Shared Decoder Picture Buffer for Multiple Layers

Abstract

A video decoder for decoding multi-layer video data may be configured to: maintain a decoded picture buffer (DPB) for storing reference pictures for a plurality of layers; perform a picture output and removal process on the DPB before decoding a current picture of an access unit of a first layer, wherein the plurality of layers comprises at least a first layer and a second layer; and perform a picture bumping process across all layers of the DPB after removing the last decoded unit of the current picture from a coded picture buffer (CPB), wherein one or more processors are further configured to remove only decoded pictures belonging to the first layer from the DPB, to perform the picture output and removal process on the DPB.

Description

[Technical field]

[0001]

[0001] This application claims priority to U.S. Application No. 17 / 128,767, filed December 21, 2020, which claims the benefit of U.S. Provisional Application No. 62 / 953,394, filed December 24, 2019, the entire contents of each of which are incorporated herein by reference.

[0002] This disclosure relates to video encoding and decoding. [Background technology]

[0003] Digital video capabilities may be incorporated into a wide range of devices, including digital televisions, digital direct 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 gaming devices, video game consoles, cellular or satellite radio telephones, so-called "smartphones," video teleconferencing devices, video streaming devices, and the like. Digital video devices implement video coding techniques, such as those described in 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 to such standards. By implementing such video coding techniques, video devices may more efficiently transmit, receive, encode, decode, and / or store digital video information.

[0004]

[0004] Video coding techniques include spatial (intra-picture) prediction and / or temporal (inter-picture) prediction to reduce or remove redundancy inherent in video sequences. In 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 with respect 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 with respect to reference samples in neighboring blocks in the same picture or temporal prediction with respect to reference samples in other reference pictures. A picture may be referred to as a frame, and a reference picture may be referred to as a reference frame. Summary of the Invention

[0005]

[0005] This disclosure describes techniques for maintaining a decoded picture buffer for decoding multi-layer video data. As part of maintaining the DPB, a video decoder may need to periodically remove pictures from the DPB to make room for new pictures to be added to the DPB. When decoding multi-layer video data, some existing video decoders maintain sub-DPBs, where each sub-DPB includes a picture storage buffer for storage of decoded pictures of one layer. In contrast, when decoding multi-layer video data, some existing video decoders maintain a common DPB for all layers, which reduces complexity but potentially brings other problems. For example, if the bumping process is only invoked for pictures that belong to the same layer as the picture being coded, in some coding scenarios where the buffer does not contain any pictures of that layer, the bumping process may not properly create a place in the DPB for the new picture. The techniques of this disclosure, including performing a picture output and removal process on the DPB by removing only decoded pictures belonging to the first layer from the DPB, and performing a picture bumping process across all layers of the DPB after removing the last decoding unit of the current picture from the CPB, may advantageously enable a video decoder to utilize a common DPB for all layers while ensuring that needed reference pictures are not removed prematurely from the DPB and while ensuring that the DPB does not become overly full.

[0006]

[0006] According to one example of the present disclosure, a device for decoding video data includes a memory configured to store the video data and one or more processors implemented in a circuit, wherein the one or more processors are configured to maintain a decoded picture buffer (DPB) for storing reference pictures for a plurality of layers, wherein the plurality of layers comprises at least a first layer and a second layer, and to perform a picture output and removal process on the DPB prior to decoding a current picture of an access unit of a first layer, wherein the plurality of layers comprises at least a first layer and a second layer, and wherein to perform the picture output and removal process on the DPB, the one or more processors perform a picture bumping process across all layers of the DPB after removing a last decoded unit of the current picture from a coded picture buffer (CPB), which is further configured to remove only decoded pictures belonging to the first layer from the DPB.

[0007]

[0007] According to another example of the present disclosure, a method includes maintaining a decoded picture buffer (DPB) for storing reference pictures for multiple layers, wherein the multiple layers comprise at least a first layer and a second layer, performing a picture output and removal process on the DPB prior to decoding a current picture of an access unit of a first layer, wherein performing the picture output and removal process on the DPB comprises removing only decoded pictures belonging to the first layer from the DPB, and performing a picture bumping process across all layers of the DPB after removing a last decoded unit of the current picture from a coded picture buffer (CPB), wherein performing the picture output and removal process on the DPB comprises removing only decoded pictures from the DPB that belong to the first layer.

[0008]

[0008] According to another example of the present disclosure, a computer-readable storage medium stores instructions that, when executed by one or more processors, cause the one or more processors to maintain a decoded picture buffer (DPB) for storing reference pictures for multiple layers, wherein the multiple layers comprise at least a first layer and a second layer, prior to decoding a current picture of an access unit of a first layer, wherein the multiple layers comprise at least a first layer and a second layer, and wherein, to perform the picture output and removal process on the DPB, the one or more processors perform a picture bumping process across all layers of the DPB after removing a last decoded unit of the current picture from a coded picture buffer (CPB), further configured to remove only decoded pictures belonging to the first layer from the DPB.

[0009]

[0009] According to another example of the present disclosure, an apparatus for decoding multi-layer video data includes means for maintaining a decoded picture buffer (DPB) for storing reference pictures for a plurality of layers, wherein the plurality of layers comprises at least a first layer and a second layer, means for performing a picture output and removal process on the DPB prior to decoding a current picture of an access unit of a first layer, and means for performing a picture bumping process across all layers of the DPB after removing a last decoded unit of the current picture from a coded picture buffer (CPB), wherein performing the picture output and removal process on the DPB comprises removing only decoded pictures belonging to the first layer from the DPB.

[0010]

[0010] The details of one or more examples are set forth in the accompanying drawings and the description below. Other features, objects, and advantages will become apparent from the description, drawings, and claims. [Brief description of the drawings]

[0011] [Figure 1]

[0011] A block diagram illustrating an example video encoding and decoding system in which the techniques of this disclosure may be implemented. [Figure 2A]

[0012] 1 is a conceptual diagram illustrating an exemplary Quad Tree Binary Tree (QTBT) structure. [Figure 2B] A conceptual diagram showing a corresponding coding tree unit (CTU). [Diagram 3]

[0013] 1 is a block diagram illustrating an example video encoder that may implement the techniques of this disclosure. [Figure 4]

[0014] 1 is a block diagram illustrating an example video decoder that may implement the techniques of this disclosure. [Diagram 5]

[0015] 1 is a flow chart illustrating a video encoding process. [Figure 6]

[0016] 1 is a flow chart illustrating a video decoding process. [Figure 7]

[0017] 1 is a flow chart illustrating a video decoding process. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012]

[0018] Video coding (e.g., video encoding and / or video decoding) generally involves either predicting a block of video data from already coded blocks of video data in the same picture (e.g., intra prediction) or predicting a block of video data from already coded blocks of video data in a different picture (e.g., inter prediction). In some instances, the video encoder also calculates residual data by comparing a prediction block to an original block. The residual data thus represents the difference between the prediction block and the original block. To reduce the number of bits required to signal the residual data, the video encoder transforms and quantizes the residual data and signals the transformed and quantized residual data in the encoded bitstream. The compression achieved by the transform and quantization process may be lossy, meaning that the transform and quantization process may introduce distortions into the decoded video data.

[0013]

[0019] A video decoder decodes the residual data and adds it to the predictive block to generate a reconstructed video block that matches the original video block more closely than the predictive block alone. Due to losses introduced by transforming and quantizing the residual data, the initial reconstructed block may have distortions or artifacts. One common type of artifacts or distortions is called blockiness, where boundaries of the blocks used to code the video data are visible.

[0014]

[0020] To further improve the quality of the decoded video, the video decoder may perform one or more filtering operations on the reconstructed video blocks. Examples of these filtering operations include deblocking filtering, sample adaptive offset (SAO) filtering, and adaptive loop filtering (ALF). Parameters for these filtering operations may either be determined by the video encoder and explicitly signaled in the encoded video bitstream, or may be implicitly determined by the video decoder without the parameters having to be explicitly signaled in the encoded video bitstream.

[0015]

[0021] A video encoder encodes video data as network abstraction layer (NAL) units, and a video decoder decodes video data as NAL units. A NAL unit generally refers to a syntax structure that includes an indication of the type of data to follow and bytes that contain that data in the form of a raw byte sequence payload (RBSP) interspersed with emulation prevention bytes as needed. NAL units can include both video coding layer (VCL) NAL units and non-VCL NAL units.

[0016]

[0022] A picture unit (PU) generally refers to a set of NAL units that are associated with each other according to a specified classification rule, are consecutive in decoding order, and contain exactly one coded picture. An access unit generally refers to a set of PUs that contain coded pictures that belong to different layers and are associated with the same time for output.

[0017]

[0023] To support spatial and temporal scalability, video data may be coded in multiple layers. A layer generally refers to a set of VCL NAL units and associated non-VCL NAL units that all have the same layer identification value (e.g., a nuh_layer_id value). When decoding multi-layer video data, a video decoder may decode and display all layers, or only a subset of the layers.

[0018]

[0024] A video decoder may maintain, e.g., store and update, a coded picture buffer (CPB). The CPB may be, e.g., a first-in, first-out buffer containing decoding units (DUs) in a specified decoding order. The video decoder may also maintain a decoded picture buffer (DPB). A DPB generally refers to a buffer or memory that holds decoded pictures for reference, output reordering, or a specified output delay. A DU may refer to one or more VCL NAL units and associated non-VCL NAL units in an access unit (AU). In some instances, a DU may also be an AU.

[0019]

[0025] As part of maintaining the DPB, the video decoder may need to periodically remove pictures from the DPB to make room for new pictures to be added to the DPB. When decoding multi-layer video data, some existing video decoders maintain sub-DPBs, where each sub-DPB includes a picture storage buffer for storage of decoded pictures of one layer. In contrast, when decoding multi-layer video data, some existing video decoders maintain a common DPB for all layers, which reduces complexity but potentially introduces other problems. For example, if the bumping process is only invoked for pictures that belong to the same layer as the picture being coded, in some coding scenarios where the buffer does not contain any pictures of that layer, the bumping process may not properly create a place in the DPB for the new picture. The techniques of this disclosure, including performing a picture output and removal process on the DPB by removing only decoded pictures belonging to the first layer from the DPB, and performing a picture bumping process across all layers of the DPB after removing the last decoded unit of the current picture from the CPB, may advantageously enable a video decoder to utilize a common DPB for all layers while ensuring that needed reference pictures are not removed from the DPB prematurely and while ensuring that the DPB does not become overly full.

[0020]

[0026] Some techniques described in this disclosure may be described with respect to video decoding. However, it should be understood that, unless specified to the contrary, these techniques may also be implemented by a video encoder. For example, a video encoder generally performs video decoding (also referred to as reconstruction) as part of a process of determining how to encode video data. For example, as part of determining how to encode a block of video data, the video encoder may be configured to implement the same DPB update process as the video decoder, such that the video encoder and video decoder maintain the same DPB.

[0021]

[0027] 1 is a block diagram illustrating an example video encoding and decoding system 100 that may implement the techniques of this disclosure. The techniques of this disclosure are generally directed to coding (encoding and / or decoding) video data. Generally, video data includes any data for processing video. Thus, video data may include raw uncoded video, coded video, decoded (e.g., reconstructed) video, and video metadata, such as signaling data.

[0022]

[0028] 1, system 100 includes a source device 102 that provides encoded video data to be decoded and displayed by a destination device 116, in this example. In particular, source device 102 provides the video data to destination device 116 via a computer-readable medium 110. Source device 102 and destination device 116 may comprise any of a wide range of devices, including desktop computers, notebook (i.e., laptop) computers, mobile devices, tablet computers, set-top boxes, telephone handsets such as smartphones, televisions, cameras, display devices, digital media players, video gaming consoles, video streaming devices, broadcast receiver devices, and the like. In some cases, source device 102 and destination device 116 may be equipped for wireless communication and thus may be referred to as wireless communication devices.

[0023]

[0029] In the example of FIG. 1, source device 102 includes a video source 104, memory 106, video encoder 200, and output interface 108. Destination device 116 includes an input interface 122, a video decoder 300, memory 120, and a display device 118. According to this disclosure, the video encoder 200 of source device 102 and the video decoder 300 of destination device 116 may be configured to apply techniques for a shared decoded picture buffer for multiple layers. Thus, 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, the source and destination devices 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 interface with an external display device rather than including an integrated display device.

[0024]

[0030] The system 100 shown in FIG. 1 is only an example. In general, any digital video encoding and / or decoding device may implement the technique for a shared decoded picture buffer for multiple layers. The source device 102 and the destination device 116 are only examples of coding devices, such that the source device 102 generates coded video data for transmission to the destination device 116. In this disclosure, we refer to a "coding" device as a device that performs coding (encoding and / or decoding) of data. Thus, the video encoder 200 and the video decoder 300 represent examples of coding devices, specifically, video encoders and video decoders, respectively. In some examples, the source device 102 and the destination device 116 may operate substantially symmetrically, such that each of the source device 102 and the destination device 116 includes video encoding and video decoding components. Thus, the system 100 may support one-way or two-way video transmission between the source device 102 and the destination device 116, for example, video streaming, video playback, video broadcasting, or video telephony.

[0025]

[0031] Generally, video source 104 represents a source of video data (i.e., raw, unencoded video data) and provides a continuous series of pictures (also called “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 video camera, a video archive containing previously captured raw video, and / or a video feed interface for receiving video from a video content provider. As a further alternative, video source 104 may generate computer graphics-based data or a combination of live, archival, and computer-generated video as the source video. In each case, video encoder 200 encodes the captured, pre-captured, or computer-generated video data. Video encoder 200 may reorder the pictures from a received order (sometimes called a “display order”) into a coding order for coding. Video encoder 200 may generate a bitstream including the encoded video data. The source device 102 may then output the encoded video data via the output interface 108 onto a computer-readable medium 110, for receipt and / or retrieval by, for example, an input interface 122 of the destination device 116.

[0026]

[0032] The memory 106 of the source device 102 and the memory 120 of the destination device 116 represent general purpose memories. In some examples, the memories 106, 120 may store raw video data, e.g., raw video from the video source 104 and raw decoded video data from the video decoder 300. Additionally or alternatively, the memories 106, 120 may store software instructions executable by, e.g., the video encoder 200 and the video decoder 300, respectively. Although the memories 106 and 120 are shown in this example as separate from the video encoder 200 and the video decoder 300, it should be understood that the video encoder 200 and the video decoder 300 may also include internal memories for functionally similar or equivalent purposes. Additionally, the memories 106, 120 may store encoded video data, e.g., the output from the video encoder 200 and the input to the video decoder 300. In some examples, portions of the memory 106, 120 may be allocated as one or more video buffers, for example, to store raw decoded and / or encoded video data.

[0027]

[0033] The computer-readable medium 110 may represent any type of medium or device capable of transporting 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 for enabling the source device 102 to transmit encoded video data directly to the destination device 116 in real time, for example, via a radio frequency network or a computer-based network. In accordance with a communication standard, such as a wireless communication protocol, the output interface 108 may modulate a transmission signal including the encoded video data, and the input interface 122 may demodulate a received transmission signal. The communication medium may comprise any wireless or wired communication medium, such as a radio frequency (RF) spectrum or one or more physical transmission lines. The communication medium may form part 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 routers, switches, base stations, or any other equipment that may be useful to facilitate communication from the source device 102 to the destination device 116.

[0028]

[0034] In some examples, source device 102 may output encoded data from output interface 108 to storage device 112. Similarly, destination device 116 may access 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.

[0029]

[0035] In some examples, source device 102 may output the encoded video data to a file server 114 or another intermediate storage device, which may store the encoded video data generated by source device 102. Destination device 116 may access the stored video data from file server 114 via streaming or download.

[0030]

[0036] The file server 114 may be any type of server device capable of storing encoded video data and transmitting the encoded video data to the destination device 116. The file server 114 may represent a web server (e.g., for a website), a server configured to provide file transfer protocol services (such as File Transfer Protocol (FTP) or File Delivery over Unidirectional Transport (FLUTE) protocol), a content delivery network (CDN) device, a HyperText Transfer Protocol (HTTP) server, a Multimedia Broadcast Multicast Service (MBMS) or enhanced MBMS (eMBMS) server, and / or a network attached storage (NAS) device. The file server 114 may additionally or alternatively implement one or more HTTP streaming protocols, such as Dynamic Adaptive Streaming over HTTP (DASH), HTTP Live Streaming (HLS), Real Time Streaming Protocol (RTSP), HTTP Dynamic Streaming, etc.

[0031]

[0037] Destination device 116 may access the encoded video data from file server 114 through 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 both, that is suitable for accessing the encoded video data stored on file server 114. Input interface 122 may be configured to operate according to any one or more of the various protocols described above for retrieving or receiving media data from file server 114, or other such protocols for retrieving media data.

[0032]

[0038] The output interface 108 and the input interface 122 may represent a wireless transmitter / receiver, a modem, a wired networking component (e.g., an Ethernet card), a wireless communication component operating according to any of the various IEEE 802.11 standards, or other physical components. In examples in which the output interface 108 and the input interface 122 comprise wireless components, the output interface 108 and the input interface 122 may be configured to transfer data, such as encoded video data, according to a cellular communication standard, such as 4G, 4G-LTE (Long Term Evolution), LTE Advanced, 5G, etc. In some examples in which the output interface 108 comprises a wireless transmitter, the output interface 108 and the input interface 122 may be configured to transfer data, such as encoded video data, according to other wireless standards, such as the IEEE 802.11 specification, the IEEE 802.15 specification (e.g., ZigBee), the Bluetooth standard, etc. In some examples, the source device 102 and / or the destination device 116 may include respective system-on-chip (SoC) devices. For example, the source device 102 may include a SoC device for performing functions attributable to the video encoder 200 and / or the output interface 108, and the destination device 116 may include a SoC device for performing functions attributable to the video decoder 300 and / or the input interface 122.

[0033]

[0039] The techniques of this disclosure may be applied to video coding supporting any of a variety of multimedia applications, such as over-the-air television broadcast, cable television transmission, satellite television transmission, Internet streaming video transmission such as Dynamic Adaptive Streaming over HTTP (DASH), digital video encoded on a data storage medium, decoding of digital video stored on a data storage medium, or other applications.

[0034]

[0040] An input interface 122 of the destination device 116 receives an encoded video bitstream from a computer-readable medium 110 (e.g., a communication medium, a storage device 112, a file server 114, etc.). The encoded video bitstream may include signaling information defined by the video encoder 200 that is also used by the video decoder 300, such as syntax elements having values ​​that describe characteristics and / or processing of video blocks or other coded units (e.g., slices, pictures, groups of pictures, sequences, etc.). The display device 118 displays decoded pictures of the decoded video data to a user. The display device 118 may represent any of a variety of display devices, such as a liquid crystal display (LCD), a plasma display, an organic light emitting diode (OLED) display, or another type of display device.

[0035]

[0041] 1, in some examples, the video encoder 200 and the video decoder 300 may each be integrated with an audio encoder and / or an audio decoder and may include an appropriate MUX-DEMUX unit, or other hardware and / or software, to handle multiplexed streams that include both audio and video in a common data stream. Where applicable, the MUX-DEMUX unit may conform to the ITU H.223 multiplexer protocol or other protocols, such as the User Datagram Protocol (UDP).

[0036]

[0042] The video encoder 200 and the video decoder 300 may each be implemented as any of a variety of suitable encoder and / or decoder circuits, or any combination thereof, 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, etc. When the techniques are implemented partially in software, a device may store instructions for the software on a suitable non-transitory computer-readable medium and execute the instructions in hardware using one or more processors to implement the techniques of this disclosure. Each of the video encoder 200 and the video decoder 300 may be included in one or more encoders or decoders, any of which may be integrated as part of a combined encoder / decoder (CODEC) in the respective device. A device including the video encoder 200 and / or the video decoder 300 may comprise an integrated circuit, a microprocessor, and / or a wireless communication device such as a cellular phone.

[0037]

[0043] Video encoder 200 and video decoder 300 may operate according to a video coding standard, such as ITU-T H.265, also known as High Efficiency Video Coding (HEVC), or extensions thereof, such as multiview and / or scalable video coding extensions. Alternatively, video encoder 200 and video decoder 300 may operate according to other proprietary or industry standards, such as ITU-T H.266, also known as Joint Exploration Test Model (JEM), or Versatile Video Coding (VVC). A recent draft of the VVC standard is set forth in Bross et al., "Versatile Video Coding (Draft 7)," Joint Video Experts Team (JVET) of ITU-T SG16 WP3 and ISO / IEC JTC1 / SC29 / WG11, 16th Meeting, Geneva, Switzerland, October 1-11, 2019, JVET-P2001-v14 (hereinafter, "VVC Draft 7"). However, the techniques of this disclosure are not limited to any particular coding standard.

[0038]

[0044] Generally, the video encoder 200 and the video decoder 300 may perform block-based coding of pictures. The term “block” generally refers to a structure that includes data to be processed (e.g., encoded, decoded, or otherwise used in an encoding and / or decoding process). For example, a block may include a two-dimensional matrix of samples of luminance and / or chrominance data. Generally, the video encoder 200 and the video decoder 300 may code video data represented in a YUV (e.g., Y, Cb, Cr) format. That is, rather than coding red, green, and blue (RGB) data for a sample of a picture, the video encoder 200 and the video decoder 300 may code a luminance component and a chrominance component, where the chrominance component may include both red and blue hues of chrominance components. In some examples, the video encoder 200 converts received RGB format data to a YUV representation prior to encoding, and the video decoder 300 converts the YUV representation to an RGB format. Alternatively, pre-processing and post-processing units (not shown) may perform these conversions.

[0039]

[0045] This disclosure may generally refer to coding (e.g., encoding and decoding) a picture to include processes of encoding or decoding data for a picture. Similarly, this disclosure may refer to coding a block of a picture to include processes of encoding or decoding data for the block, e.g., predictive and / or residual coding. A coded video bitstream generally includes a series of values ​​for syntax elements that represent coding decisions (e.g., coding modes) and partitioning of a picture into blocks. Thus, references to coding a picture or a block should be understood generally as coding values ​​for the syntax elements that form the picture or block.

[0040]

[0046] HEVC defines various blocks, including coding units (CUs), prediction units (PUs), and transform units (TUs). According to HEVC, a video coder (such as video encoder 200) partitions coding tree units (CTUs) into CUs according to a quadtree structure. That is, the video coder partitions CTUs and CUs into four equal non-overlapping squares, and each node of the quadtree has either zero or four child nodes. A node without children may be called a "leaf node", and a CU of such a leaf node may include one or more PUs and / or one or more TUs. A video coder may further partition PUs and TUs. For example, in HEVC, a residual quadtree (RQT) represents the partition of TUs. In HEVC, a PU represents inter-predicted data, while a TU represents residual data. An intra-predicted CU includes intra-prediction information, such as an intra-mode indication.

[0041]

[0047] As another example, the video encoder 200 and the video decoder 300 may be configured to operate according to VVC. According to VVC, a video coder (such as the video encoder 200) partitions a picture into multiple coding tree units (CTUs). The video encoder 200 may partition the CTUs according to a tree structure, such as a quad-tree binary tree (QTBT) structure or a multi-type tree (MTT) structure. The QTBT structure eliminates the concept of multiple partition types, such as the separation between CUs, PUs, and TUs in HEVC. The QTBT structure includes two levels, a first level partitioned according to a quad-tree partition and a second level partitioned according to a binary tree partition. The root node of the QTBT structure corresponds to a CTU. The leaf nodes of the binary tree correspond to coding units (CUs).

[0042]

[0048] In the MTT partitioning structure, blocks may be partitioned using quad tree (QT) partitioning, binary tree (BT) partitioning, and one or more types of triple tree (TT) (also called ternary tree (TT)) partitioning. A triple tree or ternary tree partitioning is a partitioning in which a block is split into three sub-blocks. In some examples, a triple tree or ternary tree partitioning splits a block into three sub-blocks without splitting the original block through the center. The partitioning types in MTT (e.g., QT, BT, and TT) may be symmetric or asymmetric.

[0043]

[0049] 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 luminance and chrominance components, and 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 luminance component and another QTBT / MTT structure for both chrominance components (or two QTBT / MTT structures for each chrominance component).

[0044]

[0050] Video encoder 200 and video decoder 300 may be configured to use quadtree partitioning, QTBT partitioning, MTT partitioning, or other partition structures in accordance with HEVC. For purposes of illustration, the description of the techniques of this disclosure is presented with respect to QTBT partitioning. However, it should be understood that the techniques of this disclosure may also be applied to video coders configured to use quadtree partitioning, or other types of partitioning as well.

[0045]

[0051] In some examples, the CTU includes a coding tree block (CTB) of luma samples, two corresponding CTBs of chroma samples for a picture with three sample arrays, or a CTB of samples for a monochrome picture, or a picture coded using three separate color planes and syntax structures used to code the samples. The CTB may be an N×N block of samples for some value of N such that the division of the components into the CTB is partitioned. The components are arrays or single samples from one of the three arrays (luma and two chromas) that configure the picture in 4:2:0, 4:2:2, or 4:4:4 color format, or an array or single sample of an array that configures the picture in monochrome format. In some examples, the coding block is an M×N block of samples for some value of M and N such that the division of the CTB into coding blocks is partitioned.

[0046]

[0052] Blocks (e.g., CTUs or CUs) may be grouped in various ways in a picture. As an example, a brick may refer to a rectangular region of a CTU row in a particular tile in a picture. A tile may be a rectangular region of a CTU in a particular tile column and a particular tile row in a picture. A tile column refers to a rectangular region of a CTU having a height equal to the height of the picture and a width specified by a syntax element (e.g., in a picture parameter set). A tile row refers to a rectangular region of a CTU having a height specified by a syntax element (e.g., in a picture parameter set) and a width equal to the width of the picture.

[0047]

[0053] In some examples, a tile may be partitioned into multiple bricks, each of which may include one or more CTU rows within the tile. A tile 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 tile may not be referred to as a tile.

[0048]

[0054] The bricks in a picture may also be arranged into slices. A slice may be an integer number of bricks of a picture that may be contained entirely in a single Network Abstraction Layer (NAL) unit. In some examples, a slice includes either several complete tiles or only a continuous sequence of complete bricks of one tile.

[0049]

[0055] This disclosure may use "NxN" and "N by N", e.g., 16x16 samples or 16 by 16 samples, interchangeably to refer to sample dimensions of a block (such as a CU or other video block) in terms of vertical and horizontal dimensions. Generally, a 16x16 CU has 16 samples in the vertical direction (y=16) and 16 samples in the horizontal direction (x=16). Similarly, an NxN CU generally has N samples in the vertical direction and N samples in the horizontal direction, where N represents a non-negative integer value. Samples in a CU may be arranged in rows and columns. Moreover, a CU does not necessarily have to have the same number of samples in the horizontal direction as in the vertical direction. For example, a CU may comprise NxM samples, where M is not necessarily equal to N.

[0050]

[0056] The video encoder 200 encodes video data for a CU that represents prediction and / or residual information, as well as other information. The prediction information indicates how the CU should be predicted to form a predictive block for the CU. The residual information generally represents sample-by-sample differences between samples of the CU prior to encoding and the predictive block.

[0051]

[0057] To predict a CU, the video encoder 200 may generally form a predictive block for the CU through inter-prediction or intra-prediction. Inter-prediction generally refers to predicting a CU from data of a previously coded picture, while intra-prediction generally refers to predicting a CU from previously coded data of the same picture. To perform inter-prediction, the video encoder 200 may generate a predictive block using one or more motion vectors. The video encoder 200 may generally perform a motion search to identify a reference block that closely matches the CU, for example, with respect to the difference between the CU and the reference block. The video encoder 200 may calculate a difference metric using a sum of absolute differences (SAD), sum of squared differences (SSD), mean absolute difference (MAD), mean squared difference (MSD), or other such difference calculation to determine whether the reference block closely matches the current CU. In some examples, the video encoder 200 may predict the current CU using unidirectional or bidirectional prediction.

[0052]

[0058] Some examples of VVC also provide an affine motion compensation mode, which may be considered an inter-prediction mode. In an affine motion compensation mode, video encoder 200 may determine two or more motion vectors that represent non-translational motion, such as zooming in or out, rotation, perspective motion, or other irregular motion types.

[0053]

[0059] To perform intra prediction, the video encoder 200 may select an intra prediction mode to generate a predictive block. Some examples of VVC provide 67 intra prediction modes, including various directional modes, as well as planar and DC modes. In general, the video encoder 200 selects an intra prediction mode that describes neighboring samples relative to a current block (e.g., a block of a CU) from which samples of the current block should be predicted. Such samples may generally be above, to the left of, or to the left of the current block in the same picture as the current block, assuming that the video encoder 200 codes the CTUs and CUs in raster scan order (left to right, top to bottom).

[0054]

[0060] Video encoder 200 encodes data representing a prediction mode for the current block. For example, in an inter prediction mode, video encoder 200 may encode data representing which of various available inter prediction modes is used, as well as motion information for the corresponding mode. For example, in unidirectional or bidirectional inter prediction, video encoder 200 may encode motion vectors using advanced motion vector prediction (AMVP) or merge mode. Video encoder 200 may use similar modes to encode motion vectors for affine motion compensation modes.

[0055]

[0061] Following prediction, such as intra- 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 sample-by-sample differences between the block and a predictive block for the block formed using a corresponding prediction mode. The video encoder 200 may apply one or more transforms to the residual block to generate transform data in a transform domain rather than the 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. Additionally, the video encoder 200 may apply a secondary transform, such as a mode-dependent non-separable secondary transform (MDNSST), a signal-dependent transform, a Karhunen-Loeve transform (KLT), etc., following the first transform. The video encoder 200 generates transform coefficients following application of the one or more transforms.

[0056]

[0062] As mentioned above, following any transformation to generate 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 possibly reduce the amount of data used to represent the transform coefficients, providing further compression. By performing a quantization process, the video encoder 200 may reduce the bit depth associated with some or all of the transform coefficients. For example, the video encoder 200 may round 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.

[0057]

[0063] Following quantization, the video encoder 200 may scan the transform coefficients to generate a one-dimensional vector from a two-dimensional matrix including the quantized transform coefficients. The scan may be designed to place higher energy (and therefore lower frequency) transform coefficients at the front of the vector and lower energy (and therefore higher frequency) transform coefficients at the rear of the vector. In some examples, the video encoder 200 may utilize a predefined scan order to scan the quantized transform coefficients to generate a serialized vector and then entropy encode the quantized transform coefficients of the vector. In other examples, the video encoder 200 may perform an adaptive scan. After scanning the quantized transform coefficients to form a one-dimensional vector, the video encoder 200 may entropy encode the one-dimensional vector, e.g., according to context-adaptive binary arithmetic coding (CABAC). The video encoder 200 may also entropy encode values ​​for syntax elements describing metadata associated with the encoded video data for use by the video decoder 300 in decoding the video data.

[0058]

[0064] To implement CABAC, the video encoder 200 may assign a context in a context model to a symbol to be transmitted. The context may relate, for example, to whether neighboring values ​​of the symbol are zero-valued or not. The probability determination may be based on the context assigned to the symbol.

[0059]

[0065] Video encoder 200 may further generate syntax data, such as block-based syntax data, picture-based syntax data, and sequence-based syntax data, for video decoder 300, e.g., in a picture header, block header, slice header, or other syntax data, such as a sequence parameter set (SPS), picture parameter set (PPS), or video parameter set (VPS). Video decoder 300 may similarly decode such syntax data to determine how to decode corresponding video data.

[0060]

[0066] In this manner, video encoder 200 may generate a bitstream including encoded video data, e.g., syntax elements that describe partitions of a picture into blocks (e.g., CUs) as well as predictive and / or residual information for the blocks. Finally, video decoder 300 may receive the bitstream and decode the encoded video data.

[0061]

[0067] In general, the video decoder 300 performs an inverse process to that performed by the video encoder 200 to decode the encoded video data of the bitstream. For example, the video decoder 300 may decode values ​​for syntax elements of the bitstream using CABAC in a manner that is inverse to, but substantially similar to, the CABAC encoding process of the video encoder 200. The syntax elements may define partition information for partitioning a picture into CTUs and partitions of each CTU according to a corresponding partition structure, such as a QTBT structure, to define CUs of the CTU. The syntax elements may further define prediction and residual information for blocks (e.g., CUs) of video data.

[0062]

[0068] The residual information may be represented, for example, by quantized transform coefficients. The video decoder 300 may dequantize and inverse transform the quantized transform coefficients of the block to reconstruct a residual block for the block. The video decoder 300 uses the signaled prediction mode (intra- or inter-prediction) and associated prediction information (e.g., motion information for inter-prediction) to form a predictive block for the block. The video decoder 300 may then combine (sample-by-sample) the predictive block and the residual block to reconstruct the original block. The video decoder 300 may perform additional processing, such as performing a deblocking process to reduce visual artifacts along block boundaries.

[0063]

[0069] This disclosure may generally refer to "signaling" certain information, such as a syntax element. The term "signaling" may generally refer to communication of values ​​for syntax elements and / or other data used to decode encoded video data. That is, video encoder 200 may signal values ​​for syntax elements in a bitstream. Generally, signaling refers to generating values ​​in a bitstream. As mentioned above, source device 102 may transport the bitstream to destination device 116 in substantially real-time or may transport the bitstream to destination device 116 in non-real-time, such as may be done when storing syntax elements to storage device 112 for later retrieval by destination device 116.

[0064]

[0070] 2A and 2B are conceptual diagrams illustrating an exemplary quad-tree binary tree (QTBT) structure 130 and corresponding coding tree unit (CTU) 132. Solid lines represent quad-tree splitting, and dotted lines indicate binary tree splitting. At each split (i.e., non-leaf) node of the binary tree, one flag is signaled to indicate which splitting type (i.e., horizontal or vertical) is used, where in this example, 0 indicates horizontal splitting and 1 indicates vertical splitting. In quad-tree splitting, there is no need to indicate the splitting type, since the quad-tree node splits the block horizontally and vertically into four sub-blocks with equal size. Thus, video encoder 200 may encode, and video decoder 300 may decode, syntax elements (such as splitting information) for the region tree level (i.e., solid lines) of QTBT structure 130 and syntax elements (such as splitting information) for the prediction tree level (i.e., dashed lines) of QTBT structure 130. Video encoder 200 may encode, and video decoder 300 may decode, video data, such as prediction and transform data, for CUs represented by terminal leaf nodes of QTBT structure 130.

[0065]

[0071] 2B may be associated with parameters that define the sizes of blocks corresponding to nodes of the QTBT structure 130 at the first and second levels. These parameters may include a CTU size (representing the size of the CTU 132 in a sample), a minimum quad tree size (MinQTSize representing the minimum allowable quad tree leaf node size), a maximum binary tree size (MaxBTSize representing the maximum allowable binary tree root node size), a maximum binary tree depth (MaxBTDepth representing the maximum allowable binary tree depth), and a minimum binary tree size (MinBTSize representing the minimum allowable binary tree leaf node size).

[0066]

[0072] 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 partitioned according to a quadtree partition. That is, the nodes at the first level are either leaf nodes (without child nodes) or have four child nodes. The example QTBT structure 130 represents such a node including a parent node and a child node with solid lines for branching. If the nodes at the first level are not larger than the maximum allowed binary tree root node size (MaxBTSize), the nodes may be further partitioned by their respective binary trees. The binary tree splitting of one node may be repeated until the nodes resulting from the split reach the minimum allowed binary tree leaf node size (MinBTSize) or the maximum allowed binary tree depth (MaxBTDepth). The example QTBT structure 130 represents such a node with dashed lines for branching. The binary tree leaf nodes are called coding units (CUs), and the CUs are used for prediction (e.g., intra-picture or inter-picture prediction) and transformation without further partitioning. As explained above, a CU may also be referred to as a "video block" or a "block."

[0067]

[0073] In one example of a QTBT partitioning structure, the CTU size is set as 128x128 (luma samples and two corresponding 64x64 chroma samples), MinQTSize is set as 16x16, MaxBTSize is set as 64x64, MinBTSize is set as 4 (for both width and height), and MaxBTDepth is set as 4. Quad tree partitioning is first applied to the CTU to generate a quad tree leaf node. The quad tree leaf node may have a size from 16x16 (i.e., MinQTSize) to 128x128 (i.e., CTU size). If the quad tree leaf node is 128x128, the leaf quad tree node is not further split by the binary tree since the size exceeds MaxBTSize (i.e., in this example, 64x64). Otherwise, the quad tree leaf node is further partitioned by the binary tree. Thus, the quad tree leaf node is also the root node for the binary tree and has the binary tree depth as 0. When the binary tree depth reaches MaxBTDepth (4 in this example), no further splitting is allowed. A binary tree node having a width equal to MinBTSize (4 in this example) implies that no further vertical splitting (i.e., width division) is allowed for that binary tree node. Similarly, a binary tree node having a height equal to MinBTSize implies that no further horizontal splitting (i.e., height division) is allowed for that binary tree node. As mentioned above, the leaf node of the binary tree is called a CU and is further processed according to the prediction and transformation without further partitioning.

[0068]

[0074] VVC Draft 7 supports multi-layer coding, where a DPB is common or shared across different layers. DPB operations are expressed in terms of sub-DPBs, where sub-DPBs are defined in Section C.3.1 of VVC Draft 7 as follows:

[0069] A DPB conceptually consists of sub-DPBs, each of which contains a picture storage buffer for storage of decoded pictures of one layer. Each of the picture storage buffers contains decoded pictures that are marked as "used for reference" or are retained for future output.

[0070]

[0075] There is a picture output process called independently for each layer. Section C.5.2.1 of VVC Draft 7 describes this process as follows:

[0071] The process for outputting and removing pictures from the DPB prior to the decoding of the current picture, specified in clause C.5.2.2, is invoked, followed by the invocation of the process for currently decoded picture marking and storage, specified in clause C.3.4, and finally the invocation of the process for additional bumping, specified in clause C.5.2.3. The "bumping" process is specified in clause C.5.2.4 and is invoked as specified in clauses C.5.2.2 and C.5.2.3.

[0072] These processes are applied independently for each layer, starting from the lowest layer in the OLS, in ascending order of the nuh_layer_id values ​​of the layers in the OLS. When these processes are applied for a particular layer, only the sub-DPBs for that particular layer are affected.

[0073]

[0076] The DPB parameters are signaled in the dpb_parameters() syntax structure, reproduced below.

[0074] [Table 1]

[0075]

[0077] VVC Draft 7 defines the syntax element "max_dec_pic_buffering_minus1[i]" as follows: max_dec_pic_buffering_minus1[i]+1 specifies the maximum required size of the DPB in units of picture storage buffers when Htid is equal to i, for each CLVS in the CVS. The value of max_dec_pic_buffering_minus1[i] shall be in the range of 0 to MaxDpbSize-1, inclusive, where MaxDpbSize is as specified in section A.4.2. When i is greater than 0, max_dec_pic_buffering_minus1[i] shall be greater than or equal to max_dec_pic_buffering_minus1[i-1]. When max_dec_pic_buffering_minus1[i] is not present due to subLayerInfoFlag equal to 0, for i in the range 0 to maxSubLayersMinus1-1, inclusive, it is inferred to be equal to max_dec_pic_buffering_minus1[maxSubLayersMinus1].

[0076]

[0078] VVC Draft 7 defines the syntax element "max_num_reorder_pics[i]" as follows: max_num_reorder_pics[i] specifies, for each CLVS of a CVS, the maximum allowable number of pictures of the CLVS that can precede any picture in the CLVS in decoding order and follow that picture in output order when Htid is equal to i. The value of max_num_reorder_pics[i] shall be in the range from 0 to max_dec_pic_buffering_minus1[i], inclusive. When i is greater than 0, max_num_reorder_pics[i] shall be greater than or equal to max_num_reorder_pics[i-1]. When max_num_reorder_pics[i] is not present due to subLayerInfoFlag equal to 0, for i in the range 0 to maxSubLayersMinus1-1, inclusive, it is inferred to be equal to max_num_reorder_pics[maxSubLayersMinus1].

[0077]

[0079] VVC Draft 7 defines the syntax element "max_latency_increase_plus1[i]" as follows: max_latency_increase_plus1[i] not equal to 0 is used to calculate a value of MaxLatencyPictures[i], which specifies, for each CLVS of a CVS, the maximum number of pictures in the CLVS that can precede any picture in the CLVS in output order and follow that picture in decoding order when Htid is equal to i.

[0078] When max_latency_increase_plus1[i] is not equal to 0, the value of MaxLatencyPictures[i] is specified as follows:

[0079]

number

[0080] When max_latency_increase_plus1[i] is equal to 0, the corresponding limit is not expressed.

[0081] The value of max_latency_increase_plus1[i] must be between 0 and 2, inclusive. 32 -2. For i in the range 0 to maxSubLayersMinus1-1, inclusive, due to subLayerInfoFlag equal to 0, when max_latency_increase_plus1[i] is not present, it is inferred to be equal to max_latency_increase_plus1[maxSubLayersMinus1].

[0082]

[0080] The DPB implementation of VVC Draft 7 may have some problems. As an example, in VVC Draft 7, DPB operations are expressed using sub-DPBs and sub-DPB fullness. However, VVC Draft 7 does not define sub-DPB fullness, and does not specify how sub-DPB fullness relates to the DPB fullness specified in the dpb_parameters() picture structure.

[0083]

[0081] Furthermore, the operations on the sub-DPBs, such as how the sub-DPB fullness should be checked, are not specified. Comparing a particular sub-DPB to the maximum DPB size (MaxDpbSize) may not be sufficient because there may be multiple sub-DPBs, and these sub-DPBs may exceed the specified DPB resources.

[0084] In VVC Draft 7 section C.5.2.1, output and removal of pictures from the DPB are called for each layer, where only the sub-DPB for the particular layer is affected. However, the DPB size is not defined for the sub-DPB, and thus it is unclear how the condition "the number of pictures in the DPB is greater than or equal to max_dec_pic_buffering_minus1[Htid]+1" should be checked for the sub-DPB.

[0085]

[0083] This disclosure has described techniques that may address the problems discussed above. The solutions provided in this disclosure may be used independently or in any combination.

[0086]

[0084] Parts of the description provided herein are described with respect to an example using a DPB size specified by the max_dec_pic_buffering_minus1 syntax element. However, the techniques of this disclosure may also be used with other parameters signaled in the dpb_paramters() syntax structure, such as max_num_reorder_pics and max_latency_increase_plus1. All these parameters are signaled for the entire DPB and not for the sub-DPBs, and therefore the sub-DPB condition checks currently utilized in VVC Draft 7 may be performed on the entire DPB using the signaled dpb_paramters() syntax element.

[0087]

[0085] The disclosed techniques described for a DPB may be applicable in other operations where sub-DPBs are used, such as for Coded Picture Buffer (CPB) or Hypothetical Reference Decoder (HRD) processing.

[0088]

[0086] As part of utilizing a shared decoder picture buffer for multiple layers, video encoder 200 and video decoder 300 may be configured to implement the following techniques.

[0089]

[0087] When sub-DPBs are used, DPB overall fullness is not initialized in VVC Draft 7. In some examples of this disclosure, video encoder 200 and video decoder 300 may be configured to initialize DPB fullness to 0 when the first picture of a video sequence is parsed. In one example, video encoder 200 and video decoder 300 may be configured to initialize DPB fullness to 0 when the first slice of CLVSS picture 0 with the lowest nuh_layer_id is parsed.

[0090]

[0088] The DPB picture marking process is applied to the current layer picture. However, the status of other nuh_layer_id pictures in the DPB is not specified in VVC Draft 7. In some examples of the present disclosure, the picture state or status refers to picture marking such as "used for short-term reference", "used for long-term reference", "used for inter-layer prediction", etc., and may alternatively or additionally include picture output status such as "used for output", "picture not needed for output", etc.

[0091] For some instances, it may be desirable to keep the state of other layer pictures as is, i.e. their state is kept in the DPB after the previous access unit decoding. In other words, the state of previous pictures of other nuh_layer_id is kept. In this case, if the other layer picture is a reference picture, it may not be removed by the "bumping" process.

[0092] In some examples, all pictures may be marked as being used for reference (e.g., used for short-term reference, used for long-term reference) when the first picture of the current access unit is decoded.

[0093] In some examples, in the "bumping" process (C.5.2.4), a picture is removed (emptied) only if it has a layer id equal to the current picture layer id. In this case, pictures of other layers may be output but not removed from the DPB even when they are not referenced; removal of such pictures will occur when the picture of that layer is decoded.

[0094]

[0089] In one example, DPB fullness may be defined as the sum of sub-DPB fullness, since MaxDpbSize is defined for each layer in the output layer set (OLS) and not for sub-DPBs. For example, MaxDpbSize may be specified by profile / level / tier as the maximum number of picture storage buffers. Furthermore, if sub-DPB sizes are defined or signaled, the sum of sub-DPB sizes shall not exceed MaxDpbSize. In one example, such a constraint may be expressed as follows:

[0095] It is a bitstream conformance requirement that the sum of max_dec_pic_buffering_minus1[i] for all layers included in an AU is within the range of 0 to MaxDpbSize-1, inclusive.

[0096]

[0090] In some examples, the constraints may be expressed as follows:

[0097] It is a bitstream conformance requirement that the sum of max_dec_pic_buffering_minus1[i] for all layers included in an OLS is within the range of 0 to MaxDpbSize-1, inclusive.

[0098]

[0091] In the output and remove picture process, instead of performing all operations for each layer independently, the video encoder 200 and the video decoder 300 may be configured to perform some operations per layer and some operations for the entire DPB across layers, even if the process is invoked per layer. For example, the video encoder 200 and the video decoder 300 may be configured to maintain a DPB for storing reference pictures for multiple layers, including at least a first layer and a second layer. Prior to decoding the current picture of the access unit of the first layer, the video encoder 200 and the video decoder 300 may be configured to perform a picture output and remove process on the DPB, such as described below with respect to section C.5.2.2. After removing the last decoding unit of the current picture from the CPB, the video encoder 200 and the video decoder 300 may be configured to perform a picture bumping process across all layers of the DPB, as described below with respect to sections C.5.2.3 and C.5.2.4.

[0099]

[0092] In one example, the picture output and removal process and the additional bumping process are invoked for each layer, where for a coded layer video sequence start (CLVSS) picture (intra random access point (IRAP) picture), the sub-DPB is emptied while the "bumping" process C.5.2.4 operates on the entire DPB across layers, since it may be the case that the AU is incomplete (pictures of all layers are not present) but pictures of other layers may need to be output before the picture of the layer currently present in the AU.

[0100]

[0093] When a sub-DPB is emptied layer-by-layer, ie when a picture with a certain layer ID is emptied, the picture "bumping" process is called for the entire DPB, including pictures of all layers.

[0101]

[0094] In a similar manner, the processes of DPB operations (e.g., section C.3) are invoked for or per layer, but when a picture is output or emptied, such processes are invoked for all pictures in the DPB, e.g., across layers.

[0102]

[0095] In one example, this technique can be implemented by removing the condition from the relevant section from VVC Draft 7 that "when these processes are applied for a particular layer, only the sub-DPBs for the particular layer are affected."

[0103]

[0096] In some examples, picture removal may only be applied within each layer, but picture output may be applied across different layers.

[0104]

[0097] As part of implementing the techniques described above, the video encoder 200 and / or the video decoder 300 may be configured to maintain a decoded picture buffer (DPB) for storing reference pictures for multiple layers, where the DPB comprises sub-DPBs for storing reference pictures for layers of the multiple layers, decode pictures of the video data, and store copies of the decoded pictures in the DPB as reference pictures.

[0105]

[0098] The video encoder 200 and / or the video decoder 300 may also be configured to determine a fullness of the sub-DPB and / or to determine a fullness of the DPB. The video encoder 200 and / or the video decoder 300 may also be configured to initialize a fullness of the sub-DPB to 0 in response to a first picture of a video sequence being parsed and / or to initialize a fullness of the sub-DPB to 0 in response to a first slice of a CLVSS picture 0 with the lowest nuh_layer_id being parsed. The video encoder 200 and / or the video decoder 300 may also be configured to mark pictures stored in the sub-DPB with a status.

[0106] In one example using VVC Draft 7, the techniques of this disclosure may be implemented with the following modifications to the picture output and removal description: <add> " indicates the start of additional proposed by this disclosure, and the tag "< / add> " indicates the end of these additions. <del> " indicates the start of the deletion (i.e., text removal) proposed by this disclosure, and the tag "< / del> " indicates the end of their deletion.

[0107] In the following description, an AU represents a set PU that contains coded pictures belonging to different layers and associated with the same time for output from the DPB. A decoding unit (DU) refers to an AU if DecodingUnitHrdFlag is equal to 0, or a subset of an AU consisting of one or more VCL NAL units and associated non-VCL NAL units in the AU. 8.3.3 Decoding process for reference picture marking This process is invoked once per picture after the decoding of the slice header and the decoding process for building a reference picture list for a slice, specified in section 8.3.2, but before the decoding of the slice data. This process may mark one or more reference pictures in the DPB as "unused for reference" or "used for long-term reference".

[0108] A decoded picture in the DPB may be marked as "not used for reference", "used for short-term reference" or "used for long-term reference", but only one between these three may be marked at a given moment during the operation of the decoding process. Assigning one of these markings to a picture implicitly removes another one of these markings, when applicable. When a picture is referred to as being marked "used for reference", this refers collectively to pictures that are marked as "used for short-term reference" or "used for long-term reference" (but not both).

[0109] STRPs and ILRPs are identified by their nuh_layer_id and PicOrderCntVal values. LTRPs are identified by their nuh_layer_id value and the Log2(MaxLtPicOrderCntLsb) LSB of their PicOrderCntVal value.

[0110] If the current picture is a CLVSS picture, all reference pictures currently in the DPB (if any) with the same nuh_layer_id as the current picture are marked as "unused for reference".

[0111] In other cases the following applies:

[0112] - For each LTRP entry in RefPicList[0] or RefPicList[1], if the picture is a STRP with the same nuh_layer_id as the current picture, the picture is marked as "used for long term reference".

[0113] - Each reference picture with the same nuh_layer_id as the current picture in the DPB that is not referenced by any entry in RefPicList[0] or RefPicList[1] is marked as "unused for reference".

[0114] - For each ILRP entry in RefPicList[0] or RefPicList[1], the picture is marked as "used for long-term reference".

[0115] <add> Pictures in the DPB with a different nuh_layer_id than the current picture retain their DPB status from the previous picture marking.< / add> In some examples, it may be specified that the reference picture markings of the current picture do not affect the reference picture markings of pictures that have a nuh_layer_id that is not equal to the nuh_layer_id of the current picture. C.5.2 Output Order DPB Operation C.5.2.1 General The specifications in this section apply independently to each set of DPB parameters selected, as specified in Section C.1.

[0116] A DPB is conceptually composed of sub-DPBs, each of which contains a picture storage buffer for the storage of decoded pictures of one layer. Each of the picture storage buffers contains decoded pictures that are marked as "used for reference" or are retained for future output.

[0117] The process for outputting and removing pictures from the DPB prior to the decoding of the current picture, specified in clause C.5.2.2, is invoked, followed by the invocation of the process for currently decoded picture marking and storage, specified in clause C.3.4, and finally the invocation of the process for additional bumping, specified in clause C.5.2.3. The "bumping" process is specified in clause C.5.2.4 and is invoked as specified in clauses C.5.2.2 and C.5.2.3.

[0118] <del> These processes< / del> <add> Sections C.5.2.2, "Output and Removal of Pictures from the DPB" and C.5.2.3, "Additional Bumping"< / add> is applied independently for each layer in ascending order of the nuh_layer_id values ​​of the layers in the OLS, starting with the lowest layer in the OLS. <del> When these processes are applied for a particular layer, only the sub-DPBs for that particular layer are affected.< / del> <add> Section C.5.2.4 applies to all pictures of any layer in the DPB.< / add> NOTE – In Output Order DPB operation, just as in Output Timing DPB operation, decoded pictures with PicOutputFlag equal to 1 in the same access unit are also output consecutively in ascending order of the decoded pictures' nuh_layer_id values.

[0119] Let picture n and current picture be the coded or decoded pictures of access unit n for a particular value of nuh_layer_id, where n is a non-negative integer. C.5.2.2 Outputting and Removing Pictures from the DPB Output and removal of a picture from the DPB, before decoding of the current picture (but after parsing the slice header of the first slice of the current picture), occurs the instant the first DU of the AU containing the current picture is removed from the CPB, and proceeds as follows: - The decoding process for reference picture list construction specified in clause 8.3.2 and the decoding process for reference picture marking specified in clause 8.3.3 are invoked. - If the current picture is a CLVSS picture that is not picture 0, the following ordered steps apply:

[0120] 1. The variable NoOutputOfPriorPicsFlag is derived for the decoder under test as follows:

[0121] - If the values ​​of pic_width_max_in_luma_samples, pic_height_max_in_luma_samples, chroma_format_idc, separate_colour_plane_flag, bit_depth_minus8, or max_dec_pic_buffering_minus1[Htid] derived for any picture in the current AU are different from the values ​​of pic_width_max_in_luma_samples, pic_height_max_in_luma_samples, chroma_format_idc, separate_colour_plane_flag, bit_depth_minus8, or max_dec_pic_buffering_minus1[Htid], respectively, for a preceding picture in the same CLVS, then NoOutputOfPriorPicsFlag MAY (but should not be set to) 1 by the decoder under test, regardless of the value of no_output_of_prior_pics_flag.

[0122] NOTE - Under these conditions it is preferred to set NoOutputOfPriorPicsFlag equal to no_output_of_prior_pics_flag, however the decoder under test is allowed to set NoOutputOfPriorPicsFlag to 1 in this case.

[0123] - Otherwise, NoOutputOfPriorPicsFlag is set equal to no_output_of_prior_pics_flag.

[0124] 2. The value of NoOutputOfPriorPicsFlag derived for the decoder under test is applied to the HRD as follows:

[0125] - If NoOutputOfPriorPicsFlag is equal to 1, <del> DPB< / del> <add> Sub DPB< / add> All picture storage buffers in are emptied without outputting the pictures they contain, and the DPB fullness is <del> Set equal to 0< / del> <add> For each picture storage buffer emptied, it is decremented by 1.< / add> .

[0126] [An alternative wording using sub-DPB fullness would be if NoOutputOfPriorPicsFlag is equal to 1: <del> DPB< / del> <add> Sub DPB< / add> all picture storage buffers in are emptied without outputting the pictures they contain, <del> DPB< / del> <add> Sub DPB< / add> Fullness is set equal to 0.] - otherwise (NoOutputOfPriorPicsFlag is equal to 0), all picture storage buffers containing pictures marked as "not needed for output" and "not used for reference" are emptied (without output), <del> DPB< / del> <add> Sub DPB< / add> All non-empty picture storage buffers in are emptied by repeatedly invoking the "bumping" process specified in clause C.5.2.4, and the DPB fullness is <del> Set equal to 0< / del> <add> For each picture storage buffer emptied, it is decremented by 1.< / add> .

[0127] [An alternative wording using sub-DPB fullness would state that in other cases (NoOutputOfPriorPicsFlag equals 0), all picture storage buffers containing pictures marked as "not needed for output" and "not used for reference" are emptied (without output),<del> DPB< / del> <add> Sub DPB< / add> all non-empty Picture Storage Buffers in are emptied by repeatedly invoking the "bumping" process specified in Clause C.5.2.4; <del> DPB< / del> <add> Sub DPB< / add> Fullness is set equal to 0.] - [An alternative wording would be that in other cases (NoOutputOfPriorPicsFlag equals 0), all picture storage buffers containing pictures marked as "not needed for output" and "not used for reference" are emptied (without output), <add> All< / add> <del> DPB< / del> <add> Sub DPB< / add> all non-empty Picture Storage Buffers in are emptied by repeatedly invoking the "bumping" process specified in Clause C.5.2.4; <add> All sub-DPBs< / add> <del> DPB< / del> <add> Sub DPB< / add> Fullness is set equal to 0.] Otherwise (the current picture is not a CLVSS picture) <add> or the CLVSS picture is picture 0< / add> ), all picture storage buffers containing pictures marked as "not needed for output" and "not used for reference" are emptied (without output). For each picture storage buffer that is emptied, the DPB fullness is decremented by one. When one or more of the following conditions are true, the "bumping" process specified in clause C.5.2.4 is repeatedly invoked, further decrementing the DPB fullness by one for each additional picture storage buffer that is emptied, until none of the following conditions are true:

[0128] - The number of pictures in the DPB marked as "needed for output" is greater than max_num_reorder_pics[Htid].

[0129] - max_latency_increase_plus1[Htid] is not equal to 0 and there is at least one picture in the DPB marked as "required for output" for which the associated variable PicLatencyCount is greater than or equal to MaxLatencyPictures[Htid].

[0130] - The number of pictures in the DPB is greater than or equal to max_dec_pic_buffering_minus1[Htid]+1. C.5.2.3 Additional Bumping The process specified in this section occurs the instant the last DU of AU n that currently contains the picture is removed from the CPB.

[0131] When the current picture has PictureOutputFlag equal to 1, for each picture in the DPB that is marked as "required for output" and that follows the current picture in output order, the associated variable PicLatencyCount is set equal to PicLatencyCount+1.

[0132] The following applies: - If the currently decoded picture has PictureOutputFlag equal to 1, it is marked as "needed for output" and its associated variable PicLatencyCount is set equal to 0. - Otherwise (the currently decoded picture has PictureOutputFlag equal to 0), it is marked as "not needed for output".

[0133] When one or more of the following conditions are true, the "bumping" process specified in section C.5.2.4 is repeatedly invoked until none of the following conditions are true: - The number of pictures in the DPB marked as "required for output" is greater than max_num_reorder_pics[Htid]. - max_latency_increase_plus1[Htid] is not equal to 0 and there is at least one picture in the DPB marked as "required for output" for which the associated variable PicLatencyCount is greater than or equal to MaxLatencyPictures[Htid]. C.5.2.4 "Bumping" Process The "bumping" process consists of the following ordered steps: 1. The picture or pictures that are the first for output are selected as the pictures with the minimum value of PicOrderCntVal among all pictures in the DPB marked as "required for output". 2. Each of these pictures, in ascending order of nuh_layer_id, is cropped using the adaptive cropping window for pictures, the cropped picture is output, and the picture is marked as "not needed for output". 3. Each picture storage buffer that is marked as "unused for reference" and contains a picture that was one of the pictures that was cropped and output is emptied; <del> Related Sub< / del> The fullness of the DPB is decremented by one.

[0134] NOTE - For any two pictures picA and picB that belong to the same CVS and are output by the "bumping process", if picA is output earlier than picB, the value of PicOrderCntVal of picA is less than the value of PicOrderCntVal of picB. <add> or equal to< / add> .

[0135]

[0101] Figure 3 is a block diagram illustrating an example video encoder 200 that may implement the techniques of this disclosure. Figure 3 is provided for illustrative purposes and should not be considered as limiting the techniques broadly illustrated and described in this disclosure. For illustrative purposes, 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] 3, 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 DPB 218, and an entropy encoding unit 220. Any 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, an inverse quantization unit 210, an inverse transform processing unit 212, a reconstruction unit 214, a filter unit 216, a DPB 218, and an entropy encoding unit 220 may be implemented in one or more processors or processing circuits. For example, the units of video encoder 200 may be implemented as one or more circuits or logic elements, as part of a hardware circuit, or as part of a processor in an FPGA, an ASIC, etc. Moreover, video encoder 200 may include additional or alternative processors or processing circuits for performing these and other functions.

[0137]

[0103] The video data memory 230 may store video data to be encoded by components of the video encoder 200. The video encoder 200 may receive video data stored in the video data memory 230, for example, from the video source 104 (FIG. 1). The DPB 218 may act as a reference picture memory that stores reference video data for use in predicting subsequent video data by the video encoder 200. The video data memory 230 and the DPB 218 may be formed by any of a variety of memory devices, such as synchronous dynamic random access memory (DRAM), including DRAM (SDRAM), magnetoresistive RAM (MRAM), resistive RAM (RRAM), or other types of memory devices. The video data memory 230 and the DPB 218 may be provided by the same memory device or separate memory devices. In various examples, the video data memory 230 may be on-chip with other components of the video encoder 200, as shown, or off-chip relative to those components.

[0138]

[0104] The DPB 218 may include a shared multi-layer DPB 219. As described in more detail elsewhere in this disclosure, the video encoder 200 may be configured to store reference pictures for multiple layers in the shared multi-layer DPB 219. Prior to decoding the current picture of the access unit of the first layer, the video encoder 200 may perform a picture output and removal process on the shared multi-layer DPB 219 to remove only some decoded pictures belonging to the first layer from the shared multi-layer DPB 219. After removing the last decoded unit of the current picture from the CPB, the video encoder 200 may perform a picture bumping process across all layers of the shared multi-layer DPB 219.

[0139] In this disclosure, references to video data memory 230 should not be construed as limited to memory internal to video encoder 200 unless specifically so described, or to memory external to video encoder 200 unless specifically so described. Instead, references to video data memory 230 should be understood as a reference memory that stores video data that video encoder 200 receives for encoding (e.g., video data for a current block to be encoded). Memory 106 of FIG. 1 may also provide temporary storage of outputs from various units of video encoder 200.

[0140]

[0106] The various units in FIG. 3 are shown to aid in understanding the operations performed by the video encoder 200. The units may be implemented as fixed-function circuits, programmable circuits, or a combination thereof. A fixed-function circuit refers to a circuit that provides a specific function and is preset with respect to the operations that may be performed. A programmable circuit refers to a circuit that may be programmed to perform various tasks and provide flexible functionality in the operations that may 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 software or firmware instructions. A fixed-function circuit may execute software instructions (e.g., to receive parameters or output parameters), but the type of operations that the fixed-function circuit performs is generally invariant. In some examples, one or more of the units may be separate circuit blocks (fixed function or programmable), and in some examples, one or more of the units may be an integrated circuit.

[0141]

[0107] The video encoder 200 may include an arithmetic logic unit (ALU), a basic functional unit (EFU), a programmable core formed of digital circuits, analog circuits, and / or programmable circuits. In examples in which the operations of the video encoder 200 are implemented using software executed by a programmable circuit, the memory 106 (FIG. 1) may store instructions (e.g., object code) of the software that the video encoder 200 receives and executes, or another memory (not shown) within the video encoder 200 may store such instructions.

[0142]

[0108] The video data memory 230 is configured to store the received video data. The video encoder 200 may retrieve pictures 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 raw video data to be encoded.

[0143] 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 for performing video prediction according to other prediction modes. By way of 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.

[0144]

[0110] 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 CTUs into CUs, prediction modes for CUs, transform types for residual data of CUs, quantization parameters for residual data of CUs, etc. The mode selection unit 202 may finally select a combination of encoding parameters that has a rate-distortion value that is better than other tested combinations.

[0145]

[0111] The video encoder 200 may partition a 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 HEVC described above. As described above, the video encoder 200 may form one or more CUs from partitioning the CTUs according to the tree structure. Such a CU may also be generally referred to as a "video block" or a "block."

[0146]

[0112] In general, 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 a current block (e.g., the current CU, or in HEVC, the overlapping portion of the PU and TU). For inter prediction of the current block, the motion estimation unit 222 may perform motion search to identify one or more closely matching reference blocks in one or more reference pictures (e.g., one or more previously coded pictures stored in the DPB 218). In particular, the motion estimation unit 222 may calculate a value representing how similar a potential reference block is to the current block according to, for example, the sum of absolute differences (SAD), the sum of squared differences (SSD), the mean absolute difference (MAD), the mean squared difference (MSD), and the like. The motion estimation unit 222 may generally perform these calculations using the sample-by-sample difference between the current block and the reference block under consideration. Motion estimation unit 222 may identify the reference block having the lowest value resulting from these calculations, which indicates the reference block that most closely matches the current block.

[0147]

[0113] The motion estimation unit 222 may form one or more motion vectors (MVs) that define the position of a reference block in a reference picture relative to the position of a current block in a current picture. The motion estimation unit 222 may then provide the motion vectors to the motion compensation unit 224. For example, in unidirectional inter prediction, the motion estimation unit 222 may provide a single motion vector, while in 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 predictive block. For example, the motion compensation unit 224 may use the motion vectors to retrieve data of a reference block. As another example, if the motion vector has partial sample precision, the motion compensation unit 224 may interpolate values ​​for the predictive block according to one or more interpolation filters. Moreover, in bidirectional inter prediction, the motion compensation unit 224 may retrieve data for two reference blocks identified by the respective motion vectors and combine the retrieved data, for example, through sample-wise averaging or weighted averaging.

[0148]

[0114] As another example, for intra prediction, or intra predictive coding, the intra prediction unit 226 may generate a predictive block from samples adjacent to a current block. For example, in a directional mode, the intra prediction unit 226 may generally mathematically combine values ​​of adjacent samples and populate these calculated values ​​in a defined direction across the current block to generate a predictive block. As another example, in a DC mode, the intra prediction unit 226 may calculate an average of the adjacent samples for the current block and generate a predictive block to include this obtained average for each sample of the predictive block.

[0149]

[0115] The mode selection unit 202 provides the prediction block to the residual generation unit 204. The residual generation unit 204 receives a raw 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 sample-by-sample differences between the current block and the prediction block. The resulting sample-by-sample differences define a residual block for the current block. In some examples, the residual generation unit 204 may also determine differences between sample values ​​in the residual block to generate the residual block using residual differential pulse code modulation (RDPCM). In some examples, the residual generation unit 204 may be formed using one or more subtractor circuits that perform binary subtraction.

[0150]

[0116] In an example where the mode selection unit 202 partitions a 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 having various sizes. As indicated above, the size of a CU may refer to the size of the luma coding block of the CU, and the size of a PU may refer to the size of the luma prediction unit of the PU. Assuming that the size of a particular CU is 2N×2N, the video encoder 200 may support a PU size of 2N×2N or N×N for intra prediction, and a symmetric PU size of 2N×2N, 2N×N, N×2N, N×N, or the like for inter prediction. The video encoder 200 and the video decoder 300 may also support asymmetric partitioning of PU sizes of 2N×nU, 2N×nD, nL×2N, and nR×2N for inter prediction.

[0151] In an example in which the mode selection unit 202 does not further partition 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 CU sizes of 2N×2N, 2N×N, or N×2N.

[0152]

[0118] In other video coding techniques, such as intra block copy mode coding, affine mode coding, and linear model (LM) mode coding, as some examples, the mode selection unit 202 generates a predictive block for the current block being coded via a respective unit associated with the coding technique. In some examples, such as palette mode coding, the mode selection unit 202 may not generate a predictive block, but instead generate syntax elements that indicate how the block should be reconstructed based on a selected palette. In such modes, the mode selection unit 202 may provide these syntax elements to be coded to the entropy coding unit 220.

[0153]

[0119] As described above, the residual generation unit 204 receives video data for a current block and a corresponding predictive 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 sample-by-sample differences between the predictive block and the current block.

[0154]

[0120] 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"). Transform processing unit 206 may apply various transforms to the residual block to form the transform coefficient block. For example, transform processing unit 206 may 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, transform processing unit 206 may perform multiple transforms on the residual block, e.g., a linear transform and a secondary transform such as a rotation transform. In some examples, transform processing unit 206 does not apply a transform to the residual block.

[0155]

[0121] The quantization unit 208 may quantize the transform coefficients in the transform coefficient block to generate 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 result in loss of information, and thus the quantized transform coefficients may have lower precision than the original transform coefficients generated by the transform processing unit 206.

[0156]

[0122] The inverse quantization unit 210 and the inverse transform processing unit 212 may apply inverse quantization and inverse transform to the quantized transform coefficient block, respectively, to reconstruct a residual block from the transform coefficient block. The reconstruction unit 214 may generate a reconstructed block corresponding to the current block (potentially with some distortion) based on the reconstructed residual block and the predictive 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 from the predictive block generated by the mode selection unit 202 to generate a reconstructed block.

[0157]

[0123] 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 blockiness artifacts along the edges of a CU. The operations of filter unit 216 may be skipped in some examples.

[0158]

[0124] The video encoder 200 stores the reconstructed block in the DPB 218. For example, in an example where the operation of the filter unit 216 is not performed, the reconstruction unit 214 may store the reconstructed block in the DPB 218. In an example where the operation of the filter unit 216 is performed, the filter unit 216 may store the filtered reconstructed block in the DPB 218. The motion estimation unit 222 and the motion compensation unit 224 may retrieve a reference picture formed from the reconstructed (and potentially filtered) block from the DPB 218 to inter predict blocks of a picture to be subsequently encoded. Furthermore, the intra prediction unit 226 may use the reconstructed block in the DPB 218 of the current picture to intra predict other blocks in the current picture.

[0159] In general, the entropy encoding unit 220 may entropy encode syntax elements received from other functional components of the video encoder 200. For example, the entropy encoding unit 220 may entropy encode quantized transform coefficient blocks from the quantization unit 208. As another example, the entropy encoding unit 220 may entropy encode predictive syntax elements (e.g., motion information for inter prediction, or intra mode information for intra prediction) from the mode selection unit 202. The entropy encoding unit 220 may perform one or more entropy encoding operations on syntax elements, which are another example of video data, to generate entropy encoded data. For example, the entropy encoding 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 partitioned entropy (PIPE) coding operation, an exponential-Golomb coding operation, or another type of entropy coding operation on the data. In some examples, the entropy encoding unit 220 may operate in a bypass mode in which syntax elements are not entropy coded.

[0160]

[0126] Video encoder 200 may output a bitstream that includes entropy coding syntax elements needed to reconstruct blocks of a slice or picture. In particular, entropy coding unit 220 may output the bitstream.

[0161]

[0127] The operations described above are described with respect to blocks. Such descriptions should be understood as being 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 luma and chroma components of a CU. In some examples, the luma coding blocks and chroma coding blocks are luma and chroma components of a PU.

[0162]

[0128] In some examples, the operations performed with respect to the luma coding block do not need to be repeated for the chroma coding block. As an example, the operations for identifying a motion vector (MV) and a reference picture for the luma coding block do not need to be repeated to identify the MV and the reference picture for the chroma block. Rather, the MV for the luma coding block may be scaled to determine the MV for the chroma block, and the reference picture may be the same. As another example, the intra prediction process may be the same for the luma coding block and the chroma coding block.

[0163]

[0129] Video encoder 200 represents an example of a device configured to encode video data, including a memory configured to store the video data and one or more processing units implemented in circuitry, the one or more processing units configured to perform the techniques of the present disclosure, including the techniques described in the claims section below.

[0164]

[0130] Figure 4 is a block diagram illustrating an example video decoder 300 that may implement the techniques of this disclosure. Figure 4 is provided for illustrative purposes and is not intended to limit the techniques broadly illustrated and described in this disclosure. For illustrative purposes, this disclosure describes the video decoder 300 in accordance with JEM, VVC, and HEVC techniques. However, the techniques of this disclosure may be implemented by video coding devices configured for other video coding standards.

[0165]

[0131] In the example of Figure 4, the video decoder 300 includes a 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 DPB 314. 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 314 may be implemented in one or more processors or processing circuits. For example, the units of the video decoder 300 may be implemented as one or more circuits or logic elements, as part of a hardware circuit, or as part of a processor of an FPGA, an ASIC. Moreover, the video decoder 300 may include additional or alternative processors or processing circuits for performing these and other functions.

[0166]

[0132] The prediction processing unit 304 includes a motion compensation unit 316 and an intra prediction unit 318. The prediction processing unit 304 may include additional units for performing prediction according to other prediction modes. By way of 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.

[0167]

[0133] The CPB memory 320 may store video data, such as an encoded video bitstream, to be decoded by components of the video decoder 300. The video data stored in the CPB memory 320 may be obtained, for example, from the computer-readable medium 110 (FIG. 1). The CPB memory 320 may include a CPB that stores encoded video data (e.g., syntax elements) from the encoded video bitstream. The CPB memory 320 may also store video data other than syntax elements of coded pictures, such as temporary data representing output from various units of the video decoder 300. The DPB 314 generally stores decoded pictures that the video decoder 300 may output and / or use as reference video data when decoding subsequent data or pictures of the encoded video bitstream. The CPB memory 320 and the 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. The CPB memory 320 and the DPB 314 may be provided by the same memory device or separate memory devices. In various examples, the CPB memory 320 may be on-chip with other components of the video decoder 300 or off-chip relative to those components.

[0168] Additionally or alternatively, in some examples, the video decoder 300 may retrieve coded video data from memory 120 (FIG. 1). That is, memory 120 may store data as described above along with CPB memory 320. Similarly, memory 120 may store instructions to be executed by the video decoder 300 when some or all of the functionality of the video decoder 300 is implemented in software to be executed by processing circuitry of the video decoder 300.

[0169]

[0135] The various units shown in FIG. 4 are shown to aid in understanding the operations performed by the video decoder 300. The units may be implemented as fixed-function circuits, programmable circuits, or a combination thereof. As in FIG. 3, a fixed-function circuit refers to a circuit that provides a specific function and is preset with respect to the operations that may be performed. A programmable circuit refers to a circuit that may be programmed to perform various tasks and provide flexible functionality in the operations that may 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 software or firmware instructions. A fixed-function circuit may execute software instructions (e.g., to receive parameters or output parameters), but the type of operations that the fixed-function circuit performs is generally invariant. In some examples, one or more of the units may be separate circuit blocks (fixed function or programmable), and in some examples, one or more of the units may be an integrated circuit.

[0170]

[0136] The video decoder 300 may include a programmable core formed from an ALU, an EFU, a digital circuit, an analog circuit, and / or a programmable circuit. In examples in which the operation of the video decoder 300 is performed by software executing on a programmable circuit, 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.

[0171]

[0137] The entropy decoding unit 302 may receive the encoded video data from the CPB and entropy decode the video data to recover 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.

[0172]

[0138] Generally, 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 the block currently being reconstructed, i.e., the block currently being decoded, may be referred to as the "current block").

[0173]

[0139] The entropy decoding unit 302 may entropy decode syntax elements defining the quantized transform coefficients of the quantized transform coefficient block, as well as transform information such as a quantization parameter (QP) and / or a transform mode indication(s). The inverse quantization unit 306 may use the QP associated with the quantized transform coefficient block to determine the degree of quantization and, similarly, the degree of inverse quantization that the inverse quantization unit 306 should apply. The inverse quantization unit 306 may perform, for example, 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.

[0174] 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 transform, or another inverse transform to the transform coefficient block.

[0175]

[0141] Furthermore, the prediction processing unit 304 generates a prediction block according to the prediction information syntax element entropy decoded by the entropy decoding unit 302. For example, if the prediction information syntax element indicates that the current block is inter-predicted, the motion compensation unit 316 may generate a prediction block. In this case, the prediction information syntax element may indicate a reference picture in the DPB 314 from which the reference block should be retrieved, as well as a motion vector that identifies the location of the reference block in the reference picture relative to the location of the current block in the current picture. The motion compensation unit 316 may generally perform an inter-prediction process in a manner substantially similar to that described with respect to the motion compensation unit 224 (FIG. 3).

[0176]

[0142] 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 perform an intra prediction process in a manner substantially similar to that described with respect to the intra prediction unit 226 (FIG. 3). The intra prediction unit 318 may retrieve data of neighboring samples for the current block from the DPB 314.

[0177]

[0143] The reconstruction unit 310 may reconstruct the current block using the predictive block and the residual block. For example, the reconstruction unit 310 may add samples of the residual block to corresponding samples of the predictive block to reconstruct the current block.

[0178]

[0144] 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 blockiness artifacts along edges of the reconstructed block. The operations of the filter unit 312 are not necessarily performed in all examples.

[0179]

[0145] The video decoder 300 may store the reconstructed block in the DPB 314. For example, in an example where the operation of the filter unit 312 is not performed, the reconstruction unit 310 may store the reconstructed block in the DPB 314. In an example where the operation of the filter unit 312 is performed, the filter unit 312 may store the filtered reconstructed block in the DPB 314. As described above, the DPB 314 may provide reference information to the prediction processing unit 304, such as samples of a current picture for intra prediction and previously decoded pictures for subsequent motion compensation. Moreover, the video decoder 300 may output the decoded picture (e.g., decoded video) from the DPB 314 for subsequent presentation on a display device, such as the display device 118 of FIG. 1.

[0180]

[0146] The DPB 314 may include a shared multi-layer DPB 315. As described in more detail elsewhere in this disclosure, the video decoder 300 may be configured to store reference pictures for multiple layers in the shared multi-layer DPB 315. Prior to decoding the current picture of the access unit of the first layer, the video decoder 300 may perform a picture output and removal process on the shared multi-layer DPB 315 to remove only some decoded pictures belonging to the first layer from the shared multi-layer DPB 315. After removing the last decoded unit of the current picture from the CPB memory 320, the video decoder 300 may perform a picture bumping process across all layers of the shared multi-layer DPB 315. That is, the video decoder 300 may perform a picture bumping process that is not limited to a particular layer, but instead bumps pictures from layers other than the layer of the current picture.

[0181]

[0147] In this manner, the video decoder 300 represents one example of a video decoding device that includes a memory configured to store video data and one or more processing units implemented in circuitry configured to perform the techniques of the present disclosure, including the techniques described in the claims section below.

[0182]

[0148] Figure 5 is a flowchart illustrating an example process for encoding a current block. The current block may comprise a current CU. Although described with respect to video encoder 200 (Figures 1 and 3), it should be understood that other devices may be configured to perform a process similar to that of Figure 5.

[0183]

[0149] In this example, the video encoder 200 first predicts the current block (350). For example, the video encoder 200 may form a predictive block for the current block. The video encoder 200 may then calculate a residual block for the current block (352). To calculate the residual block, the video encoder 200 may calculate a difference between an original uncoded block and a predictive block for the current block. The video encoder 200 may then transform and quantize coefficients of the residual block (354). The video encoder 200 may then scan the quantized transform coefficients of the residual block (356). During or following the scan, the video encoder 200 may entropy code the transform coefficients (358). For example, the video encoder 200 may code the transform coefficients using CAVLC or CABAC. The video encoder 200 may then output entropy coded data for the block (360).

[0184]

[0150] Figure 6 is a flowchart illustrating an example process for decoding a current block of video data. The current block may comprise a current CU. Although described with respect to video decoder 300 (Figures 1 and 4), it should be understood that other devices may be configured to perform a process similar to that of Figure 6.

[0185]

[0151] The video decoder 300 may receive entropy coded data for the 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 to reconstruct the coefficients of the residual block (372). The video decoder 300 may predict the current block, e.g., using an intra-prediction or inter-prediction mode indicated by the prediction information for the current block, to calculate a predictive block for the current block (374). The video decoder 300 may then inverse scan the reconstructed coefficients to create a block of quantized transform coefficients (376). The video decoder 300 may then inverse quantize and inverse transform the transform coefficients to generate a residual block (378). The video decoder 300 may finally decode the current block by combining the predictive block and the residual block (380).

[0186]

[0152] Figure 7 is a flowchart illustrating an example process for decoding video data. The technique of Figure 7 may be implemented by a video decoder, such as video decoder 300 (Figures 1 and 4), or by a video decoding loop of a video encoder, such as video encoder 200 (Figures 1 and 3).

[0187]

[0153] The video decoder maintains a DPB (400) for storing reference pictures for multiple layers. The DPB stores previously decoded pictures. The multiple layers include at least a first layer and a second layer.

[0188]

[0154] Prior to decoding the current picture of the access unit of the first layer, the video decoder performs a picture output and removal process on the DPB by removing only the decoded pictures belonging to the first layer from the DPB (402). The video decoder may perform the picture output and removal process on the DPB, for example, prior to decoding the current picture of the first layer and after parsing the slice header for the slice of the current picture. The video decoder may perform the picture output and removal process on the DPB, for example, in response to removing the first decoding unit of the current picture from the CPB. The CPB may store encoded multi-layer video data for decoding.

[0189]

[0155] After removing the last decoding unit of the current picture from the CPB, the video decoder performs a picture bumping process across all layers of the DPB (404). To perform the picture bumping process across all layers of the DPB, the video decoder may remove at least one picture of the second layer from the DPB. To perform the picture bumping process across all layers of the DPB, the video decoder may, for example, remove reference pictures from the DPB that are marked as not required for output and not used for reference.

[0190]

[0156] The video decoder may identify a reference picture in the DPB, identify a predictive block for a current block of the current picture in the reference picture, decode the current block based on the predictive block, and output a decoded version of the current picture, where the decoded version of the current picture includes a decoded version of the current block.

[0191]

[0157] The following clauses represent examples of the techniques and devices described above.

[0192]

[0158] Clause 1: A device for decoding multi-layer video data includes a memory configured to store multi-layer video data and one or more processors implemented in a circuit, wherein the one or more processors are configured to maintain a decoded picture buffer (DPB) for storing reference pictures for a plurality of layers, wherein the plurality of layers comprises at least a first layer and a second layer, and to perform a picture output and removal process on the DPB prior to decoding a current picture of an access unit of a first layer, wherein the plurality of layers comprises at least a first layer and a second layer, and wherein to perform the picture output and removal process on the DPB, the one or more processors perform a picture bumping process across all layers of the DPB after removing a last decoded unit of the current picture from a coded picture buffer (CPB), which is further configured to remove from the DPB only decoded pictures belonging to the first layer.

[0193]

[0159] Clause 2: The device described in Clause 1, wherein to perform a picture output and removal process on the DPB, the one or more processors are further configured to perform a picture output and removal process on the DPB before decoding a current picture of the first layer and after parsing a slice header for a slice of the current picture.

[0194]

[0160] Clause 3: A device described in any of clauses 1 and 2, further configured to perform a picture output and removal process on the DPB, in response to one or more processors removing the first decoding unit of the current picture from the CPB, to perform a picture output and removal process on the DPB.

[0195]

[0161] Clause 4: A device described in any of clauses 1 to 3, wherein to perform a picture bumping process across all layers of the DPB, one or more processors are further configured to remove reference pictures from the DPB that are marked as not required for output and that are marked as not used for reference.

[0196]

[0162] Clause 5: A device described in any of clauses 1 to 4, wherein one or more processors are further configured to remove at least one picture of the second layer from the DPB to perform a picture bumping process across all layers of the DPB.

[0197]

[0163] Clause 6: A device described in any of clauses 1 to 5, wherein the one or more processors are further configured to identify a reference picture in the DPB, identify a predictive block for a current block of the current picture in the reference picture, decode the current block based on the predictive block, and output a decoded version of the current picture, wherein the decoded version of the current picture includes a decoded version of the current block.

[0198]

[0164] Clause 7: A device described in any of clauses 1 to 6, wherein the DPB is configured to store previously decoded pictures and the CPB is configured to store encoded multi-layer video data.

[0199]

[0165] Clause 8: A device described in any of clauses 1 to 7, wherein the one or more processors are further configured to maintain a DPB and a CPB in the memory.

[0200]

[0166] Clause 9: A device according to any one of clauses 1 to 8, comprising a wireless communication device, the device further comprising a receiver configured to receive encoded multi-layer video data.

[0201]

[0167] Clause 10: The device described in clause 9, wherein the wireless communication device comprises a telephone handset, wherein the receiver is configured to demodulate a signal comprising encoded multi-layer video data in accordance with a wireless communication standard.

[0202]

[0168] Clause 11: A device according to any one of clauses 1 to 8, comprising a wireless communication device, the device further comprising a transmitter configured to transmit the encoded multi-layer video data.

[0203]

[0169] Clause 12: The device of clause 11, wherein the wireless communication device comprises a telephone handset, wherein the transmitter is configured to modulate a signal comprising encoded multi-layer video data in accordance with a wireless communication standard.

[0204]

[0170] Clause 13: The device described in any of clauses 1 to 12 further includes a display configured to display decoded multi-layer video data comprising a decoded version of the current picture.

[0205]

[0171] Clause 14: A device according to any of clauses 1 to 13, wherein the device comprises one or more of a camera, a computer, a mobile device, a broadcast receiver device, or a set-top box.

[0206]

[0172] Clause 15: A method for decoding multi-layer video data includes maintaining a decoded picture buffer (DPB) for storing reference pictures for a plurality of layers, wherein the plurality of layers comprises at least a first layer and a second layer, performing a picture output and removal process on the DPB prior to decoding a current picture of an access unit of a first layer, wherein performing a picture output and removal process on the DPB comprises removing only decoded pictures belonging to the first layer from the DPB, and performing a picture bumping process across all layers of the DPB after removing a last decoded unit of the current picture from a coded picture buffer (CPB), wherein performing the picture output and removal process on the DPB comprises removing from the DPB only decoded pictures belonging to the first layer.

[0207]

[0173] Clause 16: The method described in clause 15, wherein performing a picture output and removal process on the DPB comprises performing a picture output and removal process on the DPB before decoding a current picture of the first layer and after parsing a slice header for a slice of the current picture.

[0208]

[0174] Clause 17: A method as described in any of clauses 15 and 16, wherein performing a picture output and removal process on the DPB comprises performing a picture output and removal process on the DPB in response to removing a first decoding unit of the current picture from the CPB.

[0209]

[0175] Clause 18: A method as described in any of clauses 15 to 17, wherein performing a picture bumping process across all layers of the DPB comprises removing from the DPB reference pictures that are marked as not required for output and that are marked as not used for reference.

[0210]

[0176] Clause 19: The method of any of clauses 15 to 18, wherein performing a picture bumping process across all layers of the DPB comprises removing at least one picture of the second layer from the DPB.

[0211]

[0177] Clause 20: The method according to any of clauses 15 to 19 further includes identifying a reference picture in the DPB, identifying a predictive block for a current block of the current picture in the reference picture, decoding the current block based on the predictive block, and outputting a decoded version of the current picture, wherein the decoded version of the current picture includes a decoded version of the current block.

[0212]

[0178] Clause 21: The method of clause 20, further comprising displaying a decoded version of the current picture.

[0213]

[0179] Clause 22: The method of any of clauses 15 to 21, wherein the DPB is configured to store previously decoded pictures and the CPB is configured to store encoded multi-layer video data.

[0214]

[0180] Clause 23: The method of any of clauses 15 to 20 or 22, wherein the decoding method is performed as part of an encoding process.

[0215]

[0181] Clause 24: A computer-readable storage medium storing instructions which, when executed by one or more processors, cause the one or more processors to maintain a decoded picture buffer (DPB) for storing reference pictures for a plurality of layers, wherein the plurality of layers comprises at least a first layer and a second layer, and to perform a picture output and removal process on the DPB prior to decoding a current picture of an access unit of a first layer, wherein the plurality of layers comprises at least a first layer and a second layer, and wherein, to perform the picture output and removal process on the DPB, the instructions cause the one or more processors to perform a picture bumping process across all layers of the DPB after removing the last decoded unit of the current picture from a coded picture buffer (CPB), which causes the one or more processors to remove only decoded pictures belonging to the first layer from the DPB.

[0216]

[0182] Clause 25: A computer-readable storage medium as described in Clause 24, wherein to perform a picture output and removal process on the DPB, the instructions cause one or more processors to perform a picture output and removal process on the DPB before decoding a current picture of the first layer and after parsing a slice header for a slice of the current picture.

[0217]

[0183] Clause 26: A computer-readable storage medium as described in any of clauses 24 and 25, wherein instructions cause one or more processors to perform a picture output and removal process on the DPB in response to removing a first decoding unit of the current picture from the CPB, to perform a picture output and removal process on the DPB.

[0218]

[0184] Clause 27: A computer-readable storage medium as described in any of clauses 24 to 26, wherein, to perform a picture bumping process across all layers of the DPB, instructions cause one or more processors to remove reference pictures from the DPB that are marked as not required for output and that are marked as not used for reference.

[0219]

[0185] Clause 28: A computer-readable storage medium described in any of clauses 24 to 27, wherein instructions cause one or more processors to remove at least one picture of the second layer from the DPB to perform a picture bumping process across all layers of the DPB.

[0220]

[0186] Clause 29: A computer-readable storage medium according to any of clauses 24 to 28, wherein the instructions further cause one or more processors to identify a reference picture in the DPB, identify a predictive block for a current block of the current picture in the reference picture, decode the current block based on the predictive block, and output a decoded version of the current picture, wherein the decoded version of the current picture includes a decoded version of the current block.

[0221]

[0187] Clause 30: A computer-readable storage medium described in any of clauses 24 to 29, wherein the DPB is configured to store previously decoded pictures and the CPB is configured to store encoded multi-layer video data.

[0222]

[0188] Clause 31: An apparatus for decoding multi-layer video data includes means for maintaining a decoded picture buffer (DPB) for storing reference pictures for a plurality of layers, wherein the plurality of layers comprises at least a first layer and a second layer, means for performing a picture output and removal process on the DPB prior to decoding a current picture of an access unit of a first layer, wherein performing the picture output and removal process on the DPB comprises removing only decoded pictures belonging to the first layer from the DPB, and means for performing a picture bumping process across all layers of the DPB after removing the last decoded unit of the current picture from a coded picture buffer (CPB), wherein performing the picture output and removal process on the DPB comprises removing only decoded pictures belonging to the first layer from the DPB.

[0223]

[0189] Clause 32: The apparatus described in Clause 31, wherein the means for performing a picture output and removal process on the DPB includes means for performing a picture output and removal process on the DPB before decoding a current picture of a first layer and after parsing a slice header for a slice of the current picture.

[0224]

[0190] Clause 33: An apparatus described in any of clauses 31 and 32, wherein the means for performing a picture output and removal process on the DPB comprises means for performing a picture output and removal process on the DPB in response to removing the first decoding unit of the current picture from the CPB.

[0225]

[0191] Clause 34: An apparatus described in any of clauses 31 to 33, wherein the means for performing a picture bumping process across all layers of the DPB comprises means for removing reference pictures from the DPB that are marked as not required for output and that are marked as not used for reference.

[0226]

[0192] Clause 35: An apparatus described in any of clauses 31 to 34, wherein the means for performing a picture bumping process across all layers of the DPB comprises means for removing at least one picture of the second layer from the DPB.

[0227]

[0193] Clause 36: The apparatus described in any of clauses 31 to 35 further includes means for identifying a reference picture in the DPB, means for identifying a predictive block for a current block of the current picture in the reference picture, means for decoding the current block based on the predictive block, and means for outputting a decoded version of the current picture, wherein the decoded version of the current picture includes a decoded version of the current block.

[0228]

[0194] Clause 37: The device of any of clauses 31 to 36, wherein the DPB is configured to store previously decoded pictures and the CPB is configured to store encoded multi-layer video data.

[0229]

[0195] Clause 38: The apparatus of any of clauses 31 to 37, wherein the apparatus for decoding multi-layer video data is part of a video encoder.

[0230]

[0196] Clause 39: A method for decoding video data includes maintaining a decoded picture buffer (DPB) for storing reference pictures for a plurality of layers, wherein the DPB comprises a sub-DPB for storing reference pictures for a layer among the plurality of layers, decoding a picture of the video data, and storing a copy of the decoded picture in the DPB as a reference picture.

[0231]

[0197] Clause 40: The method of clause 39 further comprises determining fullness of the sub-DPB.

[0232]

[0198] Clause 41: The method of clause 39 or 40 further comprises determining the fullness of the DPB.

[0233]

[0199] Clause 42: The method according to any of clauses 39 to 41, further comprising initialising a fullness of the sub-DPB to 0 in response to the first picture of the video sequence being parsed.

[0234]

[0200] Clause 43: The method according to any one of clauses 39 to 41, further comprising initializing a fullness of the sub-DPB to 0 in response to the first slice of CLVSS picture 0 having the lowest nuh_layer_id being parsed.

[0235]

[0201] Clause 44: The method according to any of clauses 39 to 43, further comprising marking pictures stored in the sub-DPB with a status.

[0236]

[0202] Clause 45: The method according to any of clauses 39 to 44, wherein the DPB comprises a second sub-DPB for storing reference pictures for a second layer of the plurality of layers.

[0237]

[0203] Clause 46: The method of any of clauses 39 to 45, wherein the decoding method is performed as part of an encoding process.

[0238]

[0204] Clause 47: A device for coding video data, the device comprising one or more means for performing the method according to any of clauses 39 to 46.

[0239]

[0205] Clause 48: A device as described in clause 47, wherein the one or more means comprise one or more processors implemented in circuitry.

[0240]

[0206] Clause 49: A device described in any of clauses 46 or 47, further comprising a memory for storing video data.

[0241]

[0207] Clause 50: The device of any of clauses 47 to 49, further comprising a display configured to display the decoded video data.

[0242]

[0208] Clause 51: A device according to any of clauses 47 to 50, wherein the device comprises one or more of a camera, a computer, a mobile device, a broadcast receiver device, or a set-top box.

[0243]

[0209] Clause 52: A device according to any one of clauses 47 to 51, wherein the device comprises a video decoder.

[0244]

[0210] Clause 53: A device according to any one of clauses 47 to 52, wherein the device comprises a video encoder.

[0245]

[0211] Clause 54: A computer-readable storage medium storing instructions that, when executed, cause one or more processors to perform a method according to any one of clauses 39 to 46.

[0246]

[0212] In accordance with the above examples, it should be recognized that some acts or events of any of the techniques described herein may be performed in a different sequence, added, merged, or omitted entirely (e.g., not all described acts or events are necessary to the practice of the techniques). Moreover, in some examples, acts or events may be performed simultaneously rather than sequentially, for example, through multi-threaded processing, interrupt processing, or multiple processors.

[0247]

[0213] In one or more examples, the described functions may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions may be stored on or transmitted via a computer-readable medium as one or more instructions or codes and executed by a hardware-based processing unit. The computer-readable medium may include a computer-readable storage medium corresponding to a tangible medium, such as a data storage medium, or a communication medium including any medium that enables the transfer of a computer program from one place to another, for example according to a communication protocol. In this manner, the computer-readable medium may generally correspond to (1) a tangible computer-readable storage medium that is non-transitory, or (2) a communication medium such as a signal or carrier wave. The data storage medium may be any available medium that may be accessed by one or more computers or one or more processors to retrieve instructions, codes and / or data structures for implementation of the techniques described in this disclosure. A computer program product may include a computer-readable medium.

[0248]

[0214] By way of example and not limitation, such computer-readable storage media may comprise RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, flash memory, or any other medium that may be used to store desired program code in the form of instructions or data structures and that may be accessed by a computer. Also, any connection is properly referred to as a computer-readable medium. For example, if the instructions are transmitted from a website, server, or other remote source using a coaxial cable, a fiber optic cable, a twisted pair, a digital subscriber line (DSL), or wireless technologies such as infrared, radio, and microwave, the coaxial cable, the fiber optic cable, the twisted pair, the DSL, or wireless technologies such as infrared, radio, and microwave are 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 transitory media, but instead cover non-transitory tangible storage media. As used herein, disk and disc include compact disc (CD), laser disc, optical disc, digital versatile disc (DVD), floppy disk and Blu-ray disc, where disks typically reproduce data magnetically and discs reproduce data optically with lasers. Combinations of the above should also be included within the scope of computer readable media.

[0249]

[0215] The 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 above structures, or any other structures suitable for implementing the techniques described herein. Furthermore, in some aspects, the functions described herein may be provided in dedicated hardware and / or software modules configured for encoding and decoding, or may be incorporated into a composite codec. Also, the techniques may be fully implemented in one or more circuits or logic elements.

[0250]

[0216] The techniques of the present disclosure may be implemented in a wide variety of devices or apparatuses, including wireless handsets, integrated circuits (ICs) or sets of ICs (e.g., chipsets). In this disclosure, various components, modules, or units have been described to highlight functional aspects of devices configured to implement the disclosed techniques, but the components, modules, or units do not necessarily require realization 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 described above, along with suitable software and / or firmware.

[0251]

[0217] Various examples have been described. These and other examples are within the scope of the following claims. The invention as described in the claims of the original application is set forth below. [C1] A device for decoding multi-layer video data, comprising: a memory configured to store multi-layer video data; one or more processors implemented in the circuit; wherein the one or more processors: maintaining a decoded picture buffer (DPB) for storing reference pictures for a plurality of layers, wherein the plurality of layers comprises at least a first layer and a second layer; performing a picture output and removal process on the DPB prior to decoding a current picture of the access unit of the first layer, wherein to perform the picture output and removal process on the DPB, the one or more processors are further configured to remove only decoded pictures belonging to the first layer from the DPB. performing a picture bumping process across all layers of the coded picture buffer (CPB) after removing the last decoded unit of the current picture from the coded picture buffer (CPB); A device configured to: [C2] The device of C1, further configured to perform the picture output and removal process on the DPB, the one or more processors performing the picture output and removal process on the DPB before decoding the current picture of the first layer and after parsing slice headers for slices of the current picture. [C3] The device of C1, further configured to perform the picture output and removal process on the DPB in response to the one or more processors removing a first decoding unit of the current picture from the CPB, to perform the picture output and removal process on the DPB. [C4] The device of C1, wherein, to perform the picture bumping process across all layers of the DPB, the one or more processors are further configured to remove reference pictures from the DPB that are marked as not required for output and that are marked as not used for reference. [C5] The device of C1, wherein the one or more processors are further configured to remove at least one picture of the second layer from the DPB to perform the picture bumping process across all layers of the DPB. [C6] The one or more processors: identifying a reference picture in the DPB; identifying a prediction block for a current block of the current picture in the reference picture; decoding the current block based on the predicted block; outputting a decoded version of the current picture, where the decoded version of the current picture includes a decoded version of the current block. The device of C1, further configured to: [C7] The device of C1, wherein the DPB is configured to store previously decoded pictures and the CPB is configured to store encoded multi-layer video data. [C8] The device of C1, wherein the one or more processors are further configured to maintain the DPB and the CPB in the memory. [C9] The device of C1, wherein the device comprises a wireless communication device further comprising a receiver configured to receive encoded multi-layer video data. [C10] The device of C9, wherein the wireless communication device comprises a telephone handset, and wherein the receiver is configured to demodulate a signal comprising the encoded multi-layer video data in accordance with a wireless communication standard. [C11] The device of C1, wherein the device comprises a wireless communication device further comprising a transmitter configured to transmit encoded multi-layer video data. [C12] The device of C11, wherein the wireless communication device comprises a telephone handset, and wherein the transmitter is configured to modulate a signal comprising the encoded multi-layer video data in accordance with a wireless communication standard. [C13] A display configured to display decoded multi-layer video data comprising a decoded version of the current picture. The device of C1, further comprising: [C14] The device of C1, wherein the device comprises one or more of a camera, a computer, a mobile device, a broadcast receiver device, or a set-top box. [C15] A method for decoding multi-layer video data, the method comprising: maintaining a decoded picture buffer (DPB) for storing reference pictures for a plurality of layers, wherein the plurality of layers comprises at least a first layer and a second layer; performing a picture output and removal process on the DPB prior to decoding a current picture of an access unit of the first layer, wherein performing the picture output and removal process on the DPB comprises removing only decoded pictures belonging to the first layer from the DPB. performing a picture bumping process across all layers of the coded picture buffer (CPB) after removing the last decoded unit of the current picture from the coded picture buffer (CPB); A method comprising: [C16] The method of C15, wherein performing the picture output and removal process on the DPB comprises performing the picture output and removal process on the DPB before decoding the current picture of the first layer and after parsing a slice header for a slice of the current picture. [C17] The method of C15, wherein performing the picture output and removal process on the DPB comprises performing the picture output and removal process on the DPB in response to removing a first decoding unit of the current picture from the CPB. [C18] performing the picture bumping process across all layers of the DPB, removing reference pictures from the DPB that are marked as not needed for output and that are marked as not used for reference; The method of claim 15, comprising: [C19] The method of C15, wherein performing the picture bumping process across all layers of the DPB comprises removing at least one picture of the second layer from the DPB. [C20] identifying a reference picture in the DPB; identifying a prediction block for a current block of the current picture in the reference picture; decoding the current block based on the predicted block; outputting a decoded version of the current picture, where the decoded version of the current picture includes a decoded version of the current block. The method of C15, further comprising: [C21] Displaying the decoded version of the current picture. The method of C20, further comprising: [C22] The method of C15, wherein the DPB is configured to store previously decoded pictures and the CPB is configured to store encoded multi-layer video data. [C23] The method of C15, wherein said method of decoding is performed as part of an encoding process. [C24] A computer-readable storage medium storing instructions that, when executed by one or more processors, cause the one or more processors to: maintaining a decoded picture buffer (DPB) for storing reference pictures for a plurality of layers, wherein the plurality of layers comprises at least a first layer and a second layer; performing a picture output and removal process on the DPB prior to decoding a current picture of an access unit of the first layer, wherein to perform the picture output and removal process on the DPB, the instructions cause the one or more processors to remove only decoded pictures belonging to the first layer from the DPB. performing a picture bumping process across all layers of the coded picture buffer (CPB) after removing the last decoded unit of the current picture from the coded picture buffer (CPB); A computer-readable storage medium for causing a computer to perform the above steps. [C25] An apparatus for decoding multi-layer video data, the apparatus comprising: means for maintaining a decoded picture buffer (DPB) for storing reference pictures for a plurality of layers, wherein the plurality of layers comprises at least a first layer and a second layer; means for performing a picture output and removal process on the DPB prior to decoding a current picture of an access unit of the first layer, wherein performing the picture output and removal process on the DPB comprises removing only decoded pictures belonging to the first layer from the DPB. means for performing a picture bumping process across all layers of a coded picture buffer (CPB) after removing the last decoded unit of the current picture from the CPB; An apparatus comprising:

Claims

1. 1. A device for decoding multi-layer video data, comprising: a memory configured to store multi-layer video data; one or more processors implemented in the circuit; wherein the one or more processors: maintaining a decoded picture buffer (DPB) for storing reference pictures for a plurality of layers, wherein the plurality of layers comprises at least a first layer and a second layer, and the DPB comprises a common DPB shared across all layers. performing a picture output and removal process on the DPB prior to decoding a current picture of the access unit of the first layer, wherein to perform the picture output and removal process on the DPB, the one or more processors are further configured to remove only decoded pictures belonging to the first layer from the DPB. performing a picture bumping process across all layers of the coded picture buffer (CPB) after removing the last decoded unit of the current picture from the coded picture buffer (CPB); A device configured to:

2. 2. The device of claim 1, further configured to: perform the picture output and removal process on the DPB, the one or more processors performing the picture output and removal process on the DPB before decoding the current picture of the first layer and after parsing slice headers for slices of the current picture.

3. 2. The device of claim 1, further configured to: perform the picture output and removal process on the DPB, in response to removing a first decoding unit of the current picture from the CPB, the one or more processors performing the picture output and removal process on the DPB.

4. 2. The device of claim 1, wherein to perform the picture bumping process across all layers of the DPB, the one or more processors are further configured to remove reference pictures from the DPB that are marked as not needed for output and that are marked as not used for reference.

5. 2. The device of claim 1, wherein the one or more processors are further configured to remove at least one picture of the second layer from the DPB to perform the picture bumping process across all layers of the DPB.

6. The one or more processors: identifying a reference picture in the DPB; identifying a prediction block for a current block of the current picture in the reference picture; decoding the current block based on the predicted block; outputting a decoded version of the current picture, where the decoded version of the current picture includes a decoded version of the current block. The device of claim 1 , further configured to:

7. 10. The device of claim 1, further comprising a wireless communication device comprising a receiver configured to receive encoded multi-layer video data, the wireless communication device preferably comprising a telephone handset, wherein the receiver is configured to demodulate a signal comprising the encoded multi-layer video data in accordance with a wireless communication standard.

8. 10. The device of claim 1, further comprising a wireless communication device comprising a transmitter configured to transmit encoded multi-layer video data, the wireless communication device preferably comprising a telephone handset, and wherein the transmitter is configured to modulate a signal comprising the encoded multi-layer video data in accordance with a wireless communication standard.

9. a display configured to display decoded multi-layer video data comprising a decoded version of the current picture. The device of claim 1 further comprising:

10. The device of claim 1 , wherein the device comprises one or more of a camera, a computer, a mobile device, a broadcast receiver device, or a set-top box.

11. 1. A method for decoding multi-layer video data, the method comprising: maintaining a decoded picture buffer (DPB) for storing reference pictures for a plurality of layers, wherein the plurality of layers comprises at least a first layer and a second layer, and the DPB comprises a common DPB shared across all layers. performing a picture output and removal process on the DPB prior to decoding a current picture of an access unit of the first layer, wherein performing the picture output and removal process on the DPB comprises removing only decoded pictures belonging to the first layer from the DPB. performing a picture bumping process across all layers of the coded picture buffer (CPB) after removing the last decoded unit of the current picture from the coded picture buffer (CPB); A method comprising:

12. performing the picture bumping process across all layers of the DPB; removing reference pictures from the DPB that are marked as not needed for output and that are marked as not used for reference; The method of claim 11 , comprising:

13. The method of claim 12 , wherein performing the picture bumping process across all layers of the DPB comprises removing at least one picture of the second layer from the DPB.

14. identifying a reference picture in the DPB; identifying a prediction block for a current block of the current picture in the reference picture; decoding the current block based on the predicted block; outputting a decoded version of the current picture, where the decoded version of the current picture includes a decoded version of the current block. The method of claim 12 further comprising:

15. 15. A computer readable storage medium storing instructions that, when executed by one or more processors, cause the one or more processors to perform a method according to any one of claims 11 to 14.

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