Intra-frame prediction method, device, and computer-readable storage medium

Abstract

A method for performing intra-frame prediction of a current block of an image of a video sequence, comprising: determining whether a first flag indicates that the intra-frame prediction mode corresponding to the current block is a directional mode; and based on determining that the first flag indicates that the intra-frame prediction mode corresponding to the current block is a directional mode, determining the index of the intra-frame prediction mode in an allowed intra-frame prediction mode (AIPM) list, and using the intra-frame prediction mode corresponding to the determined index in the AIPM list to perform intra-frame prediction of the current block.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to U.S. Provisional Patent Application No. 62 / 970,505, filed in the U.S. Patent and Trademark Office on February 5, 2020, and U.S. Patent Application No. 17 / 094,923, filed on November 11, 2020, both of which are incorporated herein by reference in their entirety. Technical Field

[0003] Methods and apparatus consistent with the embodiments relate to video coding, and more particularly, to methods and apparatus for decoder-side intra-mode derivation and interaction between adaptive intra-prediction modes. Background Art

[0004] The video coding format VP9 supports 8 directional modes corresponding to angles from 45 degrees to 207 degrees. In order to exploit a wider range of spatial redundancy in directional textures, the video coding format AOMediaVideo 1 (AV1) extends the directional intra mode to a set of angles with a finer span. The original 8 angles are slightly changed and become nominal angles. These 8 nominal angles are named V_PRED, H_PRED, D45_PRED, D135_PRED, D113_PRED, D157_PRED, D203_PRED, and D67_PRED, as shown in the following example. Figure 1 As shown. For each nominal angle, there are 7 finer angles, so AV1 has a total of 56 directional angles. The predicted angle is represented by the sum of the nominal intra angle and the angle δ, where the angle δ is -3 to 3 times the 3-degree step size. In order to implement the directional prediction mode in AV1 in a common way, a unified directional predictor is used to implement all 56 directional intra prediction modes in AV1. The unified directional predictor projects each pixel to a reference sub-pixel position and interpolates the reference pixel through a two-tap bilinear filter. Summary of the Invention

[0005] According to an embodiment, a method for performing intra-frame prediction of a current block of an image of a video sequence is executed by at least one processor and includes: determining whether a first flag indicates that the intra-frame prediction mode corresponding to the current block is a directional mode; and based on determining that the first flag indicates that the intra-frame prediction mode corresponding to the current block is a directional mode, determining an index of the intra-frame prediction mode in an allowed intra-frame prediction mode (AIPM) list, and using the intra-frame prediction mode corresponding to the determined index in the AIPM list to perform intra-frame prediction of the current block.

[0006] According to an embodiment, an apparatus for performing intra-frame prediction of a current block of an image of a video sequence includes: at least one memory configured to store computer program code; and at least one processor configured to access the at least one memory and operate in accordance with the computer program code. The computer program code includes: first determination code configured to cause the at least one processor to determine whether a first flag indicates that the intra-frame prediction mode corresponding to the current block is a directional mode; second determination code configured to cause the at least one processor to determine an index of the intra-frame prediction mode in an allowed intra-frame prediction mode (AIPM) list based on determining that the first flag indicates that the intra-frame prediction mode corresponding to the current block is a directional mode; and first execution code configured to cause the at least one processor to perform intra-frame prediction of the current block using the intra-frame prediction mode corresponding to the determined index in the AIPM list based on determining that the first flag indicates that the intra-frame prediction mode corresponding to the current block is a directional mode.

[0007] According to an embodiment, a non-transitory computer-readable storage medium stores instructions that cause at least one processor to: determine whether a first flag indicates that an intra-frame prediction mode corresponding to a current block is a directional mode; and based on determining that the first flag indicates that the intra-frame prediction mode corresponding to the current block is a directional mode, determine an index of the intra-frame prediction mode in an allowed intra-frame prediction mode (AIPM) list, and use the intra-frame prediction mode corresponding to the determined index in the AIPM list to perform intra-frame prediction of the current block. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 Here is a diagram of the 8 nominal angles in AV1.

[0009] Figure 2 is a simplified block diagram of a communication system according to an embodiment.

[0010] Figure 3 is a diagram illustrating placement of a video encoder and a video decoder in a streaming environment according to an embodiment.

[0011] Figure 4 is a functional block diagram of a video decoder according to an embodiment.

[0012] Figure 5 is a functional block diagram of a video encoder according to an embodiment.

[0013] Figure 6A It is a diagram of the upper position, left position and upper left position of the PAETH pattern.

[0014] Figure 6B is a diagram of the recursive intra-frame filtering mode.

[0015] Figure 6C is a diagram illustrating selection of a template from a reconstruction area having T rows of pixels.

[0016] Figure 6D is a diagram showing prediction fusion obtained by weighted averaging two Histogram of Gradient (HoG) modes and a planar mode.

[0017] Figure 7 is a flowchart illustrating a method for performing intra prediction of a current block of an image of a video sequence according to an embodiment.

[0018] Figure 8 is a simplified block diagram of an apparatus for performing intra prediction of a current block of an image of a video sequence according to an embodiment.

[0019] Figure 9 is a diagram of a computer system suitable for implementing an embodiment. DETAILED DESCRIPTION

[0020] Figure 2 2 is a simplified block diagram of a communication system (200) according to an embodiment. The communication system (200) may include at least two terminals (210-220) interconnected via a network (250). For one-way data transmission, a first terminal (210) may encode video data at a local location for transmission to another terminal (220) via the network (250). The second terminal (220) may receive the encoded video data from the other terminal from the network (250), decode the encoded data, and display the recovered video data. One-way data transmission may be more common in applications such as media services.

[0021] Figure 2 A second pair of terminals (230, 240) is shown, configured to support bidirectional transmission of encoded video, which can occur, for example, during a video conference. For bidirectional data transmission, each terminal (230, 240) can encode captured video data at a local location for transmission to the other terminal via a network (250). Each terminal (230, 240) can also receive encoded video data transmitted by the other terminal, can decode the encoded data, and can display the recovered video data on a local display device.

[0022] exist Figure 2In the embodiment, the terminals (210-240) may be shown as servers, personal computers and smart phones, but the principles of the embodiments are not limited thereto. The embodiments are applicable to laptop computers, tablet computers, media players and / or dedicated video conferencing equipment. The network (250) represents any number of networks that transmit encoded video data between the terminals (210-240), including, for example, wired and / or wireless communication networks. The communication network (250) can exchange data in circuit switching and / or packet switching channels. Representative networks include telecommunications networks, local area networks, wide area networks and / or the Internet. For the purposes of this discussion, unless explained below, the architecture and topology of the network (250) may be irrelevant to the operation of the embodiments.

[0023] Figure 3 A diagram illustrating placement of a video encoder and video decoder in a streaming environment according to an embodiment. The disclosed subject matter is equally applicable to other video-enabled applications, including, for example, video conferencing, digital TV, storing compressed video on digital media including CDs, DVDs, memory sticks, etc.

[0024] The streaming system may include an acquisition subsystem (313) that may include a video source (301), such as a digital camera, that creates, for example, an uncompressed video sample stream (302). The sample stream (302), depicted as a thick line to emphasize the high amount of data compared to the encoded video bitstream, may be processed by an encoder (303) coupled to the camera (301). The encoder (303) may include hardware, software, or a combination of hardware and software to implement or implement various aspects of the disclosed subject matter as described in more detail below. The encoded video bitstream (304), depicted as a thin line to emphasize the lower amount of data compared to the sample stream, may be stored on a streaming server (305) for future use. One or more streaming clients (306, 308) may access the streaming server (305) to retrieve a copy (307, 309) of the encoded video bitstream (304). The client (306) may include a video decoder (310) that decodes an incoming copy (307) of an encoded video bitstream and produces an output video sample stream (311) that can be presented on a display (312) or another presentation device (not depicted). In some streaming systems, the video bitstreams (304, 307, 309) may be encoded according to certain video coding / compression standards. Examples of such standards include ITU-T Recommendation H.265. The video coding standard under development is informally referred to as Versatile Video Coding (VVC). The disclosed subject matter may be used in the context of VVC.

[0025] Figure 4is a functional block diagram of a video decoder (310) according to an embodiment.

[0026] A receiver (410) may receive one or more encoded video sequences to be decoded by a decoder (310); in the same or another embodiment, one encoded video sequence is received at a time, wherein the decoding of each encoded video sequence is independent of the decoding of the other encoded video sequences. The encoded video sequence may be received from a channel (412), which may be a hardware / software link to a storage device storing the encoded video data. The receiver (410) may receive the encoded video data and other data, such as encoded audio data and / or auxiliary data streams, which may be forwarded to their respective consuming entities (not depicted). The receiver (410) may separate the encoded video sequence from the other data. To prevent network jitter, a buffer memory (415) may be coupled between the receiver (410) and an entropy decoder / parser (420) (hereinafter referred to as the "parser"). When the receiver (410) receives data from a store / forward device with sufficient bandwidth and controllability or from an isochronous network, the buffer memory (415) may not be needed or may be made smaller. For best-effort use on a traffic packet network such as the Internet, a cache (415) may be required, which may be relatively large and advantageously have an adaptive size.

[0027] The video decoder (310) may include a parser (420) to reconstruct symbols (421) from an entropy-coded video sequence. These symbols may include information for managing the operation of the decoder (310) and potentially information for controlling a presentation device (312) (e.g., a display) that is not an integral part of the decoder but may be coupled to the decoder, such as Figure 4. The control information for the presentation device may be in the form of a parameter set fragment (not depicted) of Supplemental Enhancement Information (SEI message) or Video Usability Information (VUI). The parser (420) may parse / entropy decode the received coded video sequence. The coding of the coded video sequence may be performed according to a video coding technique or standard and may follow various principles known to those skilled in the art, including variable length coding, Huffman coding, arithmetic coding with or without context sensitivity, and the like. The parser (420) may extract a subgroup parameter set for at least one subgroup of the subgroups of pixels in the video decoder from the coded video sequence based on at least one parameter corresponding to the group. The subgroup may include a Group of Pictures (GOP), a picture, a tile, a slice, a macroblock, a Coding Unit (CU), a block, a Transform Unit (TU), a Prediction Unit (PU), and the like. The entropy decoder / parser may also extract information from the encoded video sequence, such as transform coefficients, quantizer parameter (QP) values, motion vectors, and so on.

[0028] The parser (420) may perform entropy decoding / parsing operations on a video sequence received from the buffer (415) to create symbols (421). The parser (420) may receive encoded data and selectively decode specific symbols (421). In addition, the parser (420) may determine whether to provide the specific symbols (421) to the motion compensation prediction unit (453), the scaler / inverse transform unit (451), the intra prediction unit (452), or the loop filter unit (454).

[0029] Depending on the type of coded video picture or portion of a coded video picture (e.g., inter-frame and intra-frame pictures, inter-frame blocks and intra-frame blocks), and other factors, the reconstruction of the symbol (421) may involve multiple different units. Which units are involved and how they are involved can be controlled by subgroup control information parsed from the coded video sequence by the parser (420). For clarity, the flow of such subgroup control information between the parser (420) and the various units described below is not depicted.

[0030] In addition to the functional blocks already mentioned, the decoder (310) can be conceptually subdivided into several functional units as described below. In a practical implementation operating under commercial constraints, many of these units interact closely with each other and may be at least partially integrated with each other. However, for the purposes of describing the disclosed subject matter, the conceptual subdivision into the following functional units is appropriate.

[0031] The first unit is a scaler / inverse transform unit (451). The scaler / inverse transform unit (451) receives quantized transform coefficients as symbols (421) from the parser (420) along with control information, including which transform method to use, block size, quantization factor, quantization scaling matrix, etc. The scaler / inverse transform unit (451) may output a block comprising sample values, which may be input to an aggregator (455).

[0032] In some cases, the output samples of the scaler / inverse transform unit (451) may belong to an intra-coded block; that is, a block that does not use predictive information from a previously reconstructed image, but may use predictive information from a previously reconstructed portion of the current image. Such predictive information may be provided by an intra-image prediction unit (452). In some cases, the intra-image prediction unit (452) uses surrounding reconstructed information extracted from the current (partially reconstructed) image (456) to generate a block of the same size and shape as the block being reconstructed. In some cases, the aggregator (455) adds the prediction information generated by the intra-frame prediction unit (452) to the output sample information provided by the scaler / inverse transform unit (451) on a per-sample basis.

[0033] In other cases, the output samples of the scaler / inverse transform unit (451) may belong to an inter-frame coded and potentially motion compensated block. In this case, the motion compensated prediction unit (453) may access the reference picture memory (457) to extract samples for prediction. After the extracted samples are motion compensated according to the symbols (421) belonging to the block, these samples may be added to the output of the scaler / inverse transform unit (in this case referred to as residual samples or residual signal) by the aggregator (455) to generate output sample information. The retrieval of the prediction samples by the motion compensation unit from the address in the reference picture memory may be controlled by a motion vector, and the motion vector is provided to the motion compensation unit in the form of a symbol (421) that may have, for example, X, Y and reference picture components. Motion compensation may also include interpolation of sample values ​​extracted from the reference picture memory when using sub-sample accurate motion vectors, motion vector prediction mechanisms, etc.

[0034] The output samples of the aggregator (455) may be subjected to various loop filtering techniques in a loop filter unit (454). The video compression techniques may include in-loop filtering techniques controlled by parameters included in the coded video bitstream and available to the loop filter unit (454) as symbols (421) from the parser (420), however, the video compression techniques may also be responsive to meta-information obtained during decoding of a previous (in decoding order) portion of a coded picture or coded video sequence, as well as to previously reconstructed and loop filtered sample values.

[0035] The output of the loop filter unit (454) may be a sample stream that may be output to a rendering device (312) and stored in a reference picture memory (456) for subsequent inter-frame picture prediction.

[0036] Once fully reconstructed, certain coded pictures can be used as reference pictures for future prediction. Once a coded picture is fully reconstructed and the coded picture is identified as a reference picture (e.g., by a parser (420)), the current reference picture (456) can become part of the reference picture cache (457) and new current picture memory can be reallocated before starting to reconstruct a subsequent coded picture.

[0037] The video decoder (310) may perform decoding operations according to a predetermined video compression technique, such as that documented in the ITU-T Recommendation H.265 standard. The coded video sequence may conform to the syntax specified by the video compression technique or standard used, in the sense that the coded video sequence follows the syntax of the video compression technique or standard, as specified in a video compression technique document or standard, and in particular as specified in a profile of the video compression technique document or standard. Conformance may also require that the complexity of the coded video sequence be within a range defined by the hierarchy of the video compression technique or standard. In some cases, the hierarchy limits the maximum picture size, maximum frame rate, maximum reconstruction sampling rate (measured in, for example, megasamples per second), maximum reference picture size, etc. In some cases, the limits set by the hierarchy may be further defined by a Hypothetical Reference Decoder (HRD) specification and metadata for HRD buffer management signaled in the coded video sequence.

[0038] In an embodiment, the receiver (410) may receive additional (redundant) data along with the encoded video. The additional data may be included as part of the encoded video sequence. The additional data may be used by the video decoder (310) to properly decode the data and / or more accurately reconstruct the original video data. The additional data may be in the form of, for example, temporal, spatial, or signal-to-noise ratio (SNR) enhancement layers, redundant slices, redundant pictures, forward error correction codes, and the like.

[0039] Figure 5 is a functional block diagram of a video encoder (303) according to an embodiment.

[0040] The encoder (303) may receive video samples from a video source (301) (not part of the encoder) that may capture video images to be encoded by the encoder (303).

[0041] The video source (301) may provide a source video sequence in the form of a digital video sample stream to be encoded by the encoder (303), the digital video sample stream may have any suitable bit depth (e.g., 8-bit, 10-bit, 12-bit, ...), any color space (e.g., BT.601 Y CrCB, RGB, ...), and any suitable sampling structure (e.g., Y CrCb 4:2:0, Y CrCb 4:4:4). In a media service system, the video source (301) may be a storage device storing previously prepared videos. In a video conferencing system, the video source (301) may be a camera that captures local image information as a video sequence. The video data may be provided as a plurality of individual images that are given motion when viewed sequentially. The images themselves may be constructed as a spatial array of pixels, where each pixel may include one or more samples depending on the sampling structure, color space, etc. used. The relationship between pixels and samples may be readily understood by those skilled in the art. The following description focuses on samples.

[0042] According to an embodiment, the encoder (303) can encode and compress the images of the source video sequence into an encoded video sequence (543) in real time or under any other time constraints required by the application. Implementing the appropriate encoding speed is a function of the controller (550). The controller controls other functional units as described below and is functionally coupled to these units. For the sake of clarity, the coupling is not depicted in the figure. The parameters set by the controller may include rate control related parameters (picture skipping, quantizer, lambda value of rate distortion optimization technique, etc.), picture size, group of pictures (GOP) layout, maximum motion vector search range, etc. Those skilled in the art can easily recognize the other functions of the controller (550) because these functions relate to the video encoder (303) optimized for a certain system design.

[0043] Some video encoders operate in what one skilled in the art will readily recognize as a "coding loop." As a simplified description, the coding loop may include an encoder (530) (hereinafter referred to as the "source encoder," which is responsible for creating symbols based on an input image to be encoded and a reference image) and a (local) decoder (533) embedded within the encoder (303), which reconstructs the symbols to create sample data in a manner similar to how a (remote) decoder can also create sample data (since, in the video compression techniques contemplated by the disclosed subject matter, any compression between the symbols and the encoded video bitstream is lossless). The reconstructed sample stream is input to a reference image memory (534). Since decoding the symbol stream produces bit-accurate results that are independent of the decoder's location (local or remote), the contents of the reference image buffer also correspond bit-accurately between the local encoder and the remote encoder. In other words, the reference image samples "seen" by the prediction portion of the encoder are exactly the same sample values ​​that the decoder will "see" when using prediction during decoding. Those skilled in the art are aware of this basic principle of reference image synchronization (and the resulting drift when synchronization cannot be maintained, for example, due to channel errors).

[0044] The operation of the "local" decoder (533) can be combined with the Figure 4 The operation of the "remote" decoder (310) is identical to that described in detail. However, additional brief reference is made to Figure 4 , when symbols are available and the entropy encoder (545) and parser (420) can losslessly encode / decode the symbols into an encoded video sequence, the entropy decoding portion of the decoder (310), including the channel (412), receiver (410), buffer (415) and parser (420), may not be fully implemented in the local decoder (533).

[0045] At this point, it can be observed that any decoder technique other than parsing / entropy decoding present in the decoder must also be present in essentially the same functional form in the corresponding encoder. The description of the encoder technique can be simplified because the encoder technique is the inverse of the decoder technique described comprehensively. A more detailed description is required only in certain areas and is provided below.

[0046] As part of its operation, the source encoder (530) may perform motion-compensated predictive coding, in which an input frame is predictively encoded with reference to one or more previously encoded frames in a video sequence designated as "reference frames." In this manner, the encoding engine (532) encodes the differences between pixel blocks of an input frame and pixel blocks of a reference frame that may be selected as a prediction reference for the input frame.

[0047] The local video decoder (533) can decode the encoded video data of the frame that can be designated as the reference frame based on the symbol created by the source encoder (530). The operation of the encoding engine (532) can advantageously be a lossy process. When the encoded video data can be decoded at the video decoder ( Figure 4 When decoded at a remote location (not shown), the reconstructed video sequence may typically be a copy of the source video sequence, but with some errors. The local video decoder (533) replicates the decoding process that the video decoder would perform on the reference frame and may cause the reconstructed reference frame to be stored in the reference picture cache (534). In this way, the encoder (303) may locally store a copy of the reconstructed reference frame that has common content (absent transmission errors) with the reconstructed reference frame that will be obtained by the remote video decoder.

[0048] The predictor (535) may perform a prediction search for the encoding engine (532). That is, for a new frame to be encoded, the predictor (535) may search the reference image memory (534) for sample data (as candidate reference pixel blocks) or certain metadata, such as reference image motion vectors, block shapes, etc., that may serve as suitable prediction references for the new frame. The predictor (535) may operate on a pixel block-by-pixel block basis to find a suitable prediction reference. In some cases, as determined by the search results obtained by the predictor (535), the input image may have prediction references taken from multiple reference images stored in the reference image memory (534).

[0049] The controller (550) can manage encoding operations of the video encoder (530), including, for example, setting parameters and subgroup parameters for encoding video data.

[0050] The outputs of all the above functional units may be entropy coded in an entropy encoder (545). The entropy encoder performs lossless compression on the symbols generated by the various functional units according to techniques known to those skilled in the art, such as Huffman coding, variable length coding, arithmetic coding, etc., thereby transforming the symbols into a coded video sequence.

[0051] The transmitter (540) can buffer the encoded video sequence created by the entropy encoder (545) in preparation for transmission over a communication channel (560), which can be a hardware / software link to a storage device that can store the encoded video data. The transmitter (540) can combine the encoded video data from the video encoder (530) with other data to be transmitted, such as encoded audio data and / or an auxiliary data stream (source not shown).

[0052] The controller (550) may manage the operation of the encoder (303). During encoding, the controller (550) may assign a certain coded picture type to each coded picture, but this may affect the encoding techniques that can be applied to the corresponding picture. For example, a picture may generally be assigned to any of the following frame types:

[0053] An intra picture (I picture) is a picture that can be encoded and decoded without using any other frame in the sequence as a prediction source. Some video codecs allow for different types of intra pictures, including, for example, Independent Decoder Refresh (IDR) pictures. Those skilled in the art are aware of the variations of I pictures and their corresponding applications and characteristics.

[0054] A predictive picture (P picture) may be a picture that can be encoded and decoded using intra prediction or inter prediction, which uses at most one motion vector and a reference index to predict sample values ​​for each block.

[0055] Bidirectionally predictive pictures (B pictures) can be encoded and decoded using intra-frame prediction or inter-frame prediction, which uses up to two motion vectors and reference indices to predict the sample values ​​of each block. Similarly, multiple predictive pictures can use more than two reference pictures and associated metadata to reconstruct a single block.

[0056] A source picture is typically spatially subdivided into blocks of samples (e.g., blocks of 4×4, 8×8, 4×8, or 16×16 samples) and coded block by block. These blocks can be predictively coded with reference to other (already coded) blocks, determined by the coding allocation applied to the block's corresponding picture. For example, a block of an I picture can be non-predictively coded, or the block can be predictively coded (spatial prediction or intra prediction) with reference to already coded blocks of the same picture. Pixel blocks of a P picture can be non-predictively coded using spatial prediction with reference to a previously coded reference picture or using temporal prediction. Blocks of a B picture can be non-predictively coded using spatial prediction with reference to one or two previously coded reference pictures or using temporal prediction.

[0057] The video encoder (303) may perform encoding operations according to a predetermined video coding technique or standard, such as ITU-T Recommendation H.265, or the next generation video coding (Versatile Video Coding, VVC) H.266. In operation, the video encoder (303) may perform various compression operations, including predictive coding operations that exploit temporal and spatial redundancy in the input video sequence. Thus, the encoded video data may conform to the syntax specified by the video coding technique or standard used.

[0058] In an embodiment, the transmitter (540) may transmit additional data along with the encoded video. The video encoder (530) may include such data as part of the encoded video sequence. The additional data may include temporal, spatial, and / or SNR enhancement layers, redundant pictures and slices, or other forms of redundant data, such as Supplementary Enhancement Information (SEI) messages or Visual Usability Information (VUI) parameter set segments.

[0059] In AV1, there are five non-directional smooth intra prediction modes: DC, PAETH, SMOOTH, SMOOTH_V, and SMOOTH_H. For DC prediction, the average of the left and upper neighboring samples is used as the prediction value of the block to be predicted. For the PAETH predictor, the upper reference sample, the left reference sample, and the upper left reference sample are first extracted, and then the value closest to (upper + left - upper left) is set as the predictor for the pixel to be predicted. Figure 6A The positions of the top sample, left sample, and top-left sample of a pixel in the current block are shown.For SMOOTH mode, SMOOTH_V mode, and SMOOTH_H mode, blocks are predicted using quadratic interpolation in the vertical or horizontal direction or an average of both directions.

[0060] In order to capture the attenuated spatial correlation through reference on the edge, a filter intra mode is designed for the luma block. AV1 defines five filter intra modes, each of which is represented by a set of eight 7-tap filters that reflect the correlation between a pixel in a 4×2 patch and its 7 neighbors adjacent to the patch. In other words, the weighting factor of the 7-tap filter depends on the position. Take an 8×8 block as an example; the block is divided into 8 4×2 patches, such as Figure 6B These patches are shown in Figure 6B In the example, B0, B1, B2, B3, B4, B5, B6, and B7 are represented in the image. For each tile, its seven neighbors, represented by R0 to R6, are used to predict the pixels in the current tile. For tile B0, all neighbors have been reconstructed. However, for other tiles, not all neighbors are reconstructed, so the predicted values ​​of the nearest neighbors are used as a reference. For example, not all neighbors of tile B7 are reconstructed, so the predicted samples of the neighbors (i.e., B5 and B6) are used instead.

[0061] Chroma from Luma (CfL) is a pure chroma intra predictor that models chroma pixels as linear functions that consistently reconstruct luma pixels. The CfL prediction is expressed as follows:

[0062] CfL(α)=α×L AC+DC (1),

[0063] Among them, L AC represents the AC contribution of the luma component, α represents the parameters of the linear model, and DC represents the DC contribution of the chroma components. Specifically, the reconstructed luma pixels are downsampled to the chroma resolution and then the average value is subtracted to form the AC contribution. To approximate the chroma AC components from the AC contributions, instead of requiring the decoder to calculate the scaling parameters as in some methods, AV1CfL determines the parameter α based on the original chroma pixels and signals α in the bitstream. This reduces decoder complexity and produces more accurate predictions. For the DC contributions of the chroma components, they are calculated using the DC mode, which is sufficient for most chroma content and has a mature and fast implementation.

[0064] A proposal is made to improve intra mode coding for the next generation video coding (VVC) standard. For example, two intra prediction mode sets may be defined for each block, which are named allowed intra prediction mode set (AIPM, also named adaptive intra prediction mode) and forbidden intra prediction mode set (DIPM). The AIPM is defined as a mode set whose modes can be used for intra prediction of the current block, and the DIPM is defined as a mode set whose modes cannot be signaled or used for intra prediction of the current block. For each block, modes in the two mode sets are derived based on the intra prediction modes of neighboring blocks. The neighboring modes are included in the AIPM set but not in the DIPM set. The number of modes included in the AIPM set and the DIPM set is predefined and fixed for all blocks. When the size of the AIPM set is S and the number of intra prediction modes derived from the neighboring modes is less than S, the AIPM set is populated with default modes.

[0065] When AIPM is applied to AV1, all nominal angles are always included in AIPM regardless of the block size of the current block and the prediction mode of neighboring blocks.

[0066] In the decoder-side intra mode derivation (DIMD) process, intra prediction modes are derived based on previously encoded / decoded pixels and are done in the same way on both the encoder and decoder sides. Therefore, signaling of the intra prediction mode index is avoided during the DIMD process. This process defines a new coding mode called DIMD. A flag is signaled in the bitstream to indicate whether DIMD mode is selected. Decoder-side intra mode derivation, also known as derived intra mode, has been implemented in the proposal using the flag CONFIG_DERIVED_INTRA_MODE.

[0067] There are two main steps employed in the DIMD process, as described in detail below.

[0068] To implicitly derive the intra prediction mode (IPM) of the DIMD block, texture gradient analysis is performed on both the encoder and decoder sides. The process starts with an empty HoG with 65 entries corresponding to the number of angular modes. The magnitudes of these entries are determined during texture gradient analysis.

[0069] In the first step, DIMD selects T = 3 columns and 3 rows of templates from the left and top of the current block, respectively, as Figure 6C This region will be used as a reference for gradient-based IPM derivation.

[0070] In the second step, horizontal and vertical Sobel filters are applied to all 3×3 window positions centered on the pixels in the template centerline, as Figure 6C At each window position, the Sobel filter calculates the pure horizontal and vertical intensities as G hor and G ver The texture angle of the window is then calculated as:

[0071] angle=arctan(G ver / G hor ) (2),

[0072] This angle can be converted into one of 65 angle IPMs. Once the IPM index of the current window is derived as idx, the magnitude of its entry in HoG[idx] is updated by adding the following:

[0073] ampl=|G hor |+|G ver | (3).

[0074] Figure 6C Part (c) shows an example of the HoG calculated after applying the above operation to all pixel positions in the template.

[0075] This process is not required if only a single IPM corresponding to the highest peak of the HoG is used.

[0076] Otherwise, if more than one IPM is derived from the DIMD process, the prediction fusion process may be used.

[0077] The prediction fusion is calculated by taking a weighted average of multiple predictors. Figure 6DAn example of the fusion algorithm is shown. It can be seen that the two IPMs corresponding to the three highest peaks of HoG are detected as M1 and M2. The third IPM is fixed to the planar mode. After applying pixel prediction through these three IPMs and obtaining Pred1, Pred2 and Pred3, their fusion is calculated by the weighted average of the above three predictors. In one example, the weight of the planar mode is fixed to 21 / 64 (~1 / 3). The remaining weight of 43 / 64 (~2 / 3) is then shared between the two HoG IPMs, and the weight is proportional to the amplitude of the HoG bar.

[0078] In detail, the first weight ω1, the second weight ω2, and the third weight ω3 can be expressed as follows:

[0079]

[0080] and

[0081]

[0082] Therefore, the predictor block can be represented as follows:

[0083]

[0084] DIMD uses neighboring samples of the current block to derive one or more angular IPMs and assigns shorter codewords to these derived IPMs. AIPM uses neighboring IPMs to derive a selected IPM list and assigns shorter codewords to these IPMs. Both methods use neighboring information to optimize the signaling of the current block's IPMs. However, there is no solution for combining these two methods.

[0085] Embodiments of methods and apparatus for decoder-side intra mode derivation and interaction between adaptive intra prediction modes are described herein.

[0086] In this detailed description, a mode is called an angular mode or a directional mode if it is not a smooth mode or generates prediction samples according to a given prediction direction. DIMD is a general term used when a process uses neighboring reconstructed samples to derive an intra prediction mode.

[0087] In an embodiment, for each block, there are two intra prediction mode sets, which are respectively referred to as AIPM set and DIPM set. All non-directional modes are always included in the AIPM set, regardless of the block size of the current block and the prediction modes of neighboring blocks.

[0088] In an embodiment, all non-directional smooth intra prediction modes in AV1 are always inserted first into the AIPM set, regardless of the intra prediction modes of neighboring blocks.

[0089] In an embodiment, the DC mode, PAETH mode, SMOOTH mode, SMOOTH_V mode, and SMOOTH_H mode are always included first in the AIPM set regardless of the intra prediction mode of the neighboring blocks.

[0090] In an embodiment, the patterns included in the AIPM set can be divided into K levels, where K is a positive integer, such as 2, 3, or 4. For the first level, the number of patterns is equal to the number of non-directional patterns. For other levels, the number of patterns is equal to a power of 2, such as 2 L , L is a positive integer greater than 1. For example, the number of patterns in the AIPM set may be S, and the AIPM set may have 3 levels. S is equal to K+2 L +2 M , where the pattern with an index less than K in the AIPM set is called a first-level pattern, and the pattern with an index greater than or equal to K but less than K+2 in the AIPM set is called a first-level pattern. L The mode of is called the second level mode, and so on. In an embodiment, all non-directional IPMs are placed in the first level of the AIPM set.

[0091] In an embodiment, only directional IPMs are included in the AIPM list, and the number of modes in the AIPM is set equal to a power of 2 or a sum of multiples of a power of 2.

[0092] In an embodiment, for signaling intra prediction modes, a flag is signaled to indicate whether the current block is in directional mode. If so, a second flag is signaled to indicate the index of the current mode in the AIPM list. Otherwise, a second flag is signaled to indicate which non-directional mode the current mode is.

[0093] In an embodiment, for signaling intra-prediction modes, a flag is signaled to indicate whether the current block is in directional mode. If the current block is in directional mode, a second flag is signaled to indicate whether the current mode is DIMD mode. If the current mode is not DIMD mode, a third flag is signaled to indicate the index of the current mode in the AIPM list. Otherwise, if the current mode is DIMD mode, the third flag is avoided and the IPM for the current block is derived from the decoder side. Otherwise, if the current mode is not directional IPM, a second flag is signaled to indicate which non-directional mode the current mode is.

[0094] In an embodiment, an IPM derived from a DIMD process is always inserted into the AIPM list. In an embodiment, an IPM derived from a DIMD process is always inserted first into the AIPM list and is placed in the first level of the AIPM list.

[0095] In an embodiment, the AIPM scheme is applied only to the luma component, and the DIMD scheme is applied only to the chroma components.

[0096] Figure 7 is a flow chart illustrating a method (700) for performing intra prediction of a current block of an image of a video sequence according to an embodiment. In some implementations, Figure 7 One or more processing blocks of may be performed by the decoder (310). In some implementations, Figure 7 One or more processing blocks of may be performed by another device or group of devices (eg, encoder (303)) separate from or including the decoder (310).

[0097] refer to Figure 7 , in a first block (710), the method (700) includes determining whether a first flag indicates that an intra-prediction mode corresponding to a current block is a directional mode.

[0098] Based on determining that the first flag indicates that the intra-frame prediction mode corresponding to the current block is a directional mode (710-yes), in the second block (720), the method (700) includes: determining whether the second flag indicates that the intra-frame prediction mode is a decoder-side intra-frame mode derivation (DIMD) mode.

[0099] Based on determining that the second flag does not indicate that the intra-frame prediction mode corresponding to the current block is the DIMD mode (720-No), in the third block (730), the method (700) includes: determining an index of the intra-frame prediction mode in the allowed intra-frame prediction mode (AIPM) list, and in the fourth block (740), the method (700) includes: using the intra-frame prediction mode corresponding to the determined index in the AIPM list to perform intra-frame prediction of the current block.

[0100] Based on determining that the second flag indicates that the intra-frame prediction mode corresponding to the current block is DIMD mode (720-yes), in the fifth block (750), the method (700) includes: performing DIMD to determine the intra-frame prediction mode, and continuing in the fourth block (740), wherein the method (700) includes: using the determined intra-frame prediction mode to perform intra-frame prediction of the current block.

[0101] Based on determining that the first flag does not indicate that the intra-frame prediction mode corresponding to the current block is a directional mode (710-No), in the sixth block (760), the method (700) includes: determining the intra-frame prediction mode to be one of a plurality of non-directional modes, and continuing to the fourth block (740), wherein the method (700) includes: performing intra-frame prediction of the current block using the determined intra-frame prediction mode.

[0102] The method (700) may further include first inserting the intra prediction mode determined by performing DIMD into the first level of the AIPM list.

[0103] The method (700) may further include performing intra prediction of the luma component of the current block using at least one intra prediction mode in the AIPM list.

[0104] The method (700) may further include performing intra prediction of the chroma component of the current block using the intra prediction mode determined by performing DIMD.

[0105] The AIPM list may include only directional patterns, and the number of directional patterns included in the AIPM list may be equal to a power of 2 or a sum of multiples of the power of 2.

[0106] Although Figure 7 Exemplary blocks of the method (700) are shown, but in some implementations, the method (700) may include additional blocks, fewer blocks, different blocks, or different blocks. Figure 7 The blocks shown are blocks arranged differently. Additionally or alternatively, two or more blocks of the method (700) may be performed in parallel.

[0107] Figure 8 is a simplified block diagram of an apparatus (800) for performing intra prediction of a current block of an image of a video sequence according to an embodiment.

[0108] refer to Figure 8 , the device (800) includes a first determination code (805), a second determination code (810), a third determination code (815), a first execution code (820), a second execution code (825) and a fourth determination code (830).

[0109] The first determination code (805) is configured to cause at least one processor to determine whether the first flag indicates that the intra prediction mode corresponding to the current block is a directional mode.

[0110] The third determining code (815) is configured to cause the at least one processor to determine whether the second flag indicates that the intra prediction mode corresponding to the current block is a directional mode based on determining that the first flag indicates that the intra prediction mode corresponding to the current block is a directional mode.

[0111] The second determining code (810) is configured to cause the at least one processor to determine an index of the intra prediction mode in an allowed intra prediction mode (AIPM) list based on determining that the second flag does not indicate that the intra prediction mode corresponding to the current block is the DIMD mode.

[0112] The first execution code (820) is configured to cause at least one processor to perform intra-frame prediction of the current block using the intra-frame prediction mode corresponding to the determined index in the AIPM list based on determining that the second flag does not indicate that the intra-frame prediction mode corresponding to the current block is the DIMD mode.

[0113] The second execution code (825) is configured to cause the at least one processor to perform DIMD to determine the intra prediction mode based on determining that the second flag indicates that the intra prediction mode corresponding to the current block is the DIMD mode.

[0114] The first execution code (820) is further configured to cause the at least one processor to perform intra prediction of the current block using the determined intra prediction mode based on determining that the second flag indicates that the intra prediction mode corresponding to the current block is the DIMD mode.

[0115] The fourth determining code (830) is configured to cause the at least one processor to determine the intra prediction mode to be one of the plurality of non-directional modes based on determining that the first flag does not indicate that the intra prediction mode corresponding to the current block is the directional mode.

[0116] The first execution code (820) is further configured to cause the at least one processor to perform intra prediction of the current block using the determined intra prediction mode based on determining that the first flag does not indicate that the intra prediction mode corresponding to the current block is a directional mode.

[0117] The apparatus (800) may further include inserting code configured to cause the at least one processor to first insert the intra prediction mode determined by performing the DIMD into a first level of the AIPM list.

[0118] The apparatus (800) may further include a third execution code configured to cause the at least one processor to perform intra prediction of the luma component of the current block using at least one intra prediction mode in the AIPM list.

[0119] The third execution code may be further configured to cause the at least one processor to perform intra prediction of the chroma component of the current block using the intra prediction mode determined by performing the DIMD.

[0120] The AIPM list may include only directional patterns, and the number of directional patterns included in the AIPM list may be equal to a power of 2 or a sum of multiples of the power of 2.

[0121] Figure 9 is a diagram of a computer system (900) suitable for implementing an embodiment.

[0122] Computer software may be encoded using any suitable machine code or computer language that may be subjected to assembly, compilation, linking, or similar mechanisms to create code comprising instructions that may be executed directly by one or more computer central processing units (CPUs), graphics processing units (GPUs), etc., or through interpretation, microcode execution, etc.

[0123] The instructions may be executed on various types of computers or components thereof, including, for example, personal computers, tablet computers, servers, smart phones, gaming devices, IoT devices, etc.

[0124] Figure 9 The components of the computer system (900) shown are exemplary in nature and are not intended to suggest any limitation on the scope of use or functionality of computer software implementing the embodiments. Neither should the configuration of the components be interpreted as having any dependency or requirement relating to any one or combination of components shown in the embodiments of the computer system (900).

[0125] The computer system (900) may include certain human interface input devices. Such human interface input devices may be responsive to input from one or more human users through, for example, tactile input (e.g., keystrokes, swipes, data glove movements), audio input (e.g., speech, hand clapping), visual input (e.g., gestures), and olfactory input (not depicted). The human interface devices may also be used to capture certain media that are not necessarily directly related to human conscious input, such as audio (e.g., speech, music, ambient sounds), images (e.g., scanned images, photographic images from a still camera), and video (e.g., two-dimensional video, three-dimensional video including stereoscopic video).

[0126] The input human-machine interface device may include one or more of the following (only one of each is shown): keyboard (901), mouse (902), touchpad (903), touch screen (910), data gloves, joystick (905), microphone (906), scanner (907), camera (908).

[0127] The computer system (900) may also include certain human interface output devices. Such human interface output devices may stimulate one or more senses of a human user, for example, through tactile output, sound, light, and smell / taste. Such human-machine interface output devices may include tactile output devices (e.g., tactile feedback of a touch screen (910), data gloves, or joysticks (905), but may also be tactile feedback devices that are not input devices), audio output devices (e.g., speakers (909), headphones (not depicted)), visual output devices (e.g., screens (910) including cathode ray tube (CRT) screens, liquid crystal display (LCD) screens, plasma screens, organic light-emitting diode (OLED) screens, each with or without touch screen input capabilities, each with or without tactile feedback capabilities - some of which are capable of outputting two-dimensional visual output or output in more than three dimensions through devices such as stereoscopic image output, virtual reality glasses (not depicted), holographic displays and smoke boxes (not depicted), and printers (not depicted). The graphics adapter (950) generates images and outputs the images to the touch screen (910).

[0128] The computer system (900) may also include human-accessible storage devices and their associated media, such as optical media including CD / DVD ROM / RW (920) including CD / DVD etc. media (921), thumb drives (922), removable hard drives or solid-state drives (923), traditional magnetic media such as tapes and floppy disks (not depicted), dedicated ROM / ASIC / PLD based devices such as security dongles (not depicted), etc.

[0129] Those skilled in the art will also understand that the term "computer-readable medium" used in connection with the presently disclosed subject matter does not encompass transmission media, carrier waves, or other transitory signals.

[0130] The computer system (900) may also include an interface to one or more communication networks (955). The network (955) may be, for example, a wireless network, a wired network, an optical network. The network (955) may further be a local area network, a wide area network, a metropolitan area network, a vehicle and industrial network, a real-time network, a delay-tolerant network, etc. Examples of the network (955) include a local area network such as Ethernet, a wireless LAN, a cellular network including Global System for Mobile Communications (GSM), third generation (3G), fourth generation (4G), fifth generation (5G), long term evolution (LTE), etc., a television wired or wireless wide area digital network including cable television, satellite television, and terrestrial broadcast television, a vehicle and industrial television including CANBus, etc. Some networks (955) typically require an external network interface adapter connected to some universal data port or peripheral bus (949) (e.g., a universal serial bus (USB) port of the computer system (900)); as described below, other network interfaces are typically integrated into the core of the computer system (900) by connecting to the system bus (e.g., connecting to an Ethernet interface in a PC computer system or connecting to a cellular network interface (954) in a smartphone computer system). The computer system (900) can use any of these networks (955) to communicate with other entities. Such communication can be one-way receive only (e.g., broadcast television), one-way send only (e.g., CANbus connected to some CANbus devices), or two-way, for example, using a local area network or wide area network digital network to connect to other computer systems. As described above, certain protocols and protocol stacks can be used on each of those networks (955) and network interfaces (954).

[0131] The above-mentioned human-machine interface device, human-machine accessible storage device and network interface (954) may be attached to the kernel (940) of the computer system (900).

[0132] The core (940) may include one or more central processing units (CPUs) (941), graphics processing units (GPUs) (942), specialized programmable processing units in the form of field programmable gate arrays (FPGAs) (943), hardware accelerators (194) for certain tasks, and the like. These devices, as well as read-only memory (ROM) (945), random access memory (RAM) (946), and internal mass storage (947) such as internal non-user accessible hard drives, solid-state drives (SSDs), and the like, may be connected via a system bus (948). In some computer systems, the system bus (948) may be accessed in the form of one or more physical plugs to enable expansion with additional CPUs, GPUs, and the like. Peripheral devices may be connected directly to the core's system bus (948) or to the core's system bus (948) via a peripheral bus (949). Peripheral bus architectures include peripheral component interconnect (PCI), USB, and the like.

[0133] The CPU (941), GPU (942), FPGA (943) and accelerator (Accl.) (944) can execute certain instructions, which can be combined to form the above-mentioned computer code. The computer code can be stored in ROM (945) or RAM (946). Transient data can also be stored in RAM (946), while permanent data can be stored, for example, in internal mass storage (947). Fast storage and retrieval to any storage device can be achieved by using a cache, which can be closely associated with the following: one or more CPUs (941), GPUs (942), mass storage (947), ROM (945), RAM (946), etc.

[0134] The computer readable medium may have computer code thereon for performing various computer-implemented operations. The medium and computer code may be those specially designed and constructed for the purposes of the embodiments, or they may be of a type well known and available to those skilled in the art of computer software.

[0135] As a non-limiting example, a computer system having architecture (900), particularly kernel (940), may provide functionality due to one or more processors (including CPUs, GPUs, FPGAs, accelerators, etc.) executing software contained in one or more tangible computer-readable media. Such computer-readable media may be media associated with user-accessible mass storage as described above, as well as certain non-temporary memories of kernel (940), such as kernel internal mass storage (947) or ROM (945). Software for implementing various embodiments may be stored in such devices and executed by kernel (940). Depending on specific needs, the computer-readable medium may include one or more storage devices or chips. The software may enable kernel (940), particularly the processors therein (including CPUs, GPUs, FPGAs, etc.), to perform specific processes or specific parts of specific processes described herein, including defining data structures stored in RAM (946) and modifying such data structures according to processes defined by the software. Additionally or alternatively, the computer system may provide functionality due to logic hardwired or otherwise embodied in circuitry (e.g., accelerator (944)), which may replace software or operate in conjunction with software to perform specific processes or specific portions of specific processes described herein. Where appropriate, references to software may include logic and vice versa. Where appropriate, references to computer-readable media may include circuitry (e.g., integrated circuits (ICs)) storing software for execution, circuitry embodying logic for execution, or both. Embodiments include any suitable combination of hardware and software.

[0136] Although the present disclosure has described a number of embodiments, there are modifications, permutations, and various alternative equivalents that fall within the scope of the present disclosure. Therefore, it should be understood that those skilled in the art will be able to devise many systems and methods that, although not explicitly shown or described herein, embody the principles of the present disclosure and therefore fall within the spirit and scope of the present disclosure.

Claims

1. A method for performing intra prediction of a current block of an image of a video sequence, the method being performed by at least one processor, and the method comprising: determining whether a first flag indicates that the intra prediction mode corresponding to the current block is a directional mode; as well as determining whether a second flag indicates that the intra prediction mode is a decoder-side intra-mode derivation (DIMD) mode based on determining that the first flag indicates that the intra prediction mode corresponding to the current block is the directional mode; Based on determining that the second flag does not indicate that the intra prediction mode is the DIMD mode: Determine the index of the intra prediction mode in the allowed intra prediction mode AIPM list; and performing intra prediction of the current block using the intra prediction mode corresponding to the determined index in the AIPM list; as well as Based on determining that the second flag indicates that the intra prediction mode is the DIMD mode: performing DIMD to determine the intra prediction mode; and Intra prediction of the current block is performed using the determined intra prediction mode.

2. The method according to claim 1, wherein The method further comprises first inserting the intra prediction mode determined by performing a decoder-side intra mode derivation DIMD into a first level of the AIPM list.

3. The method according to claim 1, wherein The method further includes performing intra prediction of a chroma component of the current block using the intra prediction mode determined by performing the DIMD.

4. The method according to any one of claims 1 to 3, wherein The method further includes: based on determining that the first flag does not indicate that the intra prediction mode corresponding to the current block is the directional mode: determining the intra prediction mode to be one of a plurality of non-directional modes; and Intra prediction of the current block is performed using the determined intra prediction mode.

5. The method according to any one of claims 1 to 3, wherein The method further includes performing intra prediction of a luma component of the current block using at least one intra prediction mode in the AIPM list.

6. The method according to any one of claims 1 to 3, wherein The AIPM list includes only directional modes, and The number of directional patterns included in the AIPM list is equal to a power of 2 or a sum of multiples of the power of 2.

7. An apparatus for performing intra prediction of a current block of an image of a video sequence, the apparatus comprising: at least one memory configured to store computer program code; as well as at least one processor configured to access the at least one memory and to operate according to the computer program code, the computer program code comprising: a first determining code configured to cause the at least one processor to determine whether a first flag indicates that the intra prediction mode corresponding to the current block is a directional mode; a third determining code configured to cause the at least one processor to determine that the first flag indicates that the intra prediction mode corresponding to the current block is the directional mode, and to determine whether the second flag indicates that the intra prediction mode is a decoder-side intra mode derivation DIMD mode; A second determination code configured to cause the at least one processor to determine that the second flag does not indicate that the intra prediction mode is the DIMD mode: determine an index of the intra prediction mode in an allowed intra prediction mode AIPM list; and a first execution code configured to cause at least one processor to perform intra prediction of the current block using the intra prediction mode corresponding to the determined index in the AIPM list, based on determining that the second flag does not indicate that the intra prediction mode corresponding to the current block is the DIMD mode; and A second execution code configured to cause at least one processor to, based on determining that the second flag indicates that the intra prediction mode is the DIMD mode: perform DIMD to determine the intra prediction mode; and The first execution code is further configured to enable the at least one processor to perform intra prediction of the current block using the determined intra prediction mode based on determining that the second flag indicates that the intra prediction mode corresponding to the current block is the DIMD mode.

8. The device according to claim 7, wherein The apparatus further includes an insertion code configured to cause the at least one processor to first insert an intra prediction mode determined by performing a decoder-side intra mode derivation (DIMD) into a first level of the AIPM list.

9. The device according to claim 7, wherein The apparatus further includes a third execution code configured to cause the at least one processor to perform intra prediction of a chroma component of the current block using the intra prediction mode determined by executing the DIMD.

10. The device according to any one of claims 7 to 9, wherein The apparatus further includes fourth determining code configured to cause the at least one processor to determine that the intra prediction mode is one of a plurality of non-directional modes based on determining that the first flag does not indicate that the intra prediction mode corresponding to the current block is the directional mode, The first execution code is further configured to cause the at least one processor to perform intra prediction of the current block using the determined intra prediction mode based on determining that the first flag does not indicate that the intra prediction mode corresponding to the current block is the directional mode.

11. The device according to any one of claims 7 to 9, wherein The apparatus further includes a third execution code configured to cause the at least one processor to perform intra prediction of a luma component of the current block using at least one intra prediction mode in the AIPM list.

12. The device according to any one of claims 7 to 9, wherein The AIPM list includes only directional modes, and The number of directional patterns included in the AIPM list is equal to a power of 2 or a sum of multiples of the power of 2.

13. A non-transitory computer-readable storage medium storing instructions that cause at least one processor to: determining whether the first flag indicates that the intra prediction mode corresponding to the current block is a directional mode; as well as determining whether a second flag indicates that the intra prediction mode is a decoder-side intra-mode derivation (DIMD) mode based on determining that the first flag indicates that the intra prediction mode corresponding to the current block is the directional mode; Based on determining that the second flag does not indicate that the intra prediction mode is the DIMD mode: Determine the index of the intra prediction mode in the allowed intra prediction mode AIPM list; and performing intra prediction of the current block using the intra prediction mode corresponding to the determined index in the AIPM list; as well as Based on determining that the second flag indicates that the intra prediction mode is the DIMD mode: performing DIMD to determine the intra prediction mode; and Intra prediction of the current block is performed using the determined intra prediction mode.

14. The non-transitory computer-readable storage medium of claim 13, wherein: The instructions further cause the at least one processor to first insert the intra prediction mode determined by performing a decoder-side intra mode derivation DIMD into a first level of the AIPM list.

15. The non-transitory computer-readable storage medium of claim 13, wherein: The instructions further cause the at least one processor to perform intra prediction of a chroma component of the current block using the intra prediction mode determined by executing the DIMD.

16. The non-transitory computer-readable storage medium according to any one of claims 13 to 15, wherein: The instructions further cause the at least one processor, based on determining that the first flag does not indicate that the intra-prediction mode corresponding to the current block is the directional mode: determining the intra prediction mode to be one of a plurality of non-directional modes; and Intra prediction of the current block is performed using the determined intra prediction mode.

17. The non-transitory computer-readable storage medium according to any one of claims 13 to 15, wherein: The instructions further cause the at least one processor to perform intra prediction of the luma component of the current block using at least one intra prediction mode in the AIPM list.

18. A method for storing a bit stream, characterized in that: In the encoding and decoding process of the bit stream, intra-frame prediction is performed based on the method for performing intra-frame prediction of a current block of an image of a video sequence according to any one of claims 1 to 6.

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