Encoder, decoder and corresponding method

Abstract

To provide a method of decoding a coded video bitstream.SOLUTION: A method includes: a step of obtaining, from a coded video bitstream, a first syntax element specifying whether a first layer uses inter-layer prediction; a step of obtaining one or more second syntax elements associated with one or more second layers; and a step of performing inter-layer prediction on a picture of the first layer by using the picture of the second layer associated with the second syntax element as a reference picture.SELECTED DRAWING: Figure 1A

Description

[Technical Field]

[0001] FIELD Embodiments of the present disclosure relate generally to the field of image processing, and more particularly to inter-layer prediction. CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to U.S. Provisional Application No. 62 / 912,046, filed October 7, 2019, the subject matter of which is incorporated herein by reference in its entirety. [Background technology]

[0002] Video coding (video encoding and decoding) is used in a wide range of digital video applications, such as broadcast digital TV, video transmission over the Internet and mobile networks, real-time conversation applications such as video chat, video conferencing, DVD and Blu-ray discs, video content collection and editing systems, and camcorders in security applications.

[0003] The amount of video data required to render a relatively short video is substantial, which can result in difficulties when the data is streamed or otherwise communicated over communication networks with limited bandwidth capacity. Therefore, video data is typically compressed before being communicated over modern telecommunications networks. If the video is stored on a storage device, the size of the video can also be an issue because memory resources can be limited. Video compression devices often use software and / or hardware at the source to code the video data before transmission or storage, thereby reducing the amount of data required to represent a digital video image. The compressed data is then received at the destination by a video decompressor, which decodes the video data. With limited network resources and ever-increasing demands for higher video quality, improved compression and decompression techniques that improve compression ratios with little sacrifice in image quality are desirable. Summary of the Invention

[0004] Embodiments of the present application provide apparatuses and methods for encoding and decoding according to the independent claims.

[0005] These and other objects are achieved by the subject matter of the independent claims. Further embodiments are evident from the dependent claims, the description and the drawings.

[0006] Particular embodiments are outlined in the accompanying independent claims, while other embodiments are outlined in the dependent claims.

[0007] According to a first aspect, the present invention relates to a method for decoding a coded video bitstream, the method being performed by a decoding device. The method includes the steps of: obtaining, from the coded video bitstream, a first syntax element specifying whether a first layer uses inter-layer prediction; obtaining, from the coded video bitstream, one or more second syntax elements associated with one or more second layers, each second syntax element specifying whether the second layer is a direct reference layer for the first layer, wherein at least one second syntax element of the one or more second syntax elements has a value specifying that the second layer is a direct reference layer for the first layer if a value of the first syntax element specifies that the first layer is allowed to use inter-layer prediction; and performing inter-layer prediction on a picture of the first layer by using a picture of the second layer associated with the at least one second syntax element as a reference picture.

[0008] Alternatively, the first syntax element specifies whether one or more second syntax elements associated with one or more second layers are present in the coded video bitstream. Further, a first syntax element equal to 1 specifies that one or more second syntax elements associated with one or more second layers are not present in the coded video bitstream, or a first syntax element equal to 0 specifies that one or more second syntax elements associated with one or more second layers are present in the coded video bitstream. Here, a layer comprises a sequence of coded pictures with the same layer index. Here, the layer index of one or more second layers is smaller than the layer index of the first layer. Here, second layers associated with different second syntax elements are accompanied by different layer indices. Here, the one or more second syntax elements have a one-to-one correspondence with the one or more second layers. Here, a bitstream is a sequence of bits that forms one or more coded video sequences (CVS). Here, a coded video sequence (CVS) is a sequence of AUs. Here, a coded layer video sequence (CLVS) is a sequence of PUs with the same value of nuh_layer_id. Here, an access unit (AU) is a collection of PUs that contain coded pictures that belong to different layers and are associated with the same time for output from the DPB. Here, a picture unit (PU) is a collection of NAL units that are related to each other according to a specified classification rule, are consecutive in decoding order, and contain exactly one coded picture. Here, the inter-layer reference picture (ILRP) is a picture in the same AU as the current picture, and its nuh_layer_id is smaller than that of the current picture. Here, an SPS is a syntax structure containing syntax elements that apply to zero or more entire CLVSs. Here, if Layer A uses Layer B as a reference layer, Layer B is a direct reference layer of Layer A. If Layer A uses Layer B as a reference layer and Layer B uses Layer C as a reference layer, but Layer A does not use Layer C as a reference layer, Layer C is not a direct reference layer of Layer A.

[0009] In a possible implementation of a method according to such a first aspect, wherein the first syntax element equal to 1 specifies that the first layer does not use inter-layer prediction, or wherein the first syntax element equal to 0 specifies that the first layer is allowed to use inter-layer prediction.

[0010] In any preceding implementation of the first aspect or a possible implementation of a method according to such first aspect, wherein the second syntax element equal to 0 specifies that the second layer associated with the second syntax element is not a direct reference layer of the first layer, or the second syntax element equal to 1 specifies that the second layer associated with the second syntax element is a direct reference layer of the first layer.

[0011] In any preceding implementation of the first aspect or a possible implementation of a method according to such a first aspect, wherein the step of obtaining one or more second syntax elements is performed if a value of the first syntax element specifies that the first layer is allowed to use inter-layer prediction.

[0012] In any preceding implementation of the first aspect or a possible implementation of a method according to such a first aspect, wherein the method further includes, when a value of the first syntax element specifies that the first layer does not use inter-layer prediction, performing prediction on a picture of the first layer without using a picture of the layer associated with the at least one second syntax element as a reference picture.

[0013] According to a second aspect, the present invention provides a method for encoding a coded video bitstream, the method being performed by an encoder, comprising: determining whether at least one second layer is a direct reference layer of a first layer; and encoding into the coded video bitstream a syntax element specifying whether the first layer uses inter-layer prediction, wherein if none of the at least one second layer is a direct reference layer of the first layer, a value of the syntax element specifies that the first layer does not use inter-layer prediction.

[0014] The step of determining whether at least one second layer is a direct reference layer of the first layer includes the steps of: determining that the second layer is a direct reference layer of the first layer based on determining that a first rate-distortion cost is less than or equal to a second rate-distortion cost; and determining that the second layer is not a direct reference layer of the first layer based on determining that the first rate-distortion cost is greater than or equal to a second rate-distortion cost, where the first rate-distortion cost is a cost of using the second layer as a direct reference layer of the first layer, and the second rate-distortion cost is a cost of not using the second layer as a direct reference layer of the first layer.

[0015] In a possible implementation of the method according to this second aspect, the value of the syntax element specifies that the first layer is allowed to use inter-layer prediction if the at least one second layer is a direct reference layer of the first layer.

[0016] According to a third aspect, the present invention relates to an apparatus for decoding a coded video bitstream. The apparatus includes an acquisition unit and a prediction unit. The acquisition unit is configured to acquire, from the coded video bitstream, a first syntax element specifying whether a first layer uses inter-layer prediction. The acquisition unit is further configured to acquire one or more second syntax elements associated with one or more second layers, each second syntax element specifying whether the second layer is a direct reference layer of the first layer. If the value of the first syntax element specifies that the first layer is allowed to use inter-layer prediction, at least one second syntax element of the one or more second syntax elements has a value specifying that the second layer is a direct reference layer of the first layer. The prediction unit is configured to perform inter-layer prediction on a picture of the first layer by using a picture of the second layer associated with the at least one second syntax element as a reference picture.

[0017] In a possible implementation of a method according to such a third aspect, wherein the first syntax element equal to 1 specifies that the first layer does not use inter-layer prediction, or wherein the first syntax element equal to 0 specifies that the first layer is allowed to use inter-layer prediction.

[0018] In any preceding implementation of the third aspect or a possible implementation of a method according to such third aspect, wherein the second syntax element equal to 0 specifies that the second layer associated with the second syntax element is not a direct reference layer of the first layer, or the second syntax element equal to 1 specifies that the second layer associated with the second syntax element is a direct reference layer of the first layer.

[0019] In any preceding implementation of the third aspect or a possible implementation of a method according to such a third aspect, wherein a prediction unit configured to acquire one or more second syntax elements is executed if a value of the first syntax element specifies that the first layer is allowed to use inter-layer prediction.

[0020] According to a fourth aspect, the present invention relates to an apparatus for encoding a coded video bitstream. The apparatus includes a determining unit and an encoding unit. The determining unit is configured to determine whether at least one second layer is a direct reference layer of the first layer. The encoding unit is configured to encode a syntax element into the coded video bitstream, where the syntax element specifies whether the first layer uses inter-layer prediction. Wherein, if any of the at least one second layer is not a direct reference layer of the first layer, a value of the syntax element specifies that the first layer does not use inter-layer prediction.

[0021] In a possible implementation form of the method according to such a fourth aspect, where if at least one second layer is a direct reference layer of a first layer, the value of the syntax element specifies that the first layer is allowed to use inter-layer prediction.

[0022] The method of the first aspect of the invention can be implemented by the apparatus of the third aspect of the invention. Further features and implementations of the method according to the third aspect of the invention correspond to the features and implementations of the apparatus according to the first aspect of the invention.

[0023] The method of the second aspect of the invention can be implemented by the apparatus of the fourth aspect of the invention. Further features and implementations of the method according to the fourth aspect of the invention correspond to the features and implementations of the apparatus according to the second aspect of the invention.

[0024] The method according to the second aspect may be extended to an implementation form corresponding to an implementation form of the first device according to the first aspect, and therefore the implementation form of the method includes the features of the corresponding implementation form of the first device.

[0025] The advantages of the method according to the second aspect are the same as the advantages of the corresponding implementation of the first device according to the first aspect.

[0026] According to a fifth aspect, the present invention relates to an apparatus for decoding a video stream, comprising a processor and a memory, the memory storing instructions for causing the processor to carry out the method according to the first aspect.

[0027] According to a sixth aspect, the present invention relates to an apparatus for encoding a video stream, comprising a processor and a memory, the memory storing instructions for causing the processor to carry out the method according to the second aspect.

[0028] According to a seventh aspect, there is proposed a computer-readable storage medium having stored thereon instructions configured, when executed, to cause one or more processors to encode video data, the instructions causing the one or more processors to perform a method according to the first or second aspect or any possible implementation of the first or second aspect.

[0029] According to an eighth aspect, the present invention relates to a computer program comprising a program code for carrying out, when the computer program is run on a computer, the method according to the first or second aspect or any possible embodiment of the first or second aspect.

[0030] According to a ninth aspect, the present invention relates to a non-transitory storage medium containing a coded bitstream to be decoded by an apparatus, the bitstream being generated by dividing a frame of a video or image signal into blocks and including a plurality of syntax elements, the plurality of syntax elements including a first syntax element specifying whether a first layer uses inter-layer prediction and one or more second syntax elements associated with one or more second layers, each second syntax element specifying whether the second layer is a direct reference layer of the first layer, and at least one second syntax element of the one or more second syntax elements having a value specifying that the second layer is a direct reference layer of the first layer if the value of the first syntax element specifies that the first layer is allowed to use inter-layer prediction.

[0031] The details of one or more embodiments are set forth in the accompanying drawings and the description below. Other features, objects, and advantages will be apparent from the description, drawings, and claims.

[0032] Furthermore, the following embodiments are provided:

[0033] In one embodiment, a method for decoding a coded video bitstream is provided, the method including: Parsing a first syntax element specifying whether a layer with index i uses inter-layer prediction, where i is an integer and is greater than 0. If a first condition is satisfied, parsing a second syntax element specifying whether a layer with index j is a direct reference layer of a layer with index i, where the first condition includes the first syntax element specifying that the layer with index i can use inter-layer prediction, j is equal to i-1, and any one of the layers with an index less than j is not a direct reference layer of the layer with index i. Predicting a picture of a layer having index i based on a value of a second syntax element.

[0034] In one embodiment, if the first syntax element specifies that the layer with index i may use inter-layer prediction, then the sum of vps_direct_direct_direct_dinercy_flag[i][k] is greater than 0, where k is every integer in the range from 0 to i-1, where vps_direct_direct_direct_depency_flag equal to 1 specifies that the layer with index k is a direct reference layer of the layer with index I, and vps_direct_direct_direct_depency_flag equal to 0 specifies that the layer with index k is not a direct reference layer of the layer with index i.

[0035] In one embodiment, if the first syntax element specifies that a layer with index i may use inter-layer prediction, at least one value of vps_direct_direct_direct_dinercy_flag[i][k] is equal to 1, where k is an integer and is in the range of 0 to i-1, where vps_direct_direct_direct_depency_flag equal to 1 specifies that the layer with index k is a direct reference layer of the layer with index I, and vps_direct_direct_direct_depency_flag equal to 0 specifies that the layer with index k is not a direct reference layer of the layer with index i.

[0036] In one embodiment, the pictures of the layer with index i include the pictures in or associated with the layer with index i.

[0037] In one embodiment, a method for decoding a coded video bitstream is provided, the method including: Parsing a first syntax element specifying whether a layer with index i uses inter-layer prediction, where i is an integer and is greater than 0. If a condition is met, a step of predicting a picture of a layer having index i using an image of the layer having index j as a direct reference layer of the layer having index i, where j is an integer and j is equal to i-1, and where this condition includes a syntax element specifying that the layer having index i may use inter-layer prediction.

[0038] In one embodiment, the pictures of the layer with index i include the pictures in or associated with the layer with index i.

[0039] In one embodiment, a method for decoding a coded video bitstream is provided, the method including: Parsing a syntax element specifying whether at least one long-term reference picture (LTRP) is used for inter-prediction of coded pictures in a coded video sequence (CVS), where each picture of the at least one LTRP is marked as "used for long-term reference" but is not an inter-layer reference picture (ILRP). Predicting one or more coded pictures in the CVS based on the values ​​of the syntax elements.

[0040] In one embodiment, a method for decoding a coded video bitstream is provided, the method including: determining whether conditions are met, where all conditions include the layer index of the current layer being greater than a preset value; If the condition is met, parsing a first syntax element specifying whether at least one inter-layer reference picture (ILRP) is used for inter-prediction of any coded picture in the coded video sequence (CVS). Predicting one or more coded pictures in the CVS based on the value of the first syntax element.

[0041] In one embodiment, the preset value is zero.

[0042] In one embodiment, the condition further includes that a second syntax element (eg, sps_video_parameter_set_id) is greater than zero.

[0043] In one embodiment, a method for decoding a coded video bitstream is provided, the method including: A step of determining whether conditions are met, where all conditions include that the layer index of the current layer is greater than a preset value and the current entry in the reference picture list structure is an ILRP entry. If the condition is met, parsing a syntax element specifying an index into the list of direct dependent layers of the current layer. Predicting one or more coded pictures in the CVS based on the reference picture list structure of the current entry, where the current ILRP is obtained using an index into the list of direct dependent layers.

[0044] In one embodiment, the preset value is one.

[0045] In one embodiment, an encoder (20) is provided, comprising processing circuitry for carrying out the method of any one of claims 1 to 12.

[0046] In one embodiment, a decoder (30) is provided, comprising processing circuitry for performing the method of any one of claims 1 to 12.

[0047] In one embodiment there is provided a computer program product comprising program code for performing a method according to any one of the preceding claims when the program code is run on a computer or processor.

[0048] In one embodiment, a decoder is provided, comprising: one or more processors; and 10. A non-transitory computer readable storage medium coupled to the processor and having programming stored thereon for execution by the processor, the programming, when executed by the processor, configuring the decoder to perform the method of any one of the preceding claims.

[0049] In one embodiment, an encoder is provided, comprising: one or more processors; and 10. A non-transitory computer readable storage medium coupled to the processor and having programming stored thereon for execution by the processor, the programming, when executed by the processor, configuring the encoder to perform the method of any one of the preceding claims.

[0050] In one embodiment, there is provided a non-transitory computer readable medium carrying program code which, when executed by a computing device, causes the computing device to perform a method according to any one of the preceding claims. [Brief explanation of the drawings]

[0051] In the following embodiments of the present invention, the invention will be described in more detail with reference to the accompanying figures and drawings. [Figure 1A] FIG. 1A is a block diagram illustrating an example of a video coding system configured to implement embodiments of the present invention. [Figure 1B] FIG. 1B is a block diagram illustrating another example of a video coding system configured to implement embodiments of the present invention. [Figure 2] FIG. 2 is a block diagram illustrating an example of a video encoder configured to implement embodiments of the present invention. [Figure 3]FIG. 3 is a block diagram illustrating one exemplary architecture of a video decoder configured to implement embodiments of the present invention. [Figure 4] FIG. 4 is a block diagram showing an example of an encoding device or a decoding device. [Figure 5] FIG. 5 is a block diagram showing another example of an encoding device or a decoding device. [Figure 6] FIG. 6 is a block diagram illustrating scalable coding with two layers. [Figure 7] FIG. 7 is a block diagram showing an exemplary configuration of a content supply system 3100 for implementing a content distribution service. [Figure 8] FIG. 8 is a block diagram showing the configuration of an example of a terminal device. [Figure 9] FIG. 9 shows a flow chart of a decoding method according to one embodiment. [Figure 10] FIG. 10 shows a flow chart of an encoding method according to one embodiment. [Figure 11] FIG. 11 is a schematic diagram of an encoder according to one embodiment. [Figure 12] FIG. 12 is a schematic diagram of a decoder according to one embodiment.

[0052] Identical reference signs below refer to identical or at least functionally equivalent features unless expressly specified otherwise. DETAILED DESCRIPTION OF THE INVENTION

[0053] In the following description, reference is made to the accompanying drawings. The drawings form a part of this disclosure and show, by way of illustration, specific aspects of embodiments of the invention or in which embodiments of the invention may be used. It is understood that embodiments of the invention may be used in other ways and may include structural or logical variations not shown in the drawings. The following detailed description, therefore, is not to be taken in a limiting sense and the scope of the present invention is defined by the appended claims.

[0054] For example, disclosure related to a described method also applies to a corresponding apparatus or system configured to perform the method, and vice versa. For example, if one or more particular method steps are described, a corresponding device may include one or more units (e.g., functional units) to perform the described one or more method steps (e.g., one unit performing one or more steps, or multiple units performing each of multiple steps), even if such one or more units are not explicitly described or shown in the drawings. On the other hand, for example, if a particular apparatus is described based on one or more units, e.g., functional units, a corresponding method may include one step for performing the functionality of one or more units (e.g., one step for performing the functionality of one or more units, or multiple steps for performing one or more functionality of multiple units), even if such one or more units are not explicitly described or shown in the drawings. Furthermore, it is understood that the features of the various exemplary embodiments and / or aspects described herein may be combined with one another to obtain different results, unless otherwise noted.

[0055] Video coding typically refers to processing a series of images that form a video or a video sequence. Instead of the term "picture," the terms "frame" or "image" may be used synonymously in the field of video coding. Video coding (or, in general, coding) includes two parts: video coding and video decoding. Video coding is performed at the source side and typically involves processing the original video image to reduce the amount of data needed to represent the video image (for more efficient storage and / or transmission). Video decoding is performed at the destination side and typically involves the reverse processing compared to the encoder to reconstruct the video image. Embodiments that refer to "coding" of video images (or, in general, pictures) are understood to relate to "encoding" or "decoding" of the video image or respective video sequence. The combination of encoding and decoding is also referred to as CODEC (Coding and Decoding).

[0056] In the case of lossless video coding, the original video footage can be reconstructed, i.e., the reconstructed video footage has the same quality as the original video footage (assuming there is no transmission or other data loss during storage or transmission). In the case of lossy video coding, further compression is performed, for example by quantization, to reduce the amount of data representing the video footage, which cannot be fully reconstructed at a decoder, i.e., the quality of the reconstructed video footage is lower or worse than the quality of the original video footage.

[0057] Some video coding standards belong to the group of "lossy hybrid video codecs" (i.e., they combine spatial and temporal prediction in the sample domain with 2D transform coding to apply quantization in the transform domain). Each picture of a video sequence is typically divided into a set of non-overlapping blocks, and coding is typically performed at the block level. In other words, at an encoder, video is typically processed, i.e., encoded, at the block (video block) level, for example, by using spatial (intra-picture) prediction and / or temporal (inter-picture) prediction to generate a predictive block, subtracting the predictive block from a current block (the block currently being / to be processed) to obtain a residual block, transforming the residual block to reduce the amount of data to be transmitted, and quantizing the residual block in the transform domain. Meanwhile, at a decoder, the inverse process is applied to the encoded or compressed block compared to the encoder to reconstruct the current block for representation. Additionally, the encoder replicates the decoder processing loop so that both generate the same predictions (e.g., intra-prediction and inter-prediction) and / or reconstruct subsequent blocks for processing, i.e., coding.

[0058] In the following embodiment of a video coding system 10, a video encoder 20 and a video decoder 30 are described based on FIGS. 1 to 3. FIG.

[0059] 1A is a schematic block diagram illustrating an exemplary coding system 10, e.g., a video coding system 10 (or short coding system 10) that can utilize the techniques of the present application. A video encoder 20 (or short encoder 20) and a video decoder 30 (or short decoder 30) of video coding system 10 represent examples of devices that can be configured to perform techniques in accordance with various embodiments described in the present application.

[0060] As shown in FIG. 1A, coding system 10 includes a source device 12 configured to provide encoded video data 12, e.g., to a destination device 14 for decoding.

[0061] Source device 12 includes an encoder 20 and may additionally, i.e., optionally, include a picture source 16, a preprocessor (or preprocessing unit) 18, for example a video preprocessor 18, and a communication interface or unit 22.

[0062] Picture source 16 may include or be any type of video capture device, such as a camera for capturing real-world imagery, and / or any type of video generation device, such as a computer graphics processor for generating computer-animated imagery, or any type of other device for acquiring and / or providing real-world imagery, computer-generated imagery (e.g., screen content, virtual reality (VR) imagery), and / or any combination thereof (e.g., augmented reality (AR) imagery). Picture source may also be any type of memory or storage device that stores any of the above images.

[0063] In distinction to the pre-processor 18 and the processing performed by the pre-processing unit 18, the video or video data 17 is also referred to as raw video or raw video data 17.

[0064] The pre-processor 18 is configured to receive (raw) video data 17 and perform pre-processing on the video data 17 to obtain pre-processed video data 19 or pre-processed video data 19. The pre-processing performed by the pre-processor 18 may include, for example, cropping, color format conversion (e.g., from RGB to YCbCr), color correction, or noise removal. It may be understood that the pre-processing unit 18 may be an optional component.

[0065] Video encoder 20 is configured to receive preprocessed video data 19 and provide encoded video data 21 (described in further detail below, e.g., based on FIG. 2). Communication interface 22 of source device 12 may be configured to receive encoded video data 21 and transmit encoded video data 21 (or any further processed version thereof) via communication channel 13 to another device, such as destination device 14, or any other device, for storage or direct reconstruction.

[0066] Destination device 14 includes a decoder 30 (eg, a video decoder 30) and may additionally include a communications interface or unit 28, a post-processor 32 (or post-processing unit 32), and a display device 34.

[0067] The communications interface 28 of the destination device 14 is configured to receive the encoded video data 21 (or any further processed version thereof), for example directly from the source device 12 or from any other source, for example a storage device, for example an encoded video data storage device, and to provide the encoded video data 21 to the decoder 30.

[0068] The communication interface 22 and the communication interface 28 may be a direct communication link between the source device 12 and the destination device 14, such as a direct wired or wireless connection. or via any kind of network, e.g., a wired or wireless network, or any combination thereof, or any kind of private and public network, or any kind of combination thereof.

[0069] The communications interface 22 may be configured, for example, to package the encoded video data 21 into an appropriate format, e.g., packets, and / or process the encoded video data using any type of transmission encoding or processing for transmission over a communications link or network.

[0070] The communications interface 28, which forms the counterpart of the communications interface 22, can be configured, for example, to receive the transmitted data and process the transmitted data using any kind of corresponding transmission decoding or processing and / or de-packaging to obtain the encoded video data 21.

[0071] Both communication interface 22 and communication interface 28 may be configured as unidirectional communication interfaces, as indicated by the arrow of communication channel 13 in FIG. 1A pointing from source device 12 to destination device 14, and / or as bidirectional communication interfaces, and may be configured to, for example, send and receive messages, for example, to acknowledge and exchange messages related to the communication link and / or any other information related to the data transmission, e.g., the encoded video data transmission.

[0072] The decoder 30 is configured to receive the encoded video data 21 and provide decoded video data 31 or decoded pictures 31 (further details are described below, e.g., based on Figure 3 or Figure 5).

[0073] The post-processor 32 of the destination device 14 is configured to post-process the decoded video data 31 (also referred to as reconstructed video data), e.g., decoded pictures 31, to obtain post-processed video data 33, e.g., post-processed video 33. The post-processing performed by the post-processing unit 32 may include, e.g., color format conversion (e.g., YCbCr to RGB conversion), color correction, cropping, or resampling, or any other processing to prepare, e.g., the decoded video data 31 for display, e.g., by a display device 34.

[0074] The display device 34 of the destination device 14 is configured to receive the post-processed video data 33 for displaying the image, for example, to a user or viewer. The display device 34 may be or include any type of display for presenting the reconstructed image, for example, an integrated or external display or monitor. The display may include, for example, a liquid crystal display (LCD), an organic light emitting diode display (OLED), a plasma display, a projector, a micro LED display, a liquid crystal on silicon (LCoS), a digital light processor (DLP), or any other type of display.

[0075] 1A depicts source device 12 and destination device 14 as separate devices, an embodiment of the device may also include both or both functionality, source device 12 or corresponding functionality, and destination device 14 or corresponding functionality. In such an embodiment, source device 12 or corresponding functionality and destination device 14 or corresponding functionality may be implemented using the same hardware and / or software, or by separate hardware and / or software, or any combination thereof.

[0076] As will be apparent to those skilled in the art based on this description, the functionality or presence and (exact) division of functionality of different units within source device 12 and / or destination device 14 as shown in FIG. 1A may vary depending on the actual device and application.

[0077] Encoder 20 (e.g., video encoder 20), decoder 30 (e.g., video decoder 30), or both encoder 20 and decoder 30 may be implemented via processing circuitry such as that shown in FIG. 1B , such as one or more microprocessors, digital signal processors (DSPs), application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), discrete logic, hardware, dedicated video coding, or any combination thereof. Encoder 20 may be implemented via processing circuitry 46 to implement various modules as described with respect to encoder 20 of FIG. 2 and / or any other encoder system or subsystem described herein. Decoder 30 may be implemented via processing circuitry 46 to implement various modules as described with respect to decoder 30 of FIG. 3 and / or any other decoder system or subsystem described herein. The processing circuitry may be configured to perform various operations, as described below. 5, if the techniques are implemented partially in software, a device may store instructions for the software on a suitable non-transitory computer-readable storage medium and execute the instructions in hardware using one or more processors to perform the techniques of this disclosure. Either video encoder 20 and video decoder 30 may be integrated as part of a combined encoder / decoder (CODEC) in a single device, for example, as shown in FIG. 1B.

[0078] Source device 12 and destination device 14 can include any of a wide range of devices, including any type of handheld or fixed device, such as, for example, a notebook or laptop computer, a mobile phone, a smartphone, a tablet or tablet computer, a camera, a desktop computer, a set-top box, a television, a display device, a digital media player, a video game console, a video streaming device (such as a content service server or content distribution server), a broadcast receiver device, a broadcast transmitter device, etc., and can use no operating system or any type of operating system. In some cases, source device 12 and destination device 14 may be equipped for wireless communication. Thus, source device 12 and destination device 14 can be wireless communication devices.

[0079] 1A is merely an example, and the techniques of the present application may be applied to video coding settings (e.g., video encoding or video decoding) that do not necessarily involve data communication between an encoding device and a decoding device. In other examples, data may be retrieved from local memory, streamed over a network, etc. A video coding device may encode data and store it in memory, and / or a video decoding device may retrieve data from memory and decode it. In some examples, encoding and decoding are performed by devices that do not communicate with each other but simply encode data to memory and / or retrieve data from memory and decode it.

[0080] For ease of explanation, embodiments of the present invention are described herein with reference to, for example, High-Efficiency Video Coding (HEVC) or with reference to reference software for Versatile Video Coding (VVC), the next-generation video coding standard developed by the ITU-T Video Coding Experts Group (VCEG) Joint Collaboration on Video Coding (JCT-VC), and the ISO / IEC Motion Picture Experts Group (MPEG). One skilled in the art will appreciate that embodiments of the present invention are not limited to HEVC or VVC.

[0081] Encoders and Encoding Methods FIG. 2 shows a schematic block diagram of an exemplary video encoder 20 configured to implement the techniques of the present application. In the example of FIG. 2, the video encoder 20 includes an input 201 (or input interface 201), a residual calculation unit 204, a transform processing unit 206, a quantization unit 208, an inverse quantization unit 210, an inverse transform processing unit 212, a reconstruction unit 214, a loop filter unit 220, a decoded picture buffer 230, a mode selection unit 260, an entropy encoding unit 270, and an output unit 272 (or output interface 272). The mode selection unit 260 may include an inter prediction unit 244, an intra prediction unit 254, and a partitioning unit 262. The inter prediction unit 244 may include a motion estimation unit and a motion compensation unit (not shown). The video encoder 20 shown in FIG. 2 is also referred to as a hybrid video encoder or a video encoder according to a hybrid video codec.

[0082] The residual calculation unit 204, the transform processing unit 206, the quantization unit 208, and the mode selection unit 260 may be referred to as forming a forward signal path of the encoder 20, while the inverse quantization unit 210, the inverse transform processing unit 212, the reconstruction unit 214, the buffer 216, the loop filter 220, the decoded picture buffer (DPB) 230, the inter prediction unit 244, and the intra prediction unit 254 may be referred to as forming a backward signal path of the video encoder 20. Here, the backward signal path of the video encoder 20 corresponds to the signal path of a decoder (see video decoder 30 of FIG. 3). The inverse quantization unit 210, the inverse transform processing unit 212, the reconstruction unit 214, the loop filter 220, the decoded picture buffer (DPB) 230, the inter prediction unit 244, and the intra prediction unit 254 may also be referred to as forming a “built-in decoder” of the video encoder 20.

[0083] Pictures and picture divisions (pictures and blocks) Encoder 20 may be configured to receive, for example via input 201, picture 7 (or video data 17), e.g., video relating to a video or a series of pictures forming a video sequence. The received picture or video data may also be preprocessed picture 19 (or preprocessed video data 19). For simplicity, the following description refers to Figure 17. Picture 17 may also be referred to as the current picture or the picture to be coded (particularly in video coding, to distinguish the current picture from other pictures, e.g., previously encoded and / or decoded pictures, of the same video sequence, i.e., a video sequence that also includes the current picture).

[0084] A (digital) image is, or can be considered as, a two-dimensional array or matrix of samples with intensity values. The samples in the array can also be referred to as pixels (a short form of picture element) or pels. The number of samples in the horizontal and vertical directions (or axes) of the array or picture defines the size and / or resolution of the picture. For color representation, three color components are typically used; that is, a picture can represent or contain three sample arrays. In an RBG format or color space, a picture contains corresponding red, green, and blue sample arrays. However, in video coding, each pixel is typically represented in a luminance and chrominance format or color space, e.g., YCbCr, which includes a luminance component denoted Y (sometimes alternatively, L is also used) and two chrominance components denoted Cb and Cr. The luminance (or luma for short) component Y represents brightness or gray level intensity (e.g., in a grayscale image), while the two chrominance (or chroma for short) components Cb and Cr represent chromaticity or color information components. Thus, a picture in YCbCr format contains a luma sample array of luma sample values ​​(Y) and two chroma sample arrays of chrominance values ​​(Cb and Cr). A picture in RGB format can be converted or transformed to YCbC format, and vice versa. This method is also known as color conversion or translation. If the picture is monochrome, the picture may contain only a luma sample array. Thus, an image may contain, for example, an array of luma samples in monochrome format, or an array of luma samples and two corresponding arrays of chroma samples in 4:2:0, 4:2:2, and 4:4:4 color formats.

[0085] Embodiments of video encoder 20 may include a video partitioning unit (not shown in FIG. 2 ) configured to partition picture 17 into multiple (typically non-overlapping) picture blocks 203. These blocks may also be referred to as root blocks, macroblocks (H.264 / AVC), or coding tree blocks (CTBs) or coding tree units (CTUs) (H.265 / HEVC and VVC). The video partitioning unit may be configured to use the same block size for all pictures of a video sequence and a corresponding grid that defines the block size, or to vary the block size between pictures, subsets, or groups of pictures, and to partition each picture into corresponding blocks.

[0086] In further embodiments, the video encoder may be configured to directly receive blocks 203 of picture 17, such as one, several, or all of the blocks forming picture 17. Picture block 203 may also be referred to as the current picture block or the picture block to be coded.

[0087] Similar to picture 17, picture block 203 is, or may be considered to be, a two-dimensional array or matrix of samples with luminance values ​​(sample values), albeit with smaller dimensions than picture 17. In other words, block 203 may include, for example, one sample array (e.g., a luma array for monochrome video 17, or a luma or chroma array for color video), or three sample arrays (e.g., a luma and two chroma arrays for color video 17), or any other number and / or type of arrays depending on the applied color format. The number of samples in the horizontal and vertical directions (or axes) of block 203 defines the size of block 203. Thus, a block may be, for example, an M×N (M columns, N rows) array of samples or an M×N array of transform coefficients.

[0088] 2, an embodiment of video encoder 20 may be configured to encode blocks of picture 17 on a block-by-block basis. For example, encoding and prediction may be performed on each block 203.

[0089] 2, embodiments of video encoder 20 may be further configured to partition and / or encode pictures by using slices (also referred to as video slices), where a picture may be partitioned or encoded into one or more slices (typically non-overlapping), and each slice may include one or more blocks (e.g., CTUs) or groups of one or more blocks (e.g., tiles (H.265 / HEVC and VC) or bricks (VVC)).

[0090] As shown in FIG. 2, embodiments of video encoder 20 may be further configured to partition and / or encode a picture by using slices / tile groups (also referred to as video tile groups) and / or tile groups (also referred to as video tiles), where a picture may be partitioned or encoded into one or more slices / tile groups (typically non-overlapping), and each slice / tile group may include, for example, one or more blocks (e.g., CTUs) or one or more tiles, where each tile may be, for example, rectangular in shape and may include one or more blocks (e.g., CTUs), e.g., full or divided blocks.

[0091] Residual Calculation The residual calculation unit 204 may be configured to calculate a residual block 205 (also referred to as residual block 205) based on the picture block 203 and the prediction block 265 (more details about the prediction block 265 will be provided later). For example, the residual block 205 in the sample domain is obtained on a sample-by-sample (pixel-by-pixel) basis by subtracting sample values ​​of the prediction block 265 from sample values ​​of the picture block 203.

[0092] Transform The transform processing unit 206 may be configured to apply a transform, such as a discrete cosine transform (DCT) or a discrete sine transform (DST), on the sample values ​​of the residual block 205 to obtain transform coefficients 207 in the transform domain. The transform coefficients 207 are also referred to as transform residual coefficients and may represent the residual block 205 in the transform domain.

[0093] The transform processing unit 206 may be configured to apply an integer approximation of a DCT / DST, such as the transform specified for H.265 / HEVC. Compared to an orthogonal DCT transform, such an integer approximation is typically scaled by a predetermined factor. To preserve the norm of the residual block processed by the forward and inverse transforms, an additional scaling factor is applied as part of the transform process. The scaling factor is typically selected based on predetermined constraints, such as a scaling factor that is a power of two for shift operations, the bit depth of the transform coefficients, a trade-off between accuracy and implementation cost, etc. Specific scaling factors are, for example, specified for the inverse transform, e.g., by the inverse transform processing unit 212 (and for the corresponding inverse transform, by the inverse transform processing unit 312 in the video decoder 30). Then, corresponding scaling factors for the forward transform may be specified accordingly in the encoder 20, e.g., by the transform processing unit 206.

[0094] Embodiments of video encoder 20 (respectively, transform processing unit 206) may be configured to output the transform parameters, e.g., the type of transform, directly or encoded or compressed, e.g., via entropy encoding unit 270. As a result, for example, video decoder 30 can receive and use the transform parameters for decoding.

[0095] quantization The quantization unit 208 may be configured to quantize the transform coefficients 207, for example, by applying scalar quantization or vector quantization, to obtain quantized coefficients 209. The quantized coefficients 209 are also referred to as quantized transform coefficients 209 or quantized residual coefficients 209.

[0096] The quantization process may reduce the bit depth associated with some or all of the transform coefficients 207. For example, an n-bit transform coefficient may be rounded to an m-bit transform coefficient during quantization, where n is greater than m. The degree of quantization may be modified by adjusting a quantization parameter (QP). For example, for scalar quantization, different scaling may be applied to achieve finer or coarser quantization. A smaller quantization step size corresponds to finer quantization, while a larger quantization step size corresponds to coarser quantization. The applicable quantization step size may be indicated by the quantization parameter (QP). The quantization parameter may, for example, be an index into a predefined set of applicable quantization step sizes. For example, a small quantization parameter may correspond to fine quantization (small quantization step size) and a large quantization parameter may correspond to coarse quantization (large quantization step size), or vice versa. Quantization may involve division by a quantization step size, and corresponding and / or inverse dequantization may involve multiplication by the quantization step size, e.g., by the inverse quantization unit 210. Embodiments according to some standards, e.g., HEVC, may be configured to use a quantization parameter to determine the quantization step size. Typically, the quantization step size may be calculated based on the quantization parameter using a fixed-point approximation of an equation involving division. To recover the norm of the residual block, an additional scaling factor may be introduced for quantization and dequantization, which may be corrected for the scaling used in the fixed-point approximation of the equation for the quantization step size and the quantization parameter. In one embodiment, the scaling of the inverse transform and dequantization may be combined. Alternatively, customized quantization tables may be used and signaled from the encoder to the decoder, e.g., in the bitstream.Quantization is a lossy operation, where the loss increases with increasing quantization step size.

[0097] Embodiments of video encoder 20 (respectively, quantization unit 208) may be configured to output a quantization parameter (QP) directly or encoded, e.g., via entropy encoding unit 270. As a result, for example, video decoder 30 can receive and apply the quantization parameter for decoding.

[0098] Inverse Quantization The inverse quantization unit 210 is configured to apply the inverse quantization of the quantization unit 208 to the quantized coefficients, e.g., by applying the inverse of the quantization scheme applied by the quantization unit 208, based on or using the same quantization step size as the quantization unit 208, to obtain dequantized coefficients 211. The dequantized coefficients 211 are also referred to as dequantized residual coefficients 211 or references, and correspond to the transform coefficients 207—although typically not identical to the transform coefficients due to loss due to quantization.

[0099] Inverse Transform The inverse transform processing unit 212 is configured to apply an inverse transform of the transform applied by the transform processing unit 206, such as an inverse discrete cosine transform (DCT), an inverse discrete sine transform (DST), or other inverse transform, to obtain a reconstructed residual block 213 (or corresponding dequantized coefficients 213) in the sample domain. The reconstructed residual block 213 is also referred to as a transform block 213.

[0100] Reconstruction The reconstruction unit 214 (e.g., an adder or adder 214) is configured to add the transform block 213 (i.e., the reconstructed residual block 213) to the prediction block 265, for example, by adding—sample by sample—the sample values ​​of the reconstructed residual block 213 and the sample values ​​of the prediction block 265 to obtain the reconstructed block 215 in the sample domain.

[0101] filtering The loop filter unit 220 (or, for short, "loop filter" 220) is configured to filter the reconstructed block 215 to obtain a filtered block 221, or generally, to filter the reconstructed samples to obtain filtered sample values. The loop filter unit is configured, for example, to smooth pixel transitions or otherwise improve video quality. The loop filter unit 220 may include one or more loop filters, such as a deblocking filter, a sample adaptive offset (SAO) filter, or one or more other filters, such as an adaptive loop filter (ALF), a noise suppression filter (NSF), or any combination thereof. In one embodiment, the loop filter unit 220 may include a deblocking filter, an SAO filter, and an ALF filter. The order of the filtering processes may be deblocking, SAO, and ALF. In another example, a process called luma mapping with chroma scaling (LMCS) (i.e., an adaptive in-loop reshaper) is added. This processing is performed before deblocking. In another example, the deblocking process may also be applied to interior sub-block edges, such as affine sub-block edges, ATMVP sub-block edges, sub-block transform (SBT) edges, and intra-subpartition (ISP) edges. Although loop filter unit 220 is shown in FIG. 2 as an in-loop filter, in other configurations, loop filter unit 220 may be implemented as a post-loop filter. Filtered block 221 may also be referred to as filtered reconstruction block 221.

[0102] Embodiments of video encoder 20 (respectively, loop filter unit 220) may be configured to output loop filter parameters (such as SAO filter parameters, ALF filter parameters, or LMCS parameters), e.g., encoded directly or via entropy encoding unit 270. As a result, for example, decoder 30 may receive and apply the same loop filter parameters or respective loop filters.

[0103] Decoded Picture Buffer The decoded picture buffer (DPB) 230 may be a memory that stores reference pictures for encoding video data by the video encoder 20, or may be in general reference video data. The DPB 230 may be formed by any of a variety of memory devices, such as dynamic random access memory (DRAM), including synchronous dynamic random access memory (ADRAM), magnetoresistive random access memory (MRAM), resistive random access memory (RRAM), or other types of memory devices. The decoded picture buffer (DPB) 230 may be configured to store one or more filtered blocks 221. The decoded picture buffer 230 may also be configured to store other previously filtered blocks (e.g., previously reconstructed and filtered blocks 221) associated with the same current picture or a different picture, e.g., a previously reconstructed picture. Thus, for example, for inter-prediction, the DPB 230 may provide a complete previously reconstructed, i.e., decoded, picture (and corresponding reference blocks and samples) and / or a partially reconstructed current picture (and corresponding reference blocks and samples). The decoded picture buffer (DPB) 230 may also be configured to store one or more reconstructed unfiltered blocks 215, or, if the reconstructed blocks 215 are not filtered by the loop filter unit 220, generally unfiltered reconstructed samples, or any other further processed version of the reconstructed blocks or samples.

[0104] Mode Selection (Partitioning and Prediction) The mode select unit 260 includes a partitioning unit 262, an inter prediction unit 244, and an intra prediction unit 254, and is configured to receive or obtain original video data, such as original block 203 (current block 203 of current picture 17), and reconstructed video data, such as filtered and / or unfiltered reconstructed samples or blocks of the same (current) picture, and / or from one or more previously decoded pictures, such as from a decoded picture buffer 230 or other buffer (e.g., a line buffer, not shown). The reconstructed video data is used as reference picture data for prediction, such as inter prediction or intra prediction, to obtain a prediction block 265 or predictor 265.

[0105] The mode selection unit 260 may be configured to determine or select a partitioning for the current block prediction mode (including no partitioning) and prediction mode (e.g., intra or inter prediction mode) and generate a corresponding prediction block 265 used for calculating the residual block 205 and for reconstructing the reconstruction block 215.

[0106] Embodiments of mode selection unit 260 may be configured to select a partitioning and prediction mode (e.g., from those supported or available by mode selection unit 260) that provides the best match, i.e., in other words, the smallest residual (smallest residual means better compression for transmission or storage), or the smallest signaling overhead (smallest signaling overhead means better compression for transmission or storage), or that considers or balances both. Mode selection unit 260 may be configured to determine the partitioning and prediction mode based on rate-distortion optimization (RDO), i.e., to select a prediction mode that provides the smallest rate-distortion. Terms such as “best,” “minimum,” “optimum,” etc. in this context do not necessarily refer to an overall “best,” “minimum,” “optimum,” etc., but may also refer to achieving a termination criterion or selection criterion that exceeds or falls below a threshold, or that may lead to a “sub-optimal selection,” but that reduces complexity and processing time.

[0107] In other words, the partitioning unit 262 may be configured to partition pictures from a video sequence into a sequence of coding tree units (CTUs). The CTUs 203 may then be further partitioned into smaller block partitions or sub-blocks (which again form blocks), e.g., using quad-tree partitioning (QT), binary partitioning (BT), or triple-tree partitioning (TT), or any combination thereof, iteratively, and prediction may be performed on each of the block partitions or sub-blocks, e.g., where mode selection includes selecting a tree structure for the partitioned blocks 203, and a prediction mode is applied to each of the block partitions or sub-blocks.

[0108] Below, the partitioning (e.g., by partitioning unit 260) and prediction processing (by inter prediction unit 244 and intra prediction unit 254) performed by one exemplary video encoder 20 are described in more detail.

[0109] Partitioning The partitioning unit 262 may be configured to partition a picture from a video sequence into a sequence of coding tree units (CTUs). The partitioning unit 262 may then partition (or split) the coding tree units (CTUs) 203 into smaller partitions, e.g., smaller blocks of square or rectangular size. For a picture with three sample arrays, a CTU consists of an N×N block of luma samples together with two corresponding blocks of chroma samples. The maximum allowable size of a luma block in a CTU is specified as 128×128 in the currently developing Versatile Video Coding (VVC) standard, but may be specified as a value other than 128×128, e.g., 256×256, in the future. The CTUs of a picture may be clustered / grouped as slices / tile groups, tiles, or bricks. A tile covers a rectangular area of ​​the picture, and the tile may be divided into one or more bricks. A brick consists of multiple columns of CTUs within the tile. A tile that is not partitioned into multiple bricks may be referred to as a brick. However, a brick may be a true subset of a tile and not referred to as a tile. There are two modes of tile groups supported by VVC: raster-scan slice / tile group mode and rectangular slice mode. In raster-scan tile group mode, a slice / tile group contains a sequence of tiles in the tile raster scan of the picture. In rectangular slice mode, a slice contains many bricks of the picture that collectively form a rectangular region of the picture. The bricks within a rectangular slice are in the brick raster scan order of the slice. These smaller blocks (also referred to as sub-blocks) can be further partitioned into even smaller partitions.This is also referred to as tree partitioning or hierarchical tree partitioning, where a root block, e.g., root tree level 0 (hierarchical level 0, depth 0), may be recursively partitioned into two or more blocks at a node of the next lower tree level, e.g., tree level 1 (hierarchical level 1, depth 1), and these blocks may then be partitioned again into two or more blocks at the next lower level, e.g., tree level 2 (hierarchical level 2, depth 2), etc., until partitioning terminates. Termination occurs when a termination criterion is met, such as reaching a maximum tree depth or a minimum block size. Blocks that are not further partitioned are also referred to as leaf blocks or leaf nodes of the tree. A tree using a partition into two partitions is referred to as a binary tree (BT), a tree using a partition into three partitions is referred to as a ternary tree (TT), and a tree using a partition into four partitions is referred to as a quad tree (QT).

[0110] For example, a coding tree unit (CTU) may be or include a CTB for luma samples, two corresponding CTBs for chroma samples for a picture having three sample arrays, or a CTB for samples of a monochrome video or picture coded using three separate color planes and syntax structures used to code the samples. Correspondingly, a coding tree block (CTB) may be an N×N block of samples for some values ​​of N, such that the division of the components into CTBs is a partition. A coding unit (CU) may be or include a coding block for luma samples, two corresponding coding blocks for chroma samples for a picture having three sample arrays, or a coding block for samples of a monochrome video or picture coded using three separate color planes and syntax structures used to code the samples. Correspondingly, a coding block may be an M×N block of samples for some values ​​of M and N, such that the division of a CTB into coding blocks is a partition.

[0111] In an embodiment, for example, according to HEVC, a coding tree unit (CTU) may be split into CUs by using a quad-tree structure, denoted as a coding tree. The decision of whether to code a picture region using inter-picture (temporal) or intra-picture (spatial) prediction is made at the leaf CU level. Each leaf CU can be further split into one, two, or four PUs depending on the PU splitting type. Within one PU, the same prediction process is applied, and related information is transmitted to the decoder on a PU-by-PU basis. After obtaining residual blocks by applying a prediction process based on the PU split type, the leaf CU may be partitioned into transform units (TUs) according to another quad-tree structure similar to the coding tree for CUs.

[0112] In an embodiment, the combined quad trees are nested into a multitype tree using binary and ternary split segmentation structures, e.g., used to partition coding tree units, e.g., according to the latest video coding standard currently under development, referred to as Versatile Video Coding (VVC). In the coding tree structures within a coding tree unit, CUs can have either square or rectangular shapes. For example, a coding tree unit (CTU) is first partitioned by a quaternary tree. Then, quaternary tree leaf nodes can be further partitioned by a multitype tree structure. There are four split types in the multitype tree structure: vertical binary split (SPLIT_BT_VER), horizontal binary split (SPLIT_BT_HOR), vertical ternary split (SPLIT_TT_VER), and horizontal ternary split (SPLIT_TT_HOR). The multi-type tree leaf nodes are called coding units (CUs), and this segmentation is used for prediction and transform processing without any further partitioning, unless the CU is too large for the maximum transform length. This means that in most cases, CUs, PUs, and TUs have the same block size in a quad-tree with a nested multi-type tree coding block structure. An exception occurs when the maximum supported transform length is smaller than the width or height of the color components of the CU. VVC develops a unique signaling mechanism for partition split information in a quad-tree with a nested multi-type tree coding tree structure. In the signaling mechanism, a coding tree unit (CTU) is treated as the root of a quaternary tree and is first partitioned by the quarter-tree structure.Each quarter-tree leaf node (if large enough to allow it) is then further partitioned by a multitype tree structure. In the multitype tree structure, a first flag (mtt_split_cu_flag) is signaled to indicate whether the node is further partitioned, and if the node is further partitioned, a second flag (mtt_split_cu_vertical_flag) is signaled to indicate the split direction, and then a third flag (mtt_split_cu_binary_flag) is signaled to indicate whether the split is a binary split or a ternary split. Based on the values ​​of mtt_split_cu_vertical_flag and mtt_split_cu_binary_flag, the multitype tree split mode (MttSplitMode) of the CU can be derived by the decoder based on a predefined rule or table. For a given design, e.g., a 64x64 luma block and 32x32 chroma pipeline design in a VVC hardware decoder, TT splitting is prohibited if either the width or height of the luma coding block is greater than 64, as shown in Figure 6. TT splitting is also prohibited if the width or height of the chroma coding block is greater than 32. The pipeline design divides a picture into virtual pipeline data units (VPDUs), which are defined as non-overlapping units within a picture. In a hardware decoder, consecutive VPDUs are processed simultaneously by multiple pipeline stages. It is important to keep the VPDU size small because the VPDU size is roughly proportional to the buffer size in most pipeline stages. In most hardware decoders, the VPDU size can be set to the maximum transform block (TB) size. However, in VVC, ternary tree (TT) and binary tree (BT) partitions can result in an increase in VPDU size.In addition, it should be noted that if any part of a tree node block extends beyond the bottom or right side of the picture boundary, the tree node block is forced to be split until all samples of the respective coded CU are located inside the picture boundary. As an example, the Intra Sub-Partitions (ISP) tool can divide a luma intra-predicted block into two or four sub-partitions vertically or horizontally, depending on the block size.

[0113] In one example, mode select unit 260 of video encoder 20 may be configured to perform any combination of the partitioning techniques described herein.

[0114] As described above, video encoder 20 is configured to determine or select a best or optimal prediction mode from a (e.g., predetermined) set of prediction modes, which may include, for example, intra-prediction modes and / or inter-prediction modes.

[0115] Intra-Prediction The set of intra prediction modes may include 35 different intra prediction modes. For example, non-directional modes, such as DC (or average) mode and planar mode, or directional modes, as defined in HEVC. Or, it may include 67 different intra prediction modes. For example, non-directional modes, such as DC (or average) mode and planar mode, or directional modes, as defined in VVC. As one example, some conventional angular intra prediction modes are adaptively replaced with wide-angle intra prediction modes for non-square blocks, as defined in VVC. As another example, to avoid division operations for DC prediction, for non-square blocks, only the longer side is used to calculate the average. And, the result of planar mode intra prediction may be further modified by a position-dependent intra prediction combining (PDPC) method.

[0116] The intra prediction unit 254 is configured to use reconstructed samples of neighboring blocks of the same current picture to generate an intra prediction block 265 according to an intra prediction mode of the set of intra prediction modes.

[0117] Intra prediction unit 254 (or, generally, mode select unit 260) is further configured to output the intra prediction parameters (or, generally, information indicating the selected intra prediction mode for the block) to entropy encoding unit 270 in the form of syntax element 266 for inclusion in encoded video data 21. As a result, for example, video decoder 30 can receive and use the prediction parameters for decoding.

[0118] Inter prediction (including inter-layer prediction) The (or possible) set of inter prediction modes depends on the available reference pictures (i.e., previously at least partially decoded pictures, e.g., stored in DBP 230) and other inter prediction parameters, such as whether the entire reference picture or a portion of the reference picture, e.g., a search window area around the area of ​​the current block, is used to search for the best matching reference block, and / or, for example, whether pixel interpolation is applied, e.g., half / semi-pel, quarter-pel, and / or 1 / 16-pel, or not.

[0119] In addition to the prediction modes mentioned above, skip mode, direct mode, and / or other inter prediction modes may be applied.

[0120] For example, in extended merge prediction, the merge candidate list for such a mode is constructed by sequentially including the following five types of candidates: spatial MVP from spatially adjacent CUs, temporal MVP from co-located CUs, history-based MVP from a FIFO table, pairwise average MVP, and zero MV. To improve the accuracy of the MV in the merge mode, bilateral matching-based decoder-side motion vector refinement (DMVR) can be applied. The merge mode with MVD (MMDV) is derived from the merge mode with motion vector difference. The MMVD flag is signaled immediately after sending the skip flag and merge flag to specify whether the MMVD mode is used for the CU. Then, CU-level adaptive motion vector resolution (AMVR) scanning can be applied. AMVR allows the MVD of a CU to be coded with different accuracy. The MVD of the current CU can be adaptively selected depending on the prediction mode of the current CU. When a CU is coded in merge mode, combined inter / intra prediction (CIIP) mode can be applied to the current CU. To obtain CIIP prediction, a weighted average of the inter and intra prediction signals is performed. Affine motion compensation prediction: The affine motion field of a block is described by motion information of two control points (four parameters) or three control point motion vectors (six parameters). Subblock-based temporal motion vector prediction (SbTMVP) is similar to temporal motion vector prediction (TMVP) in HEVC, but predicts motion vectors of sub-CUs within the current CU. Bidirectional optical flow (BDOF), formerly known as BIO, is a simpler version that requires much less computational effort, especially in terms of the number of multiplications and the size of the multipliers.Triangle partitioning mode, in which a CU is evenly divided into two triangular partitions using either diagonal or anti-diagonal partitioning. In addition, bi-prediction mode is extended beyond simple averaging to allow for weighted averaging of two prediction signals.

[0121] The inter prediction unit 244 may include a motion estimation (ME) unit and a motion compensation (MC) unit (both not shown in FIG. 2). The motion estimation unit may be configured to receive or obtain a picture block 203 (current picture block 203 of current picture 17) and a decoded picture 231, or at least one or more previously reconstructed blocks, e.g., reconstructed blocks of one or more other / different previously decoded pictures 231, for motion estimation. For example, a video sequence may include the current picture and the previously decoded picture 231. Or, in other words, the current picture and the previously decoded picture 231 may be part of or form a sequence of pictures forming a video sequence.

[0122] The encoder 20 may be configured, for example, to select a reference block from multiple reference blocks associated with the same or different ones of multiple other pictures, and provide the reference picture (or reference picture index) and / or an offset (spatial offset) between the position (x, y coordinates) of the reference block and the position of the current block as inter-prediction parameters to the motion estimation unit, which offset is also referred to as a motion vector (MV).

[0123] The motion compensation unit is configured to obtain, e.g., receive, received inter prediction parameters and perform inter prediction based on or using the inter prediction parameters to obtain inter prediction block 265. Motion compensation performed by the motion compensation unit may include fetching or generating a prediction block based on motion / block vectors determined by motion estimation and may perform interpolation to sub-pixel accuracy. Interpolation filtering can generate additional pixel samples from known pixel samples, thus potentially increasing the number of candidate prediction blocks that can be used to code the picture block. Upon receiving a motion vector for the PU of the current picture block, the motion compensation unit may locate the prediction block pointed to by the motion vector in one of the reference picture lists.

[0124] The motion compensation unit may also generate syntax elements associated with blocks and video slices for use by video decoder 30 in decoding picture blocks of the video slices. In addition to, or as an alternative to, slices and their respective syntax elements, tile groups and / or tiles and their respective syntax elements may be generated or used.

[0125] Entropy Coding Entropy coding unit 270 may be configured to apply, for example, an entropy encoding algorithm or scheme (e.g., a variable length coding (VLC) scheme, a context-adaptive VLC scheme (CAVLC), an arithmetic coding scheme, binarization, context-adaptive binary arithmetic coding (CABAC), syntax-based context-adaptive binary arithmetic coding (SBAC), probability interval partitioning entropy (PIPE) coding, or another entropy encoding method or technique) to, or bypass (uncompress) quantization coefficients 209, inter-prediction parameters, intra-prediction parameters, loop filter parameters, and / or other syntax elements to obtain encoded video data 21, which may be output via output 272, for example, in the form of encoded bitstream 21. As a result, video decoder 30 may receive and use the decoded parameters. Encoded bitstream 21 may be transmitted to video decoder 30 or may be stored in memory for later transmission or retrieval by video decoder 30.

[0126] Other structural variations of the video encoder 20 may be used to encode the video stream. For example, a non-transform-based encoder 20 may quantize the residual signal directly for a given block or frame, without the transform processing unit 206. In another embodiment, the encoder 20 may combine the quantization unit 208 and the inverse quantization unit 210 into a single unit.

[0127] Decoder and decoding method 3 shows an example of a video decoder 30 configured to implement the techniques of the present application. Video decoder 30 is configured to receive encoded video data 21 (e.g., encoded bitstream 21), e.g., as encoded by encoder 20, to obtain a decoded picture 331. The encoded video data or bitstream includes information for decoding the encoded video data, e.g., data representing picture blocks (and / or tile groups or tiles) of an encoded video slice and associated syntax elements.

[0128] 3, decoder 30 includes an entropy decoding unit 304, an inverse quantization unit 310, an inverse transform processing unit 312, a reconstruction unit 314 (e.g., summer 314), a loop filter 320, a decoded picture buffer (DBP) 330, a mode application unit 360, an inter prediction unit 344, and an intra prediction unit 354. Inter prediction unit 344 may be or may include a motion compensation unit. Video decoder 30, in some examples, may perform a decoding path that is generally reciprocal to the encoding path described with respect to video encoder 100 from FIG. 2.

[0129] As described with respect to encoder 20, inverse quantization unit 210, inverse transform processing unit 212, reconstruction unit 214, loop filter 220, decoded picture buffer (DPB) 230, inter prediction unit 344, and intra prediction unit 354 are also referred to as forming a “built-in decoder” of video encoder 20. Accordingly, inverse quantization unit 310 may be functionally identical to inverse quantization unit 110, inverse transform processing unit 312 may be functionally identical to inverse transform processing unit 212, reconstruction unit 314 may be functionally identical to reconstruction unit 214, loop filter 320 may be functionally identical to loop filter 220, and decoded picture buffer 330 may be functionally identical to decoded picture buffer 230. Accordingly, the descriptions provided for the respective units and functions of video decoder 20 also apply correspondingly to the respective units and functions of video decoder 30.

[0130] Entropy Decoding the entropy decoding unit 304 is configured to analyze the bitstream 21 (or generally the encoded video data 21) and, for example, perform entropy decoding on the encoded video data 21; For example, entropy decoding unit 304 obtains quantization coefficients 309 and / or decoded coding parameters (not shown in FIG. 3 ), such as some or all of inter-prediction parameters (e.g., reference picture indices and motion vectors), intra-prediction parameters (e.g., intra-prediction modes or indices), transform parameters, quantization parameters, loop filter parameters, and / or other syntax elements. Entropy decoding unit 304 may be configured to apply a decoding algorithm or scheme corresponding to the encoding scheme, as described with respect to entropy coding unit 270 of encoder 20. Entropy decoding unit 304 may further be configured to provide the inter-prediction parameters, intra-prediction parameters, and / or other syntax elements to mode application unit 360 and other parameters to other units of decoder 30. Video decoder 30 may receive syntax elements at a video slice level and / or a video block level. In addition to or as an alternative to slices and their respective syntax elements, tile groups and / or tiles and their respective syntax elements may be received and / or used.

[0131] Inverse Quantization Inverse quantization unit 310 may be configured to receive a quantization parameter (QP) (or generally, information related to inverse quantization) and quantization coefficients from encoded video data 21 (e.g., by parsing and / or decoding by entropy decoding unit 304), and to apply inverse quantization to decoded quantized data 309 based on the quantization parameter, to obtain dequantized coefficients 311, which may also be referred to as transform coefficients 311. The inverse quantization process may include using the quantization parameter determined by video encoder 20 for each video block within a video slice (or tile or tile group) to determine the degree of quantization, and similarly, the degree of inverse quantization to be applied.

[0132] Inverse Transform The inverse transform processing unit 312 may be configured to receive the dequantized coefficients 311, also referred to as transform coefficients 311, and apply a transform to the dequantized coefficients 311 to obtain the reconstructed residual block 213 in the sample domain. The reconstructed residual block 213 may also be referred to as a transform block 313. The transform may be an inverse transform, such as an inverse DCT, an inverse DST, an inverse integer transform, or a conceptually similar inverse transform process. The inverse transform processing unit 312 may further be configured to receive transform parameters or corresponding information from the encoded video data 21 (e.g., by analysis and / or decoding by the entropy decoding unit 304) and determine the transform to apply to the dequantized coefficients 311.

[0133] Reconstruction The reconstruction unit 314 (e.g., an adder or adder 314) may be configured to add the reconstructed residual block 313 to the prediction block 365 to obtain a reconstructed block 315 in the sample domain, for example, by adding sample values ​​of the reconstructed residual block 313 and sample values ​​of the prediction block 365.

[0134] filtering The loop filter unit 320 is configured to filter the reconstructed block 315 (either in the coding loop or after the coding loop) to obtain a filtered block 321, e.g., to smooth pixel transitions or otherwise improve video quality. The loop filter unit 320 may include one or more loop filters, such as a deblocking filter, a sample adaptive offset (SAO) filter, or one or more other filters, e.g., an adaptive loop filter (ALF), a noise suppression filter (NSF), or any combination thereof. In one example, the loop filter unit 320 may include a deblocking filter, an SAO filter, and an ALF filter. The filtering process order may be deblocking filter, SAO, and ALF. In another example, a process called luma mapping with chroma scaling (LMCS) (i.e., an adaptive in-loop reshaper) is added. This process is performed before deblocking. In another example, the deblocking filter process may also be applied to interior sub-block edges, such as affine sub-block edges, ATMVP sub-block edges, sub-block transform (SBT) edges, and intra-sub-partition (ISP) edges. Although loop filter unit 320 is shown in FIG. 3 as an in-loop filter, in other configurations, loop filter unit 320 may be implemented as a post-loop filter.

[0135] Decoded Picture Buffer The decoded video blocks 321 of the picture are then stored in a decoded picture buffer 330. The buffer stores the decoded picture 331 as a reference picture for subsequent motion compensation for other pictures and / or for output respective display.

[0136] The decoder 30 is arranged to output the decoded pictures 311, for example via an output 312, for presentation or display to a user.

[0137] Prediction The inter prediction unit 344 may be identical to the inter prediction unit 244 (in particular the motion compensation unit), and the intra prediction unit 354 may be identical in function to the inter prediction unit 254 and performs the division or partitioning decision and prediction based on the partitioning and / or prediction parameters or respective information received from the encoded video data 21 (e.g., by analysis and / or decoding, e.g., by the entropy decoding unit 304). The mode application unit 360 may be configured to perform prediction (intra prediction or inter prediction) for each block based on the reconstructed picture, block or respective samples (filtered or unfiltered) to obtain a prediction block 365.

[0138] When a video slice is coded as an intra-coded (I) slice, intra prediction unit 354 of mode application unit 360 is configured to generate a predictive block 365 for a picture block of the current video slice based on a signaled intra-prediction mode and data from a previously decoded block of the current picture. When a video picture is coded as an inter-coded (i.e., B or P) slice, inter prediction unit 344 (e.g., a motion compensation unit) of mode application unit 360 is configured to generate a predictive block 365 for a video block of the current video slice based on a motion vector and other syntax elements received from entropy decoding unit 304. For inter prediction, the predictive block may be generated from one of the reference pictures in one of the reference picture lists. Video decoder 30 may construct the reference frame lists, List 0 and List 1, using a default construction technique based on the reference pictures stored in DPB 330. The same or similar may apply to embodiments that use tile groups (e.g., video tile groups) and / or tiles (e.g., video tiles) in addition to or instead of slices (e.g., video slices). For example, video may be coded using I, P, or B tile groups and / or tiles.

[0139] Mode application unit 360 is configured to determine prediction information for video blocks of the current video slice by analyzing motion vectors or related information and other syntax elements, and use the prediction information to generate predictive blocks for the current video block to be decoded. For example, mode application unit 360 uses some of the received syntax elements to determine a prediction mode used to code video blocks of the video slice, a slice type for inter prediction (e.g., B slice, P slice, or GPB slice), configuration information for one or more of the reference picture lists for the slice, motion vectors for each inter-encoded video block of the slice, inter-prediction status for each inter-coded video block of the slice, and other information for decoding video blocks in the current video slice. The same or similar may apply to embodiments that use tile groups (e.g., video tile groups) and / or tiles (e.g., video tiles) in addition to, or instead of, slices (e.g., video slices). For example, video may be coded using I, P, or B tile groups and / or tiles.

[0140] 3, embodiments of video decoder 30 may be configured to partition and / or decode pictures by using slices (also referred to as video slices), where a picture may be partitioned or decoded using one or more slices (typically non-overlapping), and each slice may include one or more blocks (e.g., CTUs) or one or more block groups (e.g., tiles (H.265 / HEVC and VVC) or bricks (VVC)).

[0141] As shown in FIG. 3, embodiments of video decoder 30 may be configured to partition and / or decode a picture using slices / tile groups (also referred to as video tile groups) and / or tiles (also referred to as video tiles). Here, a picture may be partitioned or decoded using one or more slices / tile groups (typically non-overlapping). Each slice / tile group may include, for example, one or more blocks (e.g., CTUs) or one or more tiles. Here, each tile may be, for example, rectangular in shape and may include one or more blocks (e.g., CTUs), e.g., full or divided blocks.

[0142] Other variations of the video decoder 30 may be used to decode the encoded video data 21. For example, the decoder 30 may generate the output video stream without the loop filtering unit 320. For example, a non-transform-based decoder 30 may inverse quantize the residual signal directly for a given block or frame, without the inverse transform processing unit 312. In another embodiment, the video decoder 30 may combine the inverse quantization unit 310 and the inverse transform processing unit 312 into a single unit.

[0143] It should be understood that in the encoder 20 and the decoder 30, the processing result of the current step may be further processed and then output to the next step. For example, after interpolation filtering, motion vector derivation, or loop filtering, further operations such as clipping or shifting may be performed on the processing result of the interpolation filtering, motion vector derivation, or loop filtering.

[0144] It should be noted that further operations may be applied to the derived motion vector of the current block (including, but not limited to, control point motion vectors in affine mode, sub-block motion vectors in affine, planar, and ATMVP modes, temporal motion vectors, etc.). For example, the value of a motion vector is constrained to a predefined range according to its representation bits. If the representation bits of a motion vector are bitDepth, the range is -2^(bitDepth-1) to 2^(bitDepth-1)-1, where "^" means exponentiation. For example, if bitDepth is set equal to 16, the range is -32768 to 32767, and if bitDepth is set equal to 18, the range is -131072 to 131071. For example, the derived motion vector values ​​(e.g., MVs of 4x4 sub-blocks in one 8x8 block) are constrained so that the maximum difference between the integer parts of the MVs of four 4x4 sub-blocks is less than or equal to N pixels, such as less than or equal to 1 pixel. Here, we provide two methods for constraining motion vectors according to bit depth.

[0145] 4 is a schematic diagram of a video coding device 400 according to one embodiment of the present disclosure. The video coding device 400 is suitable for implementing the disclosed embodiments as described herein. In one embodiment, the video coding device 400 may be a decoder, such as the video decoder 30 of FIG. 1A, or an encoder, such as the video encoder 20 of FIG. 1A.

[0146] Video coding device 400 includes an ingress port 410 (or input port 410) and a receiver unit (Rx) 420 for receiving data, a processor, logic unit, or central processing unit (CPU) 430 for processing the data, a transmitter unit (Tx) 440 and an egress port 450 (or output port 450) for transmitting the data, and a memory 460 for storing the data. Video coding device 400 may also include optical-to-electrical (OE) and electrical-to-optical (EO) components coupled to ingress port 410, receiver unit 420, transmitter unit 440, and egress port 450 for the ingress or egress of optical or electrical signals.

[0147] The processor 430 is implemented in hardware and software. The processor 430 may be implemented as one or more CPU chips, cores (e.g., as a multi-core processor), FPGA, ASIC, and DSP. The processor 430 communicates with the ingress port 410, the receiver unit 420, the transmitter unit 440, the egress port 450, and the memory 460. The processor 430 includes a coding module 470. The coding module 470 implements the disclosed embodiments described above. For example, the coding module 470 performs, processes, prepares, or provides various coding operations. The inclusion of the coding module 470 thus provides substantial improvements to the functionality of the video coding device 400 and results in the transformation of the video coding device 400 into a different state. Alternatively, the coding module 470 is implemented as instructions stored in the memory 460 and executed by the processor 430.

[0148] Memory 460 may include one or more disks, tape drives, and solid-state drives, and may be used to store programs when such programs are selected for execution and as an overflow data storage device to store instructions and data retrieved during program execution. Memory 460 may be, for example, volatile and / or non-volatile, and may be read-only memory (ROM), random access memory (RAM), ternary content-addressable memory (TCAM), and / or static random access memory (SRAM).

[0149] FIG. 5 is a schematic block diagram of an apparatus 500 that can be used as either or both of source device 12 and destination device 14 of FIG. 1, according to one exemplary embodiment. Processor 502 in device 500 may be a central processing unit. Alternatively, processor 502 may be any other type of device or devices now existing or later developed that are capable of manipulating or processing information. While the disclosed embodiments may be implemented using a single processor, e.g., processor 502, as shown, advantages in speed and efficiency may be achieved using more than one processor.

[0150] The memory 504 in the device 500 may be a read-only memory (ROM) device or a random access memory (RAM) device in implementation. Any other suitable type of storage device may be used as the memory 504. The memory 504 may include code and data 506 accessed by the processor 502 using a bus 512. The memory 504 may further include an operating system 508 and application programs 510. The application programs 510 include at least one program that enables the processor 502 to perform the methods described herein. For example, the application programs 510 may include applications 1 through N and may further include a video coding application that performs the methods described herein. The device 500 may also include one or more output devices, such as a display 518. The display 518, in one example, may be a touch-sensitive display that combines a display with a touch-sensitive element operable to sense touch input. The display 518 may be coupled to the processor 502 via the bus 512.

[0151] Although shown here as a single bus, bus 512 of device 500 may be comprised of multiple buses. Additionally, secondary storage device 514 may be directly coupled to other components of device 500 or accessed over a network, and may include a single integrated unit, such as a memory card, or multiple units, such as multiple memory cards. Device 500 may therefore be implemented in a wide variety of configurations.

[0152] Scalable coding Scalable coding includes quality scalable (PSNR scalable), spatial scalable, etc. For example, as shown in Figure 6, a sequence may be downsampled to a lower spatial resolution version. Both the lower spatial resolution version and the original spatial resolution (high spatial resolution) version are encoded. Typically, the lower spatial resolution is coded first and used as a reference for the higher spatial resolution, which is coded later.

[0153] To describe layer information (number, dependency, output), there is a VPS (Video Parameter Set) defined as follows: [Table 1] vps_max_layers_minus1 plus1 specifies the maximum number of layers allowed in each CVS that references the VPS. vps_all_independent_layers_flag equal to 1 specifies that all layers in the CVS are coded independently without using inter-layer prediction. vps_all_independent_layers_flag equal to 0 specifies that one or more layers in the CVS may use inter-layer prediction. If not present, the value of vps_all_independent_layers_flag is inferred to be equal to 1. If vps_all_independent_layers_flag is equal to 1, the value of vps_independent_layer_flag[i] is inferred to be equal to 1. If vps_all_independent_layers_flag is equal to 0, the value of vps_independent_layer_flag[0] is inferred to be 1. vps_layer_id[i] specifies the nuh_layer_id value of the ith layer. For two non-negative integer values ​​of m and n, if m is less than n, the value of vps_layer_id[m] is less than vps_layer_id[n]. vps_independent_layer_flag[i] equal to 1 specifies that the layer with index i does not use inter-layer prediction. vps_independent_layer_flag[i] equal to 0 specifies that the layer with index i can use inter-layer prediction and vps_layer_dependency_flag[i] is present in the VPS. vps_direct_direct_dependency_flag[i][j] equal to 0 specifies that the layer with index j is not a direct reference layer for the layer with index i. vps_direct_direct_dependency_flag[i][j] equal to 1 specifies that the layer with index j is a direct reference layer for the layer with index i. If vps_direct_dinercy_dependency_flag[i][j] is not present for i and j in the range 0 to vps_max_layers_minus1, it is inferred to be equal to 0. The variable DirectDependentLayerIdx[i][j] specifies the jth direct dependency layer of the ith layer and is derived as follows:

number

number

[0154] DPB Management and Reference Picture Marking To manage these reference pictures in the decoding process, decoded pictures need to be kept in a decoding picture buffer (DPB) for reference use in subsequent picture decoding. To indicate these pictures, their picture order count (POC) information needs to be directly or indirectly signaled in the slice header. Generally, there are two reference picture lists: list0 and list1. And, to signal a picture in the list, a reference picture index also needs to be included. For uni-prediction, reference pictures are fetched from one reference picture list, and for bi-prediction, reference pictures are fetched from two reference picture lists. All reference pictures are stored in the DPB. All pictures in the DPB are marked as "used for long-term reference," "used for short-term reference," or "unused for reference," and there is only one of the three statuses. Once a picture is marked as "reference unused", it is not used for reference at all and can be removed from the DPB if it does not need to be stored for output. The reference picture status can be signaled in the slice header or can be derived from the slice header information. A new reference picture management method called RPL (reference picture list) method has been proposed. RPL proposes an entire reference picture set or sets for the currently coded picture, and the reference pictures in the reference picture set are used for decoding the current picture or future (later or next) pictures. Thus, RPL reflects picture information in DPB, and even if a reference picture is not used for reference for the current picture, it is required to be stored in RPL if it is used for reference for the next picture. After a picture is reconstructed, it is stored in the DPB and is marked by default as "short-term reference." DPB management operations start after parsing the RPL information in the slice header.

[0155] Reference Picture List Configuration Reference picture information can be signaled via the slice header. Also, there can be several RPL candidates in the sequence parameter set (SPS). In this case, the slice header can include an RPL index to obtain the required RPL information without signaling the entire RPL syntax structure. Alternatively, the entire RPL syntax structure can be signaled within the slice header.

[0156] Introducing the RPL method To save cost bits of RPL signaling, there can be several RPL candidates in the SPS. A picture can use the RPL index (ref_pic_list_idx[i]) to obtain RPL information from the SPS. The RPL candidates are signaled as follows: [Table 2]

[0157] The semantics are as follows: rpl1_sim_as_rpl0_flag equal to 1 specifies that the syntax structures num_ref_pic_lists_in_sps[1] and ref_pic_list_struct(1,rplsidx) are not present, and the following applies: - The value of num_ref_pic_lists_in_sps[1] is assumed to be equal to the value of num_ref_pic_lists_in_sps[0]. The value of each syntax element in ref_pic_list_struct(1,rplsIdx) is inferred to be equal to the value of the corresponding syntax element in ref_pic_list_struct(0,rplsIdx) for rplsIdx in the range 0 to num_ref_pic_lists_in_sps[0]-1. num_ref_pic_lists_in_sps[i] specifies the number of ref_pic_list_struct(listIdx, rplsIdx) syntax structures contained in the SPS that have listIdx equal to 1. The value of num_ref_pic_lists_in_sps[i] shall range from 0 to 64, inclusive.

[0158] Besides obtaining the RPL information based on the RPL index from the SPS, the RPL information can be signaled in the slice header. [Table 3] ref_pic_list_sps_flag[i] equal to 1 specifies that the reference picture list i of the current slice is derived based on one of the ref_pic_list_struct(listIdx, rplsIdx) syntax structures with listIdx equal to i in the SPS. ref_pic_list_sps_flag[i] equal to 0 specifies that the reference picture list i of the current slice is derived based on the ref_pic_list_struct(listIdx, rplsIdx) syntax structure with listIdx equal to i that is directly contained in the slice header of the current picture. If ref_pic_list_sps_flag[i] is not present, the following applies: - If num_ref_pic_lists_in_sps[i] is equal to 0, the value of ref_pic_list_sps_flag[i] is inferred to be equal to 0. - Otherwise (num_ref_pic_lists_in_sps[i] is greater than 0), if rpl1_idx_present_flag is equal to 0, the value of ref_pic_list_sps_flag[1] is inferred to be equal to ref_pic_list_sps_flag[0]. - Otherwise, the value of ref_pic_list_sps_flag[i] is inferred to be equal to pps_ref_pic_list_sps_idc[i]-1. ref_pic_list_idx[i] specifies the index of the ref_pic_list_struct(listIdx,rplsIdx) syntax structure with listIdx equal to i that is used to derive the reference picture list i of the current picture within the list of ref_pic_list_struct(listIdx,rplsIdx) syntax structures with listIdx equal to i contained in the SPS. The syntax element ref_pic_list_idx[i] is represented by Ceil(Log2(num_ref_pic_lists_in_sps[i])) bits. If not present, the value of ref_pic_list_idx[i] is inferred to be equal to 0. The value of ref_pic_list_idx[i] shall range from 0 to num_ref_pic_lists_in_sps[i]-1, inclusive. If ref_pic_list_sps_flag[i] is equal to 1 and num_ref_pic_lists_in_sps[i] is equal to 1, the value of ref_pic_list_idx[i] is inferred to be equal to 0. If ref_pic_list_sps_flag[i] is equal to 1 and rpl1_idx_present_flag is equal to 0, the value of ref_pic_list_idx[1] is inferred to be equal to ref_pic_list_idx[0]. The variable RplsIdx[i] is derived as follows:

number

number

number

[0159] The syntax structure of RPL is as follows: [Table 4] num_ref_entries[listIdx][rplsIdx] specifies the number of entries in the ref_pic_list_struct(listIdx,rplsIdx) syntax structure. The value of num_ref_entries[listIdx][rplsidx] shall be in the range from 0 to sps_max_dec_pic_buffering_minus1+14, inclusive. ltrp_in_slice_header_flag[listIdx][rplsIdx] equal to 0 specifies that the POC LSB of the LTRP entry in the ref_pic_list_struct(listIdx,rplsIdx) syntax structure is present in the ref_pic_list_struct(listIdx,rplsIdx) syntax structure. ltrp_in_slice_header_flag[listIdx][rplsIdx] equal to 1 specifies that the POC LSB of the LTRP entry in the ref_pic_list_struct(listIdx,rplsIdx) syntax structure is not present in the ref_pic_list_struct(listIdx,rplsIdx) syntax structure. inter_layer_ref_pic_flag[listIdx][rplsIdx][i] equal to 1 specifies 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] equal to 0 specifies that the i-th entry in the ref_pic_list_struct(listIdx,rplsIdx) syntax structure is not an ILRP entry. If not present, the value of inter_layer_ref_pic_flag[listIdx][rplsIdx][i] is inferred to be equal to 0. st_ref_pic_flag[listIdx][rplsIdx][i] equal to 1 specifies 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] equal to 0 specifies that the i-th entry in the ref_pic_list_struct(listIdx,rplsIdx) syntax structure is an LTRP entry. If inter_layer_ref_pic_flag[listIdx][rplsIdx][i] is equal to 0 and st_ref_pic_flag[listIdx][rplsIdx][i] is not present, the value of st_ref_pic_flag[listIdx][rplsIdx][i] is inferred to be equal to 1. The variables NumLtrpEntries[listIdx][rplsIdx] are derived as follows:

number

number

number

[0160] Some general explanations regarding the RPL structure For each list, there is an RPL structure. First, num_ref_entries[listIdx][rplsIdx] is signaled to indicate the number of reference pictures in the list. ltrp_in_slice_header_flag[listIdx][rplsIdx] is used to indicate whether LSB (Least Significant Bit) information is signaled in the slice header. If the current reference picture is not an inter-layer reference picture, st_ref_pic_flag[listIdx][rplsIdx][i] indicates whether it is a long-term reference picture. If it is a short-term reference picture, POC information (abs_delta_poc_st and strp_entry_sign_flag) is signaled. If ltrp_in_in_slice_header_flag[listIdx][rplsIdx] is zero, rpls_poc_lsb_lt[listIdx][rplsIdx][j+++] is used to derive the LSB information of the current reference picture. The MSB (Most Significant Bit) can be derived directly or based on the information in the slice header (delta_poc_msb_present_flag[i][j] and delta_poc_msb_cycle_lt[i][j]).

[0161] Decoding process for reference picture list construction This process is invoked at the start of the decoding process for each slice of a non-IDR picture. Reference pictures are addressed through reference indices. A reference index is an index into a 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 (i.e., RefPicList[0]) is used in decoding the slice data. When decoding a B slice, both reference picture list 0 and reference picture list 1 (i.e., RefPicList[1]) are used in decoding the slice data. At the start of the decoding process for each slice of a non-IDR picture, the reference picture lists RefPicList[0] and RefPicList[1] are derived. The reference picture lists are used in marking reference pictures as specified in clause 8.3.3 or in decoding slice data. NOTE 1 - For an I-slice of a non-IDR picture that is not the first slice of the picture, RefPicList[0] and RefPicList[1] may be derived for bitstream conformance checking, but their derivation is not required for decoding the current picture or pictures that follow it in decoding order. For a P-slice that is not the first slice of the picture, RefPicList[1] may be derived for bitstream conformance checking, but its derivation is not required for decoding the current picture or pictures that follow it in decoding order. The reference picture lists RefPicList[0] and RefPicList[1] are configured as follows:

number

number

[0162] Decoding Process for Reference Picture Marking This process is invoked once per picture after the decoding of the slice header and the decoding process for constructing the reference picture list for the slice, but before the decoding of the slice data, as specified in clause 8.3.2. This process may result in one or more reference pictures in the DPB being marked as "reference unused" or "long-term reference". A decoded picture in a DPB may be marked as "reference-free," "short-term reference," or "long-term reference," but only one of these three at any given time during the operation of the decoding process. Assigning one of these markings to a picture implicitly removes another of these markings, if applicable. When a picture is referred to as being marked as "reference," this refers collectively to pictures that are marked as "short-term reference" or "long-term reference" (but not both). STRPs and ILRPs are identified by their nuh_layer_id and PicOrderCntVal values. LTRPs are identified by their nuh_layer_id value and Log2(MaxLtPicOrderCntLsb) LSBs of their PicOrderCntVal value. If the current picture is a CLVSS picture, all current reference pictures in the DPB (if any) that have the same nuh_layer_id as the current picture are marked as "reference unused". Otherwise, the following applies: - For each LTRP entry in RefPicList[0] or RefPicList[1], if the referenced picture is a STRP with the same nuh_layer_id as the current picture, then the picture is marked as "long term reference". - Each reference picture with the same nuh_layer_id as the current picture in the DPB that is not referenced by any entry in RefPicList[0] or RefPicList[1] is marked as "reference unused". - For each ILRP entry in RefPicList[0] or RefPicList[1], the referenced picture is marked as "long-term reference".

[0163] Note that here the ILRP (Inter-layer Reference Picture) is marked as "long term reference".

[0164] Within the SPS, there are two syntaxes related to inter-layer reference information. [Table 5] sps_video_parameter_set_id, if greater than 0, specifies the value of vps_video_parameter_set_id for the VPS referenced by the SPS. If sps_video_parameter_set_id is equal to 0, the SPS does not reference a VPS, and the VPS is not referenced when decoding each CVS with reference to the SPS. long_term_ref_pics_flag equal to 0 specifies that the LTRP is not used for inter prediction of any coded pictures in the CVS. long_term_ref_pics_flag equal to 1 specifies that the LTRP may be used for inter prediction of one or more coded pictures in the CVS. inter_layer_ref_pics_present_flag equal to 0 specifies that ILRP is not used for inter prediction of any coded pictures in the CVS. inter_layer_ref_pics_flag equal to 1 specifies that ILRP may be used for inter prediction of one or more coded pictures in the CVS. If sps_video_parameter_set_id is equal to 0, the value of inter_layer_ref_pics_present_flag is inferred to be 0.

[0165] A brief explanation is as follows: The long_term_ref_pics_flag is used to indicate whether LTRP can be used in the decoding process. The inter_layer_ref_pics_present_flag is used to indicate whether ILRP can be used in the decoding process.

[0166] Thus, if inter_layer_ref_pics_present_flag is equal to 1, there may be an ILRP that is used in the decoding process and is marked as "for long term reference". In this case, there is an LTRP that is used in the decoding process even if long_term_ref_pics_flag is equal to 0. Thus, there is a conflict with the semantics of long_term_ref_pics_flag. In existing methods, some syntax elements for inter-layer reference information are always signaled without considering the index of the current layer. This invention proposes to add some conditions to the syntax elements to improve the signaling efficiency.

[0167] Since long_term_ref_pics_flag is only used to control the parsing of ltrp_in_slice_header_flag and st_ref_pic_flag, the semantic is modified to control the parsing of flags parsing in RPL. The syntax element for inter-layer reference information is signaled taking into account the index of the current layer. If the information can be derived from the index of the current layer, the information does not need to be signaled.

[0168] Since long_term_ref_pics_flag is only used to control the parsing of ltrp_in_slice_header_flag and st_ref_pic_flag, the semantics are modified to control the parsing of flags parsing in RPL. The syntax element for inter-layer reference information is signaled taking into account the index of the current layer. If the information can be derived from the index of the current layer, the information does not need to be signaled.

[0169] First embodiment of the present invention [Semantics] (Fix the semantics of long_term_ref_pics_flag to remove the inconsistency between LTRP and ILRP)

[0170] Since long_term_ref_pics_flag is only used to control the parsing of ltrp_in_slice_header_flag and st_ref_pic_flag, the semantics are modified as follows: long_term_ref_pics_flag equal to 1 specifies that ltrp_in_slice_header_flag, st_ref_pic_flag are present in the syntax structure ref_pic_list_struct(listIdx, rplsIdx). long_term_ref_pics_flag equal to 0 specifies that these syntax elements are not present in the syntax structure ref_pic_list_struct(listIdx, rplsIdx). long_term_ref_pics_flag equal to 0 specifies that LTRP is not used for inter prediction of any coded pictures in the CVS. long_term_ref_pics_flag equal to 1 specifies that LTRP may be used for inter prediction of one or more coded pictures in the CVS. The semantics can also be modified to exclude ILRP as follows: long_term_ref_pics_flag equal to 0 specifies that the LTRP is not used for inter prediction of coded pictures in the CVS. long_term_ref_pics_flag equal to 1 specifies that the LTRP may be used for inter prediction of one or more coded pictures in the CVS, where the LTRP does not include an ILRP (inter-layer reference picture).

[0171] Second embodiment of the present invention [VPS]

[0172] Suggestion 1: Conditional signaling of vps_direct_direct_dependency_flag[i][j] (inter-layer reference information is signaled taking into account the index of the current layer, eliminating redundant information signaling and improving coding efficiency.)

[0173] Option 1.A: Note that if i is equal to 1, it means that layer 1 needs to reference other layers. On the other hand, vps_direct_direct_dependency_flag[i][j] does not need to be signaled, since only layer 0 can be a reference layer. Only if i is greater than 1, vps_direct_direct_dependency_flag[i][j] needs to be signaled. [Table 6] vps_direct_direct_dependency_flag[i][j] equal to 0 specifies that the layer with index j is not a direct reference layer for the layer with index i. vps_direct_direct_dependency_flag[i][j] equal to 1 specifies that the layer with index j is a direct reference layer for the layer with index i. If vps_direct_dinercy_dinercy_flag[i][j] is not in the range from 0 to vps_max_layers_minus1, inclusive, for i and j, then if i is equal to 1 and vps_independent_layer_flag[i] is equal to 0, then vps_direct_direct_dependent_flag[i][j] is inferred to be equal to 1, otherwise it is inferred to be equal to 0.

[0174] Option 1.B: In addition to the above implementation method (Option 1.A), there is also Option 1.B, which means that if all values ​​of vps_direct_direct_dependency_flag[i][j] are equal to 0, for i and j in the range from 0 to i-1 inclusive, and for vps_independent_layer_flag[i] equal to 0 and for j in the range from 0 to i-2 inclusive, then the value of vps_direct_direct_dependency_flag[i][i-1] does not need to be signaled and is inferred to be equal to 1. [Table 7] vps_direct_direct_dependency_flag[i][j] equal to 0 specifies that the layer with index j is not a direct reference layer for the layer with index i. vps_direct_direct_dependency_flag[i][j] equal to 1 specifies that the layer with index j is a direct reference layer for the layer with index i. If vps_direct_dinercy_dinercy_flag[i][j] is not in the range from 0 to vps_max_layers_minus1, inclusive, for i and j, then if vps_independent_layer_flag[i] is equal to 0, j is equal to 0, and the value of SumDependencyFlag is equal to 0, then vps_direct_direct_dependency_flag[i][j] is inferred to be equal to 1, otherwise it is inferred to be equal to 0.

[0175] Suggestion 2: Semantic constraints on vps_direct_direct_dependency_flag[i][j] We can also constrain the semantics of vps_direct_direct_depency_flag[i][j] without changing the syntax signaling method or syntax tables. Basically, for i, if the layer with index i is a dependent layer (vps_independent_layer_flag[i] is equal to 0), then at least one value of vps_direct_direct_dependency_flag[i][j] should be equal to 1, with j ranging from 0 to i-1. Alternatively, the sum of vps_direct_direct_dependency_flag[i][j] should not be equal to 0, with j ranging from 0 to i-1, or should be greater than or equal to 1 (e.g., >= 1). Or, it should be greater than 0 (e.g., > 0).

[0176] Option 2.A: vps_direct_direct_dependency_flag[i][j] equal to 0 specifies that the layer with index j is not a direct reference layer for the layer with index i. vps_direct_direct_dependency_flag[i][j] equal to 1 specifies that the layer with index j is a direct reference layer for the layer with index i. vps_direct_dinercy_dependency_flag[i][j] is inferred to be equal to 0 if, for i and j, it is not present in the range from 0 to vps_max_layers_minus1, inclusive, where, for i and j in the range from 0 to i-1, inclusive, and if vps_independent_layer_flag[i] is equal to 0, the sum of vps_direct_direct_depency_flag[i][j] is greater than 0.

[0177] Option 2.B: vps_direct_direct_dependency_flag[i][j] equal to 0 specifies that the layer with index j is not a direct reference layer for the layer with index i. vps_direct_direct_dependency_flag[i][j] equal to 1 specifies that the layer with index j is a direct reference layer for the layer with index i. vps_direct_inercy_dependency_flag[i][j] is inferred to be equal to 0 if it is not present for i and j in the range from 0 to vps_max_layers_minus1, inclusive, where, for i and j in the range from 0 to i-1, inclusive, and if vps_independent_layer_flag[i] is equal to 0, then at least one value of vps_direct_direct_depency_flag[i][j] is equal to 1.

[0178] Suggestion 3: Proposal 1+Proposal 2

[0179] Option 3: In fact, Option 1 and Option 2 can be combined to form other implementation methods, such as Operation 1.B + Operation 2.B. [Table 8] vps_direct_direct_dependency_flag[i][j] equal to 0 specifies that the layer with index j is not a direct reference layer for the layer with index i. vps_direct_direct_dependency_flag[i][j] equal to 1 specifies that the layer with index j is a direct reference layer for the layer with index i. If vps_direct_direct_dependency_flag[i][j] is not present in the range from 0 to vps_max_layers_minus1, inclusive, for i and j, then if vps_independence_layer_flag[i] is equal to 0 and j is equal to i-1 and the value of SumDependencyFlag is equal to 0, then vps_direct_direct_dependency_flag[i][j] is inferred to be equal to 1, otherwise it is inferred to be equal to 0. Here, for i and j in the range from 0 to i-1, inclusive, and if vps_independent_layer_flag[i] is equal to 0, then at least one value of vps_direct_direct_depency_flag[i][j] is equal to 1.

[0180] The bonding method is not limited here and can be as follows: The same applies to Operation 1.A + Operation 2.B. The same applies to Operation 1.A + Operation 2.A. The same applies to Operation 1.B + Operation 2.A.

[0181] Third embodiment of the present invention [sps] [sps] (Inter-layer reference information is signaled taking into account the index of the current layer, eliminating redundant information signaling and improving coding efficiency.) Note that here, if sps_video_parameter_set_id is equal to 0, it means that there are no multiple layers, and therefore there is no need to signal inter_layer_ref_pics_flag, and the flag is 0 by default. [Table 9] inter_layer_ref_pics_present_flag equal to 0 specifies that ILRP is not used for inter prediction of any coded pictures in the CVS. inter_layer_ref_pics_flag equal to 1 specifies that ILRP may be used for inter prediction of one or more coded pictures in the CVS. If sps_video_parameter_set_id is 0 and inter_layer_ref_pics_flag is not present, the value of inter_layer_ref_pics_present_flag is inferred to be equal to 0. Note that if GeneralLayerIdx[nuh_layer_id] is equal to 0, the current layer is the 0th layer and cannot refer to any other layer, so there is no need to signal inter_layer_ref_pics_present_flag, and the value is 0 by default. [Table 10] inter_layer_ref_pics_present_flag equal to 0 specifies that ILRP is not used for inter prediction of coded pictures in the CVS. inter_layer_ref_pics_flag equal to 1 specifies that ILRP may be used for inter prediction of one or more coded pictures in the CVS. If sps_video_parameter_set_id is 0 and inter_layer_ref_pics_flag is not present, the value of inter_layer_ref_pics_present_flag is inferred to be equal to 0. Another application example, coding both of the above cases, is shown below. [Table 11] inter_layer_ref_pics_present_flag equal to 0 specifies that ILRP is not used for inter prediction of coded pictures in the CVS. inter_layer_ref_pics_flag equal to 1 specifies that ILRP may be used for inter prediction of one or more coded pictures in the CVS. If sps_video_parameter_set_id is 0 and inter_layer_ref_pics_flag is not present, the value of inter_layer_ref_pics_present_flag is inferred to be equal to 0.

[0182] Fourth embodiment of the present invention [RPL] Note that if GeneralLayerIdx[nuh_layer_id] is equal to 1, the current layer is layer 1 and can only refer to layer 0, while ilrp_idc for layer 0 must be 0. Therefore, in this case, there is no need to signal irp_idc. [Table 12] irp_idc[listIdx][rplsIdx][i] specifies the index of the ILRP of the i-th entry in the ref_pic_list_struct(listIdx,rplsIdx) syntax structure for the list of direct dependency layers. The value of lrp_idc[listIdx][rplsIdx][i] shall be in the range from 0 to GeneralLayerIdx[nuh_layer_id]-1, inclusive. If GeneralLayerIdx[nuh_layer_id] is equal to 1, the value of lrp_idc[listIdx][rplsIdx][i] is inferred to be equal to 0.

[0183] Fifth embodiment of the present invention [combination] It should be noted that some or all of the embodiments from embodiment 1 to embodiment 4 can be combined to form new embodiments. For example, embodiment 1+embodiment 2+embodiment 3+embodiment 4, or embodiment 2+embodiment 3+embodiment 4, or other combinations.

[0184] The following is a description of the applications of the encoding and decoding methods and systems using them as shown in the above embodiments.

[0185] 7 is a block diagram showing a content delivery system 3100 for implementing a content distribution service. The content delivery system 3100 includes a capture device 3102, a terminal device 3106, and optionally a display 3126. The capture device 3102 communicates with the terminal device 3106 via a communication link 3104. The communication link may include the communication channel 13 described above. The communication link 3104 may include, but is not limited to, WIFI, Ethernet, cable, wireless (3G / 4G / 5G), USB, or any combination thereof.

[0186] The capture device 3102 may generate data and encode the data by an encoding method as shown in the above embodiment. Alternatively, the capture device 3102 may distribute the data to a streaming server (not shown), which then encodes the data and transmits the encoded data to the terminal device 3106. The capture device 3102 may include, but is not limited to, a camera, a smartphone or pad, a computer or laptop, a video conferencing system, a PDA, an in-vehicle device, or any combination thereof. For example, the capture device 3102 may include the source device 12 as described above. If the data includes video, the video encoder 20 included in the capture device 3102 may actually perform the video encoding process. If the data includes audio (i.e., voice), the audio encoder included in the capture device 3102 may actually perform the audio encoding process. For some practical scenarios, the capture device 3102 distributes the encoded video and audio data by multiplexing them together. In other practical scenarios, for example, in a video conferencing system, the encoded audio data and the encoded video data are not multiplexed, and the capture device 3102 distributes the encoded audio data and the encoded video data to the terminal device 3106 separately.

[0187] In the content delivery system 3100, the terminal device 3106 receives and reproduces the encoded data. The terminal device 3106 may be a device having data receiving and recovering capabilities, or capable of decoding the encoded data, such as a smartphone or pad 3108, a computer or laptop 3110, a network video recorder (NVR) / digital video recorder (DVR) 3112, a TV 3114, a set-top box (STB) 3116, a video conferencing system 3118, a video surveillance system 3120, a personal digital assistant (PDA) 3122, an in-vehicle device 3124, or any combination thereof. For example, the terminal device 3106 may include the destination device 14 described above. If the encoded data includes video, the video decoder 30 included in the terminal device is prioritized to perform video decoding. If the encoded data includes audio, the audio decoder included in the terminal device is prioritized to perform audio decoding.

[0188] For terminal devices with their own display, such as a smartphone or pad 3108, a computer or laptop 3110, a network video recorder (NVR) / digital video recorder (DVR) 3112, a TV 3114, a personal digital assistant (PDA) 3122, or an in-vehicle device 3124, the terminal device can feed the decoded data to its display. For terminal devices without a display, such as an STB 3116, a video conferencing system 3118, or a video surveillance system 3120, an external display 3126 is connected thereto to receive and display the decoded data.

[0189] If each device in the system performs encoding or decoding, a video encoding device or a video decoding device may be used as shown in the above embodiments.

[0190] 8 is a diagram illustrating a configuration according to one example of the terminal device 3106. After the terminal device 3106 receives the stream from the capture device 3102, the protocol processing unit 3202 analyzes the transmission protocol of the stream, which includes, but is not limited to, Real Time Streaming Protocol (RTSP), HyperText Transfer Protocol (HTTP), HTTP Live Streaming Protocol (HLS), MPEG-DASH, Real Time Transport Protocol (RTP), Real Time Message Protocol (RTMP), or any combination thereof.

[0191] After the protocol processing unit 3202 processes the stream, a stream file is generated. The file is output to a demultiplexing unit 3204. The demultiplexing unit 3204 can separate the multiplexed data into encoded audio data and encoded video data. For some practical scenarios mentioned above, for example, in a video conferencing system, the encoded audio data and encoded video data are not multiplexed. In this situation, the encoded data is sent to the video decoder 3206 and the audio decoder 3208 without going through the demultiplexing unit 3204.

[0192] Through the demultiplexing process, a video elementary stream (ES), an audio ES, and optionally subtitles are generated. The video decoder 3206, which includes the video decoder 30 as described in the above embodiment, decodes the video ES by the decoding method as shown in the above embodiment to generate video frames and feeds this data to the synchronization unit 3212. The audio decoder 3208 decodes the audio ES to generate audio frames and feeds this data to the synchronization unit 3212. Alternatively, the video frames may be stored in a buffer (not shown in Figure Y) before being supplied to the synchronization unit 3212. Similarly, the audio frames may be stored in a buffer (not shown in Figure Y) before being supplied to the synchronization unit 3212.

[0193] The synchronization unit 3212 synchronizes the video and audio frames and provides the video / audio to the video / audio display 3214. For example, the synchronization unit 3212 synchronizes the presentation of video and audio information. The information can be coded in the syntax using timestamps for the representation of the coded audio and visual data and for the delivery of the data stream itself.

[0194] If subtitles are included in the stream, the subtitle decoder 3210 decodes the subtitles and synchronizes them with the video and audio frames, and provides the video / audio / subtitles to the video / audio / subtitle display 3216.

[0195] The present invention is not limited to the above-mentioned system, and either the video encoding device or the video decoding device in the above-mentioned embodiments may be incorporated into other systems, for example, vehicle systems.

[0196] Mathematical Operators The mathematical operators used in this application are similar to those used in the C programming language. However, the results of integer division and arithmetic shift operations are more precisely defined, and additional operations such as exponentiation and real-valued division are defined. Numbering and counting conventions generally start from 0; for example, "the first" is equivalent to 0-th, "the second" is equivalent to second, etc.

[0197] Arithmetic operators The following arithmetic operators are defined as follows: + Addition. - Subtraction (as a two-argument operator) or negation (as a unary prefix operator). * Multiplication, including matrix multiplication. x y Exponent. Specifies x to the power y. In other contexts, such notation is used as a superscript without any intended interpretation as an exponential function. / Integer division with the result truncated towards zero. For example, 7 / 4 and -7 / -4 round down to 1, and -7 / 4 and 7 / -4 round down to -1. ÷ Used to indicate division in mathematical expressions, where no truncation or rounding is intended.

number

number

[0198] Logical operators The following logical operators are defined as follows: x&&y Boolean logic "and" on x and y. x||y Boolean logic "or" on x and y. ! Boolean logic "not". x?y:zIf x is TRUE or not 0, evaluates with the value of y. Otherwise, evaluates with the value of z.

[0199] Relational operators The following relational operators are defined as follows: > Greater than. >= Greater than or equal to. < Less than. <= Less than or equal to. = Equal to. != Not equal to.

[0200] When a relational operator is applied to a syntax element or variable that has been assigned the value "na" (not applicable), the value "na" is treated as a distinct value of the syntax element or variable. The value "na" is considered unequal to any other value.

[0201] Bit-wise operators The following bitwise operators are defined as follows: & Bitwise "and". When operating on integer arguments, operates on the two's complement representation of the integer value. When operating on a binary argument that contains fewer bits than another argument, the shorter argument is extended by adding its more significant bits equal to 0. | Bitwise "or". When operating on integer arguments, it operates on the two's complement representation of the integer value. When operating on binary arguments that contain fewer bits than another argument, the shorter argument is extended by adding leading bits equal to 0. ^ Bitwise "exclusive or". When operating on integer arguments, it operates on the two's complement representation of the integer value. When operating on binary arguments that contain fewer bits than another argument, the shorter argument is extended by adding leading bits equal to 0. x>>y Arithmetically right-shift the two's complement integer representation of x by the number of bits in the binary representation of y. This function is defined only for non-negative integer values of y. The bits shifted into the most significant bit (MSB) as a result of the right shift have the same value as the MSB of x prior to the shift operation. x<<y Arithmetically left-shift the two's complement integer representation of x by the number of bits in the binary representation of y. This function is defined only for non-negative integer values of y. The bits shifted into the least significant bit (LSB) as a result of the left shift have a value equal to 0.

[0202] Assignment operator The following arithmetic operators are defined as follows. = Assignment operator. ++ Increment, i.e., x++ is equivalent to x=x+1. When used in an array index, it is evaluated with the value of the variable prior to the increment operation. ―― Decrement, i.e., x-- is equivalent to x=x-1, and when used in an array index, it is evaluated with the value of the variable prior to the decrement operation. += Increment by the specified amount, i.e., x+=3 is equivalent to x=x+3, and x+=(-3) is equivalent to x=x+(-3). -= Decrement by the specified amount, i.e., x-=3 is equivalent to x=x-3, and x-=(-3) is equivalent to x=x-(-3).

[0203] Range notation The following notation is used to specify a range of values: x=y..zx takes integer values ​​from y to z inclusive, where x, y, and z are integers and z is greater.

[0204] mathematical functions The following mathematical functions are defined:

number

number

number

number

number

number

number

[0205] Order of operation precedence If the precedence in an expression is not explicitly stated using parentheses, the following rules apply: - Operations with higher precedence are evaluated before operations with lower precedence. - Operations of equal precedence are evaluated consecutively from left to right. The table below shows the precedence of operations from highest to lowest, with higher positions in the table indicating higher precedence. Also in the C programming language, for operators used, the precedence used in this specification is the same as the precedence used in the C programming language. [Table 13] Table: Operation precedence from highest (top of table) to lowest (bottom of table)

[0206] Text description of logical operations In the text, logical statements are written mathematically in the following form:

number

[0207] Text description of logical operations In the text, logical statements are written mathematically in the following form:

number

[0208] In the text, logical statements are written mathematically in the following form: if(condition 0) statement 0 if(condition 1) statement 1 The above can be written in the following way. When condition 0, statement 0 When condition 1, statement 1

[0209] Although embodiments of the present invention have been described primarily in the context of video coding, it should be noted that embodiments of coding system 10, encoder 20, and decoder 30 (and corresponding system 10), as well as other embodiments described herein, may also be configured for still image processing or coding, i.e., processing or coding of individual pictures independent of any preceding or subsequent pictures, as in video coding. Generally, when video processing coding is limited to a single picture 17, only inter prediction units 244 (encoder) and 344 (decoder) may not be available. All other functionality (also referred to as tools or technologies) of the video encoder 20 and the video decoder 30 may be equally used for still image processing, such as residual calculation 204 / 304, transform 206, quantization 208, inverse quantization 210 / 310, (inverse) transform 212 / 312, partitioning 262 / 362, intra prediction 254 / 354, and / or loop filtering 220, 320, and entropy coding 270 and entropy decoding 304.

[0210] For example, embodiments of the encoder 20 and decoder 30, and functions described herein in connection with the encoder 20 and decoder 30, may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions may be stored on a computer-readable medium or transmitted over a communication medium as one or more instructions or code and executed by a hardware-based processing unit. Computer-readable media may include computer-readable storage media, which correspond to tangible media such as data storage media, or communication media, including any medium that facilitates transfer of a computer program from one place to another, for example, according to a communication protocol. In this manner, computer-readable media may generally correspond to (1) tangible computer-readable storage media that are non-transitory, or (2) communication media, such as a signal or carrier wave. Data storage media may be any available medium that can be accessed by one or more computers or one or more processors to retrieve instructions, code, and / or data structures for implementing the techniques described in this disclosure. A computer program product may include computer-readable media.

[0211] In particular, as shown in Figure 9, there is provided a method for decoding a coded video bitstream implemented in a decoder. The method includes: S901, obtaining from the coded video bitstream a first syntax element (i.e., vps_independent_layer_flag[i]) specifying whether a first layer uses inter-layer prediction; and S902, obtaining from the coded video bitstream one or more second syntax elements (i.e., vps_direct_direct_depency_flag[i][j]) related to one or more second layers, each second syntax element specifying whether the second layer is a direct reference layer of the first layer, where at least one second syntax element of the one or more second syntax elements has a value specifying that the second layer is a direct reference layer of the first layer if the value of the first syntax element specifies that the first layer is allowed to use inter-layer prediction. and S903, performing inter-layer prediction on a picture of the first layer by using a picture of the second layer associated with the at least one second syntax element as a reference picture.

[0212] Similarly, as shown in Figure 10, there is provided a method for encoding a video bitstream including coded data implemented in an encoder. The method includes: S1001, determining whether at least one second layer is a direct reference layer of the first layer; and S1003, encoding a syntax element into the coded video bitstream, where the syntax element specifies whether the first layer uses inter-layer prediction, and where if any of the at least one second layer is not a direct reference layer of the first layer, a value of the syntax element specifies that the first layer does not use inter-layer prediction.

[0213] 11 illustrates a decoder 1100 configured to decode a video bitstream including coded data for multiple pictures. The decoder 1100 according to the illustrated example includes an acquisition unit 1110 and a prediction unit 1120. The acquisition unit 1110 is configured to acquire, from the coded video bitstream, a first syntax element specifying whether a first layer uses inter-layer prediction. The acquisition unit 1110 is further configured to acquire one or more second syntax elements associated with one or more second layers, each second syntax element specifying whether the second layer is a direct reference layer of the first layer. Here, if the value of the first syntax element specifies that the first layer is allowed to use inter-layer prediction, at least one second syntax element of the one or more second syntax elements has a value specifying that the second layer is a direct reference layer of the first layer. The prediction unit 1120 is then configured to perform inter-layer prediction on the picture of the first layer by using the picture of the second layer associated with the at least one second syntax element as a reference picture.

[0214] Here, a unit may be a software module for execution by a processor or a processing circuit.

[0215] Here, the acquisition unit 1110 may be the entropy decoding unit 304. The prediction unit 1120 may be the inter prediction unit 344. The decoder 1100 may be the destination device 14, the decoder 30, the device 500, the video decoder 3206, or the terminal device 3106.

[0216] Similarly, as shown in FIG. 12, an encoder 1200 configured to encode a video bitstream including coded data for a plurality of pictures is provided. The encoder 1200 includes a determining unit 1210 and an encoding unit 1220. The determining unit 1210 is configured to determine whether at least one second layer is a direct reference layer of the first layer. The encoding unit 1220 is configured to encode a syntax element into the coded video bitstream, where the syntax element specifies whether the first layer uses inter-layer prediction. Wherein, if any of the at least one second layer is not a direct reference layer of the first layer, a value of the syntax element specifies that the first layer does not use inter-layer prediction.

[0217] Here, a unit may be a software module for execution by a processor or a processing circuit.

[0218] The first coding unit 1210 and the second coding unit 1220 may be entropy coding units 270. The decision unit may be the mode selection unit 260. The encoder 1200 may be the source device 12, the encoder 20, or the apparatus 500.

[0219] By way of example, and not limitation, such computer-readable storage media may include RAM, ROM, EEPROM, CD-ROM or other optical disk storage devices, magnetic disk storage devices or other magnetic storage devices, flash memory, or any other medium that can be used to store desired program code in the form of instructions or data structures and that can be accessed by a computer. Also, any connection is properly termed a computer-readable medium. For example, if instructions are transmitted from a website, server, or other remote source using coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared, radio, and microwave, the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are included within the definition of medium. However, it should be understood that computer-readable storage media and data storage media do not include connections, carrier waves, signals, or other transitory media, but instead refer to non-transitory, tangible storage media. Disk and disc, as used herein, include compact discs (CDs), laser discs, optical discs, digital versatile discs (DVDs), floppy disks, and Blu-ray discs, where disks often reproduce data magnetically, while disks reproduce data optically using a laser. Combinations of the above should also be included within the scope of computer-readable media.

[0220] The instructions may be executed by one or more processors, such as one or more digital signal processors (DSPs), general-purpose microprocessors, application-specific integrated circuits (ASICs), field-programmable logic arrays (FPGAs), or other equivalent integrated or discrete logic circuitry. Accordingly, as used herein, the term "processor" may refer to any of the foregoing structures, or any other structure suitable for implementing the techniques described herein. Additionally, in some aspects, the functionality described herein may be provided in dedicated hardware and / or software modules configured for encoding and decoding, or may be incorporated into a combined codec. The techniques may also be implemented entirely in one or more circuits or logic elements.

[0221] The techniques of this disclosure may be implemented in a wide variety of devices or apparatuses, including a wireless handset, an integrated circuit (IC), or a set of ICs (e.g., a chipset). Various components, modules, or units are described in this disclosure to highlight functional aspects of devices configured to implement the disclosed techniques, but do not necessarily require realization by different hardware units. Rather, as described above, the various units may be combined within a codec hardware unit or may be provided by a collection of interoperable hardware units, including one or more processors as described above, in conjunction with appropriate software and / or firmware.

Claims

1. 1. A method for decoding a coded video bitstream, comprising: obtaining, from the coded video bitstream, a first syntax element having an index i, the first syntax element specifying whether a first layer having the index i uses inter-layer prediction; obtaining, from the coded video bitstream, one or more second syntax elements associated with one or more second layers, wherein each second syntax element having an index i and an index j specifies whether the second layer having the index j is a direct reference layer for the first layer having the index i, and j is in the range from 0 to i−1, and at least one second syntax element among the second syntax elements having the index j is equal to 1 when a value of the first syntax element is equal to 0; and obtaining, from the coded video bitstream, a third syntax element, wherein the third syntax element equal to 0 specifies that an inter-layer reference picture (ILRP) is not used for inter-prediction of any coded picture, the third syntax element equal to 1 specifies that ILRP may be used for inter prediction of one or more coded pictures.

2. The method of claim 1 , wherein the first syntax element equal to 1 specifies that the first layer does not use inter-layer prediction.

3. 3. The method of claim 1, wherein the second syntax element equal to 0 specifies that the second layer associated with the second syntax element is not a direct reference layer of the first layer, or the second syntax element equal to 1 specifies that the second layer associated with the second syntax element is a direct reference layer of the first layer.

4. 4. The method of claim 1, wherein the step of obtaining one or more second syntax elements is performed if a value of the first syntax element specifies that the first layer is allowed to use inter-layer prediction.

5. The method of claim 1 , wherein the first syntax element is denoted as vps_independent_layer_flag[i].

6. The method of claim 1 , wherein an ILRP is a picture in the same access unit (AU) as a current picture, and wherein nuh_layer_id is smaller than the nuh_layer_id of the current picture.

7. The method of claim 1 , wherein the third syntax element is included in a sequence parameter set (SPS) of the coded video bitstream.

8. 1. A method for encoding a coded video bitstream, the method comprising: encoding into the coded video bitstream a first syntax element, the first syntax element having an index i and specifying whether a first layer having the index i uses inter-layer prediction; encoding into the coded video bitstream one or more second syntax elements associated with at least one second layer, wherein each second syntax element having an index i and an index j specifies whether a second layer having the index j is a direct reference layer for the first layer having the index i, and when a value of the first syntax element is equal to 0, j is in the range from 0 to i−1, and at least one second syntax element among the second syntax elements having the index j is equal to 1; and encoding into the coded video bitstream a third syntax element, wherein the third syntax element equal to 0 specifies that an inter-layer reference picture (ILRP) is not used for inter-prediction of any coded picture, the third syntax element equal to 1 specifies that ILRP may be used for inter prediction of one or more coded pictures.

9. The method of claim 8 , wherein the first syntax element equal to 1 specifies that the first layer does not use inter-layer prediction.

10. 10. The method of claim 8 or 9, wherein a second syntax element equal to 0 specifies that the second layer associated with the second syntax element is not a direct reference layer of the first layer, or a second syntax element equal to 1 specifies that the second layer associated with the second syntax element is a direct reference layer of the first layer.

11. 11. The method of claim 8, wherein the step of encoding one or more second syntax elements associated with at least one second layer into the coded video bitstream is performed if a value of the first syntax element indicates that the first layer is allowed to use inter-layer prediction.

12. 12. The method of claim 8, wherein the ILRP is a picture in the same access unit (AU) as the current picture, and the nuh_layer_id is smaller than the nuh_layer_id of the current picture.

13. The method of claim 8 , wherein the third syntax element is included in a sequence parameter set (SPS) of the coded video bitstream.

14. An encoder comprising processing circuitry for carrying out the method of any one of claims 8 to 13.

15. A decoder comprising processing circuitry for carrying out the method of any one of claims 1 to 7.

16. A computer program comprising program code, which, when executed by a processor of a computer, causes the computer to perform a method according to any one of claims 1 to 7 or a method according to any one of claims 8 to 13.

17. 8. A decoder comprising: one or more processors; and a non-transitory computer-readable storage medium coupled to the processors and storing a program executed by the processors, the program being configured, when executed by the processors, to cause the decoder to perform the method of any one of claims 1 to 7.

18. 14. An encoder comprising: one or more processors; and a non-transitory computer-readable storage medium coupled to the processors and storing a program executed by the processors, the program being configured, when executed by the processors, to cause the encoder to perform the method of any one of claims 8 to 13.

19. A non-transitory computer readable storage medium carrying program code which, when executed by a computing device, causes the computing device to perform the method of any one of claims 1 to 7, or causes the computing device to perform the method of any one of claims 8 to 13.

20. 1. An apparatus for storing and transmitting a bitstream, the apparatus comprising: a receiver, a processor, a transmitter, and a storage medium, wherein the receiver is configured to receive a bitstream, the storage medium is configured to store the bitstream, and the transmitter is configured to transmit the bitstream, the bitstream comprising: a first syntax element, one or more second syntax elements, and a third syntax element, wherein the first syntax element has an index i and specifies whether a first layer having the index i uses inter-layer prediction; each second syntax element having an index i and an index j specifies whether a second layer having the index j is a direct reference layer for the first layer having the index i; the third syntax element equal to 0 specifies that an inter-layer reference picture (ILRP) is not used for inter-prediction of any coded picture; and the third syntax element equal to 1 specifies that ILRP may be used for inter-prediction of one or more coded pictures. When the value of the first syntax element is equal to 0, j is in the range from 0 to i-1, and at least one second syntax element among the second syntax elements having the index j is equal to 1, and a first syntax element equal to 0 specifies that the first layer is allowed to use inter-layer prediction, and the processor parses the bitstream to obtain the first syntax element, the one or more second syntax elements, and the third syntax element.

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