Encoder, decoder and corresponding method for merge mode

Abstract

To provide methods and devices for processing a block according to a merge candidate list.SOLUTION: A method includes the steps of: constructing a first list according to motion information of neighboring blocks of a current block; obtaining prediction information of the current block; when the prediction information of the current block indicates that a sub-block prediction is applied to the current block, obtaining a uni-prediction candidate for the current block according to the first list; and using the uni-prediction candidate for the current block to perform inter prediction of the current block. According to an embodiment of the present disclosure, the regular merge list can be directly used and there is no need to explicitly generate the uni-prediction merge candidate list for sub-block prediction.SELECTED DRAWING: None

Description

[Technical Field]

[0001] FIELD Embodiments of the present disclosure relate generally to the field of picture processing, and more particularly to merge modes. [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 acquisition and editing systems, and camcorders in security applications.

[0003] The amount of video data required to render even a relatively short video can be significant, which can pose challenges when the data is to be streamed or otherwise transmitted over communication networks with limited bandwidth capacity. Therefore, video data is generally compressed before being transmitted over modern communication networks. Because memory resources may be limited, video size can also be an issue when the video is stored on a storage device. Often, video compression devices use software and / or hardware at the source to code the video data before transmission or storage, thereby reducing the amount of data needed to represent a digital video image. The compressed data is then received at the destination by a video decompression device, which decodes the video data. With limited network resources and an ever-increasing demand for higher video quality, improved compression and decompression techniques that increase compression ratios with little or no sacrifice in picture quality are desirable. Summary of the Invention [Means for solving the problem]

[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 implementation forms are evident from the dependent claims, the description and the drawings.

[0006] According to a first aspect of the present disclosure, a method for processing blocks according to a merge candidate list is disclosed, the method comprising: The method includes constructing a first list according to motion information of neighboring blocks of the current block; obtaining prediction information of the current block; when the prediction information of the current block indicates that lower-order block prediction is applied to the current block, obtaining uni-prediction candidates for the current block according to the first list; and using the uni-prediction candidates for the current block to perform inter-prediction of the current block.

[0007] In this method, the regular merge candidate list is reused for merge prediction of sub-block partitions (eg, triangular or non-rectangular) without extra motion vector pruning.

[0008] In a possible implementation, the current block includes two sub-blocks, each of which corresponds to a uni-predictive candidate.

[0009] In a possible implementation form, one uni-prediction candidate is generated according to one bi-prediction candidate in the first list.

[0010] In a possible implementation, two uni-predictive candidates are generated according to one bi-predictive candidate in the first list.

[0011] In a possible implementation form, one uni-predictive candidate is the first part of the bi-predictive candidates.

[0012] In a possible implementation, one uni-predictive candidate is the second part of the bi-predictive candidates.

[0013] In a possible implementation, the lower-level block prediction is a triangular prediction.

[0014] In a possible implementation form, generating two uni-predictive candidates according to one bi-predictive candidate of the first list comprises: This involves determining the similarity between two unipredictive candidates.

[0015] In a possible implementation, uni-predictive candidates are generated according to the bi-predictive candidates in the first list based on the order of the candidates in the first list.

[0016] According to a second aspect of the present disclosure, an encoder includes processing circuitry for performing a method embodiment.

[0017] According to a third aspect of the present disclosure, a decoder includes processing circuitry for performing a method embodiment.

[0018] According to a fourth aspect of the present disclosure, a computer program product includes program code for carrying out an embodiment of a method.

[0019] According to a fifth aspect of the present disclosure, a decoder includes: one or more processors; a non-transitory computer-readable storage medium coupled to the processor and storing programming for execution by the processor, the programming, when executed by the processor, configuring the decoder to perform an embodiment of the method; and Includes.

[0020] According to a sixth aspect of the present disclosure, an encoder includes: one or more processors; a non-transitory computer-readable storage medium coupled to the processor and storing programming for execution by the processor, the programming, when executed by the processor, configuring the encoder to perform an embodiment of the method; and Includes.

[0021] According to an embodiment of the present disclosure, in order to maximize the common operations shared by different merge modes, a normal merge list is constructed, and its motion vectors are used for lower-level block prediction. In an example, for each merge candidate in the normal merge candidate list, one and only one of its L0 or L1 motion vectors is used for one lower-level block prediction. Furthermore, the order of selecting L0 vs. L1 motion vectors is based on the parity of their merge indexes. The normal merge list can be used directly, and there is no need to explicitly generate a uni-predictive merge candidate list for lower-level block prediction.

[0022] In the example, when a normal merge list is constructed, for each merge candidate in the normal merge candidate list, one and only one of the L0 or L1 motion vectors is used for one lower block prediction. Furthermore, the order of selecting L0 versus L1 motion vectors is based on the parity of the merge index. In the example, as shown in Table 1, for a candidate with an even-valued index, the L0 motion vector is first selected to be used for lower block prediction. If the L0 motion vector is unavailable, the L1 motion vector is used instead of the L0 motion vector. For a candidate with an odd-valued index, the L1 motion vector is first selected to be used for triangular prediction. If it is unavailable, the L0 motion vector is used instead. In Table 1, the motion vector marked with an "x" corresponding to each merge index is first selected for lower block prediction.

[0023] [Table 1]

[0024] According to embodiments of the present disclosure, a normal merge list can be used directly, and there is no need to explicitly generate a uni-predictive merge candidate list for lower-order block prediction. At the decoder side, once the merge index of the lower-order block is received, the uni-predictive MV candidates can be easily found based on the signaled merge index value.

[0025] The details of one or more embodiments are set forth in the accompanying drawings and the description below. Other features, objects, and advantages will become apparent from the description, drawings, and claims.

[0026] In the following, embodiments of the present disclosure will be described in more detail with reference to the accompanying figures and drawings. [Brief explanation of the drawings]

[0027] [Figure 1A] FIG. 1 is a block diagram illustrating an example of a video coding system configured to implement embodiments of the present disclosure. [Figure 1B] FIG. 2 is a block diagram illustrating another example of a video coding system configured to implement embodiments of the present disclosure. [Figure 2] FIG. 1 is a block diagram illustrating an example of a video encoder configured to implement embodiments of the present disclosure. [Figure 3] 1 is a block diagram illustrating an example structure of a video decoder configured to implement embodiments of the present disclosure. [Figure 4] FIG. 1 is a block diagram illustrating an example of an encoding device or a decoding device. [Figure 5] FIG. 10 is a block diagram showing another example of an encoding device or a decoding device. [Figure 6] 10 is a flow diagram illustrating an example of building a second motion candidate list based on a first motion candidate list. [Figure 7a] FIG. 10 illustrates an example of co-located blocks. [Figure 7b] FIG. 1 illustrates an example of spatially neighboring blocks. [Figure 8] 10 is a flow diagram illustrating another example of constructing a second motion candidate list based on a first motion candidate list. [Figure 9] FIG. 10 is a diagram illustrating an example of a triangular prediction mode. [Figure 10] 10 is a flow diagram illustrating another example of constructing a second motion candidate list based on a first motion candidate list. [Figure 11] FIG. 10 is a diagram illustrating some examples of lower-order block prediction modes. [Figure 12] 10A and 10B are diagrams illustrating examples of merge candidates selected from candidates in positions. [Figure 13] FIG. 10 is a diagram illustrating an example of a merge candidate. [Figure 14] FIG. 10 illustrates an example of obtaining a scaled motion vector. [Figure 15] FIG. 10 illustrates an example for temporal candidates. [Figure 16] 31 is a block diagram illustrating an exemplary structure of a content supply system 3100 for implementing a content distribution service. [Figure 17] FIG. 2 is a block diagram illustrating the structure of an example terminal device. DETAILED DESCRIPTION OF THE INVENTION

[0028] In the following, the same reference signs, unless otherwise specified, refer to identical or at least functionally equivalent features.

[0029] In the following description, reference is made to the accompanying drawings which form a part of this disclosure and which show, by way of illustration, specific aspects of embodiments of the present disclosure or in which embodiments of the present disclosure may be used. It is understood that embodiments of the present disclosure may be used in other ways and may include structural or logical changes not shown in the drawings. Therefore, the following detailed description is not to be taken in a limiting sense, and the scope of the present disclosure is defined by the appended claims.

[0030] For example, it will be understood that disclosure related to a described method may also apply to a corresponding device or system configured to perform the method, and vice versa. For example, when one or more particular method steps are described, the corresponding device may include one or more units, e.g., functional units, for performing the described one or more method steps (e.g., one unit that performs one or more steps, or multiple units that each perform one or more of the steps), even if such one or more units are not explicitly described or shown in a figure. On the other hand, for example, when a particular apparatus is described based on one or more units, e.g., functional units, the corresponding method may include one step for performing the function of the one or more units (e.g., one step that performs the function of one or more units, or multiple steps that each perform one or more functions of multiple units), even if such one or more steps are not explicitly described or shown in a figure. Furthermore, it will be understood that features of various exemplary embodiments and / or aspects described herein may be combined with each other unless expressly stated otherwise.

[0031] Video coding generally refers to the processing of a sequence of pictures 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 coding in general) includes two parts: video encoding and video decoding. Video encoding is performed at the source side and generally involves processing the original video picture (e.g., by compression) to reduce the amount of data needed to represent the video picture (for more efficient storage and / or transmission). Video decoding is performed at the destination side and generally involves the reverse process compared to the encoder to reconstruct the video picture. Embodiments that refer to "coding" a video picture (or pictures in general) are understood to relate to "encoding" or "decoding" the video picture or the respective video sequence. The combination of the encoding and decoding parts is also called a codec (coding and decoding).

[0032] In the case of lossless video coding, the original video picture can be reconstructed (assuming there is no transmission loss or other data loss during storage or transmission), i.e., the reconstructed video picture has the same quality as the original video picture. In the case of lossy video coding, further compression, for example by quantization, is performed to reduce the amount of data representing the video picture, which cannot be perfectly reconstructed at the decoder, i.e., the quality of the reconstructed video picture is lower or worse than the quality of the original video picture.

[0033] Some video coding standards belong to the group of "lossy hybrid video codecs" (i.e., combine spatial and temporal prediction in the sample domain with 2D transform coding for applying quantization in the transform domain). Each picture of a video sequence is generally partitioned into a set of non-overlapping blocks, and coding is generally performed at the block level. In other words, at an encoder, video is generally processed, i.e., encoded, at the block (video block) level, for example, by generating a prediction block using spatial (intra-picture) prediction and / or temporal (inter-picture) prediction, subtracting the prediction block from a current block (the block currently being / to be processed) to obtain a residual block, transforming the residual block, and quantizing the residual block in the transform domain to reduce the amount of data to be transmitted (compression); whereas at a decoder, an inverse process is applied to the coded or compressed block compared to the encoder to reconstruct the current block for representation. Furthermore, the encoder replicates the decoder's processing loop so that both generate the same prediction (eg, intra and inter prediction) and / or reconstruction for processing, i.e., coding, subsequent blocks.

[0034] In the following, embodiments of a video coding system 10, a video encoder 20 and a video decoder 30 are described based on FIGS.

[0035] 1A is a schematic block diagram illustrating an example coding system 10, e.g., video coding system 10 (or coding system 10 for short), that may utilize techniques of the present application. A video encoder 20 (or encoder 20 for short) and a video decoder 30 (or decoder 30 for short) of video coding system 10 illustrate examples of devices that may be configured to perform techniques according to various examples described in the present application.

[0036] As shown in FIG. 1A, coding system 10 includes a source device 12 configured to provide encoded picture data 21 to, for example, a destination device 14 for decoding the encoded picture data 13.

[0037] The 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 picture preprocessor 18, and a communication interface or unit 22.

[0038] Picture source 16 may include or be any kind of picture capture device, e.g., a camera for capturing real-world pictures, and / or any kind of picture generation device, e.g., a computer graphics processor for generating computer-animated pictures, or any kind of other device for acquiring and / or providing real-world pictures, computer-generated pictures (e.g., screen content, virtual reality (VR) pictures), and / or any combination thereof (e.g., augmented reality (AR) pictures). Picture source may also be any kind of memory or storage for storing any of the above-mentioned pictures.

[0039] To distinguish from the preprocessor 18 and the processing performed by the preprocessing unit 18, the picture or picture data 17 may also be referred to as a raw picture or raw picture data 17.

[0040] The pre-processor 18 is configured to receive (raw) picture data 17 and perform pre-processing on the picture data 17 to obtain a pre-processed picture 19 or pre-processed picture data 19. The pre-processing performed by the pre-processor 18 may include, for example, cropping, color format change (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.

[0041] Video encoder 20 is configured to receive pre-processed picture data 19 and provide encoded picture data 21 (further details are described below, eg, with reference to FIG. 2).

[0042] The communication interface 22 of the source device 12 may be configured to receive the encoded picture data 21 and transmit the encoded picture data 21 (or any further processed version thereof) via the communication channel 13 to another device, e.g., the destination device 14 or any other device, for storage or direct reconstruction.

[0043] The destination device 14 includes a decoder 30 (e.g., a video decoder 30) and may additionally, i.e., optionally, include a communication interface or communication unit 28, a post-processor 32 (or post-processing unit 32), and a display device 34.

[0044] The communications interface 28 of the destination device 14 is configured to receive the encoded picture 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 a storage device for encoded picture data, and to provide the encoded picture data 21 to the decoder 30.

[0045] The communication interface 22 and the communication interface 28 may be configured to transmit or receive the encoded picture data 21 or the encoded data 13 via a direct communication link between the source device 12 and the destination device 14, e.g., a direct wired or wireless connection, or via any type of network, e.g., a wired or wireless network or any combination thereof, or any type of private and public network, or any type of combination thereof.

[0046] The communications interface 22 may be configured to process the encoded picture data 21 using any type of transmission encoding or processing, for example packaging the encoded picture data 21 into a suitable format, for example packets, and / or for transmission over a communications link or network.

[0047] The communications interface 28 forming the counterpart of the communications interface 22 may for example be configured to receive the transmitted data and process the transmitted data using any kind of corresponding transmission decoding or processing and / or depackaging to obtain the encoded picture data 21.

[0048] Both communication interface 22 and communication interface 28 may be configured as unidirectional communication interfaces, as indicated by the arrows for communication channel 13 in FIG. 1A pointing from source device 12 toward destination device 14, or as bidirectional communication interfaces, and may be configured, for example, to send and receive messages, for example, to set up connections and to confirm and exchange communications links and / or any other information related to data transmission, e.g., transmission of encoded picture data.

[0049] The decoder 30 is configured to receive encoded picture data 21 and provide decoded picture data 31 or decoded pictures 31 (further details are described below, for example, based on Figure 3 or Figure 5).

[0050] Post-processor 32 of destination device 14 is configured to post-process decoded picture data 31 (also called reconstructed picture data), e.g., decoded picture 31, to obtain post-processed picture data 33, e.g., post-processed picture 33. The post-processing performed by post-processing unit 32 may include, e.g., color format change (e.g., from YCbCr to RGB), color correction, cropping, or resampling, or any other processing to prepare, e.g., decoded picture data 31, for display by, e.g., display device 34.

[0051] Display device 34 of destination device 14 is configured to receive post-processed picture data 33, for example, to display the picture to a user or viewer. Display device 34 may be or include any type of display for showing the reconstructed picture, e.g., an integrated or external display or monitor. The display may include, for example, a liquid crystal display (LCD), an organic light emitting diode (OLED) display, a plasma display, a projector, a microLED display, a liquid crystal on silicon (LCoS), a digital light processor (DLP), or any other type of display.

[0052] 1A depicts source device 12 and destination device 14 as separate devices, embodiments of the devices may also include both or both functionality, source device 12 or corresponding functionality and destination device 14 or corresponding functionality. In such embodiments, 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.

[0053] As will be apparent to those skilled in the art based on the description, the functions of different units or the presence and (exact) division of functions within source device 12 and / or destination device 14 shown in FIG. 1A may vary depending on the actual device and application.

[0054] Encoder 20 (e.g., video encoder 20) or decoder 30 (e.g., video decoder 30), or both encoder 20 and decoder 30, may be implemented by processing circuitry 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 to video coding, or any combination thereof. Encoder 20 may be implemented by processing circuitry 46 to embody various modules discussed in connection with encoder 20 of FIG. 2 and / or any other encoder system or subsystem described herein. Decoder 30 may be implemented by processing circuitry 46 to embody various modules discussed in connection with 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 discussed later. If the techniques are implemented partially in software, as shown in FIG. 5, 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 incorporated as part of a combined encoder / decoder (codec) within a single device, for example, as shown in FIG. 1B.

[0055] Source device 12 and destination device 14 may include any of a wide range of devices, including any type of handheld or fixed device, e.g., 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 may use no operating system or any type of operating system. In some cases, source device 12 and destination device 14 may be capable of wireless communication. Thus, source device 12 and destination device 14 may be wireless communication devices.

[0056] In some cases, the video coding system 10 shown in FIG. 1A is merely an example, and the techniques of this disclosure may be applied to video coding situations (e.g., video encoding or video decoding) that do not necessarily involve any 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 encoding 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.

[0057] For ease of explanation, embodiments of the present disclosure are described herein by reference to reference software, for example, High-Efficiency Video Coding (HEVC), or Versatile Video coding (VVC), the next-generation video coding standard developed by the ITU-T Video Coding Experts Group (VCEG) and the ISO / IEC Joint Collaboration Team on Video Coding (JCT-VC) of the Motion Picture Experts Group (MPEG). Those skilled in the art will understand that embodiments of the present disclosure are not limited to HEVC or VVC.

[0058] Encoder and encoding method 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 (DPB) 230, a mode selection unit 260, an entropy coding unit 270, and an output 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 may also be referred to as a hybrid video encoder or a video encoder using a hybrid video codec.

[0059] The residual calculation unit 204, the transform processing unit 206, the quantization unit 208, and the mode selection unit 260 may be considered to form 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 considered to form a backward signal path of the video encoder 20, which corresponds to the signal path of a decoder (see video decoder 30 in 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 are also considered to form a “built-in decoder” of the video encoder 20.

[0060] Picture & Picture Division (Picture & Block) Encoder 20 may be configured, for example, to receive via input 201 picture 17 (or picture data 17), e.g., a picture of a sequence of pictures forming a video or a video sequence. The received picture or picture data may also be preprocessed picture 19 (or preprocessed picture data 19). For simplicity, the following description refers to picture 17. Picture 17 may also be called a current picture or a picture to be coded (particularly in video coding, to distinguish the current picture from other pictures, e.g., already coded and / or decoded pictures of the same video sequence, i.e., the video sequence that also includes the current picture).

[0061] A (digital) picture is or can be considered as a two-dimensional array or matrix of samples having intensity values. The samples of the array may also be called pixels (short for 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 generally used, i.e., a picture may be represented or include three sample arrays. In an RBG format or color space, a picture includes corresponding red, green, and blue sample arrays. However, in video coding, each pixel is generally represented in a luminance and chrominance format or color space, e.g., YCbCr, which includes a luminance component denoted by Y (although L may be used instead) and two chrominance components denoted by Cb and Cr. The luminance (or luma for short) component Y represents brightness or gray level intensity (e.g., similar to a grayscale picture), while the two chrominance (or chroma for short) components Cb and Cr represent chromaticity or color information components. Thus, a picture in YCbCr format includes a luminance sample array of luminance sample values ​​(Y) and two chrominance sample arrays of chrominance values ​​(Cb and Cr). A picture in RGB format may be changed or converted to YCbCr format, and vice versa, a process also known as color conversion or transformation. If a picture is monochrome, the picture may include only a luminance sample array. Thus, a picture may be, for example, an array of luma samples in a 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.

[0062] Embodiments of video encoder 20 may include a picture partitioning unit (not shown in FIG. 2) configured to partition picture 17 into multiple (usually non-overlapping) picture blocks 203. These blocks may also be called root blocks, macroblocks (H.264 / AVC), or coding tree blocks (CTBs) or coding tree units (CTUs) (H.265 / HEVC and VVC). The picture partitioning unit may be configured to use the same block size for all pictures of a video sequence and a corresponding grid defining the block size, or to vary the block size among pictures or subsets or groups of pictures, and to partition each picture into corresponding blocks.

[0063] In further embodiments, the video encoder may be configured to directly receive blocks 203 of picture 17, e.g., one, some, or all of the blocks that form picture 17. Picture blocks 203 may also be referred to as current picture blocks or picture blocks to be coded.

[0064] Similar to picture 17, picture block 203, although smaller in dimensions than picture 17, is or can still be considered as a two-dimensional array or matrix of samples having intensity values ​​(sample values). In other words, block 203 may include, for example, one sample array (e.g., a luma array for a monochrome picture 17, or a luma or chroma array for a color picture), or three sample arrays (e.g., a luma and two chroma arrays for a color picture 17), or any other number and / or type of array, 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 MxN (M columns by N rows) array of samples or an MxN array of transform coefficients.

[0065] The embodiment of video encoder 20 shown in FIG. 2 may be configured to encode picture 17 block by block, eg, encoding and prediction is performed for each block 203.

[0066] Calculating residuals The residual calculation unit 204 may be configured to calculate the residual block 205 (also referred to as the residual 205) based on the picture block 203 and the predictive block 265 (further details about the predictive block 265 are provided later), for example, by subtracting the sample values ​​of the predictive block 265 from the sample values ​​of the picture block 203 on a sample-by-sample (pixel-by-pixel) basis to obtain the residual block 205 in the sample domain.

[0067] conversion The transform processing unit 206 may be configured to apply a transform, for example, a discrete cosine transform (DCT) or a discrete sine transform (DST), to the sample values ​​of the residual block 205 to obtain transform coefficients 207 in a transform domain. The transform coefficients 207, also referred to as transform residual coefficients, may represent the residual block 205 in the transform domain.

[0068] 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 generally scaled by a particular factor. To maintain the norm of the residual blocks processed by the forward and inverse transforms, an additional scaling factor is applied as part of the transform process. The scaling factor is generally selected based on particular constraints, such as the scaling factor being a power of two for shift operations, the bit depth of the transform coefficients, a trade-off between accuracy and implementation cost, etc. For example, a particular scaling factor may be specified for the inverse transform, e.g., by the inverse transform processing unit 212 (and the corresponding inverse transform, e.g., by the inverse transform processing unit 312 in the video decoder 30), and a corresponding scaling factor for the forward transform, e.g., by the transform processing unit 206 of the encoder 20, may be specified accordingly.

[0069] An embodiment of video encoder 20 (respectively, transform processing unit 206) may be configured to output transform parameters, e.g., a certain transform or transforms, either as is or encoded or compressed by entropy coding unit 270, for example, so that video decoder 30 may receive the transform parameters and use them for decoding.

[0070] 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 may also be referred to as quantized transform coefficients 209 or quantized residual coefficients 209.

[0071] 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 truncated 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, with respect to 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 include division by a quantization step size, and corresponding and / or inverse inverse quantization by, for example, the inverse quantization unit 210 may include multiplication by the quantization step size. Some standards, for example, HEVC, may be configured to determine the quantization step size using a quantization parameter. Generally, the quantization step size may be calculated based on the quantization parameter using a fixed-point approximation of an equation involving division. Additional scaling factors may be introduced for quantization and inverse quantization to restore the norm of the residual block, which may be modified due to scaling used in the fixed-point approximation of the equation for the quantization step size and the quantization parameter. In one exemplary implementation, the scaling of the inverse transform and inverse quantization may be combined. Alternatively, customized quantization tables may be used, e.g., signaled from the encoder to the decoder in the bitstream. Quantization is a lossy operation, and loss increases as the quantization step size increases.

[0072] Embodiments of video encoder 20 (respectively, quantization unit 208) may be configured to output a quantization parameter (QP), e.g., as is or to be encoded by entropy encoding unit 270, such that video decoder 30 may receive the quantization parameter and apply it for decoding.

[0073] inverse quantization Inverse quantization unit 210 is configured to apply the inverse quantization of quantization unit 208 to the quantized coefficients to obtain inverse quantized coefficients 211, e.g., by applying the inverse of the quantization scheme applied by quantization unit 208, based on or using the same quantization step size as quantization unit 208. The inverse quantized coefficients 211, also referred to as inverse quantized residual coefficients 211, may correspond to transform coefficients 207—although they are generally not identical to the transform coefficients due to loss due to quantization.

[0074] Inverse transformation The inverse transform processing unit 212 is configured to apply an inverse transform of the transform applied by the transform processing unit 206, for example, an inverse discrete cosine transform (DCT) or 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 may also be referred to as a transform block 213.

[0075] Rebuild The reconstruction unit 214 (e.g., an adder or summator 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 the sample values ​​of the reconstructed residual block 213 and the sample values ​​of the prediction block 265—sample by sample—to obtain a reconstructed block 215 in the sample domain.

[0076] filtering The loop filter unit 220 (or "loop filter" 220 for short) is configured to filter the reconstructed block 215 to obtain a filtered block 221, or generally, to filter reconstructed samples to obtain filtered samples. 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, for example, a bilateral filter, an adaptive loop filter (ALF), a sharpening filter, a smoothing filter, or a collaborative filter, or any combination thereof. Although the loop filter unit 220 is shown in FIG. 2 as being an in-loop filter, in other configurations, the loop filter unit 220 may be implemented as a post-loop filter. The filtered block 221 may also be referred to as a filtered reconstructed block 221.

[0077] Embodiments of video encoder 20 (respectively, loop filter unit 220) may be configured to output loop filter parameters (e.g., sample adaptive offset information) either as is or encoded by entropy coding unit 270, e.g., so that decoder 30 may receive and apply the same loop filter parameters or the respective loop filter for decoding.

[0078] Decoded Picture Buffer The decoded picture buffer (DPB) 230 may be a memory that stores reference pictures or generally reference picture data for encoding video data by the video encoder 20. The DPB 230 may be formed by any of a variety of memory devices, such as dynamic random access memory (DRAM), including synchronous DRAM (SDRAM), magnetoresistive RAM (MRAM), resistive RAM (RRAM), or other types of memory devices. The decoded picture buffer (DPB) 230 may be configured to store one or more filtered blocks 221. The decoded picture buffer 230 may further be configured to store other already-filtered blocks, e.g., already-reconstructed filtered blocks 221, of the same current picture or a different picture, e.g., an already-reconstructed picture, and / or may provide a complete already-reconstructed, i.e., decoded, picture (and corresponding reference blocks and samples) and / or a partially-reconstructed current picture (and corresponding reference blocks and samples), e.g., for inter-prediction. The decoded picture buffer (DPB) 230 may also be configured to store one or more unfiltered reconstructed blocks 215 or generally unfiltered reconstructed samples, for example, if the reconstructed blocks 215 are not filtered by the loop filter unit 220, or to store any other further processed version of the reconstructed blocks or samples.

[0079] Mode selection (classification & prediction) The mode selection 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 picture data, e.g., original block 203 (current block 203 of current picture 17), and reconstructed picture data, e.g., filtered and / or unfiltered reconstructed samples or blocks of the same (current) picture and / or from one or more already decoded pictures, for example, from the decoded picture buffer 230 or other buffer (e.g., a line buffer, not shown). The reconstructed picture data is used as reference picture data for prediction, e.g., inter prediction or intra prediction, to obtain a prediction block 265 or predictor 265.

[0080] The mode selection unit 260 may be configured to determine or select a partitioning and prediction mode (e.g., intra or inter prediction mode) for the prediction mode of the current block (which does not include partitioning) and generate a corresponding prediction block 265 used for calculating the residual block 205 and reconstructing the reconstructed block 215.

[0081] Embodiments of the mode selection unit 260 may be configured to select a partitioning and prediction mode (e.g., from partitioning and prediction modes supported by or available to the mode selection unit 260) that provides the best match, or 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. The mode selection unit 260 may be configured to determine the partitioning and prediction mode based on rate-distortion optimization (RDO), i.e., to select the prediction mode that provides the smallest rate-distortion. Terms such as “best,” “minimum,” “optimum,” etc. in this context do not necessarily refer to the overall “best,” “minimum,” “optimum,” etc., but may also refer to satisfying termination or selection criteria such as values ​​above or below a threshold, or other constraints that potentially lead to a “suboptimal selection,” but that reduce complexity and processing time.

[0082] In other words, the partitioning unit 262 may be configured to partition the block 203 into smaller partitions or sub-blocks of the block (which also form blocks) using, for example, quadtree partitioning (QT), binary partitioning (BT), or ternary tree partitioning (TT), or any combination thereof, iteratively, and to perform prediction on, for example, each of the partitions or sub-blocks of the block, wherein the mode selection includes selecting a tree structure of the partitioned block 203, and a prediction mode is applied to each of the partitions or sub-blocks of the block.

[0083] Below, the partitioning (eg, by partitioning unit 260) and prediction processes (by inter-prediction unit 244 and intra-prediction unit 254) performed by exemplary video encoder 20 are described in more detail.

[0084] Division The partitioning unit 262 may partition (or divide) the current block 203 into smaller sections, e.g., square or rectangular sized smaller blocks. These smaller blocks (which may also be called subblocks) may be further partitioned into even smaller sections. This is also called tree partitioning or hierarchical tree partitioning; for example, a root block at root tree level 0 (hierarchical level 0, depth 0) may be recursively partitioned, e.g., into two or more blocks at the next lower tree level, e.g., nodes at tree level 1 (hierarchical level 1, depth 1), which may again be partitioned into two or more blocks at the next lower level, e.g., tree level 2 (hierarchical level 2, depth 2), and so on, until partitioning is terminated, e.g., because a termination criterion is met, e.g., a maximum tree depth or a minimum block size is reached. Blocks that are not further partitioned are also called leaf blocks or leaf nodes of the tree. A tree that uses a partition into two partitions is called a binary tree (BT), a tree that uses a partition into three partitions is called a ternary tree (TT), and a tree that uses a partition into four partitions is called a quad tree (QT).

[0085] As mentioned above, the term "block" as used herein may refer to a portion of a picture, particularly a square or rectangular portion. For example, in the context of HEVC and VVC, a block may be or correspond to a coding tree unit (CTU), a coding unit (CU), a prediction unit (PU), and a transform unit (TU), and / or a corresponding block, such as a coding tree block (CTB), a coding block (CB), a transform block (TB), or a prediction block (PB).

[0086] For example, a coding tree unit (CTU) may be or include a CTB of luma samples, two corresponding CTBs of chroma samples for a picture having a three-sample arrangement, or a CTB of samples for a picture coded using three separate color planes and a syntax structure used to code a monochrome picture or sample. Correspondingly, a coding tree block (CTB) may be an NxN block of samples for some value 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 of luma samples, two corresponding coding blocks of chroma samples for a picture having a three-sample arrangement, or a coding block of samples for a picture coded using three separate color planes and a syntax structure used to code a monochrome picture or sample. Correspondingly, a coding block (CB) may be an MxN block of samples for some values ​​of M and N such that the division of the CTB into coding blocks is a partition.

[0087] For example, in an HEVC embodiment, a coding tree unit (CTU) may be divided into CUs by using a quadtree structure represented as a coding tree. The decision of whether to code a picture area using inter-picture (temporal) prediction or intra-picture (spatial) prediction is made at the CU level. Each CU may be further divided into one, two, or four PUs according to a PU partition type. Within one PU, the same prediction process is applied, and related information is transmitted to the decoder based on the PU. After obtaining residual blocks by applying a prediction process based on the PU partition type, the CU may be partitioned into transform units (TUs) by another quadtree structure similar to the coding tree for the CU.

[0088] For example, in an embodiment according to the latest video coding standard currently under development, called Versatile Video Coding (VVC), quadtree and binary tree (QTBT) partitioning is used to partition coding blocks. In the QTBT block structure, CUs may have either square or rectangular shapes. For example, coding tree units (CTUs) are first partitioned by a quadtree structure. The leaf nodes of the quadtree are further partitioned by a binary tree or ternary (or triple) tree structure. The leaf nodes of the partitioning tree are called coding units (CUs), and their segmentation is used for prediction and transform processing without any further partitioning. This means that CUs, PUs, and TUs have the same block size in the QTBT coding block structure. In parallel, multi-partitioning, for example, ternary tree partitioning, has also been proposed to be used with the QTBT block structure.

[0089] In one example, mode select unit 260 of video encoder 20 may be configured to perform any combination of the partitioning techniques described herein.

[0090] As mentioned above, video encoder 20 is configured to determine or select a best or optimal prediction mode from a (predetermined) set of prediction modes, which may include, for example, intra-prediction modes and / or inter-prediction modes.

[0091] Intra prediction The set of intra prediction modes may include, for example, the 35 different intra prediction modes defined in HEVC, e.g., non-directional modes such as DC (or average) mode and planar mode, or directional modes, or may include, for example, the 67 different intra prediction modes defined for VVC, e.g., non-directional modes such as DC (or average) mode and planar mode, or directional modes.

[0092] The intra prediction unit 254 is configured to generate the intra prediction block 265 using reconstructed samples of neighboring blocks of the same current picture according to an intra prediction mode from a set of intra prediction modes.

[0093] The intra prediction unit 254 (or generally the mode selection unit 260) is further configured to output the intra prediction parameters (or generally information indicating the selected intra prediction mode for the block) to the entropy encoding unit 270 in the form of syntax elements 266 for inclusion in the encoded picture data 21, for example, so that the video decoder 30 may receive the prediction parameters and use them for decoding.

[0094] Inter Prediction The set (or possible) inter prediction modes depends on the available reference pictures (i.e., for example, previous at least partially decoded pictures stored in DBP230) as well as other inter prediction parameters, such as whether the entire reference picture is used to search for the best matching reference block or only a portion of the reference picture, for example, a search window area around the area of ​​the current block, and / or whether pixel interpolation, for example, half / semi-pel and / or quarter-pel interpolation, is applied.

[0095] In addition to the prediction modes mentioned above, skip mode and / or direct mode may also be applied.

[0096] The inter prediction unit 244 may include a motion estimation (ME) unit and a motion compensation (MC) unit (neither of which are shown in FIG. 2). The motion estimation unit may be configured to receive or obtain, for motion estimation, the picture block 203 (current picture block 203 of current picture 17) and the decoded picture 231, or at least one or more already reconstructed blocks, e.g., reconstructed blocks of one or more other / different already decoded pictures 231. For example, a video sequence may include the current picture and the already decoded picture 231, or in other words, the current picture and the already decoded picture 231 may be part of or form a sequence of pictures that form a video sequence.

[0097] The encoder 20 may be configured to, for example, select a reference block from multiple reference blocks of the same or different pictures among 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 to the motion estimation unit as an inter-prediction parameter. This offset is also called a motion vector (MV).

[0098] The motion compensation unit is configured to obtain, e.g., receive, inter prediction parameters and perform inter prediction based on or using the inter prediction parameters to obtain inter prediction block 265. The 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, possibly performing interpolation with sub-pixel accuracy. Interpolation filtering may generate additional pixel samples from known pixel samples, thus potentially increasing the number of candidate prediction blocks that may 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 find the prediction block to which the motion vector points in one of the reference picture lists.

[0099] The motion compensation unit may also generate syntax elements associated with the blocks and video slices for use by video decoder 30 in decoding picture blocks of the video slices.

[0100] Entropy Coding The entropy coding unit 270 is configured to apply, for example, an entropy coding 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 coding method or technique) or bypass (uncompressed) to the quantized coefficients 209, the inter-prediction parameters, the intra-prediction parameters, the loop filter parameters, and / or other syntax elements to obtain coded picture data 21, which may be output via an output 272, for example, in the form of coded bitstream 21, such that, for example, video decoder 30 may receive the parameters and use them for decoding. Encoded bitstream 21 may be transmitted to video decoder 30 or stored in memory for later transmission or retrieval by video decoder 30 .

[0101] 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 directly quantize the residual signal for a particular block or frame without a transform processing unit 206. In another implementation, the encoder 20 may have the quantization unit 208 and the inverse quantization unit 210 combined into a single unit.

[0102] Decoder and decoding method 3 shows an example of a video decoder 30 configured to implement the techniques of the present application. The video decoder 30 is configured to receive coded picture data 21 (e.g., coded bitstream 21), e.g., coded by encoder 20, to obtain a decoded picture 331. The coded picture data or bitstream includes information for decoding the coded picture data, e.g., data representing picture blocks of a coded video slice and associated syntax elements.

[0103] 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, an inter prediction unit 344, and an intra prediction unit 354. Inter prediction unit 344 may be or include a motion compensation unit. Video decoder 30 may, in some examples, perform a decoding path that is generally the reverse of the encoding path described in connection with video encoder 100 of FIG. 2.

[0104] As described in connection with 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 considered to form 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 given with respect to the respective units and functions of video encoder 20 apply mutatis mutandis to the respective units and functions of video decoder 30.

[0105] Entropy Decoding The entropy decoding unit 304 is configured to parse the bitstream 21 (or the coded picture data 21 generally), e.g., to perform entropy decoding on the coded picture data 21 to obtain, e.g., quantized coefficients 309 and / or decoded coding parameters (not shown in FIG. 3 ), e.g., any 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. The entropy decoding unit 304 may be configured to apply a decoding algorithm or scheme corresponding to the encoding scheme described in connection with the entropy coding unit 270 of the encoder 20. The entropy decoding unit 304 may be further configured to provide the inter-prediction parameters, intra-prediction parameters, and / or other syntax elements to the mode selection unit 360 and to provide other parameters to other units of the decoder 30. The video decoder 30 may receive syntax elements at the video slice level and / or the video block level.

[0106] inverse quantization Inverse quantization unit 310 may be configured to receive a quantization parameter (QP) (or information generally related to inverse quantization) and quantized coefficients from encoded picture data 21 (e.g., by parsing and / or decoding by entropy decoding unit 304), and apply inverse quantization to the decoded quantized coefficients 309 based on the quantization parameter to obtain inverse quantized 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 to determine the degree of quantization and, similarly, the degree of inverse quantization to be applied.

[0107] Inverse transformation 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 reconstructed residual blocks 213 in the sample domain. The reconstructed residual blocks 213 may also be referred to as transform blocks 213. The transform may be an inverse transform, e.g., 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 coded picture data 21 (e.g., by parsing and / or decoding by the entropy decoding unit 304) to determine the transform to apply to the dequantized coefficients 311.

[0108] Rebuild The reconstruction unit 314 (e.g., an adder or summer 314) may be configured to add the reconstructed residual block 313 to the prediction block 365, for example, by adding the sample values ​​of the reconstructed residual block 313 and the sample values ​​of the prediction block 365, to obtain a reconstructed block 315 in the sample domain.

[0109] filtering Loop filter unit 320 (either in the coding loop or after the coding loop) is configured to filter reconstructed block 315 to, for example, smooth pixel transitions or otherwise improve video quality, to obtain filtered block 321. 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., a bilateral filter, an adaptive loop filter (ALF), a sharpening filter, a smoothing filter, or a collaborative filter, or any combination thereof. Although loop filter unit 320 is shown in FIG. 3 as being an in-loop filter, in other configurations, loop filter unit 320 may be implemented as a post-loop filter.

[0110] Decoded Picture Buffer The decoded video blocks 321 of the picture are then stored in a decoded picture buffer 330, which stores the decoded picture 331 as a reference picture for subsequent motion compensation with respect to other pictures and / or for output on a display, respectively.

[0111] The decoder 30 is configured to output the decoded pictures 311 for presentation or viewing to a user, for example via an output 312.

[0112] prediction The inter prediction unit 344 may be identical to the inter prediction unit 244 (especially the motion compensation unit), and the intra prediction unit 354 may be functionally identical to the inter prediction unit 254, and performs the partitioning or partitioning decision and prediction based on the partitioning and / or prediction parameters or respective information received from the decoded picture data 21 (e.g., by analyzing and / or decoding by the entropy decoding unit 304). The mode selection unit 360 may be configured to perform prediction (intra or inter prediction) for each block based on the (filtered or unfiltered) reconstructed picture, block, or respective sample to obtain a prediction block 365.

[0113] When a video slice is coded as an intra-coded (I) slice, intra prediction unit 354 of mode select unit 360 is configured to generate a predictive block 365 for a picture block of the current video slice based on the signaled intra prediction mode and data from already decoded blocks 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 select unit 360 is configured to generate a predictive block 365 for a video block of the current video slice based on the 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.

[0114] Mode select unit 360 is configured to determine prediction information for video blocks of the current video slice by parsing motion vectors and other syntax elements, and use the prediction information to generate a predictive block for the current video block being decoded. For example, mode select unit 360 uses some of the received syntax elements to determine the prediction mode (e.g., intra or inter prediction) used to code the video blocks of the video slice, the slice type for inter prediction (e.g., B slice, P slice, or GPB slice), construction information for one or more of the reference picture lists for the slice, motion vectors for each inter-coded video block of the slice, the status of inter prediction for each inter-coded video block of the slice, and other information for decoding video blocks in the current video slice.

[0115] Other variations of the video decoder 30 may be used to decode the coded picture data 21. For example, the decoder 30 may generate an output video stream without the loop filtering unit 320. For example, a non-transform-based decoder 30 may directly inverse quantize the residual signal for a particular block or frame without the inverse transform processing unit 312. In another implementation, the video decoder 30 may have the inverse quantization unit 310 and the inverse transform processing unit 312 combined into a single unit.

[0116] 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 Clip or Shift may be performed on the processing result of the interpolation filtering, motion vector derivation, or loop filtering.

[0117] 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, lower-block motion vectors in affine, planar, and ATMVP modes, temporal motion vectors, etc.). For example, the value of the motion vector is constrained to a predetermined range according to its representation bits. If the representation bits of the motion vector are bitDepth, then 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. Here, two methods are provided for constraining the motion vector.

[0118] Method 1: Delete the overflow MSB (Most Significant Bit) by flowing operation ux= ( mvx+2 bitDepth ) % 2 bitDepth (1) mvx = ( ux >= 2 bitDepth-1 ) ? (ux - 2 bitDepth ) : ux (2) uy= ( mvy+2 bitDepth ) % 2 bitDepth (3) mvy = ( uy >= 2 bitDepth-1 ) ? (uy - 2 bitDepth ) : uy (4)

[0119] For example, if the value of mvx is -32769, after applying equations (1) and (2), the resulting value is 32767. In computer systems, decimal numbers are stored as two's complement numbers. The two's complement of -32769 is 1, 0111, 1111, 1111, 1111 (17 bits), then the MSB is discarded, therefore the resulting two's complement is 0111, 1111, 1111, 1111 (decimal 32767), which is the same as the output by applying equations (1) and (2).

[0120] ux= ( mvpx + mvdx +2 bitDepth ) % 2 bitDepth (5) mvx = ( ux >= 2 bitDepth-1 ) ? (ux - 2 bitDepth ) : ux (6) uy= ( mvpy + mvdy +2 bitDepth ) % 2 bitDepth (7) mvy = ( uy >= 2 bitDepth-1 ) ? (uy - 2 bitDepth ) : uy (8)

[0121] The operations may be applied during the summation of mvp and mvd as shown in equations (5) to (8).

[0122] Method 2: Remove overflow MSB by clipping the value vx = Clip3(-2 bitDepth-1 , 2 bitDepth-1 -1, vx) vy = Clip3(-2 bitDepth-1 , 2 bitDepth-1 -1, vy) The function Clip3 is defined as follows:

number

[0123] 4 is a schematic diagram of a video coding device 400 according to an embodiment of the present disclosure. The video coding device 400 is suitable for implementing the disclosed embodiments as described herein. In an 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.

[0124] Video coding device 400 includes an incoming 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 data, a transmitter unit (Tx) 440 and an outgoing port 450 (or output port 450) for transmitting data, and a memory 460 for storing data. Video coding device 400 may also include optical-electrical (OE) and electrical-optical (EO) components coupled to the incoming port 410, receiver unit 420, transmitter unit 440, and outgoing port 450 for emitting or receiving optical or electrical signals.

[0125] The processor 430 is implemented by 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 incoming port 410, the receiver unit 420, the transmitter unit 440, the outgoing 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 implements, processes, prepares, or provides various coding operations. Thus, the inclusion of the coding module 470 significantly improves the functionality of the video coding device 400 and results in the transition of the video coding device 400 to different states. Alternatively, the coding module 470 is implemented as instructions stored in the memory 460 and executed by the processor 430.

[0126] Memory 460 may include one or more disks, tape drives, and solid-state drives, and may be used as an overflow data storage device for storing programs when such programs are selected for execution and for storing instructions and data read during execution of the programs. 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).

[0127] FIG. 5 is a simplified block diagram of an apparatus 500 that may be used as either or both of source device 12 and destination device 14 of FIG. 1, according to an exemplary embodiment.

[0128] Processor 502 of apparatus 500 may be a central processing unit. Alternatively, processor 502 may be any other type of device or devices, existing or later developed, that can manipulate or process information. While the disclosed implementations may be performed by a single processor, e.g., processor 502, as shown, speed and efficiency advantages may be realized by using two or more processors.

[0129] The memory 504 of the apparatus 500 may, in implementation, be a read-only memory (ROM) device or a random-access memory (RAM) device. Any other suitable type of storage device may be used as the memory 504. The memory 504 may include code and data 506 that is accessed by the processor 502 using a bus 512. The memory 504 may further include an operating system 508 and application programs 510, which 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, which further include a video coding application that performs the methods described herein.

[0130] The apparatus 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 touch-sensing elements operable to sense touch input. The display 518 may be coupled to the processor 502 via the bus 512.

[0131] Although shown here as a single bus, bus 212 of device 500 may be comprised of multiple buses. Additionally, secondary storage 514 may be directly coupled to other components of device 500 or may be accessed over a network, and may include a single integrated unit such as a memory card or multiple units such as multiple memory cards. Accordingly, device 500 may be implemented in a wide variety of configurations.

[0132] Merge candidate list The process of building a merge motion candidate list is introduced by the ITU-T H.265 standard. In another embodiment, the merge motion candidate list is used by the enhanced merge prediction of Versatile Video Coding (VVC).

[0133] The block merge operation is a special mode (also called "merge mode") for coding motion data. The block merge operation allows a current block to use the same motion information of a neighboring block. The motion information includes motion data, which includes information on whether one or two reference picture lists are used, as well as a reference index and a motion vector for each reference picture list. The block merge operation is particularly useful when two neighboring blocks correspond to the same non-deforming object in a picture frame. In this case, the two blocks may be predicted using the same motion vector and the same reference picture, and therefore the motion information is identical for both blocks.

[0134] In implementation, after checking whether neighboring blocks are available and contain motion information, some further redundancy checks are performed before considering all motion data of neighboring blocks as motion information candidates.

[0135] In implementation, the merge candidate list is constructed by including the following five types of candidates in order: 1) Spatial MVP from spatially neighboring CUs 2) Temporal MVP from co-located CUs 3) MVP based on history from FIFO table 4) Average MVP of the pair 5) Zero MV

[0136] The size of the merge list is signaled in the slice header, and the maximum allowed size of the merge list is, for example, 6. For each CU code in merge mode, the index of the best merge candidate is coded.

[0137] A generation process for each category of merge candidates is provided.

[0138] Deriving spatial candidates In implementation, up to four merge candidates are selected from the candidates at the positions shown in FIG. 12. The order of derivation is B1, A1, B0, A0, and B2. Position B2 is considered only when any CU at positions A0, B0, B1, A1 is unavailable (e.g., because it belongs to another slice or tile) or is intra-coded. After the candidate at position B1 is added, the addition of the remaining candidates undergoes a redundancy check to ensure that candidates with the same motion information are removed from the list so as to improve coding efficiency. To reduce computational complexity, not all possible candidate pairs are considered in the above redundancy check. Instead, only pairs connected by arrows in FIG. 13 are considered, and a candidate is only added to the list if the corresponding candidate used for the redundancy check does not have the same motion information.

[0139] The order, location, and number of spatial neighbors are contemplated as variable during implementation, and the above examples may not be considered limiting.

[0140] Temporal candidate derivation In implementation, only one candidate is added to the list. In particular, in deriving this temporal merge candidate, a scaled motion vector is derived based on the co-located CU belonging to the co-located reference picture. The reference picture list used for deriving the co-located CU is explicitly signaled in the slice header. The scaled motion vector for the temporal merge candidate is obtained as shown by the dashed line in Figure 14 and is scaled from the motion vector of the co-located CU using POC distances tb and td, where tb is defined to be the difference in POC between the current picture's reference picture and the current picture, and td is defined to be the difference in POC between the co-located picture's reference picture and the co-located picture. The reference picture index of the temporal merge candidate is set equal to zero.

[0141] The location for the temporal candidate is selected between candidate C0 and candidate C1, as shown in Figure 15. If the CU at location C0 is unavailable, intra-coded, or outside the current row of the CTU, location C1 is used. Otherwise, location C0 is used in deriving the temporal merge candidate.

[0142] History-based merging candidate derivation History-based MVP (HMVP) merge candidates are added to the merge list after spatial MVP and TMVP. In the implementation, the motion information of already coded blocks is stored in a table and used as the MVP of the current CU. A table with multiple HMVP candidates is maintained during the encoding / decoding process. The table is reset (emptied) when a new CTU row is encountered. Whenever there is an inter-coded CU that is not a lower-order block, the associated motion information is added to the last entry of the table as a new HMVP candidate.

[0143] For example, the size S of the HMVP table is set to 5, indicating that up to five history-based MVPs (HMVPs) may be added to the table. When inserting a new motion candidate into the table, a constrained first-in-first-out (FIFO) rule is utilized, and a redundancy check is first applied to see if an identical HMVP exists in the table. If so, the identical HMVP is removed from the table, and then all HMVP candidates are moved forward.

[0144] HMVP candidates may be used in the process of building a merge candidate list. The most recent few HMVPs in the table are examined in order and inserted into the candidate list after the TMVP candidate. Redundancy checks are applied to HMVP candidates up to spatial or temporal merge candidates.

[0145] Different simplifications may be introduced to reduce the number of redundancy check operations. Generally, the process of building a merge candidate list from HMVP is terminated when the total number of available merge candidates reaches the maximum allowed merge candidates minus one.

[0146] Deriving Pairwise Average Merge Candidates An average candidate pair is generated by averaging a predefined pair of candidates in an existing merge candidate list, where the predefined pair is defined as (0, 1), for example, and the number represents the merge index into the merge candidate list. An averaged motion vector is calculated separately for each reference list. If both motion vectors are available in one list, these two motion vectors are averaged even if they point to different reference pictures; if only one motion vector is available, that one is used as is; if no motion vector is available, this list remains invalid.

[0147] In the example of building a merge candidate list according to ITU-T H.265, the merge candidate list is built based on the following candidates: 1. Up to four spatial candidates derived from five spatially neighboring blocks; 2. A temporal candidate is derived from two temporally co-located blocks; 3. Additional candidates, including combined bi-predictive candidates; and 4. Zero motion vector candidates

[0148] spatial candidate The motion information of spatially neighboring blocks is first added to the merge candidate list as motion information candidates (in an example, the merge candidate list may be an empty list before the first motion vector is added to the merge candidate list). Here, the neighboring blocks that may be inserted into the merge list are shown in FIG. 7b. For inter-prediction block merging, up to four candidates are inserted into the merge list by sequentially examining A1, B1, B0, A0, and B2 in this order.

[0149] The motion information may include motion data, which includes information on whether one or two reference picture lists are used, as well as a reference index and a motion vector for each reference picture list.

[0150] In the example, after checking whether neighboring blocks are available and whether they contain motion information, some further redundancy checks are performed before considering all the motion data of neighboring blocks as motion information candidates. These redundancy checks can be divided into the following two categories: Category 1, avoid having candidates with redundant motion data in the list Category 2, which creates redundant syntax and prevents merging two compartments that can be expressed by other means

[0151] temporal candidate 7a shows the coordinates of blocks from which temporal motion information candidates are retrieved. A co-located block is a block that has the same -x, -y coordinates as the current block but is on a different picture (one of the reference pictures). A temporal motion information candidate is added to a merge list if the list is not full (in an example, a merge list is not full when the amount of candidates in the merge list is less than a threshold, for example, the threshold may be 4, 5, 6, etc.).

[0152] Generated candidates If the merge list is not yet full after the insertion of the spatial and temporal motion information candidates, the generated candidates are added to fill the list. In an example, the size of the merge list is indicated in the sequence parameter set and is fixed throughout the coded video sequence.

[0153] Bi-prediction Inter-prediction mode is called "bi-prediction," in which two motion vectors are used to predict a block. The motion vectors may point to the same or different reference pictures, and the reference pictures may be indicated by a reference picture list ID and a reference picture index. For example, a first motion vector may point to the first picture of a reference picture list L0, and a second motion vector may point to the first picture of a reference picture list L1. Two reference picture lists (e.g., L0 and L1) may be held, and the picture pointed to by the first motion vector is selected from list L0, and the picture pointed to by the second motion vector is selected from list L1.

[0154] In an example, if the motion information indicates bi-prediction, then the motion information includes the following two parts: L0 part: motion vectors and reference picture indices pointing to entries in the reference picture list L0 L1 part: motion vectors and reference picture indices pointing to entries in the reference picture list L1

[0155] Picture Order Count (POC): A variable associated with each picture that uniquely identifies the associated picture among all pictures in a CVS (Coded Video Sequence). When the associated picture is to be output from the decoded picture buffer, the POC is used to indicate the position of the associated picture in output order relative to the output order positions of other pictures in the same CVS that are to be output from the decoded picture buffer.

[0156] The reference picture list L0 or L1 may include one or more reference pictures, each of which is identified by a POC. The association of each reference index with a POC value may be signaled in the bitstream. As an example, the reference picture lists L0 and L1 may include the following reference pictures:

[0157] [Table 2]

[0158] In the above example, the first entry (indicated by reference index 0) of reference picture list L1 is a reference picture with a POC value of 13. The second entry (indicated by reference index 1) of reference picture list L1 is a reference picture with a POC value of 14.

[0159] Triangular prediction mode The concept of triangular prediction mode is a triangular partition for motion compensation prediction. As an example shown in Figure 9, a CU is divided into two triangular prediction units in a diagonal or anti-diagonal direction. Each triangular prediction unit in a CU is inter-predicted using a uni-predictive motion vector and a reference frame index derived from a uni-predictive candidate list. After predicting the triangular prediction unit, an adaptive weighting process is performed on the diagonal edge. Then, a transform and quantization process is applied to the entire CU. It is noted that this mode only applies to skip mode and merge mode.

[0160] In triangular prediction mode, a block is divided into two triangular parts (as in FIG. 9), and each part can be predicted using one motion vector. The motion vector used to predict one triangular part (represented by PU1) can be different from the motion vector used to predict the other triangular part (represented by PU2). It is noted that to reduce the complexity of performing triangular prediction mode, each part can be predicted using only a single motion vector (uni-prediction). In other words, PU1 and PU2 cannot be predicted using bi-prediction.

[0161] Lower Block Prediction Mode Triangular prediction mode is a special case of sub-block prediction, in which a block is divided into two blocks. In the above example, two block division directions are shown (45-degree partition and 135-degree partition). However, it should be noted that other partition angles and partition ratios are also possible (for example, the example of FIG. 11).

[0162] In some examples, a block is divided into two sub-block parts, and each part is applied with uni-prediction. Compared with triangular prediction mode, the difference is how the block is divided into two parts, and therefore it represents a generalized version of triangular prediction. For example, the sub-block may be rectangular or non-rectangular depending on the angle of the partition. In some examples, the current block consists of two prediction units, and the two prediction units are divided by a virtual dividing line. In this case, the current block is said to be predicted by geometric prediction mode.

[0163] The merge list construction process for ITU-T H.265 and VVC outputs a list of motion information candidates. The merge list construction process for VVC is described in the document JVET-L1001_v2 Versatile Video Coding (Draft 3), published at http: / / phenix.it-sudparis.eu / jvet / , in section "8.3.2.2 Derivation process for luma motion vectors for merge mode." The term motion information refers to the motion data required to perform the motion compensation prediction process. Motion information typically refers to the following information: Whether the block is uni- or bi-predictive ID of the reference picture used in the prediction (two IDs if the block applies bi-prediction) Motion vector (two motion vectors if the block is bi-predicted) Additional Information

[0164] In the latest version of the VVC specification draft text, the merge list construction process is described in the document JVET-L1001_v7 Versatile Video Coding (Draft 3), section "8.3.2.2 Derivation process for luma motion vectors for merge mode."

[0165] It is noted that the aspects presented in the present application are not limited to the above three examples. The merge list construction processes described in the above examples have in common that the constructed merge list is used to obtain a prediction of a coding block when a triangular prediction mode is not applied to the coding block. The method of the present disclosure for generating a list of second motion information candidates using candidates of a merge list (first list), wherein the candidates of the merge list are generated according to any method, which may be a method described in any version of VVC or ITU-T H.265.

[0166] In VVC and H.265, the output of the merge list construction process includes N candidate motion information. The number N is generally included in the bitstream and can be a positive integer, such as 5, 6, etc. The candidates included in the constructed merge list may include uni-predictive or bi-predictive information. This means that the candidates selected from the merge list may exhibit bi-predictive behavior.

[0167] When a triangular prediction mode is applied to a coding block, each triangular portion of the coding block must be applied uni-predictively, not bi-predictively (due to hardware implementation concerns). This means that candidates in a normal merge list that indicate bi-prediction cannot be used, which causes performance degradation.

[0168] The problem can be reframed as follows: If a block applies triangular prediction mode, an indication is included in the bitstream and is used to indicate the motion information used to predict each triangular portion. For example, the indication may be in the form of two merge indices, where the first merge index specifies the entry in the merge list that is applied to predict the first portion, and the second merge index specifies the entry in the merge list that is applied to predict the second portion. · Applying bi-prediction to individual parts is prohibited, which means that the motion information indicated to be used in the respective part must indicate uni-prediction. It is possible to have uni-predictive and bi-predictive motion information candidates in the merge list. This causes a performance degradation, since bi-predictive candidates are forbidden to be selected. Since only uni-predictive candidates can be used, the size of the candidate list is effectively reduced.

[0169] In VVC, if a block has a certain size (4 samples wide or 4 samples high), applying bi-prediction to predict the block is prohibited. An 8x4 / 4x8 block is the smallest possible inter-prediction block that can be realized using block partitioning. Because hardware implementations need to consider the smallest possible block as their worst-case complexity metric, bi-prediction is not allowed for the smallest blocks due to hardware complexity concerns. Therefore, prohibiting bi-prediction for the smallest blocks reduces the worst-case complexity of the hardware implementation.

[0170] For VVC, a similar problem to problem 1 exists when the blocks have a size of 8x4 / 4x8 and when the blocks are coded in merge mode.

[0171] In an embodiment (embodiment 1) of the present disclosure, the following steps are followed to construct a merge list.

[0172] Step 1: Construct a motion candidate list (first list) containing motion information candidates with uni-prediction or bi-prediction.

[0173] The first list may be constructed according to the methods of ITU-T H.265 and VVC, see the above examples and disclosures about the merge list construction process of H.265 and VVC.

[0174] Step 2: Construct a second list using the candidates from the first list as follows:

[0175] Start with the first candidate in the first list.

[0176] Step 2.1: If the candidate is a uni-prediction candidate, add the candidate (motion information candidate) to a second list.

[0177] or Step 2.2: If the candidate is a bi-predictive candidate, two uni-predictive candidates are generated and the two uni-predictive candidates are added to a second list according to the following order: The first motion information candidate contains a motion vector and a reference picture index corresponding to the L0 reference picture list (the candidate is set as a uni-prediction candidate before inserting it into the second list). The second motion information candidate includes a motion vector and a reference picture index corresponding to the L1 reference picture list (the candidate is set as a uni-prediction candidate before inserting it into the second list).

[0178] Step 2.3: Proceed to the next candidate in the first list and continue with Step 2.1 or Step 2.2 until a specified amount of candidates have been collected in the second list or until all candidates in the first list have been processed.

[0179] The first merge list and the second merge list may be used in the inter prediction process of the current block.

[0180] In the example, when triangular prediction is applied to the current block, two candidates from the second list are selected to perform triangular prediction, one candidate is used in the prediction process of the first triangular portion, and the other candidate is used in the prediction of the second triangular portion.

[0181] In another example, if the block size of the current block is less than or equal to a threshold (e.g., the threshold may be 16) or the block size of the current block is the smallest size predefined or signaled in the parameter set, one candidate from the second list is selected to perform inter prediction for the current block. In this example, when the size of the current block is small, bi-prediction is not allowed for the current block.

[0182] In another example, if a merge mode is applied to the current block and a triangular prediction mode is not applied to the current block, one candidate from the first list is selected to perform prediction of the current block, which is the same as the related process disclosed in ITU-T H.265 or VVC.

[0183] In the example, the first motion candidate list is a merge list.

[0184] It is noted that in a possible implementation, the candidate list may not be an independent list, since the candidate list for triangular (or lower block) prediction is derived from the candidate list for the merge mode. Candidates in the second candidate list may be represented by indicator points relative to candidates in the candidate list for the merge mode.

[0185] Embodiment 1 discloses a method for constructing a motion information candidate list (second list), where the second list includes uni-prediction candidates.

[0186] If triangular prediction is not applied to the block, the first list is used in predicting the block. In the example, the first list is used for coding blocks that are indicated to apply merge mode but are not indicated to apply triangular prediction mode.

[0187] The second list is constructed based on the first list. If triangular prediction is applied to the block, motion information (or motion vector) candidates are selected from the second list. The second list includes uni-predictive candidates, and the candidates may be applied to the first and second triangular portions of the block. In an example, if a triangular merge mode is applied to the block, two merge indexes are coded into the bitstream. The merge indexes identify which candidate from the second list is used for the first or second triangular portion of the block.

[0188] In another example, if the block size of the current block is less than or equal to a threshold (e.g., the threshold may be 16) or the block size of the current block is the smallest size predefined or signaled in the parameter set, one merge index is coded into the bitstream to identify which candidate from the second list is used to predict the block. If the block size of the current block is greater than a threshold (e.g., the threshold may be 16) or the block size of the current block is not the smallest size predefined or signaled in the parameter set, a merge index is coded into the bitstream to identify which candidate from the first list is used to predict the block.

[0189] 6 shows a flowchart of one possible implementation of embodiment 1. The flowchart shows the construction of a second motion candidate list based on a first motion candidate list. According to 602, if triangular prediction is applied to a block, the second motion candidate list is used to predict the block, and if triangular prediction is not applied to the block, the first motion candidate list is used to predict the block. In another example, the condition of 602 may include a block size check. Depending on the result of the block size check, the first motion candidate list or the second motion candidate list may be used to predict the block.

[0190] In another example, if it is determined that the block does not apply triangular prediction, other conditions may be checked to determine whether the block uses the first motion candidate list. In one example, if it is determined that the block does not apply triangular prediction, it is further determined whether the block applies a merge mode. If the merge mode is applied, the first motion candidate list is used to predict the block, and if the merge mode is not applied, other methods of predicting the current block (e.g., intra prediction) may be applied.

[0191] According to embodiment 1, a second motion candidate list is constructed based on the first motion candidate list. The second list may have the advantage of only including uni-prediction candidates and therefore not including unusable candidates (for example, bi-prediction candidates). Therefore, the indicator for signaling which candidate is used can be represented by fewer bits, which improves compression efficiency.

[0192] In an embodiment (embodiment 2) of the present disclosure, the following steps are followed to construct a merge list.

[0193] Step 1: Construct a motion candidate list (first list) containing motion information candidates with uni-prediction or bi-prediction.

[0194] The first list may be constructed according to the methods of ITU-T H.265 and VVC, see the above examples and disclosures on the merge list construction process of HEVC and VVC.

[0195] Step 2: Construct a second list using the candidates from the first list as follows: Start with the first candidate in the first list.

[0196] Step 2.1: If the candidate is a uni-prediction candidate, add the candidate (motion information candidate) to a second list.

[0197] or Step 2.2: If the candidate is a bi-predictive candidate, two uni-predictive candidates are generated and the two uni-predictive candidates are added to a second list according to the following order: The first candidate contains a motion vector and a reference picture index corresponding to the L0 reference picture list: the motion vector is denoted mv_L0, and the POC value of the reference picture (calculated based on the reference picture index in list L0) is denoted POC_L0. The second candidate includes a motion vector and a reference picture index corresponding to the L1 reference picture list. The motion vector is denoted as mv_L1, and the POC value of the reference picture (calculated based on the reference picture index in list L1) is denoted as POC_L1. If POC_L0 is equal to POC_L1 and mv_L0 is similar to mv_L1, then the second candidate is not included in the second list. If either POC_L0 is not equal to POC_L1 or mv_L0 is not similar to mv_L1, the second candidate is included in the second list.

[0198] Step 2.3: Proceed to the next candidate in the first list and continue with Step 2.1 or Step 2.2 until a specified amount of candidates have been collected in the second list or until all candidates in the first list have been processed.

[0199] The first merge list and the second merge list may be used in the inter prediction process of the current block.

[0200] In the example, when triangular prediction (or lower-level block prediction) is applied to the current block, two candidates from the second list are selected to perform triangular prediction (or lower-level block prediction), and one candidate is used in the prediction process of the first triangular portion and the other candidate is used in the prediction of the second triangular portion.

[0201] In another example, if the block size of the current block is less than or equal to a threshold (e.g., the threshold may be 16) or the block size of the current block is the smallest size predefined or signaled in the parameter set, one motion information candidate from the second list is selected to perform inter prediction for the current block. In this example, when the size of the current block is small, bi-prediction is not allowed for the current block.

[0202] In another example, if a merge mode is applied to the current block and a triangular prediction mode is not applied to the current block, one candidate from the first list is selected to perform prediction of the current block, which is the same as the related process disclosed in ITU-T H.265 or VVC.

[0203] In the example, if POC_L0 is equal to POC_L1 and mv_L0 is the same as mv_L1, the second candidate in step 2.2 is not added to the second list.

[0204] In another example, if the reference picture index of the L0 portion is the same as the reference picture index of the L1 portion and if mv_L0 is identical to (or alternatively similar to) mv_L1, the second candidate of step 2.2 is not added to the second list.

[0205] In an example, the similarity of two motion vectors may be determined by the following inequality: -K< (MV1.x - MV2.x) < K and -K< (MV1.y - MV2.y) < K where MV1.x represents the x-component of the first motion vector (MV2.x has the same meaning as MV1.x), MV1.y represents the y-component (MV2.y has the same meaning as MV1.y), and K is a positive number. In this example, if both inequalities hold, then motion vector MV1 is considered to be similar to motion vector MV2.

[0206] In another example, similarity may be determined based on the following equation: (MV1.x >> N) - (MV2.x >> N) == K and (MV1.x >> N) - (MV2.x >> N) == K

[0207] where x>>y denotes an arithmetic right shift of the two's complement integer representation of x by y binary places. This function is defined only for non-negative integer values ​​of y. The bit shifted to the most significant bit (MSB) as a result of the right shift has a value equal to the MSB of x before the shift operation. "==" is a rational operation that is true when both sides of the operator are identical. In this example, motion vector MV1 is considered to be similar to motion vector MV2 if both equalities hold.

[0208] In the example, the first motion candidate list is a merge list.

[0209] It is noted that in a possible implementation, the candidate list may not be an independent list, since the candidate list for triangular (or lower block) prediction is derived from the candidate list for the merge mode. Candidates in the second candidate list may be represented by indicators pointing to candidates in the candidate list for the merge mode.

[0210] A flowchart of one possible implementation of embodiment 2 is shown in Figure 8. The difference from embodiment 1 lies in step 811. In step 811, the L1 part of the bi-predicted candidate is compared with the L0 part (the motion vector of the L0 part is compared with the motion vector of the L1 part, and the POC of the reference picture of the L0 part is compared with the POC of the reference picture of the L1 part). If the L0 part is similar to the L1 part according to a similarity metric, then the uni-predictive candidate generated based on the L1 part is not inserted into the second motion candidate list.

[0211] In step 2.2, the second candidate (which is a uni-predictive candidate generated based on the L1 portion of the bi-predictive candidates in the first motion candidate list) is added to the second motion candidate list only if the second candidate is sufficiently different from the first candidate (which is a uni-predictive candidate generated based on the L0 portion of the bi-predictive candidates in the first motion candidate list).

[0212] When an L1 portion is similar (or identical) to an L0 portion, the L1 portion is not inserted into the second list, thereby increasing compression efficiency.

[0213] In Figure 8, step 2.2 is indicated by 807, 811, and 808. First, 807 inserts the L1 part of the bi-predictive motion candidate into the second list. Then, 811 compares the last entry of the second list (indicated by the index value last_entry) with the previous entry of the second list (indicated by the index value last_entry - 1). If the POC value of the last entry is the same as the POC value of the previous entry and the motion vector of the last entry is identical to the motion vector of the previous entry, the last entry is deleted from the second list by 808. It is noted that the combination of 807, 811, and 808 corresponds to step 2.2 of the embodiment of the present disclosure.

[0214] In an embodiment (embodiment 3) of the present disclosure, the following steps are followed to construct a merge list.

[0215] Step 1: Construct a motion candidate list (first list) containing motion information candidates with uni-prediction or bi-prediction.

[0216] The first list may be constructed according to the methods of ITU-T H.265 and VVC, see the above examples and disclosures on the merge list construction process of HEVC and VVC.

[0217] Step 2: The first list is updated as follows: For every entry in the first list, Check whether the candidate is a bi-predictive candidate. If the candidate is a bi-predictive candidate, the motion vector belonging to the L0 part is denoted as mv_L0, the reference index is denoted as ref_idx_L0, and the POC value of the reference picture (calculated based on the reference picture index in list L0) is denoted as POC_L0. The motion vector belonging to the L1 part is denoted as mv_L1, the reference index is denoted as ref_idx_L1, and the POC value of the reference picture (calculated based on the reference picture index in list L1) is denoted as POC_L1. If POC_L0 is equal to POC_L1 and mv_L0 is similar to mv_L1 (or in another example embodiment is identical), the candidate is updated as a uni-predictive candidate, the motion vector is set to MV_L0, the reference picture list is set to L0, and the reference index is set to ref_idx_L0.

[0218] Step 3: Construct a second list using the candidates from the first list as follows:

[0219] Step 3.1: Start with the first candidate in the updated first list.

[0220] Step 3.2: If the candidate is a uni-prediction candidate, add the candidate (motion information candidate) to a second list.

[0221] or Step 3.3: If the candidate is a bi-predictive candidate, two uni-predictive candidates are generated and the two uni-predictive candidates are added to a second list according to the following order: The first candidate contains the motion vectors and reference picture indices corresponding to the L0 reference picture list. The second candidate contains the motion vectors and reference picture indices corresponding to the L1 reference picture list.

[0222] Step 3.4: Proceed to the next candidate in the first list and continue with Step 3.2 or Step 3.3 until a specified amount of candidates have been collected in the second list or until all candidates in the first list have been processed.

[0223] In the example, when triangular prediction is applied to the current block, two candidates from the second list are selected to perform triangular prediction, one candidate is used in the prediction process of the first triangular portion, and the other candidate is used in the prediction of the second triangular portion.

[0224] In another example, if the block size of the current block is less than or equal to a threshold (e.g., the threshold may be 16) or the block size of the current block is the smallest size predefined or signaled in the parameter set, one motion information candidate from the second list is selected to perform inter prediction for the current block. In this example, when the size of the current block is small, bi-prediction is not allowed for the current block.

[0225] In another example, if merge mode is applied to the current block and triangular prediction mode is not applied to the current block (or the block size of the current block exceeds a threshold (e.g., the threshold may be 16) or the block size of the current block is not the smallest size predefined or signaled in the parameter set), a candidate from the first list is selected to perform prediction of the current block.

[0226] In an embodiment (embodiment 4) of the present disclosure, the following steps are followed to construct a merge list.

[0227] Step 1: Construct a motion candidate list (first list) containing motion information candidates with uni-prediction or bi-prediction.

[0228] The first list may be constructed according to the methods of ITU-T H.265 and VVC, see the above examples and disclosures on the merge list construction process of HEVC and VVC.

[0229] Step 2: Construct a second list using the candidates from the first list as follows:

[0230] Step 2.1: Start with the first motion information candidate in the first list.

[0231] Step 2.2: If the candidate is a uni-prediction candidate, add the candidate (motion information candidate) to a second list.

[0232] Step 2.3: Proceed to the next candidate in the first list and continue with step 2.2 until a specified amount of candidates have been collected in the second list or until all candidates in the first list have been processed.

[0233] Step 2.4: Start with the first candidate in the first list.

[0234] Step 2.5: If the candidate is a bi-predictive candidate, two uni-predictive candidates are generated and added to a second list according to the following order: The first motion information candidate includes a motion vector and a reference picture index corresponding to the L0 reference picture list. Add the first candidate to a second list. The second motion information candidate includes a motion vector and a reference picture index corresponding to the L1 reference picture list. If the second list is not full, add the second candidate to the second list.

[0235] Step 2.6: Proceed to the next candidate in the first list and continue with step 2.5 until a specified amount of candidates have been collected in the second list or until all candidates in the first list have been processed.

[0236] The first merge list and the second merge list may be used in the inter prediction process of the current block.

[0237] It is noted that in a possible implementation, the candidate list may not be an independent list, since the candidate list for triangular (or lower block) prediction is derived from the candidate list for the merge mode. Candidates in the second candidate list may be represented by indicators pointing to candidates in the candidate list for the merge mode.

[0238] In the example, when triangular prediction is applied to the current block, two candidates from the second list are selected to perform triangular prediction, one candidate is used in the prediction process of the first triangular portion, and the other candidate is used in the prediction of the second triangular portion.

[0239] In another example, if the block size of the current block is less than or equal to a threshold (e.g., the threshold may be 16) or the block size of the current block is the smallest size predefined or signaled in the parameter set, one candidate from the second list is selected to perform inter prediction for the current block. In this example, when the size of the current block is small, bi-prediction is not allowed for the current block.

[0240] In another example, if a merge mode is applied to the current block and a triangular prediction mode is not applied to the current block, one candidate from the first list is selected to perform prediction of the current block, which is the same as the related process disclosed in ITU-T H.265 or VVC.

[0241] In an embodiment (embodiment 5) of the present disclosure, the size of the second list (motion candidate list) is equal to or smaller than the size of the first list.

[0242] For example, if M is determined to be less than or equal to N, the size of the second list is set equal to M, where N is the size of the first list (the number of motion candidates). Otherwise (if M is determined to be greater than N), the size of the second list is set equal to N.

[0243] In another example, N may be derived from an indicator coded into the bitstream, and M may be a predefined number. M and N may be positive integers, e.g., M may be equal to 5 and N may be equal to 6.

[0244] An example of this embodiment is as follows: The value M (indicating the maximum size of the second list) may be 5, which is predetermined. Also, the value of N (the size of the first list) may be signaled in the sequence parameter set (SPS). If the value of N is signaled as 6, the size of the second list is set to be equal to 5, since the size of the first list is larger than the size of the second list. In another scenario, if N is signaled as 3 in the SPS, then the size of the second list is also set to be equal to 3.

[0245] In another example, N may be derived from an indicator coded in the bitstream, and M may be derived from an indicator also coded in the bitstream. In this example, the indicator used to derive the value of M may not indicate a value of M greater than N.

[0246] In another example, in ITU-T H.265, the size of the merge list (first list) is N, where N may be modified based on syntax elements coded in the bitstream. The value of N may be a positive integer (e.g., the value of the positive integer is between 2 and 5), and the value of the positive integer is signaled in the SPS. The size of the merge list is fixed for the entire video sequence.

[0247] According to Embodiment 5, the size of the second list is less than or equal to the size of the first list. In some examples, the size of the second list is also fixed for the purpose of error tolerance. According to the above-described Embodiments 1 to 4, the second list is constructed based on the first list. The size of the second list is less than or equal to the size of the first list. If all candidates in the first list are single-prediction candidates, in this case, the maximum number of movement candidates that can be inserted into the second list is equal to the number of candidates in the first list. Therefore, when the size of the second list is set to be less than or equal to the first list, it is guaranteed that the second list is always completely filled.

[0248] According to another embodiment (Embodiment 6), the size of the second list is determined based on the size of the current block. When the size of the current block is less than the threshold, the size of the second list is set to be equal to K, and when the size of the current block is greater than or equal to the threshold, the size of the second list is set to be equal to L. The size of the block can be determined based on its width and height (for example, width times height). K and L are positive integers where K < L.

[0249] For example, when the width times height of the block is 128 or more, the size of the second list can be set to be equal to 5. When the width times height of the block is less than 128, the size of the second list can be set to be equal to 3.

[0250] In another example, when the width of the block is 8 or less or the height of the block is 8 or less, the size of the second list is set to be equal to 3. When both the width and height of the block exceed 8, then the size of the second list is set to be equal to 5.

[0251] In an embodiment of the present disclosure (Embodiment 7), the following steps are followed to construct the merge list.

[0252] Step 1: Construct a motion candidate list (first list) containing motion information candidates with uni-prediction or bi-prediction.

[0253] The first list may be constructed according to the methods of ITU-T H.265 and VVC, see the above examples and disclosures about the merge list construction process of H.265 and VVC.

[0254] Step 2: Construct a second list using the candidates from the first list as follows:

[0255] Step 2.1: Start with the first candidate in the first list.

[0256] Step 2.2: If the motion information candidate is a uni-prediction candidate, add the candidate (motion information candidate) to a second list.

[0257] or Step 2.3: If the motion information candidate is a bi-predictive candidate, one uni-predictive candidate is generated based on the bi-predictive candidate as follows and added to the second list. The generated uni-predictive motion information candidates include motion vectors and reference picture indices corresponding to the L0 reference picture list (the candidates are set as uni-predictive candidates before inserting them into the second list).

[0258] Step 2.4: Proceed to the next candidate in the first list and continue with Step 2.2 or Step 2.3 until a specified amount of candidates have been collected in the second list or until all candidates in the first list have been processed.

[0259] The first merge list and the second merge list may be used in the inter prediction process of the current block.

[0260] In the example, when triangular prediction is applied to the current block, two candidates from the second list are selected to perform triangular prediction, and one candidate is used in the prediction process of the first triangular portion and the other candidate is used in the prediction of the second triangular portion.

[0261] In another example, if the block size of the current block is less than or equal to a threshold (e.g., the threshold may be 16) or the block size of the current block is the smallest size predefined or signaled in the parameter set, one candidate from the second list is selected to perform inter prediction for the current block. In this example, when the size of the current block is small, bi-prediction is not allowed for the current block.

[0262] In another example, if a merge mode is applied to the current block and a triangular prediction mode is not applied to the current block, one candidate from the first list is selected to perform prediction of the current block, which is the same as the related process disclosed in ITU-T H.265 or VVC.

[0263] In the example, the first motion candidate list is a merge list.

[0264] It is noted that in a possible implementation, the candidate list may not be an independent list, since the candidate list for triangular (or lower block) prediction is derived from the candidate list for the merge mode. Candidates in the second candidate list may be represented by indicators pointing to candidates in the candidate list for the merge mode.

[0265] Embodiment 7 discloses a method for constructing a motion information candidate list (second list), where the second list includes uni-prediction candidates.

[0266] If triangular prediction is not applied to the block, the first list is used in predicting the block. In the example, the first list is used for coding blocks that are indicated to apply a merge mode but are not indicated to apply a triangular prediction mode.

[0267] The second list is constructed based on the first list. If triangular prediction is applied to the block, motion information (or motion vector) candidates are selected from the second list. The second list includes uni-predictive candidates, and the candidates may be applied to the first and second triangular portions of the block. In an example, if a triangular merge mode is applied to the block, two merge indexes are coded into the bitstream. The merge indexes identify which candidate from the second list is used for the first or second triangular portion of the block.

[0268] In another example, if the block size of the current block is less than or equal to a threshold (e.g., the threshold may be 16) or the block size of the current block is the smallest size predefined or signaled in the parameter set, one merge index is coded into the bitstream to identify which candidate from the second list is used to predict the block. If the block size of the current block is greater than a threshold (e.g., the threshold may be 16) or the block size of the current block is not the smallest size predefined or signaled in the parameter set, a merge index is coded into the bitstream to identify which candidate from the first list is used to predict the block.

[0269] According to embodiment 7, if a motion candidate in the first list is a bi-predictive candidate, the candidate is added to the second list after the bi-predictive candidate is changed to a uni-predictive candidate. The bi-predictive motion candidate includes two motion vectors and two reference picture indexes, one pair corresponding to the reference picture list L0 and the other pair corresponding to the reference picture list L1. The changed uni-predictive candidate includes a reference picture index and a motion vector corresponding to the reference picture list L0. In embodiment 7, if it is determined that the block applies triangular prediction, the motion data corresponding to the reference picture list L1 is not used to generate the second uni-predictive candidate.

[0270] FIG. 10 shows a flow chart of the seventh embodiment.

[0271] In an embodiment (embodiment 8) of the present disclosure, the following steps are followed to construct a merge list.

[0272] Step 1: Construct a motion candidate list (first list) containing motion information candidates with uni-prediction or bi-prediction.

[0273] The first list may be constructed according to the methods of ITU-T H.265 and VVC, see the above examples and disclosures about the merge list construction process of H.265 and VVC.

[0274] Step 2: Construct the second and third lists using the candidates in the first list as follows:

[0275] Step 2.1: Start with the first candidate in the first list.

[0276] Step 2.2: If the candidate is a uni-prediction candidate, add the candidate (motion information candidate) to the second list and the third list.

[0277] or Step 2.3: If the candidate is a bi-predictive candidate, two uni-predictive candidates are generated and one uni-predictive candidate is added to the second list and one uni-predictive candidate is added to the third list according to the following order: The first motion information candidate contains a motion vector and a reference picture index corresponding to the L0 reference picture list (the candidate is set as a uni-prediction candidate before inserting it into the second list). The second motion information candidate contains a motion vector and a reference picture index corresponding to the L1 reference picture list (the candidate is set as a uni-prediction candidate before inserting it into the third list).

[0278] Step 2.4: Proceed to the next candidate in the first list and continue with Step 2.2 or Step 2.3 until the specified amount of candidates have been collected in the second and third lists or until all candidates in the first list have been processed.

[0279] The first merge list, the second merge list, and the third merge list may be used in the inter prediction process of the current block.

[0280] In the example, when triangular prediction is applied to the current block, one candidate from the second list and one candidate from the third list are selected to perform triangular prediction, and one candidate is used in the prediction process of the first triangular portion and the other candidate is used in the prediction of the second triangular portion.

[0281] In another example, if the block size of the current block is less than or equal to a threshold (e.g., the threshold may be 16) or the block size of the current block is the smallest size predefined or signaled in the parameter set, one candidate from the second list is selected to perform inter prediction for the current block. In this example, when the size of the current block is small, bi-prediction is not allowed for the current block.

[0282] In another example, if a merge mode is applied to the current block and a triangular prediction mode is not applied to the current block, one candidate from the first list is selected to perform prediction of the current block, which is the same as the related process disclosed in ITU-T H.265 or VVC.

[0283] In the example, the first motion candidate list is a merge list.

[0284] It is noted that in a possible implementation, the candidate list may not be an independent list, since the candidate list for triangular (or lower block) prediction is derived from the candidate list for the merge mode. Candidates in the second candidate list may be represented by indicators pointing to candidates in the candidate list for the merge mode.

[0285] Embodiment 8 discloses a method for constructing two motion information candidate lists (a second list and a third list), where the second list and the third list include uni-prediction candidates.

[0286] If triangular prediction is not applied to the block, the first list is used in predicting the block. In the example, the first list is used for coding blocks that are indicated to apply a merge mode but are not indicated to apply a triangular prediction mode.

[0287] The second list and the third list are constructed based on the first list. When triangular prediction is applied to the block, motion information (or motion vector) candidates are selected from the second list and the third list. The second list and the third list include uni-predictive candidates, and the candidates may be applied to the first and second triangular portions of the block. In an example, when a triangular merge mode is applied to the block, two merge indexes are coded into the bitstream. The first merge index identifies which candidate from the second list is used for the first triangular portion of the block and which candidate from the third list is used for the second triangular portion of the block.

[0288] In another example, if the block size of the current block is less than or equal to a threshold (e.g., the threshold may be 16) or the block size of the current block is the smallest size predefined or signaled in the parameter set, one merge index is coded into the bitstream to identify which candidate from the second list is used to predict the block. If the block size of the current block is greater than a threshold (e.g., the threshold may be 16) or the block size of the current block is not the smallest size predefined or signaled in the parameter set, a merge index is coded into the bitstream to identify which candidate from the first list is used to predict the block.

[0289] In another example, if it is determined that the block does not apply triangular prediction, other conditions may be checked to determine whether the block uses the first motion candidate list. In one example, if it is determined that the block does not apply triangular prediction, it is further determined whether the block applies a merge mode. If the merge mode is applied, the first motion candidate list is used to predict the block, and if the merge mode is not applied, other methods of predicting the current block (e.g., intra prediction) may be applied.

[0290] According to embodiment 8, second and third motion candidate lists are constructed based on the first motion candidate list. The second and third lists may have the advantage of only including uni-predictive candidates and therefore not including unusable candidates (for example, bi-predictive candidates). Therefore, the indicator for signaling which candidate is used can be represented by fewer bits, which improves compression efficiency.

[0291] In an embodiment (Embodiment 9) of the present disclosure, the following steps are followed to construct a merge list.

[0292] Step 1: Construct a motion candidate list (first list) containing motion information candidates with uni-prediction or bi-prediction.

[0293] The first list may be constructed according to the methods of ITU-T H.265 and VVC, see the above examples and disclosures about the merge list construction process of H.265 and VVC.

[0294] Step 1.1: Initialize a counter with a positive integer value N (the value of the counter is set equal to N).

[0295] Step 2: Construct a second list using the candidates from the first list as follows:

[0296] Step 2.1: Start with the first candidate in the first list.

[0297] Step 2.2: If the candidate is a uni-prediction candidate, add the candidate (motion information candidate) to a second list.

[0298] or Step 2.3: If the candidate is a bi-predictive candidate, two uni-predictive candidates are generated according to the one bi-predictive candidate, and the two uni-predictive candidates are added to a second list in the following order: The first candidate contains a motion vector and a reference picture index corresponding to the L0 reference picture list: the motion vector is denoted mv_L0, and the POC value of the reference picture (calculated based on the reference picture index in list L0) is denoted POC_L0. The second candidate contains a motion vector and a reference picture index corresponding to the L1 reference picture list: the motion vector is denoted mv_L1, and the POC value of the reference picture (calculated based on the reference picture index in list L1) is denoted POC_L1. A second candidate is inserted into the second list if all of the following conditions are met: ◆The counter value is greater than 0. ◆ Either POC_L0 is not equal to POC_L1 or mv_L0 is not similar to mv_L1. If the value of the counter is equal to zero, then the second candidate is inserted into the second list. If the counter value is greater than zero, the counter value is decremented by one.

[0299] Step 2.4: Proceed to the next candidate in the first list and continue with Step 2.2 or Step 2.3 until the specified amount (number) of candidates have been collected in the second list or until all candidates in the first list have been processed.

[0300] The specified number of candidates may be a predefined value or a value indicated in the bitstream. In one particular implementation, the specified number is 5. In this case, candidates are added to the second list until 5 candidates are placed in the second list.

[0301] In one possible implementation, the value of N may be a predefined number equal to one.

[0302] According to embodiment 9, the number of motion vector comparison operations (given by the condition test "either POC_L0 is not equal to POC_L1 or mv_L0 is not similar to mv_L1" in the section above) is limited to a maximum value N. Since hardware implementations have certain timing constraints, reducing and limiting the number of motion vector comparison operations helps to improve the processing throughput of the hardware implementation.

[0303] According to embodiment 9, a motion vector comparison operation is required for the first N bi-predictive candidates in the first list. If N is equal to 1, the first bi-predictive candidate in the first list requires a motion vector comparison operation before the two generated uni-predictive candidates are inserted into the second list. After the first bi-predictive candidate in the first list is processed by step 2.3, the remaining bi-predictive candidates do not require a motion vector comparison operation.

[0304] Alternatively, the second merge list may be constructed by the following steps.

[0305] Step 1: Construct a motion candidate list (first list) containing motion information candidates with uni-prediction or bi-prediction.

[0306] The first list may be constructed according to the methods of ITU-T H.265 and VVC, see the above examples and disclosures about the merge list construction process of H.265 and VVC.

[0307] Step 1.1: Initialize a counter with a positive integer value N (the value of the counter is set equal to N).

[0308] Step 2: Construct a second list using the candidates from the first list as follows:

[0309] Step 2.1: Start with the first candidate in the first list.

[0310] Step 2.2: If the candidate is a uni-prediction candidate, add the candidate (motion information candidate) to a second list.

[0311] or Step 2.3: If the candidate is a bi-predictive candidate, two uni-predictive candidates are generated according to the one bi-predictive candidate, and the two uni-predictive candidates are added to a second list in the following order: The first candidate contains a motion vector and a reference picture index corresponding to the L0 reference picture list: the motion vector is denoted mv_L0, and the POC value of the reference picture (calculated based on the reference picture index in list L0) is denoted POC_L0. The second candidate contains a motion vector and a reference picture index corresponding to the L1 reference picture list: the motion vector is denoted mv_L1, and the POC value of the reference picture (calculated based on the reference picture index in list L1) is denoted POC_L1. A second candidate is inserted into the second list if all of the following conditions are met: ◆The counter value is greater than 0. ◆ Either POC_L0 is not equal to POC_L1 or mv_L0 is not similar to mv_L1. If the value of the counter is equal to zero, then the second candidate is inserted into the second list.

[0312] Step 2.4: If the counter value is greater than zero, the counter value is decremented by one.

[0313] Step 2.5: Proceed to the next candidate in the first list and continue with Step 2.2 or Step 2.3 until a specified amount of candidates have been collected in the second list or until all candidates in the first list have been processed.

[0314] The specified number of candidates may be a predefined value or a value indicated in the bitstream. In one particular implementation, the specified number is 5. In this case, candidates are added to the second list until 5 candidates are placed in the second list.

[0315] In one particular implementation, the value of N may be a predefined number equal to one.

[0316] According to an alternative form of embodiment 9, the number of motion vector comparison operations (described as the condition test “either POC_L0 is not equal to POC_L1 or mv_L0 is not similar to mv_L1” in the section above) is limited to a maximum value N. Because hardware implementations have certain timing constraints, reducing and limiting the number of motion vector comparison operations helps to improve the processing throughput of the hardware implementation.

[0317] According to an alternative embodiment of embodiment 9, a motion vector comparison operation is required for the first N candidates in the first list. If N is equal to 1, the first bi-predictive candidate in the first list requires a motion vector comparison operation if it is a bi-predictive candidate. After the first candidate in the first list is processed by step 2.3, the remaining bi-predictive candidates do not require a motion vector comparison operation.

[0318] In a first example, after the first bi-predictive candidate in the first list is processed (by generating two uni-predictive candidates and inserting them into the second list), the counter is decremented by 1. In a second example, after the first candidate in the first list is processed, regardless of whether it is a uni-predictive candidate or a bi-predictive candidate, the counter is decremented by 1.

[0319] The first merge list and the second merge list may be used in the inter-prediction process of the current block. Since the candidate list for triangular (or lower-order block) prediction is derived from the candidate list of the merge mode, it is noted that in a possible implementation, the candidate list may not be an independent list. The candidates in the second candidate list may be represented by an indicator pointing to the candidates in the candidate list of the merge mode.

[0320] In the example, when triangular prediction is applied to the current block, two candidates from the second list are selected to perform triangular prediction, and one candidate is used in the prediction process of the first triangular portion and the other candidate is used in the prediction of the second triangular portion.

[0321] In another example, if the block size of the current block is less than or equal to a threshold (e.g., the threshold may be 16) or the block size of the current block is the smallest size predefined or signaled in the parameter set, one motion information candidate from the second list is selected to perform inter prediction for the current block. In this example, when the size of the current block is small, bi-prediction is not allowed for the current block.

[0322] In another example, if a merge mode is applied to the current block and a triangular prediction mode is not applied to the current block, one candidate from the first list is selected to perform prediction of the current block, which is the same as the related process disclosed in ITU-T H.265 or VVC.

[0323] In the example, if POC_L0 is equal to POC_L1 and mv_L0 is the same as mv_L1, the second candidate in step 2.3 is not added to the second list.

[0324] In another example, if the reference picture index of the L0 portion is the same as the reference picture index of the L1 portion and if mv_L0 is identical to (or alternatively similar to) mv_L1, the second candidate of step 2.3 is not added to the second list.

[0325] In an example, the similarity of two motion vectors may be determined by the following inequality: -K< (MV1.x - MV2.x) < K and -K< (MV1.y - MV2.y) < K where MV1.x represents the x-component of the first motion vector (MV2.x has the same meaning as MV1.x), MV1.y represents the y-component (MV2.y has the same meaning as MV1.y), and K is a positive number. In this example, if both inequalities hold, then motion vector MV1 is considered to be similar to motion vector MV2.

[0326] In another example, similarity may be determined based on the following equation: (MV1.x >> N) - (MV2.x >> N) == K and (MV1.x >> N) - (MV2.x >> N) == K

[0327] where x>>y denotes an arithmetic right shift of the two's complement integer representation of x by y binary places. This function is defined only for non-negative integer values ​​of y. The bit shifted to the most significant bit (MSB) as a result of the right shift has a value equal to the MSB of x before the shift operation. "==" is a rational operation that is true when both sides of the operator are identical. In this example, motion vector MV1 is considered to be similar to motion vector MV2 if both equalities hold.

[0328] In the example, the first motion candidate list is a merge list.

[0329] In step 2.3, the second candidate (which is a uni-predictive candidate generated based on the L1 portion of the bi-predictive candidates in the first motion candidate list) is added to the second motion candidate list only if the second candidate is sufficiently different from the first candidate (which is a uni-predictive candidate generated based on the L0 portion of the bi-predictive candidates in the first motion candidate list).

[0330] When an L1 portion is similar (or identical) to an L0 portion, the L1 portion is not inserted into the second list, thereby increasing compression efficiency.

[0331] Embodiment 9 discloses a method for constructing a motion information candidate list (second list), where the second list includes uni-prediction candidates.

[0332] If triangular prediction is not applied to the block, the first list is used in predicting the block. In the example, the first list is used for coding blocks that are indicated to apply a merge mode but are not indicated to apply a triangular prediction mode.

[0333] The second list is constructed based on the first list. If triangular prediction is applied to the block, motion information (or motion vector) candidates are selected from the second list. The second list includes uni-predictive candidates, and the candidates may be applied to the first and second triangular portions of the block. In an example, if a triangular merge mode is applied to the block, two merge indexes are coded into the bitstream. The merge indexes identify which candidate from the second list is used for the first or second triangular portion of the block.

[0334] In another example, if the block size of the current block is less than or equal to a threshold (e.g., the threshold may be 16) or the block size of the current block is the smallest size predefined or signaled in the parameter set, one merge index is coded into the bitstream to identify which candidate from the second list is used to predict the block. If the block size of the current block is greater than a threshold (e.g., the threshold may be 16) or the block size of the current block is not the smallest size predefined or signaled in the parameter set, a merge index is coded into the bitstream to identify which candidate from the first list is used to predict the block.

[0335] In another example, if it is determined that the block does not apply triangular prediction, other conditions may be checked to determine whether the block uses the first motion candidate list. In one example, if it is determined that the block does not apply triangular prediction, it is further determined whether the block applies a merge mode. If the merge mode is applied, the first motion candidate list is used to predict the block, and if the merge mode is not applied, other methods of predicting the current block (e.g., intra prediction) may be applied.

[0336] According to embodiment 9, a second motion candidate list is constructed based on the first motion candidate list. The second list may have the advantage of only including uni-prediction candidates and therefore not including unusable candidates (for example, bi-prediction candidates). Therefore, the indicator for signaling which candidate is used can be represented by fewer bits, which improves compression efficiency.

[0337] In embodiments 1 to 9, aspects are described using the terms "first list" and "second list." It is noted that if a coding block is coded using a triangular or sub-block prediction mode, the motion information candidates in the second list are used to predict the coding block. The present disclosure may also be considered a modification to the rules for constructing the first list. Because the first list may include not only uni-predictive candidates but also bi-predictive candidates, the first list cannot be used in predicting a coding block predicted using triangular prediction (which requires that all selectable candidates must be uni-predictive candidates). Therefore, the present disclosure may be considered a modification to the list construction rules described, for example, in the ITU-T H.265 standard or the VVC draft standard. In fact, the disclosed aspects are applicable to any motion information list including uni-predictive candidates and bi-predictive candidates, and the objective of the present disclosure is to modify the list construction rules so that the resulting motion information candidate list includes only uni-predictive candidates. Therefore, the modified list construction rules can be applied to obtain motion information candidates that can be used to predict coding blocks that are predicted using triangular (or sub-block) prediction. In other words, given a set of rules for constructing a merge list that includes both uni-predictive and bi-predictive candidates, embodiments 1-9 describe the modification of the rules required to obtain a motion information candidate list that includes only uni-predictive candidates.

[0338] Example 1. A method of processing blocks according to a merge candidate list, comprising: constructing a first list according to the motion information of neighboring blocks of the current block; constructing a second list according to the first list; obtaining prediction information or block size information for the current block; using the first list or the second list to perform inter prediction of the current block according to prediction information or block size information of the current block; A method comprising:

[0339] Example 2. The method of example 1, wherein all candidates in the second list are uni-prediction candidates.

[0340] Example 3. The step of constructing a second list according to a first list comprises: generating two uni-predictive candidates according to one bi-predictive candidate of the first list; constructing a second list according to two uni-prediction candidates; The method of Example 1 or 2, including:

[0341] Example 4. The step of constructing a second list according to a first list comprises: generating one uni-predictive candidate according to one bi-predictive candidate of the first list; constructing a second list according to one uni-prediction candidate; The method of Example 1 or 2, including:

[0342] Example 5. The step of constructing a second list according to a first list comprises: generating two uni-predictive candidates according to one bi-predictive candidate of the first list; constructing a second list according to at least one uni-predictive candidate and two uni-predictive candidates of the first list; The method of Example 1 or 2, including:

[0343] Example 6. The step of constructing a second list according to a first list comprises: generating two uni-predictive candidates according to one bi-predictive candidate of the first list; determining a similarity between two uni-prediction candidates; constructing a second list depending on the results of the step of determining two uniprediction candidates and similarities; The method of Example 1 or 2, including:

[0344] Example 7. The step of constructing a second list according to a first list comprises: 7. The method of any one of Examples 1 to 6, comprising inserting at least one uni-predictive candidate of the first list into the second list by splitting the bi-predictive candidates of the first list into two uni-predictive candidates.

[0345] Example 8. The step of constructing a second list according to a first list comprises: 7. The method of any one of Examples 1 to 6, comprising inserting at least one uni-predictive candidate of the first list into the second list according to an order of the at least one uni-predictive candidate of the first list and by splitting the bi-predictive candidate of the first list into two uni-predictive candidates.

[0346] Example 9. The method is determining a similarity between two components of the first list of bi-prediction candidates; updating the first list according to the results of the similarity determining step; further comprising Correspondingly, the step of constructing a second list in response to the first list comprises: The method of any one of Examples 1 to 8, comprising constructing a second list in response to the updated first list.

[0347] Example 10. The method of any one of Examples 1 to 9, wherein the size of the second list is less than or equal to the size of the first list.

[0348] Example 11. The method of any one of Examples 1 to 9, wherein the size of the second list is determined according to the block size of the current block.

[0349] Example 12. The method of any one of Examples 1 to 9, wherein the size of the second list is determined according to the width or height of the current block.

[0350] Example 13. The step of using the first list or the second list to perform inter prediction according to prediction information or block size information of the current block includes: When triangular prediction (or lower-order block prediction) is applied to the current block, the second list is used to predict the current block; or 13. The method of any one of Examples 1 to 12, comprising using the first list to predict the current block when triangular prediction (or lower block prediction) is not applied to the current block.

[0351] Example 14. The step of using the first list or the second list to perform inter prediction according to prediction information or block size information of the current block, the second list is used to predict the current block when the block size of the current block is less than or equal to a threshold (e.g., the threshold may be 16) or the block size of the current block is the smallest size predefined or signaled in the parameter set; or,

[0033] Any one of Examples 1 to 13, including using the first list to predict the current block when the block size of the current block is greater than a threshold (e.g., the threshold may be 16) or the block size of the current block is not the smallest size predefined or signaled in the parameter set.

[0352] Example 15. An encoder (20) including processing circuitry for performing the method according to any one of examples 1 to 14.

[0353] Example 16. A decoder (30) comprising processing circuitry for performing the method according to any one of examples 1 to 14.

[0354] Example 17. A computer program product comprising program code for performing the method according to any one of Examples 1 to 14.

[0355] Example 18. A decoder comprising: one or more processors; a non-transitory computer-readable storage medium coupled to the processor and storing programming for execution by the processor, the programming, when executed by the processor, configuring the decoder to perform a method according to any one of Examples 1 to 14; and Including, a decoder.

[0356] Example 19. An encoder having: one or more processors; a non-transitory computer-readable storage medium coupled to the processor and storing programming for execution by the processor, the programming, when executed by the processor, configuring the encoder to perform a method according to any one of Examples 1 to 14; and Including, an encoder.

[0357] While embodiments of the present disclosure have been described primarily based on video coding, it should be noted that embodiments of coding system 10, encoder 20, and decoder 30 (and correspondingly, system 10), as well as other embodiments described herein, may also be configured for processing or coding of still pictures, i.e., processing or coding of individual pictures independent of any preceding or subsequent pictures, similar to video coding. Generally, when picture processing coding is limited to a single picture 17, only inter prediction units 244 (encoder) and 344 (decoder) may not be available. All other functions (also called tools or technologies) of the video encoder 20 and the video decoder 30, 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 filter 220, 320, and entropy coding 270, and entropy decoding 304, may be used equally for processing still pictures.

[0358] The following is a description of the application of the encoding and decoding methods shown in the above embodiments and the systems that use them.

[0359] 16 is a block diagram showing a content supply system 3100 for realizing a content distribution service. The content supply 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 includes, but is not limited to, WIFI, Ethernet, cable, wireless (3G / 4G / 5G), USB, or any type of combination thereof.

[0360] The capture device 3102 may generate data and encode the data according to the encoding method described in the above embodiment. Alternatively, the capture device 3102 may deliver 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 smart 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 described above. When the data includes video, a video encoder 20 included in the capture device 3102 may actually perform the video encoding process. When the data includes audio (i.e., voice), an audio encoder included in the capture device 3102 may actually perform the audio encoding process. In some practical scenarios, the capture device 3102 delivers 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. The capture device 3102 delivers the encoded audio data and the encoded video data separately to the terminal device 3106 .

[0361] In the content supply system 3100, the terminal device 3106 receives and plays the encoded data. The terminal device 3106 can be a device having data reception and restoration capabilities, such as a smartphone or smart 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, capable of decoding the above-mentioned encoded data. For example, the terminal device 3106 may include the above-mentioned destination device 14. When the encoded data includes video, the video decoder 30 included in the terminal device is prioritized to perform video decoding. When the encoded data includes audio, the audio decoder included in the terminal device is prioritized to perform audio decoding processing.

[0362] For terminal devices with a display, such as a smartphone or smart 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), or an in-vehicle device 3124, the terminal device can provide 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 contacted to receive and show the decoded data.

[0363] When each device in this system performs encoding or decoding, the picture encoding device or picture decoding device shown in the above embodiments may be used.

[0364] 17 is a diagram illustrating an example structure of a terminal device 3106. After the terminal device 3106 receives a stream from the capture device 3102, a protocol progression unit 3202 analyzes the transmission protocol of the stream. The protocol may include, 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 Messaging Protocol (RTMP), or any type of combination thereof.

[0365] After the protocol progression unit 3202 processes the stream, a stream file is generated. The file is output to the demultiplexing unit 3204. The demultiplexing unit 3204 may separate the multiplexed data into encoded audio data and encoded video data. As mentioned above, for some practical scenarios, 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 passing through the demultiplexing unit 3204.

[0366] The demultiplexing process generates a video elementary stream (ES), an audio ES, and optionally subtitles. The video decoder 3206, which includes the video decoder 30 described in the above embodiment, decodes the video ES using the decoding method shown in the above embodiment to generate video frames and supplies this data to the synchronization unit 3212. The audio decoder 3208 decodes the audio ES to generate audio frames and supplies this data to the synchronization unit 3212. Alternatively, the video frames may be stored in a buffer (not shown in FIG. 17) before being supplied to the synchronization unit 3212. Similarly, the audio frames may be stored in a buffer (not shown in FIG. 17) before being supplied to the synchronization unit 3212.

[0367] 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 may be coded in a syntax that uses timestamps for the presentation of the coded audio and visual data as well as timestamps for the delivery of the data stream itself.

[0368] If subtitles are included in the stream, the subtitle decoder 3210 decodes the subtitles, synchronizes the subtitles with the video and audio frames, and provides the video / audio / subtitles to the video / audio / subtitle display 3216.

[0369] The present invention is not limited to the above-mentioned system, and either the picture encoding device or the picture decoding device of the above-mentioned embodiments may be incorporated into other systems, for example, a system in an automobile.

[0370] For example, embodiments of the encoder 20 and decoder 30 and the functionality described herein in connection with, for example, 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. A computer-readable medium may include a computer-readable storage medium, which corresponds to a tangible medium such as a data storage medium, or a communication medium, which includes any medium that facilitates transfer of a computer program from one place to another, for example via a communication protocol. Thus, generally, a computer-readable medium may correspond to (1) a tangible computer-readable storage medium that is non-transitory or (2) a communication medium such as a signal or carrier wave. A data storage medium 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 a computer-readable medium.

[0371] By way of example, and not limitation, such computer-readable storage media may include RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, flash memory, or any other medium that 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 wave, and microwave, then the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio wave, 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 cover non-transitory, tangible storage media. As used herein, disk and disc include compact disc (CD), laser disc, optical disc, digital versatile disc (DVD), floppy disk, and Blu-ray disc, where disks typically reproduce data magnetically while discs reproduce data optically using a laser. Combinations of the above should also be included within the scope of computer-readable media.

[0372] 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, the term "processor," as used herein, may refer to any of the above 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 incorporated into a combined codec. Also, the techniques may be implemented entirely in one or more circuits or logic elements.

[0373] 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 perform the disclosed techniques, but do not necessarily require realization by different hardware units. Rather, as described above, the various units may be combined in a codec hardware unit or provided by a collection of interoperable hardware units including one or more processors as described above in conjunction with suitable software and / or firmware. [Explanation of symbols]

[0374] 10 Video coding system, coding system 12 Source Device 13 Encoded picture data, communication channel 14 Destination Device 16 Picture Source 17 Picture, Picture Data, Raw Picture, Raw Picture Data, Monochrome Picture, Color Picture, Current Picture 18 Preprocessor, preprocessing unit, picture preprocessor 19 Preprocessed Picture, Preprocessed Picture Data 20 Video Encoder, Encoder 21 Encoded picture data, encoded bitstream 22 Communication interface, communication unit 28 Communication interface, communication unit 30 decoder, video decoder 31 Decoded Picture Data, Decoded Picture 32 Post-processor, post-processing unit 33 Post-processed picture data, post-processed picture 34 Display Devices 46 Processing Circuit 100 Video Encoder 201 Input, input interface 203 Picture Block, Original Block, Current Block, Segmented Block, Current Picture Block 204 Residual Calculation Unit, Residual Calculation 205 Residual Block, Residual 206 Conversion Processing Unit, Conversion 207 Conversion Factor 208 Quantization Unit, Quantization 209 Quantized Coefficients, Quantized Transform Coefficients, Quantized Residual Coefficients 210 Inverse quantization unit, inverse quantization 211 Dequantized coefficients, dequantized residual coefficients 212 Inverse Transform Processing Unit, (Inverse) Transform 213 Reconstructed residual block, dequantized coefficients, transform block 214 Reconstruction Unit, Adder, Summer 215 reconstructed blocks 216 buffers 220 Loop filter unit, loop filter 221 filtered blocks, filtered reconstructed blocks 230 Decoded Picture Buffer (DPB) 231 decoded pictures 244 Inter Prediction Units 254 Intra prediction unit, Inter prediction unit, Intra prediction 260 Mode Selection Unit 262 Division Unit, Division 265 prediction block, predictor 266 Syntax Elements 270 Entropy Coding Unit, Entropy Coding 272 Output, Output Interface 304 Entropy Decoding Unit, Residual Calculation, Entropy Decoding 309 Quantized Coefficients 310 Inverse Quantization Unit, Inverse Quantization 311 Dequantized Coefficients, Transform Coefficients 312 Inverse Transform Processing Unit, (inverse) transformation, output 313 Reconstructed Residual Blocks 314 Reconstruction Unit, Summer, Adder 315 reconstructed blocks 320 Loop filter, loop filter unit, loop filtering unit 321 filtered blocks, decoded video blocks 330 Decoded Picture Buffer (DPB) 331 decoded pictures 344 Inter Prediction Unit 354 Intra prediction unit, Intra prediction 360 Mode Selection Unit 362 Division 365 predicted blocks 400 Video Coding Device 410 Incoming port, input port 420 Receiver Unit (Rx) 430 Processor, Logic Unit, Central Processing Unit (CPU) 440 Transmitter Unit (Tx) 450 outgoing and outgoing ports 460 memory 470 Coding Module 500 equipment 502 processor 504 memory 506 Data 508 Operating Systems 510 Application Program 512 Bus 514 Secondary Storage 518 Display 3100 Contents Supply System 3102 Capture Device 3104 Communication Links 3106 Terminal Device 3108 Smartphones, smart pads 3110 Computers, Laptops 3112 Network Video Recorder (NVR) / Digital Video Recorder (DVR) 3114 TV 3116 Set-top box (STB) 3118 Video Conference System 3120 Video Surveillance System 3122 Personal Digital Assistant (PDA) 3124 In-Vehicle Devices 3126 Display 3202 Protocol Progression Unit 3204 Demultiplexing Unit 3206 Video Decoder 3208 Audio Decoder 3210 Subtitle Decoder 3212 Synchronous Unit 3214 Video / Audio Display 3216 Video / Audio / Subtitle Display

Claims

1. 1. A method for processing blocks according to a merge candidate list, comprising: constructing a first list according to the motion information of neighboring blocks of the current block; obtaining prediction information for the current block; When the prediction information of the current block indicates that a lower-order block prediction is applied to the current block, obtaining uni-predictive candidates for the current block according to the first list; using the uni-prediction candidates for the current block to perform inter prediction of the current block; A method comprising:

2. The method of claim 1 , wherein the current block includes two sub-blocks, each sub-block corresponding to a uni-predictive candidate.

3. The method of claim 1 or 2, wherein one uni-predictive candidate is generated according to one bi-predictive candidate in the first list.

4. The method of claim 1 or 2, wherein two uni-predictive candidates are generated according to one bi-predictive candidate in the first list.

5. The method of claim 3 or 4, wherein one uni-predictive candidate is a first part of the bi-predictive candidates.

6. The method of claim 3 or 4, wherein one uni-predictive candidate is a second part of the bi-predictive candidates.

7. The method of claim 1 , wherein the lower-order block prediction is a triangular prediction.

8. generating the two uni-predictive candidates in response to the one bi-predictive candidate in the first list, The method of claim 4 , comprising determining a similarity between the two uni-predictive candidates.

9. 9. The method of claim 1, wherein the uni-predictive candidates are generated in response to the bi-predictive candidates of the first list based on an order of the candidates in the first list.

10. An encoder (20) including processing circuitry for carrying out the method of any one of claims 1 to 9.

11. A decoder (30) comprising processing circuitry for carrying out the method of any one of claims 1 to 9.

12. A computer program product comprising program code for carrying out the method according to any one of claims 1 to 9.

13. A decoder comprising: one or more processors; a non-transitory computer-readable storage medium coupled to the processor and storing programming for execution by the processor, the programming, when executed by the processor, configuring the decoder to perform the method of any one of claims 1 to 9; and A decoder, including:

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