Progressive Random Access (GRA) signaling in video coding

Abstract

A method for decoding video data comprises: decoding, according to a decoded video bitstream and as an unsigned integer 0th order index Golomb decoding syntax element with left bit first, a value specifying a target recovery point picture for a current picture in a current sequence of pictures, wherein the target recovery point picture is located at or after the current picture in display order; and resuming decoding of pictures of the current sequence at the target recovery point picture.

Description

[0001] This application claims priority to U.S. Application No. 16 / 909,447, filed on June 23, 2020, which claims the benefit of U.S. Provisional Application No. 62 / 865,838, filed on June 24, 2019, and U.S. Provisional Application No. 62 / 867,083, filed on June 26, 2019, each of which is hereby incorporated by reference in its entirety. Technical Field

[0002] The present disclosure relates to video encoding and video decoding. Background Art

[0003] Digital video capabilities can be incorporated into a wide variety of devices, including digital televisions, digital live broadcast systems, wireless broadcast systems, personal digital assistants (PDAs), laptop or desktop computers, tablet computers, e-book readers, digital cameras, digital recording devices, digital media players, video game devices, video game consoles, cellular or satellite radio phones, so-called "smart phones", video teleconferencing devices, video streaming devices, etc. Digital video devices implement video decoding technology (such as the video decoding technology described in the standards defined by MPEG-2, MPEG-4, ITU-T H.263, ITU-T H.264 / MPEG-4, Part 10, Advanced Video Coding (AVC), ITU-T H.265 / High Efficiency Video Coding (HEVC) and extensions of such standards). Video devices can more efficiently send, receive, encode, decode and / or store digital video information by implementing such video decoding technology.

[0004] Video coding techniques include spatial (intra-picture) prediction and / or temporal (inter-picture) prediction to reduce or remove redundancy inherent in video sequences. For block-based video coding, a video slice (e.g., a video picture or a portion of a video picture) may be partitioned into video blocks, which may also be referred to as coding tree units (CTUs), coding units (CUs), and / or coding nodes. Video blocks in an intra-coded (I) slice of a picture are encoded using spatial prediction relative to reference samples in neighboring blocks in the same picture. Video blocks in an inter-coded (P or B) slice of a picture may use spatial prediction relative to reference samples in neighboring blocks in the same picture or temporal prediction relative to reference samples in other reference pictures. Pictures may be referred to as frames, and reference pictures may be referred to as reference frames. Summary of the invention

[0005] In summary, the present disclosure describes techniques for signaling progressive random access (GRA) recovery points in video decoding. An important aspect in video communication is random access. Random access refers to the ability of a decoder to start decoding a stream at a point other than the beginning of the stream and recover an accurate or approximate representation of the decoded pictures. Random access points and recovery points characterize random access operations. A random access point is any decoded picture that can initiate decoding. All decoded pictures at or after the recovery point in output order are correct or approximately correct in content. If the random access point is the same as the recovery point, the random access operation is instantaneous; otherwise, it is progressive.

[0006] Random access points enable seek, fast forward, and rewind operations in locally stored video streams. In video-on-demand streams, the server can respond to a seek request by sending data starting from the random access point closest to the requested destination of the seek operation. Random access points enable listening to broadcasts. In addition, random access points can be decoded as a response to a scene cut in the source sequence or a response to an update request within a fast-update picture.

[0007] In some examples, a progressive random access (GRA) picture may be defined as a picture that signals the start of progressive random access using a target recovery point picture order count (POC) value at which the recovery picture is located. As such, if the decoder starts the decoding process from a GRA picture, the decoder will decode the picture but will not output the picture until the recovery point picture, but the decoder may decode and output the picture from and after the recovery picture. The video encoder may use a syntax element with a signed value (e.g., recovery_poc_cnt) to signal the target recovery point picture. This means that a picture with a smaller POC value than the current GRA picture may be a recovery point. This results in a situation where all pictures starting from and forward from the recovery point in decoding may be output. Such a situation may have one or more problems. For example, there may be pictures that need to be skipped (e.g., not output / displayed) in the output order because the picture is before the recovery point picture in the decoding order. This may result in gaps in the rendered picture, which may be undesirable.

[0008] According to one or more techniques of the present disclosure, a video decoder (e.g., a video decoder and / or a video encoder) may use a syntax element with an unsigned value (e.g., recovery_poc_cnt) to decode an indication of a target recovery point picture. For example, the video decoder may decode the syntax element as an unsigned integer 0th order index golomb decoding syntax element with the left bit first. By using syntax elements with unsigned values ​​to decode the target recovery point picture, the techniques of the present disclosure eliminate the undesirable condition of introducing gaps in the output of the rendered picture. In addition, using syntax elements with unsigned values ​​to decode the target recovery point picture can reduce the amount of data used to signal the target recovery point picture, which can improve decoding efficiency.

[0009] In one example, a method for decoding video data includes: decoding, based on a decoded video bitstream and as an unsigned integer 0th-order index Golomb decoding element with a left bit first, a value specifying a target recovery point picture for a current picture in a current sequence of pictures, wherein the target recovery point picture is located at or after the current picture in a display order; and resuming decoding of the pictures of the current sequence at the target recovery point picture.

[0010] In one example, a method for encoding video data includes: selecting a target recovery point picture for a current picture in a current sequence of pictures and at or after the current picture in display order; and encoding, in a decoded video bitstream and as an unsigned integer 0th order exponent Golomb decoding syntax element with a left bit first, a value specifying the target recovery point picture for the current picture in the current sequence of pictures.

[0011] In another example, a device includes: a memory configured to store at least a portion of a decoded video bitstream; and one or more processors implemented in circuits and configured to: decode, based on the decoded video bitstream and as an unsigned integer 0th order index Golomb decoding syntax element with a left bit first, a value specifying a target recovery point picture for a current picture in a current sequence of pictures, wherein the target recovery point picture is located at or after the current picture in a display order; and resume decoding of the pictures of the current sequence at the target recovery point picture.

[0012] In another example, a device includes: a memory configured to store at least a portion of a decoded video bitstream; and one or more processors implemented in circuits and configured to: select a target recovery point picture for a current picture in a current sequence of pictures and at or after the current picture in display order; and encode in the decoded video bitstream and as an unsigned integer 0th order exponent Golomb decoding syntax element with a left bit first, a value specifying the target recovery point picture for the current picture in the current sequence of pictures.

[0013] The details of one or more examples are set forth in the accompanying drawings and the description below. Other features, objects, and advantages will be apparent from the description, drawings, and claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 is a block diagram illustrating an example video encoding and decoding system that may perform the techniques of this disclosure.

[0015] Figure 2A and Figure 2B is a conceptual diagram illustrating an example quadtree binary tree (QTBT) structure and a corresponding coding tree unit (CTU).

[0016] Figure 3 is a block diagram illustrating an example video encoder that may perform the techniques of this disclosure.

[0017] Figure 4 is a block diagram illustrating an example video decoder that may perform the techniques of this disclosure.

[0018] Figure 5 is a flow chart illustrating an example encoding method of the present disclosure.

[0019] Figure 6 is a flow chart illustrating an example decoding method of the present disclosure.

[0020] Figure 7 is a flow diagram illustrating an example technique for encoding progressive random access (GRA) recovery points in video coding, in accordance with one or more techniques of this disclosure.

[0021] Figure 8 is a flow diagram illustrating an example technique for decoding progressive random access (GRA) recovery points in video coding, in accordance with one or more techniques of this disclosure. DETAILED DESCRIPTION

[0022] Figure 11 is a block diagram illustrating an example video encoding and decoding system 100 that may perform techniques of the present disclosure. In general, techniques of the present disclosure relate to decoding (encoding and / or decoding) video data. In general, video data includes any data used to process video. Thus, video data may include original, unencoded video, encoded video, decoded (e.g., reconstructed) video, and video metadata (e.g., signaling data).

[0023] like Figure 1 As shown, in this example, system 100 includes a source device 102 that provides encoded video data to be decoded and displayed by a destination device 116. Specifically, source device 102 provides the video data to destination device 116 via computer-readable medium 110. Source device 102 and destination device 116 may include any of a wide variety of devices, including desktop computers, notebook computers (i.e., laptop computers), tablet computers, set-top boxes, telephone handsets such as smart phones, televisions, cameras, display devices, digital media players, video game consoles, video streaming devices, etc. In some cases, source device 102 and destination device 116 may be equipped for wireless communication and, therefore, may be referred to as wireless communication devices.

[0024] exist Figure 1 In the example of , source device 102 includes video source 104, memory 106, video encoder 200 and output interface 108. Destination device 116 includes input interface 122, video decoder 300, memory 120 and display device 118. According to the present disclosure, the video encoder 200 of source device 102 and the video decoder 300 of destination device 116 can be configured to apply technology for progressive random access (GRA) recovery point signaling. Therefore, source device 102 represents an example of a video encoding device, and destination device 116 represents an example of a video decoding device. In other examples, source device and destination device may include other components or arrangements. For example, source device 102 may receive video data from an external video source such as an external camera. Similarly, destination device 116 may be connected to an external display device with an interface, rather than including an integrated display device.

[0025] like Figure 1The system 100 shown is only an example. In general, any digital video encoding and / or decoding device can perform the technology for GRA recovery point signaling. The source device 102 and the destination device 116 are only examples of such decoding devices, wherein the source device 102 generates decoded video data for transmission to the destination device 116. The present disclosure refers to a "decoding" device as a device that performs decoding (e.g., encoding and / or decoding) of data. Therefore, the video encoder 200 and the video decoder 300 represent examples of decoding devices (specifically, video encoders and video decoders), respectively. In some examples, the devices 102 and 116 can operate in a substantially symmetrical manner, so that each of the devices 102 and 116 includes video encoding and decoding components. Therefore, the system 100 can support one-way or two-way video transmission between the video devices 102 and 116, for example, for video streaming, video playback, video broadcasting, or video telephony.

[0026] Typically, video source 104 represents a source of video data (i.e., original, unencoded video data), and provides a sequence of pictures (also referred to as "frames") of the video data to video encoder 200, which encodes the data for the pictures. Video source 104 of source device 102 may include a video capture device, such as a camera, a video archive containing previously captured original video, and / or a video feed interface for receiving video from a video content provider. As another alternative, video source 104 may generate computer graphics-based data as source video, or a combination of real-time video, archived video, and computer-generated video. In each case, video encoder 200 may encode captured, pre-captured, or computer-generated video data. Video encoder 200 may rearrange pictures from the received order (sometimes referred to as "display order") to a decoding order for decoding. Video encoder 200 may generate a bitstream comprising encoded video data. Source device 102 may then output the encoded video data onto computer-readable medium 110 via output interface 108 to be received and / or retrieved by, for example, input interface 122 of destination device 116 .

[0027] The memory 106 of the source device 102 and the memory 120 of the destination device 116 represent general purpose memory. In some examples, the memory 106, memory 120 can store original video data, for example, the original video from the video source 104 and the original decoded video data from the video decoder 300. In addition or alternatively, the memory 106, memory 120 can store software instructions executable by, for example, the video encoder 200 and the video decoder 300, respectively. Although shown separately from the video encoder 200 and the video decoder 300 in this example, it should be understood that the video encoder 200 and the video decoder 300 can also include internal memory for functionally similar or equivalent purposes. In addition, the memory 106, memory 120 can store, for example, encoded video data output from the video encoder 200 and input to the video decoder 300. In some examples, portions of the memory 106, memory 120 can be allocated as one or more video buffers, for example, to store original decoded and / or encoded video data.

[0028] The computer-readable medium 110 may represent any type of medium or device capable of delivering the encoded video data from the source device 102 to the destination device 116. In one example, the computer-readable medium 110 represents a communication medium that enables the source device 102 to directly send the encoded video data to the destination device 116 in real time, for example, via a radio frequency network or a computer-based network. The output interface 108 may modulate the transmission signal including the encoded video data according to a communication standard such as a wireless communication protocol, and the input interface 122 may demodulate the received transmission signal according to a communication standard such as a wireless communication protocol. The communication medium may include any wireless or wired communication medium, for example, a radio frequency (RF) spectrum or one or more physical transmission lines. The communication medium may form a portion of a packet-based network such as a local area network, a wide area network, or a global network such as the Internet. The communication medium may include a router, a switch, a base station, or any other device that may be useful for facilitating communication from the source device 102 to the destination device 116.

[0029] In some examples, source device 102 may output the encoded data from output interface 108 to storage device 112. Similarly, destination device 116 may access the encoded data from storage device 112 via input interface 122. Storage device 112 may include any of a variety of distributed or locally accessed data storage media, such as a hard drive, Blu-ray disc, DVD, CD-ROM, flash memory, volatile or non-volatile memory, or any other suitable digital storage medium for storing encoded video data.

[0030] In some examples, the source device 102 may output the encoded video data to a file server 114 or another intermediate storage device that may store the encoded video generated by the source device 102. The destination device 116 may access the stored video data from the file server 114 via streaming or downloading. The file server 114 may be any type of server device capable of storing the encoded video data and sending the encoded video data to the destination device 116. The file server 114 may represent a web server (e.g., for a website), a file transfer protocol (FTP) server, a content delivery network device, or a network attached storage (NAS) device. The destination device 116 may access the encoded video data from the file server 114 via any standard data connection (including an Internet connection). This may include a wireless channel (e.g., a Wi-Fi connection), a wired connection (e.g., a digital subscriber line (DSL), a cable modem, etc.), or a combination of the two suitable for accessing the encoded video data stored on the file server 114. The file server 114 and the input interface 122 may be configured to operate according to the following: a streaming protocol, a download transmission protocol, or a combination thereof.

[0031] Output interface 108 and input interface 122 may represent wireless transmitters / receivers, modems, wired networking components (e.g., Ethernet cards), wireless communication components that operate according to any of the various IEEE 802.11 standards, or other physical components. In examples where output interface 108 and input interface 122 include wireless components, output interface 108 and input interface 122 may be configured to transmit data (e.g., encoded video data) according to a cellular communication standard (e.g., 4G, 4G-LTE (Long Term Evolution), Advanced LTE, 5G, etc.). In some examples where output interface 108 includes a wireless transmitter, output interface 108 and input interface 122 may be configured to transmit data (e.g., encoded video data) according to other wireless standards (e.g., IEEE 802.11 specifications, IEEE 802.15 specifications (e.g., ZigBee 5G, etc.). TM ), Bluetooth TM Standards, etc.) to transmit data (such as encoded video data). In some examples, source device 102 and / or destination device 116 may include corresponding system-on-chip (SoC) devices. For example, source device 102 may include a SoC device for performing the functions assigned to video encoder 200 and / or output interface 108, and destination device 116 may include a SoC device for performing the functions assigned to video decoder 300 and / or input interface 122.

[0032] The techniques of the present disclosure may be applied to video decoding to support any of a variety of multimedia applications, such as over-the-air television broadcasting, cable television transmission, satellite television transmission, Internet streaming video transmission (such as Dynamic Adaptive Streaming over HTTP (DASH)), digital video encoded onto a data storage medium, decoding of digital video stored on a data storage medium, or other applications.

[0033] The input interface 122 of the destination device 116 receives the encoded video bitstream from the computer-readable medium 110 (e.g., the storage device 112, the file server 114, etc.). The encoded video bitstream may include signaling information such as the following syntax elements defined by the video encoder 200 (which are also used by the video decoder 300): the syntax elements have values ​​that describe the characteristics and / or processing of video blocks or other decoding units (e.g., slices, pictures, groups of pictures, sequences, etc.). The display device 118 displays the decoded pictures of the decoded video data to the user. The display device 118 can represent any of a variety of display devices, such as a cathode ray tube (CRT), a liquid crystal display (LCD), a plasma display, an organic light emitting diode (OLED) display, or another type of display device.

[0034] Despite Figure 1 200 and 300 may each be integrated with an audio encoder and / or an audio decoder and may include appropriate MUX-DEMUX units or other hardware and / or software to process multiplexed streams including both audio and video in a common data stream. If applicable, the MUX-DEMUX units may follow the ITU H.223 multiplexer protocol or other protocols such as the User Datagram Protocol (UDP).

[0035] The video encoder 200 and the video decoder 300 can each be implemented as any of a variety of suitable encoder and / or decoder circuits, such as one or more microprocessors, digital signal processors (DSPs), application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), discrete logic, software, hardware, firmware, or any combination thereof. When the technology is partially implemented in software, the device can store instructions for the software in a suitable non-transitory computer-readable medium, and use one or more processors to execute the instructions in hardware to perform the technology of the present disclosure. Each of the video encoder 200 and the video decoder 300 can be included in one or more encoders or decoders, and any of the encoders or decoders can be integrated as part of a combined encoder / decoder (CODEC) in the corresponding device. The device including the video encoder 200 and / or the video decoder 300 can include an integrated circuit, a microprocessor, and / or a wireless communication device (such as a cellular phone).

[0036] The video encoder 200 and the video decoder 300 may operate according to a video coding standard, such as the ITU-T H.265 (also known as the High Efficiency Video Coding (HEVC) standard) or an extension thereof, such as a multi-view and / or scalable video coding extension. Alternatively, the video encoder 200 and the video decoder 300 may operate according to other proprietary or industry standards, such as the Joint Exploration Test Model (JEM) or the ITU-T H.266 standard, also known as Versatile Video Coding (VVC). The latest draft of the VVC standard is described in the following document: Bross et al., “Versatile Video Coding (Draft 5)”, Joint Video Experts Group (JVET) of ITU-T SG 16WP 3 and ISO / IEC JTC 1 / SC 29 / WG 11, 14th Meeting: Geneva, Switzerland, March 19-27, 2019, JVET-N1001-v8 (hereinafter referred to as “VVC Draft 5”). However, the technology of the present disclosure is not limited to any particular coding standard.

[0037] Typically, the video encoder 200 and the video decoder 300 can perform block-based decoding of the picture. The term "block" generally refers to a structure that includes data to be processed (e.g., to be encoded, decoded, or otherwise used in the encoding and / or decoding process). For example, a block may include a two-dimensional matrix of samples of luminance and / or chrominance data. Typically, the video encoder 200 and the video decoder 300 can decode video data represented in a YUV (e.g., Y, Cb, Cr) format. That is, the video encoder 200 and the video decoder 300 can decode luminance and chrominance components instead of decoding red, green, and blue (RGB) data for samples of the picture, wherein the chrominance components may include both red hue and blue hue chrominance components. In some examples, the video encoder 200 converts the received RGB formatted data to a YUV representation before encoding, and the video decoder 300 converts the YUV representation to an RGB format. Alternatively, a pre-processing unit and a post-processing unit (not shown) may perform these conversions.

[0038] In general, the present disclosure may relate to the decoding (e.g., encoding and decoding) of a picture to include the process of encoding or decoding data for the picture. Similarly, the present disclosure may relate to the decoding of a block of a picture to include the process of encoding or decoding data for the block (e.g., prediction and / or residual decoding). The encoded video bitstream typically includes a series of values ​​for syntax elements that represent decoding decisions (e.g., decoding modes) and partitioning of the picture into blocks. Therefore, references to decoding a picture or a block should generally be understood as decoding the values ​​of the syntax elements used to form the picture or the block.

[0039] HEVC defines various blocks, including coding units (CUs), prediction units (PUs), and transform units (TUs). According to HEVC, a video decoder (such as the video encoder 200) partitions a coding tree unit (CTU) into CUs according to a quadtree structure. That is, the video decoder partitions the CTU and CU into four equal, non-overlapping squares, and each node of the quadtree has zero or four child nodes. A node without child nodes may be referred to as a "leaf node", and the CU of such a leaf node may include one or more PUs and / or one or more TUs. The video decoder may further partition the PU and TU. For example, in HEVC, the residual quadtree (RQT) represents the partitioning of a TU. In HEVC, a PU represents inter-frame prediction data, and a TU represents residual data. An intra-predicted CU includes intra-frame prediction information, such as an intra-frame mode indication.

[0040] As another example, the video encoder 200 and the video decoder 300 may be configured to operate according to JEM or VVC. According to JEM or VVC, a video decoder (such as the video encoder 200) partitions a picture into a plurality of coding tree units (CTUs). The video encoder 200 may partition the CTU according to a tree structure (such as a quadtree-binary tree (QTBT) structure or a multi-type tree (MTT) structure). The QTBT structure removes the concept of multiple partition types, such as the separation between CU, PU, ​​and TU of HEVC. The QTBT structure includes two levels: a first level partitioned according to quadtree partitioning, and a second level partitioned according to binary tree partitioning. The root node of the QTBT structure corresponds to the CTU. The leaf nodes of the binary tree correspond to the coding units (CUs).

[0041] In the MTT segmentation structure, blocks can be segmented using quadtree (QT) segmentation, binary tree (BT) segmentation, and one or more types of ternary tree (TT) segmentation. A ternary tree segmentation is a segmentation in which a block is split into three sub-blocks. In some examples, the ternary tree segmentation divides the block into three sub-blocks without dividing the original block through the center. The segmentation types in MTT (e.g., QT, BT, and TT) can be symmetric or asymmetric.

[0042] In some examples, the video encoder 200 and the video decoder 300 may use a single QTBT or MTT structure to represent each of the luma component and the chroma components, while in other examples, the video encoder 200 and the video decoder 300 may use two or more QTBT or MTT structures, such as one QTBT / MTT structure for the luma component and another QTBT / MTT structure for the two chroma components (or two QTBT / MTT structures for the corresponding chroma components).

[0043] The video encoder 200 and the video decoder 300 may be configured to use quadtree segmentation, QTBT segmentation, MTT segmentation, or other segmentation structures per HEVC. For purposes of explanation, a description of the techniques of the present disclosure is given with respect to QTBT segmentation. However, it should be understood that the techniques of the present disclosure may also be applied to video decoders configured to use quadtree segmentation or also use other types of segmentation.

[0044] Blocks (e.g., CTUs or CUs) may be grouped in a picture in various ways. As an example, a brick may refer to a rectangular area of ​​a CTU row within a particular tile in a picture. A tile may be a rectangular area of ​​a CTU within a particular tile column and a particular tile row in a picture. A tile column refers to a rectangular area of ​​a CTU having a height equal to the height of the picture and a width specified by a syntax element (e.g., such as in a picture parameter set). A tile row refers to a rectangular area of ​​a CTU having a height specified by a syntax element (e.g., such as in a picture parameter set) and a width equal to the width of the picture.

[0045] In some examples, a slice may be partitioned into multiple bricks, each of which may include one or more CTU rows within the slice. A slice that is not partitioned into multiple bricks may also be referred to as a brick. However, a brick that is a true subset of a slice may not be referred to as a slice.

[0046] The bricks in a picture can also be arranged in slices. A slice can be an integer number of bricks of a picture that can be uniquely contained in a single network abstraction layer (NAL) unit. In some examples, a slice includes multiple complete slices or a series of consecutive complete bricks of only one slice.

[0047] The present disclosure may use "NxN" and "N by N" interchangeably to refer to the sample dimensions of a block (such as a CU or other video block) in terms of vertical and horizontal dimensions, for example, 16x16 samples or 16 by 16 samples. Typically, a 16x16 CU will have 16 samples in the vertical direction (y=16) and 16 samples in the horizontal direction (x=16). Similarly, an NxNCU typically has N samples in the vertical direction and N samples in the horizontal direction, where N represents a non-negative integer value. The samples in a CU may be arranged in rows and columns. In addition, a CU does not necessarily need to have the same number of samples in the horizontal direction as in the vertical direction. For example, a CU may include NxM samples, where M is not necessarily equal to N.

[0048] The video encoder 200 encodes video data representing prediction and / or residual information and other information for a CU. The prediction information indicates how the CU will be predicted in order to form a prediction block for the CU. The residual information typically represents the sample-by-sample difference between the samples of the CU before encoding and the prediction block.

[0049] In order to predict a CU, the video encoder 200 can generally form a prediction block for the CU by inter-frame prediction or intra-frame prediction. Inter-frame prediction generally refers to predicting a CU based on data of a previously decoded picture, while intra-frame prediction generally refers to predicting a CU based on previously decoded data of the same picture. In order to perform inter-frame prediction, the video encoder 200 can use one or more motion vectors to generate a prediction block. The video encoder 200 can generally perform motion search to identify a reference block that closely matches the CU, for example, in terms of the difference between the CU and the reference block. The video encoder 200 can use the sum of absolute differences (SAD), the sum of squared differences (SSD), the mean absolute difference (MAD), the mean square difference (MSD), or other such difference calculations to calculate a difference metric to determine whether the reference block closely matches the current CU. In some examples, the video encoder 200 can use unidirectional prediction or bidirectional prediction to predict the current CU.

[0050] Some examples of JEM and VVC also provide an affine motion compensation mode, which can be considered an inter-frame prediction mode. In the affine motion compensation mode, the video encoder 200 can determine two or more motion vectors representing non-translational motion (such as zooming in or out, rotation, perspective motion, or other irregular motion types).

[0051] In order to perform intra prediction, the video encoder 200 can select an intra prediction mode to generate a prediction block. Some examples of JEM and VVC provide sixty-seven intra prediction modes, including various directional modes, as well as planar modes and DC modes. Typically, the video encoder 200 selects an intra prediction mode that describes neighboring samples of the current block according to which the samples of the current block (e.g., a block of a CU) are to be predicted. Assuming that the video encoder 200 decodes the CTU and CU in a raster scan order (from left to right, from top to bottom), such samples can typically be above, above left, or to the left of the current block in the same picture as the current block.

[0052] The video encoder 200 encodes data representing a prediction mode for the current block. For example, for an inter-frame prediction mode, the video encoder 200 may encode data representing which of the various available inter-frame prediction modes is used and motion information for the corresponding mode. For unidirectional or bidirectional inter-frame prediction, for example, the video encoder 200 may encode motion vectors using advanced motion vector prediction (AMVP) or merge mode. The video encoder 200 may use a similar mode to encode motion vectors for affine motion compensation mode.

[0053] After a prediction, such as intra prediction or inter prediction of a block, the video encoder 200 may calculate residual data for the block. The residual data (such as a residual block) represents the sample-by-sample difference between the block and a prediction block for the block, which is formed using a corresponding prediction mode. The video encoder 200 may apply one or more transforms to the residual block to generate transformed data in a transform domain rather than in a sample domain. For example, the video encoder 200 may apply a discrete cosine transform (DCT), an integer transform, a wavelet transform, or a conceptually similar transform to the residual video data. In addition, the video encoder 200 may apply a secondary transform after the first transform, such as a mode-dependent non-separable secondary transform (MDNSST), a signal-dependent transform, a Karhunen-Loeve transform (KLT), etc. The video encoder 200 generates transform coefficients after applying one or more transforms.

[0054] As described above, after performing any transforms to produce transform coefficients, the video encoder 200 may perform quantization of the transform coefficients. Quantization generally refers to a process in which transform coefficients are quantized to potentially reduce the amount of data used to represent the coefficients, thereby providing further compression. By performing the quantization process, the video encoder 200 may reduce the bit depth associated with some or all of the coefficients. For example, the video encoder 200 may round down an n-bit value to an m-bit value during quantization, where n is greater than m. In some examples, to perform quantization, the video encoder 200 may perform a bitwise right shift of the value to be quantized.

[0055] After quantization, the video encoder 200 can scan the transform coefficients to generate a one-dimensional vector from a two-dimensional matrix including the quantized transform coefficients. The scan can be designed to place coefficients of higher energy (and therefore lower frequency) in front of the vector and transform coefficients of lower energy (and therefore higher frequency) in the back of the vector. In some examples, the video encoder 200 can scan the quantized transform coefficients using a predefined scan order to generate a serialized vector, and then entropy encode the quantized transform coefficients of the vector. In other examples, the video encoder 200 can perform adaptive scanning. After scanning the quantized transform coefficients to form a one-dimensional vector, the video encoder 200 can entropy encode the one-dimensional vector, for example, according to context adaptive binary arithmetic coding (CABAC). The video encoder 200 can also entropy encode the values ​​of the syntax elements used to describe the metadata associated with the encoded video data for use by the video decoder 300 when decoding the video data.

[0056] To perform CABAC, the video encoder 200 may assign context within a context model to a symbol to be transmitted. The context may relate to, for example, whether neighboring values ​​of the symbol are zero values. The probability determination may be based on the context assigned to the symbol.

[0057] The video encoder 200 may also generate syntax data (such as block-based syntax data, picture-based syntax data, and sequence-based syntax data) to the video decoder 300, for example, in a picture header, a block header, a slice header, or other syntax data (such as a sequence parameter set (SPS), a picture parameter set (PPS), or a video parameter set (VPS). Likewise, the video decoder 300 may decode such syntax data to determine how to decode the corresponding video data.

[0058] In this way, the video encoder 200 can generate a bitstream, which includes the encoded video data, for example, a syntax element describing the partitioning of a picture into blocks (e.g., CUs) and prediction and / or residual information for the blocks. Finally, the video decoder 300 can receive the bitstream and decode the encoded video data.

[0059] In general, the video decoder 300 performs a process that is reciprocal to the process performed by the video encoder 200 to decode the encoded video data of the bitstream. For example, the video decoder 300 may use CABAC to decode the values ​​of the syntax elements for the bitstream in a manner substantially similar to the CABAC encoding process of the video encoder 200, but reciprocal. The syntax elements may define partitioning information for partitioning a picture into CTUs, and partitioning each CTU according to a corresponding partitioning structure (such as a QTBT structure) to define CUs of the CTUs. The syntax elements may also define prediction and residual information for a block (e.g., CU) of video data.

[0060] The residual information may be represented by, for example, quantized transform coefficients. The video decoder 300 may inverse quantize and inverse transform the quantized transform coefficients of the block to regenerate a residual block for the block. The video decoder 300 uses the prediction mode (intra-frame prediction or inter-frame prediction) and related prediction information (e.g., motion information for inter-frame prediction) sent by the signal to form a prediction block for the block. The video decoder 300 may then combine the prediction block and the residual block (on a sample-by-sample basis) to regenerate the original block. The video decoder 300 may perform additional processing, such as performing a deblocking process to reduce visual artifacts along the boundaries of the blocks.

[0061] In VVC draft 5, a progressive random access (GRA) picture can be defined as a picture that signals the start of progressive random access using the target recovery point POC value at which the recovery picture is located. If the decoder starts the decoding process from a GRA picture with NoIncorrectPicOutputFlag set to 1, the decoder can decode the picture but not output the picture until the recovery point picture is decoded. The decoder can decode the pictures from and after the recovery point picture and output the pictures from and after the recovery point picture. The target recovery point picture can be signaled by recovery_poc_cnt having a signed value and signaled using se(v). This means that a picture with a smaller POC value than the current (curr) GRA pic (GRA_NUT) can be a recovery point. In this way, all pictures starting from the recovery point and forward in decoding can be output.

[0062] There may be one or more problems with current GRA signaling. As an example, there may be pictures in the output order that need to be skipped (e.g., not output / displayed) because they precede the recovery point picture in the decoding order. This will result in gaps in the rendered pictures, which is undesirable.

[0063] According to one or more techniques of the present disclosure, instead of allowing a recovery point picture to precede a GRA_NUT picture in display order, a video decoder only allows pictures that are equal to or greater than the GRA_NUT picture in a POC value for a recovery picture. For example, instead of allowing a recovery point picture with a smaller POC value than a current GRA picture, a video decoder may only allow pictures with a POC value equal to or greater than the current GRA picture as recovery pictures.

[0064] The current specifications and semantics in VVC Draft 5 are provided below:

[0065] 7.3.5 Slice Header Syntax

[0066] 7.3.5.1 Generic Slice Header Syntax

[0067]

[0068] recovery_poc_cnt specifies the recovery point of the decoded picture in the output order. If there is a picture picA in the CVS that follows the current GRA picture in the decoding order and has a PicOrderCntVal equal to the PicOrderCntVal of the current GRA picture plus the value of recovery_poc_cnt, then the picture picA is called the recovery point picture. Otherwise, the first picture in the output order that has a PicOrderCntVal greater than the value of the current GRA picture plus the recovery_poc_cnt is called the recovery point picture. In the decoding order, the recovery point picture should not be before the current GRA picture. The value of recovery_poc_cnt should be in the range of -MaxPicOrderCntLsb / 2 to MaxPicOrderCntLsb / 2-1 (including -MaxPicOrderCntLsb / 2 and MaxPicOrderCntLsb / 2-1).

[0069] The variable RpPicOrderCntVal is derived as follows:

[0070] RpPicOrderCntVal = PicOrderCntVal + recovery_poc_cnt (7-40)

[0071] 8.1 General Decoding Process

[0072] 8.1.1 Overview

[0073] For each IRAP picture in the bitstream, the following applies:

[0074] - If the picture is an IDR picture, the first picture in the bitstream in decoding order, or the first picture following the end of a sequence NAL unit in decoding order, the variable NoIncorrectPicOutputFlag is set equal to 1.

[0075] – Otherwise, if some external unit not specified in this specification is available to set the variable HandleCraAsCvsStartFlag to a value for the picture, then HandleCraAsCvsStartFlag is set equal to the value provided by the external unit and NoIncorrectPicOutputFlag is set equal to HandleCraAsCvsStartFlag.

[0076] – Otherwise, HandleCraAsCvsStartFlag and NoIncorrectPicOutputFlag are both set equal to 0.

[0077] For each GRA picture in the bitstream, the following applies:

[0078] - If the current picture is the first picture in the bitstream in decoding order, or the first picture following the end of a sequence NAL unit in decoding order, the variable NoIncorrectPicOutputFlag is set equal to 1.

[0079] – Otherwise, NoIncorrectPicOutputFlag is set to 0.

[0080] NOTE - For both IRAP pictures and GRA pictures, the above operations are required to identify the CVS in the bitstream.

[0081] 8.1.2 Decoding process for coded pictures

[0082] For the current picture CurrPic, the decoding process is as follows:

[0083] 1. The decoding of NAL units is specified in clause 8.2.

[0084] 2. The procedure in clause 8.3 specifies the following decoding process using the syntax elements in the slice header layer and upper layers:

[0085] – The variables and functions related to the picture sequence count are derived as specified in clause 8.3.1. This only needs to be called for the first slice of a picture.

[0086] – At the beginning of the decoding process for each slice of a non-IDR picture, the decoding process for reference picture list construction specified in clause 8.3.2 is called to derive reference picture list 0 (RefPicList[0]) and reference picture list 1 (RefPicList[1]).

[0087] - Invoke the decoding process for reference picture marking in clause 8.3.3, where a reference picture can be marked as "unused for reference" or "used for long-term reference". This only needs to be called for the first slice of a picture.

[0088] – When the current picture is a CRA picture with NoIncorrectPicOutputFlag equal to 1 or a GRA picture with NoIncorrectPicOutputFlag equal to 1, the decoding process for generating unusable reference pictures specified in subclause 8.3.4 is invoked, which only needs to be invoked for the first slice of the picture.

[0089] – Set PictureOutputFlag as follows:

[0090] – PictureOutputFlag is set equal to 0 if one of the following conditions is true:

[0091] – The current picture is a RASL picture and the NoIncorrectPicOutputFlag of the associated IRAP picture is equal to 1.

[0092] –gra_enabled_flag is equal to 1 and the current picture is a GRA picture with NoIncorrectPicOutputFlag equal to 1.

[0093] – gra_enabled_flag is equal to 1, the current picture is associated with a GRA picture with NoIncorrectPicOutputFlag equal to 1, and PicOrderCntVal of the current picture is less than RpPicOrderCntVal of the associated GRA picture.

[0094] – Otherwise, PictureOutputFlag is set equal to 1.

[0095] 3. [Ed.(YK): Add a call to the decoding process in this article

[0096] 4. After all slices of the current picture have been decoded, the current decoded picture is marked as "used for short-term reference".

[0097] When gra_enabled_flag is equal to 1 and the PicOrderCntVal of the current picture is greater than or equal to the RpPicOrderCntVal of the previous GRA picture in decoding order (where there is no IRAP picture between the current picture and the previous GRA picture in decoding order), the bitstream conformance requirement is that the current decoded picture and subsequent decoded pictures should be an exact match to the pictures produced by starting the decoding process at the previous IRAP picture that precedes the current picture in decoding order.

[0098] As shown above, in VVC draft 5, the syntax element that specifies the recovery point of a decoded picture in output order (ie, recovery_poc_cnt) is signaled using se(v), which means a signed integer 0th order index Golomb coding syntax element with left bit first.

[0099] According to one or more techniques of the present disclosure, signaling of a syntax element (i.e., recovery_poc_cnt) that specifies a recovery point of a decoded picture in output order may be performed using ue(v), which means an unsigned integer 0th order index Golomb coding syntax element with left bit first. For example, VVC Draft 5 may be modified as follows. Additions are shown in italics and deletions are shown in strikethrough.

[0100] 7.3.5 Slice Header Syntax

[0101] 7.3.5.1 Generic Slice Header Syntax

[0102]

[0103] recovery_poc_cnt specifies the recovery point of a decoded picture in output order. If there is a picture picA following the current GRA picture in decoding order in the CVS, and the picture picA has a PicOrderCntVal equal to the PicOrderCntVal of the current GRA picture plus the value of recovery_poc_cnt, then the picture picA is called the recovery point picture. Otherwise, the first picture in the output order with a PicOrderCntVal greater than the PicOrderCntVal of the current GRA picture plus the value of recovery_poc_cnt is called the recovery point picture. In decoding order, the recovery point picture should not precede the current GRA picture. The value of recovery_poc_cnt should be in In the range of 0 to MaxPicOrderCntLsb / 2-1 (including 0 and MaxPicOrderCntLsb / 2-1).

[0104] The variable RpPicOrderCntVal is derived as follows:

[0105] RpPicOrderCntVal = PicOrderCntVal + recovery_poc_cnt (7-40)

[0106] Alternatively, the value of recovery_poc_cnt should be in the range of 0 to MaxPicOrderCntLsb-1 (including 0 and MaxPicOrderCntLsb-1).

[0107] The present disclosure proposes modifications to the behavior of decoders with multiple GRA pictures. For example, if a GRA picture follows a previous GRA picture in decoding order before the recovery point of the previous GRA picture, the subsequent GRA picture and therefore its recovery picture overwrites the previous GRA picture recovery point. In other words, the recovery point picture of the first GRA picture that is signaled as a recovery point picture will no longer be valid (or associated with GRA_NUT(GRA picture)). The recovery point picture of the subsequent GRA picture will be considered as a recovery point picture. A similar situation applies to IRAP pictures that appear between a GRA picture and its recovery point picture in decoding order. For example, the output process will not wait for the recovery point picture, instead, the output process can start from the IRAP picture.

[0108] In some examples, the decoder behavior may be described as follows. An encoder (e.g., video encoder 200) may determine to encode an IRAP picture, or to start another GRA process after signaling a GRA picture with NoIncorrectPicOutputFlag equal to 1 before its associated recovery point picture in decoding order. In this case, the present disclosure proposes replacing the RpPicOrderCntVal of the decoding process with the PicOrderCntVal of the IRAP picture for the IRAP case, and with PicOrderCntVal+recovery_poc_cnt, where PicOrderCntVal and recovery_poc_cnt are the PicOrderCntVal and recovery_poc_cnt of the new GRA picture, and setting NoIncorrectPicOutputFlag equal to 1. For example, a video decoder (eg, video decoder 300 ) may consider a GRA picture with RpPicOrderCntVal with NoIncorrectPicOutputFlag equal to 1 as valid until an IRAP or a new GRA_NUT or its associated recovery point picture (or later POC value) is decoded.

[0109] VVC Draft 5 can be modified as follows (additions are in italics):

[0110] 8.1 General Decoding Process

[0111] 8.1.1 Overview

[0112] …

[0113] For each GRA picture in the bitstream, the following applies:

[0114] - If the current picture is the first picture in the bitstream in decoding order, or the first picture following the end of a sequence NAL unit in decoding order, the variable NoIncorrectPicOutputFlag is set equal to 1.

[0115] – If the current picture precedes, in decoding order, the RpPicOrderCntVal of the previous GRA picture with NoIncorrectPicOutputFlag equal to 1, the variable NoIncorrectPicOutputFlag is set equal to 1.

[0116] – Otherwise, NoIncorrectPicOutputFlag is set equal to 0.

[0117] NOTE – The above operations need to be done for IRAP pictures and GRA pictures to identify CVS in the bitstream.

[0118] As described above, a video decoder may consider the RpPicOrderCntVal of a GRA picture with NoIncorrectPicOutputFlag equal to 1 to be valid until an IRAP or a new GRA_NUT or its associated recovery point picture (or a later POC value) is decoded.

[0119] As described above, the recovery picture may be a picture that is signaled as a picture in which all content will be refreshed (recovered) from the point of the signaled recovery point (recovery_poc_cnt). By signaling a non-negative recovery poc cnt, the present disclosure may eliminate the following situation: in which a recovery point is signaled before the currently decoded picture (i.e., the picture in which the recovery poc cnt is signaled) in the output order, and there are pictures decoded before the current picture with an output order after the recovery picture. Because these pictures after recovery in the output order will not be displayable (not decoded correctly), the decoder may have to skip them and render the pictures that come after the recovery picture in the decoding order after displaying the recovery picture.

[0120] The following examples illustrate some advantages of the techniques of the present disclosure:

[0121] Decoding order: PX:X is the output order.

[0122] ...P8 P9 P10 (with signaling P7 as the recovery point, which is negative 3 relative to 10) P7 P11 P12 ... output order: (the underlined pictures will not be displayed, there is a gap between P7 and P11 (non-smooth playback).

[0123] …P7 P8 P9 P10 P11 P12…

[0124] By utilizing non-negative values ​​to signal recovery poc cnt, the techniques of this disclosure achieve the following:

[0125] Decoding order: PX:X is the output order.

[0126] ...P8 P9 P10 (with signaling P14 as the recovery point, which is positive 4 relative to 10) P11 P12 P13 P14...

[0127] Output order: (underlined pictures will not be displayed, there is no gap after P14 (smooth playback).

[0128] … P10 P11 P12 P13 P14 P15 P16…

[0129] According to the techniques of the present disclosure, a video decoder (e.g., video encoder 200 and / or video decoder 300) may decode syntax elements of a specified target recovery point picture for a current picture via an encoded video bitstream, wherein the target recovery point picture is located at or after the current picture in the display order. As described above, by limiting the target recovery point picture to be located at or after the current picture in the display order, the video decoder may avoid gaps in rendered pictures. Additionally, in examples where syntax elements are decoded using unsigned codes, the modification may result in a reduction in bit rate because unsigned values ​​typically require fewer bits to decode than signed values.

[0130] In general, the present disclosure may involve "signaling" certain information (such as syntax elements). The term "signaling" may generally refer to the transmission of values ​​for syntax elements and / or other data used to decode encoded video data. That is, the video encoder 200 may signal values ​​for syntax elements in a bitstream. Generally, signaling refers to generating values ​​in a bitstream. As described above, the source device 102 may transmit the bitstream to the destination device 116 in substantially real time or not in real time (such as may occur when storing syntax elements to the storage device 112 for later retrieval by the destination device 116).

[0131] Figure 2A and 2B 1 is a conceptual diagram showing an example quadtree binary tree (QTBT) structure 130 and a corresponding coding tree unit (CTU) 132. Solid lines represent quadtree splits, and dashed lines indicate binary tree splits. In each split (i.e., non-leaf) node of the binary tree, a flag is signaled to indicate which split type (i.e., horizontal or vertical) is used, where, in this example, 0 indicates horizontal splitting and 1 indicates vertical splitting. For quadtree splitting, since the quadtree node splits the block horizontally and vertically into 4 sub-blocks of equal size, there is no need to indicate the split type. Therefore, the video encoder 200 can encode the following, and the video decoder 300 can decode the following: syntax elements (such as split information) for the regional tree level (i.e., solid line) of the QTBT structure 130, and syntax elements (such as split information) for the prediction tree level (i.e., dashed line) of the QTBT structure 130. The video encoder 200 may encode video data (such as prediction and transform data) for a CU represented by a terminal leaf node of the QTBT structure 130 , and the video decoder 300 may decode the video data.

[0132] generally, Figure 2B The CTU 132 may be associated with parameters defining the size of blocks corresponding to nodes at the first and second levels of the QTBT structure 130. These parameters may include a CTU size (indicating the size of the CTU 132 in samples), a minimum quadtree size (MinQTSize, which indicates the minimum allowed quadtree leaf node size), a maximum binary tree size (MaxBTSize, which indicates the maximum allowed binary tree root node size), a maximum binary tree depth (MaxBTDepth, which indicates the maximum allowed binary tree depth), and a minimum binary tree size (MinBTSize, which indicates the minimum allowed binary tree leaf node size).

[0133] The root node of the QTBT structure corresponding to the CTU may have four child nodes at the first level of the QTBT structure, each of which may be segmented according to a quadtree segmentation. That is, the node of the first level is a leaf node (without child nodes) or has four child nodes. The example of the QTBT structure 130 represents such a node as including a parent node and a child node with a solid line branch. If the node of the first level is not larger than the maximum allowed binary tree root node size (MaxBTSize), the nodes may be further segmented by the corresponding binary tree. The binary tree splitting of a node may be iterated until the node generated from the split reaches the minimum allowed binary tree leaf node size (MinBTSize) or the maximum allowed binary tree depth (MaxBTDepth). The example of the QTBT structure 130 represents such a node as having a dotted line branch. The binary tree leaf node is called a coding unit (CU), which is used for prediction (e.g., intra-picture or inter-picture prediction) and transformation without any further segmentation. As discussed above, a CU may also be referred to as a "video block" or "block".

[0134] In one example of a QTBT partitioning structure, the CTU size is set to 128x128 (luminance sample and two corresponding 64x64 chrominance samples), MinQTSize is set to 16x16, MaxBTSize is set to 64x64, MinBTSize (for both width and height) is set to 4, and MaxBTDepth is set to 4. Quadtree partitioning is first applied to the CTU to generate a quadtree leaf node. The quadtree leaf node can have a size from 16x16 (i.e., MinQTSize) to 128x128 (i.e., CTU size). If the leaf quadtree node is 128x128, the leaf quadtree node will not be further split by the binary tree because the size exceeds MaxBTSize (i.e., 64x64 in this example). Otherwise, the leaf quadtree node will be further split by the binary tree. Therefore, the quadtree leaf node is also the root node for the binary tree and has a binary tree depth of 0. When the binary tree depth reaches MaxBTDepth (4 in this example), no further splitting is allowed. When a binary tree node has a width equal to MinBTSize (4 in this example), it means that no further horizontal splitting is allowed. Similarly, a binary tree node with a height equal to MinBTSize means that no further vertical splitting is allowed for the binary tree node. As described above, the leaf nodes of the binary tree are called CUs and are further processed according to prediction and transformation without further segmentation.

[0135] Figure 3 is a block diagram illustrating an example video encoder 200 that may perform the techniques of this disclosure. Figure 3The present disclosure is provided for purposes of explanation and should not be considered limiting of the techniques broadly exemplified and described in this disclosure. For purposes of explanation, this disclosure describes the video encoder 200 in the context of video coding standards such as the HEVC video coding standard and the developing H.266 video coding standard. However, the techniques of this disclosure are not limited to these video coding standards and are generally applicable to video encoding and decoding.

[0136] exist Figure 3 In the example of , the video encoder 200 includes a video data memory 230, a mode selection unit 202, a residual generation unit 204, a transform processing unit 206, a quantization unit 208, an inverse quantization unit 210, an inverse transform processing unit 212, a reconstruction unit 214, a filter unit 216, a decoded picture buffer (DPB) 218, and an entropy coding unit 220. Any one or all of the video data memory 230, the mode selection unit 202, the residual generation unit 204, the transform processing unit 206, the quantization unit 208, the inverse quantization unit 210, the inverse transform processing unit 212, the reconstruction unit 214, the filter unit 216, the DPB 218, and the entropy coding unit 220 may be implemented in one or more processors or in processing circuits. In addition, the video encoder 200 may include additional or alternative processors or processing circuits to perform these and other functions.

[0137] The video data memory 230 may store video data to be encoded by the components of the video encoder 200. The video encoder 200 may receive video data from, for example, the video source 104 ( Figure 1 ) receives the video data stored in the video data memory 230. DPB 218 can act as a reference picture memory, which stores reference video data for use when subsequent video data is predicted by the video encoder 200. Video data memory 230 and DPB 218 can be formed by any one of various memory devices, such as dynamic random access memory (DRAM) (including synchronous DRAM (SDRAM)), magnetoresistive RAM (MRAM), resistive RAM (RRAM), or other types of memory devices. Video data memory 230 and DPB 218 can be provided by the same memory device or separate memory devices. In various examples, video data memory 230 can be on chip with other components of video encoder 200 (as shown), or off chip relative to those components.

[0138] In the present disclosure, references to the video data memory 230 should not be interpreted as limited to memory internal to the video encoder 200 (unless specifically described as such), or to memory external to the video encoder 200 (unless specifically described as such). Rather, references to the video data memory 230 should be understood as a reference memory that stores video data received by the video encoder 200 for encoding (e.g., video data for a current block to be encoded). Figure 1 The memory 106 may also provide temporary storage for outputs from the various units of the video encoder 200 .

[0139] Shows Figure 3 The various units of the video encoder 200 are provided to help understand the operations performed by the video encoder 200. These units may be implemented as fixed-function circuits, programmable circuits, or a combination thereof. Fixed-function circuits refer to circuits that provide specific functions and are pre-set with respect to the operations that can be performed. Programmable circuits refer to circuits that can be programmed to perform various tasks and provide flexible functions with the operations that can be performed. For example, a programmable circuit may execute software or firmware that causes the programmable circuit to operate in a manner defined by the instructions of the software or firmware. Fixed-function circuits may execute software instructions (e.g., to receive parameters or output parameters), but the types of operations performed by fixed-function circuits are generally immutable. In some examples, one or more of these units may be different circuit blocks (fixed-function or programmable), and in some examples, one or more units may be integrated circuits.

[0140] The video encoder 200 may include an arithmetic logic unit (ALU), an elementary function unit (EFU), a digital circuit, an analog circuit, and / or a programmable core formed by a programmable circuit. In an example in which the operation of the video encoder 200 is performed using software executed by a programmable circuit, the memory 106 ( Figure 1 ) may store object code for software that the video encoder 200 receives and executes, or another memory (not shown) within the video encoder 200 may store such instructions.

[0141] The video data memory 230 is configured to store the received video data. The video encoder 200 may retrieve the picture of the video data from the video data memory 230 and provide the video data to the residual generation unit 204 and the mode selection unit 202. The video data in the video data memory 230 may be the original video data to be encoded.

[0142] The mode selection unit 202 includes a motion estimation unit 222, a motion compensation unit 224, and an intra prediction unit 226. The mode selection unit 202 may include additional functional units to perform video prediction according to other prediction modes. As an example, the mode selection unit 202 may include a palette unit, an intra-block copy unit (which may be part of the motion estimation unit 222 and / or the motion compensation unit 224), an affine unit, a linear model (LM) unit, etc.

[0143] The mode selection unit 202 generally coordinates multiple encoding passes to test combinations of encoding parameters and the resulting rate-distortion values ​​for such combinations. The encoding parameters may include partitioning of a CTU into CUs, a prediction mode for a CU, a transform type for residual data of a CU, a quantization parameter for residual data of a CU, etc. The mode selection unit 202 may ultimately select a combination of encoding parameters that has a better rate-distortion value than other tested combinations.

[0144] The video encoder 200 may partition the picture retrieved from the video data memory 230 into a series of CTUs, and encapsulate one or more CTUs in a slice. The mode selection unit 202 may partition the CTUs of the picture according to a tree structure (such as the QTBT structure or quadtree structure of the HEVC described above). As described above, the video encoder 200 may form one or more CUs by partitioning the CTUs according to the tree structure. Such CUs may also be generally referred to as "video blocks" or "blocks".

[0145] Typically, the mode selection unit 202 also controls its components (e.g., the motion estimation unit 222, the motion compensation unit 224, and the intra prediction unit 226) to generate a prediction block for the current block (e.g., the current CU, or the overlapping portion of the PU and TU in HEVC). In order to inter-predict the current block, the motion estimation unit 222 may perform a motion search to identify one or more closely matching reference blocks in one or more reference pictures (e.g., one or more previously decoded pictures stored in the DPB 218). Specifically, the motion estimation unit 222 may calculate a value representing the degree of similarity of the potential reference block to the current block, for example, based on the sum of absolute differences (SAD), the sum of squared differences (SSD), the mean absolute difference (MAD), the mean squared difference (MSD), etc. The motion estimation unit 222 may typically perform these calculations using the sample-by-sample difference between the current block and the reference block under consideration. The motion estimation unit 222 may identify the reference block with the lowest value resulting from these calculations, which indicates the reference block that most closely matches the current block.

[0146] The motion estimation unit 222 may form one or more motion vectors (MVs) that define the position of the reference block in the reference picture relative to the position of the current block in the current picture. The motion estimation unit 222 may then provide the motion vectors to the motion compensation unit 224. For example, for unidirectional inter prediction, the motion estimation unit 222 may provide a single motion vector, while for bidirectional inter prediction, the motion estimation unit 222 may provide two motion vectors. The motion compensation unit 224 may then use the motion vectors to generate a prediction block. For example, the motion compensation unit 224 may use the motion vectors to retrieve data for the reference block. As another example, if the motion vectors have fractional sample precision, the motion compensation unit 224 may interpolate the values ​​for the prediction block according to one or more interpolation filters. In addition, for bidirectional inter prediction, the motion compensation unit 224 may retrieve data for two reference blocks identified by the corresponding motion vectors and combine the retrieved data, for example, by sample-by-sample averaging or weighted averaging.

[0147] As another example, for intra prediction or intra prediction decoding, the intra prediction unit 226 can generate a prediction block based on samples adjacent to the current block. For example, for directional mode, the intra prediction unit 226 can generally mathematically combine the values ​​of the adjacent samples and fill these calculated values ​​across the current block in a defined direction to produce a prediction block. As another example, for DC mode, the intra prediction unit 226 can calculate the average value of the adjacent samples of the current block and generate a prediction block to include the obtained average value for each sample of the prediction block.

[0148] The mode selection unit 202 provides the prediction block to the residual generation unit 204. The residual generation unit 204 receives the original uncoded version of the current block from the video data memory 230 and receives the prediction block from the mode selection unit 202. The residual generation unit 204 calculates the sample-by-sample difference between the current block and the prediction block. The resulting sample-by-sample difference defines a residual block for the current block. In some examples, the residual generation unit 204 may also determine the difference between the sample values ​​in the residual block to generate the residual block using residual differential pulse coding modulation (RDPCM). In some examples, the residual generation unit 204 may be formed using one or more subtractor circuits that perform binary subtraction.

[0149] In an example where the mode selection unit 202 partitions the CU into PUs, each PU may be associated with a luma prediction unit and a corresponding chroma prediction unit. The video encoder 200 and the video decoder 300 may support PUs of various sizes. As noted above, the size of the CU may refer to the size of the luma coding block of the CU, and the size of the PU may refer to the size of the luma prediction unit of the PU. Assuming that the size of a particular CU is 2Nx2N, the video encoder 200 may support PU sizes of 2Nx2N or NxN for intra-frame prediction, and symmetrical PU sizes of 2Nx2N, 2NxN, Nx2N, NxN, or similar sizes for inter-frame prediction. The video encoder 200 and the video decoder 300 may also support asymmetric partitioning for PU sizes of 2NxnU, 2NxnD, nLx2N, and nRx2N for inter-frame prediction.

[0150] In an example where the mode selection unit does not further split the CU into PUs, each CU may be associated with a luma coding block and a corresponding chroma coding block. As described above, the size of a CU may refer to the size of the luma coding block of the CU. The video encoder 200 and the video decoder 300 may support a CU size of 2Nx2N, 2NxN, or Nx2N.

[0151] For other video coding techniques (such as intra-block copy mode coding, affine mode coding, and linear model (LM) mode coding, to name a few examples), the mode selection unit 202 generates a prediction block for the current block being encoded via a corresponding unit associated with the coding technique. In some examples (such as palette mode coding), the mode selection unit 202 may not generate a prediction block, but instead generate syntax elements indicating how to reconstruct the block based on the selected palette. In such a mode, the mode selection unit 202 can provide these syntax elements to the entropy coding unit 220 for encoding.

[0152] As described above, the residual generation unit 204 receives video data for a current block and a corresponding prediction block. The residual generation unit 204 then generates a residual block for the current block. To generate the residual block, the residual generation unit 204 calculates the sample-by-sample difference between the prediction block and the current block.

[0153] The transform processing unit 206 applies one or more transforms to the residual block to generate a block of transform coefficients (referred to herein as a "transform coefficient block"). The transform processing unit 206 can apply various transforms to the residual block to form a transform coefficient block. For example, the transform processing unit 206 can apply a discrete cosine transform (DCT), a directional transform, a Karhunen-Loeve transform (KLT), or a conceptually similar transform to the residual block. In some examples, the transform processing unit 206 can perform multiple transforms on the residual block, for example, a primary transform and a secondary transform (such as a rotation transform). In some examples, the transform processing unit 206 does not apply a transform to the residual block.

[0154] The quantization unit 208 may quantize the transform coefficients in the transform coefficient block to produce a quantized transform coefficient block. The quantization unit 208 may quantize the transform coefficients of the transform coefficient block according to a quantization parameter (QP) value associated with the current block. The video encoder 200 (e.g., via the mode selection unit 202) may adjust the degree of quantization applied to the transform coefficient block associated with the current block by adjusting the QP value associated with the CU. Quantization may cause a loss of information, and therefore, the quantized transform coefficients may have a lower precision than the original transform coefficients produced by the transform processing unit 206.

[0155] The inverse quantization unit 210 and the inverse transform processing unit 212 may apply inverse quantization and inverse transform, respectively, to the quantized transform coefficient block to reconstruct a residual block from the transform coefficient block. The reconstruction unit 214 may generate a reconstructed block corresponding to the current block (although potentially with some degree of distortion) based on the reconstructed residual block and the prediction block generated by the mode selection unit 202. For example, the reconstruction unit 214 may add samples of the reconstructed residual block to corresponding samples of the prediction block generated by the mode selection unit 202 to generate a reconstructed block.

[0156] Filter unit 216 may perform one or more filter operations on the reconstructed block. For example, filter unit 216 may perform a deblocking operation to reduce blocking artifacts along the edge of the CU. In some examples, the operations of filter unit 216 may be skipped.

[0157] The video encoder 200 stores the reconstructed blocks in the DPB 218. For example, in an example where the operation of the filter unit 216 is not required, the reconstruction unit 214 can store the reconstructed blocks in the DPB 218. In an example where the operation of the filter unit 216 is required, the filter unit 216 can store the filtered reconstructed blocks in the DPB 218. The motion estimation unit 222 and the motion compensation unit 224 can retrieve the reference picture formed from the reconstructed (and potentially filtered) blocks from the DPB 218 to perform inter-frame prediction on the blocks of the subsequently encoded pictures. In addition, the intra-frame prediction unit 226 can use the reconstructed blocks of the current picture in the DPB 218 to perform intra-frame prediction on other blocks in the current picture.

[0158] In general, the entropy coding unit 220 may entropy encode syntax elements received from other functional components of the video encoder 200. For example, the entropy coding unit 220 may entropy encode the quantized transform coefficient blocks from the quantization unit 208. As another example, the entropy coding unit 220 may entropy encode the prediction syntax elements (e.g., motion information for inter-frame prediction or intra-frame mode information for intra-frame prediction) from the mode selection unit 202. The entropy coding unit 220 may perform one or more entropy coding operations on syntax elements as another example of video data to generate entropy-encoded data. For example, the entropy coding unit 220 may perform a context-adaptive variable length coding (CAVLC) operation, a CABAC operation, a variable to variable (V2V) length coding operation, a syntax-based context-adaptive binary arithmetic coding (SBAC) operation, a probability interval partitioning entropy (PIPE) coding operation, an exponential Golomb coding operation, or another type of entropy coding operation on the data. In some examples, the entropy coding unit 220 may operate in a bypass mode in which the syntax elements are not entropy encoded.

[0159] The video encoder 200 may output a bitstream including entropy-encoded syntax elements required for reconstructing a block of a slice or picture. Specifically, the entropy encoding unit 220 may output a bitstream.

[0160] The above operations are described with respect to blocks. Such descriptions should be understood as operations for luma coding blocks and / or chroma coding blocks. As described above, in some examples, the luma coding blocks and chroma coding blocks are the luma components and chroma components of a CU. In some examples, the luma coding blocks and chroma coding blocks are the luma components and chroma components of a PU.

[0161] In some examples, operations performed with respect to luma coding blocks need not be repeated for chroma coding blocks. As an example, operations for identifying motion vectors (MVs) and reference pictures for luma coding blocks need not be repeated to identify MVs and reference pictures for chroma blocks. Specifically, the MVs for luma coding blocks may be scaled to determine MVs for chroma blocks, and the reference pictures may be the same. As another example, the intra prediction process may be the same for luma coding blocks and chroma coding blocks.

[0162] Video encoder 200 represents an example of a device configured to encode video data, the device comprising: a memory configured to store the video data; and one or more processing units implemented in circuits and configured to: encode, in an encoded video bitstream and for a current picture, a syntax element specifying a target recovery point picture, wherein the target recovery point picture is located at or after the current picture in a display order.

[0163] Figure 4 is a block diagram illustrating an example video decoder 300 that may perform the techniques of this disclosure. Figure 4 It is provided for the purpose of explanation and does not limit the techniques extensively illustrated and described in this disclosure. For the purpose of explanation, this disclosure describes a video decoder 300 according to the techniques of JEM, VVC, and HEVC. However, the techniques of this disclosure can be performed by a video decoding device configured for other video decoding standards.

[0164] exist Figure 4 In the example of , the video decoder 300 includes a coded picture buffer (CPB) memory 320, an entropy decoding unit 302, a prediction processing unit 304, an inverse quantization unit 306, an inverse transform processing unit 308, a reconstruction unit 310, a filter unit 312, and a decoded picture buffer (DPB) 134. Any or all of the CPB memory 320, the entropy decoding unit 302, the prediction processing unit 304, the inverse quantization unit 306, the inverse transform processing unit 308, the reconstruction unit 310, the filter unit 312, and the DPB 134 may be implemented in one or more processors or in processing circuitry. Furthermore, the video decoder 300 may include additional or alternative processors or processing circuitry to perform these and other functions.

[0165] The prediction processing unit 304 includes a motion compensation unit 316 and an intra prediction unit 318. The prediction processing unit 304 may include an addition unit to perform prediction according to other prediction modes. As an example, the prediction processing unit 304 may include a palette unit, an intra-block copy unit (which may form part of the motion compensation unit 316), an affine unit, a linear model (LM) unit, etc. In other examples, the video decoder 300 may include more, fewer, or different functional components.

[0166] CPB memory 320 may store video data, such as an encoded video bitstream, to be decoded by components of video decoder 300. For example, the video bitstream may be obtained from computer readable medium 110 ( Figure 1 ) obtains video data stored in CPB memory 320. CPB memory 320 may include a CPB that stores coded video data (e.g., syntax elements) from a coded video bitstream. In addition, CPB memory 320 may store video data other than syntax elements of decoded pictures, such as temporary data representing outputs from various units of video decoder 300. DPB 314 typically stores decoded pictures, and video decoder 300 may output decoded pictures, and / or use decoded pictures as reference video data when decoding subsequent data or pictures of the coded video bitstream. CPB memory 320 and DPB 314 may be formed by any of a variety of memory devices, such as DRAM, including SDRAM, MRAM, RRAM or other types of memory devices. CPB memory 320 and DPB 314 may be provided by the same memory device or separate memory devices. In various examples, CPB memory 320 may be on-chip with other components of video decoder 300, or off-chip relative to those components.

[0167] Additionally or alternatively, in some examples, video decoder 300 may retrieve the video from memory 120 ( Figure 1 ) to retrieve the decoded video data. That is, memory 120 may utilize CPB memory 320 to store data as discussed above. Likewise, when some or all of the functionality of video decoder 300 is implemented in software to be executed by processing circuitry of video decoder 300, memory 120 may store instructions to be executed by video decoder 300.

[0168] Shows Figure 4 The various units shown in FIG. 3 are used to help understand the operations performed by the video decoder 300. These units may be implemented as fixed function circuits, programmable circuits, or a combination thereof. Figure 3, fixed-function circuits refer to circuits that provide specific functions and are pre-set with respect to the operations that can be performed. Programmable circuits refer to circuits that can be programmed to perform various tasks and provide flexible functions with respect to the operations that can be performed. For example, a programmable circuit can execute software or firmware that causes the programmable circuit to operate in a manner defined by the instructions of the software or firmware. Fixed-function circuits can execute software instructions (e.g., to receive parameters or output parameters), but the types of operations performed by fixed-function circuits are generally immutable. In some examples, one or more of these units may be different circuit blocks (fixed-function or programmable), and in some examples, one or more units may be integrated circuits.

[0169] The video decoder 300 may include an ALU, an EFU, a digital circuit, an analog circuit, and / or a programmable core formed from programmable circuits. In examples where the operation of the video decoder 300 is performed by software executed on the programmable circuits, an on-chip or off-chip memory may store instructions (e.g., object code) of the software that the video decoder 300 receives and executes.

[0170] The entropy decoding unit 302 may receive the encoded video data from the CPB and entropy decode the video data to regenerate the syntax elements. The prediction processing unit 304, the inverse quantization unit 306, the inverse transform processing unit 308, the reconstruction unit 310, and the filter unit 312 may generate decoded video data based on the syntax elements extracted from the bitstream.

[0171] Typically, the video decoder 300 reconstructs a picture on a block-by-block basis. The video decoder 300 may perform a reconstruction operation on each block individually (wherein a block currently being reconstructed (ie, decoded) may be referred to as a "current block").

[0172] The entropy decoding unit 302 may entropy decode syntax elements defining the quantized transform coefficients of the quantized transform coefficient block and transform information such as a quantization parameter (QP) and / or a transform mode indication. The inverse quantization unit 306 may use the QP associated with the quantized transform coefficient block to determine a degree of quantization and, likewise, determine a degree of inverse quantization for the inverse quantization unit 306 to apply. The inverse quantization unit 306 may, for example, perform a bitwise left shift operation to inverse quantize the quantized transform coefficients. The inverse quantization unit 306 may thereby form a transform coefficient block including the transform coefficients.

[0173] After the inverse quantization unit 306 forms the transform coefficient block, the inverse transform processing unit 308 may apply one or more inverse transforms to the transform coefficient block to generate a residual block associated with the current block. For example, the inverse transform processing unit 308 may apply an inverse DCT, an inverse integer transform, an inverse Karhunen-Loeve transform (KLT), an inverse rotational transform, an inverse directional transform, or another inverse transform to the transform coefficient block.

[0174] In addition, prediction processing unit 304 generates a prediction block based on the prediction information syntax elements entropy decoded by entropy decoding unit 302. For example, if the prediction information syntax elements indicate that the current block is inter-predicted, motion compensation unit 316 can generate a prediction block. In this case, the prediction information syntax elements can indicate a reference picture in DPB 314 from which to retrieve the reference block, and a motion vector that identifies the position of the reference block in the reference picture relative to the position of the current block in the current picture. Motion compensation unit 316 can generally generate a prediction block in the same manner as described for motion compensation unit 224 ( Figure 3 )The inter-frame prediction process is performed in a manner substantially similar to that described in detail above.

[0175] As another example, if the prediction information syntax element indicates that the current block is intra-predicted, the intra-prediction unit 318 may generate a prediction block according to the intra-prediction mode indicated by the prediction information syntax element. Again, the intra-prediction unit 318 may generally generate a prediction block in the same manner as described with respect to the intra-prediction unit 226 ( Figure 3 The intra prediction process is performed in a substantially similar manner as described in the foregoing description. The intra prediction unit 318 may retrieve data of neighboring samples of the current block from the DPB 314.

[0176] The reconstruction unit 310 may reconstruct the current block using the prediction block and the residual block. For example, the reconstruction unit 310 may reconstruct the current block by adding samples of the residual block to corresponding samples of the prediction block.

[0177] The filter unit 312 may perform one or more filter operations on the reconstructed block. For example, the filter unit 312 may perform a deblocking operation to reduce blocking artifacts along the edges of the reconstructed block. The operations of the filter unit 312 may not necessarily be performed in all examples.

[0178] The video decoder 300 may store the reconstructed blocks in the DPB 314. As discussed above, the DPB 314 may provide reference information (such as samples of the current picture for intra prediction and previously decoded pictures for subsequent motion compensation) to the prediction processing unit 304. In addition, the video decoder 300 may output the decoded pictures from the DPB 314 for use in, for example, Figure 1 Subsequent presentation on a display device 118 of the display device.

[0179] In this manner, the video decoder 300 represents an example of a video decoding device, the video decoding device comprising: a memory configured to store video data; and one or more processing units implemented in circuits and configured to: decode a syntax element specifying a target recovery point picture according to a decoded video bitstream and for a current picture, wherein the target recovery point picture is located at or after the current picture in a display order. Similarly, the video decoder 300 represents an example of a video decoding device, the video decoding device comprising: a memory configured to store video data; and one or more processing units implemented in circuits and configured to: decode a first progressive random access (GRA) picture having a recovery point according to a decoded video bitstream; decode a second GRA picture having a recovery point according to the decoded video bitstream; and in response to determining that the second GRA picture is located between the first GRA picture and the recovery point of the first GRA picture, replace the recovery point of the first GRA picture with the recovery point of the second GRA picture.

[0180] Figure 5 2 is a flowchart illustrating an example method for encoding a current block. The current block may include a current CU. Although with respect to the video encoder 200 ( Figure 1 and 3 ), but it should be understood that other devices may be configured to perform the same Figure 5 A similar approach to the one used in this paper.

[0181] In this example, the video encoder 200 initially predicts the current block (350). For example, the video encoder 200 may form a prediction block for the current block. The video encoder 200 may then calculate a residual block for the current block (532). To calculate the residual block, the video encoder 200 may calculate the difference between the original unencoded block and the prediction block for the current block. The video encoder 200 may then transform and quantize the coefficients of the residual block (354). Next, the video encoder 200 may scan the quantized transform coefficients of the residual block (356). During or after the scan, the video encoder 200 may entropy encode the coefficients (358). For example, the video encoder 200 may encode the coefficients using CAVLC or CABAC. The video encoder 200 may then output the entropy coded data of the block (360).

[0182] Figure 6 is a flowchart illustrating an example method for decoding a current block of video data. The current block may include a current CU. Although with respect to the video decoder 300 ( Figure 1 and Figure 4), but it should be understood that other devices may be configured to perform the same Figure 6 A similar approach to the one used in this paper.

[0183] The video decoder 300 may receive entropy coded data for a current block, such as entropy coded prediction information and entropy coded data for coefficients of a residual block corresponding to the current block (370). The video decoder 300 may entropy decode the entropy coded data to determine prediction information for the current block and regenerate coefficients of the residual block (372). The video decoder 300 may predict the current block (374), for example, using an intra-prediction mode or an inter-prediction mode as indicated by the prediction information for the current block, to calculate a prediction block for the current block. The video decoder 300 may then inverse scan the regenerated coefficients (376) to create a block of quantized transform coefficients. The video decoder 300 may then inverse quantize and inverse transform the coefficients to generate a residual block (378). Finally, the video decoder 300 may decode the current block by combining the prediction block and the residual block (380).

[0184] Figure 7 2 is a flowchart illustrating an example technique for encoding a progressive random access (GRA) recovery point in video decoding in accordance with one or more techniques of the present disclosure. Figure 1 and Figure 4 ), but it should be understood that other devices may be configured to perform the same Figure 7 A similar approach to the one used in this paper.

[0185] The video encoder 200 may determine to specify random access points in a picture of a current sequence of video data. For example, the video encoder 200 may determine to specify random access points at regular intervals (e.g., every 30 seconds, every 1 minute, etc.) in the sequence of video data. Additionally, the video encoder 200 may determine to specify random access points as a response to a scene cut in a source sequence or a response to an update request within a fast update picture.

[0186] In addition to specifying a random access point, the video encoder 200 may also specify a recovery point. If the random access point is the same as the recovery point, the random access operation is instantaneous; otherwise, it is progressive.

[0187] To enable progressive random access (GRA), the video encoder 200 may select a target recovery point picture (702) for a current picture in a current sequence of pictures and at or after the current picture in display order. For example, the mode selection unit 202 of the video encoder 200 may identify a picture sequence count (POC) value of the target recovery point picture. The identified POC value may be referred to as recoveryPointPocVal.

[0188] The video encoder 200 may signal an indication of the selected target recovery point picture in the decoded video bitstream. Instead of signaling the identified POC value, the video encoder 200 may signal the difference between the identified POC value and the POC value of the current picture (PicOrderCntVal). For example, the video encoder 200 may determine the difference between the identified POC value and the POC value of the current picture according to the following equation, where:

[0189] recovery_poc_cnt=recoveryPointPocVal–PicOrderCntVal

[0190] Where recoveryPointPocVal is the POC value of the target recovery point picture, PicOrderCntVal is the POC value of the current picture, and recovery_poc_cnt is the difference between the POC value of the target recovery point picture and the POC value of the current picture.

[0191] The video encoder 200 may select a target recovery point picture so that the value of recovery_poc_cnt satisfies certain constraints. For example, the video encoder 200 may select a target recovery point picture so that the value of recovery_poc_cnt is in the range of zero to MaxPicOrderCntLsb (e.g., a representation of the maximum picture order count, such as the least significant bit of the maximum picture order count), including zero and MaxPicOrderCntLsb.

[0192] As discussed above, the video encoder 200 may signal the difference between the identified POC value and the POC value of the current picture. Also as discussed above, and in accordance with one or more techniques of the present disclosure, the video encoder 200 may signal the target recovery point picture using a syntax element having an unsigned value. For example, the mode selection unit 202 may cause the entropy encoding unit 220 to encode (704) the value of the target recovery point picture specified for the current picture in the current sequence of pictures in the decoded video bitstream and as an unsigned integer 0th order index Golomb decoding syntax element with left bit first. The syntax element may be named recovery_poc_cnt or a similar name.

[0193] The entropy coding unit 220 may encode the syntax elements in the header syntax structure of the decoded video bitstream referenced by the current picture. For example, the entropy coding unit 220 may encode the syntax elements in the slice header or the picture header syntax structure.

[0194] By using syntax elements with unsigned values ​​to signal the target recovery point picture, the video encoder 200 can eliminate the undesirable situation of introducing gaps in the output of the rendered picture. In addition, using syntax elements with unsigned values ​​to signal the target recovery point picture can reduce the amount of data used by the video encoder 200 to signal the target recovery point picture, which can improve decoding efficiency.

[0195] Figure 8 is a flow chart illustrating an example technique for decoding a progressive random access (GRA) recovery point in video decoding in accordance with one or more techniques of this disclosure. Figure 1 and Figure 4 ), but it should be understood that other devices may be configured to perform the same Figure 8 A similar approach to the one used in this paper.

[0196] In accordance with one or more techniques of the present disclosure and as discussed above, the video decoder 300 may signal a target recovery point picture using a syntax element having an unsigned value. For example, the entropy decoding unit 302 may decode (802) a value of a target recovery point picture for a current picture in a current sequence of pictures based on a decoded video bitstream and as an unsigned integer 0th order index Golomb decoding syntax element with left bit first. The target recovery point picture may be located at or after the current picture in the display order. For example, the target recovery point picture may have a POC value greater than or equal to the POC value of the current picture.

[0197] The entropy decoding unit 302 may decode the syntax elements according to the header syntax structure of the decoded video bitstream referenced by the current picture. For example, the entropy decoding unit 302 may decode the syntax elements according to the slice header or picture header syntax structure.

[0198] The video decoder 300 may verify whether the value of the syntax element satisfies certain constraints. For example, the video decoder 300 may verify that the value of the syntax element is within the range of 0 to MaxPicOrderCntLsb (including 0 and MaxPicOrderCntLsb).

[0199] By using syntax elements with unsigned values ​​to signal the target recovery point picture, the video decoder 300 can eliminate the undesirable situation of introducing gaps in the output of the rendered picture. In addition, using syntax elements with unsigned values ​​to signal the target recovery point picture can reduce the amount of data used by the video decoder 300 to signal the target recovery point picture, which can improve decoding efficiency.

[0200] The video decoder 300 may resume decoding of pictures of the current sequence at the target resumption point picture (804). For example, in response to receiving a user input indicating a requested destination of a seek operation, the video decoder 300 may identify a random access point closest to the requested destination of the seek operation and start or resume decoding of pictures of the sequence at the target resumption point picture.

[0201] The following numbered examples may illustrate one or more aspects of the present disclosure:

[0202] Example 1. A method of decoding video data, the method comprising: decoding, via a decoded video bitstream and for a current picture, a syntax element that specifies a target recovery point picture, wherein the target recovery point picture is located at or after the current picture in display order; and decoding the current picture based on the syntax element.

[0203] Example 2. The method of claim 1, wherein decoding the syntax element comprises decoding the syntax element using an unsigned code.

[0204] Example 3. The method of claim 2, wherein decoding the syntax element using the unsigned code comprises decoding the syntax element as a Golomb-coded syntax element with an unsigned integer 0th order index with left bits leading.

[0205] Example 4. The method according to any of claims 1 to 3, wherein the syntax element is a recovery_poc_cnt syntax element.

[0206] Example 5. A method of decoding video data, the method comprising: obtaining information for a first progressive random access (GRA) picture having a recovery point picture from a decoded video bitstream; obtaining information for a second GRA picture having a recovery point picture from the decoded video bitstream; and in response to determining that the second GRA picture is between the first GRA picture and the recovery point picture of the first GRA picture, replacing the recovery point picture of the first GRA picture with the recovery point picture of the second GRA picture.

[0207] Example 6. The method of claim 5, further comprising determining that the recovery point picture of the first GRA picture is valid until the second GRA picture or the recovery point picture of the second GRA picture is decoded.

[0208] Example 7. The method of claim 5 or claim 6, further comprising determining that a recovery point picture of the first GRA picture is valid until an intra random access point (IRAP) picture is decoded.

[0209] Example 8. The method of any of claims 5 to 7, wherein the recovery point picture of the first GRA picture is specified by a first RpPicOrderCntVal variable, and wherein the recovery point picture of the second GRA picture is specified by a second RpPicOrderCntVal variable.

[0210] Example 9. The method of claim 8, wherein replacing the recovery point picture of the first GRA picture with the recovery point picture of the second GRA picture comprises replacing the value of the first RpPicOrderCntVal variable with the value of the second RpPicOrderCntVal variable.

[0211] Example 10. The method of any of claims 1 to 9, wherein decoding comprises decoding.

[0212] Example 11. The method of any of claims 1 to 10, wherein decoding comprises encoding.

[0213] Example 12. An apparatus for decoding video data, the apparatus comprising one or more units for performing the method according to any of claims 1 to 11.

[0214] Example 13. The apparatus of claim 12, wherein the one or more units include one or more processors implemented in circuitry.

[0215] Example 14. The apparatus of any of claims 12 and 13, further comprising: a memory for storing the video data.

[0216] Example 15. The apparatus of any of claims 12 to 14, further comprising: a display configured to display the decoded video data.

[0217] Example 16. The device of any of claims 12-15, wherein the device comprises one or more of a camera, a computer, a mobile device, a broadcast receiver device, or a set-top box.

[0218] Example 17. The apparatus of any of Claims 12 to 16, wherein the apparatus comprises a video decoder.

[0219] Example 18. The apparatus of any of Claims 12 to 17, wherein the apparatus comprises a video encoder.

[0220] Example 19. A computer-readable storage medium having instructions stored thereon, the instructions, when executed, causing one or more processors to perform the method of any of claims 1-11.

[0221] It is to be appreciated that, depending on the example, certain actions or events of any of the techniques described herein may be performed in a different order, may be added, combined, or omitted entirely (e.g., not all described actions or events are necessary for the practice of the techniques). Additionally, in some examples, actions or events may be performed concurrently rather than sequentially, such as through multithreading, interrupt handling, or multiple processors.

[0222] In one or more examples, the functions described may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions may be stored or transmitted on a computer-readable medium as one or more instructions or codes and executed by a hardware-based processing unit. Computer-readable media may include computer-readable storage media corresponding to tangible media such as data storage media or communication media, including any media that facilitates the transfer of a computer program from one place to another, for example, according to a communication protocol. In this manner, computer-readable media may generally correspond to: (1) a non-transitory tangible computer-readable storage medium; or (2) a communication medium such as a signal or carrier wave. Data storage media may be any available media that can be accessed by one or more computers or one or more processors to retrieve instructions, codes, and / or data structures for the implementation of the techniques described in the present disclosure. A computer program product may include a computer-readable medium.

[0223] By way of example and not limitation, such computer-readable storage media may include RAM, ROM, EEPROM, CD-ROM or other optical disk storage, disk storage or other magnetic storage devices, flash memory, or any other medium that can be used to store the desired program code in the form of instructions or data structures and can be accessed by a computer. In addition, any connection is appropriately referred to as a computer-readable medium. For example, if the instruction is sent from a website, server or other remote source using a coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL) or wireless technology (such as infrared, radio and microwave), the coaxial cable, fiber optic cable, twisted pair, DSL or wireless technology (such as infrared, radio and microwave) is included in the definition of the medium. However, it should be understood that computer-readable storage media and data storage media do not include connections, carrier waves, signals or other temporary media, but are instead directed to non-temporary tangible storage media. Disks and optical disks as used herein include compact discs (CDs), laser optical disks, optical disks, digital versatile discs (DVDs), floppy disks and blue-ray discs, wherein disks usually copy data magnetically, while optical disks use lasers to optically copy data. Combinations of the above should also be included within the scope of computer-readable media.

[0224] Instructions may be executed by one or more processors, such as one or more digital signal processors (DSPs), general-purpose microprocessors, application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other equivalent integrated or discrete logic circuits. Thus, the terms "processor" and "processing circuitry" as used herein may refer to any of the foregoing structures or any other structure suitable for implementation of the techniques described herein. Additionally, in some aspects, the functionality described herein may be provided within dedicated hardware and / or software modules configured for encoding and decoding, or incorporated into a combined codec. Furthermore, the techniques may be fully implemented in one or more circuits or logic elements.

[0225] The techniques of the present disclosure may be implemented in a variety of devices or apparatuses, including a wireless handset, an integrated circuit (IC), or a set of ICs (e.g., a chipset). Various components, modules, or units are described in the present disclosure to emphasize aspects of the functionality of a device configured to perform the disclosed techniques, but do not necessarily require implementation by different hardware units. Rather, as described above, the various units may be combined in a codec hardware unit, or provided by a collection of interoperable hardware units including one or more processors as described above in combination with appropriate software and / or firmware.

[0226] Various examples have been described. These and other examples are within the scope of the following claims.

Claims

1. A method for decoding video data, the method comprising: decoding, according to a decoded video bitstream and as an unsigned integer 0th order index Golomb decoding syntax element with left bit first, a first value specifying a recovery point picture for a first progressive random access (GRA) picture in a current sequence and a second value specifying a recovery point picture for a second GRA picture in the current sequence, wherein the recovery point picture of the first GRA picture is located at or after the first GRA picture in display order, and the recovery point picture of the second GRA picture is located at or after the second GRA picture in display order, wherein the first value and the second value are both in a range of zero to MaxPicOrderCntLsb-1, inclusive, and wherein decoding the first value or the second value comprises: decoding the syntax element according to a header syntax structure of the decoded video bitstream referenced by the first GRA picture or the second GRA picture; Determine that the second GRA picture is located between the first GRA picture and a restoration point picture of the first GRA picture; In response to determining that the second GRA picture is located between the first GRA picture and the restoration point picture of the first GRA picture, replacing the restoration point picture of the first GRA picture with the restoration point picture of the second GRA picture; and The decoding of the pictures of the current sequence is resumed at a recovery point picture of the second GRA picture.

2. The method according to claim 1, further comprising: determining a picture order count (POC) value of a recovery point picture of the first GRA picture based on the first value specifying the recovery point picture of the first GRA picture and a POC value of the first GRA picture; as well as A POC value of a restoration point picture of the second GRA picture is determined based on the second value specifying the restoration point picture of the second GRA picture and the POC value of the second GRA picture.

3. The method according to claim 1, wherein: The syntax element is the recovery_poc_cnt syntax element.

4. The method according to claim 1, further comprising: It is determined that the recovery point picture of the first GRA picture is valid until the second GRA picture or the recovery point picture of the second GRA picture is decoded.

5. The method according to claim 1 or 4, further comprising: A recovery point picture of the first GRA picture is determined to be valid until an intra random access point (IRAP) picture is decoded.

6. The method according to claim 1 or 4, wherein: The recovery point picture of the first GRA picture is specified by a first RpPicOrderCntVal variable, wherein the recovery point picture of the second GRA picture is specified by a second RpPicOrderCntVal variable.

7. The method according to claim 6, wherein: Replacing the recovery point picture of the first GRA picture with the recovery point picture of the second GRA picture includes: replacing the value of the first RpPicOrderCntVal variable with the value of the second RpPicOrderCntVal variable.

8. A method for encoding video data, the method comprising: selecting, for a first progressive random access (GRA) picture in a current sequence of pictures and at or after the first GRA picture in display order, a recovery point picture, and selecting, for a second GRA picture in the current sequence of pictures and at or after the second GRA picture in display order, a recovery point picture; as well as A first value specifying a recovery point picture for the first GRA picture in the pictures of the current sequence and a second value specifying a recovery point picture for the second GRA picture in the pictures of the current sequence are encoded in a decoded video bitstream and as an unsigned integer 0th order index Golomb decoding syntax element with a left bit first, wherein the first value and the second value are both in a range of zero to MaxPicOrderCntLsb-1, including zero and MaxPicOrderCntLsb-1, and wherein encoding the first value or the second value comprises encoding the syntax element according to a header syntax structure of the decoded video bitstream referenced by the first GRA picture or the second GRA picture.

9. The method according to claim 8, wherein: The syntax element is the recovery_poc_cnt syntax element.

10. A device for decoding video data, the device comprising: a memory configured to store at least a portion of the decoded video bitstream; as well as One or more processors implemented in circuitry and configured to: decoding, according to the decoded video bitstream and as an unsigned integer 0th order index Golomb decoding syntax element with left bit first, a first value specifying a recovery point picture for a first progressive random access (GRA) picture in a current sequence and a second value specifying a recovery point picture for a second GRA picture in the current sequence, wherein the recovery point picture of the first GRA picture is located at or after the first GRA picture in display order, and the recovery point picture of the second GRA picture is located at or after the second GRA picture in display order, wherein the first value and the second value are both in a range of zero to MaxPicOrderCntLsb-1, inclusive, and wherein decoding the first value or the second value comprises: decoding the syntax element according to a header syntax structure of the decoded video bitstream referenced by the first GRA picture or the second GRA picture; Determine that the second GRA picture is located between the first GRA picture and a restoration point picture of the first GRA picture; In response to determining that the second GRA picture is located between the first GRA picture and the restoration point picture of the first GRA picture, replacing the restoration point picture of the first GRA picture with the restoration point picture of the second GRA picture; and The decoding of the pictures of the current sequence is resumed at a recovery point picture of the second GRA picture.

11. The device according to claim 10, further comprising: determining a picture order count (POC) value of a recovery point picture of the first GRA picture based on the first value specifying the recovery point picture of the first GRA picture and a POC value of the first GRA picture; as well as A POC value of a restoration point picture of the second GRA picture is determined based on the second value specifying the restoration point picture of the second GRA picture and the POC value of the second GRA picture.

12. The device according to claim 10, wherein: The syntax element is the recovery_poc_cnt syntax element.

13. The device of claim 10, further comprising a display, the one or more processors being further configured to output the decoded picture from the current sequence of pictures for display at the display.

14. The apparatus according to claim 10, further comprising: It is determined that the recovery point picture of the first GRA picture is valid until the second GRA picture or the recovery point picture of the second GRA picture is decoded.

15. The device according to claim 10 or 14, further comprising: A recovery point picture of the first GRA picture is determined to be valid until an intra random access point (IRAP) picture is decoded.

16. The apparatus according to claim 10 or 14, wherein: The recovery point picture of the first GRA picture is specified by a first RpPicOrderCntVal variable, wherein the recovery point picture of the second GRA picture is specified by a second RpPicOrderCntVal variable.

17. The device according to claim 16, wherein: Replacing the recovery point picture of the first GRA picture with the recovery point picture of the second GRA picture includes: replacing the value of the first RpPicOrderCntVal variable with the value of the second RpPicOrderCntVal variable.

18. A device for encoding video data, the device comprising: a memory configured to store at least a portion of the decoded video bitstream; as well as One or more processors implemented in circuitry and configured to: selecting, for a first progressive random access (GRA) picture in a current sequence of pictures and at or after the first GRA picture in display order, a recovery point picture, and selecting, for a second GRA picture in the current sequence of pictures and at or after the second GRA picture in display order, a recovery point picture; and A first value specifying a recovery point picture for the first GRA picture in pictures of the current sequence and a second value specifying a recovery point picture for the second GRA picture in pictures of the current sequence are encoded in the decoded video bitstream and as an unsigned integer 0th order index Golomb decoding syntax element with a left bit first, wherein the first value and the second value are both in a range of zero to MaxPicOrderCntLsb-1, including zero and MaxPicOrderCntLsb-1, and wherein encoding the first value or the second value comprises encoding the syntax element according to a header syntax structure of the decoded video bitstream referenced by the first GRA picture or the second GRA picture.

19. A computer-readable storage medium storing instructions that, when executed by one or more processors of a video decoder, cause the one or more processors to: A first value specifying a recovery point picture for a first progressive random access (GRA) picture in a current sequence of pictures and a second value specifying a recovery point picture for a second GRA picture in the current sequence of pictures are decoded from the decoded video bitstream and as an unsigned integer 0th order index Golomb coding syntax element with left bit first, wherein The recovery point picture of the first GRA picture is located at or after the first GRA picture in display order, and the recovery point picture of the second GRA picture is located at or after the second GRA picture in display order, wherein the first value and the second value are both in the range of zero to MaxPicOrderCntLsb-1, including zero and MaxPicOrderCntLsb-1, and wherein decoding the first value or the second value comprises: decoding the syntax element according to a header syntax structure of the decoded video bitstream referenced by the first GRA picture or the second GRA picture; Determine that the second GRA picture is located between the first GRA picture and a restoration point picture of the first GRA picture; In response to determining that the second GRA picture is located between the first GRA picture and the restoration point picture of the first GRA picture, replacing the restoration point picture of the first GRA picture with the restoration point picture of the second GRA picture; and The decoding of the pictures of the current sequence is resumed at a recovery point picture of the second GRA picture.

20. The computer-readable storage medium of claim 19, further comprising instructions for causing the one or more processors to: determining a picture order count (POC) value of a recovery point picture of the first GRA picture based on the first value specifying the recovery point picture of the first GRA picture and a POC value of the first GRA picture; and A POC value of a restoration point picture of the second GRA picture is determined based on the second value specifying the restoration point picture of the second GRA picture and the POC value of the second GRA picture.

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