WO2020185047A1 - 인트라 예측을 수행하는 영상 부호화/복호화 방법, 장치 및 비트스트림을 전송하는 방법 - Google Patents
인트라 예측을 수행하는 영상 부호화/복호화 방법, 장치 및 비트스트림을 전송하는 방법 Download PDFInfo
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Definitions
- the present disclosure relates to an image encoding/decoding method and apparatus, and more particularly, a method and apparatus for encoding/decoding an image using intra prediction, and transmitting a bitstream generated by the image encoding method/apparatus of the present disclosure. It's about how to do it.
- An object of the present disclosure is to provide an image encoding/decoding method and apparatus with improved encoding/decoding efficiency.
- an object of the present disclosure is to provide a method and apparatus for encoding/decoding an image using intra prediction.
- the present disclosure provides an image encoding/decoding method and apparatus for deriving an intra prediction mode of a chroma block based on an intra prediction mode of a corresponding luma block or a default intra prediction mode, and then performing intra prediction on a chroma block. It is aimed at.
- an object of the present disclosure is to provide a method for transmitting a bitstream generated by an image encoding method or apparatus according to the present disclosure.
- an object of the present disclosure is to provide a recording medium storing a bitstream generated by an image encoding method or apparatus according to the present disclosure.
- an object of the present disclosure is to provide a recording medium storing a bitstream that is received and decoded by an image decoding apparatus according to the present disclosure and used for image restoration.
- an image decoding method based on information on prediction of a current chroma block, determining whether intra prediction is applied to the current chroma block, wherein intra prediction is applied to the current chroma block.
- deriving an intra prediction mode of the current chroma block based on the intra prediction mode of the corresponding luma block corresponding to the current chroma block and the intra chroma prediction mode information of the current chroma block, and intra prediction of the current chroma block Generating a prediction block for the current chroma block by performing intra prediction based on a mode, and when an intra prediction mode of the corresponding luma block does not exist, the intra prediction mode of the current chroma block is a default It can be derived based on the intra prediction mode.
- the deriving of the intra prediction mode of the current chroma block may include determining a method of predicting a predetermined position of the corresponding luma block.
- the intra prediction mode of the current chroma block is derived based on an intra prediction mode of a predetermined position of the corresponding luma block
- the intra prediction mode of the current chroma block may be derived based on the default intra prediction mode
- the intra prediction mode of the current chroma block is derived based on the default intra prediction mode. I can.
- the predetermined position may be a center position of the corresponding luma block.
- the default intra prediction mode may be a planar mode or a DC mode.
- the tree structure of the current chroma block may be a dual tree (DUAL_TREE) structure.
- the intra prediction mode of the current chroma block is If the intra prediction mode of the corresponding luma block is derived, and the intra prediction mode information of the current chroma block indicates a DM mode, and there is no intra prediction mode of the corresponding luma block, the intra prediction mode of the current chroma block is the It can be derived as a default intra prediction mode.
- DM direct mode
- An image decoding apparatus includes a memory and at least one processor, wherein the at least one processor determines whether intra prediction is applied to the current chroma block based on information on prediction of a current chroma block. Whether to determine whether or not, and when intra prediction is applied to the current chroma block, based on the intra prediction mode of the corresponding luma block corresponding to the current chroma block and the intra chroma prediction mode information of the current chroma block, the current chroma block is By deriving an intra prediction mode and performing intra prediction based on the intra prediction mode of the current chroma block, a prediction block for the current chroma block is generated, and there is no intra prediction mode of the corresponding luma block, The intra prediction mode of the current chroma block may be derived based on a default intra prediction mode.
- An image encoding method includes determining whether intra prediction is applied to a current chroma block, and when intra prediction is applied to the current chroma block, a corresponding luma block corresponding to the current chroma block Deriving an intra prediction mode of the current chroma block based on the intra prediction mode of, generating a prediction block for the current chroma block by performing intra prediction based on the intra prediction mode of the current chroma block, and Encoding an intra prediction mode of the current chroma block based on the intra prediction mode of the corresponding luma block, and if there is no intra prediction mode of the corresponding luma block, the intra prediction mode of the current chroma block is It can be derived based on the default intra prediction mode.
- deriving the intra prediction mode of the current chroma block may include determining a method of predicting a predetermined position of the corresponding luma block.
- an intra prediction mode of the current chroma block is derived based on an intra prediction mode at a predetermined position of the corresponding luma block.
- the intra prediction mode of the current chroma block may be derived based on the default intra prediction mode.
- the predetermined position may be a center position of the corresponding luma block.
- the default intra prediction mode may be a planar mode or a DC mode.
- a transmission method may transmit a bitstream generated by the image encoding apparatus or image encoding method of the present disclosure.
- a computer-readable recording medium may store a bitstream generated by the image encoding method or image encoding apparatus of the present disclosure.
- an image encoding/decoding method and apparatus with improved encoding/decoding efficiency may be provided.
- a method and apparatus for encoding/decoding an image using intra prediction may be provided.
- an image encoding/decoding method and apparatus for performing intra prediction on a chroma block can be provided.
- a method for transmitting a bitstream generated by an image encoding method or apparatus according to the present disclosure may be provided.
- a recording medium storing a bitstream generated by an image encoding method or apparatus according to the present disclosure may be provided.
- a recording medium may be provided that stores a bitstream that is received and decoded by the image decoding apparatus according to the present disclosure and used for image restoration.
- FIG. 1 is a diagram schematically illustrating a video coding system to which an embodiment according to the present disclosure can be applied.
- FIG. 2 is a diagram schematically illustrating an image encoding apparatus to which an embodiment according to the present disclosure can be applied.
- FIG. 3 is a diagram schematically illustrating an image decoding apparatus to which an embodiment according to the present disclosure can be applied.
- FIG. 4 is a diagram showing a block division type according to a multi-type tree structure.
- FIG. 5 is a diagram illustrating a signaling mechanism of partitioning information of a quadtree with nested multi-type tree structure according to the present disclosure.
- FIG. 6 is a flowchart illustrating a video/video encoding method based on intra prediction.
- FIG. 7 is a diagram illustrating an exemplary configuration of an intra prediction unit 185 according to the present disclosure.
- FIG. 8 is a flowchart illustrating a video/video decoding method based on intra prediction.
- FIG. 9 is a diagram illustrating an exemplary configuration of an intra prediction unit 265 according to the present disclosure.
- FIG. 10 is a flowchart illustrating an intra prediction mode signaling procedure in an image encoding apparatus.
- 11 is a flowchart illustrating a procedure for determining an intra prediction mode in an image decoding apparatus.
- FIG. 12 is a flowchart for describing a procedure for deriving an intra prediction mode in more detail.
- FIG. 13 is a diagram illustrating an intra prediction direction according to an embodiment of the present disclosure.
- FIG. 14 is a diagram illustrating an intra prediction direction according to another embodiment of the present disclosure.
- 15 is a diagram illustrating a predetermined position for deriving an intra prediction mode of a current chroma block in the case of the DM mode.
- FIG. 16 is a flowchart illustrating a conventional method of deriving an intra prediction mode of a chroma block based on a corresponding luma block.
- FIG. 17 is a flowchart illustrating an embodiment of the present disclosure in which an intra prediction mode of a chroma block is derived based on a corresponding luma block.
- FIG. 18 is a flowchart illustrating another embodiment of the present disclosure in which an intra prediction mode of a chroma block is derived based on a corresponding luma block.
- 19 is a flowchart illustrating another embodiment of the present disclosure for deriving an intra prediction mode of a chroma block based on a corresponding luma block.
- 20 is a flowchart illustrating an embodiment of the present disclosure in which an intra prediction mode of a current block is derived based on a corresponding block.
- FIG. 21 is a flowchart illustrating still another embodiment of the present disclosure in which an intra prediction mode of a chroma block is derived and a chroma block is encoded based on a corresponding luma block.
- FIG. 22 is a diagram illustrating a content streaming system to which an embodiment of the present disclosure can be applied.
- first and second are used only for the purpose of distinguishing one component from other components, and do not limit the order or importance of the components unless otherwise stated. Accordingly, within the scope of the present disclosure, a first component in one embodiment may be referred to as a second component in another embodiment, and similarly, a second component in one embodiment is a first component in another embodiment. It can also be called.
- components that are distinguished from each other are intended to clearly describe each feature, and do not necessarily mean that the components are separated. That is, a plurality of components may be integrated to be formed in one hardware or software unit, or one component may be distributed in a plurality of hardware or software units. Therefore, even if not stated otherwise, such integrated or distributed embodiments are also included in the scope of the present disclosure.
- the components described in various embodiments do not necessarily mean essential components, and some may be optional components. Accordingly, an embodiment consisting of a subset of components described in an embodiment is also included in the scope of the present disclosure. In addition, embodiments including other elements in addition to the elements described in the various embodiments are included in the scope of the present disclosure.
- the present disclosure relates to encoding and decoding of an image, and terms used in the present disclosure may have a common meaning commonly used in the technical field to which the present disclosure belongs unless newly defined in the present disclosure.
- a “picture” generally refers to a unit representing one image in a specific time period
- a slice/tile is a coding unit constituting a part of a picture
- one picture is one It may be composed of more than one slice/tile.
- a slice/tile may include one or more coding tree units (CTU).
- pixel or "pel” may mean a minimum unit constituting one picture (or image).
- sample may be used as a term corresponding to a pixel.
- a sample may generally represent a pixel or a value of a pixel, may represent only a pixel/pixel value of a luma component, or may represent only a pixel/pixel value of a chroma component.
- unit may represent a basic unit of image processing.
- the unit may include at least one of a specific area of a picture and information related to the corresponding area.
- the unit may be used interchangeably with terms such as “sample array”, “block”, or “area” depending on the case.
- the MxN block may include samples (or sample arrays) consisting of M columns and N rows, or a set (or array) of transform coefficients.
- current block may mean one of “current coding block”, “current coding unit”, “coding object block”, “decoding object block”, or “processing object block”.
- current block may mean “current prediction block” or “prediction target block”.
- transformation inverse transformation
- quantization inverse quantization
- current block may mean “current transform block” or “transform target block”.
- filtering is performed, “current block” may mean “block to be filtered”.
- current block may mean a block including both a luma component block and a chroma component block or "a luma block of the current block” unless explicitly stated as a chroma block.
- the chroma block of the current block may be explicitly expressed by including an explicit description of a chroma block such as a "chroma block” or a "current chroma block”.
- FIG. 1 shows a video coding system according to this disclosure.
- a video coding system may include an encoding device 10 and a decoding device 20.
- the encoding device 10 may transmit the encoded video and/or image information or data in a file or streaming format to the decoding device 20 through a digital storage medium or a network.
- the encoding apparatus 10 may include a video source generator 11, an encoder 12, and a transmission unit 13.
- the decoding apparatus 20 may include a receiving unit 21, a decoding unit 22, and a rendering unit 23.
- the encoder 12 may be referred to as a video/image encoder, and the decoder 22 may be referred to as a video/image decoder.
- the transmission unit 13 may be included in the encoding unit 12.
- the receiving unit 21 may be included in the decoding unit 22.
- the rendering unit 23 may include a display unit, and the display unit may be configured as a separate device or an external component.
- the video source generator 11 may acquire a video/image through a process of capturing, synthesizing, or generating a video/image.
- the video source generator 11 may include a video/image capturing device and/or a video/image generating device.
- the video/image capture device may include, for example, one or more cameras, a video/image archive including previously captured video/images, and the like.
- the video/image generating device may include, for example, a computer, a tablet and a smartphone, and may (electronically) generate a video/image.
- a virtual video/image may be generated through a computer or the like, and in this case, a video/image capturing process may be substituted as a process of generating related data.
- the encoder 12 may encode an input video/image.
- the encoder 12 may perform a series of procedures such as prediction, transformation, and quantization for compression and encoding efficiency.
- the encoder 12 may output encoded data (coded video/image information) in a bitstream format.
- the transmission unit 13 may transmit the encoded video/image information or data output in the form of a bitstream to the receiving unit 21 of the decoding apparatus 20 through a digital storage medium or a network in a file or streaming form.
- Digital storage media may include various storage media such as USB, SD, CD, DVD, Blu-ray, HDD, and SSD.
- the transmission unit 13 may include an element for generating a media file through a predetermined file format, and may include an element for transmission through a broadcast/communication network.
- the receiving unit 21 may extract/receive the bitstream from the storage medium or network and transmit it to the decoding unit 22.
- the decoder 22 may decode the video/image by performing a series of procedures such as inverse quantization, inverse transformation, and prediction corresponding to the operation of the encoder 12.
- the rendering unit 23 may render the decoded video/image.
- the rendered video/image may be displayed through the display unit.
- FIG. 2 is a diagram schematically illustrating an image encoding apparatus to which an embodiment according to the present disclosure can be applied.
- the image encoding apparatus 100 includes an image segmentation unit 110, a subtraction unit 115, a transform unit 120, a quantization unit 130, an inverse quantization unit 140, and an inverse transform unit ( 150), an addition unit 155, a filtering unit 160, a memory 170, an inter prediction unit 180, an intra prediction unit 185, and an entropy encoding unit 190.
- the inter prediction unit 180 and the intra prediction unit 185 may be collectively referred to as a “prediction unit”.
- the transform unit 120, the quantization unit 130, the inverse quantization unit 140, and the inverse transform unit 150 may be included in a residual processing unit.
- the residual processing unit may further include a subtraction unit 115.
- All or at least some of the plurality of constituent units constituting the image encoding apparatus 100 may be implemented as one hardware component (eg, an encoder or a processor) according to embodiments.
- the memory 170 may include a decoded picture buffer (DPB), and may be implemented by a digital storage medium.
- DPB decoded picture buffer
- the image dividing unit 110 may divide an input image (or picture, frame) input to the image encoding apparatus 100 into one or more processing units.
- the processing unit may be referred to as a coding unit (CU).
- the coding unit is a coding tree unit (CTU) or a largest coding unit (LCU) recursively according to a QT/BT/TT (Quad-tree/binary-tree/ternary-tree) structure ( It can be obtained by dividing recursively.
- one coding unit may be divided into a plurality of coding units of a deeper depth based on a quad tree structure, a binary tree structure, and/or a ternary tree structure.
- a quad tree structure may be applied first, and a binary tree structure and/or a ternary tree structure may be applied later.
- the coding procedure according to the present disclosure may be performed based on the final coding unit that is no longer divided.
- the largest coding unit may be directly used as the final coding unit, or a coding unit of a lower depth obtained by dividing the largest coding unit may be used as the final cornet unit.
- the coding procedure may include a procedure such as prediction, transformation, and/or restoration described later.
- the processing unit of the coding procedure may be a prediction unit (PU) or a transform unit (TU).
- Each of the prediction unit and the transform unit may be divided or partitioned from the final coding unit.
- the prediction unit may be a unit of sample prediction
- the transform unit may be a unit for inducing a transform coefficient and/or a unit for inducing a residual signal from the transform coefficient.
- the prediction unit (inter prediction unit 180 or intra prediction unit 185) performs prediction on a block to be processed (current block), and generates a predicted block including prediction samples for the current block. Can be generated.
- the prediction unit may determine whether intra prediction or inter prediction is applied in units of the current block or CU.
- the prediction unit may generate various information on prediction of the current block and transmit it to the entropy encoding unit 190.
- the information on prediction may be encoded by the entropy encoding unit 190 and output in the form of a bitstream.
- the intra prediction unit 185 may predict the current block by referring to samples in the current picture.
- the referenced samples may be located in a neighborhood of the current block or may be located away from each other according to an intra prediction mode and/or an intra prediction technique.
- the intra prediction modes may include a plurality of non-directional modes and a plurality of directional modes.
- the non-directional mode may include, for example, a DC mode and a planar mode (Planar mode).
- the directional mode may include, for example, 33 directional prediction modes or 65 directional prediction modes, depending on the degree of detail of the prediction direction. However, this is an example, and more or less directional prediction modes may be used depending on the setting.
- the intra prediction unit 185 may determine a prediction mode applied to the current block by using the prediction mode applied to the neighboring block.
- the inter prediction unit 180 may derive a predicted block for the current block based on a reference block (reference sample array) specified by a motion vector on the reference picture.
- motion information may be predicted in units of blocks, subblocks, or samples based on a correlation between motion information between a neighboring block and a current block.
- the motion information may include a motion vector and a reference picture index.
- the motion information may further include inter prediction direction (L0 prediction, L1 prediction, Bi prediction, etc.) information.
- the neighboring block may include a spatial neighboring block existing in the current picture and a temporal neighboring block existing in the reference picture.
- the reference picture including the reference block and the reference picture including the temporal neighboring block may be the same or different from each other.
- the temporal neighboring block may be referred to as a collocated reference block, a collocated CU (colCU), or the like.
- a reference picture including the temporal neighboring block may be referred to as a collocated picture (colPic).
- the inter prediction unit 180 constructs a motion information candidate list based on neighboring blocks, and provides information indicating which candidate is used to derive a motion vector and/or a reference picture index of the current block. Can be generated. Inter prediction may be performed based on various prediction modes.
- the inter prediction unit 180 may use motion information of a neighboring block as motion information of a current block.
- a residual signal may not be transmitted.
- motion vector prediction (MVP) mode motion vectors of neighboring blocks are used as motion vector predictors, and indicators for motion vector difference and motion vector predictors ( indicator) to signal the motion vector of the current block.
- the motion vector difference may mean a difference between a motion vector of a current block and a motion vector predictor.
- the prediction unit may generate a prediction signal based on various prediction methods and/or prediction techniques to be described later. For example, the prediction unit may apply intra prediction or inter prediction for prediction of the current block, and may simultaneously apply intra prediction and inter prediction. A prediction method in which intra prediction and inter prediction are applied simultaneously for prediction of a current block may be called combined inter and intra prediction (CIIP). Also, the prediction unit may perform intra block copy (IBC) for prediction of the current block. The intra block copy may be used for content image/movie coding such as games, such as, for example, screen content coding (SCC). IBC is a method of predicting a current block by using a reference block in a current picture at a distance from the current block by a predetermined distance.
- CIIP combined inter and intra prediction
- IBC intra block copy
- the intra block copy may be used for content image/movie coding such as games, such as, for example, screen content coding (SCC).
- IBC is a method of predicting a current block by using a reference
- the position of the reference block in the current picture may be encoded as a vector (block vector) corresponding to the predetermined distance.
- IBC basically performs prediction in the current picture, but may be performed similarly to inter prediction in that it derives a reference block in the current picture. That is, the IBC may use at least one of the inter prediction techniques described in this disclosure.
- the prediction signal generated through the prediction unit may be used to generate a reconstructed signal or may be used to generate a residual signal.
- the subtraction unit 115 subtracts the prediction signal (predicted block, prediction sample array) output from the prediction unit from the input image signal (original block, original sample array), and subtracts a residual signal (remaining block, residual sample array). ) Can be created.
- the generated residual signal may be transmitted to the converter 120.
- the transform unit 120 may generate transform coefficients by applying a transform technique to the residual signal.
- the transformation technique uses at least one of DCT (Discrete Cosine Transform), DST (Discrete Sine Transform), KLT (Karhunen-Loeve Transform), GBT (Graph-Based Transform), or CNT (Conditionally Non-linear Transform).
- DCT Discrete Cosine Transform
- DST Discrete Sine Transform
- KLT Kerhunen-Loeve Transform
- GBT Graph-Based Transform
- CNT Conditionally Non-linear Transform
- GBT refers to the transformation obtained from this graph when the relationship information between pixels is expressed in a graph.
- CNT refers to a transformation obtained based on generating a prediction signal using all previously reconstructed pixels.
- the conversion process may be applied to a block of pixels having the same size of a square, or may be applied to a block of a variable size other than a square.
- the quantization unit 130 may quantize the transform coefficients and transmit the quantization to the entropy encoding unit 190.
- the entropy encoding unit 190 may encode a quantized signal (information on quantized transform coefficients) and output it as a bitstream.
- the information on the quantized transform coefficients may be called residual information.
- the quantization unit 130 may rearrange the quantized transform coefficients in the form of a block into a one-dimensional vector form based on a coefficient scan order, and the quantized transform coefficients in the form of the one-dimensional vector It is also possible to generate information about transform coefficients.
- the entropy encoding unit 190 may perform various encoding methods such as exponential Golomb, context-adaptive variable length coding (CAVLC), and context-adaptive binary arithmetic coding (CABAC).
- the entropy encoding unit 190 may encode together or separately information necessary for video/image restoration (eg, values of syntax elements) in addition to quantized transform coefficients.
- the encoded information (eg, encoded video/video information) may be transmitted or stored in a bitstream format in units of network abstraction layer (NAL) units.
- the video/video information may further include information on various parameter sets, such as an adaptation parameter set (APS), a picture parameter set (PPS), a sequence parameter set (SPS), or a video parameter set (VPS).
- the video/video information may further include general constraint information.
- the signaling information, transmitted information, and/or syntax elements mentioned in the present disclosure may be encoded through the above-described encoding procedure and included in the bitstream.
- the bitstream may be transmitted through a network or may be stored in a digital storage medium.
- the network may include a broadcasting network and/or a communication network
- the digital storage medium may include various storage media such as USB, SD, CD, DVD, Blu-ray, HDD, and SSD.
- a transmission unit (not shown) for transmitting the signal output from the entropy encoding unit 190 and/or a storage unit (not shown) for storing may be provided as an inner/outer element of the image encoding apparatus 100, or transmission The unit may be provided as a component of the entropy encoding unit 190.
- the quantized transform coefficients output from the quantization unit 130 may be used to generate a residual signal.
- a residual signal residual block or residual samples
- inverse quantization and inverse transform residual transforms
- the addition unit 155 adds the reconstructed residual signal to the prediction signal output from the inter prediction unit 180 or the intra prediction unit 185 to obtain a reconstructed signal (a reconstructed picture, a reconstructed block, and a reconstructed sample array). Can be generated.
- a reconstructed signal (a reconstructed picture, a reconstructed block, and a reconstructed sample array).
- the predicted block may be used as a reconstructed block.
- the addition unit 155 may be referred to as a restoration unit or a restoration block generation unit.
- the generated reconstructed signal may be used for intra prediction of the next processing target block in the current picture, and may be used for inter prediction of the next picture through filtering as described later.
- the filtering unit 160 may apply filtering to the reconstructed signal to improve subjective/objective image quality.
- the filtering unit 160 may generate a modified reconstructed picture by applying various filtering methods to the reconstructed picture, and the modified reconstructed picture may be converted to the memory 170, specifically, the DPB of the memory 170. Can be saved on.
- the various filtering methods may include, for example, deblocking filtering, sample adaptive offset, adaptive loop filter, bilateral filter, and the like.
- the filtering unit 160 may generate a variety of filtering information and transmit it to the entropy encoding unit 190 as described later in the description of each filtering method.
- the filtering information may be encoded by the entropy encoding unit 190 and output in the form of a bitstream.
- the modified reconstructed picture transmitted to the memory 170 may be used as a reference picture in the inter prediction unit 180.
- the image encoding apparatus 100 may avoid prediction mismatch between the image encoding apparatus 100 and the image decoding apparatus, and may improve encoding efficiency.
- the DPB in the memory 170 may store a reconstructed picture modified to be used as a reference picture in the inter prediction unit 180.
- the memory 170 may store motion information of a block from which motion information in a current picture is derived (or encoded) and/or motion information of blocks in a picture that have already been reconstructed.
- the stored motion information may be transmitted to the inter prediction unit 180 to be used as motion information of spatial neighboring blocks or motion information of temporal neighboring blocks.
- the memory 170 may store reconstructed samples of reconstructed blocks in the current picture, and may transmit the reconstructed samples to the intra prediction unit 185.
- FIG. 3 is a diagram schematically illustrating an image decoding apparatus to which an embodiment according to the present disclosure can be applied.
- the image decoding apparatus 200 includes an entropy decoding unit 210, an inverse quantization unit 220, an inverse transform unit 230, an addition unit 235, a filtering unit 240, and a memory 250. ), an inter prediction unit 260 and an intra prediction unit 265 may be included.
- the inter prediction unit 260 and the intra prediction unit 265 may be collectively referred to as a “prediction unit”.
- the inverse quantization unit 220 and the inverse transform unit 230 may be included in the residual processing unit.
- All or at least some of the plurality of constituent units constituting the image decoding apparatus 200 may be implemented as one hardware component (eg, a decoder or a processor) according to embodiments.
- the memory 170 may include a DPB and may be implemented by a digital storage medium.
- the image decoding apparatus 200 having received a bitstream including video/image information may reconstruct an image by performing a process corresponding to the process performed by the image encoding apparatus 100 of FIG. 2.
- the image decoding apparatus 200 may perform decoding using a processing unit applied in the image encoding apparatus.
- the processing unit of decoding may be, for example, a coding unit.
- the coding unit may be a coding tree unit or may be obtained by dividing the largest coding unit.
- the reconstructed image signal decoded and output through the image decoding apparatus 200 may be reproduced through a reproduction device (not shown).
- the image decoding apparatus 200 may receive a signal output from the image encoding apparatus of FIG. 2 in the form of a bitstream.
- the received signal may be decoded through the entropy decoding unit 210.
- the entropy decoding unit 210 may parse the bitstream to derive information (eg, video/video information) necessary for image restoration (or picture restoration).
- the video/video information may further include information on various parameter sets, such as an adaptation parameter set (APS), a picture parameter set (PPS), a sequence parameter set (SPS), or a video parameter set (VPS).
- the video/video information may further include general constraint information.
- the image decoding apparatus may additionally use information on the parameter set and/or the general restriction information to decode an image.
- the signaling information, received information and/or syntax elements mentioned in the present disclosure may be obtained from the bitstream by being decoded through the decoding procedure.
- the entropy decoding unit 210 decodes information in the bitstream based on a coding method such as exponential Golomb coding, CAVLC, or CABAC, and a value of a syntax element required for image restoration, a quantized value of a transform coefficient related to a residual. Can be printed.
- the CABAC entropy decoding method receives a bin corresponding to each syntax element in a bitstream, and includes information on the syntax element to be decoded, information on decoding information of a neighboring block and a block to be decoded, or information on a symbol/bin decoded in a previous step
- the context model is determined by using and, according to the determined context model, the probability of occurrence of bins is predicted to perform arithmetic decoding of bins to generate symbols corresponding to the values of each syntax element. I can.
- the CABAC entropy decoding method may update the context model using information of the decoded symbol/bin for the context model of the next symbol/bin after the context model is determined.
- the entropy decoding unit 210 Among the information decoded by the entropy decoding unit 210, information on prediction is provided to the prediction unit (inter prediction unit 260 and intra prediction unit 265), and the register on which entropy decoding is performed by the entropy decoding unit 210 Dual values, that is, quantized transform coefficients and related parameter information may be input to the inverse quantization unit 220. In addition, information about filtering among information decoded by the entropy decoding unit 210 may be provided to the filtering unit 240.
- a receiving unit for receiving a signal output from the image encoding device may be additionally provided as an inner/outer element of the image decoding device 200, or the receiving unit is provided as a component of the entropy decoding unit 210 It could be.
- the video decoding apparatus may include an information decoder (video/video/picture information decoder) and/or a sample decoder (video/video/picture sample decoder).
- the information decoder may include an entropy decoding unit 210, and the sample decoder includes an inverse quantization unit 220, an inverse transform unit 230, an addition unit 235, a filtering unit 240, a memory 250, It may include at least one of the inter prediction unit 260 and the intra prediction unit 265.
- the inverse quantization unit 220 may inverse quantize the quantized transform coefficients and output transform coefficients.
- the inverse quantization unit 220 may rearrange the quantized transform coefficients into a two-dimensional block shape. In this case, the rearrangement may be performed based on a coefficient scan order performed by the image encoding apparatus.
- the inverse quantization unit 220 may perform inverse quantization on quantized transform coefficients by using a quantization parameter (eg, quantization step size information) and obtain transform coefficients.
- a quantization parameter eg, quantization step size information
- the inverse transform unit 230 may inversely transform transform coefficients to obtain a residual signal (residual block, residual sample array).
- the prediction unit may perform prediction on the current block and generate a predicted block including prediction samples for the current block.
- the prediction unit may determine whether intra prediction or inter prediction is applied to the current block based on the prediction information output from the entropy decoding unit 210, and determine a specific intra/inter prediction mode (prediction technique). I can.
- the prediction unit can generate the prediction signal based on various prediction methods (techniques) described later.
- the intra prediction unit 265 may predict the current block by referring to samples in the current picture.
- the description of the intra prediction unit 185 may be equally applied to the intra prediction unit 265.
- the inter prediction unit 260 may derive a predicted block for the current block based on a reference block (reference sample array) specified by a motion vector on the reference picture.
- motion information may be predicted in units of blocks, subblocks, or samples based on a correlation between motion information between a neighboring block and a current block.
- the motion information may include a motion vector and a reference picture index.
- the motion information may further include inter prediction direction (L0 prediction, L1 prediction, Bi prediction, etc.) information.
- the neighboring block may include a spatial neighboring block existing in the current picture and a temporal neighboring block existing in the reference picture.
- the inter prediction unit 260 may construct a motion information candidate list based on neighboring blocks, and derive a motion vector and/or a reference picture index of the current block based on the received candidate selection information.
- Inter prediction may be performed based on various prediction modes (techniques), and the information about the prediction may include information indicating a mode (technique) of inter prediction for the current block.
- the addition unit 235 is reconstructed by adding the obtained residual signal to the prediction signal (predicted block, prediction sample array) output from the prediction unit (including the inter prediction unit 260 and/or the intra prediction unit 265). Signals (restored pictures, reconstructed blocks, reconstructed sample arrays) can be generated. When there is no residual for a block to be processed, such as when the skip mode is applied, the predicted block may be used as a reconstructed block.
- the description of the addition unit 155 may be equally applied to the addition unit 235.
- the addition unit 235 may be referred to as a restoration unit or a restoration block generation unit.
- the generated reconstructed signal may be used for intra prediction of the next processing target block in the current picture, and may be used for inter prediction of the next picture through filtering as described later.
- the filtering unit 240 may apply filtering to the reconstructed signal to improve subjective/objective image quality.
- the filtering unit 240 may generate a modified reconstructed picture by applying various filtering methods to the reconstructed picture, and the modified reconstructed picture may be converted to the memory 250, specifically the DPB of the memory 250. Can be saved on.
- the various filtering methods may include, for example, deblocking filtering, sample adaptive offset, adaptive loop filter, bilateral filter, and the like.
- the (modified) reconstructed picture stored in the DPB of the memory 250 may be used as a reference picture in the inter prediction unit 260.
- the memory 250 may store motion information of a block from which motion information in a current picture is derived (or decoded) and/or motion information of blocks in a picture that have already been reconstructed.
- the stored motion information may be transmitted to the inter prediction unit 260 to be used as motion information of a spatial neighboring block or motion information of a temporal neighboring block.
- the memory 250 may store reconstructed samples of reconstructed blocks in the current picture, and may be transmitted to the intra prediction unit 265.
- embodiments described in the filtering unit 160, the inter prediction unit 180, and the intra prediction unit 185 of the image encoding apparatus 100 are respectively the filtering unit 240 of the image decoding apparatus 200, The same or corresponding to the inter prediction unit 260 and the intra prediction unit 265 may be applied.
- the coding unit is obtained by recursively dividing a coding tree unit (CTU) or a maximum coding unit (LCU) according to a QT/BT/TT (Quad-tree/binary-tree/ternary-tree) structure.
- CTU coding tree unit
- LCU maximum coding unit
- QT/BT/TT Quad-tree/binary-tree/ternary-tree
- the CTU may be first divided into a quadtree structure. Thereafter, leaf nodes of a quadtree structure may be further divided by a multitype tree structure.
- the division according to the quadtree means division in which the current CU (or CTU) is divided into four. By partitioning according to the quadtree, the current CU can be divided into four CUs having the same width and the same height.
- the current CU corresponds to a leaf node of the quadtree structure.
- the CU corresponding to the leaf node of the quadtree structure is no longer divided and may be used as the above-described final coding unit.
- a CU corresponding to a leaf node of a quadtree structure may be further divided by a multitype tree structure.
- the division according to the multi-type tree structure may include two divisions according to a binary tree structure and two divisions according to a ternary tree structure.
- the two divisions according to the binary tree structure may include vertical binary splitting (SPLIT_BT_VER) and horizontal binary splitting (SPLIT_BT_HOR).
- the vertical binary division (SPLIT_BT_VER) means division in which the current CU is divided into two in the vertical direction. As shown in FIG. 4, two CUs having a height equal to the height of the current CU and a width of half the width of the current CU may be generated by vertical binary division.
- the horizontal binary division means division in which the current CU is divided into two in the horizontal direction. As shown in FIG. 4, two CUs having a height of half the height of the current CU and a width equal to the width of the current CU may be generated by horizontal binary division.
- the two divisions according to the ternary tree structure may include vertical ternary splitting (SPLIT_TT_VER) and horizontal ternary splitting (hotizontal ternary splitting, SPLIT_TT_HOR).
- Vertical ternary division (SPLIT_TT_VER) divides the current CU in a vertical direction at a ratio of 1:2:1. As shown in FIG. 4, by vertical ternary division, two CUs having a height equal to the height of the current CU and a width of 1/4 of the width of the current CU, and a current CU having a height equal to the height of the current CU A CU with a width of half the width of can be created.
- the horizontal ternary division divides the current CU horizontally at a ratio of 1:2:1. As shown in FIG. 4, by horizontal ternary division, two CUs having a height of 1/4 of the height of the current CU and having the same width as the width of the current CU and a height of half the height of the current CU One CU can be created with a width equal to the width of the CU.
- FIG. 5 is a diagram illustrating a signaling mechanism of partitioning information of a quadtree with nested multi-type tree structure according to the present disclosure.
- the CTU is treated as the root node of a quadtree, and is first partitioned into a quadtree structure.
- Information eg, qt_split_flag
- qt_split_flag a first value (eg, “1”)
- the current CU may be quadtree split.
- qt_split_flag is a second value (eg, "0")
- the current CU is not divided into a quadtree, but becomes a leaf node (QT_leaf_node) of the quadtree.
- the leaf nodes of each quadtree can then be further partitioned into a multitype tree structure. That is, a leaf node of a quad tree may be a node (MTT_node) of a multi-type tree.
- a first flag eg, mtt_split_cu_flag
- a second flag (ex.mtt_split_cu_verticla_flag) may be signaled to indicate the splitting direction.
- the division direction may be a vertical direction
- the second flag is 0, the division direction may be a horizontal direction.
- a third flag (eg, mtt_split_cu_binary_flag) may be signaled to indicate whether the division type is a binary division type or a ternary division type.
- the division type may be a binary division type
- the third flag when the third flag is 0, the division type may be a ternary division type.
- Nodes of a multitype tree obtained by binary division or ternary division may be further partitioned into a multitype tree structure.
- nodes of a multitype tree cannot be partitioned into a quadtree structure.
- the first flag is 0, the corresponding node of the multitype tree is no longer divided and becomes a leaf node (MTT_leaf_node) of the multitype tree.
- the CU corresponding to the leaf node of the multitype tree may be used as the above-described final coding unit.
- a multi-type tree splitting mode (MttSplitMode) of the CU may be derived as shown in Table 1.
- One CTU may include a coding block of luma samples (hereinafter, referred to as a “luma block”) and two coding blocks of chroma samples corresponding thereto (hereinafter referred to as a “chroma block”).
- the above-described coding tree scheme may be applied equally to the luma block and the chroma block of the current CU, or may be applied separately.
- a luma block and a chroma block in one CTU may be divided into the same block tree structure, and the tree structure in this case may be represented as a single tree (SINGLE_TREE).
- a luma block and a chroma block in one CTU may be divided into individual block tree structures, and the tree structure in this case may be represented as a dual tree (DUAL_TREE). That is, when the CTU is divided into a dual tree, a block tree structure for a luma block and a block tree structure for a chroma block may exist separately.
- the block tree structure for the luma block may be referred to as a dual tree luma (DUAL_TREE_LUMA)
- the block tree structure for the chroma block may be referred to as a dual tree chroma (DUAL_TREE_CHROMA).
- luma blocks and chroma blocks in one CTU may be limited to have the same coding tree structure.
- luma blocks and chroma blocks may have separate block tree structures from each other. If an individual block tree structure is applied, a luma coding tree block (CTB) may be divided into CUs based on a specific coding tree structure, and the chroma CTB may be divided into chroma CUs based on a different coding tree structure. That is, a CU in an I slice/tile group to which an individual block tree structure is applied may be composed of a coding block of a luma component or a coding block of two chroma components.
- CTB luma coding tree block
- the CU in the I slice/tile group to which the same block tree structure is applied and the CU in the P or B slice/tile group may be composed of blocks of three color components (a luma component and two chroma components).
- a quadtree coding tree structure with a multi-type tree has been described, but the structure in which the CU is divided is not limited thereto.
- the BT structure and the TT structure may be interpreted as a concept included in the Multiple Partitioning Tree (MPT) structure, and the CU may be interpreted as being divided through the QT structure and the MPT structure.
- MPT Multiple Partitioning Tree
- a syntax element (e.g., MPT_split_type) including information on how many blocks a leaf node of a QT structure is divided into, and a leaf node of the QT structure are vertical.
- the split structure may be determined by signaling a syntax element (eg, MPT_split_mode) including information on which direction of splitting between horizontal and horizontal.
- the CU may be divided in a different way from the QT structure, BT structure, or TT structure. That is, according to the QT structure, the CU of the lower depth is divided into 1/4 size of the CU of the upper depth, or the CU of the lower depth is divided into 1/2 of the CU of the upper depth according to the BT structure, or according to the TT structure. Unlike CUs of lower depth are divided into 1/4 or 1/2 of CUs of higher depth, CUs of lower depth are 1/5, 1/3, 3/8, 3 of CUs of higher depth depending on the case. It may be divided into /5, 2/3, or 5/8 size, and the method of dividing the CU is not limited thereto.
- Intra prediction may indicate prediction of generating prediction samples for a current block based on reference samples in a picture (hereinafter, referred to as a current picture) to which the current block belongs.
- a current picture a picture to which the current block belongs.
- surrounding reference samples to be used for intra prediction of the current block may be derived.
- the neighboring reference samples of the current block are a sample adjacent to the left boundary of the current block of size nWxnH, a total of 2xnH samples adjacent to the bottom-left, and a sample adjacent to the top boundary of the current block And a total of 2xnW samples adjacent to the top-right side and one sample adjacent to the top-left side of the current block.
- the peripheral reference samples of the current block may include a plurality of columns of upper peripheral samples and a plurality of rows of left peripheral samples.
- the neighboring reference samples of the current block are a total of nH samples adjacent to the right boundary of the current block of size nWxnH, a total of nW samples adjacent to the bottom boundary of the current block, and the lower right side of the current block. It may include one sample adjacent to (bottom-right).
- the decoder may construct neighboring reference samples to be used for prediction by substituting samples that are not available with available samples.
- surrounding reference samples to be used for prediction may be configured through interpolation of available samples.
- a prediction sample can be derived based on an average or interpolation of neighboring reference samples of the current block, and (ii) neighboring reference samples of the current block Among them, the prediction sample may be derived based on a reference sample existing in a specific (prediction) direction with respect to the prediction sample.
- it may be called a non-directional mode or a non-angular mode
- it may be called a directional mode or an angular mode.
- LIP linear interpolation intra prediction
- chroma prediction samples may be generated based on luma samples using a linear model. This case may be referred to as LM (Linear Model) mode.
- LM Linear Model
- a temporary prediction sample of the current block is derived based on the filtered surrounding reference samples, and at least one of the existing surrounding reference samples, that is, unfiltered surrounding reference samples, derived according to the intra prediction mode.
- a prediction sample of the current block may be derived by weighted sum of a reference sample and the temporary prediction sample. This case may be called PDPC (Position dependent intra prediction).
- a reference sample line having the highest prediction accuracy among the neighboring multi-reference sample lines of the current block may be selected, and a prediction sample may be derived using a reference sample positioned in the prediction direction from the corresponding line.
- information on the used reference sample line eg, intra_luma_ref_idx
- MRL multi-reference line intra prediction
- reference samples may be derived from a reference sample line directly adjacent to the current block, and in this case, information about the reference sample line may not be signaled.
- the current block may be divided into vertical or horizontal subpartitions, and intra prediction may be performed for each subpartition based on the same intra prediction mode.
- neighboring reference samples of intra prediction may be derived for each subpartition. That is, the reconstructed sample of the previous sub-partition in the encoding/decoding order may be used as a neighboring reference sample of the current sub-partition.
- the intra prediction mode for the current block is equally applied to the subpartitions, but by deriving and using neighboring reference samples in units of the subpartitions, intra prediction performance may be improved in some cases.
- This prediction method may be referred to as intra sub-partitions (ISP) or ISP-based intra prediction.
- intra prediction techniques may be referred to in various terms such as an intra prediction type or an additional intra prediction mode in distinction from a directional or non-directional intra prediction mode.
- the intra prediction technique may include at least one of the aforementioned LIP, LM, PDPC, MRL, and ISP.
- the general intra prediction method excluding specific intra prediction types such as LIP, LM, PDPC, MRL, and ISP may be referred to as a normal intra prediction type.
- the normal intra prediction type may be generally applied when the specific intra prediction type as described above is not applied, and prediction may be performed based on the aforementioned intra prediction mode. Meanwhile, post-processing filtering may be performed on the derived prediction samples as necessary.
- the intra prediction procedure may include determining an intra prediction mode/type, deriving a neighboring reference sample, and deriving an intra prediction mode/type based prediction sample. Also, a post-filtering step may be performed on the derived prediction samples as necessary.
- FIG. 6 is a flowchart illustrating a video/video encoding method based on intra prediction.
- the encoding method of FIG. 6 may be performed by the video encoding apparatus of FIG. 2. Specifically, step S610 may be performed by the intra prediction unit 185, and step S620 may be performed by the residual processing unit. Specifically, step S620 may be performed by the subtraction unit 115. Step S630 may be performed by the entropy encoding unit 190.
- the prediction information of step S630 may be derived by the intra prediction unit 185, and the residual information of step S630 may be derived by the residual processing unit.
- the residual information is information on the residual samples.
- the residual information may include information on quantized transform coefficients for the residual samples.
- the residual samples may be derived as transform coefficients through the transform unit 120 of the image encoding apparatus, and the transform coefficients may be derived as quantized transform coefficients through the quantization unit 130.
- Information about the quantized transform coefficients may be encoded by the entropy encoding unit 190 through a residual coding procedure.
- the image encoding apparatus may perform intra prediction on the current block (S610).
- the video encoding apparatus determines an intra prediction mode/type for the current block, derives neighboring reference samples of the current block, and then generates prediction samples in the current block based on the intra prediction mode/type and the neighboring reference samples. can do.
- the procedure of determining the intra prediction mode/type, deriving neighboring reference samples, and generating prediction samples may be simultaneously performed, or one procedure may be performed before the other procedure.
- FIG. 7 is a diagram illustrating an exemplary configuration of an intra prediction unit 185 according to the present disclosure.
- the intra prediction unit 185 of the video encoding apparatus may include an intra prediction mode/type determination unit 186, a reference sample derivation unit 187 and/or a prediction sample derivation unit 188.
- the intra prediction mode/type determiner 186 may determine an intra prediction mode/type for the current block.
- the reference sample derivation unit 187 may derive neighboring reference samples of the current block.
- the prediction sample derivation unit 188 may derive prediction samples of the current block.
- the intra prediction unit 185 may further include a prediction sample filter unit (not shown).
- the image encoding apparatus may determine a mode/type applied to the current block from among a plurality of intra prediction modes/types.
- the video encoding apparatus may compare RD costs for the intra prediction modes/types and determine an optimal intra prediction mode/type for the current block.
- the image encoding apparatus may perform a prediction sample filtering procedure.
- Predictive sample filtering may be referred to as post filtering. Some or all of the prediction samples may be filtered by the prediction sample filtering procedure. In some cases, the prediction sample filtering procedure may be omitted.
- the apparatus for encoding an image may generate residual samples for the current block based on prediction samples or filtered prediction samples (S620).
- the image encoding apparatus may derive the residual samples by subtracting the prediction samples from original samples of the current block. That is, the image encoding apparatus may derive the residual sample value by subtracting the corresponding predicted sample value from the original sample value.
- the image encoding apparatus may encode image information including information about the intra prediction (prediction information) and residual information about the residual samples (S630).
- the prediction information may include the intra prediction mode information and/or the intra prediction technique information.
- the image encoding apparatus may output the encoded image information in the form of a bitstream.
- the output bitstream may be delivered to an image decoding apparatus through a storage medium or a network.
- the residual information may include a residual coding syntax to be described later.
- the image encoding apparatus may transform/quantize the residual samples to derive quantized transform coefficients.
- the residual information may include information on the quantized transform coefficients.
- the image encoding apparatus may generate a reconstructed picture (including reconstructed samples and a reconstructed block). To this end, the image encoding apparatus may perform inverse quantization/inverse transformation on the quantized transform coefficients again to derive (modified) residual samples. The reason why the residual samples are transformed/quantized and then inverse quantized/inverse transformed is performed to derive residual samples identical to the residual samples derived from the image decoding apparatus.
- the image encoding apparatus may generate a reconstructed block including reconstructed samples for the current block based on the prediction samples and the (modified) residual samples. A reconstructed picture for the current picture may be generated based on the reconstructed block. As described above, an in-loop filtering procedure or the like may be further applied to the reconstructed picture.
- FIG. 8 is a flowchart illustrating a video/video decoding method based on intra prediction.
- the image decoding apparatus may perform an operation corresponding to an operation performed by the image encoding apparatus.
- the decoding method of FIG. 8 may be performed by the video decoding apparatus of FIG. 3.
- Dean systems S810 to S830 may be performed by the intra prediction unit 265, and the prediction information of step S810 and the residual information of step S840 may be obtained from the bitstream by the entropy decoding unit 210.
- the residual processing unit of the image decoding apparatus may derive residual samples for the current block based on the residual information (S840).
- the inverse quantization unit 220 of the residual processing unit derives transform coefficients by performing inverse quantization based on the quantized transform coefficients derived based on the residual information
- the inverse transform unit of the residual processing unit ( 230) may derive residual samples for the current block by performing inverse transform on the transform coefficients.
- Step S850 may be performed by the addition unit 235 or the restoration unit.
- the image decoding apparatus may derive an intra prediction mode/type for the current block based on the received prediction information (intra prediction mode/type information) (S810).
- the image decoding apparatus may derive neighboring reference samples of the current block (S820).
- the image decoding apparatus may generate prediction samples in the current block based on the intra prediction mode/type and the neighboring reference samples (S830).
- the image decoding apparatus may perform a prediction sample filtering procedure. Predictive sample filtering may be referred to as post filtering. Some or all of the prediction samples may be filtered by the prediction sample filtering procedure. In some cases, the prediction sample filtering procedure may be omitted.
- the image decoding apparatus may generate residual samples for the current block based on the received residual information (S840).
- the image decoding apparatus may generate reconstructed samples for the current block based on the prediction samples and the residual samples, and derive a reconstructed block including the reconstructed samples (S850).
- a reconstructed picture for the current picture may be generated based on the reconstructed block.
- an in-loop filtering procedure or the like may be further applied to the reconstructed picture.
- FIG. 9 is a diagram illustrating an exemplary configuration of an intra prediction unit 265 according to the present disclosure.
- the intra prediction unit 265 of the image decoding apparatus may include an intra prediction mode/type determination unit 266, a reference sample derivation unit 267, and a prediction sample derivation unit 268. .
- the intra prediction mode/type determiner 266 determines an intra prediction mode/type for the current block based on intra prediction mode/type information generated and signaled by the intra prediction mode/type determiner 186 of the image encoding apparatus.
- the reference sample deriving unit 266 may derive neighboring reference samples of the current block from the reconstructed reference region in the current picture.
- the prediction sample derivation unit 268 may derive prediction samples of the current block.
- the intra prediction unit 265 may further include a prediction sample filter unit (not shown).
- the intra prediction mode information may include, for example, flag information (ex. intra_luma_mpm_flag) indicating whether a most probable mode (MPM) is applied to the current block or a remaining mode is applied, and the When MPM is applied to the current block, the intra prediction mode information may further include index information (ex. intra_luma_mpm_idx) indicating one of the intra prediction mode candidates (MPM candidates).
- the intra prediction mode candidates (MPM candidates) may be composed of an MPM candidate list or an MPM list.
- the intra prediction mode information includes remaining mode information (ex. intra_luma_mpm_remainder) indicating one of the remaining intra prediction modes excluding the intra prediction mode candidates (MPM candidates).
- the image decoding apparatus may determine an intra prediction mode of the current block based on the intra prediction mode information.
- the MPM candidate modes may include an intra prediction mode and additional candidate modes of a neighboring block (eg, a left neighboring block and an upper neighboring block) of the current block.
- the intra prediction technique information may be implemented in various forms.
- the intra prediction technique information may include intra prediction technique index information indicating one of the intra prediction techniques.
- the intra prediction method information includes reference sample line information (ex. intra_luma_ref_idx) indicating whether the MRL is applied to the current block and, if applied, a reference sample line (eg, intra_luma_ref_idx), and the ISP is the current block.
- ISP flag information indicating whether it is applied to (ex. intra_subpartitions_mode_flag), ISP type information indicating the split type of subpartitions when the ISP is applied (ex.
- intra_subpartitions_split_flag flag information indicating whether or not PDPC is applied, or LIP application It may include at least one of flag information indicating whether or not.
- the ISP flag information may be referred to as an ISP application indicator.
- the intra prediction mode information and/or the intra prediction technique information may be encoded/decoded through the coding method described in this disclosure.
- the intra prediction mode information and/or the intra prediction method information may be encoded/decoded through entropy coding (ex. CABAC, CAVLC) based on a truncated (rice) binary code.
- an intra prediction mode applied to the current block may be determined using an intra prediction mode of a neighboring block.
- the image decoding apparatus constructs an mpm (most probable mode) list derived based on the intra prediction mode and additional candidate modes of the neighboring block (ex. left and/or upper neighboring block) of the current block, and received One of the mpm candidates in the mpm list can be selected based on the mpm index.
- the video decoding apparatus may select one of the remaining intra prediction modes that are not included in the mpm list based on the remaining intra prediction mode information.
- intra prediction mode applied to the current block is among mpm candidates (ie, is included in the mpm list) or in the remaining mode may be indicated based on an mpm flag (ex. intra_luma_mpm_flag).
- a value of 1 of the mpm flag may indicate that the intra prediction mode for the current block is in mpm candidates (mpm list), and a value of 0 of the mpm flag indicates that the intra prediction mode for the current block is in mpm candidates (mpm list). Can indicate none.
- the mpm index may be signaled in the form of an mpm_idx or intra_luma_mpm_idx syntax element
- the remaining intra prediction mode information may be signaled in the form of a rem_intra_luma_pred_mode or intra_luma_mpm_remainder syntax element.
- the remaining intra prediction mode information may indicate one of all intra prediction modes by indexing the remaining intra prediction modes not included in the mpm candidates (mpm list) in the order of prediction mode numbers.
- the intra prediction mode may be an intra prediction mode for a luma component (sample).
- the intra prediction mode information may include at least one of the mpm flag (ex.
- the MPM list may be referred to in various terms such as an MPM candidate list and candModeList.
- FIG. 10 is a flowchart illustrating an intra prediction mode signaling procedure in an image encoding apparatus.
- the apparatus for encoding an image may configure an MPM list for a current block (S1010).
- the MPM list may include candidate intra prediction modes (MPM candidates) that are likely to be applied to the current block.
- the MPM list may include intra prediction modes of neighboring blocks, or may further include specific intra prediction modes according to a predetermined method.
- the image encoding apparatus may determine an intra prediction mode of the current block (S1020).
- the video encoding apparatus may perform prediction based on various intra prediction modes, and may determine an optimal intra prediction mode by performing rate-distortion optimization (RDO) based thereon.
- RDO rate-distortion optimization
- the video encoding apparatus may determine the optimal intra prediction mode using only MPM candidates included in the MPM list, or further use the remaining intra prediction modes as well as the MPM candidates included in the MPM list. It is also possible to determine the intra prediction mode. Specifically, for example, if the intra prediction type of the current block is a specific type (eg, LIP, MRL, or ISP) other than the normal intra prediction type, the video encoding apparatus uses only the MPM candidates to determine the optimal intra prediction type.
- a specific type eg, LIP, MRL, or ISP
- the prediction mode can be determined. That is, in this case, the intra prediction mode for the current block may be determined only among the MPM candidates, and in this case, the mpm flag may not be encoded/signaled. In the case of the specific type, the video decoding apparatus may estimate that the mpm flag is 1 without separately signaling the mpm flag.
- the video encoding apparatus may generate an mpm index (mpm idx) indicating one of the MPM candidates. If the intra prediction mode of the current block is not in the MPM list, remaining intra prediction mode information indicating the same mode as the intra prediction mode of the current block is generated among the remaining intra prediction modes not included in the MPM list. can do.
- the image encoding apparatus may encode the intra prediction mode information and output it in the form of a bitstream (S1030).
- the intra prediction mode information may include the aforementioned mpm flag, mpm index, and/or remaining intra prediction mode information.
- the mpm index and the remaining intra prediction mode information are not signaled at the same time when indicating an intra prediction mode for one block with an alternative relationship. That is, when the mpm flag value is 1, the mpm index may be signaled, and when the mpm flag value is 0, the remaining intra prediction mode information may be signaled.
- the mpm flag is not signaled and its value is inferred as 1, and only the mpm index may be signaled. That is, in this case, the intra prediction mode information may include only the mpm index.
- S1020 is shown to be performed after S1010, but this is an example, and S1020 may be performed before S1010 or at the same time.
- 11 is a flowchart illustrating a procedure for determining an intra prediction mode in an image decoding apparatus.
- the image decoding apparatus may determine an intra prediction mode of the current block based on intra prediction mode information determined and signaled by the image encoding apparatus.
- the apparatus for decoding an image may acquire intra prediction mode information from a bitstream (S1110).
- the intra prediction mode information may include at least one of an mpm flag, an mpm index, and a remaining intra prediction mode.
- the video decoding apparatus may configure an MPM list (S1120).
- the MPM list is configured in the same way as the MPM list configured in the video encoding apparatus. That is, the MPM list may include intra prediction modes of neighboring blocks, or may further include specific intra prediction modes according to a predetermined method.
- S1120 is shown to be performed after S1110, but this is an example, and S1120 may be performed before S1110 or at the same time.
- the video decoding apparatus determines an intra prediction mode of the current block based on the MPM list and the intra prediction mode information (S1130). Step S1130 will be described in more detail with reference to FIG. 12.
- FIG. 12 is a flowchart for describing a procedure for deriving an intra prediction mode in more detail.
- Steps S1210 and S1220 of FIG. 12 may correspond to steps S1110 and S1120 of FIG. 11, respectively. Therefore, detailed descriptions of steps S1210 and S1220 are omitted.
- the image decoding apparatus may obtain intra prediction mode information from the bitstream, configure an MPM list (S1210 and S1220), and determine a predetermined condition (S1230). Specifically, as shown in FIG. 12, when the value of the mpm flag is 1 (Yes in S1230), the video decoding apparatus selects a candidate indicated by the mpm index among MPM candidates in the MPM list in the intra prediction mode of the current block. It can be derived as (S1240). As another example, when the value of the mpm flag is 0 (No in S1230), the video decoding apparatus selects the intra prediction mode indicated by the remany intra prediction mode information among the remaining intra prediction modes not included in the MPM list. The intra prediction mode of the block may be derived (S1250).
- the video decoding apparatus within the MPM list without checking the mpm flag A candidate indicated by the mpm index may be derived as an intra prediction mode of the current block (S1240).
- FIG. 13 is a diagram illustrating an intra prediction direction according to an embodiment of the present disclosure.
- the intra prediction mode may include two non-directional intra prediction modes and 33 directional intra prediction modes.
- the non-directional intra prediction modes may include a planar intra prediction mode and a DC intra prediction mode, and the directional intra prediction modes may include 2 to 34 intra prediction modes.
- the planar intra prediction mode may be referred to as a planner mode, and the DC intra prediction mode may be referred to as a DC mode.
- the intra prediction mode includes two non-directional intra prediction modes and 65 extended directional intra prediction. It can include modes.
- the non-directional intra prediction modes may include a planar mode and a DC mode, and the directional intra prediction modes may include 2 to 66 intra prediction modes.
- the extended intra prediction modes can be applied to blocks of all sizes, and can be applied to both a luma component (a luma block) and a chroma component (a chroma block).
- the intra prediction mode may include two non-directional intra prediction modes and 129 directional intra prediction modes.
- the non-directional intra prediction modes may include a planar mode and a DC mode, and the directional intra prediction modes may include 2 to 130 intra prediction modes.
- the intra prediction mode may further include a cross-component linear model (CCLM) mode for chroma samples in addition to the aforementioned intra prediction modes.
- CCLM cross-component linear model
- the CCLM mode can be divided into L_CCLM, T_CCLM, and LT_CCLM, depending on whether left samples are considered, upper samples are considered, or both for LM parameter derivation, and can be applied only to a chroma component.
- the intra prediction mode may be indexed, for example, as shown in Table 2 below.
- an intra prediction mode in order to capture an arbitrary edge direction presented in a natural video, includes 93 directions along with two non-directional intra prediction modes. It may include an intra prediction mode. Non-directional intra prediction modes may include planar mode and DC mode.
- the directional intra prediction mode may include an intra prediction mode consisting of times 2 to 80 and -1 to -14 as indicated by the arrows in FIG. 14.
- the planner mode may be indicated as INTRA_PLANAR, and the DC mode may be indicated as INTRA_DC.
- the directional intra prediction mode may be expressed as INTRA_ANGULAR-14 to INTRA_ANGULAR-1 and INTRA_ANGULAR2 to INTRA_ANGULAR80.
- a method of deriving a prediction sample of a chroma component block according to the present disclosure will be described in detail.
- intra prediction When intra prediction is performed on the current block, prediction on a luma component block (luma block) of the current block and prediction on a chroma component block (chroma block) may be performed. In this case, a chroma component (chroma block) can be predicted.
- the intra prediction mode may be set separately from the intra prediction mode for the luma component (luma block).
- an intra prediction mode (intra chroma prediction mode) for a chroma block may be indicated based on intra chroma prediction mode information, and the intra chroma prediction mode information may be signaled in the form of an intra_chroma_pred_mode syntax element.
- the intra-chroma prediction mode information may indicate one of a planar mode, a DC mode, a vertical mode, a horizontal mode, a derived mode (DM), and a CCLM mode.
- the intra prediction mode includes two non-directional intra prediction modes and 33 directional intra prediction modes
- the planar mode is an intra prediction mode of 0
- the DC mode is an intra prediction mode of 1
- the vertical mode when the intra prediction mode includes two non-directional intra prediction modes and 33 directional intra prediction modes, the planar mode is an intra prediction mode of 0, the DC mode is an intra prediction mode of 1, and the vertical mode.
- the horizontal mode may represent the 10th intra prediction mode.
- the intra prediction mode includes two non-directional intra prediction modes and 65 directional intra prediction modes
- the planar mode is an intra prediction mode of 0
- the DC mode is an intra prediction mode of 1
- the vertical mode May represent the 50th intra prediction mode
- the horizontal mode may represent the 18th intra prediction mode.
- DM can also be called direct mode.
- CCLM can be called LM.
- DM and CCLM are dependent intra prediction modes for predicting a chroma block using information of a luma block.
- the DM may represent a mode in which an intra prediction mode identical to an intra prediction mode for the luma component (a luma block) is applied as an intra prediction mode for the chroma component (chroma block).
- the CCLM subsamples the reconstructed samples of the luma block in the process of generating the prediction block for the chroma block, and then applies the CCLM parameters ⁇ and ⁇ to the subsampled samples. Intra prediction mode used as prediction samples of may be indicated.
- the intra prediction mode of the current chroma block may be derived as the intra prediction mode of the corresponding luma block.
- the intra prediction mode at a predetermined position of the corresponding luma block may be used as the intra prediction mode of the current chroma block.
- 15 is a diagram illustrating a predetermined position for deriving an intra prediction mode of a current chroma block in the case of the DM mode.
- a chroma block is vertically binary divided, and a current chroma block may be a block of a hatched area.
- the luma block corresponding to the current chroma block may be a block of a shaded area within the luma block.
- an intra prediction mode (intra chroma prediction mode) of a current chroma block predicted by DM may be derived to an intra prediction mode (intra luma prediction mode) at a predetermined position in a corresponding luma block.
- the intra prediction mode of the block covering the lower right center sample (center position) CR in the corresponding luma block may be determined as the intra prediction mode of the current chroma block.
- the predetermined position is not limited to the center position, and may be another position in the corresponding luma block, such as, for example, the upper left position TL.
- MDM Direct Modes
- the multiple DM is a mode in which the single DM mode is extended to a plurality of modes, and a DM candidate list including a plurality of DM modes is constructed to induce an intra prediction mode of the current chroma block, and is included in the DM candidate list.
- One of the candidates may be derived as an intra prediction mode of the current chroma block.
- the DM candidate list may include a plurality of DM candidates below.
- -Default DM candidate mode vertical mode, horizontal mode, 2, 34, 66, 10, 26 modes (in case of 65 directional modes)
- the intra prediction modes of the chroma block may be encoded using a total of 8 intra prediction modes.
- the eight intra prediction modes may include conventional five intra prediction modes and a cross-component linear model mode (CCLM) mode(s).
- CCLM cross-component linear model mode
- Whether the CCLM is available may be determined based on information signaled at a higher level (eg, sps_cclm_enabled_flag transmitted at a sequence level).
- the intra prediction mode of the chroma block may be derived based on the intra chroma prediction mode information (intra_chroma_pred_mode) and/or the intra prediction mode (IntraPredModeY) of the corresponding luma block.
- the intra prediction mode of the corresponding luma block may be determined as an intra prediction mode of the luma block that covers the current block or the lower right center sample (center position) of the chroma block.
- the center of the lower right sample position is derived as (xCb + cbWidth / 2, yCb + cbHeight / 2), where (xCb, yCb) means the coordinates of the top-left sample of the corresponding luma block.
- cbWidth and cbHeight mean the width and height of the corresponding luma block, respectively.
- the intra_chroma_pred_mode 0 (planner mode)
- the intra_chroma_pred_mode 1
- the intra prediction mode of the chroma block may be determined as 50 (vertical mode).
- the intra_chroma_pred_mode 2
- the intra prediction mode of the chroma block may be determined as 18 (horizontal mode)
- the intra_chroma_pred_mode is 3
- the intra prediction mode of the chroma block may be determined as 1 (DC mode).
- the intra prediction mode of the chroma block may be determined to have the same value as the intra prediction mode of the corresponding luma block. That is, when the intra_chroma_pred_mode is 4, it indicates that the intra prediction mode of the chroma block is derived as DM.
- the indexes of the intra prediction mode (IntraPredModeC[ xCb ][ yCb ]) of the chroma block derived based on Table 3 may correspond to the indexes of the intra prediction mode shown in Table 2 above.
- the intra prediction mode of the chroma block is determined to be 66 instead of the aforementioned intra prediction mode (planner mode, vertical mode, horizontal mode, DC mode) according to the IntraPredModeY value.
- an intra_chroma_pred_mode value of 0 indicates a planar mode.
- IntraPredModeY is 0 (planar mode)
- the intra prediction mode of the chroma block is determined to be 66.
- the intra_chroma_pred_mode value is determined to be 4 indicating DM, not 0. Accordingly, when the intra_chroma_pred_mode value is 0 to 3, the case where the intra prediction mode of the chroma block is determined to be 66 does not substantially occur. That is, when the intra_chroma_pred_mode is 0 to 3, the intra prediction mode of the chroma block may be derived from one of a planar mode, a vertical mode, a horizontal mode, and a DC mode based on the intra_chroma_pred_mode value.
- the intra prediction mode of the chroma block may be derived based on an intra_chroma_pred_mode value and an intra prediction mode of a corresponding luma block.
- the present disclosure is not limited to the above-described example, and even when the intra_chroma_pred_mode is 0 to 3, the intra prediction mode of the chroma block is derived based on intra-chroma prediction mode information (eg, intra_chroma_pred_mode) and the intra prediction mode of the corresponding luma block. Examples may be included.
- Table 4 is a case where the CCLM is available, and includes modes for signaling the CCLM mode in addition to the modes of Table 3.
- intra_chroma_pred_mode when intra_chroma_pred_mode is 4 to 6, INTRA_LT_CCLM, INTRA_L_CCLM, and INTRA_T_CCLM may be indicated, respectively.
- the cases where the intra_chroma_pred_mode is 0 to 3 and 7 may correspond to the case where the intra_chroma_pred_mode is 0 to 4 in Table 3, respectively. That is, when the intra_chroma_pred_mode is 7, it indicates that the intra prediction mode of the chroma block is derived as DM.
- an intra prediction mode of a chroma block may be derived based on intra-chroma prediction mode information (intra_chroma_pred_mode) and/or an intra prediction mode of a corresponding luma block.
- intra-chroma prediction mode information indicates the DM mode
- the intra prediction mode of the chroma block may be determined to be the same as the intra prediction mode of the corresponding luma block.
- FIG. 16 is a flowchart illustrating a conventional method of deriving an intra prediction mode of a chroma block based on a corresponding luma block.
- an intra luma prediction mode of a corresponding luma block may be obtained (S1620).
- the intra luma prediction mode may be obtained, for example, from a predetermined position (center position) in the corresponding luma block, as described above.
- the intra prediction mode of the current chroma block may be derived by referring to Table 3 or Table 4 based on the intra chroma prediction mode information and/or the intra luma prediction mode obtained from the bitstream. (S1630). Thereafter, intra prediction on the current chroma block may be performed using the derived intra chroma prediction mode to generate a prediction block of the current chroma block (S1640).
- the intra prediction mode of the current chroma block may be derived with the same value as the intra luma prediction mode of the corresponding luma block.
- the intra prediction mode of the current chroma block is derived from one of the planar mode, DC mode, vertical mode, horizontal mode, and CCLM mode based on the intra chroma prediction mode information. I can.
- the conventional method described with reference to FIG. 16 does not take into account the case where the intra luma prediction mode of the corresponding luma block does not exist.
- a luma block and a chroma block in one CTU may be divided into the same block tree structure (SINGLE_TREE) or a separate block tree structure (DUAL_TREE).
- the luma block And the corresponding chroma blocks may be encoded in the same prediction mode or different prediction modes. That is, the luma block corresponding to the intra predicted chroma block may be intra predicted or may be encoded in a different prediction mode.
- the intra luma prediction mode of the corresponding luma block cannot be obtained in step S1620, and accordingly, for example, the intra prediction mode of the chroma block intra-predicted using the DM mode cannot be derived. Problems can arise.
- FIG. 17 is a flowchart illustrating an embodiment of the present disclosure in which an intra prediction mode of a chroma block is derived based on a corresponding luma block.
- the problem of the above-described conventional method can be solved by using the default intra prediction mode.
- an intra-predicted current chroma block is input (S1710). After that, it may be determined whether an intra luma prediction mode of a corresponding luma block required to derive an intra prediction mode of the current chroma block is available (S1720). As described above, the intra luma prediction mode of the corresponding luma block may be obtained from a predetermined position (eg, a center position) of the corresponding luma block. Accordingly, the determination of step S1720 may be performed by confirming the prediction mode of the predetermined position of the corresponding luma block.
- the prediction mode of the predetermined position of the corresponding luma block is an intra mode
- the prediction mode of the predetermined position of the corresponding luma block is a mode other than the intra mode (eg, IBC mode)
- the determination of step S1720 may be determined based on whether the predetermined position of the corresponding luma block has an intra luma prediction mode.
- step S1720 if it is determined that the intra luma prediction mode is available, steps S1730, S1740, and S1760 may be sequentially performed. Steps S1730, S1740, and S1760 correspond to steps S1620, S1630, and S1640 of FIG. 16, respectively, and detailed descriptions are omitted.
- a default intra prediction mode may be used. That is, the intra prediction mode of the current chroma block may be derived based on the intra chroma prediction mode information and/or the default intra prediction mode (S1750). In this case, a default intra prediction mode may be used instead of an intra luma prediction mode that is not available. For example, when the intra chroma prediction mode information indicates DM, the intra prediction mode of the current chroma block may be derived as a default intra prediction mode.
- the intra prediction mode of the current chroma block is one of a planar mode, a DC mode, a vertical mode, a horizontal mode, and a CCLM mode based on the intra chroma prediction mode information. Can be derived. Thereafter, a prediction block of the current chroma block may be generated by performing intra prediction on the current chroma block using the derived intra chroma prediction mode (S1760).
- a DC mode or a planar mode may be used as a default intra prediction mode.
- the present invention is not limited thereto, and a predetermined intra prediction mode or an intra prediction mode signaled through a bitstream may be used as the default intra prediction mode.
- FIG. 18 is a flowchart illustrating another embodiment of the present disclosure in which an intra prediction mode of a chroma block is derived based on a corresponding luma block.
- the problem of the conventional method described above can be solved by using the default intra prediction mode. Further, according to the embodiment shown in FIG. 18, determination of whether the intra prediction mode of the corresponding luma block is available is performed only when the tree structure of the current block is a dual tree.
- an intra-predicted current chroma block is input (S1810). After that, it is determined whether the tree structure of the current block is a dual tree structure (S1815). If the tree structure of the current block is not a dual tree structure, i.e., a single tree structure, the chroma block and the corresponding luma block can be regarded as intra-predicted identically, so that the intra luma prediction mode of the corresponding luma block is available. Can be judged. Therefore, in this case, the determination of step S1820 may be skipped. In other words, when the tree structure of the current block is a single tree structure, steps S1830, S1840, and S1860 are immediately sequentially performed to generate a prediction block of the current chroma block.
- step S1815 if the tree structure of the current block is a dual tree structure, the determination of step S1820 may be performed, and the processing according to the determination result of step S1820 is the same as described with reference to FIG. 17, and thus a repetitive description is omitted. . That is, steps S1820 to S1860 may correspond to each of steps S1720 to S1760 of FIG. 17.
- steps S1815 and S1820 of FIG. 18 may be a specific embodiment of step S1720 of FIG. 17.
- 19 is a flowchart illustrating another embodiment of the present disclosure for deriving an intra prediction mode of a chroma block based on a corresponding luma block.
- the problem of the conventional method described above can be solved by using the default intra prediction mode. Further, according to the embodiment shown in FIG. 19, the determination of whether the intra prediction mode of the corresponding luma block is available is performed only when the tree structure of the current block is a dual tree and IBC is allowed.
- an intra-predicted current chroma block is input (S1910). After that, it is determined whether the tree structure of the current block is a dual tree structure (S1915). When the tree structure of the current block is not a dual tree structure, i.e., a single tree structure, as described with reference to FIG. 18, the intra luma prediction mode of the corresponding luma block can be considered to be available, so steps S1917 and steps S1917 The judgment of S1920 may be skipped. Accordingly, in the case of a single tree structure, a prediction block of a current chroma block may be generated by sequentially performing steps S1930, S1940, and S1960 immediately.
- step S1915 when the tree structure of the current block is a dual tree structure, it may be determined whether IBC is allowed (S1917). Whether IBC is allowed may be determined based on information (eg, sps_ibc_enabled_flag) signaled at a higher level (eg, sequence) of the current block. For example, if sps_ibc_enabled_flag is 1, it may be determined that IBC is allowed, and if sps_ibc_enabled_flag is 0, it may be determined that IBC is not allowed.
- information eg, sps_ibc_enabled_flag
- the current block belongs to an I slice/tile group. Assuming that the prediction of the block included in the I slice/tile group is limited to intra prediction and IBC prediction, the current block may be predicted by either intra prediction or IBC prediction. Therefore, when IBC is not allowed, it may be determined that the current block is intra-predicted.
- step S1917 if it is determined in step S1917 that IBC is not allowed, since the corresponding luma block can be considered to be intra-predicted, the determination of step S1920 may be skipped, and steps S1930, S1940 and S1960 may be immediately performed. If it is determined in step S1917 that IBC is allowed, since the corresponding luma block may be intra prediction or IBC prediction, in this case, the determination of step S1920 may be performed.
- the processing according to the determination result in step S1920 is the same as that described with reference to FIG. 17, so a repetitive description is omitted. That is, steps S1920 to S1960 may correspond to each of steps S1720 to S1760 of FIG. 17.
- step S1917 since it is assumed that only intra prediction or IBC prediction is possible for blocks belonging to the I slice/tile group, only whether or not IBC is allowed is determined in step S1917. However, when a third prediction mode other than intra prediction or IBC prediction is possible for blocks belonging to the I slice/tile group, not only whether IBC is allowed, but also whether the third prediction mode is allowed may be performed in step S1917. have. In this case, step S1920 may be skipped only when both the IBC and the third prediction mode are not allowed. That is, when either of the IBC and the third prediction mode is allowed, step S1920 and subsequent processing according thereto may be performed as described above.
- steps S1915, S1917, and S1920 of FIG. 19 may be a specific embodiment of step S1720 of FIG. 17.
- the type of the slice/tile group of the current block may be determined.
- the type of the slice/tile group of the current block is P or B slice/tile group
- the tree structure of the current block is determined as a single tree structure, so it is difficult to determine whether the tree structure of the current block is a dual tree structure (S1815 or S1915). It doesn't have to be done. Accordingly, in the case of a P or B slice/tile group, a corresponding intra luma prediction mode may be obtained immediately and an intra chroma prediction mode may be derived based on the acquired intra luma prediction mode.
- the tree structure of the current block may be a single tree structure or a dual tree structure, so the steps of FIGS. 18 and 19 including S1815 or S1915 Can be performed.
- 20 is a flowchart illustrating an embodiment of the present disclosure in which an intra prediction mode of a current block is derived based on a corresponding block.
- a current block to be encoded/decoded may be input (S2010).
- the current block is an intra-prediction block, and the intra prediction mode of the current block is not signaled directly and may be derived from the intra prediction mode of the corresponding block.
- the current block may be a chroma block.
- a corresponding block corresponding to the current block is specified, and it may be determined whether an intra prediction mode of the corresponding block is available (S2020).
- the corresponding block may be a corresponding luma block corresponding to a chroma block. Step S2020 may be performed based on determining whether the corresponding block is intra predicted.
- the prediction mode of the corresponding block may be performed based on determination of whether a mode other than an intra mode (eg, an IBC mode) is determined.
- step S2020 may be performed based on determining whether the corresponding block has an intra prediction mode. For example, when the corresponding block is intra predicted or has an intra prediction mode, it may be determined that the intra prediction mode of the corresponding block is available. Otherwise, when the corresponding block is predicted in a mode other than the intra mode or does not have an intra prediction mode, it may be determined that the intra prediction mode of the corresponding block is not available.
- step S2020 determination of the type of the slice/tile group including the current block, determination of the tree structure of the current block, and whether IBC or the third prediction mode is allowed in addition to intra prediction for the current block. It may include at least one of the judgments about.
- the current block and the corresponding block are illustrated as a chroma block and a corresponding luma block, but are not limited thereto.
- the current block may be a luma block and the corresponding block may be a corresponding chroma block.
- the current block may be the first color component block and the corresponding block may be the second color component block.
- the first color component may be, for example, one of a luma component and a plurality of chroma components
- the second color component may be a color component different from the first color component.
- the first color component block may be a first chroma component block
- the second color component block may be a second chroma component block.
- step S2020 if the intra prediction mode of the corresponding block is available, the intra prediction mode of the corresponding block is obtained (S2030), and the intra prediction mode of the current block is determined based on the intra prediction mode of the corresponding block. It can be derived (S2040).
- step S2020 if the intra prediction mode of the corresponding block is not available, a default intra prediction mode is determined (S2050), and an intra prediction mode of the current block may be derived based on the default intra prediction mode (S2060).
- a default intra prediction mode in step S2050 a DC mode or a planar mode may be used.
- the present invention is not limited thereto, and a predetermined intra prediction mode or an intra prediction mode signaled through a bitstream may be used as the default intra prediction mode.
- the intra prediction mode of the current block when the intra prediction mode of the current block is derived from the intra prediction mode of the corresponding block, when the intra prediction mode of the corresponding block does not exist, the intra prediction mode of the current block is determined based on the default intra prediction mode. Since it can be derived, intra prediction for the current block can be effectively performed even when the intra prediction mode of the corresponding block does not exist.
- FIG. 21 is a flowchart illustrating still another embodiment of the present disclosure in which an intra prediction mode of a chroma block is derived and a chroma block is encoded based on a corresponding luma block.
- FIG. 21 relates to an operation in an image encoding apparatus corresponding to the embodiment described with reference to FIG. 17.
- a current chroma block is input (S2110).
- the image encoding apparatus may determine an intra prediction mode of the current chroma block.
- the image encoding apparatus may perform intra prediction on all or at least some of the intra prediction modes applicable to the current chroma block, and determine an optimal mode as the intra prediction mode of the current chroma block. Accordingly, the apparatus for encoding an image needs to determine whether to apply the DM mode to the current chroma block, and for this purpose, it is necessary to obtain an intra prediction mode of a corresponding luma block.
- the image encoding apparatus may first determine whether the intra luma prediction mode of the corresponding luma block is available (S2120).
- the determination of step S2120 is substantially the same as the determination of step S1720, so a repetitive description is omitted.
- determination of the type of the slice/tile group including the current block, determination of the tree structure of the current block, and whether IBC or the third prediction mode is allowed in addition to intra prediction for the current block. It may include at least one of the judgments about.
- step S2120 when it is determined that the intra luma prediction mode is available, the video encoding apparatus acquires the intra luma prediction mode from a predetermined position of the corresponding luma block (S2130), and includes the intra luma prediction mode.
- a prediction mode may be derived (S2140).
- the apparatus for encoding an image may select one intra prediction mode from among one or more intra prediction modes applicable to a current chroma block, including the intra luma prediction mode, by comparing the aforementioned RD-cost.
- the method of selecting the intra prediction mode of the current chroma block by the video encoding apparatus is not limited to the above example.
- intra prediction may be performed on the current chroma block and a prediction block may be generated based on the derived intra prediction mode.
- the intra prediction mode of the current chroma block may be encoded based on the intra luma prediction mode (S2160). For example, when the intra luma prediction mode is determined as the intra prediction mode of the current chroma block, the intra chroma prediction mode information may be encoded as a value indicating DM.
- the intra prediction mode of the current chroma block may be derived by using the default intra prediction mode instead of the intra luma prediction mode (S2150).
- intra prediction may be performed on the current chroma block and a prediction block may be generated based on the derived intra prediction mode.
- the intra prediction mode of the current chroma block may be encoded based on the default intra prediction mode (S2160).
- a DC mode or a planar mode may be used as a default intra prediction mode.
- the present invention is not limited thereto, and a predetermined intra prediction mode is used as the default intra prediction mode, or a default intra prediction mode is determined in the video encoding apparatus, and information on the determined default intra prediction mode is signaled through a bitstream. It could be.
- Exemplary methods of the present disclosure are expressed as a series of operations for clarity of explanation, but this is not intended to limit the order in which steps are performed, and each step may be performed simultaneously or in a different order if necessary.
- the illustrative steps may include additional steps, other steps may be included excluding some steps, or may include additional other steps excluding some steps.
- an image encoding apparatus or an image decoding apparatus performing a predetermined operation may perform an operation (step) of confirming an execution condition or situation of the operation (step). For example, when it is described that a predetermined operation is performed when a predetermined condition is satisfied, the video encoding apparatus or the video decoding apparatus performs an operation to check whether the predetermined condition is satisfied, and then performs the predetermined operation. I can.
- various embodiments of the present disclosure may be implemented by hardware, firmware, software, or a combination thereof.
- one or more ASICs Application Specific Integrated Circuits
- DSPs Digital Signal Processors
- DSPDs Digital Signal Processing Devices
- PLDs Programmable Logic Devices
- FPGAs Field Programmable Gate Arrays
- general purpose It may be implemented by a processor (general processor), a controller, a microcontroller, a microprocessor, or the like.
- the image decoding device and the image encoding device to which the embodiment of the present disclosure is applied include a multimedia broadcasting transmission/reception device, a mobile communication terminal, a home cinema video device, a digital cinema video device, a surveillance camera, a video chat device, and a real-time communication device such as video communication.
- Mobile streaming devices storage media, camcorders, video-on-demand (VoD) service providers, OTT video (Over the top video) devices, Internet streaming service providers, three-dimensional (3D) video devices, video telephony video devices, and medical use. It may be included in a video device or the like, and may be used to process a video signal or a data signal.
- an OTT video (Over the top video) device may include a game console, a Blu-ray player, an Internet-connected TV, a home theater system, a smartphone, a tablet PC, and a digital video recorder (DVR).
- DVR digital video recorder
- FIG. 22 is a diagram illustrating a content streaming system to which an embodiment of the present disclosure can be applied.
- a content streaming system to which an embodiment of the present disclosure is applied may largely include an encoding server, a streaming server, a web server, a media storage device, a user device, and a multimedia input device.
- the encoding server serves to generate a bitstream by compressing content input from multimedia input devices such as smartphones, cameras, camcorders, etc. into digital data, and transmits it to the streaming server.
- multimedia input devices such as smartphones, cameras, camcorders, etc. directly generate bitstreams
- the encoding server may be omitted.
- the bitstream may be generated by an image encoding method and/or an image encoding apparatus to which an embodiment of the present disclosure is applied, and the streaming server may temporarily store the bitstream in a process of transmitting or receiving the bitstream.
- the streaming server may transmit multimedia data to a user device based on a user request through a web server, and the web server may serve as an intermediary for notifying the user of a service.
- the web server transmits the request to the streaming server, and the streaming server may transmit multimedia data to the user.
- the content streaming system may include a separate control server, and in this case, the control server may play a role of controlling a command/response between devices in the content streaming system.
- the streaming server may receive content from a media storage and/or encoding server. For example, when content is received from the encoding server, the content may be received in real time. In this case, in order to provide a smooth streaming service, the streaming server may store the bitstream for a predetermined time.
- Examples of the user device include a mobile phone, a smart phone, a laptop computer, a digital broadcasting terminal, a personal digital assistant (PDA), a portable multimedia player (PMP), a navigation system, a slate PC, and Tablet PC, ultrabook, wearable device, for example, smartwatch, smart glass, head mounted display (HMD)), digital TV, desktop There may be computers, digital signage, etc.
- PDA personal digital assistant
- PMP portable multimedia player
- HMD head mounted display
- TV desktop
- desktop There may be computers, digital signage, etc.
- Each server in the content streaming system may be operated as a distributed server, and in this case, data received from each server may be distributedly processed.
- the scope of the present disclosure is software or machine-executable instructions (e.g., operating systems, applications, firmware, programs, etc.) that cause an operation according to the method of various embodiments to be executed on a device or computer, and such software or It includes a non-transitory computer-readable medium (non-transitory computer-readable medium) which stores instructions and the like and is executable on a device or a computer.
- a non-transitory computer-readable medium non-transitory computer-readable medium
- An embodiment according to the present disclosure may be used to encode/decode an image.
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Abstract
Description
MttSplitMode | mtt_split_cu_vertical_flag | mtt_split_cu_binary_flag |
SPLIT_TT_HOR | 0 | 0 |
SPLIT_BT_HOR | 0 | 1 |
SPLIT_TT_VER | 1 | 0 |
SPLIT_BT_VER | 1 | 1 |
Intra prediction mode | Associated name |
0 | INTRA_PLANAR |
1 | INTRA_DC |
2..66 | INTRA_ANGULAR2..INTRA_ANGULAR66 |
81..83 | INTRA_LT_CCLM, INTRA_L_CCLM, INTRA_T_CCLM |
intra_chroma_pred_mode[xCb][yCb] | IntraPredModeY[xCb + cbWidth/2][yCb + cbHeight/2] | ||||
0 | 50 | 18 | 1 | X ( 0 <= X <= 66 ) | |
0 | 66 | 0 | 0 | 0 | 0 |
1 | 50 | 66 | 50 | 50 | 50 |
2 | 18 | 18 | 66 | 18 | 18 |
3 | 1 | 1 | 1 | 66 | 1 |
4 | 0 | 50 | 18 | 1 | X |
intra_chroma_pred_mode[xCb][yCb] | IntraPredModeY[xCb + cbWidth/2][yCb + cbHeight/2] | ||||
0 | 50 | 18 | 1 | X ( 0 <= X <= 66 ) | |
0 | 66 | 0 | 0 | 0 | 0 |
1 | 50 | 66 | 50 | 50 | 50 |
2 | 18 | 18 | 66 | 18 | 18 |
3 | 1 | 1 | 1 | 66 | 1 |
4 | 81 | 81 | 81 | 81 | 81 |
5 | 82 | 82 | 82 | 82 | 82 |
6 | 83 | 83 | 83 | 83 | 83 |
7 | 0 | 50 | 18 | 1 | X |
Claims (15)
- 영상 복호화 장치에 의해 수행되는 영상 복호화 방법으로서,현재 크로마 블록의 예측에 관한 정보에 기반하여, 상기 현재 크로마 블록에 인트라 예측이 적용되는지 여부를 결정하는 단계;상기 현재 크로마 블록에 인트라 예측이 적용되는 경우, 상기 현재 크로마 블록에 대응하는 대응 루마 블록의 인트라 예측 모드 및 상기 현재 크로마 블록의 인트라 크로마 예측 모드 정보에 기반하여 상기 현재 크로마 블록의 인트라 예측 모드를 도출하는 단계; 및상기 현재 크로마 블록의 인트라 예측 모드에 기반하여 인트라 예측을 수행함으로써, 상기 현재 크로마 블록에 대한 예측 블록을 생성하는 단계를 포함하고,상기 대응 루마 블록의 인트라 예측 모드가 존재하지 않는 경우, 상기 현재 크로마 블록의 인트라 예측 모드는 디폴트 인트라 예측 모드에 기반하여 도출되는 영상 복호화 방법.
- 제1항에 있어서,상기 현재 크로마 블록의 인트라 예측 모드를 도출하는 단계는, 상기 대응 루마 블록의 소정 위치의 예측 방법을 판단하는 단계를 포함하는 영상 복호화 방법.
- 제2항에 있어서,상기 대응 루마 블록의 소정 위치의 예측 방법이 인트라 예측인 경우, 상기 현재 크로마 블록의 인트라 예측 모드는 상기 대응 루마 블록의 소정 위치의 인트라 예측 모드에 기반하여 도출되고,상기 대응 루마 블록의 소정 위치의 예측 방법이 인트라 예측이 아닌 경우, 상기 현재 크로마 블록의 인트라 예측 모드는 상기 디폴트 인트라 예측 모드에 기반하여 도출되는 영상 복호화 방법.
- 제2항에 있어서,상기 대응 루마 블록의 소정 위치의 예측 방법이 IBC(Intra Block Copy) 예측인 경우, 상기 현재 크로마 블록의 인트라 예측 모드는 상기 디폴트 인트라 예측 모드에 기반하여 도출되는 영상 복호화 방법.
- 제2항에 있어서,상기 소정 위치는 상기 대응 루마 블록의 중심 위치인 영상 복호화 방법.
- 제1항에 있어서,상기 디폴트 인트라 예측 모드는 Planar 모드 또는 DC 모드인 영상 복호화 방법.
- 제1항에 있어서,상기 현재 크로마 블록의 트리 구조는 듀얼 트리(DUAL_TREE) 구조인 영상 복호화 방법.
- 제1항에 있어서,상기 현재 크로마 블록의 인트라 예측 모드 정보가 DM(Direct Mode) 모드를 나타내고, 상기 대응 루마 블록의 인트라 예측 모드가 존재하면, 상기 현재 크로마 블록의 인트라 예측 모드는 상기 대응 루마 블록의 인트라 예측 모드로 도출되고,상기 현재 크로마 블록의 인트라 예측 모드 정보가 DM 모드를 나타내고, 상기 대응 루마 블록의 인트라 예측 모드가 존재하지 않으면, 상기 현재 크로마 블록의 인트라 예측 모드는 상기 디폴트 인트라 예측 모드로 도출되는 영상 복호화 방법.
- 메모리 및 적어도 하나의 프로세서를 포함하는 영상 복호화 장치로서,상기 적어도 하나의 프로세서는현재 크로마 블록의 예측에 관한 정보에 기반하여, 상기 현재 크로마 블록에 인트라 예측이 적용되는지 여부를 결정하고,상기 현재 크로마 블록에 인트라 예측이 적용되는 경우, 상기 현재 크로마 블록에 대응하는 대응 루마 블록의 인트라 예측 모드 및 상기 현재 크로마 블록의 인트라 크로마 예측 모드 정보에 기반하여 상기 현재 크로마 블록의 인트라 예측 모드를 도출하고,상기 현재 크로마 블록의 인트라 예측 모드에 기반하여 인트라 예측을 수행함으로써, 상기 현재 크로마 블록에 대한 예측 블록을 생성하며,상기 대응 루마 블록의 인트라 예측 모드가 존재하지 않는 경우, 상기 현재 크로마 블록의 인트라 예측 모드는 디폴트 인트라 예측 모드에 기반하여 도출되는 영상 복호화 장치.
- 영상 부호화 장치에 의해 수행되는 영상 부호화 방법으로서,현재 크로마 블록에 인트라 예측이 적용되는지 여부를 결정하는 단계;상기 현재 크로마 블록에 인트라 예측이 적용되는 경우, 상기 현재 크로마 블록에 대응하는 대응 루마 블록의 인트라 예측 모드에 기반하여 상기 현재 크로마 블록의 인트라 예측 모드를 도출하는 단계;상기 현재 크로마 블록의 인트라 예측 모드에 기반하여 인트라 예측을 수행함으로써, 상기 현재 크로마 블록에 대한 예측 블록을 생성하는 단계; 및상기 대응 루마 블록의 인트라 예측 모드에 기반하여 상기 현재 크로마 블록의 인트라 예측 모드를 부호화하는 단계를 포함하고,상기 대응 루마 블록의 인트라 예측 모드가 존재하지 않는 경우, 상기 현재 크로마 블록의 인트라 예측 모드는 디폴트 인트라 예측 모드에 기반하여 도출되는 영상 부호화 방법.
- 제10항에 있어서,상기 현재 크로마 블록의 인트라 예측 모드를 도출하는 단계는, 상기 대응 루마 블록의 소정 위치의 예측 방법을 판단하는 단계를 포함하는 영상 부호화 방법.
- 제11항에 있어서,상기 대응 루마 블록의 소정 위치의 예측 방법이 인트라 예측인 경우, 상기 현재 크로마 블록의 인트라 예측 모드는 상기 대응 루마 블록의 소정 위치의 인트라 예측 모드에 기반하여 도출되고,상기 대응 루마 블록의 소정 위치의 예측 방법이 인트라 예측이 아닌 경우, 상기 현재 크로마 블록의 인트라 예측 모드는 상기 디폴트 인트라 예측 모드에 기반하여 도출되는 영상 부호화 방법.
- 제11항에 있어서,상기 소정 위치는 상기 대응 루마 블록의 중심 위치인 영상 부호화 방법.
- 제10항에 있어서,상기 디폴트 인트라 예측 모드는 Planar 모드 또는 DC 모드인 영상 부호화 방법.
- 제10항의 영상 부호화 방법에 의해 생성된 비트스트림을 전송하는 방법.
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EP3941046A4 (en) | 2022-12-21 |
JP7410168B2 (ja) | 2024-01-09 |
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US11770537B2 (en) | 2023-09-26 |
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