A restoration unit, or loop restoration unit (LRU), is a rectangular portion of a frame, such as a 64x64 block of the frame, a 128x128 block of the frame, or a 256x256 block of the frame, on which restoration filtering is performed. In some implementations, a frame may include one restoration unit having a size of the frame. In some implementations, a frame may include multiple, non-overlapping, restoration units respectively having a size smaller than the size of the frame. Restoration units are distinct from, and may be defined or determined separately from, other blocks of the frame as described herein, such as prediction blocks, coding blocks, residual blocks, transform blocks, macroblocks, segments, slices, tiles, or superblocks.

[0136] The current restoration unit of the current frame is obtained, selected, or otherwise identified (at 1140). Although not shown expressly in FIG. 11, restoration filtering (at 1110) is performed on a per-restoration unit basis for the current frame. For frames including multiple restoration units, the restoration units may be restoration filtered in a defined order, or sequence, such as in raster scan order. The current restoration unit includes decoded, or partially reconstructed, pixel values for the respective portion of the current frame.

[0137] Although not expressly shown in FIG. 11, obtaining the reconstructed frame data (at 1120), or identifying the current restoration unit (at 1140), includes classifying pixels from the decoded frame data into a defined set of classes (restoration filtering classes), such as on a per-pixel basis or on a per-classification group of pixels basis, wherein a classification group of pixels includes a block, such as a 4x4 block, of pixels, such as based on edge strength for a respective pixel or classification group of pixels, directionality of the edge for the respective pixel classification group of pixels, or a combination thereof. The defined set of classes includes a defined number, count, or cardinality, (C) of classes, such as four classes or sixteen classes. Other sizes may be used for the classification group of pixels. Other classes may be used.

[0138] Decoding using multi-class restoration filtering 1100 includes the decoder obtaining, maintaining, or both, a dynamic reference restoration filters buffer, or index, forthe current frame. The dynamic reference restoration filters buffer includes one or more supersets (sets of sets) of reference restoration filter parameters (reference restoration filter parameters supersets) previously used, by the decoder, for restoration filtering a reference frame, a restoration unit, other than the current restoration unit, of the current frame, or both.

[0139] In some implementations, the dynamic reference restoration filters buffer has a defined maximum size (P), indicating a maximum number, count, or cardinality, of reference restoration filter parameters supersets included in the dynamic reference restoration filters buffer.

[0140] The reference restoration filter parameters superset identifier is obtained (at 1142). To obtain the reference restoration filter parameters superset identifier the decoder decodes, receives, reads, obtains, extracts, or otherwise accesses, the reference restoration filter parameters superset identifier for the current restoration unit from the encoded bitstream. The reference restoration filter parameters superset identifier is a value, such as an integer value, in a defined range, defined in accordance with the defined maximum size (P) of the dynamic reference restoration filters buffer, plus one (1), such as the range [0...P]. A reference restoration filter parameters superset identifier in the range [0-P-1] indicates a reference restoration filter parameters superset included in the dynamic reference restoration filters buffer. A reference restoration filter parameters superset identifier of P indicates a defined, trained, or both, such as prior to and independent of decoding the current frame or video, reference restoration filter parameters superset.

[0141] A respective reference restoration filter parameters superset includes, on a per-class basis with respect to the defined set of restoration filtering classes, a respective reference restoration filter parameters set.

[0142] A respective restoration filter parameters set, such as for a respective restoration filtering class, defines or describes a respective restoration filter. A restoration filter has a filter type, such as Wiener filter, which is a two-dimensional (2D) linear filter. A restoration filter has a filter shape, such as a diamond shape as shown in FIG. 7. A restoration filter has a size, indicating a number, count, or cardinality, of coefficients, or weights, for the restoration filter. A restoration filter has a coefficient set, indicating respective coefficient values for the filter.

[0143] The decoder obtains the current reference restoration filter parameters superset (at 1144) in accordance with the reference restoration filter parameters superset identifier. For a reference restoration filter parameters superset identifier in the range [0-P-1], the decoder obtains, as the current reference restoration filter parameters superset, the referencerestoration filter parameters superset included in the dynamic reference restoration filters buffer in accordance with the reference restoration filter parameters superset identifier. For a reference restoration filter parameters superset identifier of P, the decoder obtains, as the current reference restoration filter parameters superset, the defined, trained, or both, reference restoration filter parameters superset. In some implementations, a value of the reference restoration filter parameters superset identifier other than P+1 may be associated with the defined, trained, or both, reference restoration filter parameters superset. In some implementations, the defined, trained, or both, reference restoration filter parameters superset may be included in the dynamic reference restoration filters buffer, wherein the maximum size of the dynamic reference restoration filters buffer is P+1.

[0144] A reference restoration filter modification flag is obtained (at 1146). To obtain the reference restoration filter modification flag, the decoder decodes, extracts, receives, reads, obtains, or otherwise accesses, the reference restoration filter modification flag from the encoded bitstream. For example, the reference restoration filter modification flag may be a bit, binary value, or symbol.

[0145] Whether the reference restoration filter modification flag indicates modification of the current reference restoration filter parameters superset, or one or more portions thereof, is determined (at 1148). A first value of the reference restoration filter modification flag, such as zero (0) (NO), indicates the omission or exclusion of modifying one or more of the parameters of the current reference restoration filter parameters superset. A second value of the reference restoration filter modification flag, such as one (1) (YES), indicates a modification of one or more of the parameters of the current reference restoration filter parameters superset.

[0146] In some implementations, the reference restoration filter modification flag indicates the omission or exclusion of modifying one or more of the parameters of the current reference restoration filter parameters superset (NO) and obtaining a restoration filtering classes subset identifier (at 1150), obtaining a current restoration filtering classes subset (Si) (at 1152), obtaining a reference restoration filter modification type flag (at 1154), determining whether the reference restoration filter modification type flag indicates modification of the reference restoration filter parameters of the current restoration filtering classes subset (Si) in accordance with defined parameters (at 1156), obtaining signaled modification data (at 1158), and obtaining modified restoration filter parameters (at 1160), is skipped, excluded, or otherwise omitted for the current restoration unit.

[0147] In some implementations, the reference restoration filter modification flag indicates modification of one or more of the parameters of the current reference restoration filter parameters superset (YES) and a restoration filtering (RF) classes subset identifier is obtained (at 1150). For example, the restoration filtering classes subset identifier may be obtained in response to determining (at 1148) that the reference restoration filter modification flag indicates modification of the current reference restoration filter parameters superset. To obtain the restoration filtering classes subset identifier, the decoder decodes, extracts, receives, reads, obtains, or otherwise accesses, the restoration filtering classes subset identifier from the encoded bitstream.

[0148] The defined set of restoration filtering classes (C) may be expressed as S = {0, 1, 2, ..., C-l }. A defined number, count, or cardinality, (K), such as ten ( / Y= 10), of defined restoration filtering classes subsets (So, Si, ..., Sk-t) of the restoration filtering classes (C) may be defined. A restoration filtering classes subset (Si) is a subset (S5) of the defined set of classes (S). In some implementations, the restoration filtering classes subsets overlap. Examples of restoration filtering classes subsets are shown in FIGS. 8-10.

[0149] In some implementations, such as for the restoration filtering classes subsets shown in FIG. 8, to obtain the restoration filtering classes subset identifier the decoder may extract, receive, read, obtain, or otherwise access, the restoration filtering classes subset identifier from the encoded bitstream as an integer value, which may be an index value, wherein a respective integer value of the restoration filtering classes subset identifier indicates or identifies a respective restoration filtering classes subset from the restoration filtering classes subsets.

[0150] In some implementations, such as for the restoration filtering classes subsets shown in FIG. 9, to obtain the restoration filtering classes subset identifier the decoder may extract, receive, read, obtain, or otherwise access, from the encoded bitstream zero or more restoration filtering classes subset branch identifiers, such as an ordered sequence of zero or more restoration filtering classes subset branch identifiers and the restoration filtering classes subset identifier is identified, determined, or obtained in accordance with the zero or more restoration filtering classes subset branch identifiers.

[0151] Obtaining the restoration filtering classes subset identifier in accordance with the zero or more restoration filtering classes subset branch identifiers may include traversing the hierarchy of restoration filtering classes subsets in accordance with the zero or more restoration filtering classes subset branch identifiers to obtain the restoration filtering classessubset identifier.

[0152] For example, in response to the absence, or unavailability, of restoration filtering classes subset branch identifiers (zero restoration filtering classes subset branch identifiers) from the encoded bitstream, the restoration filtering classes subset identifier of the root hierarchical restoration filtering class from the hierarchical restoration filtering classes subsets, such as shown (at 902) in FIG. 9, is identified as the restoration filtering classes subset identifier.

[0153] In another example, in response to a sequentially first restoration filtering classes subset branch identifier from the encoded bitstream and in response to the absence, or unavailability, of subsequent restoration filtering classes subset branch identifiers from the encoded bitstream, the restoration filtering classes subset identifier corresponding to a branch of the hierarchical restoration filtering classes subsets indicated by the sequentially first restoration filtering classes subset branch identifier is identified as the restoration filtering classes subset identifier. For example, a first value of the sequentially first restoration filtering classes subset branch identifier, such as zero (0), may indicate a first branch, such as the second restoration filtering classes subset shown (at 912) in FIG. 9, a second value of the sequentially first restoration filtering classes subset branch identifier, such as one (1), may indicate a second branch, such as the third restoration filtering classes subset shown (at 922) in FIG. 9, and a third value of the sequentially first restoration filtering classes subset branch identifier, such as two (2), may indicate a third branch, such as the fourth restoration filtering classes subset shown (at 932) in FIG. 9.

[0154] In another example, in response to a sequentially first restoration filtering classes subset branch identifier from the encoded bitstream having the second value (1) indicating the third restoration filtering classes subset shown (at 922) in FIG. 9, in response to a sequentially second restoration filtering classes subset branch identifier from the encoded bitstream having the first value (0) indicating the seventh restoration filtering classes subset shown (at 962) in FIG. 9, and in response to the absence, or unavailability, of subsequent restoration filtering classes subset branch identifiers from the encoded bitstream, the restoration filtering classes subset identifier corresponding to the seventh restoration filtering classes subset shown (at 962) in FIG. 9 is identified as the restoration filtering classes subset identifier.

[0155] In some implementations, such as for the restoration filtering classes subsets shown in FIG. 10, to obtain the restoration filtering classes subset identifier the decoder may extract, receive, read, obtain, or otherwise access, from the encoded bitstream zero or more binaryrestoration filtering classes subset branch identifiers.

[0156] For example, in response to a sequentially first binary restoration filtering classes subset branch identifier from the encoded bitstream having the first value (0) indicating the first binary symmetrical hierarchical restoration filtering classes subset shown (at 1020) in FIG. 10, in response to a sequentially second binary restoration filtering classes subset branch identifier from the encoded bitstream having the first value (0) indicating the third binary symmetrical hierarchical restoration filtering classes subset shown (at 1030) in FIG. 10, and in response to a sequentially third binary restoration filtering classes subset branch identifier from the encoded bitstream having the second value (1) indicating the ninth binary symmetrical hierarchical restoration filtering classes subset shown (at 1042) in FIG. 10, the restoration filtering classes subset identifier corresponding to the ninth binary symmetrical hierarchical restoration filtering classes subset shown (at 1042) in FIG. 10 is identified as the restoration filtering classes subset identifier.

[0157] The restoration filtering classes subset identifier (z) indicates a restoration filtering classes subset from the restoration filtering classes subsets (S). For example, the restoration filtering classes subset identifier (z) may be a value in a defined range, such as [0-K-1] (t G {0, 1, — 1}). In some implementations, the restoration filtering classes subsets may include a restoration filtering classes subset (Si) and a compliment restoration filtering classes subset (S-Si). In some implementations, whether to identify a subset (Si) or the corresponding compliment subset (S-Si) may be indicated, or signaled, by a flag, bit, or other binary value, in the encoded bitstream.

[0158] The current restoration filtering classes subset (Si) is obtained (at 1152) from the restoration filtering classes subsets in accordance with the restoration filtering classes subset identifier.

[0159] The reference restoration filter modification type flag is obtained (at 1154) for the current restoration filtering classes subset (Si). To obtain the reference restoration filter modification type flag, the decoder decodes, extracts, receives, reads, obtains, or otherwise accesses, the reference restoration filter modification type flag from the encoded bitstream. For example, the reference restoration filter modification type flag may be a bit, binary value, or symbol.

[0160] Whether the reference restoration filter modification type flag indicates modification, such as modification of one or more parameters of the restoration filtering classes subset (Si), in accordance with defined parameters, such as defined parameters fromthe defined reference restoration filter parameters superset, or in accordance with signaled modification data, is determined (at 1156). For example, a first value of the reference restoration filter modification type flag may indicate modification in accordance with the defined reference restoration filter parameters superset. A second value of the reference restoration filter modification type flag may indicate modification in accordance with signaled modification data.

[0161] In some implementations, signaled modification data (signaled restoration filter parameters modification data) is obtained (at 1158), such as in response to a determination (at 1156) that the reference restoration filter modification type flag indicates modification in accordance with signaled modification data. To obtain the signaled modification data, the decoder decodes, extracts, receives, reads, obtains, or otherwise accesses, the signaled modification data from the encoded bitstream.

[0162] In some implementations, obtaining the signaled modification data includes obtaining, from the encoded bitstream, a, such as one, set of signaled modification parameters, or coefficients, for updating the respective restoration filtering classes from the current restoration filtering classes subset (Si) (obtained at 1152).

[0163] In some implementations, obtaining the signaled modification data includes obtaining, from the encoded bitstream, differentially coded modification data, such as differential restoration filter parameters. An example of coding restoration filter modification data, such as to obtain differentially coded modification data, is shown in FIG. 12.

[0164] Modified restoration filter parameters are obtained (at 1160) for the current restoration filtering classes subset (Si) (obtained at 1152). Obtaining the modified restoration filter parameters for the current restoration filtering classes subset (Si) includes obtaining, such as on a per-class basis with respect to the current restoration filtering classes subset (Si), modified restoration filter parameters.

[0165] In some implementations, in response to a determination (at 1156) that the reference restoration filter modification type flag indicates modification in accordance with the defined reference restoration filter parameters superset, the parameters from the defined, or trained, reference restoration filter parameters superset corresponding to the current restoration filtering classes subset (Si) are obtained, or used, as the modified restoration filter parameters for the restoration filtering classes of the current restoration filtering classes subset (Si).

[0166] In some implementations, in response to a determination (at 1156) that thereference restoration filter modification type flag indicates a modification of the parameters of the current restoration filtering classes subset (Si) (obtained at 1152) in accordance with signaled modification data (obtained at 1158), the parameters from the current restoration filtering classes subset (Si) (obtained at 1152) are modified in accordance with the signaled modification data (obtained at 1158) to obtain the modified restoration filter parameters for the current restoration filtering classes subset (Si).

[0167] Obtaining a reference restoration filter modification flag (at 1146), determining whether the reference restoration filter modification flag indicates a modification of the current reference restoration filter parameters superset (at 1148), obtaining a restoration filtering classes subset identifier (at 1150), obtaining a current restoration filtering classes subset (Si) (at 1152), obtaining a reference restoration filter modification type flag (at 1154), determining whether the reference restoration filter modification type flag indicates a modification of the reference restoration filter parameters of the current restoration filtering classes subset (Si) in accordance with defined parameters (at 1156), obtaining signaled modification data (at 1158), and obtaining modified restoration filter parameters (at 1160), may be performed for one or more restoration filtering classes subsets as indicated by the directional line (at 1161) from obtaining modified restoration filter parameters (at 1160) to obtaining the reference restoration filter modification flag (at 1146).

[0168] The decoder includes the modified restoration filter parameters for the current restoration filtering classes subset (Si) in the current reference restoration filter parameters superset (updating the current reference restoration filter parameters superset in accordance with the modified restoration filter parameters), which may include replacing the restoration filter parameters for the current restoration filtering classes subset (Si) previously included in the current reference restoration filter parameters superset.

[0169] The decoder includes the current reference restoration filter parameters superset for the current restoration unit in the dynamic reference restoration filters buffer. In some implementations, the decoder includes the current reference restoration filter parameters superset for the current restoration unit in the dynamic reference restoration filters buffer in response to a determination that the current reference restoration filter parameters superset is unavailable from the dynamic reference restoration filters buffer. In some implementations, the decoder may omit including the current reference restoration filter parameters superset for the current restoration unit in the dynamic reference restoration filters buffer in response to adetermination that the current reference restoration filter parameters superset matches, or is available, a refence restoration filter parameters superset from the dynamic reference restoration filters buffer. Including the current reference restoration filter parameters superset for the current restoration unit in the dynamic reference restoration filters buffer may include removing a restoration filter parameters superset, such as a sequentially oldest restoration filter parameters superset, from the dynamic reference restoration filters buffer.

[0170] The filtered restoration unit is obtained (at 1162). For example, the filtered restoration unit may be obtained in response to a determination (at 1148) that the reference restoration filter modification flag indicates the absence, omission, or exclusion, of a modification, other than a previously performed modification with respect to the current restoration unit, of one or more of the parameters of the current reference restoration filter parameters superset.

[0171] Obtaining the filtered restoration unit includes restoration filtering the restoration unit using restoration filter parameters indicated by the current reference restoration filter parameters superset.

[0172] Restoration filtering (at 1110) may be performed on a per-restoration unit basis for the restoration units of the current frame, as indicated by the broken directional line (at 1163) from obtaining the filtered restoration unit (at 1162) to obtaining the current restoration unit (at 1146).

[0173] The decoder outputs the reconstructed image or video data (at 1130). To output the reconstructed image or video data, the decoder includes the filtered restoration unit in the reconstructed frame data for the current frame and outputs the reconstructed frame data for the current frame. For example, the decoder may send, transmit, or otherwise make available, the reconstructed frame data for presentation to a user. In another example, the decoder may write, store, record, or otherwise save, the reconstructed frame data.

[0174] FIG. 12 is a diagram of an example of coding restoration filter modification data 1200 in accordance with implementations of this disclosure. Coding restoration filter modification data 1200 may be implemented by an encoder, such as the encoder 400 shown in FIG. 4. Coding restoration filter modification data 1200 may be implemented by a decoder, such as the decoder 500 shown in FIG. 5.

[0175] Coding restoration filter modification data 1200 is shown, for simplicity and brevity, with respect to a current restoration filtering classes subset (Si) 1210. The current restoration filtering classes subset (Si) 1210 includes a first restoration filtering class (0), afifth restoration filtering class (4), a tenth restoration filtering class (9), and a twelfth restoration filtering class (11).

[0176] Obtaining modified restoration filter parameters, such as shown (at 1160) in FIG. 11, for the current restoration filtering classes subset (Si) 1210 includes obtaining modified restoration filter parameters for the first restoration filtering class (0), obtaining modified restoration filter parameters for the fifth restoration filtering class (4), obtaining modified restoration filter parameters for the tenth restoration filtering class (9), and obtaining modified restoration filter parameters for the twelfth restoration filtering class (11).

[0177] In some implementations, a reference restoration filter modification type for obtaining modified restoration filter parameters for the current restoration filtering classes subset (Si) 1210 indicates a modification of one or more of the reference restoration filter parameters of the current restoration filtering classes subset (Si) 1210 in accordance with defined parameters from a defined, or trained, reference restoration filter parameters superset corresponding to the current restoration filtering classes subset (Si) 1210 (not expressly shown in FIG. 12).

[0178] In some implementations, the reference restoration filter modification type for obtaining modified restoration filter parameters for the current restoration filtering classes subset (Si) 1210 indicates a modification of the parameters of the current restoration filtering classes subset (Si) 1210 in accordance with signaled restoration filter parameters modification data.

[0179] In some implementations, obtaining the signaled restoration filter parameters modification data, such as shown (at 1158) in FIG. 11, includes obtaining a, such as one, set of expressly signaled restoration filter parameters modification parameters, or coefficients, for updating the respective the restoration filtering classes from the current restoration filtering classes subset (Si) (obtained as shown at 1152 in FIG. 11) (not expressly shown in FIG. 12).

[0180] In some implementations, obtaining modified restoration filter parameters for the current restoration filtering classes subset (Si) 1210 includes replacing the parameters of the restoration filtering classes of the current restoration filtering classes subset (Si) 1210 with the expressly signaled modification parameters, or coefficients (not expressly shown in FIG. 12).

[0181] In some implementations, obtaining the signaled restoration filter parametersmodification data, such as shown (at 1158) in FIG. 11, includes obtaining differential restoration filter parameters (differentially coded restoration filter parameters), for updating the respective the restoration filtering classes from the current restoration filtering classes subset (Si) (obtained as shown at 1152 in FIG. 11) (as shown in FIG. 12).

[0182] In some implementations, obtaining modified restoration filter parameters for the current restoration filtering classes subset (Si) 1210 includes determining, calculating, identifying, or otherwise obtaining, centroid restoration filter parameters of a centroid 1220, or average, of the current restoration filtering classes subset (Si) 1210.

[0183] FIG. 12, shows a first diamond (Vo) 1222 with a white background arranged relative to the centroid 1220 as a representation of the unmodified restoration filter parameters of the first restoration filtering class (0).

[0184] FIG. 12, shows a second diamond (V4) 1224 with a white background arranged relative to the centroid 1220 as a representation of the unmodified restoration filter parameters of the fifth restoration filtering class (4).

[0185] FIG. 12, shows a third diamond (V9) 1226 with a white background arranged relative to the centroid 1220 as a representation of the unmodified restoration filter parameters of the tenth restoration filtering class (9).

[0186] FIG. 12, shows a fourth diamond (V11) 1226 with a white background arranged relative to the centroid 1220 as a representation of the unmodified restoration filter parameters of the twelfth restoration filtering class (11).

[0187] In some implementations, obtaining the modified restoration filter parameters for the current restoration filtering classes subset (Si) 1210 includes differential coding of the reference filter modification data, such as with respect to the centroid restoration filter parameters of the centroid 1220.

[0188] Differential coding of the reference filter modification data includes obtaining differential restoration filter parameters indicating a difference between modified centroid restoration filter parameters for a modified centroid (1230) with respect to the current restoration filtering classes subset and the centroid restoration filter parameters of the centroid 1220.

[0189] FIG. 12, shows a fifth diamond (V'o) 1232 with a stippled background arranged relative to the modified centroid 1230 as a representation of the modified restoration filter parameters of the first restoration filtering class (0).

[0190] FIG. 12, shows a sixth diamond (V 4) 1234 with a stippled background arranged relative to the modified centroid 1230 as a representation of the modified restoration filter parameters of the fifth restoration filtering class (4).

[0191] FIG. 12, shows a seventh diamond (V^) 1236 with a stippled background arranged relative to the modified centroid 1230 as a representation of the modified restoration filter parameters of the tenth restoration filtering class (9).

[0192] FIG. 12, shows an eighth diamond (V'n) 1236 with a stippled background arranged relative to the modified centroid 1230 as a representation of the modified restoration filter parameters of the twelfth restoration filtering class (11).

[0193] For example, the encoder may obtain the centroid restoration filter parameters of the centroid 1220, such as by averaging the unmodified, or reference, restoration filter parameters for the current restoration filtering classes subset, such as the current restoration filtering classes subset (Si) 1210 shown in FIG. 12, such as for the classes represented at 1222, 1224, 1226, and 1228. The encoder may obtain the modified centroid restoration filter parameters of the modified centroid 1230, such as by averaging the modified restoration filter parameters for the current modified restoration filtering classes subset, such as represented at 1232, 1234, 1236, and 1238 in FIG. 12. The encoder may obtain, as the differential restoration filter parameters, a difference between the modified centroid restoration filter parameters of the modified centroid 1230 and the corresponding centroid restoration filter parameters of the centroid 1220, such as by subtracting the centroid restoration filter parameters of the centroid 1220 from the modified centroid restoration filter parameters of the modified centroid 1230.

[0194] In another example, the decoder may obtain the differential restoration filter parameters by decoding, extracting, receiving, reading, obtaining, or otherwise accessing, the differential restoration filter parameters from the encoded bitstream. The decoder may obtain the centroid restoration filter parameters of the centroid 1220, such as by averaging the unmodified, or reference, restoration filter parameters for the current restoration filtering classes subset, such as the current restoration filtering classes subset (Si) 1210 shown in FIG. 12, such as for the classes represented at 1222, 1224, 1226, and 1228. The decoder may obtain the modified centroid restoration filter parameters of the modified centroid 1230, such as by combining the centroid restoration filter parameters of the centroid 1220 and the differential restoration filter parameters, such as by adding the centroid restoration filter parameters of the centroid 1220 and the differential restoration filter parameters. The decodermay obtain the modified restoration filter parameters for the current modified restoration filtering classes subset, such as represented at 1232, 1234, 1236, and 1238 in FIG. 12, using the modified centroid restoration filter parameters of the modified centroid 1230. For example, for a respective restoration filtering class, such as for the classes represented at 1222, 1224, 1226, and 1228, from the current restoration filtering classes subset, the decoder may obtain the corresponding modified restoration filter parameters, such as for the classes as represented at 1232, 1234, 1236, and 1238, by obtaining, as the modified restoration filter parameters for the respective restoration filtering class, a combination of the modified centroid restoration filter parameters of the modified centroid 1230 and a difference, or deviation, between the unmodified, or reference, restoration filter parameters for the respective restoration filtering class, such as represented at 1222, 1224, 1226, and 1228, and the centroid restoration filter parameters of the centroid 1220.

[0195] For example, to obtain the modified restoration filter parameters of the first restoration filtering class (0), represented by the fifth diamond (V'o) 1232 in FIG. 12, the decoder, or the encoder, obtains a deviation of the unmodified, or reference, restoration filter parameters of the first restoration filtering class (0), represented by the first diamond (Vo) 1222 in FIG. 12, from the centroid restoration filter parameters of the unmodified centroid 1220, and applies the deviation to the modified centroid restoration filter parameters of the modified centroid 1230.

[0196] In another example, to obtain the modified restoration filter parameters of the fifth restoration filtering class (4), represented by the sixth diamond (V 4) 1234 in FIG. 12, the decoder, or the encoder, obtains a deviation of the unmodified, or reference, restoration filter parameters of the fifth restoration filtering class (4), represented by the second diamond (V4) 1224 in FIG. 12, from the centroid restoration filter parameters of the unmodified centroid 1220, and applies the deviation to the modified centroid restoration filter parameters of the modified centroid 1230.

[0197] In another example, to obtain the modified restoration filter parameters of the tenth restoration filtering class (9), represented by the seventh diamond (V^) 1236 in FIG. 12, the decoder, or the encoder, obtains a deviation of the unmodified, or reference, restoration filter parameters of the tenth restoration filtering class (9), represented by the third diamond (V9) 1226 in FIG. 12, from the centroid restoration filter parameters of the unmodified, or reference, centroid 1220, and applies the deviation to the modified centroid restoration filter parameters of the modified centroid 1230.

[0198] In another example, to obtain the modified restoration filter parameters of the twelfth restoration filtering class (11), represented by the eighth diamond (V'n) 1236 in FIG. 12, the decoder, or the encoder, obtains a deviation of the unmodified, or reference, restoration filter parameters of the twelfth restoration filtering class (11), represented by the fourth diamond (Vn) 1226 in FIG. 12, from the centroid restoration filter parameters of the unmodified, or reference, centroid 1220, and applies the deviation to the centroid restoration filter parameters of the modified centroid 1230.

[0199] In some implementations, the modified restoration filter parameters obtained with respect to the centroid 1220 may be used as the modified restoration filter parameters for the restoration filtering classes of the current restoration filtering classes subset (Si) 1210.

[0200] In some implementations, obtaining the modified restoration filter parameters for the restoration filtering classes of the current restoration filtering classes subset (Si) 1210 includes obtaining the modified restoration filter parameters for the centroid 1220 as restoration filter parameters for a modified centroid 1230.

[0201] FIG. 13 is a flowchart diagram of an example of encoding using multi-class restoration filtering 1300 in accordance with implementations of this disclosure. Encoding using multi-class restoration filtering 1300 may be implemented in an encoder, such as the encoder 400 shown in FIG. 4. Encoding using multi-class restoration filtering 1300 includes block-based hybrid video coding as described herein.

[0202] Encoding using multi-class restoration filtering 1300 includes encoding, as described herein, input frame, or video, data, such as video stream 300 shown in FIG. 3 or the input video stream 402 shown in FIG. 4, or a frame thereof, such as the frame 330 shown in FIG. 3, to obtain an encoded bitstream, such as the compressed bitstream 404 shown in FIG.4 or the compressed bitstream 502 shown in FIG. 5.

[0203] Encoding using multi-class restoration filtering 1300 includes obtaining input frame data (at 1310), obtaining encoded frame data (at 1320), obtaining decoded frame data (at 1330), obtaining reconstructed frame data (at 1340), and output (at 1350). One or more aspects of Encoding using multi-class restoration filtering 1300 may be omitted from the description herein for simplicity and brevity.

[0204] The encoder obtains, such as by receiving, reading, or otherwise accessing, the input, or source, frame or video data (at 1310). Obtaining the input frame or video data includes obtaining current frame data for a current frame.

[0205] The encoder obtains encoded frame data (at 1320) for the current frame byencoding the input frame data. The encoding includes prediction coding, such as the prediction coding shown at 410 in FIG. 4, transformation, such as shown at 420 in FIG. 4, quantization, such as shown at 430 in FIG. 4, and entropy coding, such as shown at 440 in FIG. 4.

[0206] The encoder obtains decoded frame data (at 1330) by decoding the encoded frame data, such as prior to entropy coding. Obtaining the decoded frame data includes dequantization, such as shown at 450 in FIG. 4, inverse transformation, such as shown at 460 in FIG. 4, and reconstruction, such as shown at 470 in FIG. 4.

[0207] The encoder obtains reconstructed, filtered, or restored, frame data (at 1330). Obtaining the reconstructed, filtered, or restored, frame data (at 1330) is similar to obtaining reconstructed frame data as shown (at 1120) in FIG. 11, except as is described herein or as is otherwise clear from context.

[0208] Obtaining the reconstructed, filtered, or restored, frame data (at 1330) includes obtaining a current restoration unit (at 1342), obtaining current restoration filter (RF) parameters (at 1344), obtaining restoration filter modification data (at 1346), and outputting the restoration filter modification data (at 1348).

[0209] Obtaining the current restoration unit (at 1342) is similar to obtaining a current restoration unit as shown (at 1140) in FIG. 11, except as is described herein or as is otherwise clear from context.

[0210] Obtaining the current restoration filter (RF) parameters (at 1344) includes obtaining, maintaining, or both, a dynamic reference restoration filters buffer, or index, for the current frame, which is similar to obtaining, maintaining, or both, a dynamic reference restoration filters buffer, or index, for the current frame as described with respect to FIG. 11, except as is described herein or as is otherwise clear from context.

[0211] The dynamic reference restoration filters buffer includes one or more supersets (sets of sets) of reference restoration filter parameters (reference restoration filter parameters supersets) previously used, by the encoder, for restoration filtering a reference frame, a restoration unit, other than a current restoration unit, of the current frame, or both. In some implementations, the dynamic reference restoration filters buffer has a defined maximum size (P), indicating a maximum number, count, or cardinality, of reference restoration filter parameters supersets included in the dynamic reference restoration filters buffer. In some implementations, a defined, trained, or both, such as prior to and independent of encoding the current frame or video, reference restoration filter parameters superset is available.

[0212] Obtaining the current restoration filter (RF) parameters (at 1344) includesevaluating, searching, or testing, the defined, trained, or both, reference restoration filter parameters superset, and the reference restoration filter parameters supersets from the dynamic reference restoration filters buffer. For a respective reference restoration filter parameters superset from among the defined, trained, or both, reference restoration filter parameters superset, and the reference restoration filter parameters supersets from the dynamic reference restoration filters buffer, the encoder obtains, such as calculates or determines, a rate-distortion cost for encoding the current frame using the respective reference restoration filter parameters superset. In some implementations, the encoder may reoptimize for previous restoration units that used the respective reference restoration filter parameters superset.

[0213] For a respective restoration filtering classes subset from the restoration filtering classes subsets for a respective reference restoration filter parameters superset, the encoder may obtain modified restoration filter parameters in accordance with the restoration filter parameters from the defined, trained, or both, reference restoration filter parameters superset corresponding to the respective restoration filtering classes subset, and may obtain, such as calculate or determine, a rate-distortion cost for encoding the current frame using the modified restoration filter parameters.

[0214] For the respective restoration filtering classes subset from the restoration filtering classes subsets for the respective reference restoration filter parameters superset, the encoder may obtain modified restoration filter parameters by optimization of the restoration filter parameters, and may obtain, such as calculate or determine, a rate-distortion cost for encoding the current frame using the modified restoration filter parameters, which includes the cost of signaling modification data for the modified restoration filter parameters.

[0215] The encoder identifies the restoration filter parameters corresponding to the minimal cost among the rate-distortion cost for encoding the current frame using the respective reference restoration filter parameters superset (unmodified), the rate-distortion cost for encoding the current frame using the modified restoration filter parameters obtained in accordance with the defined, trained, or both, reference restoration filter parameters superset, and the a rate-distortion cost for encoding the current frame using the modified restoration filter parameters including the signaled modification data, as the current restoration filter parameters.

[0216] For a, such as one, restoration filtering classes subset, the encoder identifies the reference restoration filter parameters superset having the minimal aggregate rate-distortion cost. For multiple restoration filtering classes subsets, the encoder may obtain the filter setobtained from the previous stage as reference and repeat the search steps for respective subsets. In some implementations, defined pairs, or triples, of restoration filtering classes subsets may be used.

[0217] The encoder outputs a reference restoration filter parameters superset identifier that identifies the current reference restoration filter parameters superset, such as by including the reference restoration filter parameters superset identifier that identifies the current reference restoration filter parameters superset in the encoded bitstream, which may include encoding, such as entropy coding, the reference restoration filter parameters superset identifier.

[0218] The encoder outputs a reference restoration filter modification flag that indicates whether to perform modification of the current reference restoration filter parameters superset, such as by including the reference restoration filter modification flag in the encoded bitstream, which may include encoding, such as entropy coding, the reference restoration filter modification flag. In some implementations, the current reference restoration filter parameters superset may be used in the absence of modification and including the reference restoration filter modification flag in the encoded bitstream may be omitted, or a value indicating the absence of modification may be included in the encoded bitstream.

[0219] In implementations wherein the reference restoration filter modification flag indicates modification of the current reference restoration filter parameters superset, the encoder outputs one or more restoration filtering classes subset identifiers, such as by including the one or more restoration filtering classes subset identifiers in the encoded bitstream or by including zero or more restoration filtering classes subset branch identifiers in the encoded bitstream, which may include encoding, such as entropy coding, the one or more restoration filtering classes subset identifiers or the restoration filtering classes subset branch identifiers.

[0220] In implementations wherein the reference restoration filter modification flag indicates modification of the current reference restoration filter parameters superset, the encoder outputs a reference restoration filter modification type flag that indicates modification in accordance with the defined reference restoration filter parameters superset or in accordance with signaled restoration filter parameters modification data, such as by including the reference restoration filter modification type flag in the encoded bitstream, which may include encoding, such as entropy coding, the reference restoration filter modification type flag.

[0221] In implementations wherein the reference restoration filter modification flag indicates modification of the current reference restoration filter parameters superset, andwherein the reference restoration filter modification type flag indicates modification in accordance with signaled restoration filter parameters modification data, the encoder obtains restoration filter modification data (at 1346). Obtaining the restoration filter modification data (at 1346) is similar to obtaining modified parameters as shown (at 1160) in FIG. 11, except as is described herein or as is otherwise clear from context.

[0222] The encoder outputs the restoration filter modification data (at 1348), such as by including the restoration filter modification data in the encoded bitstream, which may include encoding, such as entropy coding, the restoration filter modification data.

[0223] The output, compressed, or encoded, bitstream, is output, such as stored or transmitted, such as to a decoder, (at 1350).

[0224] The encoding using multi-class restoration filtering 1300 shown in FIG. 13 outputs, the decoding using multi-class restoration filtering 1100 shown in FIG. 11 obtains, or both, an encoded bitstream comprising encoded frame data for a current frame and a reference restoration filter parameters superset identifier for a restoration unit of the current frame, wherein the reference restoration filter parameters superset identifier identifies a defined reference restoration filter parameters superset or a reference restoration filter parameters superset from a dynamic reference restoration filters buffer, wherein the dynamic reference restoration filters buffer includes reference restoration filter parameters supersets previously used for restoration filtering a reference frame of the current frame or for restoration filtering a second restoration unit of the current frame.

[0225] In some implementations, the encoded bitstream includes a reference restoration filter modification flag indicating whether to modify the current reference restoration filter parameters superset, and a restoration filtering classes subset identifier that identifies a current restoration filtering classes subset from a defined cardinality of restoration filtering classes subsets, wherein a respective restoration filtering classes subset includes a respective subset of restoration filtering classes. In some implementations, the restoration filtering classes subset identifier is an index value with respect to an index of the defined cardinality of restoration filtering classes subsets. In some implementations, the restoration filtering classes subset identifier includes one or more restoration filtering classes subset branch identifiers. In some implementations, the encoded bitstream includes the zero or more restoration filtering classes subset branch identifiers are binary.

[0226] In some implementations, the encoded bitstream includes a reference restoration filter modification type flag that indicates modification in accordance with the defined reference restoration filter parameters superset or in accordance with signaled restorationfilter parameters modification data.

[0227] In some implementations, the encoded bitstream includes the restoration filter parameters modification data. In some implementations, the restoration filter parameters modification data includes a set of restoration filter parameters. In some implementations, the restoration filter parameters modification data includes differential restoration filter parameters indicating a difference between modified centroid restoration filter parameters and centroid restoration filter parameters with respect to the current restoration filtering classes subset.

[0228] 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.

[0229] As used herein, the term “set” indicates a distinguishable collection or grouping of zero or more distinct elements or members that may be represented as a one-dimensional array or vector, except as expressly described herein or otherwise clear from context.

[0230] 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.

[0231] 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 hereincan 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.

[0232] The implementations of the transmitting computing and communication device 100A and / or the receiving computing and communication device 100B (and the algorithms, methods, instructions, etc. stored thereon and / or executed thereby) can be realized in hardware, software, or any combination thereof. The hardware can include, for example, computers, intellectual property (IP) cores, application-specific integrated circuits (ASICs), programmable logic arrays, optical processors, programmable logic controllers, microcode, microcontrollers, servers, microprocessors, digital signal processors or any other suitable circuit. In the claims, the term “processor” should be understood as encompassing any of the foregoing hardware, either singly or in combination. The terms “signal” and “data” are used interchangeably. Further, portions of the transmitting computing and communication device 100A and the receiving computing and communication device 100B do not necessarily have to be implemented in the same manner.

[0233] 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.

[0234] 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 transmittingcomputing 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.

[0235] 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.

[0236] 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.

[0237] 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 frame data by decoding an encoded bitstream, wherein decoding the encoded bitstream includes: obtaining decoded frame data for a current frame by decoding encoded frame data from the encoded bitstream; obtaining the reconstructed frame data by restoration filtering the decoded frame data, wherein restoration filtering the decoded frame data includes: identifying a current restoration unit of the current frame; obtaining a reference restoration filter parameters superset identifier from the encoded bitstream for the current restoration unit; obtaining, in accordance with the reference restoration filter parameters superset identifier, as a current reference restoration filter parameters superset, a defined reference restoration filter parameters superset or a reference restoration filter parameters superset from a dynamic reference restoration filters buffer, wherein the dynamic reference restoration filters buffer includes reference restoration filter parameters supersets previously used for restoration filtering a reference frame of the current frame or for restoration filtering a second restoration unit of the current frame; obtaining a filtered restoration unit by filtering the restoration unit using restoration filter parameters obtained from the current reference restoration filter parameters superset; and including the filtered restoration unit in the reconstructed frame data; and outputting the reconstructed frame data.

2. The method of claim 1, wherein the current reference restoration filter parameters superset indicates, on a per-class basis with respect to a defined set of restoration filtering classes, a respective reference restoration filter parameters set.

3. The method of claim 1, wherein filtering the restoration unit includes:obtaining a reference restoration filter modification flag from the encoded bitstream; and determining whether the reference restoration filter modification flag indicates modification of the current reference restoration filter parameters superset.

4. The method of claim 3, wherein, in response to determining that the reference restoration filter modification flag indicates modification of the current reference restoration filter parameters superset, filtering the restoration unit includes: obtaining a restoration filtering classes subset identifier; obtaining a current restoration filtering classes subset in accordance with the restoration filtering classes subset identifier; obtaining modified restoration filter parameters for the current restoration filtering classes subset; and updating the current reference restoration filter parameters superset in accordance with the modified restoration filter parameters.

5. The method of claim 4, wherein obtaining the current restoration filtering classes subset includes: obtaining the current restoration filtering classes subset from a defined cardinality of restoration filtering classes subsets, wherein a respective restoration filtering classes subset includes a respective subset of restoration filtering classes.

6. The method of claim 5, wherein: obtaining the restoration filtering classes subset identifier includes obtaining the restoration filtering classes subset identifier from the encoded bitstream, wherein the restoration filtering classes subset identifier is an index value with respect to an index of the defined cardinality of restoration filtering classes subsets.

7. The method of claim 5, wherein obtaining the restoration filtering classes subset identifier includes: obtaining zero or more restoration filtering classes subset branch identifiers from the encoded bitstream; and obtaining the restoration filtering classes subset identifier in accordance with the zero or more restoration filtering classes subset branch identifiers.

8. The method of claim 4, wherein, in response to determining that the reference restoration filter modification flag indicates modification of the current reference restoration filter parameters superset, filtering the restoration unit includes: obtaining a second restoration filtering classes subset identifier; obtaining a second current restoration filtering classes subset in accordance with the second restoration filtering classes subset identifier; obtaining second modified restoration filter parameters for the second current restoration filtering classes subset; and updating the current reference restoration filter parameters superset in accordance with the second modified restoration filter parameters.

9. The method of claim 4, wherein obtaining the modified restoration filter parameters includes: obtaining a reference restoration filter modification type flag from the encoded bitstream for the current restoration filtering classes subset; and determining whether the reference restoration filter modification type flag indicates modification in accordance with the defined reference restoration filter parameters superset or in accordance with signaled restoration filter parameters modification data.

10. The method of claim 9, wherein, in response to determining that the reference restoration filter modification type flag indicates modification in accordance with the defined reference restoration filter parameters superset: obtaining, as the modified restoration filter parameters for the current restoration filtering classes subset, parameters from the defined reference restoration filter parameters superset corresponding to the current restoration filtering classes subset.

11. The method of claim 9, wherein, in response to determining that the reference restoration filter modification type flag indicates modification in accordance with signaled restoration filter parameters modification data: obtaining the signaled restoration filter parameters modification data from the encoded bitstream.

12. The method of claim 11, wherein:obtaining the signaled restoration filter parameters modification data from the encoded bitstream includes: obtaining, from the encoded bitstream, a set of restoration fdter parameters; and updating the current reference restoration filter parameters superset includes: using the set of restoration filter parameters as the modified restoration filter parameters for updating the respective restoration filtering classes from the current restoration filtering classes subset.

13. The method of claim 11, wherein: obtaining the signaled restoration filter parameters modification data from the encoded bitstream includes: obtaining, from the encoded bitstream, differential restoration filter parameters; and obtaining the modified restoration filter parameters includes: obtaining centroid restoration filter parameters with respect to the current restoration filtering classes subset; obtaining, as modified centroid restoration filter parameters, a combination of the centroid restoration filter parameters and the differential restoration filter parameters; and obtaining the modified restoration filter parameters using the modified centroid restoration filter parameters, wherein, for a respective restoration filtering class from the current restoration filtering classes subset, obtaining the modified restoration filter parameters includes obtaining, as modified restoration filter parameters for the respective restoration filtering class, a combination of the modified centroid restoration filter parameters and a difference between unmodified restoration filter parameters for the respective restoration filtering class and the centroid restoration filter parameters.

14. The method of claim 1, wherein restoration filtering the decoded frame data includes: determining whether the current reference restoration filter parameters superset is unavailable from the dynamic reference restoration filters buffer; and in response to determining that the current reference restoration filter parameters superset is unavailable from the dynamic reference restoration filters buffer, including thecurrent reference restoration filter parameters superset in the dynamic reference restoration filters buffer.

15. A non-transitory computer-readable storage medium having stored thereon an encoded bitstream comprising: encoded frame data for a current frame; and a reference restoration filter parameters superset identifier for a restoration unit of the current frame, wherein the reference restoration filter parameters superset identifier identifies a defined reference restoration filter parameters superset or a reference restoration filter parameters superset from a dynamic reference restoration filters buffer, wherein the dynamic reference restoration filters buffer includes reference restoration filter parameters supersets previously used for restoration filtering a reference frame of the current frame or for restoration filtering a second restoration unit of the current frame.

16. An apparatus for decoding using multi-class restoration filtering, the apparatus comprising a non-transitory computer readable medium and a processor configured to execute instructions stored on the non-transitory computer readable medium to perform the method of any one of claims 1-14.

Images