Encoder, decoder, and corresponding method

Abstract

To disclose a video coding mechanism.SOLUTION: The mechanism includes receiving a bit stream having a reference picture list structure having a current picture and an inter-layer reference picture flag. The mechanism determines, on the basis of the inter-layer reference picture flag, that an entry in the reference picture list structure related to the current picture is an inter-layer reference picture (ILRP) entry. The current picture is decoded on the basis of the inter-layer reference picture shown by an entry in the reference picture list structure when the entry is an ILRP entry. The current picture is transferred for display as a part of a decoding video sequence.SELECTED DRAWING: Figure 8

Description

[Technical Field]

[0002] This disclosure relates generally to video coding, and more specifically to reference picture management when employed in inter-layer prediction in video coding. [Background technology]

[0003] Even the amount of video data required to render a relatively short video can be substantial, which can pose difficulties when data is streamed or otherwise transmitted across communication networks with limited bandwidth. Therefore, video data is generally compressed before being transmitted across modern telecommunications networks. Video size can also be a concern when video is stored on storage devices, as memory resources can be limited. Video compression devices often encode video data at the source using software and / or hardware before transmission or storage, thereby reducing the amount of data required to represent the digital video image. The compressed data is then received at the destination by a video decompression device that decodes the video data. As network resources become limited and the demand for higher video quality constantly increases, improved compression and decompression techniques that improve compression ratios with little to no sacrifice in image quality are desirable. [Overview of the Initiative] [Means for solving the problem]

[0004] In one embodiment, the disclosure includes a method implemented in a decoder, the method comprising: receiving a bitstream by the decoder's receiver, the bitstream comprising a current picture and a reference picture list structure having an inter-layer reference picture flag; determining by the decoder's processor, based on the inter-layer reference picture flag, that an entry in the reference picture list structure related to the current picture is an inter-layer reference picture (ILRP) entry; and, if the entry is an ILRP entry, decoding the current picture by the processor based on the inter-layer reference picture indicated by the entry in the reference picture list structure.

[0005] A video coding system may encode a picture according to interpretation. In interpretation, a picture is coded by referencing another picture. The picture being coded is called the current picture, and the picture used as a reference is called the reference picture. Some video coding systems track reference pictures by employing a reference picture list. Some video coding systems employ scalable video coding. In scalable video coding, a video sequence is coded as a base layer and one or more enhancement layers. In this context, a picture may be divided into parts that reside in different layers. For example, a lower layer version of a picture may be of lower quality than a higher layer version of the picture. Furthermore, a lower layer version of a picture may be smaller than a higher layer version of the picture (for example, it may have a smaller width and / or height). When using layers, a picture in the current layer may be coded according to intrapretation (without using a reference picture), according to interpretation by referencing a reference picture in the same layer, or according to interlayer prediction by referencing a reference picture in a different layer. Some reference picture management systems may not be configured to manage reference pictures used in inter-layer prediction. This example includes a mechanism for managing a reference picture list when employing inter-layer prediction. The reference picture list may be configured to contain an entry for each reference picture used by the coded video. A flag may then be used to indicate whether each entry contains an inter-prediction reference picture or an inter-layer reference picture. In one example, a group of reference picture flags for a syntax structure containing the reference picture list may be represented as inter_layer_ref_pic_flag[ listIdx ][ rplsIdx ][ i ]. Furthermore, an ILRP layer indicator may be used to indicate which layer contains the indicated inter-layer reference picture.The decoder can then use the reference picture flag and the ILRP layer indicator to select the appropriate inter-layer reference picture in order to perform inter-layer prediction. Thus, the disclosed mechanism creates additional functionality in the encoder and / or decoder. Furthermore, the disclosed mechanism may improve coding efficiency, which may reduce the processor, memory, and / or network resource usage in the encoder and / or decoder.

[0006] Optionally, in any of the embodiments described above, another implementation of the embodiment provides that the reference picture list structure further comprises an ILRP layer indicator, and the method further comprises the step of the processor determining the layer of the interlayer reference picture based on the ILRP layer indicator when the entry is an ILRP entry.

[0007] Optionally, in any of the embodiments described above, another implementation of the embodiment provides that the reference picture list structure is represented as ref_pic_list_struct( listIdx, rplsIdx ), where listIdx identifies the reference picture list, rplsIdx identifies an entry in the reference picture list, and ref_pic_list_struct is the syntax structure.

[0008] Optionally, in any of the aforementioned embodiments, another implementation of the embodiment provides that the inter-layer reference picture flag is represented as inter_layer_ref_pic_flag[ listIdx ][ rplsIdx ][ i ], where inter_layer_ref_pic_flag[ listIdx ][ rplsIdx ][ i ] is equal to 1 when the i-th entry in ref_pic_list_struct( listIdx, rplsIdx ) is an ILRP entry, and inter_layer_ref_pic_flag[ listIdx ][ rplsIdx ][ i ] is equal to 0 when the i-th entry in ref_pic_list_struct( listIdx, rplsIdx ) is not an ILRP entry.

[0009] Optionally, in any of the embodiments described above, another implementation of the embodiment further provides that, when the entry is not an ILRP entry, the processor decodes the current picture according to an in-layer prediction based on the in-layer reference picture indicated by the entry in the reference picture list structure.

[0010] Optionally, in any of the aforementioned embodiments, another implementation of the embodiment provides that ref_pic_list_struct( listIdx, rplsIdx ) and inter_layer_ref_pic_flag[ listIdx ][ rplsIdx ][ i ] are included in the bitstream within the sequence parameter set (SPS).

[0011] Optionally, in any of the aforementioned embodiments, another implementation of the embodiment provides that the interlayer reference picture is in the same access unit (AU) as the current picture, and that the interlayer reference picture is associated with a lower layer identifier than the current picture.

[0012] In one embodiment, the disclosure includes a method implemented in an encoder, the method comprising: encoding a current picture into a bitstream by the encoder's processor, wherein the current picture is encoded according to an inter-layer prediction based on an inter-layer reference picture; encoding a reference picture list structure into a bitstream by the processor, wherein the reference picture list structure comprises a plurality of entries for a plurality of reference pictures, including an entry related to the current picture, and indicating an inter-layer reference picture; encoding an inter-layer reference picture flag into a bitstream by the processor, wherein the inter-layer reference picture flag indicates that the entry related to the current picture is an ILRP entry; and storing the bitstream in a memory coupled to the processor for communication toward a decoder.

[0013] A video coding system may encode a picture according to interpretation. In interpretation, a picture is coded by referencing another picture. The picture being coded is called the current picture, and the picture used as a reference is called the reference picture. Some video coding systems track reference pictures by employing a reference picture list. Some video coding systems employ scalable video coding. In scalable video coding, a video sequence is coded as a base layer and one or more enhancement layers. In this context, a picture may be divided into parts that reside in different layers. For example, a lower layer version of a picture may be of lower quality than a higher layer version of the picture. Furthermore, a lower layer version of a picture may be smaller than a higher layer version of the picture (for example, it may have a smaller width and / or height). When using layers, a picture in the current layer may be coded according to intrapretation (without using a reference picture), according to interpretation by referencing a reference picture in the same layer, or according to interlayer prediction by referencing a reference picture in a different layer. Some reference picture management systems may not be configured to manage reference pictures used in inter-layer prediction. This example includes a mechanism for managing a reference picture list when employing inter-layer prediction. The reference picture list may be configured to contain an entry for each reference picture used by the coded video. A flag may then be used to indicate whether each entry contains an inter-prediction reference picture or an inter-layer reference picture. In one example, a group of reference picture flags for a syntax structure containing the reference picture list may be represented as inter_layer_ref_pic_flag[ listIdx ][ rplsIdx ][ i ]. Furthermore, an ILRP layer indicator may be used to indicate which layer contains the indicated inter-layer reference picture.The decoder can then use the reference picture flag and the ILRP layer indicator to select the appropriate inter-layer reference picture in order to perform inter-layer prediction. Thus, the disclosed mechanism creates additional functionality in the encoder and / or decoder. Furthermore, the disclosed mechanism may improve coding efficiency, which may reduce the processor, memory, and / or network resource usage in the encoder and / or decoder.

[0014] Optionally, in any of the embodiments described above, another implementation of the embodiment further comprises encoding an ILRP layer indicator in a bitstream by the processor, where the ILRP layer indicator indicates the layer of the interlayer reference picture.

[0015] Optionally, in any of the embodiments described above, another implementation of the embodiment provides that the reference picture list structure is represented as ref_pic_list_struct( listIdx, rplsIdx ), where listIdx identifies the reference picture list and rplsIdx identifies an entry in the reference picture list, and ref_pic_list_struct is a syntactic structure that returns an entry based on listIdx and rplsIdx.

[0016] Optionally, in any of the aforementioned embodiments, another implementation of the embodiment provides that the inter-layer reference picture flag is represented as inter_layer_ref_pic_flag[ listIdx ][ rplsIdx ][ i ], where inter_layer_ref_pic_flag[ listIdx ][ rplsIdx ][ i ] is equal to 1 when the i-th entry in ref_pic_list_struct( listIdx, rplsIdx ) is an ILRP entry, and inter_layer_ref_pic_flag[ listIdx ][ rplsIdx ][ i ] is equal to 0 when the i-th entry in ref_pic_list_struct( listIdx, rplsIdx ) is not an ILRP entry.

[0017] Optionally, in any of the aforementioned embodiments, another implementation of the embodiment provides that ref_pic_list_struct( listIdx, rplsIdx ) and inter_layer_ref_pic_flag[ listIdx ][ rplsIdx ][ i ] are encoded in the bitstream within the SPS.

[0018] Optionally, in any of the aforementioned embodiments, another implementation of the embodiment provides that ref_pic_list_struct( listIdx, rplsIdx ) and inter_layer_ref_pic_flag[ listIdx ][ rplsIdx ][ i ] are encoded in the header currently associated with the picture.

[0019] Optionally, in any of the aforementioned embodiments, another implementation of the embodiment provides that the interlayer reference picture is in the same AU as the current picture, and the interlayer reference picture is associated with a lower layer identifier than the current picture.

[0020] In one embodiment, the disclosure includes a video coding device comprising a processor, a receiver coupled to the processor, a memory coupled to the processor, and a transmitter coupled to the processor, wherein the processor, receiver, memory, and transmitter are configured to perform any of the methods described above.

[0021] In one embodiment, the disclosure includes a non-temporary computer-readable medium comprising a computer program product for use by a video coding device, wherein the computer program product comprises computer-executable instructions stored on the non-temporary computer-readable medium that, when executed by a processor, cause the video coding device to perform any of the methods described above.

[0022] In one embodiment, the disclosure includes a decoder comprising: receiving means for receiving a bitstream comprising a current picture, a reference picture list structure, and an inter-layer reference picture flag; determining means for determining, based on the inter-layer reference picture flag, whether an entry in the reference picture list structure related to the current picture is an ILRP entry; decoding means for decoding the current picture according to an inter-layer prediction based on the inter-layer reference picture indicated by the entry in the reference picture list structure when the entry is an ILRP entry; and transferring means for transferring the current picture for display as part of a decoded video sequence.

[0023] Optionally, in any of the embodiments described above, another implementation of the embodiment provides that the decoder is further configured to perform any of the methods described above.

[0024] In one embodiment, the present disclosure is to encode a current picture into a bitstream, wherein the current picture is encoded according to inter-layer prediction based on an inter-layer reference picture, and to encode a reference picture list structure into the bitstream, wherein the reference picture list structure comprises a plurality of entries for a plurality of reference pictures including entries related to the current picture and indicates an inter-layer reference picture, and to encode an inter-layer reference picture flag into the bitstream, wherein the inter-layer reference picture flag indicates that an entry related to the current picture is an ILRP entry, and an encoding means for performing the encoding, and a storage means for storing the bitstream for communication to a decoder, including an encoder.

[0025] Optionally, in any of the foregoing aspects, another implementation of the aspect provides that the encoder is further configured to execute any of the methods of the foregoing aspects.

[0026] For clarity, any one of the above embodiments may be combined with any one or more of the other above embodiments to create a new embodiment within the scope of the present disclosure.

[0027] These and other features will be more clearly understood from the following forms for carrying out the invention, to be understood together with the accompanying drawings and the claims.

[0028] For a more complete understanding of the present disclosure, reference is now made to the following brief description, to be understood in connection with the accompanying drawings and forms for carrying out the invention, in which like reference numerals represent like parts.

Brief Description of the Drawings

[0029] [Figure 1] It is a flowchart of an exemplary method for coding a video signal. [Figure 2]This is a schematic diagram illustrating an exemplary coding and decoding (codec) system for video coding. [Figure 3] This is a schematic diagram illustrating an example video encoder. [Figure 4] This is a schematic diagram illustrating an exemplary video decoder. [Figure 5] This is a schematic diagram showing an example of unidirectional interpretation. [Figure 6] This is a schematic diagram showing an example of bidirectional interface prediction. [Figure 7] This is a schematic diagram illustrating an example of layer-based prediction. [Figure 8] This is a schematic diagram illustrating an exemplary reference picture list structure. [Figure 9] This is a schematic diagram showing an exemplary bitstream including coding tool parameters to support inter-layer prediction. [Figure 10] This is a schematic diagram of an exemplary video coding device. [Figure 11] This is a flowchart illustrating an exemplary method for encoding a video sequence into a bitstream according to inter-layer prediction. [Figure 12] This is a flowchart illustrating an exemplary method for decoding a video sequence from a bitstream when employing interlayer prediction. [Figure 13] This is a schematic diagram of an exemplary system for coding a video sequence of images in a bitstream when employing interlayer prediction. [Modes for carrying out the invention]

[0030] While exemplary implementations of one or more embodiments are provided below, it should be understood from the outset that the disclosed systems and / or methods may be carried out using any number of techniques, whether currently known or existing. This disclosure should not be limited in any way to the exemplary implementations, drawings, and techniques illustrated below, including the exemplary designs and implementations illustrated and described herein, and may be modified in the appended claims together with the full range of their equivalents.

[0031] The following terms are defined as such unless used in the opposite context within this specification. In particular, the following definitions are intended to provide additional clarity to this disclosure. However, terms may be described differently in different contexts. Therefore, the following definitions should be considered supplementary and should not be considered to limit any other definitions of such terms given herein.

[0032] A bitstream is a sequence of bits containing video data that is compressed for transmission between an encoder and a decoder. An encoder is a device configured to employ an encoding process to compress video data into a bitstream. A decoder is a device configured to employ a decoding process to reconstruct video data from the bitstream for display. A picture is an array of lumen samples and / or chroma samples that make up a frame or a field of a frame. For clarity of explanation, a picture being encoded or decoded can now be called a picture. A reference picture is a picture containing reference samples that may be used when coding other pictures by reference through inter-prediction and / or inter-layer prediction. A reference picture list is a list of reference pictures used for inter-prediction and / or inter-layer prediction. Some video coding systems refer to two picture lists, which may be indicated as reference picture list 1 and reference picture list 0. A reference picture list structure is an addressable syntax structure that contains multiple reference picture lists. A layer is a group of pictures all related by similar values ​​such as similar size, quality, resolution, signal-to-noise ratio, and capability. A layer identifier (ID) is a data item that is associated with a picture and indicates that the picture is part of the layer it is shown in. Interpretation is a mechanism for coding samples in the current picture by referencing samples in a reference picture that is different from the current picture, although the reference picture and the current picture are in the same layer. In an inter-layer context, since both the current picture and the reference picture are in the same layer, interpretation can also be called intra-layer prediction. Inter-layer prediction is a mechanism for coding samples in the current picture by referencing samples in a reference picture, although the current picture and the reference picture are in different layers and therefore have different layer IDs. An inter-layer reference picture is a reference picture used for inter-layer prediction.Some video coding systems may require that the current picture and its associated inter-layer reference pictures be contained within the same Access Unit (AU). A reference picture list structure entry is an addressable location within the reference picture list structure that indicates a reference picture associated with the reference picture list. An inter-layer reference picture (ILRP) entry is an entry containing a reference picture used for inter-layer prediction. An inter-layer reference picture flag is data indicating that a reference picture in an entry of the reference picture list structure is an inter-layer reference picture. An ILRP layer indicator is data indicating the layer associated with the inter-layer reference picture referenced by the current picture. A slice header is part of a coded slice that contains data elements relating to all video data within the tiles represented in the slice. A sequence parameter set (SPS) is a set of parameters containing data relating to the sequence of pictures. An AU is a set of one or more coded pictures associated with the same display time (e.g., the same picture sequence count) for output from a decoded picture buffer (DPB) (e.g., for display to the user). A decoded video sequence is a sequence of pictures that is being reconstructed by a decoder in preparation for display to the user.

[0033] In this specification, the following acronyms are used: Coding Tree Block (CTB), Coding Tree Unit (CTU), Coding Unit (CU), Coded Video Sequence (CVS), Decoded Picture Buffer (DPB), Joint Video Experts Team (JVET), Motion-Constrained Tile Set (MCTS), Maximum Transfer Unit (MTU), Network Abstraction Layer (NAL), Picture Order Count (POC), Random Access Decodable Leading (RADL) picture, Random Access Skipped Leading (RASL) picture, Raw Byte Sequence Payload (RBSP), Reference Picture List (RPL), Sequence Parameter Set (SPS), and Video Coding Layer (VCL). Layers, Versatile Video Coding (VVC), and Working Drafts (WD) are used.

[0034] Many video compression techniques can be employed to reduce the size of video files with minimal data loss. For example, video compression techniques may include performing spatial (e.g., within a picture) prediction and / or temporal (e.g., between pictures) prediction to reduce or eliminate data redundancy in a video sequence. In block-based video coding, a video slice (e.g., a video picture or a portion of a video picture) may be divided into video blocks, which may also be called tree blocks, coding tree blocks (CTBs), coding tree units (CTUs), coding units (CUs), and / or coding nodes. Video blocks in an intra-coding (I) slice of a picture are coded using spatial prediction for reference samples in adjacent blocks within the same picture. Video blocks in an intercoding (P) or bidirectional prediction (B) slice of a picture may be coded by employing spatial prediction for reference samples in adjacent blocks within the same picture, or temporal prediction for reference samples in other reference pictures. Pictures may be called frames and / or images, and reference pictures may be called reference frames and / or reference images. Spatial or temporal prediction yields predicted blocks representing image blocks. Residual data represents the pixel difference between the original image blocks and the predicted blocks. Thus, intercoded blocks are encoded according to motion vectors pointing to the reference sample blocks forming the predicted blocks, and residual data showing the difference between the coded blocks and the predicted blocks. Intracoded blocks are encoded according to the intracoding mode and residual data. For further compression, residual data can be transformed from pixel regions to transformation regions. These yield residual transformation coefficients, which can be quantized. The quantized transformation coefficients may initially be arranged as a two-dimensional array. The quantized transformation coefficients can be scanned to generate a one-dimensional vector of transformation coefficients. Entropy coding may be applied to achieve further compression.Such video compression techniques are explained in more detail below.

[0035] To ensure that encoded video can be accurately decoded, video is encoded and decoded according to the corresponding video coding standard. Video coding standards include Advanced Video Coding (AVC), also known as ITU-T H.261, ITU-T H.262 or ISO / IEC MPEG-2 Part 2, ITU-T H.263, ISO / IEC MPEG-4 Part 2, ITU-T H.264 or ISO / IEC MPEG-4 Part 10, and High Efficiency Video Coding (HEVC), also known as ITU-T H.265 or MPEG-H Part 2. AVC includes extensions such as Scalable Video Coding (SVC), Multiview Video Coding (MVC), Multiview Video Coding Plus Depth (MVC+D), and Three-Dimensional (3D) AVC (3D-AVC). HEVC includes extensions such as Scalable HEVC (SHVC), Multiview HEVC (MV-HEVC), and 3D HEVC (3D-HEVC). The ITU-T and ISO / IEC Joint Video Expert Team (JVET) has begun developing a video coding standard called Multipurpose Video Coding (VVC). VVC is included in working drafts (WDs), including JVET-N1001-v6.

[0036] A video coding system may encode a picture according to interpretation. In interpretation, a picture is coded by reference to another picture. The picture being coded is called the current picture, and the picture used as a reference is called the reference picture. Some video coding systems track reference pictures by employing a reference picture list. In addition, some video coding systems employ scalable video coding. In scalable video coding, a video sequence is coded as a base layer and one or more enhancement layers. In this context, a picture may be divided into multiple pictures residing in different layers. For example, a lower layer version of a picture may be of lower quality than a higher layer version of the picture. Furthermore, a lower layer version of a picture may be smaller than a higher layer version of the picture (for example, it may have a smaller width and / or height). When using layers, a picture in the current layer may be coded according to intrapretation (without reference pictures), according to interpretation by reference to reference pictures in the same layer, or according to interlayer prediction by reference to reference pictures in different layers. However, reference picture lists are not always designed to describe reference pictures across multiple layers.

[0037] An exemplary mechanism for managing a reference picture list when employing inter-layer prediction is disclosed herein. For example, the reference picture list may be configured to contain an entry for each reference picture used by the coded video. A flag may then be employed to indicate whether each entry contains an inter-prediction reference picture (for references within the same level) or an inter-layer reference picture (for references between layers). In one example, a group of reference picture flags for a syntax structure containing a reference picture list may be represented as inter_layer_ref_pic_flag[ listIdx ][ rplsIdx ][ i ]. The inter_layer_ref_pic_flag[ listIdx ][ rplsIdx ][ i ] flag may be set to equal to 1 when the i-th entry in the reference picture structure is an ILRP entry, or to 0 when the i-th entry in the reference picture structure is not an ILRP entry. Furthermore, an ILRP layer indicator may be used to indicate which layer contains the inter-layer reference picture indicated by the entry in the reference picture structure. The decoder can then use the reference picture flag and the ILRP layer indicator to select the appropriate inter-layer reference picture in order to perform inter-layer prediction. Thus, the disclosed mechanism creates additional functionality in the encoder and / or decoder. Moreover, the disclosed mechanism may improve coding efficiency, which may reduce processor, memory, and / or network resource usage in the encoder and / or decoder.

[0038] Figure 1 is a flowchart of an exemplary operating method 100 for coding a video signal. Specifically, the video signal is encoded in an encoder. The encoding process compresses the video signal by employing various mechanisms to reduce the video file size. A smaller file size allows the compressed video file to be transmitted to the user while reducing the associated bandwidth overhead. The decoder then decodes the compressed video file to reconstruct the original video signal for display to the end user. The decoding process generally closely mimics the encoding process, allowing the decoder to reconstruct the video signal without inconsistency.

[0039] In step 101, a video signal is input into the encoder. For example, the video signal may be an uncompressed video file stored in memory. As another example, the video file may be captured by a video capture device such as a video camera and may be encoded to support live streaming of the video. The video file may contain both audio and video components. The video component includes a series of image frames that, when viewed in sequence, give a visual impression of motion. Each frame contains pixels, which are expressed herein with respect to light, called the lumen component (or lumen sample), and color, called the chromen component (or color sample). In some examples, the frames may also include depth values ​​to support three-dimensional display.

[0040] In step 103, the video is divided into blocks. Dividing involves subdividing the pixels within each frame into square and / or rectangular blocks for compression. For example, in High Efficiency Video Coding (HEVC) (also known as H.265 and MPEG-H Part 2), a frame may first be divided into coding tree units (CTUs), which are blocks of a predetermined size (e.g., 64 pixels × 64 pixels). A CTU contains both lumen and chroma samples. A coding tree may be employed to divide the CTU into blocks, and then recursively subdivide the blocks until a configuration supporting further encoding is obtained. For example, the lumen component of a frame may be subdivided until the individual blocks contain relatively uniform illumination values. Furthermore, the chroma component of a frame may be subdivided until the individual blocks contain relatively uniform color values. Thus, the division mechanism varies depending on the content of the video frame.

[0041] In step 105, various compression mechanisms are employed to compress the image blocks segmented in step 103. For example, interpretation and / or intrapretation may be employed. Interpretation is designed to take advantage of the fact that objects in a common scene tend to appear in consecutive frames. Therefore, blocks representing objects in a reference frame do not need to be described repeatedly in adjacent frames. In particular, objects such as tables may remain in the same position across multiple frames. Therefore, a table is described once, and adjacent frames can work backward to refer to the reference frame. Pattern matching mechanisms may be employed to align objects across multiple frames. Furthermore, moving objects may be represented across multiple frames, for example, due to object movement or camera movement. As a concrete example, a video may show a car moving across the screen across multiple frames. Motion vectors may be employed to describe such movement. A motion vector is a two-dimensional vector that provides an offset from the coordinates of an object in one frame to the coordinates of an object in a reference frame. Therefore, interpretation can encode the image blocks in the current frame as a set of motion vectors indicating the offset from the corresponding block in the reference frame.

[0042] Intra-prediction encodes blocks within a common frame. It leverages the fact that lumen and chroma components tend to cluster within a frame. For example, a green fragment within a tree tends to be placed adjacent to similar green fragments. Intra-prediction employs multiple directional prediction modes (e.g., 33 in HEVC), planar mode, and DC mode. Directional modes indicate that a current block is similar / identical to samples of adjacent blocks in the corresponding direction. Planar modes indicate that a sequence of blocks along a row / column (e.g., a plane) can be interpolated at the row edges based on adjacent blocks. Planar modes effectively represent smooth light / color transitions across rows / columns by employing a relatively constant gradient as values ​​change. DC mode is employed for boundary smoothing and indicates that a block is similar / identical to the mean value associated with all adjacent block samples related to the angular direction of the directional prediction mode. Thus, intra-predicted blocks can represent image blocks not as actual values, but as various relevant prediction mode values. Furthermore, the interpretation block can represent the image block as a motion vector value rather than its actual value. In either case, the prediction block may not strictly represent the image block in some cases. Any differences are stored in the residual block. Transformations may be applied to the residual block to further compress the file.

[0043] In step 107, various filtering techniques may be applied. In HEVC, filters are applied according to an in-loop filtering scheme. The block-based prediction described above may result in blocky images in the decoder. Furthermore, the block-based prediction scheme may encode blocks and then reconstruct the encoded blocks for later use as reference blocks. The in-loop filtering scheme iteratively applies noise suppression filters, deblocking filters, adaptive loop filters, and sample adaptive offset (SAO) filters to blocks / frames. These filters mitigate such blocking artifacts so that the encoded file can be accurately reconstructed. Furthermore, these filters mitigate artifacts in the reconstructed reference block so that artifacts are less likely to generate additional artifacts in subsequent blocks encoded based on the reconstructed reference block.

[0044] Once the video signal has been segmented, compressed, and filtered, in step 109 the resulting data is encoded in a bitstream. The bitstream contains the data described above, as well as any signaling data desired to support proper video signal reconstruction in the decoder. For example, such data may include segmented data, prediction data, residual blocks, and various flags that provide coding instructions to the decoder. The bitstream may be stored in memory for transmission to the decoder upon request. The bitstream may also be broadcast and / or multicast to multiple decoders. The creation of the bitstream is an iterative process. Therefore, steps 101, 103, 105, 107, and 109 may be performed continuously and / or simultaneously over many frames and blocks. The order shown in Figure 1 is presented for clarity and simplicity of explanation and is not intended to limit the video coding process to a specific order.

[0045] The decoder receives the bitstream in step 111 and begins the decoding process. Specifically, the decoder employs an entropy decoding scheme to convert the bitstream into corresponding syntax and video data. In step 111, the decoder employs syntax data from the bitstream to determine the divisions for the frame. The divisions should be consistent with the result of the block division in step 103. The entropy coding / decoding employed in step 111 is described below. The encoder makes many choices during the compression process, such as selecting a block division scheme from several possible options based on the spatial arrangement of values ​​in the input image. Signaling a strict choice may involve employing a number of bins. As used herein, a bin is a binary value (e.g., a bit value that may change depending on the context) treated as a variable. Entropy coding allows the encoder to discard any option that is clearly not viable for a particular case, leaving a set of acceptable options. Each acceptable option is then assigned a codeword. The length of the codeword is based on the number of acceptable options (e.g., one bin for two options, two bins for three or four options, etc.). The encoder then encodes the codeword for the selected option. This scheme reduces the size of the codeword when it is large enough to uniquely represent a choice from a small subset of acceptable options, as opposed to uniquely representing a choice from a potentially large set of all possible options. The decoder then decodes the choice by determining the set of acceptable options in a similar manner to the encoder. By determining the set of acceptable options, the decoder can read the codeword and determine the selection made by the encoder.

[0046] In step 113, the decoder performs block decoding. Specifically, the decoder employs an inverse transform to generate residual blocks. The decoder then employs the residual blocks and corresponding prediction blocks to reconstruct the image blocks according to the partitions. The prediction blocks may include both intra-prediction blocks and inter-prediction blocks, as generated in the encoder in step 105. The reconstructed image blocks are then placed in the frames of the reconstructed video signal according to the partition data determined in step 111. The syntax for step 113 may also be signaled in the bitstream via entropy coding as described above.

[0047] In step 115, filtering is performed on the frames of the reconstructed video signal in a manner similar to that in step 107 in the encoder. For example, noise suppression filters, deblocking filters, adaptive loop filters, and SAO filters may be applied to the frames to remove blocking artifacts. Once the frames have been filtered, the video signal may be output to a display in step 117 for viewing by the end user.

[0048] Figure 2 is a schematic diagram of an exemplary coding and decoding (codec) system 200 for video coding. Specifically, the codec system 200 provides functionality to support implementations of the operation method 100. The codec system 200 is generalized to show the components employed in both the encoder and the decoder. The codec system 200 receives and segments the video signal as described with respect to steps 101 and 103 in the operation method 100, which results in the segmented video signal 201. The codec system 200 then compresses the segmented video signal 201 into an encoded bitstream when acting as an encoder, as described with respect to steps 105, 107, and 109 in the method 100. When acting as a decoder, the codec system 200 generates an output video signal from the bitstream, as described with respect to steps 111, 113, 115, and 117 in the operation method 100. The codec system 200 includes a general-purpose coder control component 211, a transform scaling and quantization component 213, an in-picture estimation component 215, an in-picture prediction component 217, a motion compensation component 219, a motion estimation component 221, a scaling and inverse transform component 229, a filter-controlled analysis component 227, an in-loop filter component 225, a decoded picture buffer component 223, and a header formatting and context-adaptive binary arithmetic coding (CABAC) component 231. Such components are combined as shown in the figure. In Figure 2, black lines indicate the movement of data to be encoded / decoded, and dashed lines indicate the movement of control data that controls the operation of other components. All components of the codec system 200 may reside in the encoder. The decoder may include a subset of the components of the codec system 200. For example, the decoder may include the in-picture prediction component 217, the motion compensation component 219, the scaling and inverse transform component 229, the in-loop filter component 225, and the decoded picture buffer component 223. These components will be explained next.

[0049] The segmented video signal 201 is a captured video sequence segmented into blocks of pixels by a coding tree. The coding tree employs various segmentation modes to subdivide blocks of pixels into smaller blocks. These blocks can then be subdivided into even smaller blocks. Blocks are sometimes called nodes in the coding tree. Larger parent nodes are subdivided into smaller child nodes. The number of times a node is subdivided is called the node / coding tree depth. The segmented blocks may, in some cases, be contained within a coding unit (CU). For example, a CU may be a sub-part of a CTU, including a lumen block, a red difference chroma (Cr) block, and a blue difference chroma (Cb) block, along with the corresponding syntax instructions for the CU. The segmentation modes may include binary trees (BT), triple trees (TT), and quad trees (QT), each with a shape that varies depending on the segmentation mode adopted, used to segment a node into two, three, or four child nodes, respectively. The segmented video signal 201 is transferred to a general-purpose coder control component 211, a transformation scaling and quantization component 213, an in-picture estimation component 215, a filter control analysis component 227, and a motion estimation component 221 for compression.

[0050] The general-purpose coder control component 211 is configured to make decisions related to coding images of a video sequence into a bitstream, according to applicable constraints. For example, the general-purpose coder control component 211 manages the optimization of bitrate / bitstream size versus reconstruction quality. Such decisions may be based on memory space / bandwidth availability and image resolution requirements. The general-purpose coder control component 211 also manages buffer utilization in relation to the transmission rate to mitigate buffer underrun and overrun problems. To manage these problems, the general-purpose coder control component 211 manages segmentation, prediction, and filtering by other components. For example, the general-purpose coder control component 211 may dynamically increase the compression computation to increase resolution and bandwidth usage, or decrease the compression computation to decrease resolution and bandwidth usage. Thus, the general-purpose coder control component 211 controls other components of the codec system 200 to harmonize video signal reconstruction quality with bitrate importance. The general-purpose coder control component 211 generates control data that controls the operation of other components. The control data is also encoded within the bitstream and transferred to the header formatting and CABAC component 231 to signal parameters for decoding in the decoder.

[0051] The segmented video signal 201 is also sent to the motion estimation component 221 and the motion compensation component 219 for interpretation. A frame or slice of the segmented video signal 201 may be divided into multiple video blocks. The motion estimation component 221 and the motion compensation component 219 perform interpretation coding of the received video blocks for one or more blocks in one or more reference frames in order to perform time prediction. The codec system 200 may perform multiple coding passes, for example, to select an appropriate coding mode for each block of video data.

[0052] The motion estimation component 221 and the motion compensation component 219 may be highly integrated, but are illustrated separately for conceptual purposes. The motion estimation performed by the motion estimation component 221 is the process of generating motion vectors that estimate motion for a video block. The motion vectors may, for example, represent the displacement of a coded object relative to a predicted block. A predicted block is a block that is recognized as closely aligned with the block to be coded in terms of pixel differences. Predicted blocks are sometimes called reference blocks. Such pixel differences may be determined by the sum of absolute difference (SAD), the sum of square difference (SSD), or other difference metrics. HEVC employs several coded objects, including CTUs, coding tree blocks (CTBs), and CUs. For example, a CTU may be split into CTBs, which may then be split into CBs to be contained within the CUs. A CU may be coded as a prediction unit (PU) containing prediction data, and / or a transform unit (TU) containing transformed residual data for the CUs. The motion estimation component 221 generates motion vectors, PUs, and TUs by using rate-distortion analysis as part of the rate-distortion optimization process. For example, the motion estimation component 221 may determine multiple reference blocks, multiple motion vectors, etc. for the current block / frame and select the reference blocks, motion vectors, etc. that have the best rate-distortion characteristics. The best rate-distortion characteristics harmonize both the quality of the video reconstruction (e.g., the amount of data loss due to compression) with the coding efficiency (e.g., the size of the final encoding).

[0053] In some examples, the codec system 200 may calculate values ​​for sub-integer pixel positions of the reference picture stored in the decoded picture buffer component 223. For example, the video codec system 200 may interpolate values ​​for quarter-pixel, eighth-pixel, or other fractional-pixel positions of the reference picture. Thus, the motion estimation component 221 may perform motion search on full-pixel and fractional-pixel positions and output motion vectors with fractional-pixel precision. The motion estimation component 221 calculates motion vectors for the PU of video blocks in the intercoded slice by comparing the PU positions with the predicted block positions of the reference picture. The motion estimation component 221 outputs the calculated motion vectors as motion data for encoding to the header formatting and CABAC component 231 and to the motion compensation component 219.

[0054] Motion compensation performed by the motion compensation component 219 may involve fetching or generating a predicted block based on a motion vector determined by the motion estimation component 221. Again, in some examples, the motion estimation component 221 and the motion compensation component 219 may be functionally integrated. Upon receiving the motion vector for the PU of the current video block, the motion compensation component 219 may determine the position of the predicted block pointed to by the motion vector. A residual video block is then formed by subtracting the pixel values ​​of the predicted block from the coded pixel values ​​of the current video block, thereby forming the pixel difference values. Generally, the motion estimation component 221 performs motion estimation with respect to the lumen component, and the motion compensation component 219 uses a motion vector calculated based on the lumen component for both the chromen and lumen components. The predicted and residual blocks are then transferred to the transformation scaling and quantization component 213.

[0055] The segmented video signal 201 is also sent to the in-picture estimation component 215 and the in-picture prediction component 217. Similar to the motion estimation component 221 and the motion compensation component 219, the in-picture estimation component 215 and the in-picture prediction component 217 may be highly integrated, but are illustrated separately for conceptual purposes. The in-picture estimation component 215 and the in-picture prediction component 217 intra-predict the current block for a block in the current frame, as an alternative to the inter-prediction performed by the motion estimation component 221 and the motion compensation component 219 between frames, as described above. Specifically, the in-picture estimation component 215 determines the intra-prediction mode to be used to encode the current block. In some examples, the in-picture estimation component 215 selects an appropriate intra-prediction mode for encoding the current block from several tested intra-prediction modes. The selected intra-prediction mode is then forwarded to the header formatting and CABAC component 231 for encoding.

[0056] For example, the in-picture estimation component 215 calculates rate distortion values ​​for various intra-prediction modes tested using rate-distortion analysis and selects the intra-prediction mode with the best rate-distortion characteristics among the tested modes. Rate-distortion analysis generally determines the amount of distortion (i.e., error) between the encoded block and the original, unencoded block encoded to generate the encoded block, as well as the bit rate (e.g., number of bits) used to generate the encoded block. The in-picture estimation component 215 calculates a ratio from the distortion and rate for various encoded blocks to determine which intra-prediction mode exhibits the best rate-distortion value for the block. In addition, the in-picture estimation component 215 may be configured to code depth blocks of the depth map using a depth modeling mode (DMM) based on rate-distortion optimization (RDO).

[0057] When implemented on an encoder, the in-picture prediction component 217 may generate residual blocks from prediction blocks based on a selected intra-prediction mode determined by the in-picture estimation component 215, or when implemented on a decoder, it may read residual blocks from a bitstream. The residual blocks contain the difference in values ​​between the prediction blocks and the original blocks, represented as a matrix. The residual blocks are then transferred to the transformation scaling and quantization component 213. The in-picture estimation component 215 and the in-picture prediction component 217 may operate on both lumen and chroma components.

[0058] The transform scaling and quantization component 213 is configured to further compress the residual block. The transform scaling and quantization component 213 applies a transform, such as a discrete cosine transform (DCT), discrete sine transform (DST), or a conceptually similar transform, to the residual block to generate a video block with residual transform coefficient values. Wavelet transforms, integer transforms, subband transforms, or other types of transforms may also be used. The transform may convert the residual information from the pixel value domain to a transformation domain such as the frequency domain. The transform scaling and quantization component 213 is also configured to scale the transformed residual information, for example, based on frequency. Such scaling involves applying a scale coefficient to the residual information, resulting in different frequency information being quantized at different granularities, which may affect the final visual quality of the reconstructed video. The transform scaling and quantization component 213 is also configured to quantize the transform coefficients to further reduce the bitrate. The quantization process may reduce the bit depth associated with some or all of the coefficients. The degree of quantization may be modified by adjusting the quantization parameters. In some examples, the transformation scaling and quantization component 213 may then perform a scan of a matrix containing the quantization transformation coefficients. The quantization transformation coefficients are then transferred to the header formatting and CABAC component 231 and encoded in the bitstream.

[0059] The scaling and inverse transform component 229 applies the inverse operation of the transform scaling and quantization component 213 to support motion estimation. The scaling and inverse transform component 229 applies inverse scaling, transform, and / or quantization to reconstruct the residual block in the pixel region for later use as a reference block that may become a predicted block for another current block, for example. The motion estimation component 221 and / or motion compensation component 219 may compute the reference block by returning the residual block to the corresponding predicted block and adding it for use in motion estimation of a later block / frame. A filter is applied to the reconstructed reference block to mitigate artifacts that occur during scaling, quantization, and transform. Such artifacts may, in some cases, cause inaccurate predictions (and generate additional artifacts) when subsequent blocks are predicted.

[0060] The filter-controlled analysis component 227 and the in-loop filter component 225 apply filters to residual blocks and / or reconstructed image blocks. For example, to reconstruct the original image block, the transformed residual block from the scaling and inverse transform component 229 may be combined with the corresponding predictive block from the in-picture predictive component 217 and / or the motion compensation component 219. Filters may then be applied to the reconstructed image block. In some examples, the filter may be applied to the residual block instead. As with the other components in Figure 2, the filter-controlled analysis component 227 and the in-loop filter component 225 may be highly integrated and often implemented together, but are shown separately for conceptual purposes. Filters applied to the reconstructed reference block are applied to a specific spatial region and include several parameters for adjusting how such filters are applied. The filter-controlled analysis component 227 analyzes the reconstructed reference block to determine where such filters should be applied and sets the corresponding parameters. Such data is transferred to the header formatting and CABAC component 231 as filter-controlled data for encoding. The in-loop filter component 225 applies such a filter based on filter control data. The filter may include a deblocking filter, a noise suppression filter, a SAO filter, and an adaptive loop filter. Such filters may be applied, as an example, in the spatial / pixel domain (e.g., for a reconstructed pixel block) or in the frequency domain.

[0061] When operating as an encoder, the filtered, reconstructed image blocks, residual blocks, and / or prediction blocks are stored in the decoded picture buffer component 223 for later use in motion estimation, as described above. When operating as a decoder, the decoded picture buffer component 223 stores the reconstructed and filtered blocks and transfers them to the display as part of the output video signal. The decoded picture buffer component 223 may be any memory device capable of storing the prediction blocks, residual blocks, and / or reconstructed image blocks.

[0062] The header formatting and CABAC component 231 receives data from various components of the codec system 200 and encodes such data into a coded bitstream for transmission to the decoder. Specifically, the header formatting and CABAC component 231 generates various headers for encoding control data such as general control data and filter control data. Furthermore, prediction data, including intra-prediction and motion data, as well as residual data in the form of quantization transformation coefficient data, are all encoded in the bitstream. The final bitstream contains all the information desired by the decoder to reconstruct the segmented original video signal 201. Such information may also include an intra-prediction mode index table (also called a codeword mapping table), definitions of coding contexts for various blocks, a representation of the most probable intra-prediction mode, a representation of segmentation information, and so on. Such data may be encoded by employing entropy coding. For example, information may be encoded by employing context-adaptive variable-length coding (CAVLC), CABAC, syntax-based context-adaptive binary arithmetic coding (SBAC), probability interval partitioned entropy (PIPE) coding, or another entropy coding technique. Following entropy coding, the coded bitstream may be transmitted to another device (e.g., a video decoder) or archived for later transmission or retrieval.

[0063] Figure 3 is a block diagram of an exemplary video encoder 300. The video encoder 300 may be employed to perform the encoding function of the codec system 200 and / or to perform steps 101, 103, 105, 107, and / or 109 of the operation method 100. The encoder 300 divides the input video signal, resulting in a divided video signal 301, which is substantially similar to the divided video signal 201. The divided video signal 301 is then compressed and encoded into a bitstream by the components of the encoder 300.

[0064] Specifically, the segmented video signal 301 is transferred to the in-picture prediction component 317 for intra-prediction. The in-picture prediction component 317 may be substantially similar to the in-picture estimation component 215 and the in-picture prediction component 217. The segmented video signal 301 is also transferred to the motion compensation component 321 for inter-prediction based on a reference block in the decoded picture buffer component 323. The motion compensation component 321 may be substantially similar to the motion estimation component 221 and the motion compensation component 219. The prediction blocks and residual blocks from the in-picture prediction component 317 and the motion compensation component 321 are transferred to the transformation and quantization component 313 for transformation and quantization of the residual blocks. The transformation and quantization component 313 may be substantially similar to the transformation scaling and quantization component 213. The transformed and quantized residual blocks, as well as the corresponding prediction blocks, are transferred to the entropy coding component 331 (along with the associated control data) for coding into the bitstream. The entropy coding component 331 may be substantially similar to the header formatting and CABAC component 231.

[0065] The transformed and quantized residual blocks, and / or the corresponding predicted blocks, are also transferred from the transform and quantization component 313 to the inverse transform and quantization component 329 for reconstruction into reference blocks for use by the motion compensation component 321. The inverse transform and quantization component 329 may be substantially similar to the scaling and inverse transform component 229. The in-loop filters in the in-loop filter component 325 are also applied, as example, to the residual blocks and / or the reconstructed reference blocks. The in-loop filter component 325 may be substantially similar to the filter-controlled analysis component 227 and the in-loop filter component 225. The in-loop filter component 325 may contain multiple filters as described with respect to the in-loop filter component 225. The filtered blocks are then stored in the decoded picture buffer component 323 for use as reference blocks by the motion compensation component 321. The decoded picture buffer component 323 may be substantially similar to the decoded picture buffer component 223.

[0066] Figure 4 is a block diagram illustrating an exemplary video decoder 400. The video decoder 400 may be employed to perform the decoding function of the codec system 200 and / or to perform steps 111, 113, 115, and / or 117 of the operation method 100. The decoder 400, for example, receives a bitstream from the encoder 300 and generates a reconstructed output video signal based on the bitstream for display to the end user.

[0067] The bitstream is received by the entropy decoding component 433. The entropy decoding component 433 is configured to implement an entropy decoding scheme, such as CAVLC, CABAC, SBAC, PIPE coding, or other entropy coding techniques. For example, the entropy decoding component 433 may employ header information to provide context for interpreting additional data encoded as codewords in the bitstream. The decoded information includes any desired information for decoding the video signal, such as general control data, filter control data, piecewise information, motion data, prediction data, and quantization transformation coefficients from residual blocks. The quantization transformation coefficients are transferred to the inverse transform and quantization component 429 for reconstruction into residual blocks. The inverse transform and quantization component 429 may be similar to the inverse transform and quantization component 329.

[0068] The reconstructed residual blocks and / or predicted blocks are transferred to the in-picture prediction component 417 for reconstruction into image blocks based on intra-predictive operation. The in-picture prediction component 417 may be similar to the in-picture estimation component 215 and the in-picture prediction component 217. Specifically, the in-picture prediction component 417 employs a prediction mode to determine the position of a reference block in the frame and applies the residual blocks to the result to reconstruct the intra-predicted image block. The reconstructed, intra-predicted image block and / or residual block, as well as the corresponding inter-predictive data, are transferred to the decoded picture buffer component 423 via the in-loop filter component 425, which may be substantially similar to the decoded picture buffer component 223 and the in-loop filter component 225, respectively. The in-loop filter component 425 filters the reconstructed image block, residual block, and / or predicted block, and such information is stored in the decoded picture buffer component 423. The reconstructed image blocks from the decoded picture buffer component 423 are transferred to the motion compensation component 421 for interpretation. The motion compensation component 421 may be substantially similar to the motion estimation component 221 and / or motion compensation component 219. Specifically, the motion compensation component 421 takes motion vectors from a reference block to generate a prediction block and applies a residual block to the result to reconstruct the image block. The resulting reconstructed block may also be transferred to the decoded picture buffer component 423 via the in-loop filter component 425. The decoded picture buffer component 423 continues to store the additional reconstructed image blocks, which may be reconstructed into frames via piecewise information. Such frames may also be placed in a sequence. The sequence is output to a display as a reconstructed output video signal.

[0069] Figure 5 is a schematic diagram showing an example of a unidirectional interpretation 500, which is performed to determine motion vectors (MV) in, for example, the block compression step 105, the block decoding step 113, the motion estimation component 221, the motion compensation component 219, the motion compensation component 321, and / or the motion compensation component 421.

[0070] The unidirectional interpretation 500 employs a reference picture 530 having a reference block 531 to predict the current block 511 in the current picture 510. The reference picture 530 may be positioned temporally after the current picture 510 (for example, like a subsequent reference picture), but in some examples it may be positioned temporally before the current picture 510 (for example, like a preceding reference picture). The current picture 510 is an exemplary frame / picture being encoded / decoded at a particular time. The current picture 510 contains objects in the current block 511 that correspond to objects in the reference block 531 of the reference picture 530. The reference picture 530 is the picture employed as a reference for encoding the current picture 510, and the reference block 531 is a block in the reference picture 530 that contains objects that are also included in the current block 511 of the current picture 510.

[0071] The current block 511 is any coding unit being coded / decoded at a specified point during the coding process. The current block 511 may be an entire segmented block, or a subblock when employing an affine interpretation mode. The current picture 510 is some temporal distance (TD) 533 away from the reference picture 530. TD 533 represents the amount of time between the current picture 510 and the reference picture 530 in the video sequence and may be measured in picture units. Predictive information for the current block 511 may refer to the reference picture 530 and / or the reference block 531 by a reference index indicating the direction and temporal distance between the pictures. Over the time period represented by TD 533, an object in the current block 511 moves from one position in the current picture 510 to another position in the reference picture 530 (for example, the position of the reference block 531). For example, an object may move along a motion trajectory 513, which is the direction of the object's movement over time. The motion vector 535 represents the direction and magnitude of the object's movement along the motion trajectory 513 across the TD 533. Thus, the encoded motion vector 535, the reference block 531, and the residual including the difference between the current block 511 and the reference block 531 provide sufficient information to reconstruct the current block 511 and to determine the position of the current block 511 within the current picture 510.

[0072] Figure 6 is a schematic diagram showing an example of a bidirectional interpretation 600, which is performed to determine the MV, for example, in the block compression step 105, the block decoding step 113, the motion estimation component 221, the motion compensation component 219, the motion compensation component 321, and / or the motion compensation component 421.

[0073] The bidirectional interpretation 600 is similar to the unidirectional interpretation 500, but employs a pair of reference pictures to predict the current block 611 within the current picture 610. Thus, the current picture 610 and the current block 611 are substantially similar to the current picture 510 and the current block 511, respectively. The current picture 610 is temporally positioned between the preceding reference picture 620, which appears before the current picture 610 in the video sequence, and the succeeding reference picture 630, which appears after the current picture 610 in the video sequence. The preceding reference picture 620 and the succeeding reference picture 630 are substantially similar to the reference picture 530.

[0074] The current block 611 is aligned with the preceding reference block 621 in the preceding reference picture 620 and the subsequent reference block 631 in the subsequent reference picture 630. Such alignment indicates that, throughout the course of the video sequence, the object moves along the motion trajectory 613 and through the current block 611 from its position in the preceding reference block 621 to its position in the subsequent reference block 631. The current picture 610 is some preceding temporal distance (TD0) 623 away from the preceding reference picture 620 and some subsequent temporal distance (TD1) 633 away from the subsequent reference picture 630. TD0 623 represents the amount of time between the preceding reference picture 620 and the current picture 610 in the video sequence, in picture units. TD1 633 represents the amount of time between the current picture 610 and the subsequent reference picture 630 in the video sequence, in picture units. Therefore, the object moves along the motion path 613 from the preceding reference block 621 to the current block 611 over the time period indicated by TD0 623. The object also moves along the motion path 613 from the current block 611 to the subsequent reference block 631 over the time period indicated by TD1 633. Predictive information for the current block 611 may refer to the preceding reference picture 620 and / or the preceding reference block 621, as well as the subsequent reference picture 630 and / or the subsequent reference block 631, by a pair of reference indices indicating the directional and temporal distance between the pictures.

[0075] The preceding motion vector (MV0) 625 represents the direction and magnitude of the object's movement along the motion trajectory 613 across TD0 623 (for example, between the preceding reference picture 620 and the current picture 610). The succeeding motion vector (MV1) 635 represents the direction and magnitude of the object's movement along the motion trajectory 613 across TD1 633 (for example, between the current picture 610 and the succeeding reference picture 630). Thus, in the bidirectional interpretation 600, the current block 611 can be coded and reconstructed by employing the preceding reference block 621 and / or the succeeding reference block 631, MV0 625, and MV1 635.

[0076] Figure 7 is a schematic diagram showing an example of layer-based prediction 700, which is performed to determine the MV, for example, in the block compression step 105, the block decoding step 113, the motion estimation component 221, the motion compensation component 219, the motion compensation component 321, and / or the motion compensation component 421. Layer-based prediction 700 is similar to unidirectional interpretation 500 and / or bidirectional interpretation 600, but is also performed between pictures in different layers.

[0077] Layer-based prediction 700 is applied between pictures 711, 712, 713, and 714 and pictures 715, 716, 717, and 718, within different layers. In the illustrated example, pictures 711, 712, 713, and 714 are part of layer N+1 732, and pictures 715, 716, 717, and 718 are part of layer N731. Layers such as layer N731 and / or layer N+1 732 are groups of pictures all related to similar values ​​of properties such as similar size, quality, resolution, signal-to-noise ratio, and capability. In the illustrated example, layer N+1 732 is related to a larger image size than layer N731. Therefore, in this example, pictures 711, 712, 713, and 714 in layer N+1 732 have larger picture sizes (e.g., larger height and width, and therefore more samples) than pictures 715, 716, 717, and 718 in layer N731. However, such pictures may be separated between layer N+1 732 and layer N731 by other characteristics. Although only two layers, namely layer N+1 732 and layer N731, are illustrated, a set of pictures may be separated into any number of layers based on relevant characteristics. Layers N+1 732 and N731 may also be indicated by layer IDs. A layer ID is a data item associated with a picture, indicating that the picture is part of the layer being shown. Therefore, each picture 711-718 may be associated with a corresponding layer ID to indicate which layer N+1 732 or layer N731 contains the corresponding picture.

[0078] Pictures 711-718 in different layers 731-732 are configured to be displayed as alternatives. Thus, pictures 711-718 in different layers 731-732 can share the same picture sequence count and may be contained within the same AU. As used herein, an AU is a set of one or more coded pictures associated with the same display time for the output from the DPB. For example, if the smaller picture is desired, the decoder may decode and display picture 715 at the current display time, or if the larger picture is desired, the decoder may decode and display picture 711 at the current display time. Thus, pictures 711-714 in the higher layer N+1 732 contain substantially the same image data as the corresponding pictures 715-718 in the lower layer N731 (despite the difference in picture size). Specifically, picture 711 contains substantially the same image data as picture 715, picture 712 contains substantially the same image data as picture 716, and so on.

[0079] Pictures 711-718 can be coded by reference to other pictures 711-718 in the same layer N731 or N+1 732. Coding a picture by reference to another picture in the same layer results in an interprediction 723, which is substantially similar to a unidirectional interprediction 500 and / or a bidirectional interprediction 600. The interprediction 723 is indicated by a solid arrow. For example, picture 713 may be coded by employing an interprediction 723 using one or two of pictures 711, 712, and / or 714 in layer N+1 732 as references, where one picture is referenced for a unidirectional interprediction and / or two pictures are references for a bidirectional interprediction. Furthermore, picture 717 may be coded by employing interprediction 723, using one or two of pictures 715, 716, and / or 718 in layer N731 as references, where one picture is referenced for unidirectional interprediction and / or two pictures are references for bidirectional interprediction. When a picture is used as a reference for another picture in the same layer when performing interprediction 723, that picture may be called a reference picture. For example, picture 712 may be a reference picture used to code picture 713 according to interprediction 723. Interprediction 723 can also be called intralayer prediction in a multilayer context. Thus, interprediction 723 is a mechanism for coding a sample in the current picture by reference to an indicated sample in a reference picture that is different from the current picture, however the reference picture and the current picture are in the same layer.

[0080] Pictures 711-718 can also be coded by reference to other pictures 711-718 in different layers. This process is also known as inter-layer prediction 721 and is indicated by a dashed arrow. Inter-layer prediction 721 is a mechanism for coding a sample of the current picture by reference to an indicated sample in a reference picture, provided that the current picture and the reference picture are in different layers and therefore have different layer IDs. For example, a picture in the lower layer N731 can be used as a reference picture to code the corresponding picture in the higher layer N+1732. In concrete terms, picture 711 can be coded by reference to picture 715 via inter-layer prediction 721. In such a case, picture 715 is used as the inter-layer reference picture. An inter-layer reference picture is a reference picture used for inter-layer prediction 721. In most cases, the inter-layer prediction 721 is constrained so that the current picture, such as picture 711, can only use inter-layer reference pictures, such as picture 715, that are located in lower layers within the same AU. When multiple layers (e.g., three or more) are available, the inter-layer prediction 721 can encode / decode the current picture based on multiple inter-layer reference pictures at lower levels than the current picture.

[0081] The video encoder can employ layer-based prediction 700 to encode pictures 711-718 through many different combinations and / or rearrangements of inter-prediction 723 and inter-layer prediction 721. For example, picture 715 may be coded according to intra-prediction. Pictures 716-718 may then be coded according to inter-prediction 723 by using picture 715 as a reference picture. Furthermore, picture 711 may be coded according to inter-layer prediction 721 by using picture 715 as an inter-layer reference picture. Pictures 712-714 may then be coded according to inter-prediction 723 by using picture 711 as a reference picture. Thus, a reference picture can function as both a single-layer reference picture and an inter-layer reference picture for different coding mechanisms. By coding the picture of the higher layer N+1 732 based on the picture of the lower layer N731, the higher layer N+1 732 can avoid employing intra-prediction, which has much lower coding efficiency than inter-prediction 723 and inter-layer prediction 721. Thus, the poor coding efficiency of intra-prediction may be limited to the smallest / lowest quality picture, and therefore limited to coding the smallest amount of video data. Pictures used as reference pictures and / or inter-layer reference pictures may be indicated in the reference picture list entries contained within the reference picture list structure.

[0082] Figure 8 is a schematic diagram showing an exemplary reference picture list structure (RPL structure) 800. The RPL structure 800 may be employed to store the display of reference pictures and / or inter-layer reference pictures used in unidirectional interpretation 500, bidirectional interpretation 600, and / or layer-based prediction 700. Thus, the RPL structure 800 may be employed by the codec system 200, encoder 300, and / or decoder 400 when performing method 100.

[0083] The RPL structure 800 is an addressable syntax structure that includes multiple reference picture lists, such as RPL0 811 and RPL1 812. The RPL structure 800 may be stored in the bitstream's SPS and / or slice header, as an example. The reference picture lists, such as RPL0 811 and RPL1 812, are lists of reference pictures used for inter-prediction and / or inter-layer prediction. Each of RPL0 811 and RPL1 812 may contain multiple entries 815. A reference picture list structure entry 815 is an addressable location in the RPL structure 800 that points to a reference picture associated with the reference picture list, such as RPL0 811 and / or RPL1 812. Each entry 815 may contain a picture sequence count (POC) value (or other pointer value) that references a picture used for inter-prediction. Specifically, references to pictures used by the unidirectional interpretation 500 are stored in RPL0 811, while references to pictures used by the bidirectional interpretation 600 are stored in both RPL0 811 and RPL1 812. For example, the bidirectional interpretation 600 may use one reference picture indicated by RPL0 811 and one reference picture indicated by RPL1 812.

[0084] In a concrete example, the RPL structure 800 may be represented as ref_pic_list_struct( listIdx, rplsIdx ), where listIdx821 identifies the reference picture lists RPL0 811 and / or RPL1 812, and rplsIdx825 identifies entry 815 in the reference picture lists. Thus, ref_pic_list_struct is a syntax structure that returns entry 815 based on listIdx821 and rplsIdx825. The encoder can encode a portion of the RPL structure 800 for each non-intra-coded slice in the video sequence. The decoder can then resolve the corresponding portion of the RPL structure 800 before decoding each non-intra-coded slice in the coded video sequence.

[0085] As described above, a reference picture can be referenced for inter-layer prediction. Furthermore, a reference picture can be used as an inter-layer reference picture for inter-layer prediction. Therefore, the RPL structure 800 is modified by including an ILRP flag 833 and an ILRP layer indicator 835 to support inter-layer prediction. The ILRP flag 833 is data indicating whether the picture referenced by the corresponding entry 815 in the RPL structure 800 is an inter-layer reference picture used for inter-layer prediction. Therefore, an encoder can use the ILRP flag 833 to indicate whether each entry 815 should be treated as an ILRP entry. An ILRP entry is any entry 815 that references an inter-layer reference picture used for inter-layer prediction. Furthermore, a decoder can use the ILRP flag 833 to determine whether each entry 815 in the RPL structure 800 is an ILRP entry. In a specific example, the ILRP flag 833 is represented as inter_layer_ref_pic_flag[ listIdx ][ rplsIdx ][ i ], where i is a counter variable whose value indicates the corresponding entry 815. When the i-th entry in ref_pic_list_struct( listIdx, rplsIdx ) is an ILRP entry, inter_layer_ref_pic_flag[ listIdx ][ rplsIdx ][ i ] can be set to equal 1. Furthermore, when the i-th entry in ref_pic_list_struct( listIdx, rplsIdx ) is not an ILRP entry, inter_layer_ref_pic_flag[ listIdx ][ rplsIdx ][ i ] can be set to equal 0.

[0086] As described above, an interlayer reference picture may be located in the same AU as the current picture being encoded / decoded and may have the same POC value. Therefore, the RPL structure 800 does not need to be modified to add the POC value of the corresponding interlayer reference picture. However, the decoder may not be able to infer which of the one or more layers of the AU contains the appropriate interlayer reference picture for decoding the current picture. For this purpose, an ILRP layer indicator 835 is included. The ILRP layer indicator 835 is data that indicates the layer associated with the interlayer reference picture referenced by the current picture. Specifically, the ILRP layer indicator 835 may indicate one or more layers for each entry 815, which is an ILRP entry as indicated by the ILRP flag 833. Therefore, the encoder can encode the ILRP layer indicator 835 into the bitstream to indicate the layer of one or more interlayer reference pictures associated with entry 815. In addition, when entry 815 is an ILRP entry as indicated by the ILRP flag 833, the decoder can determine the layer of the inter-layer reference picture based on the ILRP layer indicator 835. Thus, the addition of the ILRP flag 833 and the ILRP layer indicator 835 to the RPL structure 800 provides sufficient information to enable the RPL structure 800 to manage the reference picture for inter-layer prediction.

[0087] Figure 9 is a schematic diagram showing an exemplary bitstream 900 including coding tool parameters for supporting inter-layer prediction. For example, bitstream 900 may be generated by codec system 200 and / or encoder 300 for decoding by codec system 200 and / or decoder 400. As another example, bitstream 900 may be generated by encoder in step 109 of method 100 for use by decoder in step 111. Furthermore, bitstream 900 may be a coded video sequence that can be coded according to unidirectional inter-prediction 500, bidirectional inter-prediction 600, and / or layer-based prediction 700. In addition, bitstream 900 may be employed to communicate RPL structure 800.

[0088] The bitstream 900 includes a sequence parameter set (SPS) 910, multiple picture parameter sets (PPS) 911, multiple slice headers 915, and image data 920. The SPS 910 contains sequence data common to all pictures in the video sequence contained within the bitstream 900. Such data may include picture size determination, bit depth, coding tool parameters, bitrate constraints, etc. The PPS 911 contains parameters that apply to the entire picture. Thus, each picture in the video sequence may refer to a PPS 911. While each picture refers to a PPS 911, it should be noted that in some examples a single PPS 911 may contain data for multiple pictures. For example, several similar pictures may be coded according to similar parameters. In such cases, a single PPS 911 may contain data for such similar pictures. The PPS 911 may indicate the coding tools, quantization parameters, offsets, etc., available for slices in the corresponding picture. The slice headers 915 contain parameters specific to each slice in the picture. Therefore, there may be one slice header 915 per slice in a video sequence. The slice header 915 may contain slice type information, picture order count (POC), reference picture list, prediction weights, tile entry point, deblocking parameters, etc. Note that in some contexts, the slice header 915 may also be called the tile group header. In some examples, the bitstream 900 may also contain a picture header, and note that the picture header is a syntactic structure containing parameters that apply to all slices in a single picture. For this reason, in some contexts, the picture header and slice header 915 may be used interchangeably. For example, some parameters may be moved between the slice header 915 and the picture header depending on whether such parameters are common to all slices in the picture.

[0089] Image data 920 includes video data encoded according to interpretation, intrapretation, and / or interlayer prediction, as well as corresponding transformed and quantized residual data. For example, a video sequence includes multiple pictures 923. A picture 923 is an array of lumen samples and / or chroma samples that make up a frame or a field of a frame. A frame is a complete image intended for a complete or partial display to the user at a corresponding moment in the video sequence. A picture 923 may be contained within a single AU 921. An AU 921 is a coding unit configured to store all coded pictures 923 having the same picture order count, and optionally one or more headers, such as a slice header 915, containing parameters representing the coding mechanism employed to code the coded pictures 923. Thus, an AU 921 may contain a single picture 923 for each picture level contained within the bitstream 900. A picture 923 includes one or more slices 925. Slice 925 may be defined as an integer number of complete tiles of picture 923 or an integer number of consecutive complete CTU rows (e.g., within a tile) that are exclusively contained within a single NAL unit. Slice 925 is further divided into CTUs and / or coding tree blocks (CTBs). A CTU is a group of samples of a predetermined size that can be partitioned by a coding tree. A CTB is a subset of a CTU and contains the lumen or chroma components of the CTU. A CTU / CTB is further divided into coding blocks based on the coding tree. Coding blocks can then be encoded / decoded according to a prediction mechanism.

[0090] The bitstream 900 includes various coding tool parameters to support inter-layer prediction. Specifically, the bitstream includes a reference picture list structure 931, an ILRP flag 933, and an ILRP layer indicator 935, which may be substantially similar to the RPL structure 800, the ILRP flag 833, and the ILRP layer indicator 835, respectively. The reference picture list structure 931, the ILRP flag 933, and the ILRP layer indicator 935 may be coded in the SPS 910, the slice header 915, and / or the corresponding picture header. Thus, the encoder can enumerate reference pictures in entries in the reference picture list structure 931, indicate which of the reference pictures are inter-layer reference pictures in the ILRP flag 933, and indicate which layers contain the relevant inter-layer reference pictures in the ILRP layer indicator 935. Furthermore, the decoder can decode the SPS910, slice header915, and / or corresponding picture header to obtain the reference picture list structure931, the ILRP flag933, and the ILRP layer indicator935. The decoder can then determine the reference picture for the current picture from the entries in the reference picture list structure931. The decoder can also determine which of the reference pictures is an inter-layer reference picture by employing the ILRP flag933. Furthermore, the decoder can determine one or more levels associated with an inter-layer reference picture by employing the ILRP layer indicator935. Thus, the bitstream900 is configured to provide sufficient information for managing reference pictures when performing a combination of intra-prediction, inter-prediction, and / or inter-layer prediction to code a video sequence.

[0091] The information described above will be explained in more detail below in this specification. A reference picture resampling (RPR) mechanism may be employed to change the spatial resolution of the coded picture in the middle of the bitstream. This resolution change can be achieved in the current picture even when the current picture is not intra-coded. To enable this function, the current picture may reference one or more reference pictures for interpretation purposes, provided that the reference pictures employ a different spatial resolution than that of the current picture. Thus, the encoding and decoding of the current picture may involve resampling of such reference pictures or portions of reference pictures. This function is sometimes called adaptive resolution change (ARC). Reference picture resampling can be implemented at either the picture level or the coding block level.

[0092] Several implementations can benefit from RPR. For example, video calls and video conferencing may employ rate adaptation. The rate of encoded video can be adapted to changing network conditions. As network conditions deteriorate and available bandwidth decreases, the encoder may adapt by encoding the picture at a lower resolution. Another example where changing active speakers in multi-party video conferencing can benefit from RPR is when the active speaker is shown at a larger video size than the other conference participants. When the active speaker changes, the picture resolution for each participant may also be adjusted. The RPR / ARC mechanism becomes increasingly beneficial as the active speaker changes more frequently. Another example where rapid start-ups in streaming can benefit from RPR is when streaming applications buffer decoded pictures up to a certain length before they begin to display. Starting the bitstream at a lower resolution may allow the application to buffer enough pictures to begin displaying more quickly. Once display has started, the resolution may then be increased. In another example, adaptive stream switching in streaming can benefit from RPR. Dynamic Adaptive Streaming over HTTP (DASH) employs a feature called @mediaStreamStructureId. This feature enables switching between different representations in an open group of picture (GOP) random access point with an undecodeable reading picture, sometimes called a clean random access (CRA) picture with an associated RASL picture in HEVC. For example, two different representations of the same video may have different bitrates and the same spatial resolution, while they have the same @mediaStreamStructureId value. In such a case, switching between the two representations in the CRA picture with an associated RASL picture may occur.RASL pictures associated with CRA pictures can be decoded with acceptable quality, enabling seamless switching. When switching between DASH representations with different spatial resolutions, ARC / RPR allows the @mediaStreamStructureId function to be employed.

[0093] ARC / RPR can be implemented by employing layered video coding, sometimes called scalable video coding and / or video coding with scalability. Scalability in video coding can be supported by using multilayer coding techniques. A multilayer bitstream comprises a base layer (BL) and one or more enhancement layers (EL). Scalability may include spatial scalability, quality / signal-to-noise ratio (SNR) scalability, multiview scalability, etc. When multilayer coding techniques are employed, a picture (or part of a picture) can be coded (1) without using a reference picture (intra-prediction), (2) by reference to one or more reference pictures in the same layer (inter-prediction), or (3) by reference to one or more reference pictures in other layers (inter-layer prediction). A reference picture currently used for inter-layer prediction of a picture is called an inter-layer reference picture (ILRP).

[0094] The H.26x video coding family can provide support for scalability in isolated profiles, moving away from profiles for single-layer coding. Scalable Video Coding (SVC) is a scalable extension of AVC / H.264 that provides support for spatial, temporal, and quality scalability. In the case of SVC, a flag is signaled within each macroblock (MB) in a picture to indicate whether MBs are predicted using collated blocks from lower layers. Predictions from collated blocks may include texture mode, motion vector mode, and / or coding mode.

[0095] Scalable HEVC (SHVC) is an extension of HEVC / H.265 that provides support for spatial and quality scalability. Multiview HEVC (MV-HEVC) is an extension of HEVC / H.265 that provides support for multiview scalability. Three-dimensional (3D) HEVC (3D-HEVC) is an extension of HEVC / H.264 that provides support for 3D video coding. Temporal scalability can be employed in single-layer HEVC codecs. The multi-layer extension of HEVC employs a mechanism in which the decoded picture used for inter-layer prediction is taken only from the same AU and treated as a long-term reference picture (LTRP). Such a picture is assigned a reference index in the reference picture list, along with other temporal reference pictures in the current layer. Inter-layer prediction (ILP) is achieved at the prediction unit (PU) level by setting the reference index value to refer to an inter-layer reference picture in the reference picture list.

[0096] When the ILRP has a different spatial resolution than the currently encoded or decoded picture, spatial scalability may employ resampling of the reference picture or a portion of the reference picture. Reference picture resampling can be implemented at either the picture level or the coding block level.

[0097] In video codec specifications, pictures may be identified for multiple purposes. For example, a picture may be identified for use as a reference picture in interpretation, for output from the DPB, for scaling motion vectors, for weighted prediction, etc. In some video coding systems, pictures may be identified by a picture order count (POC). Furthermore, pictures in the DPB may be marked as being used for short-term reference, used for long-term reference, or not used for reference. If a picture is marked as not used for reference, it can no longer be used for prediction. When such a picture is no longer needed for output, it may be removed from the DPB.

[0098] AVC may employ short-term and long-term reference pictures. When a picture is no longer needed as a predictive reference, the reference picture may be marked as not to be used for reference. The transition between these three statuses (short-term, long-term, and not to be used for reference) is controlled by a marking process for decoded reference pictures. For reference picture marking in such a system, an implicit sliding window process and an explicit memory management control operation (MMCO) process may be employed. The sliding window process marks short-term reference pictures as not to be used for reference when the number of reference frames equals the maximum number in the SPS (max_num_ref_frames). Short-term reference pictures are stored in a first-in, first-out manner so that the most recently decoded short-term picture is held in the DPB. An explicit MMCO process may include multiple MMCO commands. The MMCO command may mark one or more short-term or long-term reference pictures as not to be used for reference, mark all pictures as not to be used for reference, or mark the current reference picture or an existing short-term reference picture as long-term, and assign a long-term picture index to that long-term reference picture. In AVC, the reference picture marking operation and the process of outputting and removing pictures from the DPB are performed after the pictures have been decoded.

[0099] HEVC employs a reference picture set (RPS) for reference picture marking. With an RPS, a complete set of reference pictures used by the current or any subsequent picture is provided for each slice. Therefore, the complete set of all pictures that should be retained in the DPB for use by current or future pictures is signaled within the RPS. This differs from the AVC system, which only signals relative changes in the DPB. The RPS does not need to store information from earlier pictures in the decoding order when maintaining the precise status of reference pictures in the DPB.

[0100] In AVC, picture marking and buffering operations (both outputting and removing decoded pictures from the DPB) may be applied after the current picture has been decoded. In HEVC, the RPS is decoded first from the slice header of the current picture. Then, picture marking and buffering operations may be applied before the current picture is decoded.

[0101] VVC employs Reference Picture List 0 and Reference Picture List 1 for reference picture management. Using this method, the reference picture lists for pictures are immediately created without the need for a reference picture list initialization process or a reference picture list modification process. Furthermore, reference picture marking is immediately performed based on the two reference picture lists.

[0102] The aforementioned system has several problems. The VVC decoder should be able to derive inter-layer reference pictures in order to enable a multi-layer video codec with inter-layer prediction. To implement such a mechanism, the codec should employ a mechanism for signaling RPL, deriving RPL, and performing reference picture marking in a multi-layer context.

[0103] This disclosure includes several techniques for reference picture management in layered video coding. These include RPL signaling, RPL derivation, and reference picture marking. The description of these techniques is based on VVC but is applicable to other layered video coding specifications. For example, this disclosure includes a mechanism for RPL signaling in a multilayer video codec with interlayer prediction based on VVC. The following constraints may apply to the examples described below: All VCL NAL units having the same layer ID and associated with the same presentation time may have one picture. Furthermore, all VCL NAL units within a picture may have the same POC value. Such a POC value may also be referred to as the POC value of the picture.

[0104] The first example can be summarized as follows: All pictures related to the same presentation time belong to one access unit. Pictures in different layers and within the same access unit have the same POC value. A first flag, such as inter_layer_ref_pics_flag, may be added to the SPS to specify whether ILRP can be used for interpretation of any coded pictures in the CVS. When the first flag specifies that ILRP can be used for interpretation of one or more coded pictures in the CVS, a second flag may be signaled for each entry in the RPL structure to specify whether the entry is an ILRP entry. When the second flag for an entry specifies that the entry is an ILRP entry, a first delta value may be signaled, specifying the difference of -1 between the layer ID of the current picture and the picture referenced by the entry. In some examples, the first delta value specifies the difference of -1 between the layer index of the layer containing the current picture and the layer index of the layer containing the picture referenced by the entry. At the start of decoding the current slice, the RPL may be configured by the decoder according to the RPL signaling in the bitstream. When an entry is an ILRP entry, the entry is derived to refer to a picture that has the same PicOrderCntVal as the current picture and a layer ID equal to the current picture's layer ID - the delta value of the first - 1. At the start of decoding the current picture, each ILRP is marked to be used for long-term reference (if any). At the end of decoding the current picture, each ILRP is marked to be used for short-term reference (if any). When decoding a picture of the same layer, the decoded picture may only be marked as not to be used for reference.

[0105] The method for performing the above example is as follows: In one example, a method for decoding a video bitstream is disclosed. The bitstream has multiple layers, each having multiple pictures. One or more of the pictures belong to different layers and have the same presentation time, and thus form one access unit. The method comprises deriving a POC value for each picture. The POC values ​​of all pictures in one access unit are the same. Several RPLs are derived for the current slice. Each entry is associated with a flag that specifies whether the entry is an ILRP entry. The current slice is decoded based on the derived RPLs. In one exemplary embodiment, the bitstream includes an SPS flag that specifies whether an ILRP entry is used for interpretation of any coded picture in the CVS. In one exemplary embodiment, when an entry in the RPL is specified to be an ILRP entry, the bitstream includes a first delta value that specifies the difference -1 between the layer ID of the current picture containing the current slice and the picture referenced by the entry. In one exemplary embodiment, an ILRP entry refers to a picture that has the same PicOrderCntVal as the current picture and a layer ID equal to the current picture's layer ID - the first delta value - 1. In one exemplary embodiment, at the start of decoding the current picture, each ILRP is marked to be used for long-term reference (if any). At the end of decoding the current picture, each ILRP is marked to be used for short-term reference (if any).

[0106] A second method for implementing the above example is as follows: In one example, all pictures related to the same presentation time belong to one access unit. Each picture may be associated with an intra-layer POC value and a cross-layer POC value. Pictures in one CVS may have different cross-layer POC values. Pictures in different layers but within the same access unit may have the same intra-layer POC value but different cross-layer POC values. No picture is required to reference a picture in a higher layer, and therefore not a picture with a larger layer ID value. When decrypting a picture in the same layer, the decrypted picture may only be marked as not to be used for reference.

[0107] A third method for implementing the above example is as follows: In one example, all pictures related to the same presentation time belong to one access unit. Pictures in a CVS may have different POC values. Pictures in a single CVS may be identified only by their POC value. No picture is required to reference a picture of a higher layer, and therefore not a picture with a higher layer ID value. When decrypting a picture of the same layer, the decrypted picture may be marked only as not to be used for reference.

[0108] A fourth method for implementing the above example is as follows: Each access unit may contain only one picture. Therefore, any two pictures related to the same presentation time but belonging to different layers may belong to two different access units. Pictures in one CVS may have different POC values. Pictures in one CVS may be identified solely by their POC value. No picture is required to reference a picture of a higher layer, and therefore not a picture with a larger layer ID value. Regardless of whether the current picture and the referenced picture belong to the same layer, the referenced picture may be marked as not to be used for reference.

[0109] The first exemplary implementation of the method described above is explained below. The exemplary definitions are as follows: An ILRP is a picture in the same access unit as the current picture, has a nuh_layer_id smaller than the current picture's nuh_layer_id, and is marked to be used for long-term reference. A long-term reference picture (LTRP) is a picture that has a nuh_layer_id equal to the current picture's nuh_layer_id and is marked to be used for long-term reference. A reference picture is a picture that is either a short-term reference picture, a long-term reference picture, or an inter-layer reference picture. A reference picture contains samples that may be used for interpretation in the decoding process of subsequent pictures in the decoding order. A short-term reference picture (STRP) is a picture that has a nuh_layer_id equal to the current picture's nuh_layer_id and is marked to be used for short-term reference.

[0110] An exemplary sequence parameter set RBSP syntax is as follows:

[0111] [Table 1]

[0112] The syntax for an exemplary reference picture list structure is as follows:

[0113] [Table 2]

[0114] The following are exemplary sequence parameter sets and RBSP semantics: `long_term_ref_pics_flag` may be set to 0 to specify that LTRP is not used for inter-prediction of any coded pictures in the CVS. `long_term_ref_pics_flag` may be set to 1 to specify that LTRP may be used for inter-prediction of one or more coded pictures in the CVS. `inter_layer_ref_pics_flag` may be set to 0 to specify that ILRP is not used for inter-prediction of any coded pictures in the CVS. `inter_layer_ref_pics_flag` may be set to 1 to specify that ILRP may be used for inter-prediction of one or more coded pictures in the CVS.

[0115] An example of generic slice header semantics is as follows: slice_type specifies the coding type of the slice according to the table below.

[0116] [Table 3]

[0117] If NalUnitType is a value within the range IDR_W_RADL~CRA_NUT, which includes both endpoints, and the current picture is the first picture in the access unit, then slice_type should be equal to 2.

[0118] The exemplary reference picture list structure semantics are as follows: To specify that the i-th entry in the ref_pic_list_struct( listIdx, rplsIdx ) syntax structure is an ILRP entry, inter_layer_ref_pic_flag[ listIdx ][ rplsIdx ][ i ] may be set to equal to 1. To specify that the i-th entry in the ref_pic_list_struct( listIdx, rplsIdx ) syntax structure is not an ILRP entry, inter_layer_ref_pic_flag[ listIdx ][ rplsIdx ][ i ] may be set to equal to 0. When it does not exist, the value of inter_layer_ref_pic_flag[ listIdx ][ rplsIdx ][ i ] is presumed to be equal to 0. To specify that the i-th entry in the ref_pic_list_struct( listIdx, rplsIdx ) syntax structure is a STRP entry, st_ref_pic_flag[ listIdx ][ rplsIdx ][ i ] may be set to equal to 1. To specify that the i-th entry in the ref_pic_list_struct( listIdx, rplsIdx ) syntax structure is an LTRP entry, st_ref_pic_flag[ listIdx ][ rplsIdx ][ i ] may be set to equal to 0. When inter_layer_ref_pic_flag[ listIdx ][ rplsIdx ][ i ] is equal to 0 and st_ref_pic_flag[ listIdx ][ rplsIdx ][ i ] does not exist, it can be inferred that the value of st_ref_pic_flag[ listIdx ][ rplsIdx ][ i ] is equal to 1.

[0119] The variables NumLtrpEntries[ listIdx ][ rplsIdx ] can be derived as follows: For ( i = 0, NumLtrpEntries[ listIdx ][ rplsIdx ] = 0; i < num_ref_entries[ listIdx ][ rplsIdx ]; i++ ) if( !inter_layer_ref_pic_flag[ listIdx ][ rplsIdx ][ i ] && !st_ref_pic_flag[ listIdx ][ rplsIdx ][ i ] ) NumLtrpEntries[ listIdx ][ rplsIdx ]++

[0120] To specify that the i-th entry in the syntax structure ref_pic_list_struct( listIdx, rplsIdx ) has a value greater than or equal to 0, strp_entry_sign_flag[ listIdx ][ rplsIdx ][ i ] may be set to equal to 1. To specify that the i-th entry in the syntax structure ref_pic_list_struct( listIdx, rplsIdx ) has a value less than 0, strp_entry_sign_flag[ listIdx ][ rplsIdx ][ i ] may be set to equal to 0. If it does not exist, the value of strp_entry_sign_flag[ listIdx ][ rplsIdx ][ i ] can be inferred to be equal to 1.

[0121] The list DeltaPocSt[listIdx][rplsIdx] can be derived as follows: for( i = 0; i < num_ref_entries[ listIdx ][ rplsIdx ]; i++ ) if( !inter_layer_ref_pic_flag[ listIdx ][ rplsIdx ][ i ] && st_ref_pic_flag[ listIdx ][ rplsIdx ][ i ] ) { (7-93) DeltaPocSt[ listIdx ][ rplsIdx ][ i ] = ( strp_entry_sign_flag[ listIdx ][ rplsIdx ][ i ] ) ? abs_delta_poc_st[ listIdx ][ rplsIdx ][ i ] : 0 - abs_delta_poc_st[ listIdx ][ rplsIdx ][ i ]

[0122] rpls_entry_layer_id_delta_minus1[ listIdx ][ rplsIdx ][ i ]+1 specifies the difference between the current picture's nuh_layer_id and the picture referenced by the i-th entry. The value of rpls_entry_layer_id_delta_minus1[ listIdx ][ rplsIdx ][ i ] may be within the range of 0 to 125, including both endpoints.

[0123] An exemplary decoding process for a coded picture is as follows: The decoding process currently operates for picture CurrPic as follows: The NAL unit is decoded. The following decoding process may use syntax from the following elements in the slice header layer and above: Variables and functions related to the picture order count are derived. This may be called only for the first slice of the picture. Non-instantaneous decoding refresh (IDR): At the start of the decoding process for each slice of the picture, the decoding process for constructing the reference picture list may be called to derive reference picture list 0 (RefPicList

[0000] ) and reference picture list 1 (RefPicList

[0001] ). The decoding process for reference picture marking is called, and reference pictures may be marked as not to be used for reference or to be used for long-term reference. This may be called only for the first slice of the picture. When the current picture is a CRA picture with NoIncorrectPicOutputFlag equal to 1, or a Gradual Random Access (GRA) picture with NoIncorrectPicOutputFlag equal to 1, a decoding process is invoked to generate an unavailable reference picture, and such a process may be invoked only for the first slice of the picture. PictureOutputFlag may be set as follows: PictureOutputFlag may be set to equal to 0 if one of the following conditions is true: PictureOutputFlag may be set to equal to 0 when the current picture is a RASL picture and the NoIncorrectPicOutputFlag of the associated IRAP picture is equal to 1. PictureOutputFlag may be set to equal to 0 when gra_enabled_flag is equal to 1 and the current picture is a GRA picture with NoIncorrectPicOutputFlag equal to 1.If gra_enabled_flag is equal to 1, the current picture is associated with a GRA picture that has NoIncorrectPicOutputFlag equal to 1, and the current picture's PicOrderCntVal is less than the associated GRA picture's RpPicOrderCntVal, then PictureOutputFlag may be set to equal to 0. Otherwise, PictureOutputFlag is set to equal to 1. After all slices of the current picture have been decoded, the current decoded picture is marked as to be used for short-term reference, and each ILRP entry in RefPicList

[0000] or RefPicList

[0001] is marked as to be used for short-term reference.

[0124] An exemplary decoding process for constructing a reference picture list is as follows: This process is invoked at the start of the decoding process for each slice of non-IDR picture. Reference pictures are addressed through a reference index, which is an index to the reference picture list. When decoding an intracoding (I) slice, the reference picture list is not used in decoding the slice data. When decoding a unidirectional interprediction (P) slice, only reference picture list 0 (RefPicList

[0000] ) is used in decoding the slice data. When decoding a bidirectional interprediction (B) slice, both reference picture list 0 and reference picture list 1 (RefPicList

[0001] ) are used in decoding the slice data. At the start of the decoding process for each slice of non-IDR picture, reference picture lists RefPicList

[0000] and RefPicList

[0001] are derived. The reference picture lists are used in marking the reference pictures or in decoding the slice data. For I slices of a non-IDR picture that are not the first slice of the picture, RefPicList

[0000] and RefPicList

[0001] may be derived for the purpose of bitstream conformance checking, but their derivation is not required for decoding the current picture or pictures that follow the current picture in the decoding order. For P slices that are not the first slice of the picture, RefPicList

[0001] may be derived for the purpose of bitstream conformance checking, but it is not required for decoding the current picture or pictures that follow the current picture in the decoding order.

[0125] The reference picture lists RefPicList

[0000] and RefPicList

[0001] may be configured as follows: for( i = 0; i < 2; i++ ) { for( j = 0, k = 0, pocBase = PicOrderCntVal; j < num_ref_entries[ i ][ RplsIdx[ i ] ]; j++) { if( !inter_layer_ref_pic_flag[ i ][ RplsIdx[ i ] ][ j ] ) { if( st_ref_pic_flag[ i ][ RplsIdx[ i ] ][ j ] ) { RefPicPocList[ i ][ j ] = pocBase - DeltaPocSt[ i ][ RplsIdx[ i ] ][ j ] if (there is a reference picture picA in the DPB with the same nuh_layer_id as the current picture and a PicOrderCntVal equal to RefPicPocList[i][j]) RefPicList[i][j] = picA else RefPicList[i][j] = "No reference picture found" (8-5) pocBase = RefPicPocList[ i ][ j ] else { if( !delta_poc_msb_cycle_lt[ i ][ k ] ) { if (currently has the same nuh_layer_id as the picture, and PicOrderCntVal & ( MaxPicOrderCntLsb - 1 ) is equal to PocLsbLt[ i ][ k ], and reference picA is in DPB) RefPicList[ i ][ j ] = picA else RefPicList[i][j] = "No reference picture found" else { if (there is currently a reference picA in the DPB with the same nuh_layer_id and PicOrderCntVal as the picture, and FullPocLt[i][k]) RefPicList[ i ][ j ] = picA else RefPicList[i][j] = "No reference picture found" } k++ } else { refPicLayerId = nuh_layer_id - rpls_entry_layer_id_delta_minus1[ i ][ RplsIdx[ i ] ][ j ] - 1 if (there is a reference picture picA in the DPB that has a nuh_layer_id equal to refPicLayerId and the same PicOrderCntVal as the current picture) RefPicList[ i ][ j ] = picA else RefPicList[i][j] = "No reference picture found" } } } }

[0126] For each i equal to 0 or 1, the first NumRefIdxActive[i] entries in RefPicList[i] are referred to as active entries in RefPicList[i], and the other entries in RefPicList[i] are referred to as inactive entries in RefPicList[i]. A particular picture can be referred to by both entries in RefPicList

[0000] and entries in RefPicList

[0001] . A particular picture can also be referred to by two or more entries in RefPicList

[0000] or by two or more entries in RefPicList

[0001] . Active entries in RefPicList

[0000] and active entries in RefPicList

[0001] refer collectively to all reference pictures that can be used for interpretation of the current picture and one or more pictures that follow the current picture in decoding order. The inactive entries in RefPicList

[0000] and RefPicList

[0001] collectively refer to all reference pictures that are not currently used for interpretation of the picture but may be used for interpretation of one or more pictures that follow the current picture in the decoding order. There may be one or more entries in RefPicList

[0000] or RefPicList

[0001] that are not equal to any reference picture because the corresponding picture does not exist in the DPB. Each inactive entry in RefPicList

[0000] or RefPicList

[0000] that is not equal to any reference picture should be ignored. For each active entry in RefPicList

[0000] or RefPicList

[0001] that is not equal to any reference picture, an accidental picture loss should be inferred.

[0127] For bitstream conformance, the following constraints should apply: For each i equal to 0 or 1, num_ref_entries[i][RplsIdx[i]] should not be less than NumRefIdxActive[i]. The picture referenced by each active entry in RefPicList

[0000] or RefPicList

[0001] should exist in the DPB and should have a TemporalId less than or equal to the current picture's TemporalId. The picture referenced by each entry in RefPicList

[0000] or RefPicList

[0001] should not be the current picture. STRP entries in RefPicList

[0000] or RefPicList

[0001] for a slice of a picture, and LTRP entries in RefPicList

[0000] or RefPicList

[0001] for the same or different slices of the same picture, should not reference the same picture. There should be no LTRP entries in RefPicList

[0000] or RefPicList

[0001] where the difference between the PicOrderCntVal of the current picture and the PicOrderCntVal of the picture referenced by the entry is 224 or more. SetOfRefPics is the set of unique pictures referenced by all entries in RefPicList

[0000] that have the same nuh_layer_id as the current picture, and all entries in RefPicList

[0001] that have the same nuh_layer_id as the current picture. The number of pictures in setOfRefPics should be less than or equal to sps_max_dec_pic_buffering_minus1, and setOfRefPics should be the same for all slices of the picture. The pictures referenced by each ILRP entry in RefPicList

[0000] or RefPicList

[0001] of the slice of the current picture should be in the same access unit as the current picture.The picture referenced by each ILRP entry in the current picture slice's RefPicList

[0000] or RefPicList

[0001] should exist in the DPB and should have a nuh_layer_id smaller than the current picture's nuh_layer_id. Each ILRP entry in the slice's RefPicList

[0000] or RefPicList

[0001] should be an active entry.

[0128] An exemplary decoding process for reference picture marking is as follows: This process is called once per picture after decoding the slice header and the decoding process for constructing the reference picture list for the slice, but before decoding the slice data. This process may result in one or more reference pictures in the DPB being marked as either not used for reference or used for long-term reference. Decoded pictures in the DPB may be marked as either not used for reference, used for short-term reference, or used for long-term reference. However, a decoded picture may be marked as only one of these three at any given moment during the operation of the decoding process. Assigning one of these markings to a picture implicitly removes another of these markings when applicable. When a picture is referred to as being marked as being used for reference, this collectively refers to the picture being marked as being used for either short-term reference or used for long-term reference, but not both. STRPs and ILRPs may be identified by their nuh_layer_id and PicOrderCntVal values. LTRPs may be identified by their nuh_layer_id values ​​and the Log2(MaxLtPicOrderCntLsb) least significant bits (LSBs) of their PicOrderCntVal values. If the current picture is a coded layer video sequence start (CLVSS) picture, all referenced pictures in the current DPB that have the same nuh_layer_id as the current picture, if any, are marked as not to be used for reference. Otherwise, the following applies: For each LTRP entry in RefPicList

[0000] or RefPicList

[0001] , if the referenced picture is a STRP with the same nuh_layer_id as the current picture, the picture is marked as to be used for long-term reference.Each referenced picture that has the same nuh_layer_id as the current picture in the DPB and is not referenced by any entry in RefPicList

[0000] or RefPicList

[0001] is marked as not to be used for reference. For each ILRP entry in RefPicList

[0000] or RefPicList

[0001] , the referenced picture is marked as to be used for long-term reference.

[0129] A second exemplary implementation of the method described above is explained below. The exemplary definitions are as follows: An ILRP is a picture in the same access unit as the current picture, has a nuh_layer_id smaller than the current picture's nuh_layer_id, and is marked to be used for long-term references. An LTRP is a picture that has a nuh_layer_id equal to the current picture's nuh_layer_id and is marked to be used for long-term references. A reference picture is a picture that is either a short-term reference picture, a long-term reference picture, or an inter-layer reference picture. A reference picture contains samples that may be used for interpretation in the decoding process of subsequent pictures in the decoding order. An STRP is a picture that has a nuh_layer_id equal to the current picture's nuh_layer_id and is marked to be used for short-term references.

[0130] An example of video parameter set syntax is as follows:

[0131] [Table 4]

[0132] The exemplary video parameter set RBSP semantics are as follows: vps_video_parameter_set_id provides an identifier for the VPS for reference by other syntax elements. vps_max_layer_id specifies the maximum allowable value of nuh_layer_id in each CVS referencing the video parameter set (VPS). Once determined, the value of vps_max_layer_id is expected to remain unchanged when generating the original bitstream, including if the original bitstream is rewritten or if a rewritten bitstream is rewritten again. Otherwise, the picture order count value may be broken, and unexpected behavior may occur. Alternatively, the maximum allowable value of nuh_layer_id is signaled in the SPS instead and referred to as sps_max_layer_id.

[0133] An example of generic slice header semantics is as follows: slice_type specifies the coding type of the slice according to the table below.

[0134] [Table 5]

[0135] Slice_type should be equal to 2 when NalUnitType is a value of NalUnitType within the range IDR_W_RADL~CRA_NUT, including both endpoints, and the current picture is the first picture in the access unit. slice_pic_order_cnt_lsb specifies the value of PicOrderCntVal modulo MaxPicOrderCntLsb for the current picture. The length of the slice_pic_order_cnt_lsb syntax element is log2_max_pic_order_cnt_lsb_minus4+4 bits. The value of slice_pic_order_cnt_lsb should be within the range 0~MaxPicOrderCntLsb-1, including both endpoints. slice_poc_lsb_lt[i][j] specifies the value of PicOrderCntVal modulo MaxPicOrderCntLsb for the j-th LTRP entry in the i-th reference picture list. The length of the `slice_poc_lsb_lt[ i ][ j ]` syntax element is log2_max_pic_order_cnt_lsb_minus4+4 bits. `st_ref_pic_flag[ listIdx ][ rplsIdx ][ i ]` may be set to equal 1 to specify that the i-th entry in the `ref_pic_list_struct( listIdx, rplsIdx )` syntax structure is a non-LTRP entry (STRP entry or ILRP entry). `st_ref_pic_flag[ listIdx ][ rplsIdx ][ i ]` may be set to equal 0 to specify that the i-th entry in the `ref_pic_list_struct( listIdx, rplsIdx )` syntax structure is an LTRP entry. If it does not exist, the value of `st_ref_pic_flag[ listIdx ][ rplsIdx ][ i ]` can be inferred to be equal to 1.

[0136] The variables NumLtrpEntries[ listIdx ][ rplsIdx ] can be derived as follows: for( i = 0, NumLtrpEntries[ listIdx ][ rplsIdx ] = 0; i < num_ref_entries[ listIdx ][ rplsIdx ]; i++ ) if( !st_ref_pic_flag[ listIdx ][ rplsIdx ][ i ] ) (7-87) NumLtrpEntries[ listIdx ][ rplsIdx ]++

[0137] abs_delta_poc_st[ listIdx ][ rplsIdx ][ i ] specifies the absolute difference between the current picture's CrossLayerPoc value and the CrossLayerPoc value of the picture referenced by the i-th entry, when the i-th entry is the first non-LTRP entry in the ref_pic_list_struct( listIdx, rplsIdx ) syntax structure. abs_delta_poc_st[ listIdx ][ rplsIdx ][ i ] specifies the absolute difference between the CrossLayerPoc value of the picture referenced by the i-th entry and the CrossLayerPoc value of the picture referenced by the previous non-LTRP entry in the ref_pic_list_struct( listIdx, rplsIdx ) syntax structure, when the i-th entry is a non-LTRP entry but is not the first non-LTRP entry in the ref_pic_list_struct( listIdx, rplsIdx ) syntax structure. The value of abs_delta_poc_st[ listIdx ][ rplsIdx ][ i ] is 0 to (2, including both end values). 15It may be within the range - 1)*(vps_max_layer_id+1). To specify that the i-th entry in the syntax structure ref_pic_list_struct(listIdx, rplsIdx) has a value of 0 or greater, entry_sign_flag[listIdx][rplsIdx][i] may be set to equal to 1. To specify that the i-th entry in the syntax structure ref_pic_list_struct(listIdx, rplsIdx) has a value less than 0, entry_sign_flag[listIdx][rplsIdx] may be set to equal to 0. If it does not exist, the value of entry_sign_flag[i][j] is presumed to be equal to 1.

[0138] The list DeltaPoc[listIdx][rplsIdx] can be derived as follows: for( i = 0; i < num_ref_entries[ listIdx ][ rplsIdx ]; i++ ) { if( st_ref_pic_flag[ listIdx ][ rplsIdx ][ i ] ) { (7-88) DeltaPoc[ listIdx ][ rplsIdx ][ i ] = ( entry_sign_flag[ listIdx ][ rplsIdx ][ i ]) ? abs_delta_poc_st[ listIdx ][ rplsIdx ][ i ] : 0 - abs_delta_poc_st[ listIdx ][ rplsIdx ][ i ] } }

[0139] rpls_poc_lsb_lt[ listIdx ][ rplsIdx ][ i ] specifies the value of PicOrderCntVal modulo MaxPicOrderCntLsb for the picture referenced by the i-th entry in the ref_pic_list_struct( listIdx, rplsIdx ) syntax structure. The length of the rpls_poc_lsb_lt[ listIdx ][ rplsIdx ][ i ] syntax element is log2_max_pic_order_cnt_lsb_minus4+4 bits.

[0140] An exemplary decoding process for a coded picture is as follows: The decoding process currently operates for the picture CurrPic as follows: Decoding of NAL units is as specified herein. The following decoding process uses syntax elements in the slice header layer and above. Variables and functions related to picture order counting are derived. Such derivations may be called only for the first slice of the picture. For each slice of a non-IDR picture, at the start of the decoding process, the decoding process for reference picture list construction is called for the derivation of reference picture list 0 (RefPicList

[0000] ) and reference picture list 1 (RefPicList

[0001] ). The decoding process for reference picture marking is called. Reference pictures may be marked as not used for reference or as used for long-term reference. This mechanism may be called only for the first slice of the picture. If the picture is currently a CRA picture with NoIncorrectPicOutputFlag equal to 1, or a GRA picture with NoIncorrectPicOutputFlag equal to 1, a decoding process is invoked to generate an unavailable reference picture. This process may be invoked only for the first slice of the picture.

[0141] PictureOutputFlag may be set as follows: PictureOutputFlag is set to 0 if one of the following conditions is true: PictureOutputFlag is set to 0 if the current picture is a RASL picture and the associated IRAP picture's NoIncorrectPicOutputFlag is equal to 1. PictureOutputFlag is set to 0 if gra_enabled_flag is equal to 1 and the current picture is a GRA picture with a NoIncorrectPicOutputFlag equal to 1. PictureOutputFlag is set to 0 if gra_enabled_flag is equal to 1 and the current picture is associated with a GRA picture with a NoIncorrectPicOutputFlag equal to 1 and the current picture's PicOrderCntVal is less than the associated GRA picture's RpPicOrderCntVal. Otherwise, PictureOutputFlag is set to 1. After all slices of the current picture have been decrypted, the current decrypted picture may be marked as to be used for short-term reference, and each ILRP entry in RefPicList

[0000] or RefPicList

[0001] may be marked as to be used for short-term reference.

[0142] An exemplary decoding process for picture order counting is as follows: The output of this process is CrossLayerPoc, which is the picture order count of the current picture. Each coded picture is associated with the picture order count variable shown as CrossLayerPoc. When the current picture is not a CLVSS picture, the variables prevPicOrderCntLsb and prevPicOrderCntMsb may be derived as follows: Let prevTid0Pic be the previous picture in the decoding order, having a nuh_layer_id equal to the current picture's nuh_layer_id and a TemporalId equal to 0, and not being a RASL or RADL picture. The variable prevPicOrderCntLsb may be set to equal slice_pic_order_cnt_lsb of prevTid0Pic. The variable prevPicOrderCntMsb may be set to equal PicOrderCntMsb of prevTid0Pic. The current picture variable PicOrderCntMsb can be derived as follows: If the current picture is a CLVSS picture, PicOrderCntMsb can be set to equal to 0. Otherwise, PicOrderCntMsb can be derived as follows: if( ( slice_pic_order_cnt_lsb < prevPicOrderCntLsb ) && ( ( prevPicOrderCntLsb - slice_pic_order_cnt_lsb ) >= ( MaxPicOrderCntLsb / 2 ) ) ) PicOrderCntMsb = prevPicOrderCntMsb + MaxPicOrderCntLsb else if( (slice_pic_order_cnt_lsb > prevPicOrderCntLsb ) && ( ( slice_pic_order_cnt_lsb - prevPicOrderCntLsb ) > ( MaxPicOrderCntLsb / 2 ) ) ) PicOrderCntMsb = prevPicOrderCntMsb - MaxPicOrderCntLsb else PicOrderCntMsb = prevPicOrderCntMsb

[0143] PicOrderCntVal can be derived as follows: PicOrderCntVal = PicOrderCntMsb + slice_pic_order_cnt_lsb For CLVSS pictures, when PicOrderCntMsb is set to equal 0, all CLVSS pictures may have PicOrderCntVal set to equal slice_pic_order_cnt_lsb. The value of PicOrderCntVal is -2 including both ends. 31 ~2 31 It may be within the range of -1. Within a single CVS, the PicOrderCntVal values ​​for any two coded pictures with the same nuh_layer_id value do not have to be the same. All pictures within any particular access unit may have the same PicOrderCntVal value.

[0144] The variable CrossLayerPoc can be derived as follows: CrossLayerPoc = PicOrderCntVal * ( vps_max_layer_id + 1 ) + nuh_layer_id The function PicOrderCnt(picX) may be specified as follows: PicOrderCnt(picX) = PicOrderCntVal of picture picX The function DiffPicOrderCnt(picA, picB) may be specified as follows: DiffPicOrderCnt( picA, picB ) = PicOrderCnt( picA ) -PicOrderCnt( picB ) The bitstream contains the values ​​at both ends -2 15 ~2 15 Data that does not fall within the range of -1 and results in a value for DiffPicOrderCnt(picA, picB) used in the decoding process does not need to be included. Let the current picture be X, and let Y and Z be two other pictures in the same CVS. When both DiffPicOrderCnt(X, Y) and DiffPicOrderCnt(X, Z) are positive or both are negative, Y and Z may be considered to have the same output order direction from X.

[0145] An exemplary decoding process for constructing a reference picture list is as follows. This process may be invoked at the start of the decoding process for each slice of non-IDR picture. Reference pictures are addressed through a reference index, which is an index to the reference picture list. When decoding an I slice, the reference picture list is not used in decoding the slice data. When decoding a P slice, only reference picture list 0 (RefPicList

[0000] ) is used in decoding the slice data. When decoding a B slice, both reference picture list 0 and reference picture list 1 (RefPicList

[0001] ) are used in decoding the slice data. At the start of the decoding process for each slice of non-IDR picture, reference picture lists RefPicList

[0000] and RefPicList

[0001] are derived. The reference picture lists may be used in marking reference pictures or in decoding slice data. For I slices of non-IDR pictures that are not the first slice of a picture, RefPicList

[0000] and RefPicList

[0001] may be derived for the purpose of bitstream conformance checking. However, their derivation is not required for decoding the current picture or pictures that follow the current picture in the decoding order. For P slices that are not the first slice of a picture, RefPicList

[0001] may be derived for the purpose of bitstream conformance checking. However, the derivation of RefPicList

[0001] is not required for decoding the current picture or pictures that follow the current picture in the decoding order. The reference picture lists RefPicList

[0000] and RefPicList

[0001] may be configured as follows: for( i = 0; i < 2; i++ ) { for( j = 0, k = 0, pocBase = CrossLayerPoc; j < num_ref_entries[ i ][ RplsIdx[ i ] ]; j++) { if( st_ref_pic_flag[ i ][ RplsIdx[ i ] ][ j ] ) { RefPicPocList[ i ][ j ] = pocBase - DeltaPoc[ i ][ RplsIdx[ i ] ][ j ] if (the reference picture picA in the DPB has a CrossLayerPoc equal to RefPicPocList[i][j]) RefPicList[ i ][ j ] = picA else RefPicList[i][j] = "No reference picture found" (8-5) pocBase = RefPicPocList[ i ][ j ] else { if( !delta_poc_msb_cycle_lt[ i ][ k ] ) { if (currently has the same nuh_layer_id as the picture, and PicOrderCntVal & ( MaxPicOrderCntLsb - 1 ) is equal to PocLsbLt[ i ][ k ], and reference picA is in DPB) RefPicList[ i ][ j ] = picA else RefPicList[i][j] = "No reference picture found" else { if (there is a reference picA in the DPB that has the same nuh_layer_id as the current picture and a PicOrderCntVal equal to FullPocLt[i][RplsIdx[i]][k]) RefPicList[ i ][ j ] = picA else RefPicList[i][j] = "No reference picture found" } k++ } } }

[0146] For each i equal to 0 or 1, the first NumRefIdxActive[i] entries in RefPicList[i] are referred to as active entries in RefPicList[i], and the other entries in RefPicList[i] are referred to as inactive entries in RefPicList[i]. If the picture referenced by an entry has a nuh_layer_id with a different value than the current picture, the entry in the referenced picture list may be referred to as an ILRP entry. A particular picture can be referenced by both an entry in RefPicList

[0000] and an entry in RefPicList

[0001] . A particular picture can also be referenced by two or more entries in RefPicList

[0000] or by two or more entries in RefPicList

[0001] . Active entries in RefPicList

[0000] and RefPicList

[0001] refer collectively to all reference pictures that may be used for interpretation of the current picture and one or more pictures that follow the current picture in the decoding order. Inactive entries in RefPicList

[0000] and RefPicList

[0001] refer collectively to all reference pictures that are not used for interpretation of the current picture but may be used for interpretation of one or more pictures that follow the current picture in the decoding order. There may be one or more entries in RefPicList

[0000] or RefPicList

[0001] that are not equal to any reference picture because the corresponding picture does not exist in the DPB. Each inactive entry in RefPicList

[0000] or RefPicList

[0000] that is not equal to any reference picture may be ignored. Accidental picture loss can be inferred for each active entry in RefPicList

[0000] or RefPicList

[0001] that is not equal to any reference picture.

[0147] Bitstream conformance may require the following constraints to apply: For each i equal to 0 or 1, num_ref_entries[i][RplsIdx[i]] does not have to be less than NumRefIdxActive[i]. The picture referenced by each active entry in RefPicList

[0000] or RefPicList

[0001] may exist in the DPB and may have a TemporalId less than or equal to the TemporalId of the current picture. The picture referenced by each entry in RefPicList

[0000] or RefPicList

[0001] does not have to be the current picture. STRP entries in RefPicList

[0000] or RefPicList

[0001] for a slice of a picture, and LTRP entries in RefPicList

[0000] or RefPicList

[0001] for the same or different slices of the same picture, do not have to reference the same picture. There does not need to be any LTRP entries in RefPicList

[0000] or RefPicList

[0001] where the difference between the PicOrderCntVal of the current picture and the PicOrderCntVal of the picture referenced by the entry is 224 or more. setOfRefPics is the set of unique pictures referenced by all entries in RefPicList

[0000] that have the same nuh_layer_id as the current picture, and all entries in RefPicList

[0001] that have the same nuh_layer_id as the current picture. The number of pictures in setOfRefPics may be less than or equal to sps_max_dec_pic_buffering_minus1, and setOfRefPics may be the same for all slices of a picture. Pictures referenced by each ILRP entry in RefPicList

[0000] or RefPicList

[0001] of the slice of the current picture may exist in the DPB and may be in the same access unit as the current picture.The pictures referenced by each ILRP entry in RefPicList

[0000] or RefPicList

[0001] of the current picture slice may have a nuh_layer_id smaller than the current picture's nuh_layer_id. Each ILRP entry in RefPicList

[0000] or RefPicList

[0001] of the slice may be an active entry.

[0148] An exemplary decoding process for reference picture marking is as follows: This process may be called once per picture. This may be performed after the decoding of the slice header and the decoding process for constructing the reference picture list for the slice, but before decoding the slice data. This process may result in one or more reference pictures in the DPB being marked as either not used for reference or used for long-term reference. Decoded pictures in the DPB may be marked as either not used for reference, used for short-term reference, or used for long-term reference. Decoded pictures in the DPB may be marked as only one of these three at any given moment during the operation of the decoding process. Assigning one of these markings to a picture implicitly removes another of these markings when applicable. When a picture is referred to as being marked as being used for reference, this collectively refers to the picture being marked as being used for either short-term reference or long-term reference (but not both). STRPs are identified by their nuh_layer_id and PicOrderCntVal values. LTRPs are identified by their nuh_layer_id values ​​and Log2(MaxLtPicOrderCntLsb) LSBs of their PicOrderCntVal values. If the current picture is a CLVSS picture, all referenced pictures in the current DPB (if any) that have the same nuh_layer_id as the current picture may be marked as not to be used for reference. Otherwise, the following applies: For each LTRP entry in RefPicList

[0000] or RefPicList

[0001] , if the referenced picture is a STRP with the same nuh_layer_id as the current picture, the referenced picture is marked as to be used for long-term reference.Each referenced picture in the DPB that is not referenced by any entry in RefPicList

[0000] or RefPicList

[0001] and currently has the same nuh_layer_id as the picture may be marked as not to be used for reference. For each ILRP entry in RefPicList

[0000] or RefPicList

[0001] , the referenced picture may be marked as to be used for long-term reference.

[0149] A third exemplary implementation of the method described above is explained below. An example of the definition is as follows: An ILRP is a picture in the same access unit as the current picture, has a nuh_layer_id smaller than the current picture's nuh_layer_id, and is marked to be used for long-term reference. An LTRP is a picture that has a nuh_layer_id equal to the current picture's nuh_layer_id and is marked to be used for long-term reference. A reference picture is a picture that is a short-term reference picture, a long-term reference picture, or an inter-layer reference picture. A reference picture contains samples that may be used for interpretation in the decoding process of subsequent pictures in the decoding order. An STRP is a picture that has a nuh_layer_id equal to the current picture's nuh_layer_id and is marked to be used for short-term reference.

[0150] An example of generic slice header semantics is as follows: slice_type can specify the coding type of the slice according to the table below.

[0151] [Table 6]

[0152] If NalUnitType is a value within the range IDR_W_RADL~CRA_NUT, which includes both endpoints, and the current picture is the first picture in the access unit, then Slice_type may be set to equal 2.

[0153] An exemplary decoding process for a coded picture is as follows: The decoding process currently operates for the picture CurrPic as follows: Decoding of NAL units is as specified herein. The following decoding process uses syntax elements in the slice header layer and above. Variables and functions related to picture order counting are derived. Such derivations may be called only for the first slice of the picture. For each slice of a non-IDR picture, at the start of the decoding process, the decoding process for reference picture list construction is called for the derivation of reference picture list 0 (RefPicList

[0000] ) and reference picture list 1 (RefPicList

[0001] ). The decoding process for reference picture marking is called. Reference pictures may be marked as not used for reference or as used for long-term reference. This mechanism may be called only for the first slice of the picture. If the picture is currently a CRA picture with NoIncorrectPicOutputFlag equal to 1, or a GRA picture with NoIncorrectPicOutputFlag equal to 1, a decoding process is invoked to generate an unavailable reference picture. This process may be invoked only for the first slice of the picture.

[0154] PictureOutputFlag may be set as follows: PictureOutputFlag is set to 0 if one of the following conditions is true: PictureOutputFlag is set to 0 if the current picture is a RASL picture and the associated IRAP picture's NoIncorrectPicOutputFlag is equal to 1. PictureOutputFlag is set to 0 if gra_enabled_flag is equal to 1 and the current picture is a GRA picture with a NoIncorrectPicOutputFlag equal to 1. PictureOutputFlag is set to 0 if gra_enabled_flag is equal to 1 and the current picture is associated with a GRA picture with a NoIncorrectPicOutputFlag equal to 1 and the current picture's PicOrderCntVal is less than the associated GRA picture's RpPicOrderCntVal. Otherwise, PictureOutputFlag is set to 1. After all slices of the current picture have been decrypted, the current decrypted picture may be marked as to be used for short-term reference, and each ILRP entry in RefPicList

[0000] or RefPicList

[0001] may be marked as to be used for short-term reference.

[0155] An exemplary decoding process for picture order counting is as follows: The output of this process is PicOrderCntVal, which is the picture order count of the current picture. Each coded picture may be associated with a picture order count variable, indicated as PicOrderCntVal. When the current picture is not a CLVSS picture, which is the first picture in the access unit in the decoding order, the variables prevPicOrderCntLsb and prevPicOrderCntMsb may be derived as follows: Let prevTid0Pic be the previous picture in the decoding order, which has a nuh_layer_id less than or equal to the current picture's nuh_layer_id and a TemporalId equal to 0, and is not a RASL picture or a RADL picture. The variable prevPicOrderCntLsb may be set to equal slice_pic_order_cnt_lsb of prevTid0Pic. The variable prevPicOrderCntMsb may be set to equal PicOrderCntMsb of prevTid0Pic. The current picture variable PicOrderCntMsb may be derived as follows: If the current picture is a CLVSS picture which is the first picture in the access unit in the decoding order, PicOrderCntMsb may be set to equal to 0. Otherwise, PicOrderCntMsb is derived as follows: if( ( slice_pic_order_cnt_lsb < prevPicOrderCntLsb ) && ( ( prevPicOrderCntLsb - slice_pic_order_cnt_lsb ) >= ( MaxPicOrderCntLsb / 2 ) ) ) PicOrderCntMsb = prevPicOrderCntMsb + MaxPicOrderCntLsb else if( (slice_pic_order_cnt_lsb > prevPicOrderCntLsb ) && ( ( slice_pic_order_cnt_lsb - prevPicOrderCntLsb ) > ( MaxPicOrderCntLsb / 2 ) ) ) PicOrderCntMsb = prevPicOrderCntMsb - MaxPicOrderCntLsb else PicOrderCntMsb = prevPicOrderCntMsb

[0156] PicOrderCntVal may be derived as follows. PicOrderCntVal = PicOrderCntMsb + slice_pic_order_cnt_lsb After PicOrderCntMsb is set equal to 0, each CLVSS picture that is the first picture in the access unit in decoding order may have a PicOrderCntVal set equal to slice_pic_order_cnt_lsb. The value of PicOrderCntVal may be in the range of -2 31 ~2 31 -1, inclusive. Within one CVS, the PicOrderCntVal values for any two coded pictures need not be the same. The function PicOrderCnt( picX ) may be specified as follows. PicOrderCnt( picX ) = PicOrderCntVal of picture picX The function DiffPicOrderCnt( picA, picB ) may be specified as follows. DiffPicOrderCnt( picA, picB ) = PicOrderCnt( picA ) - PicOrderCnt( picB ) The bitstream is in the range of -2 15 ~2 15Data that does not fall within the range of -1 and results in a value for DiffPicOrderCnt(picA, picB) used in the decoding process does not need to be included. Let the current picture be X, and let Y and Z be two other pictures in the same CVS. When both DiffPicOrderCnt(X, Y) and DiffPicOrderCnt(X, Z) are positive or both are negative, Y and Z may be considered to have the same output order direction from X.

[0157] An exemplary decoding process for constructing a reference picture list is as follows. This process may be called at the start of the decoding process for each slice of non-IDR picture. Reference pictures are addressed through a reference index, which is an index to the reference picture list. When decoding an I slice, the reference picture list is not used in decoding the slice data. When decoding a P slice, only reference picture list 0 (RefPicList

[0000] ) is used in decoding the slice data. When decoding a B slice, both reference picture list 0 and reference picture list 1 (RefPicList

[0001] ) are used in decoding the slice data. At the start of the decoding process for each slice of non-IDR picture, reference picture lists RefPicList

[0000] and RefPicList

[0001] are derived. The reference picture lists are used in marking reference pictures or in decoding slice data. For I slices of non-IDR pictures that are not the first slice of the picture, RefPicList

[0000] and RefPicList

[0001] may be derived for the purpose of bitstream conformance checking. Their derivation is not required for decoding the current picture or pictures that follow the current picture in the decoding order. For P slices that are not the first slice of the picture, RefPicList

[0001] may be derived for the purpose of bitstream conformance checking. However, such derivation is not required for decoding the current picture or pictures that follow the current picture in the decoding order. The reference picture lists RefPicList

[0000] and RefPicList

[0001] may be constructed as follows: for( i = 0; i < 2; i++ ) { for( j = 0, k = 0, pocBase = PicOrderCntVal; j < num_ref_entries[ i ][ RplsIdx[ i ] ]; j++) { if( st_ref_pic_flag[ i ][ RplsIdx[ i ] ][ j ] ) { RefPicPocList[ i ][ j ] = pocBase - DeltaPocSt[ i ][ RplsIdx[ i ] ][ j ] if (the reference picture picA has a PicOrderCntVal equal to RefPicPocList[i][j] in the DPB) RefPicList[ i ][ j ] = picA else RefPicList[i][j] = "No reference picture found" (8-5) pocBase = RefPicPocList[ i ][ j ] else { if( !delta_poc_msb_cycle_lt[ i ][ k ] ) { if (PicOrderCntVal & ( MaxPicOrderCntLsb - 1 ) is equal to PocLsbLt[ i ][ k ] and a reference picA exists in DPB) RefPicList[ i ][ j ] = picA else RefPicList[i][j] = "No reference picture found" else { if (there is a reference picA in DPB that has a PicOrderCntVal equal to FullPocLt[i][k]) RefPicList[ i ][ j ] = picA else RefPicList[i][j] = "No reference picture found" } k++ } } }

[0158] For each i equal to 0 or 1, the first NumRefIdxActive[i] entries in RefPicList[i] are referred to as active entries in RefPicList[i], and the other entries in RefPicList[i] are referred to as inactive entries in RefPicList[i]. If the picture referenced by an entry has a nuh_layer_id with a different value than the current picture, the entry in the referenced picture list may be referred to as an ILRP entry. A particular picture can be referenced by both an entry in RefPicList

[0000] and an entry in RefPicList

[0001] . A particular picture can also be referenced by two or more entries in RefPicList

[0000] or by two or more entries in RefPicList

[0001] . Active entries in RefPicList

[0000] and RefPicList

[0001] may collectively refer to all reference pictures that can be used for interpretation of the current picture and one or more pictures that follow the current picture in the decoding order. Inactive entries in RefPicList

[0000] and RefPicList

[0001] may collectively refer to all reference pictures that are not used for interpretation of the current picture but can be used for interpretation of one or more pictures that follow the current picture in the decoding order. There may be one or more entries in RefPicList

[0000] or RefPicList

[0001] that are not equal to any reference picture because there is no corresponding picture in the DPB. Each inactive entry in RefPicList

[0000] or RefPicList

[0000] that is not equal to any reference picture may be ignored. Accidental picture loss can be inferred for each active entry in RefPicList

[0000] or RefPicList

[0001] that is not equal to any reference picture.

[0159] The following constraints may apply to bitstream conformance: For each i equal to 0 or 1, num_ref_entries[i][RplsIdx[i]] does not have to be less than NumRefIdxActive[i]. A picture referenced by each active entry in RefPicList

[0000] or RefPicList

[0001] may exist in the DPB and may have a TemporalId less than or equal to the TemporalId of the current picture. A picture referenced by each entry in RefPicList

[0000] or RefPicList

[0001] does not have to be the current picture. STRP entries in RefPicList

[0000] or RefPicList

[0001] of a slice of picture, and LTRP entries in RefPicList

[0000] or RefPicList

[0001] of the same or different slices of the same picture do not have to reference the same picture. There does not need to be any LTRP entries in RefPicList

[0000] or RefPicList

[0001] where the difference between the PicOrderCntVal of the current picture and the PicOrderCntVal of the picture referenced by the entry is 224 or more. setOfRefPics is the set of unique pictures referenced by all entries in RefPicList

[0000] that have the same nuh_layer_id as the current picture, and all entries in RefPicList

[0001] that have the same nuh_layer_id as the current picture. The number of pictures in setOfRefPics may be less than or equal to sps_max_dec_pic_buffering_minus1, and setOfRefPics may be the same for all slices of the picture. The pictures referenced by each ILRP entry in RefPicList

[0000] or RefPicList

[0001] of the slice of the current picture may be in the same access unit as the current picture.The pictures referenced by each ILRP entry in the current picture slice's RefPicList

[0000] or RefPicList

[0001] may exist in the DPB and may have a nuh_layer_id smaller than the current picture's nuh_layer_id. Each ILRP entry in the slice's RefPicList

[0000] or RefPicList

[0001] may be an active entry.

[0160] An exemplary decoding process for reference picture marking is as follows: This process may be called once per picture after decoding the slice header and the decoding process for constructing the reference picture list for the slice. The process may also be called before decoding the slice data. This process may result in one or more reference pictures in the DPB being marked as either not used for reference or used for long-term reference. Decoded pictures in the DPB may be marked as either not used for reference, used for short-term reference, or used for long-term reference. Decoded pictures in the DPB may be marked as only one of these three at any given moment during the operation of the decoding process. Assigning one of these markings to a picture implicitly removes another of these markings when applicable. When a picture is referred to as being marked as being used for reference, this collectively refers to the picture being marked as being used for either short-term reference or long-term reference (but not both). STRPs and ILRPs may be identified by their nuh_layer_id and PicOrderCntVal value. LTRPs may be identified by their nuh_layer_id value and Log2(MaxLtPicOrderCntLsb) LSBs of their PicOrderCntVal value. If the current picture is a CLVSS picture, all referenced pictures in the current DPB (if any) that have the same nuh_layer_id as the current picture may be marked as not to be used for reference. Otherwise, the following applies: For each LTRP entry in RefPicList

[0000] or RefPicList

[0001] , if the referenced picture is a STRP with the same nuh_layer_id as the current picture, the picture is marked as to be used for long-term reference.Each referenced picture that has the same nuh_layer_id as the current picture in the DPB and is not referenced by any entry in RefPicList

[0000] or RefPicList

[0001] may be marked as not to be used for reference. For each ILRP entry in RefPicList

[0000] or RefPicList

[0001] , the referenced picture may be marked as to be used for long-term reference.

[0161] A fourth exemplary implementation of the method described above is described below. An exemplary decoding process for picture order counting is as follows: The output of this process is PicOrderCntVal, which is the picture order count of the current picture. Each coded picture is associated with a picture order count variable, indicated as PicOrderCntVal. When the current picture is not a CLVSS picture, the variables prevPicOrderCntLsb and prevPicOrderCntMsb may be derived as follows: Let prevTid0Pic be the previous picture in the decoding order, having a nuh_layer_id less than or equal to the current picture's nuh_layer_id and a TemporalId equal to 0, and not being a RASL or RADL picture. The variable prevPicOrderCntLsb may be set to equal slice_pic_order_cnt_lsb of prevTid0Pic. The variable prevPicOrderCntMsb may be set to equal PicOrderCntMsb of prevTid0Pic. The current picture variable PicOrderCntMsb can be derived as follows: If the current picture is a CLVSS picture, PicOrderCntMsb can be set to equal to 0. Otherwise, PicOrderCntMsb can be derived as follows: if( ( slice_pic_order_cnt_lsb < prevPicOrderCntLsb ) && ( ( prevPicOrderCntLsb - slice_pic_order_cnt_lsb ) >= ( MaxPicOrderCntLsb / 2 ) ) ) PicOrderCntMsb = prevPicOrderCntMsb + MaxPicOrderCntLsb else if( (slice_pic_order_cnt_lsb > prevPicOrderCntLsb ) && ( ( slice_pic_order_cnt_lsb - prevPicOrderCntLsb ) > ( MaxPicOrderCntLsb / 2 ) ) ) PicOrderCntMsb = prevPicOrderCntMsb - MaxPicOrderCntLsb else PicOrderCntMsb = prevPicOrderCntMsb

[0162] PicOrderCntVal can be derived as follows: PicOrderCntVal = PicOrderCntMsb + slice_pic_order_cnt_lsb For CLVSS pictures, after PicOrderCntMsb is set to equal to 0, all CLVSS pictures may have PicOrderCntVal equal to slice_pic_order_cnt_lsb. The value of PicOrderCntVal is -2 including both ends. 31 ~2 31 It may be within the range of -1. Within a single CVS, the PicOrderCntVal values ​​for any two coded pictures do not have to be the same. The function PicOrderCnt(picX) may be specified as follows: PicOrderCnt(picX) = PicOrderCntVal of picture picX The function DiffPicOrderCnt(picA, picB) may be specified as follows: DiffPicOrderCnt( picA, picB ) = PicOrderCnt( picA ) -PicOrderCnt( picB ) The bitstream contains the values ​​at both ends -215 ~2 15 Data that does not fall within the range of -1 and would result in a value for DiffPicOrderCnt(picA, picB) used in the decoding process does not need to be included. Let the current picture be X, and two other pictures in the same CVS be Y and Z. When both DiffPicOrderCnt(X, Y) and DiffPicOrderCnt(X, Z) are positive or both are negative, Y and Z are considered to have the same output order direction from X.

[0163] An exemplary decoding process for constructing a reference picture list is as follows. This process may be invoked at the start of the decoding process for each slice of non-IDR picture. Reference pictures are addressed through a reference index, which is an index to the reference picture list. When decoding an I slice, the reference picture list is not used in decoding the slice data. When decoding a P slice, only reference picture list 0 (RefPicList

[0000] ) is used in decoding the slice data. When decoding a B slice, both reference picture list 0 and reference picture list 1 (RefPicList

[0001] ) are used in decoding the slice data. Reference picture lists RefPicList

[0000] and RefPicList

[0001] may be derived at the start of the decoding process for each slice of non-IDR picture. The reference picture lists may be used in marking reference pictures or in decoding slice data. For I slices of a non-IDR picture that are not the first slice of the picture, RefPicList

[0000] and RefPicList

[0001] may be derived for the purpose of bitstream conformance checking. Such derivation is not required for decoding the current picture or pictures that follow the current picture in the decoding order. For P slices that are not the first slice of the picture, RefPicList

[0001] may be derived for the purpose of bitstream conformance checking. However, such derivation is not required for decoding the current picture or pictures that follow the current picture in the decoding order.

[0164] The reference picture lists RefPicList

[0000] and RefPicList

[0001] may be configured as follows: for( i = 0; i < 2; i++ ) { for( j = 0, k = 0, pocBase = PicOrderCntVal; j < num_ref_entries[ i ][ RplsIdx[ i ] ]; j++) { if( st_ref_pic_flag[ i ][ RplsIdx[ i ] ][ j ] ) { RefPicPocList[ i ][ j ] = pocBase - DeltaPocSt[ i ][ RplsIdx[ i ] ][ j ] if (the reference picture picA has a PicOrderCntVal equal to RefPicPocList[i][j] in the DPB) RefPicList[ i ][ j ] = picA else RefPicList[i][j] = "No reference picture found" (8-5) pocBase = RefPicPocList[ i ][ j ] else { if( !delta_poc_msb_cycle_lt[ i ][ k ] ) { if (PicOrderCntVal & ( MaxPicOrderCntLsb - 1 ) is equal to PocLsbLt[ i ][ k ] and a reference picA exists in DPB) RefPicList[ i ][ j ] = picA else RefPicList[i][j] = "No reference picture found" else { if (there is a reference picA in DPB that has a PicOrderCntVal equal to FullPocLt[i][k]) RefPicList[ i ][ j ] = picA else RefPicList[i][j] = "No reference picture found" } k++ } } }

[0165] For each i equal to 0 or 1, the first NumRefIdxActive[i] entries in RefPicList[i] are referred to as active entries in RefPicList[i], and the other entries in RefPicList[i] are referred to as inactive entries in RefPicList[i]. A particular picture can be referred to by both entries in RefPicList

[0000] and entries in RefPicList

[0001] . A particular picture can also be referred to by two or more entries in RefPicList

[0000] or by two or more entries in RefPicList

[0001] . Active entries in RefPicList

[0000] and active entries in RefPicList

[0001] may collectively refer to all reference pictures that can be used for interpretation of the current picture and one or more pictures that follow the current picture in decoding order. Inactive entries in RefPicList

[0000] and RefPicList

[0001] may collectively refer to all reference pictures that are not currently used for interpretation of the picture but may be used for interpretation of one or more pictures that follow the current picture in the decoding order. There may be one or more entries in RefPicList

[0000] or RefPicList

[0001] that are not equal to any reference picture because the corresponding picture does not exist in the DPB. Each inactive entry in RefPicList

[0000] or RefPicList

[0000] that is not equal to any reference picture may be ignored. For each active entry in RefPicList

[0000] or RefPicList

[0001] that is not equal to any reference picture, an accidental picture loss may be inferred.

[0166] Bitstream conformance may require the following constraints to apply: For each i equal to 0 or 1, num_ref_entries[i][RplsIdx[i]] does not have to be less than NumRefIdxActive[i]. The picture referenced by each active entry in RefPicList

[0000] or RefPicList

[0001] may exist in the DPB and may have a TemporalId less than or equal to the TemporalId of the current picture. The picture referenced by each entry in RefPicList

[0000] or RefPicList

[0001] does not have to be the current picture. STRP entries in RefPicList

[0000] or RefPicList

[0001] for a slice of a picture, and LTRP entries in RefPicList

[0000] or RefPicList

[0001] for the same or different slices of the same picture, do not have to reference the same picture. There does not need to be any LTRP entries in RefPicList

[0000] or RefPicList

[0001] where the difference between the current picture's PicOrderCntVal and the PicOrderCntVal of the picture referenced by the entry is 224 or more. SetOfRefPics is the set of unique pictures referenced by all entries in RefPicList

[0000] and all entries in RefPicList

[0001] . The number of pictures in SetOfRefPics may be less than or equal to sps_max_dec_pic_buffering_minus1, and SetOfRefPics may be the same for all slices of a picture. Each picture referenced by an active entry in RefPicList

[0000] or RefPicList

[0001] may exist in the DPB and may have a nuh_layer_id less than or equal to the current picture's nuh_layer_id.

[0167] An exemplary decoding process for reference picture marking is as follows: This process may be called once per picture after decoding the slice header and the decoding process for constructing the reference picture list for the slice. The process may be called before decoding the slice data. This process may result in one or more reference pictures in the DPB being marked as not used for reference or used for long-term reference. Decoded pictures in the DPB may be marked as not used for reference, used for short-term reference, or used for long-term reference. Decoded pictures in the DPB may be marked as only one of these three at any given moment during the operation of the decoding process. Assigning one of these markings to a picture implicitly removes another of these markings when applicable. When a picture is referred to as being marked as being used for reference, this collectively refers to the picture being marked as being used for either short-term reference or long-term reference (but not both). STRPs may be identified by their PicOrderCntVal values. LTRPs may be identified by Log2(MaxLtPicOrderCntLsb) LSBs of their PicOrderCntVal values. If the current picture is a CLVSS picture, all referenced pictures in the current DPB (if any) may be marked as not to be used for reference. Otherwise, the following applies: For each LTRP entry in RefPicList

[0000] or RefPicList

[0001] , if the referenced picture is a STRP, the referenced picture is marked as to be used for long-term reference. Each referenced picture in the DPB that is not referenced by any entry in RefPicList

[0000] or RefPicList

[0001] is marked as not to be used for reference.

[0168] Figure 10 is a schematic diagram of an exemplary video coding device 1000. The video coding device 1000 is suitable for carrying out the disclosed examples / embodiments, such as those described herein. The video coding device 1000 comprises a downstream port 1020, an upstream port 1050, and a transceiver unit (Tx / Rx) 1010 including a transmitter and / or receiver for communicating data upstream and / or downstream over a network. The video coding device 1000 also includes a processor 1030 including a logic unit and / or a central processing unit (CPU) for processing data, and memory 1032 for storing data. The video coding device 1000 may also include electrical components, optical-electrical (OE) components, electro-optical (EO) components, and / or wireless communication components coupled to the upstream port 1050 and / or downstream port 1020 for communicating data over a telecommunications network, an optical communication network, or a wireless communication network. The video coding device 1000 may also include an input and / or output (I / O) device 1060 for communicating data with the user. The I / O device 1060 may include an output device, such as a display for showing video data or a speaker for outputting audio data. The I / O device 1060 may also include an input device, such as a keyboard, mouse, or trackball, and / or a corresponding interface for interacting with such an output device.

[0169] The processor 1030 is implemented by hardware and software. The processor 1030 may be implemented as one or more CPU chips, cores (e.g., a multicore processor), field-programmable gate arrays (FPGAs), application-specific integrated circuits (ASICs), and digital signal processors (DSPs). The processor 1030 communicates with downstream port 1020, Tx / Rx 1010, upstream port 1050, and memory 1032. The processor 1030 includes a coding module 1014. The coding module 1014 implements embodiments disclosed herein, such as methods 100, 1100, and / or 1200, which may employ a bitstream 900 containing an RPL structure 800 and a picture that can be coded according to unidirectional interpretation 500, bidirectional interpretation 600, and / or layer-based prediction 700. The coding module 1014 may also implement any other methods / mechanisms described herein. Furthermore, the coding module 1014 may implement the codec system 200, encoder 300, and / or decoder 400. For example, the coding module 1014 may be employed to code ILRP flags and / or ILRP layer indicators within the reference picture structure in order to manage the reference picture to support inter-layer prediction as described above. Thus, the coding module 1014 provides additional functionality and / or coding efficiency to the video coding device 1000 when coding video data. Thus, the coding module 1014 improves the functionality of the video coding device 1000 and addresses problems specific to video coding techniques. Furthermore, the coding module 1014 influences the transformation of the video coding device 1000 to different states. Alternatively, the coding module 1014 may be implemented as instructions stored in memory 1032 (for example, as a computer program product stored on a non-temporary medium) and executed by the processor 1030.

[0170] Memory 1032 comprises one or more memory types, such as disks, tape drives, solid-state drives, read-only memory (ROM), random-access memory (RAM), flash memory, ternary associative memory (TCAM), and static random-access memory (SRAM). Memory 1032 can be used as an overflow data storage device for storing such programs when they are selected for execution, and for storing instructions and data read during program execution.

[0171] Figure 11 is a flowchart of an exemplary method 1100 for encoding a video sequence into a bitstream such as bitstream 900 according to inter-layer prediction. Method 1100 can be employed by an encoder such as a codec system 200, an encoder 300, and / or a video coding device 1000 when performing method 100 for encoding a picture according to unidirectional inter-prediction 500, bidirectional inter-prediction 600, and / or layer-based prediction 700 by employing an RPL structure 800.

[0172] Method 1100 may begin when an encoder receives a video sequence containing multiple pictures and, for example, based on user input, determines that the video sequence should be encoded into a bitstream. In step 1101, the encoder encodes the current picture into a bitstream. For example, the current picture may be encoded according to an inter-layer prediction based on an inter-layer reference picture. For example, such an inter-layer prediction may be performed according to an inter-layer prediction 721. As described above, the inter-layer reference picture may be in the same AU as the current picture. Therefore, the inter-layer reference picture may contain the same POC as the current picture. Furthermore, the inter-layer reference picture is located in a different layer than the current picture. For example, the inter-layer reference picture may be associated with a lower layer than the current picture. Therefore, the inter-layer reference picture may be associated with a lower layer ID than the current picture.

[0173] In step 1103, the encoder can encode a reference picture list structure, such as RPL structure 800, into the bitstream. The reference picture list structure has multiple entries for multiple reference pictures. Such entries include entries currently associated with the picture. The entries indicate cross-layer reference pictures. For example, the reference picture list structure may be represented as ref_pic_list_struct( listIdx, rplsIdx ), where listIdx identifies the reference picture list, rplsIdx identifies the entries in the reference picture list, and ref_pic_list_struct is a syntax structure that returns entries based on listIdx and rplsIdx.

[0174] In step 1105, the encoder may encode an interlayer reference picture flag into the bitstream. The interlayer reference picture flag indicates that the entry currently associated with the picture is an ILRP entry. For example, the interlayer reference picture flag may be represented as inter_layer_ref_pic_flag[ listIdx ][ rplsIdx ][ i ]. Specifically, when the i-th entry in ref_pic_list_struct( listIdx, rplsIdx ) is an ILRP entry, inter_layer_ref_pic_flag[ listIdx ][ rplsIdx ][ i ] may be set to equal to 1. Furthermore, when the i-th entry in ref_pic_list_struct( listIdx, rplsIdx ) is not an ILRP entry, inter_layer_ref_pic_flag[ listIdx ][ rplsIdx ][ i ] may be set to equal to 0. For example, ref_pic_list_struct( listIdx, rplsIdx ) and inter_layer_ref_pic_flag[ listIdx ][ rplsIdx ][ i ] may be encoded in the bitstream within the SPS. In another example, ref_pic_list_struct( listIdx, rplsIdx ) and inter_layer_ref_pic_flag[ listIdx ][ rplsIdx ][ i ] may be encoded in the bitstream within a header associated with the current picture, such as a slice header and / or a picture header.

[0175] In step 1107, the encoder may encode the ILRP layer indicator into the bitstream. The ILRP layer indicator indicates the layer of the inter-layer reference picture. For example, the ILRP layer indicator may indicate one or more layers for each entry in the reference picture list structure associated with the inter-layer reference picture, as indicated by the inter-layer reference picture flag.

[0176] In step 1109, the encoder can store a bitstream for communication to the decoder, for example, for communication on request.

[0177] Figure 12 is a flowchart of an exemplary method for decoding a video sequence from a bitstream such as bitstream 900 when employing interlayer prediction. Method 1200 may be employed by a decoder such as a codec system 200, decoder 400, and / or video coding device 1000 when performing Method 100 for decoding a picture according to unidirectional interpretation 500, bidirectional interpretation 600, and / or layer-based prediction 700 by employing an RPL structure 800.

[0178] For example, Method 1200 may begin when, as a result of Method 1100, the decoder begins receiving a bitstream of encoded data representing a video sequence. In step 1201, the decoder receives a bitstream. The bitstream may comprise a current picture, a reference picture list structure, an inter-layer reference picture flag, and / or an ILRP layer indicator. For example, the reference picture list structure may comprise an inter-layer reference picture flag and / or an ILRP layer indicator.

[0179] In step 1203, the decoder can determine, based on the inter-layer reference picture flag, whether the entry in the reference picture list structure associated with the current picture is an ILRP entry. For example, the reference picture list structure has multiple entries for multiple reference pictures. Such entries include the entry associated with the current picture. The entries indicate the reference picture. For example, the reference picture list structure may be represented as ref_pic_list_struct( listIdx, rplsIdx ), where listIdx identifies the reference picture list, rplsIdx identifies the entry in the reference picture list, and ref_pic_list_struct is a syntax structure that returns the entries based on listIdx and rplsIdx. Furthermore, the inter-layer reference picture flag indicates whether the entry associated with the current picture is an ILRP entry. For example, the inter-layer reference picture flag may be represented as inter_layer_ref_pic_flag[ listIdx ][ rplsIdx ][ i ]. Specifically, when the i-th entry in ref_pic_list_struct( listIdx, rplsIdx ) is an ILRP entry, inter_layer_ref_pic_flag[ listIdx ][ rplsIdx ][ i ] may be set to equal to 1. Furthermore, when the i-th entry in ref_pic_list_struct( listIdx, rplsIdx ) is not an ILRP entry, inter_layer_ref_pic_flag[ listIdx ][ rplsIdx ][ i ] may be set to equal to 0. For example, ref_pic_list_struct( listIdx, rplsIdx ) and inter_layer_ref_pic_flag[ listIdx ][ rplsIdx ][ i ] may be encoded in the bitstream within the SPS.In another example, ref_pic_list_struct( listIdx, rplsIdx ) and inter_layer_ref_pic_flag[ listIdx ][ rplsIdx ][ i ] may be encoded in the bitstream within a header associated with the current picture, such as the slice header and / or picture header.

[0180] In step 1205, the decoder may determine the layer of the interlayer reference picture based on the ILRP layer indicator when the entry is an ILRP entry. For example, the ILRP layer indicator may indicate one or more layers for each entry in the reference picture list structure associated with the interlayer reference picture, as indicated by the interlayer reference picture flag. For example, the interlayer reference picture may be contained within the same AU as the current picture. Therefore, the interlayer reference picture may contain the same POC as the current picture. Furthermore, the interlayer reference picture may be located in a different layer than the current picture. For example, the interlayer reference picture may be associated with a lower layer than the current picture. Therefore, the interlayer reference picture may be associated with a lower layer ID than the current picture.

[0181] In step 1207, when the entry is an ILRP entry, the decoder can decode the current picture according to the inter-layer prediction based on the inter-layer reference picture indicated by the entry in the reference picture list structure, at the level indicated by the ILRP layer indicator.

[0182] In step 1209, the decoder can decode the current picture according to an intra-layer prediction based on the intra-layer reference picture indicated by the entry in the reference picture list structure, when the entry is not an ILRP entry. An intra-layer reference picture is simply referred to as a reference picture in a single-layer context. Furthermore, the intra-layer prediction may include an intra-prediction and / or a single-layer inter-prediction, depending on the context. When a reference picture is adopted, the intra-layer prediction indicates a single-layer inter-prediction.

[0183] In step 1211, the decoder transfers the decoded / reconstructed current picture for display as part of the decoded video sequence.

[0184] Figure 13 is a schematic diagram of an exemplary system 1300 for coding a video sequence of images in a bitstream such as bitstream 900 when employing interlayer prediction. System 1300 may be implemented by an encoder and decoder, such as a codec system 200, an encoder 300, a decoder 400, and / or a video coding device 1000. Furthermore, system 1300 may be employed when implementing methods 100, 1100, and / or 1200 for decoding pictures according to unidirectional interpretation 500, bidirectional interpretation 600, and / or layer-based prediction 700 by employing an RPL structure 800.

[0185] System 1300 includes a video encoder 1302. The video encoder 1302 includes an encoding module 1301 for encoding the current picture into a bitstream, the current picture being encoded according to an inter-layer prediction based on an inter-layer reference picture. The encoding module 1301 further encodes a reference picture list structure into the bitstream, the reference picture list structure having multiple entries for multiple reference pictures, including an entry related to the current picture, and indicating an inter-layer reference picture. The encoding module 1301 further encodes an inter-layer reference picture flag into the bitstream, the inter-layer reference picture flag indicating that the entry related to the current picture is an ILRP entry. The video encoder 1302 further includes a storage module 1303 for storing the bitstream for communication toward the decoder. The video encoder 1302 further includes a transmission module 1305 for transmitting the bitstream toward the video decoder 1310. The video encoder 1302 may be further configured to perform any of the steps of method 1100.

[0186] System 1300 also includes a video decoder 1310. The video decoder 1310 includes a receive module 1311 for receiving a bitstream having a current picture, a reference picture list structure, and an inter-layer reference picture flag. The video decoder 1310 further includes a determination module 1313 for determining, based on the inter-layer reference picture flag, whether an entry in the reference picture list structure related to the current picture is an ILRP entry. When the entry is an ILRP entry, the video decoder 1310 further includes a decode module 1315 for decoding the current picture according to an inter-layer prediction based on the inter-layer reference picture indicated by the entry in the reference picture list structure. The video decoder 1310 further includes a transfer module 1317 for transferring the current picture for display as part of a decoded video sequence. The video decoder 1310 may be further configured to perform any of the steps of method 1200.

[0187] When there are no intervening elements between the first and second elements, except for lines, traces, or other media, the first element is directly joined to the second element. When there are intervening elements other than lines, traces, or other media between the first and second elements, the first element is indirectly joined to the second element. The term "joined" and its variations include both direct and indirect joining. The use of the term "about" means a range including ±10% of the following number unless otherwise specified.

[0188] It should be understood that the steps of the exemplary methods described herein do not necessarily have to be performed in the order described, and the order of the steps in such methods should be understood as merely illustrative. Similarly, additional steps may be included in such methods, and some steps may be omitted or combined in a manner consistent with the various embodiments of this disclosure.

[0189] While several embodiments are provided in this disclosure, it should be understood that the systems and methods disclosed may be embodied in many other specific forms without departing from the spirit or scope of this disclosure. These examples are to be considered illustrative rather than restrictive, and their intent is not limited to the details given herein. For example, various elements or components may be combined or integrated in another system, or some features may be omitted or not implemented at all.

[0190] In addition, techniques, systems, subsystems, and methods described and illustrated individually or separately in various embodiments may be combined with or integrated with other systems, components, techniques, or methods without departing from the scope of this disclosure. Other examples of modifications, substitutions, and alterations that are evident to those skilled in the art may be made without departing from the spirit and scope of what is disclosed herein. [Explanation of symbols]

[0191] 200 codec systems 201 segmented video signal 211 General-purpose coder control components 213 Transformation Scaling and Quantization Components 215 Estimated elements within a picture 217 Predictive elements within a picture 219 Motion compensation components 221 Motion Estimation Components 223 Decoded Picture Buffer Components 225 In-loop filter components 227 Filter Control Analysis Components 229 Scaling and Inverse Transformation Components 231 Header Formatting and Context-Adaptive Binary Arithmetic Coding Components 300 video encoders 301 segmented video signal 313 Transformation and Quantization Components 317 Predictive elements within a picture 321 Motion compensation components 323 Decoded Picture Buffer Components 325 In-loop filter components 329 Inverse Transform and Quantization Components 331 Entropy Coding Components 400 video decoders 417 Predictive elements within a picture 421 Motion compensation components 423 Decoded Picture Buffer Components 425 In-loop filter components 429 Inverse Transform and Quantization Components 433 Entropy Decoding Components 500 Unidirectional Interpretation 510 Current Picture 511 Currently blocked 513 Movement trajectory 530 Reference Picture 531 Reference Block 533 Temporal distance 535 Motion vector 600 Bidirectional Interpretation 610 Current Picture 611 Currently blocked 613 Movement trajectory 620 Preceding reference picture 621 Preceding reference block 623 Preceding temporal distance 625 Preceding motion vector 630 Subsequent reference picture 631 Subsequent reference block 633 Subsequent temporal distance 635 Subsequent motion vector 700-layer based prediction 711-718 Pictures 721 Inter-layer prediction 723 Inter forecast 731 Layer N 732 Layer N+1 800 Reference Picture List Structure (RPL Structure) 811 RPL0 812 RPL1 815 Reference Picture List Structure Entry 821 listIdx 825 rplsIdx 833 ILRP flag 835 ILRP Layer Indicator 900 bitstream 910 Sequence Parameter Set (SPS) 911 Picture Parameter Set (PPS) 915 Slice Header 920 image data 921 Access Unit 923 Pictures 925 slices 931 Reference Picture List Structure 933 ILRP flag 935 ILRP Layer Indicator 1000 video coding devices 1010 Transceiver Unit (Tx / Rx) 1014 Coding Module 1020 Downstream Port 1030 processor 1032 memory 1050 Upstream Port 1060 Input and / or Output (I / O) Devices 1300 System 1301 Encoding Module 1302 Video Encoder 1303 Memory Module 1305 Transmitter Module 1310 Video Decoder 1311 Receiver Module 1313 Decision Module 1315 Decryption Module 1317 Transfer Module

Claims

1. A method implemented within the decoder, The step of receiving a bitstream comprising encoded data of a picture and an SPS having a sequence parameter set (SPS) flag, wherein the SPS flag equals 1, indicating that an interlayer reference picture (ILRP) may be used for interpretation of one or more coded pictures in a coded video sequence (CVS), When the SPS flag is equal to 1, the bitstream further comprises an interlayer reference picture flag, wherein the interlayer reference picture flag equal to 1 specifies that the i-th entry in the reference picture list structure is an ILRP entry, and the interlayer reference picture flag equal to 0 specifies that the i-th entry in the reference picture list structure is not an ILRP entry, and When the interlayer reference picture flag specifies that the i-th entry in the reference picture list structure is an ILRP entry, the steps include: decoding the current picture based on the interlayer reference picture indicated by the i-th entry in the reference picture list structure; A method for providing this.

2. The method according to claim 1, wherein the reference picture list structure comprises an ILRP layer indicator, and the method further comprises the step of determining the layer of the interlayer reference picture based on the ILRP layer indicator.

3. The method according to claim 1 or 2, wherein the reference picture list structure is denoted as ref_pic_list_struct( listIdx, rplsIdx ), where listIdx identifies the reference picture list, rplsIdx identifies an entry in the reference picture list, and ref_pic_list_struct is the syntax structure.

4. When the inter-layer reference picture flag is shown as inter_layer_ref_pic_flag[ listIdx ][ rplsIdx ][ i ], and the i-th entry in the ref_pic_list_struct( listIdx, rplsIdx ) is the ILRP entry, then the inter_layer_ref_pic_flag[ listIdx ][ rplsIdx ] The method according to claim 3, wherein inter_layer_ref_pic_flag[listIdx][rplsIdx][i] is equal to 0 when inter_layer_ref_pic_flag[listIdx][rplsIdx][i] is equal to 1 and the entry i in ref_pic_list_struct(listIdx, rplsIdx) is not the ILRP entry.

5. The method according to any one of claims 1 to 4, further comprising the step of decoding the current picture according to an in-layer prediction based on an in-layer reference picture indicated by the entry in the reference picture list structure when the entry is not the ILRP entry.

6. The method according to claim 4, wherein the inter_layer_ref_pic_flag[ listIdx ][ rplsIdx ][ i ] is included in the ref_pic_list_struct( listIdx, rplsIdx ) and the ref_pic_list_struct( listIdx, rplsIdx) is included in the SPS.

7. The method according to any one of claims 1 to 6, wherein the SPS flag being equal to 0 specifies that ILRP is not used for interpretation of any coded picture in the CVS.

8. A method implemented within an encoder, A step of encoding a current picture into a bitstream, wherein the current picture is encoded according to an inter-layer prediction based on an inter-layer reference picture. A step of encoding a sequence parameter set (SPS) into the bitstream, wherein the SPS comprises an SPS flag, and the SPS flag being equal to 1 specifies that an inter-layer reference picture (ILRP) may be used for interpretation of one or more coded pictures in a coded video sequence (CVS). When the SPS flag is equal to 1, the step of encoding an interlayer reference picture flag in the bitstream, wherein the interlayer reference picture flag equal to 1 specifies that the i-th entry in the reference picture list structure is an ILRP entry, and the interlayer reference picture flag equal to 0 specifies that the i-th entry in the reference picture list structure is not an ILRP entry. A method for providing this.

9. The method according to claim 8, further comprising the step of encoding an ILRP layer indicator in the bitstream, wherein the ILRP layer indicator indicates a layer of the interlayer reference picture.

10. The method according to claim 8 or 9, wherein the reference picture list structure is denoted as ref_pic_list_struct( listIdx, rplsIdx ), where listIdx identifies the reference picture list, rplsIdx identifies an entry in the reference picture list, and ref_pic_list_struct is a syntax structure.

11. When the inter-layer reference picture flag is shown as inter_layer_ref_pic_flag[ listIdx ][ rplsIdx ][ i ], and the i-th entry in the ref_pic_list_struct( listIdx, rplsIdx ) is the ILRP entry, then the inter_layer_ref_pic_flag[ listIdx ][ rplsIdx ] The method according to claim 10, wherein inter_layer_ref_pic_flag[listIdx][rplsIdx][i] is equal to 0 when inter_layer_ref_pic_flag[listIdx][rplsIdx][i] is equal to 1 and the entry i in ref_pic_list_struct(listIdx, rplsIdx) is not the ILRP entry.

12. The method according to claim 11, wherein the inter_layer_ref_pic_flag[ listIdx ][ rplsIdx ][ i ] is encoded within the ref_pic_list_struct( listIdx, rplsIdx ).

13. The method according to claim 10, wherein the ref_pic_list_struct(listIdx, rplsIdx) is encoded in the SPS of the bitstream.

14. The method according to claim 10, wherein the ref_pic_list_struct(listIdx, rplsIdx) is encoded in the header associated with the current picture.

15. The method according to any one of claims 8 to 14, wherein the SPS flag being equal to 0 specifies that ILRP is not used for interpretation of any coded picture in the CVS.

16. A decoder comprising a processing circuit configuration for performing the method according to any one of claims 1 to 7.

17. An encoder comprising a processing circuit configuration for performing the method described in any one of claims 8 to 15.

18. A computer program comprising program code for performing the method described in any one of claims 1 to 7 or any one of claims 8 to 15 when executed on a computer or processor.

19. A non-temporary computer-readable medium carrying program code that, when executed by a computer device, causes the computer device to execute the method according to any one of claims 1 to 7 or any one of claims 8 to 15.

20. It is a decoder, One or more processors, The decoder comprises a non-temporary computer-readable storage medium coupled to the processor and storing a program for execution by the processor, wherein the decoder is configured to perform the method according to any one of claims 1 to 7 when the program is executed by the processor. decoder.

21. It is an encoder, One or more processors, The encoder comprises a non-temporary computer-readable storage medium coupled to the processor and storing a program for execution by the processor, wherein the encoder is configured to perform the method according to any one of claims 8 to 15 when the program is executed by the processor. Encoder.

22. A video coding device, The system comprises a processor, a receiver coupled to the processor, a memory coupled to the processor, and a transmitter coupled to the processor, wherein the processor, the receiver, the memory, and the transmitter are configured to perform the method according to any one of claims 1 to 14. Video coding device.

23. A receiving means for receiving a bitstream comprising currently encoded picture data and an SPS having a sequence parameter set (SPS) flag, wherein the SPS flag equals 1, indicating that an interlayer reference picture (ILRP) may be used for interpretation of one or more coded pictures in a coded video sequence (CVS), When the SPS flag is equal to 1, the bitstream further comprises an interlayer reference picture flag, where the interlayer reference picture flag equal to 1 specifies that the i-th entry in the reference picture list structure is an ILRP entry, and the interlayer reference picture flag equal to 0 specifies that the i-th entry in the reference picture list structure is not an ILRP entry, and the receiving means When the interlayer reference picture flag specifies that the i entry in the reference picture list structure is an ILRP entry, a decoding means for decoding the current picture based on the interlayer reference picture indicated by the i entry in the reference picture list structure and A decoder equipped with a decoder.

24. The current picture is encoded into a bitstream, wherein the current picture is encoded according to inter-layer predictions based on inter-layer reference pictures. Encoding a sequence parameter set (SPS) into the bitstream, wherein the SPS comprises an SPS flag, and the SPS flag being equal to 1 indicates that an inter-layer reference picture (ILRP) may be used for interpretation of one or more coded pictures in a coded video sequence (CVS). When the SPS flag is equal to 1, the interlayer reference picture flag is encoded in the bitstream such that an interlayer reference picture flag equal to 1 indicates that the i-th entry in the reference picture list structure is an ILRP entry, and an interlayer reference picture flag equal to 0 indicates that the i-th entry in the reference picture list structure is not an ILRP entry. Encoding means for performing An encoder equipped with the following features.

25. A device for storing a bitstream, comprising at least one storage device and at least one receiver, The at least one receiver is configured to receive one or more bitstreams, The at least one storage device is configured to store the one or more bitstreams, The bitstream currently comprises encoded data of a picture and an SPS having a Sequence Parameter Set (SPS) flag, wherein the SPS flag equal to 1 indicates that an Interlayer Reference Picture (ILRP) may be used for interpretation of one or more coded pictures in a coded video sequence (CVS). When the SPS flag is equal to 1, the bitstream further comprises an interlayer reference picture flag, where the interlayer reference picture flag equal to 1 specifies that the i-th entry in the reference picture list structure is an ILRP entry, and the interlayer reference picture flag equal to 0 specifies that the i-th entry in the reference picture list structure is not an ILRP entry. device.

26. A method for storing a bitstream, The steps include receiving one or more bitstreams through at least one receiver, The step of storing the bitstream in one or more storage devices, wherein the bitstream comprises encoded data of the current picture and an SPS having a sequence parameter set (SPS) flag, wherein the SPS flag equal to 1 indicates that the interlayer reference picture (ILRP) may be used for interpretation of one or more coded pictures in the coded video sequence (CVS). When the SPS flag is equal to 1, the bitstream further comprises an interlayer reference picture flag, where the interlayer reference picture flag equal to 1 specifies that the i-th entry in the reference picture list structure is an ILRP entry, and the interlayer reference picture flag equal to 0 specifies that the i-th entry in the reference picture list structure is not an ILRP entry. method.

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