RU2814221C2 - Image or video encoding based on palette mode - Google Patents

Abstract

FIELD: video or image encoding.

SUBSTANCE: invention relates to video or image encoding, in particular to a palette mode based encoding method. It is proposed that a quantisation parameter used in a process of scaling a quantised transition value in a palette mode, can be output based on information of minimum quantization parameter related to conversion skipping mode, wherein the information on the minimum quantisation parameter for the transform skip mode is a syntax element obtained from a sequence parameter set (SPS) included in the image information. Accordingly, the amount of data required for signalling for video/image coding can be reduced, and transition coding in palette mode can be efficiently performed.

EFFECT: improved encoding efficiency for screen content, such as computer-generated video, which contains a significant amount of text and graphics.

3 cl, 11 dwg, 18 tbl

Description

Prerequisites for disclosure

Technical field

[1] The present disclosure relates to video or image encoding and, for example, to a palette mode-based encoding method.

prior art

[2] Recently, the need for high-resolution and high-quality images/videos, such as ultra-high-definition (UHD) 4K or 8K or higher images/videos, has increased in various fields. As the resolution or quality of an image/video becomes higher, a relatively larger amount of information or bits is transmitted compared to normal image/video data. Therefore, if image/video data is transmitted using media such as an existing wired/wireless broadband line or stored in a legacy storage media, transmission and storage costs increase.

[3] Moreover, there is currently increasing interest and demand for virtual reality (VR) and artificial reality (AR) content and immersive media such as hologram, as well as increasing broadcast of images/videos having image/video characteristics other than characteristics of real images/videos, such as game images/videos.

[4] Therefore, there is a need for a highly efficient image/video compression method for efficiently compressing and transmitting, storing and reproducing high quality images/videos having various characteristics as described above.

[5] Moreover, there is also discussion of the palette mode encoding method to improve encoding efficiency for screen content, such as computer-generated video, which contains a significant amount of text and graphics. To use this method effectively, a way is needed to encode and signal the associated information.

Brief description of the invention

[6] An object of the present disclosure is to provide a method and apparatus for improving video/image encoding efficiency.

[7] Another object of the present disclosure is to provide a method and apparatus for improving the efficiency of palette mode encoding.

[8] Another object of the present disclosure is to provide a method and apparatus for efficiently configuring and signaling various types of information used in palette mode encoding.

[9] Another object of the present disclosure is to provide a method and apparatus for efficiently applying transition coding in palette mode.

[10] According to an embodiment of the present disclosure, the quantization parameter used in the scaling process for the quantized transition value in the palette mode can be derived based on the minimum quantization parameter information for the transform skip mode. The quantization parameter may have a value equal to or greater than the minimum quantization parameter value for the skip transform mode.

[11] According to an embodiment of the present disclosure, the range of quantized transition values in palette mode may be limited based on bit depth. For example, the range of quantized transition value information for the luma component has values between 0 and (1<<BitDepth _Y )-1, and the range of quantized transition value information for the chrominance component may have values from 0 to (1<<BitDepth _C )-1.

[12] According to an embodiment of the present disclosure, palette size information regarding the maximum palette table index may be determined and signaled by a sequence parameter set (SPS).

[13] According to an embodiment of the present disclosure, a video/image decoding method performed by a decoding apparatus is provided. A video/image decoding method may include a method disclosed in embodiments of the present disclosure.

[14] According to an embodiment of the present disclosure, a decoding apparatus for performing video/image decoding is provided. The decoding device may perform the method disclosed in embodiments of the present disclosure.

[15] According to an embodiment of the present disclosure, a video/image encoding method performed by an encoding apparatus is provided. A video/image encoding method may include a method disclosed in embodiments of the present disclosure.

[16] According to an embodiment of the present disclosure, an encoding apparatus for performing video/image encoding is provided. The encoding device may perform the method disclosed in embodiments of the present disclosure.

[17] According to an embodiment of the present disclosure, a computer-readable digital storage medium is provided in which encoded video/image information generated in accordance with a video/image encoding method disclosed in at least one embodiment of the present disclosure is provided.

[18] According to an embodiment of the present disclosure, a computer-readable digital storage medium is provided that stores encoded information or encoded video/image information causing a decoding device to perform a video/image decoding method disclosed in at least one embodiment of the present disclosures.

Positive results

[19] The present disclosure has various beneficial effects. For example, according to an embodiment of the present disclosure, the overall image/video compression efficiency can be improved. Additionally, according to an embodiment of the present disclosure, efficiency in palette mode encoding can be improved. Additionally, in accordance with an embodiment of the present disclosure, various types of information used in palette mode encoding can be efficiently configured and signaled. Additionally, in accordance with an embodiment of the present disclosure, it is possible to improve the accuracy and efficiency of encoding for transition samples by efficiently applying transition encoding in palette mode.

[20] The results that can be obtained using specific embodiments of the present disclosure are not limited to the results listed above. For example, there may be various technical findings that one skilled in the art may understand or infer from the present disclosure. Accordingly, the specific results of the present disclosure are not limited to the results expressly described in the present disclosure, and may include various results that can be understood or inferred from the technical features of the present disclosure.

Brief description of drawings

[21] FIG. 1 schematically shows an example of a video/image coding system applicable to embodiments of the present disclosure.

[22] FIG. 2 is a diagram schematically illustrating the configuration of a video/image encoding apparatus to which embodiments of the present disclosure are applicable.

[23] FIG. 3 is a diagram schematically illustrating the configuration of a video/image decoding apparatus to which embodiments of the present disclosure are applicable.

[24] FIG. 4 shows an example of a schematic video/image encoding procedure to which embodiments of the present disclosure are applicable.

[25] FIG. 5 shows an example of a schematic video/image decoding procedure to which embodiments of the present disclosure are applicable.

[26] FIG. 6 shows an example to describe the basic structure of palette encoding.

[27] FIG. 7 shows an example for describing the horizontal and vertical cross-scan methods used to encode a palette index map.

[28] FIG. 8 is a diagram for describing an example of a palette mode-based encoding method.

[29] FIG. 9 schematically shows an example of a video/image encoding method in accordance with embodiment(s) of the present disclosure.

[30] FIG. 10 schematically shows an example of a video/image decoding method in accordance with embodiment(s) of the present disclosure.

[31] FIG. 11 shows an example of a content streaming system in which the embodiments set forth in the present disclosure are applicable.

Description of Exemplary Embodiments

[32] The present disclosure may be modified in various ways and may have various embodiments, and specific embodiments will be illustrated in the drawings and described in detail. However, this is not intended to limit the present disclosure to specific embodiments. The terms typically used in this specification are used to describe a particular embodiment, and are not used to limit the technical substance of the present disclosure. Expressions in the singular include expressions in the plural unless the context clearly states otherwise. A term such as “include” or “have” in this specification shall be understood to indicate the existence of a feature, number, step, operation, element, part, or combination thereof described in the specification, and not to preclude the existence or possibility of adding one or several other characteristics, numbers, steps, operations, elements, parts, or combinations thereof.

[33] Meanwhile, elements in the drawings described in the present disclosure are illustrated independently for convenience of description related to different characteristic functions. This does not mean that each of the elements is implemented as separate hardware or separate software. For example, at least two of the elements may be combined to form one element, or one element may be divided into multiple elements. An embodiment in which elements are combined and/or separated is also included within the scope of this disclosure as long as it does not depart from the spirit of this disclosure.

[34] In the present disclosure, the term “A or B” may mean “A only,” “B only,” or “both A and B.” In other words, in the present disclosure, the term “A or B” may be interpreted to indicate “A and/or B”. For example, in the present disclosure, the term “A, B, or C” may mean “A only,” “B only,” “C only,” or “any combination of A, B, and C.”

[35] The “/” symbol or comma used in this disclosure may mean “and/or.” For example, “A/B” could mean “A and/or B.” Accordingly, “A/B” can mean “A only,” “B only,” or “both A and B.” For example, “A, B, C” could mean “A, B or C”.

[36] In the present disclosure, “at least one of A and B” may mean “A only,” “B only,” or “both A and B.” Additionally, in the present disclosure, the expression “at least one of A or B” or “at least one of A and/or B” may be interpreted in the same way as “at least one of A and B”.

[37] Additionally, in the present disclosure, “at least one of A, B, and C” may mean “A only,” “B only,” “C only,” or “any combination of A, B, and C.” Additionally, “at least one of A, B, or C” or “at least one of A, B, and/or C” may mean “at least one of A, B, and C.”

[38] Additionally, parentheses used in this disclosure may mean “for example.” Specifically, in the case where “prediction (intra-prediction)” is expressed, it may be stated that “intra-prediction” is proposed as an example of “prediction”. In other words, the term “prediction” in the present disclosure is not limited to “intra-prediction”, and it may be stated that “intra-prediction” is proposed as an example of “prediction”. Additionally, even in the case where “prediction (ie, intra-prediction)” is expressed, it may be stated that “intra-prediction” is proposed as an example of “prediction”.

[39] The present disclosure relates to video/image coding. For example, the methods/embodiments disclosed in the present disclosure may be applied to a method disclosed in multi-purpose video coding (VVC). Additionally, the methods/embodiments disclosed in the present disclosure may be applied to a method disclosed in the Essential Video Coding (EVC) standard, the AOMedia Video 1 (AV1) standard, the Audio Video Coding Standard 2nd generation (AVS2), or the encoding standard Next generation video/images (eg H.267 or H.268, etc.).

[40] The present disclosure presents various embodiments of video/image encoding, and the embodiments may be performed in combination with each other unless otherwise noted.

[41] In the present disclosure, video may mean a collection of a sequence of images according to the passage of time. A picture usually means a unit representing one image in a particular time period, and a cutout/tile is a unit that constitutes part of a picture in the encoding. The clipping/tile may include one or more coding tree units (CTUs). One picture may consist of one or more cutouts/mosaic elements. A tile is a rectangular CTU area in a specific tile column and a specific tile row in a picture. A tile column is a rectangular area of CTUs having a height equal to the height of the picture and a width specified by the syntax elements in the picture parameter set. A tile row is a rectangular area of CTUs having a height specified by the syntax elements in the picture parameter set and a width equal to the width of the picture. A tile scan is a particular sequential ordering of CTUs tiles in a picture, in which the CTUs are ordered sequentially in a raster scan of the CTUs in a tile, while the tiles in a picture are ordered sequentially in a raster scan of the tiles in the picture. A slice includes an integer number of full tiles or an integer number of consecutive full CTU lines in a picture tile that can exclusively be contained in a single NAL unit.

[42] Meanwhile, one picture can be divided into two or more sub-pictures. A sub-picture may be a rectangular area of one or more cutouts in a picture.

[43] Pixel or pel can mean the smallest unit that makes up one picture (or image). Also, 'sample' can be used as a term corresponding to a pixel. The sample may typically represent a pixel or a pixel value, and may represent only a luma component pixel/pixel value or only a chrominance component pixel/pixel value. Alternatively, sample may mean a pixel value in the spatial domain, or may mean a conversion factor in the frequency domain when the pixel value is converted to the frequency domain.

[44] The unit may represent a basic image processing unit. The unit may include at least one of a specific picture area and information related to the area. One unit may include one luma block and two chrominance blocks (eg, cb, cr). Unit may be used interchangeably with terms such as block or area in some cases. In general, an M×N block may include samples (or arrays of samples) or a set (or array) of transform coefficients of M columns and N rows.

[45] Also, in the present disclosure, at least one of quantization/dequantization and/or transform/inverse transform may be omitted. When quantization/dequantization is omitted, the quantized transformation coefficient may be referred to as the transformation coefficient. When the transform/inverse transform is omitted, the transform coefficients may be called coefficients or residual coefficients, or may still be called transform coefficients for the sake of uniformity of expression.

[46] In the present disclosure, the quantized transform coefficient and the transform coefficient may be referred to as the transform coefficient and the scaled transform coefficient, respectively. In this case, the residual information may include information about the transform coefficient(s), and the information about the transform coefficient(s) may be signaled through a residual encoding syntax. Transform coefficients may be derived based on the residual information (or information about the transform coefficient(s)), and scaled transform coefficients may be derived via inverse transform (scaling) on the transform coefficients. Residual samples can be inferred based on the inverse transform (transform) of the scaled transform coefficients. This may be applied/expressed in other parts of this disclosure as well.

[47] In the present disclosure, technical features explained separately in one drawing may be implemented separately or may be implemented simultaneously.

[48] Next, preferred embodiments of the present disclosure are described more specifically with reference to the accompanying drawings. Further, in the drawings, the same reference numeral is used for the same element, and redundant description of the same element may be omitted.

[49] FIG. 1 illustrates an example of a video/image coding system to which embodiments of the present document may be applied.

[50] With reference to FIG. 1, a video/image encoding system may include a source device and a destination device. A source device may transmit encoded information or video/image data to a destination device via a digital storage medium or network in the form of a file or streaming.

[51] The source device may include a video source, an encoder, and a transmitter. The receiving device may include a receiver, a decoding device, and a renderer. The encoding device may be called a video/image encoding device, and the decoding device may be called a video/image decoding device. The transmitter may be included in the encoding device. The receiver may be included in a decoding device. The rendering module may include a display, and the display may be configured as a separate device or an external component.

[52] The video source may obtain video/image through a video/image capture, synthesis, or generation process. The video source may include a video/image capturing device and/or a video/image generation device. The video/image capturing device may include, for example, one or more cameras, video/image archives including previously captured video/images, and the like. The video/image generating apparatus may include, for example, computers, tablets, and smartphones and may (electronically) generate video/images. For example, the virtual video/image may be generated by a computer or the like. In this case, the video/image capture process can be replaced by the associated data generation process.

[53] The encoder can encode input video/images. The encoding device may perform a sequence of procedures such as prediction, transformation and quantization for compact and efficient encoding. The encoded data (encoded video/image information) may be output in the form of a bit stream.

[54] A transmitter may transmit encoded information or video/image data output in the form of a bitstream to a receiver of a recipient device via a digital storage medium or network in the form of a file or streaming. The digital storage medium may include various storage media such as USB, SD, CD, DVD, Blu-ray, HDD, SSD and the like. The transmitter may include an element for generating a media file in a predefined file format and may include an element for transmission over a broadcast/communications network. The receiver can receive/extract the bit stream and transmit the received bit stream to the decoding device.

[55] The decoding apparatus can decode video/images by performing a sequence of procedures such as dequantization, deconversion, and prediction corresponding to the operation of the encoding apparatus.

[56] The renderer can render the decoded video/image. The rendered video/image can be displayed via the display.

[57] FIG. 2 is a diagram schematically illustrating the configuration of a video/image encoding apparatus to which embodiments of the present disclosure may be applied. Further, the encoding device may include an image encoding device and/or a video encoding device.

[58] With reference to FIG. 2, encoding apparatus 200 may include or be configured with an image partitioning module 210, a predictor 220, a residual processor 230, an entropy encoder 240, an adder 250, a filter 260, and a memory 270. The predictor 220 may include an inter-predictor 221 and an intra-predictor 221. predictor 222. Residual processor 230 may include transformer 232, quantizer 233, dequantizer 234, and inverse transformer 235. Residual processor 230 may further include subtractor 231. Adder 250 may be referred to as a reconstructor or reconstructed block generator. The image partitioning module 210, predictor 220, residual processor 230, entropy encoder 240, adder 250, and filter 260, which are described above, may be configured by one or more hardware components (eg, chipsets or encoder processors) in accordance with an embodiment. Additionally, memory 270 may include a decoded picture buffer (DPB) or may be configured with a digital storage medium. The hardware component may further include memory 270 as an internal/external component.

[59] The image splitter 210 may split an input image (or picture, frame) input to the encoder 200 into one or more processing units. For example, a processing unit may be called a coding unit (CU). In this case, the coding unit may be recursively partitioned according to a quadtree-binary-tree-ternary (QTBTTT) structure from a coding tree unit (CTU) or a largest coding unit (LCU). For example, one encoding unit may be decomposed into multiple encoding units of greater depth based on a quadtree structure, a binary structure, and/or a ternary tree structure. In this case, for example, the quadtree structure is applied first, and the binary tree structure and/or ternary tree structure may be applied later. Alternatively, the binary tree structure may be applied first. The encoding procedure in accordance with the present disclosure may be performed based on a final encoding unit that is no longer split. In this case, based on the coding efficiency according to the characteristics of the image or the like, the maximum coding unit can be directly used as the final coding unit, or, if necessary, the coding unit can be recursively divided into coding units of a deeper depth, so that the coding unit having an optimal size, can be used as the final coding unit. Here, the encoding procedure may include a prediction, transformation and reconstruction procedure, which will be described later. As another example, the processing unit may further include a prediction unit (PU) or a transformation unit (TU). In this case, each of the prediction unit and the transformation unit may be separated or split from the above-mentioned final encoding unit. The prediction unit may be a sample prediction unit, and the transform unit may be a unit for deriving a transform coefficient and/or a unit for deriving a residual signal from the transform coefficient.

[60] Unit may be used interchangeably with terms such as block or area in some cases. In general, an M×N block can represent samples consisting of M columns and N rows, or a group of transform coefficients. The sample may generally represent a pixel or pixel value, may represent only a luma component pixel/pixel value, or may represent only a chrominance component pixel/pixel value. A sample can be used as a term corresponding to a pixel or pel configuring a single picture (or image).

[61] The encoding device 200 can generate a residual signal (residual block, residual sample array) by subtracting a prediction signal (predicted block, prediction sample array) output from the inter-predictor 221 or intra-predictor 222 from the input image signal (original block , the original sample array), and the generated residual signal is transmitted to the converter 232. In this case, as shown, a module for subtracting the predicted signal (predicted block, prediction sample array) from the input image signal (original block, original sample array) in the encoder 200 may be referred to as a subtractor 231. The predictor may perform prediction on a block to be processed (hereinafter referred to as a current block) and generate a predicted block including prediction samples of the current block. The predictor can determine whether intra-prediction or inter-prediction is applied in units of the current block or CU. As described later in the description of each prediction mode, the predictor may generate various prediction-related information, such as prediction mode information, to transmit the generated information to the entropy encoder 240. The prediction information may be encoded by the entropy encoder 240 and output in the form of a bit stream.

[62] Intra predictor 222 may predict the current block based on samples in the current picture. The reference samples may be located adjacent to the current block or may be spaced apart from the current block in accordance with the prediction mode. In intra-prediction, prediction modes may include a plurality of undirected modes and a plurality of directed modes. The omnidirectional mode may include, for example, a DC mode or a planar mode. The directional mode may include, for example, 33 directional prediction modes or 65 directional prediction modes according to the granularity of the prediction direction. However, this is only an example, and more or less directional prediction modes than listed above may be used according to settings. Intra predictor 222 may determine the prediction mode applied to the current block using the prediction mode applied to the adjacent block.

[63] The inter-predictor 221 may output a predicted block of the current block based on a reference block (reference sample array) specified by a motion vector in the reference picture. Here, in order to reduce the amount of motion information transmitted in the inter-prediction mode, motion information may be predicted in block, sub-block, or sample units based on the correlation of motion information between a neighboring block and the current block. The motion information may include a motion vector and a reference picture index. The motion information may further include inter-prediction direction information (L0 prediction, L1 prediction, Bi prediction, etc.). In the case of inter-prediction, the neighbor block may include a spatial neighbor block existing in the current picture and a temporal neighbor block existing in the reference picture. The reference picture including the reference block and the reference picture including the temporary adjacent block may be the same or different. A temporary neighbor block may be called a co-located reference block, a co-located CU (colCU), etc., and a reference picture including a temporary neighboring block may be called a co-located picture (colPic). For example, inter-predictor 221 may configure a list of motion information candidates based on neighboring blocks and generate information indicating which candidate is used to output the motion vector and/or reference picture index of the current block. Inter-prediction can be performed based on various prediction modes. For example, in the case of the skip mode and the merge mode, the inter-predictor 221 may use the motion information of a neighboring block as the motion information of the current block. In the case of the skip mode, unlike the combine mode, the residual signal may not be transmitted. A motion vector prediction (MVP) mode may indicate the motion vector of a current block using the motion vector of an adjacent block as a motion vector predictor and signaling the motion vector difference.

[64] Predictor 220 may generate a predicted signal based on various prediction methods described below. For example, a predictor may not only apply intra-prediction or inter-prediction to predict one block, but may also apply intra-prediction and inter-prediction simultaneously. This may be called combined inter- and intra-prediction (CIIP). In addition, the predictor can be based on intra-block copy (IBC) prediction mode or palette mode to perform prediction on a block. The IBC prediction mode or the palette mode can be used for encoding image/video content of a game or the like, such as screen content coding (SCC). IBC basically performs prediction on the current picture, but it can perform similar to inter-prediction in that it outputs a reference block on the current picture. That is, the IBC may use at least one of the inter-prediction methods described herein. Palette mode can be considered an example of intra-encoding or intra-prediction. When the palette mode is applied, the sample value in the picture can be signaled based on the palette index and palette table information.

[65] A prediction signal generated by a predictor (including inter-predictor 221 and/or intra-predictor 222) may be used to generate a reconstructed signal or to generate a residual signal. Converter 232 may generate transform coefficients by applying a transform method to the residual signal. For example, the transform method may include at least one of a discrete cosine transform (DCT), a discrete sine transform (DST), a Karhunen-Loeve transform (KLT), a graph-based transform (GBT), or a conditional nonlinear transform (CNT). . Here, GBT means the transformation obtained from a graph when the relation information between pixels is represented by the graph. CNT means a transform that is derived from the predicted signal generated using all the previously reconstructed pixels. In addition, the transformation process can also be applied to square blocks of pixels that are the same size, or can be applied to blocks that are variable in size rather than square.

[66] Quantizer 233 may quantize transform coefficients to provide the quantized transform coefficients to entropy encoder 240, and entropy encoder 240 may encode the quantized signal (quantized transform coefficient information) into an encoded quantized signal into a bit stream. Information about the quantized transform coefficients may be called residual information. Quantizer 233 may reorder the quantized transform coefficients having a block form into a one-dimensional vector form based on the scanning order of the coefficients, and generate information about the quantized transform coefficients based on the quantized transform coefficients in the one-dimensional vector form. Entropy encoder 240 can perform various encoding techniques, such as, for example, exponential Golomb coding, context adaptive variable length coding (CAVLC), context adaptive binary arithmetic coding (CABAC). Entropy encoder 240 may also encode information (eg, syntax element values, etc.) needed to reconstruct the video/image other than the quantized transform coefficients, together or separately. Encoded information (eg, encoded video/image information) may be transmitted or stored in Network Abstraction Layer (NAL) units in the form of a bitstream. The video/image information may further include information about 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). In addition, the video/image information may further include general restriction information. The signaled/transmitted information and/or syntax elements described later herein may be encoded through the encoding procedure described above and included in the bitstream. The bitstream may be transmitted over a network or may be stored in a digital storage medium. The network may include a broadcast network and/or a communications network, and the digital storage medium may include various storage media such as USB, SD, CD, DVD, Blu-ray, HDD, and SSD. A transmitter (not shown) for transmitting the signal output from the entropy encoder 240 and/or a storage module (not shown) for storing the signal may be configured as internal/external elements of the encoding device 200, or the transmitter may be included in the entropy encoder 240.

[67] The quantized transform coefficients output from quantizer 233 can be used to generate a predicted signal. For example, dequantizer 234 and deconverter 235 apply dequantization and deconversion to the quantized transform coefficients so that the residual signal (residual block or residual samples) can be reconstructed. Adder 250 may add the reconstructed residual signal to the predicted signal output from inter-predictor 221 or intra-predictor 222 so that a reconstructed signal (reconstructed picture, reconstructed block, reconstructed sample array) can be generated. As in the case where the skip mode is applied, if there is no remainder for a block to be processed, the predicted block can be used as a reconstructed block. The adder 250 may be referred to as a recovery module or a recovery block generator. The generated reconstructed signal can be used to intra-predict the next block to be processed in the current picture, and, as described below, can also be used to inter-predict the next picture through filtering.

[68] Meanwhile, luma mapping with chroma scaling (LMCS) can be applied during the encoding and/or reconstruction process of a picture.

[69] Filter 260 may apply filtering to the reconstructed signal, thereby improving the subjective/objective quality of the image. For example, filter 260 may apply various filtering methods to the restored picture to generate a modified restored picture, and store the modified restored picture in memory 270, specifically in DPB memory 270. Various filtering methods may include, for example, deblocking filtering, adaptive sampling bias, adaptive loop filter, bidirectional filter and the like. The filter 260 may generate various filtering-related information to provide the generated information to the entropy encoder 240, as described later in the description of each filtering method. Information related to filtering may be encoded by entropy encoder 240 for output in the form of a bit stream.

[70] The modified reconstructed picture transferred to the memory 270 can be used as a reference picture in the inter-predictor 221. When inter-prediction is applied by the inter-predictor, the encoding device can avoid prediction mismatch between the encoding device 200 and the decoding device 300, and also improve coding efficiency.

[71] DPB memory 270 may store a modified reconstructed picture for use as a reference picture in inter-predictor 221. Memory 270 may store block motion information from which motion information in the current picture and/or block motion information is derived (or encoded) in the previously restored picture. The stored motion information may be transmitted to the inter-predictor 221 to be used as spatial neighbor motion information or temporal neighbor motion information. Memory 270 may store reconstructed samples of reconstructed blocks in the current picture and may transfer the reconstructed samples to intra-predictor 222.

[72] FIG. 3 is a diagram schematically illustrating the configuration of a video/image decoding apparatus to which embodiments of the present disclosure are applied. Further, the decoding apparatus may include an image decoding apparatus and/or a video decoding apparatus.

[73] With reference to FIG. 3, decoding apparatus 300 may include and be configured with an entropy decoder 310, a remainder processor 320, a predictor 330, an adder 340, a filter 350, and a memory 360. The predictor 330 may include an inter-predictor 331 and an intra-predictor 332. Processor 320 the remainder may include a dequantizer 321 and an inverse converter 321. The entropy decoder 310, the residual processor 320, the predictor 330, the adder 340, and the filter 350 that were described above may be configured by one or more hardware components (e.g., decoder chipsets or processors). ) according to an embodiment. In addition, memory 360 may include a decoded picture buffer (DPB) or may be configured with a digital storage medium. The hardware component may further include memory 360 as an internal/external component.

[74] When a bitstream including video/image information is input, the decoding apparatus 300 can reconstruct an image in response to a process in which the video/image information is processed in the encoding apparatus shown in FIG. 2. For example, the decoding apparatus 300 may output units/blocks based on the block division related information obtained from the bit stream. The decoding apparatus 300 may perform decoding using a processing unit applied in the encoding apparatus. Therefore, the processing unit may be, for example, a coding unit, and the coding unit may be partitioned according to a quadtree structure, a binary tree structure, and/or a ternary tree structure from a coding tree unit or a maximum coding unit. One or more transformation units may be derived from a coding unit. Additionally, the reconstructed image signal decoded and output by the decoding device 300 can be reproduced by the playback device.

[75] The decoding device 300 may receive a signal output from the encoding device according to FIG. 2 in the form of a bitstream, and the received signal can be decoded by the entropy decoder 310. For example, the entropy decoder 310 can output information (eg, video/image information) necessary for image reconstruction (or picture reconstruction) by performing parsing of the bitstream. The video/image information may further include information about 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). In addition, the video/image information may further include general restriction information. The decoding apparatus may further decode the picture based on the parameter set information and/or general constraint information. The signaled/received information and/or syntax elements described later herein may be decoded through a decoding procedure and obtained from the bitstream. For example, an entropy decoder may decode information in a bitstream based on an encoding method such as exponential Golomb coding, CAVLC, or CABAC, and output the value of the syntax element needed to reconstruct the image and the quantized values of the transform coefficients for the remainder. More specifically, the CABAC entropy decoding method may receive a bin corresponding to each syntax element from a bitstream, determine a context model using the information of the syntax element to be decoded and the decoding information of the adjacent block and the block to be decoded, or the information of the symbol/bin decoded in the previous stage, and generate a symbol corresponding to the meaning of each syntactic element by predicting the probability of generating a bin according to the determined context model to perform arithmetic decoding of the bin. In this case, the CABAC entropy decoding method may determine the context model and then update the context model using the information of the decoded symbol/bin for the context model of the next symbol/bin. Prediction information, among the information decoded by the entropy decoder 310, may be provided to the predictor (inter-predictor 332 and intra-predictor 331), and the residual value with which entropy decoding was performed by the entropy decoder 310, that is, quantized transform coefficients and related parameter information may be input to residual processor 320. Residual processor 320 may output a residual signal (residual block, residual samples, residual sample array). Additionally, filtering information among the information decoded by the entropy decoder 310 may be provided to the filter 350. Meanwhile, a receiver (not illustrated) for receiving a signal output from the encoding device may be further configured as an internal/external element of the decoding device 300, or the receiver may also be a component of the entropy decoder 310. Meanwhile, the decoding device according to this document may be called a video/image/picture decoding device, and the decoding device may also be classified into an information decoder (video/image/picture information decoder) and a sample decoder (video/image/picture sampling decoder). The information decoder may include an entropy decoder 310, and the sample decoder may include at least one of a dequantizer 321, an inverse converter 322, an adder 340, a filter 350, a memory 360, an inter-predictor 332, and an intra-predictor 331.

[76] Dequantizer 321 may dequantize the quantized transform coefficients to output transform coefficients. The dequantizer 321 may reorder the quantized transform coefficients in the form of a two-dimensional block. In this case, reordering may be performed based on the scanning order of the coefficients performed by the encoder. The dequantizer 321 may perform dequantization on the quantized transform coefficients using a quantization parameter (eg, quantization step size information) and obtain the transform coefficients.

[77] An inverter 322 inverts the transform coefficients to obtain a residual signal (residual block, residual sample array).

[78] Predictor 330 may perform prediction on the current block and generate a predicted block including prediction samples of the current block. The predictor can determine whether intra-prediction or inter-prediction is applied to the current block based on the prediction information output from the entropy decoder 310, and can determine a particular intra/inter-prediction mode.

[79] Predictor 320 may generate a predicted signal based on various prediction methods described below. For example, a predictor may not only apply intra-prediction or inter-prediction to predict one block, but also simultaneously apply intra-prediction and inter-prediction. This may be called combined inter- and intra-prediction (CIIP). In addition, the predictor may be based on intra-block copy (IBC) prediction mode or palette mode for block prediction. The IBC prediction mode or the palette mode can be used for encoding image/video game content or the like, such as screen content encoding (SCC). IBC basically performs prediction in the current picture, but can be performed similarly to inter-prediction in that it outputs a reference block in the current picture. That is, the IBC may use at least one of the inter-prediction methods described herein. Palette mode can be considered an example of intra-encoding or intra-prediction. When the palette mode is applied, information about the palette table and palette index may be included in the video/image information and signaled.

[80] Intra predictor 331 may predict the current block based on samples in the current picture. The reference samples may be located adjacent to the current block or may be spaced apart from the current block in accordance with the prediction mode. In intra-prediction, prediction modes may include a plurality of undirected modes and a plurality of directed modes. Intra predictor 331 may determine the prediction mode applied to the current block using the prediction mode applied to the adjacent block.

[81] Inter-predictor 332 may output a predicted block for the current block based on a reference block (reference sample array) specified by a motion vector in the reference picture. In this case, in order to reduce the amount of motion information transmitted in the inter-prediction mode, motion information may be predicted in block, sub-block, or sample units based on the correlation of motion information between a neighboring block and the current block. The motion information may include a motion vector and a reference picture index. The motion information may further include inter-prediction direction information (L0 prediction, L1 prediction, Bi prediction, etc.). In the case of inter-prediction, the neighbor block may include a spatial neighbor block existing in the current picture and a temporal neighbor block existing in the reference picture. For example, inter-predictor 332 may configure a motion information candidate list based on neighboring blocks and output a motion vector of the current block and/or a reference picture index based on the received candidate selection information. Inter-prediction may be performed based on various prediction modes, and the prediction information may include information indicating an inter-prediction mode for the current block.

[82] Adder 340 may add the received residual signal with a predicted signal (predicted block, prediction sample array) output from a predictor (including inter-predictor 332 and/or intra-predictor 331) to generate a reconstructed signal (reconstructed picture, reconstructed block , reconstructed array of samples). In the case where the skip mode is applied, if there is no remainder for a block to be processed, then the predicted block can be used as a reconstructed block.

[83] The adder 340 may be referred to as a recovery module or a recovery block generator. The generated reconstructed signal can be used for intra-prediction of the next block to be processed in the current picture, and, as described below, can be output by filtering or can be used for inter-prediction of the next picture.

[84] Meanwhile, luminance chroma scaling (LMCS) mapping can also be applied in the picture decoding process.

[85] Filter 350 may apply filtering to the reconstructed signal, thereby improving the subjective/objective quality of the image. For example, filter 350 may apply various filtering methods to the reconstructed picture to generate a modified reconstructed picture, and transfer the modified reconstructed picture to memory 360, specifically the DPB of memory 360. Various filtering methods may include, for example, deblocking filtering, adaptive sample bias, adaptive loop filter, bidirectional filter and the like.

[86] The (modified) reconstructed picture stored in the DPB memory 360 may be used as a reference picture in the inter-predictor 332. The memory 360 may store motion information of a block in which motion information in the current picture is output (or decoded), and/or information about the movement of blocks in a previously reconstructed picture. The stored motion information may be transmitted to the inter-predictor 260 for use as spatial neighbor motion information or temporal neighbor motion information. Memory 360 may store reconstructed samples of reconstructed blocks in the current picture and transfer the stored reconstructed samples to intra-predictor 331.

[87] In the present disclosure, the embodiments described in the filter 260, inter-predictor 221 and intra-predictor 222 of the encoding device 200 can be applied in the same way to the filter 350, inter-predictor 332 and intra-predictor 331 of the decoding device 300.

[88] As described above, when performing video encoding, prediction is performed to improve compression efficiency. By this, a predicted block including prediction samples for the current block can be generated as a block to be encoded. Here, the predicted block includes prediction samples in a spatial domain (or pixel domain). The predicted block is output equally in the encoding device and the decoding device, and the encoding device can signal information (residual information) about the remainder between the original block and the predicted block, rather than the original sample value of the original block, to the decoding device, thereby improving the efficiency of image encoding. The decoding apparatus may output a residual block including residual samples based on the residual information, add the residual block and the predicted block to generate reconstructed blocks including the reconstructed samples, and generate a reconstructed picture including the reconstructed blocks.

[89] Residual information can be generated in the transformation and quantization procedure. For example, the encoding device may output a residual block between an original block and a predicted block, perform a transform procedure on the residual samples (residual array of samples) included in the residual block to output transform coefficients, perform a quantization procedure on the transform coefficients to output quantized transform coefficients, and signal the corresponding residual information to the decoding device (via a bit stream). Here, the residual information may include quantized transform coefficient value information, location information, transform method, transform kernel, quantization parameter, and the like. The decoding apparatus may perform a dequantization/deconversion procedure based on the residual information and output residual samples (or residual blocks). The decoding apparatus can generate a reconstructed picture based on the predicted block and the residual block. Also, to assist in inter-prediction of the next picture, the encoder may also dequantize/de-convert the quantized transform coefficients to output a residual block and generate a reconstructed picture from it.

[90] FIG. 4 shows an example of a schematic video/image encoding procedure to which embodiments of the present disclosure are applicable. In fig. 4, S400 may be performed by the encoder predictor 220 described above in FIG. 2, S410 may be performed by the remainder processor 230, and S420 may be performed by the entropy encoder 240. S400 may include an inter/intra-prediction procedure described in the present disclosure, S410 may include a remainder processing procedure described in the present disclosure, and S420 may include the information encoding procedure described in this disclosure.

[91] With reference to FIG. 4, the video/image encoding procedure may include not only a procedure for encoding picture reconstruction information (eg, prediction information, residual information, splitting information, etc.) and outputting the encoded information in the form of a bit stream, as presented in the description of FIG. . 2, but also a procedure for generating a reconstructed picture for the current picture and a procedure (optional) for applying in-circuit filtering to the restored picture. The encoder may output (modified) residual samples from the transform coefficients quantized by the dequantizer 234 and the inverse converter 235, and generate a reconstructed picture based on the prediction samples output in S400 and the (modified) residual samples. Thus, the generated reconstructed picture may be the same as the reconstructed picture generated by the above-described decoding device. The modified reconstructed picture may be generated by an in-loop filtering procedure on the reconstructed picture, which may be stored in the decoded picture buffer or memory 270, and, as with the decoding apparatus, may be used as a reference picture in the inter-prediction procedure during subsequent encoding of the picture. As described above, part or all of the in-loop filtration procedure may be omitted in some cases. When the in-loop filtering procedure is performed, the (in-loop) filtering-related information (parameters) can be encoded by the entropy encoder 240 and output in the form of a bit stream, and the decoding device can perform the in-loop filtering procedure similar to that of the encoder based on the filtering-related information.

[92] Through this in-loop filtering procedure, noise generated during image/video encoding such as blocking artifacts and ringing artifacts can be reduced, and subjective/objective visual quality can be improved. In addition, by performing the in-loop filtering procedure in both the encoding device and the decoding device, the encoding device and the decoding device can output the same prediction result, improve the reliability of picture encoding, and reduce the amount of data to be transmitted for picture encoding.

[93] As described above, the picture restoration procedure can be performed not only in the decoding device, but also in the encoding device. A reconstructed block may be generated based on intra-prediction/inter-prediction for each block, and a reconstructed picture including the reconstructed blocks may be generated. When the current picture/clipping/tile group is an I-picture/clipping/tile group, the blocks included in the current picture/clipping/tile group can be reconstructed based on intra-prediction only. On the other hand, when the current picture/clipping/tile group is a P- or B-picture/clipping/tile group, the blocks included in the current picture/clipping/tile group can be reconstructed based on intra-prediction or inter-prediction -predictions. In this case, inter-prediction can be applied to some blocks in the current picture/clipping/tile group, and intra-prediction can be applied to some remaining blocks. The color component of a picture may include a luma component and a chrominance component, and, unless expressly limited in the present disclosure, the methods and embodiments proposed in the present disclosure may be applied to the luma component and the chrominance component.

[94] FIG. 5 shows an example of a schematic video/image decoding procedure to which embodiments of the present disclosure are applicable. In fig. 5, S500 may be performed by the entropy decoder 310 of the decoding apparatus described above in FIG. 3, S510 may be performed by predictor 330, S520 may be performed by residual processor 320, S530 may be performed by adder 340, and S540 may be performed by filter 350. S500 may include an information decoding procedure described in the present disclosure, S510 may include an inter/ intra-prediction described in the present disclosure, S520 may include a residual processing procedure described in this disclosure, S530 may include a block/picture recovery procedure described in this disclosure, and S540 may include an intra-loop filtering procedure described in the present disclosure. in this disclosure.

[95] With reference to FIG. 5, the picture decoding procedure may include a procedure (S500) for obtaining image/video information from the bit stream (by decoding), a picture restoration procedure (S510 to S530), and an in-loop filtering procedure (S540) for the restored picture, as presented in the description of FIG. . 3. The picture reconstruction procedure may be performed based on the prediction samples and residual samples obtained by inter/intra prediction (S510) and residual processing (S520; dequantization and inverse transform for quantized transform coefficients) described in the present disclosure. The modified reconstructed picture may be generated by an in-loop filtering procedure for the reconstructed picture generated by the picture restoration procedure, and the modified restored picture may be output as a decoded picture. Additionally, the modified reconstructed picture can be stored in the decoded picture buffer or decoding device memory 360 and used as a reference picture in an inter-prediction procedure during decoding of a subsequent picture.

[96] In some cases, the in-loop filtering procedure may be omitted. In this case, the reconstructed picture can be output as a decoded picture, stored in the decoded picture buffer or decoding device memory 360, and used as a reference picture in inter-prediction during decoding of a subsequent picture. The in-loop filtering procedure (S540) may include a deblocking filtering procedure, an adaptive sample offset (SAO) procedure, an adaptive loop filter (ALF) procedure, and/or a bidirectional filter procedure as described above, and some or all of these may be omitted . Additionally, one or some of the deblocking filtering procedure, the sample adaptive offset (SAO) procedure, the adaptive loop filter (ALF) procedure, and the bidirectional filter procedure may be applied sequentially or all may be applied sequentially. For example, after the deblocking filtering procedure is applied to the reconstructed picture, the SAO procedure may be performed. For example, after a deblocking filtering procedure is applied to the reconstructed picture, an ALF procedure may be performed. This can be done in the encoding device in the same way.

[97] As described above, the encoder can output a residual block (residual samples) based on a block (prediction samples) predicted through intra/inter/IBC prediction and the like, and apply transform and quantization to the output residual samples to output quantized conversion factors. Information about the quantized transform coefficients (residual information) may be included in the residual encoding syntax and output in the form of a bit stream after encoding. The decoding apparatus may obtain information (residual information) about the quantized transform coefficients from the bit stream and decode the information to output the quantized transform coefficients. The decoding apparatus may output residual samples by dequantization/deconversion based on the quantized transform coefficients. As described above, at least one of quantization/dequantization and/or transform/inverse transform may be omitted. When the transform/inverse transform is omitted, the transform coefficients may be called coefficients or residual coefficients, or may also be called transform coefficients for consistency of expression. Whether a transform can be omitted/inverted can be signaled based on transform_skip_flag. For example, when the value of transform_skip_flag is 1, it may indicate that the transform/reverse transform is skipped, which may be referred to as transform skip mode.

[98] In general, in video/image encoding, the quantization degree may be changed, and the compression ratio may be adjusted using the changed quantization degree. From an implementation point of view, the quantization parameter (QP) can be used instead of the complexity-aware quantization degree. For example, integer value quantization parameters from 0 to 63 may be used, and each quantization parameter value may correspond to an actual quantization degree. For example, the quantization parameter QP _Y for the luminance component (luminance sample) and the quantization parameter QP _C for the chrominance component (chroma sample) may be set differently.

[99] The quantization process may take the transform coefficient C as input, divide it by the quantization degree Q _step , and from this obtain the quantized transform coefficient C'. In this case, in consideration of computational complexity, the quantization degree may be multiplied by the scale to form a whole, and a shift operation by a value corresponding to the scale value may be performed. The quantization scale can be derived based on the product of the quantization degree and the scale value. That is, the quantization scale can be output in accordance with the QP. For example, the quantized transform coefficient C' may be derived by applying a quantization scale to the transform coefficient C.

[100] The dequantization process is the inverse process of the quantization process and can obtain the reconstructed transform coefficient C" by multiplying the quantized transform coefficient C' by the quantization degree Q _step . In this case, the level scale can be output in accordance with the quantization parameter, and the reconstructed transform coefficient C" can be output by applying the level scale to the quantized transform coefficient C'. The reconstructed conversion coefficient C” may differ slightly from the original conversion coefficient C due to losses in the conversion and/or quantization processes. Accordingly, in the encoding device, dequantization is performed in the same manner as in the decoding device.

[101] Meanwhile, prediction can be performed based on palette coding. Palette coding is a useful method for representing blocks of a small number of unique color values. Instead of applying prediction and transformation to blocks, an index to indicate the color value of each sample is signaled in palette mode. This palette mode is useful for saving video memory buffer space. The block may be encoded using a palette mode (eg MODE_PLT). To decode a block encoded in this way, the decoder needs to decode the color and palette index. A palette color can be represented by a palette table and can be encoded by a palette table encoding tool.

[102] FIG. 6 shows an example for describing the basic structure of palette coding.

[103] With reference to FIG. 6, image 600 may be represented by a histogram 610. Here, dominant color values are typically mapped to color indexes (620), and the image may be encoded using a color index map (630).

[104] Palette encoding may be referred to as (intra) palette mode, (intra) palette encoding mode, or the like. The current block can be reconstructed according to palette encoding or palette mode. Palette coding can be considered as an example of intra-coding or can be considered as one of the methods of intra-prediction. However, similar to the skip mode described above, additional residual values for the corresponding block may not be signaled.

[105] For example, palette mode can be used to improve encoding efficiency for on-screen content, such as computer-generated video, that contains a significant amount of text and graphics. In general, the local area of the screen content has different colors, distinguished by sharp edges. To take advantage of this property, the palette mode can represent block selections based on indices pointing to color entries in the palette table.

[106] For example, palette table information may be signaled. The palette table may include an index value corresponding to each color. Palette index prediction data may be applied, and the palette table may include data indicating index values for at least a portion of a palette index map that maps pixels of the video data to palette table color indices. The palette index prediction data may include run value data that associates index values for at least a portion of the palette index map with the run values. The series value may be associated with a transition color index. The palette index map may be generated from the palette index prediction data, at least in part, by determining whether the index value of the palette index prediction data should be adjusted based on the last index value. The current block in the picture can be reconstructed according to the palette index map.

[107] When palette mode is used, the CU pixel values can be represented by a set of representative color values. Such a set may be referred to as a palette. In the case of a pixel having a value close to a color value in the palette, the palette index corresponding to the color value in the palette may be signaled. In the case of a pixel having a color value other than a palette, the pixel may be represented by a transition symbol, and the quantized value of the pixel may be directly signaled. In the present disclosure, a pixel or pixel value may be referred to as a sample or sample value.

[108] To decode a block encoded in palette mode, the decoder needs to decode the colors and palette indices. Palette colors can be represented in a palette table and encoded using the palette table encoding tool. A jump flag may indicate whether a jump character is present in the current CU by signaling for each CU. If a jump symbol is present, the palette table is incremented by 1 and the last index can be assigned to the jump mode. The palette indices of all pixels in the CU can form a palette index map and can be encoded using the palette index map encoding tool.

[109] For example, a palette predictor may be supported to encode a palette table. The predictor can be initialized at the beginning of each cut, where the predictor is reset to zero. For each palette predictor entry, a reuse flag may be signaled to indicate whether it is part of the current palette. The reuse flag may be transmitted using run length encoding of zero. Next, the number of new palette entries can be signaled using zero-order exponential Golomb coding. Finally, the component value for new palette entries can be signaled. After encoding the current CU, the palette predictor can be updated using the current palette, and the old palette predictor entries that are not reused in the current palette can be appended to the end of the new palette predictor until the allowed maximum size is reached (palette padding).

[110] For example, the index may be encoded using horizontal and vertical cross scans to encode a palette index map. The scan order may be explicitly signaled from the bitstream using flag information (eg, palette_transpose_flag).

[111] FIG. 7 shows an example for describing the horizontal and vertical cross-scan methods used to encode a palette index map.

[112] FIG. 7(a) shows an example of palette index map encoding using horizontal cross-scan, and FIG. 7(b) shows an example of palette index map encoding using vertical cross-scan.

[113] As shown in FIG. 7(a), when horizontal scanning is used, palette indices can be encoded by scanning samples from samples in the first row (top row) to samples in the last row (bottom row) in the current block (ie, current CU) in the horizontal direction.

[114] As shown in FIG. 7(b), when vertical scanning is used, palette indices can be encoded by scanning samples from samples in the first column (leftmost column) to the last column (rightmost column) in the current block (ie, current CU) in the vertical direction.

[115] The palette index can be encoded using two palette selection modes, such as the “INDEX” mode and the “COPY_ABOVE” mode. Such a palette mode may be signaled using a flag indicating whether the mode is “INDEX” or “COPY_ABOVE”. Here, the flag may be signaled except for the top row when horizontal scanning is used, and the flag may be signaled except for the first column A when vertical scanning is used or when the previous mode is the “COPY_ABOVE” mode. In “COPY_ABOVE” mode, the index of the selection palette in the top line can be copied. In “INDEX” mode, the palette index can be explicitly signaled. For both the “INDEX” mode and the “COPY_ABOVE” mode, a run value indicating the number of pixels encoded using the same mode may be signaled.

[116] The encoding order for the index map may be as follows. First, the number of index values for the CU may be signaled. The current index values for the entire CU can then be signaled using truncated binary (TB) encoding. Both the number of indexes and the index values can be encoded in bypass mode. In this case, index-linked traversal bins can be grouped together. Then, the palette mode ("INDEX" mode or "COPY_ABOVE" mode) and series can be signaled interleaved. Finally, component transition values corresponding to transition samples for the entire CU can be grouped together and encoded in bypass mode. After signaling the index values, the optional last_run_type_flag syntax element may be signaled. This syntax element is not required to signal the run value corresponding to the last run in the block along with the number of indices.

[117] Meanwhile, in the VVC standard, a double tree can be initiated for I-cut, which separates the coding unit split for luma and chrominance. Palette encoding (palette mode) can be applied to luminance (Y component) and chrominance (Cb and Cr components) separately or together. When dual tree is disabled, palette encoding (palette mode) can be applied to luma (Y component) and chroma (Cb and Cr component) together.

[118] FIG. 8 is a diagram for describing an example of a palette mode-based encoding method.

[119] With reference to FIG. 8, the decoding apparatus may obtain palette information based on the bitstream and/or previous palette information (S800).

[120] In one embodiment, the decoding apparatus may obtain palette mode information with respect to each sampling position and run length information of each palette mode when passing through the palette index information, passing direction information (scan order), and sampling in the CU from bit stream.

[121] The decoding apparatus may configure the palette based on the palette information (S810).

[122] In an embodiment, the decoding device may configure a palette predictor. The palette information used in the previous block can be stored for the CU of the next palette (ie, the CU encoded in palette mode) to be generated later, and this can be defined as a palette predictor entry. The decoder may receive the new palette entry information and configure the palette for the current CU. For example, after receiving the acquired palette predictor reuse information and the new palette entry information to be used in the current CU, the decoding apparatus may combine these two pieces of entry information to form one palette representing the current CU.

[123] The decoding apparatus may output sample values (sample prediction values) in a palette-based current block (S820).

[124] In an embodiment, the decoding apparatus may configure samples from the received palette information when passing through the samples in the CU in a horizontal direction or a vertical direction based on the passing direction information (scan order). If the palette mode information specifies the COPY_ABOVE mode, each sample value in the CU can be output by copying the left sample position index information in the vertical scan and copying the top sample position index information in the horizontal scan. That is, by deriving the color value of each sample from the configured palette table based on the index information of each sample in the CU, prediction samples in the CU can be output. The decoder can then reconfigure each sample information in the CU using the palette information and update the palette predictor.

[125] Meanwhile, the above-described palette encoding (palette mode or palette encoding mode) can signal information for indicating whether the current CU is encoded in the palette mode, and encoding it by applying the palette mode to it.

[126] As an example, information about whether a palette encoding mode is available may be signaled by a sequence parameter set (SPS), as shown in Table 1 below.

[127] [Table 1]

[128] The semantics of the syntactic elements included in the syntax of Table 1 can be represented as shown in Table 2 below.

[129]

[Table 2] sps_palette_enabled_flag equal to 1 specifies that pred_mode_plt_flag may be present in the encoding unit syntax. sps_palette_enabled_flag equal to 0 specifies that pred_mode_plt_flag is not present in the encoding unit syntax. When sps_palette_enabled_flag is not present, it is assumed to be 0. Additionally, when decoding a coding unit (CU), a flag is enabled to indicate whether the CU is encoded in palette mode.

[130] With reference to Tables 1 and 2, the sps_palette_enabled_flag syntax element may be parsed/signaled in the SPS. The sps_palette_enabled_flag syntax element can indicate whether the palette encoding mode is enabled. For example, when the value of sps_palette_enabled_flag is 1, it may indicate that the palette encoding mode is enabled, in which case, information (e.g., pred_mode_plt_flag) indicating whether the palette encoding mode should be applied to the current encoding unit in the encoding unit syntax may be parsed /signal. When the value of sps_palette_enabled_flag is 0, it may indicate that the palette encoding mode is not available, in which case, information (for example, pred_mode_plt_flag) indicating whether the palette encoding mode mode should be applied to the current encoding unit in the encoding unit syntax may not be parsed /signal.

[131] Additionally, for example, information about whether to perform encoding by applying a palette mode may be signaled based on information about whether a palette encoding mode is available (eg, sps_palette_enabled_flag), and the information may be signaled via encoding unit syntax such as shown in Table 3 below.

[132] [Table 3]

[133] The semantics of the syntactic elements included in the syntax of Table 3 can be represented as shown in Table 4 below.

[134]

[Table 4] pred_mode_plt_flag specifies the use of the palette mode in the current encoding unit. pred_mode_plt_flag equal to 1 indicates that the palette mode is applied in the current encoding unit. pred_mode_plt_flag equal to 0 indicates that the palette mode is not applied in the current encoding unit. When pred_mode_plt_flag is not present, it is assumed to be 0. When pred_mode_plt_flag is zero, the variable CuPredMode[x][y] is set to MODE_PLT for x=x0...x0+cbWidth-1 and y=y0...y0+cbHeight-1.

[135] With reference to Tables 3 and 4, the pred_mode_plt_flag syntax element may be parsed/signaled in encoding unit syntax. The pred_mode_plt_flag syntax element may indicate whether the palette mode is applied to the current encoding unit. For example, when the value of pred_mode_plt_flag is 1, it may indicate that the palette mode is applied to the current encoding unit, and if the value of pred_mode_plt_flag is 0, it may indicate that the palette mode is not applied to the current encoding unit.

[136] In this case, pred_mode_plt_flag may be parsed/signaled based on information (eg, sps_palette_enabled_flag) about whether the palette encoding mode is available. For example, when the value of sps_palette_enabled_flag is 1 (i.e. when palette encoding mode is enabled), pred_mode_plt_flag may be parsed/signaled.

[137] Additionally, encoding can be performed by applying a palette mode to the current encoding unit based on pred_mode_plt_flag. For example, when the value of pred_mode_plt_flag is 1, the palette mode can be applied to the current encoding unit to generate a reconstructed sample by parsing/signaling the palette_coding() syntax.

[138] As an example, Table 5 below shows the palette encoding syntax.

[139] [Table 5]

[140]

[141]

[142] The semantics of the syntactic elements included in the syntax of Table 5 can be represented as shown in Table 6 below.

[143]

[Table 6] In the following semantics, the array indices x0, y0 specify the position (x0, y0) of the top-left luminance sample of the encoding block in question relative to the top-left luminance sample of the picture. The array indices xC, yC specify the position (xC, yC) of the sample relative to the top-left sample of the picture brightness. The startComp array index specifies the first color component of the current palette table. startComp equal to 0 indicates the Y component, startComp equal to 1 indicates the Cb component, startComp equal to 2 indicates the Cr component. numComp specifies the number of color components in the current palette table.
The predictor palette consists of palette entries from previous encoding units, which are used to predict the current palette entries.
The PredictorPaletteSize[startComp] variable specifies the predictor palette size for the first color component of the current startComp palette table. PredictorPaletteSize is output as specified in Section 1.4.
The variable PalettePredictorEntryReuseFlags[i] equal to 1 specifies that the i-th entry in the predictor palette is reused in the current palette. PalettePredictorEntryReuseFlags[i] equal to 0 specifies that the i-th entry in the predictor palette is not an entry in the current palette. All elements of the PalettePredictorEntryReuseFlags[i] array are initialized to 0.
palette_predictor_run is used to determine the number of zeros that precede a non-zero entry in the PalettePredictorEntryReuseFlags array.
A requirement for bitstream consistency is that the value of palette_predictor_run must be in the range 0 to (PredictorPaletteSize-predictorEntryIdx), inclusive, where predictorEntryIdx corresponds to the current position in the PalettePredictorEntryReuseFlags array. The NumPredictedPaletteEntries variable specifies the number of entries in the current palette that are reused from the predictor palette. The value of NumPredictedPaletteEntries must be in the range from 0 to palette_max_size, inclusive.
num_signalled_palette_entries specifies the number of entries in the current palette that are explicitly signaled for the first color component of the current palette startComp table.
If num_signalled_palette_entries is missing, it is assumed to be 0.
The CurrentPaletteSize[startComp] variable specifies the current palette size for the first color component of the startComp current palette table and is output as follows:

[144]

CurrentPaletteSize[startComp] must be in the range 0 to palette_max_size, inclusive.
new_palette_entries[cIdx][i] specifies the value for the i-th signaled palette entry for color component cIdx.
The variable PredictorPaletteEntries[cIdx][i] specifies the i-th element in the predictor palette for the color component cIdx.
The variable CurrentPaletteEntries[cIdx][i] specifies the i-th element in the current palette for the color component cIdx and is output as follows:

palette_escape_val_present_flag equal to 1 specifies that the current encoding unit contains at least one branch-encoded sample. escape_val_present_flag equal to 0 specifies that there are no branch-coded samples in the current encoding unit. If not present, palette_escape_val_present_flag is assumed to be 1.

[145]

The MaxPaletteIndex variable specifies the maximum possible value for the palette index for the current encoding unit. The MaxPaletteIndex value is set to CurrentPaletteSize[startComp] -1+palette_escape_val_present_flag.
num_palette_indices_minus1 plus 1 is the number of palette indices explicitly signaled or output for the current block.
If num_palette_indices_minus1 is not present, it is assumed to be 0.
palette_idx_idc is an indication of the index into the palette table, CurrentPaletteEntries. The value of palette_idx_idc must be in the range from 0 to (MaxPaletteIndex), inclusive, for the first index in the block, and in the range from 0 to (MaxPaletteIndex-1), inclusive, for the remaining indices in the block.
When palette_idx_idc is missing, it is assumed to be 0.
The variable PaletteIndexIdc[i] keeps the i-th palette_idx_idc explicitly signaled or output. All elements of the PaletteIndexIdc[i] array are initialized to 0.
copy_above_indices_for_final_run_flag equal to 1 specifies that the palette indices of the last positions in the encoding unit are copied from the palette indices in the row above if a horizontal cross-scan is used, or the palette indices in the left column if a vertical cross-scan is used. copy_above_indices_for_final_run_flag equal to 0 specifies that the palette indices of the last positions in the encoding unit are copied from PaletteIndexIdc[num_palette_indices_minus1].
If copy_above_indices_for_final_run_flag is not present, it is assumed to be 0.
palette_transpose_flag equal to 1 specifies that vertical transverse scanning is used to scan indices for samples in the current encoding unit. palette_transpose_flag equal to 0 specifies that a horizontal transverse scan is used to scan indices for samples in the current encoding unit. If absent, palette_transpose_flag is assumed to be 0.
The TraverseScanOrder array specifies an array of scan order to be palette encoded. TraverseScanOrder is assigned to the horizontal scan order HorTravScanOrder if

[146]

palette_transpose_flag is 0; and TraverseScanOrder is assigned the vertical scan order of VerTravScanOrder if palette_transpose_flag is 1.
copy_above_palette_indices_flag equal to 1 specifies that the palette index is equal to the palette index at the same location in the row above if a horizontal cross-scan is used, or the same position in the left column if a vertical cross-scan is used. copy_above_palette_indices_flag equal to 0 specifies that the sampling palette index indication is encoded in the bitstream or output.
The variable CopyAboveIndicesFlag[xC][yC] equal to 1 specifies that the palette index is copied from the palette index in the top row (horizontal scan) or left column (vertical scan). CopyAboveIndicesFlag[xC][yC] equal to 0 specifies that the palette index is explicitly encoded in the bitstream or output. The array indices xC, yC specify the location (xC, yC) of the sample relative to the top-left luminance sample of the picture. The PaletteIndexMap[xC][yC] value must be in the range 0 to (MaxPaletteIndex-1), inclusive.
The PaletteIndexMap[xC][yC] variable specifies a palette index, which is an index into the table represented by CurrentPaletteEntries. The array indices xC, yC specify the location (xC, yC) of the sample relative to the top-left luminance sample of the picture. The value of PaletteIndexMap[xC][yC] must be in the range from 0 to MaxPaletteIndex, inclusive.
The adjustedRefPaletteIndex variable is output as follows:

[147]

If CopyAboveIndicesFlag[xC][yC] is 0, then the CurrPaletteIndex variable is output as follows:

palette_run_prefix, if present, specifies the prefix portion in the PaletteRunMinus1 binarization.
palette_run_suffix is used in the output of the PaletteRunMinus1 variable. If missing, palette_run_suffix is assumed to be 0.
If RunToEnd is 0, then the PaletteRunMinus1 variable is output as follows:
- If PaletteMaxRunMinus1 is 0, then PaletteRunMinus1 is set to 0.
- Otherwise (PaletteMaxRunMinus1 is greater than 0), the following applies:
- If palette_run_prefix is less than 2, the following applies:
PaletteRunMinus1= palette_run_prefix
- Otherwise (palette_run_prefix is greater than or equal to 2), the following applies:

The PaletteRunMinus1 variable is used as follows:
- If CopyAboveIndicesFlag[xC][yC] is 0, PaletteRunMinus1 specifies the number of consecutive locations minus 1 with the same palette index.
- Else, if palette_transpose_flag is 0, PaletteRunMinus1 specifies the number of consecutive locations minus 1 with the same palette index as used in the corresponding location in the line above.

[148]

- Otherwise, PaletteRunMinus1 specifies the number of consecutive locations minus 1 with the same palette index as used at the corresponding location in the left column.
When RunToEnd is 0, the variable PaletteMaxRunMinus1 represents the maximum possible value for PaletteRunMinus1, and the bitstream consistency requirement is that the value of PaletteMaxRunMinus1 must be greater than or equal to 0.
palette_escape_val specifies the quantized value of the branch-encoded sample for the component.
The variable PaletteEscapeVal[cIdx][xC][yC] specifies the transition value of the selection for which PaletteIndexMap[xC][yC] is equal to MaxPaletteIbdex, and palette_escape_val_pesent_flag is equal to 1. The cIdx array index specifies the color component. The array indices xC, yC specify the location (xC, yC) relative to the top-left sample of the image brightness.
The requirement for bitstream consistency is that PaletteEscapeVal[cIdx][xC][yC] must be in the range 0 to (1<<(BitDepth _Y +1)) -1, inclusive, for cIdx equal to 0, and in range from 0 to ((1<<(BitDepth _C +1)) -1, inclusive, for cIdx not equal to 0.

[149] With reference to Tables 5 and 6, when a palette mode is applied to the current block (ie, the current coding unit), palette encoding syntax (eg, palette_coding()) as in Table 5 may be parsed/signaled.

[150] For example, the palette table may be configured based on the palette entry information. The palette entry information may include syntactic elements such as palette_predictor_run, num_signalled_palette_entries, and new_palette_entries.

[151] Additionally, you can configure a palette index map for the current block based on the palette index information. The palette index information may include syntax elements such as num_palette_indices_minus1, palette_idx_idc, copy_above_indices_for_final_run_flag, and palette_transpose_flag. Based on the palette index information as described above, it is possible to infer palette index values (eg, PaletteIndexIdc) for samples in the current block when passing in the transverse scanning direction (vertical direction or horizontal direction) to configure a palette index map (eg, PaletteIndexMap).

[152] Additionally, you can output the sample value for a palette entry in the palette table based on the palette index map, and generate reconstructed samples of the current block based on the sample value (ie, color value) mapped to the palette entry.

[153] When the sample has a transition value in the current block (ie, when the palette_escape_val_present_flag value is 1), the transition value for the current block can be inferred based on the transition information. The transition information may include syntactic elements such as palette_escape_val_present_flag and palette_escape_val. For example, the transition value for a transition-coded sample in the current block may be inferred based on the quantized transition value information (eg, palette_escape_val). Reconstructed samples of the current block can be generated based on the transition value.

[154] As described above, information (syntax elements) in the syntax table disclosed in the present disclosure may be included in image/video information configured/encoded in accordance with an encoding method (including palette encoding) performed in an encoding apparatus and delivered to a decoding device in the form of a bit stream. The decoding apparatus may parse/decode information (syntax elements) in the syntax table. The decoding apparatus may perform an encoding method such as palette encoding based on the decoded information, and may perform a block/image/video reconstruction (decoding) procedure on this basis. Further, the present disclosure provides a syntax table and syntax elements for efficient block/image/video encoding based on palette encoding.

[155] The present disclosure provides a method for efficiently encoding and signaling transition values in palette mode encoding. In palette mode, transition values can be used to optionally convey the corresponding sample value for a sample that has a different value from those of adjacent samples in the block. Since such transition values are additional data, quantization can be performed to save transition values. Additionally, when transition encoding is in palette mode, no transform is applied and the quantized value of the transition can be directly signaled. This can be thought of as similar to skip transform mode, in which no transform is applied to the coding unit (CU).

[156] In the current VVC standard, the full range of quantization parameter (QP) values is applied to transition values in palette mode. However, the present disclosure provides a method for limiting the range of QP values to prevent the quantization step size for encoding a transition value in palette mode from becoming less than 1. In one embodiment, the same constraint as the minimum QP for skipping a transform may apply to transition value encoding in palette mode. The minimum QP for palette mode can be limited using the minimum QP to skip transformation.

[157] As an example, information about the minimum QP to skip conversion may be signaled by a Sequence Parameter Set (SPS), as shown in Table 7 below.

[158] [Table 7]

[159] The semantics of the syntactic elements included in the syntax of Table 7 can be represented as shown in Table 8 below.

[160]

[Table 8] min_qp_prime_ts_minus4 specifies the minimum allowed quantization parameter for skip transform mode as follows:
QpPrimeTsMin= 4+min_qp_prime_ts_minus4
min_qp_prime_ts_minus4 is signaled in the SPS and is usually specified by 6*(inputBitDepth-8).

[161] With reference to Tables 7 and 8, the min_qp_prime_ts_minus4 syntax element may be parsed/signaled in the SPS. The min_qp_prime_ts_minus4 syntax element may specify the minimum quantization parameter allowed for transform skip mode. In other words, the minimum value of a quantization parameter (eg, QpPrimeTsMin) in skip mode may be inferred based on the min_qp_prime_ts_minus4 syntax element. For example, the minimum value of the quantization parameter (eg, QpPrimeTsMin) can be derived by summing 4 with the value min_qp_prime_ts_minus4.

[162] As described above, based on the min_qp_prime_ts_minus4 syntax element signaled by the SPS, the QP for palette mode transition values can be output as in the algorithm disclosed in Table 9 below. That is, the QP value used to reconfigure the transition value in palette mode may be output as in the algorithm disclosed in Table 9 below.

[163]

[Table 9] Otherwise (bIsEscapeSample is equal to 1 and cu_transquant_bypass_flag is equal to 0), the following order of steps is applied:
1. The quantization parameter qP is derived as follows:
- If cIdx is 0,
qP=Max(QpPrimeTsMin, Qp'Y)
- Otherwise, if cIdx is 1,
qP=Max(QpPrimeTsMin, Qp'Cb)
- Otherwise (cIdx equals 2),
qP=Max(QpPrimeTsMin, Qp'Cr)
2. The bitDepth variable is output as follows:

3. The list levelScale[] is specified as levelScale[k]={40, 45, 51, 57, 64, 72} with k=0..5.
4. The following applies:

[164] With reference to Table 9, when a palette mode transition value exists, a QP value may be output. That is, the QP for the palette mode transition value may be inferred based on the minimum value of the quantization parameter (eg, QpPrimeTsMin) in transform skip mode inferred based on the min_qp_prime_ts_minus4 syntax element described above. For example, as shown in Table 9, the QP for palette mode transition values may be output as the greater of the value between QpPrimeTsMin and the quantization parameter Qp (Qp'Y for the luma component and Qp'Cb or Qp'Cr for the chrominance component). Then, the transition value can be inferred based on the QP for the palette mode transition values to reconstruct the selections in the block.

[165] Additionally, in the present disclosure, as described above, when the range of QP in palette mode is limited to be greater than or equal to the minimum value of the quantization parameter (e.g., QpPrimeTsMin) in transform skip mode, the range of transition values quantized in palette mode may be limited. As an embodiment, the range of transition values quantized in palette mode may be determined based on the bit depth and may be limited to be no greater than, for example, (1<<BitDepth)-1.

[166] For example, a transition value quantized in palette mode may be represented by the palette_escape_val syntax element. The palette_escape_val syntax element may be signaled via palette encoding syntax, as shown in Table 10 below.

[167] [Table 10]

[168] The semantics of the syntactic elements included in Table 10 can be represented as shown in Table 11 below.

[169]

[Table 11] palette_escape_val specifies the quantized value of the branch-encoded sample for the component.
The variable PaletteEscapeVal[cIdx][xC][yC] specifies the transition value of the selection for which PaletteIndexMap[xC][yC] is equal to MaxPaletteIndex and palette_escape_val_present_flag is equal to 1. The array index cIdx specifies the color component. The array indices xC, yC specify the location (xC, yC) of the sample relative to the top-left luminance sample of the picture.
The bitstream consistency requirement is that PaletteEscapeVal[cIdx][xC][yC] must be in the range from 0 to (1<<(BitDepth _Y ))-1, inclusive, for cIdx equal to 0, and in the range from 0 up to (1<<(BitDepth _C ))-1, inclusive, for cIdx not equal to 0.

[170] With reference to Tables 10 and 11, the palette_escape_val syntax element may be parsed/signaled in palette encoding syntax. The palette_escape_val syntax element may indicate the quantized value of the transition. Additionally, as shown in Table 10, the value of the palette_escape_val syntax element can be set to PaletteEscapeVal, and PaletteEscapeVal can indicate the value of a selection transition in which the palette index map (PaletteIndexMap) is equal to the maximum palette index (MaxPaletteIndex) and the value of palette_escape_val_present_flag is 1. Here, the case , where the value of palette_escape_val_present_flag is 1, may indicate that at least one transition-coded sample (transition value) is included in the current CU. For example, for the luminance component, PaletteEscapeVal can be limited to the range from 0 to (1<<(BitDepthY)-1). For the chroma component, PaletteEscapeVal can be limited to the range from 0 to (1<<(BitDepthC))-1.

[171] Additionally, the present disclosure provides a method for determining a palette size and signaling it. The palette size can indicate the number of entries in the palette table (that is, the number of indexes in the palette table). As an embodiment, in the present disclosure, the number of palette entries may be specified by defining the palette size using one or more constants.

[172] As an example, the palette size may be represented by the palette_max_size syntax element, and the palette_max_size syntax element may be the same for the entire sequence or may be different according to the size of the CU (ie, the number of pixels in the CU). For example, the palette size (palette_max_size) may indicate the maximum valid palette table index, and may be defined as 31. As another example, the palette size (palette_max_size) may indicate the maximum valid palette table index, and may be defined as shown in Table 12 below according to CU size.

[173]

[Table 12] if (cbWidth*cbHeight>=1024)
palette_max_size defined as 63
otherwise if cbWidth*cbHeight>=256
palette_max_size is defined as 31
otherwise,
palette_max_size is defined as 15

[174] Palette sizes 63, 31, 15, etc. and CU sizes 1024, 256, etc. disclosed in Table 12 are used as examples only and may be changed to other numbers.

[175] As an embodiment, information indicating the size of the palette (eg, palette_max_size) may be signaled by the SPS, as shown in Table 13 below.

[176] [Table 13]

[177] The semantics of the syntactic elements included in the syntax of Table 13 can be represented as shown in Table 14 below.

[178]

[Table 14] palette_max_size specifies the maximum palette table index allowed and must be in the range 1 to 63 inclusive.

[179] With reference to Tables 13 and 14 above, the palette_max_size syntax element may be parsed/signaled in a syntax element in the SPS. The palette_max_size syntax element can specify the maximum allowed palette table index and can be limited to the range 1 to 63.

[180] In this case, the palette_max_size syntax element may be parsed/signaled based on the sps_palette_enabled_flag syntax element, which is information for indicating whether the palette mode is enabled. For example, when the value of sps_palette_enabled_flag is 1 (ie when it indicates that palette mode is enabled), the palette_max_size syntax element may be parsed/signaled.

[181] Alternatively, as an embodiment, information indicating the size of the palette (eg, log2_palette_max_size) may be signaled by the SPS, as shown in Table 15 below.

[182] [Table 15]

[183] The semantics of the syntactic elements included in the syntax of Table 15 can be represented as shown in Table 16 below.

[184]

[Table 16] log2_palette_max_size specifies log2 of (palette_max_size+1), palette_max_size=(1<<log2_palette_max_size)-1. palette_max_size specifies the maximum palette table index allowed and must be in the range 1 to 63, inclusive.

[185] With reference to Tables 15 and 16, the log2_palette_max_size syntax element can be parsed/signaled in the SPS. The log2_palette_max_size syntax element may specify a log2 value of the palette size (ie, palette_max_size+1). Accordingly, palette_max_size, indicating the maximum allowed palette table index, can be derived by computing (1<< log2_palette_max_size)-1 and can be limited to the range from 1 to 63.

[186] In this case, the log2_palette_max_size syntax element may be parsed/signaled based on the sps_palette_enabled_flag syntax element, which is information for indicating whether the palette mode is enabled. For example, when the value of sps_palette_enabled_flag is 1 (ie when it indicates that palette mode is enabled), the log2_palette_max_size syntax element can be parsed/signaled.

[187] Alternatively, as an embodiment, information indicating the palette size (eg, log2_palette_CU_size_TH1, log2_palette_max_size_TH1, log2_palette_max_size_default) may be signaled by the SPS, as shown in Table 17 below.

[188] [Table 17]

[189] The semantics of the syntactic elements included in the syntax of Table 17 can be represented as shown in Table 18 below.

[190]

[Table 18] log2_palette_CU_size_TH1 specifies log2 of the size limit palette_max_size_TH1. palette_CU_size_TH1=1<<log2_palette_CU_size_TH1
log2_palette_max_size_TH1 specifies log2 of (palette_max_size_TH1+1). (palette_max_size_TH1=(1<<log2_palette_max_size_TH1)-1. palette_max_size_TH1 specifies the maximum allowed palette table index for a CU with a size larger than palette_CU_size_TH1, and must be in the range 1 to 63 inclusive.
log2_palette_max_size_default specifies log2 of (palette_max_size_default+1). palette_max_size_default=(1<<log2_palette_max_size_default)-1. palette_max_size_default specifies the maximum palette table index allowed and must be in the range 1 to 63 inclusive.
The variable palette_max_size specifies the maximum allowed palette table index and is output as follows:

[191] With reference to Tables 17 and 18, the syntax elements log2_palette_CU_size_TH1, log2_palette_max_size_TH1 and log2_palette_max_size_default can be parsed/signaled in the SPS.

[192] The log2_palette_CU_size_TH1 syntax element specifies the log2 size limit value of palette_max_size_TH1, and palette_max_size_TH1 may be output as 1<< log2_Palette_CU_size_TH1.

[193] The log2_palette_max_size_TH1 syntax element specifies the log2 value of (palette_max_size_TH1+1), and palette_max_size_TH1 may be output as (1<< log2_palette_max_size_TH1)-1. palette_max_size_TH1 specifies the maximum allowed palette table index for a CU larger than Palette_CU_size_TH1 and can be limited to a range of 1 to 63.

[194] The log2_palette_max_size_default syntax element specifies the log2 value of (palette_max_size_default+1), and palette_max_size_default can be output as (1<< log2_palette_max_size_default)-1. palette_max_size_default specifies the maximum palette table index allowed and can be limited to a range of 1 to 63.

[195] Here, the syntax elements log2_palette_CU_size_TH1, log2_palette_max_size_TH1 and log2_palette_max_size_default can be parsed/signaled based on the syntax element sps_palette_enabled_flag, which is information for indicating whether the palette mode is enabled. For example, when the value of sps_palette_enabled_flag is 1 (that is, when it indicates that palette mode is enabled), the syntax elements log2_palette_CU_size_TH1, log2_palette_max_size_TH1, and log2_palette_max_size_default can be parsed/signaled.

[196] Also, one or more sets of palette_CU_size_TH and palette_max_size_TH may be signaled and used to indicate palette_max_size.

[197] The following drawings have been created to explain a specific example of the present disclosure. The names or specific terms or names of specific devices illustrated in the drawings (e.g., syntax terms/syntactic elements, etc.) are presented by way of example, and thus the technical features of the present disclosure are not limited to the specific names used in the drawings below .

[198] FIG. 9 schematically shows an example of a video/image encoding method in accordance with embodiment(s) of the present disclosure.

[199] The method disclosed in FIG. 9 may be performed by the encoding device 200 illustrated in FIG. 2. Specifically, steps S900 and S910 in FIG. 9 may be performed by the predictor 220 illustrated in FIG. 2, and step S920 in FIG. 9 may be performed by the entropy encoder 240 illustrated in FIG. 2. Additionally, the method disclosed in FIG. 9 may include the embodiments described above in this disclosure. Accordingly, in FIG. 9, a detailed description of the redundant parts of FIG. 9 and the above-described embodiments will be omitted or simplified.

[200] With reference to FIG. 9, the encoder can output a palette mode transition value for the current block (S900).

[201] As an embodiment, the encoder may determine a prediction mode for the current block and perform the prediction. For example, the encoder may determine whether to perform inter-prediction or intra-prediction on the current block. Alternatively, the encoder may determine whether to perform prediction on the current block based on a CIIP mode, an IBC mode, or a palette mode. The encoder may determine the prediction mode based on the RD cost. The encoder may perform prediction in accordance with a certain prediction mode to output prediction samples for the current block. Additionally, the encoding device may generate and encode information (eg, prediction mode information) related to the prediction applicable to the current block.

[202] When executing the prediction-based palette mode on the current block, the encoding device may apply the palette mode encoding disclosed in the above-described embodiments. That is, the encoder can output palette entries, palette indices, transition values, and the like by applying palette mode encoding to the current block.

[203] As an example, the encoder may generate palette entry information based on the sample values of the current block. That is, the encoding device may output palette predictor entries and palette entry reuse information used in a block encoded in a previous palette mode to configure a palette table, and may output palette entries for the current block. For example, as shown in Tables 5 and 6, the encoder may output palette entry information such as palette_predictor_run, num_signalled_palette_entries, and new_palette_entries used to configure the palette table.

[204] Additionally, the encoder may generate palette index information for the current block based on the palette entry information. That is, the encoder may output the palette index value of each sample as it traverses the samples of the current block in the transverse scanning direction (vertical direction or horizontal direction) and configure the palette index map. For example, as shown in Tables 5 and 6 above, the encoding device may output palette entry information such as palette_transpose_flag, palette_idx_idc, COPY_ABOVE_indices_for_final_run_flag, num_palette_indices_minus1 used to configure the palette index map.

[205] Here, the palette table may include representative color values (palette entries) for samples in the current block and may consist of palette index values corresponding to the corresponding color values. That is, the encoding device may output a palette index value corresponding to an entry (color value) in the palette table for each sample in the current block and signal it to the decoding device.

[206] The encoding device can encode image information including palette entry information and palette index information and signal it to the decoding device.

[207] Additionally, when executing a prediction-based palette mode on a current block, the encoder may output a transition value for the current block including at least one transition-encoded sample.

[208] As described above, since it is effective to additionally transmit a corresponding sample value for a sample having a value different from those of adjacent samples in the current block in palette mode, from the point of view of encoding efficiency, this sample value may be signaled as a transition value. In this case, since the transition value is additional data, quantization can be performed to save it. In addition, the transformation is not applied to the palette mode transition value, and the quantized value can be directly signaled.

[209] The encoding device may output a quantized transition value based on the transition value (S910).

[210] As an embodiment, the encoder may output a quantized transition value by applying a quantization parameter for the transition value to the transition value.

[211] Here, a quantization parameter may be derived based on the minimum quantization parameter information regarding the skip conversion mode. For example, the quantization parameter may be inferred based on the minimum quantization parameter information (eg, min_qp_prime_ts_minus4) regarding the transform skip mode shown in Tables 7-9. As described above, since the transform is not applied to the palette mode transition value, the transition value may be quantized based on the minimum quantization parameter information used in the transform skip mode.

[212] As a specific example, as shown in Table 9, first, the encoder may output a minimum quantization parameter value (eg, QpPrimeTsMin) based on the minimum quantization parameter information (eg, min_qp_prime_ts_minus4) regarding the transform skip mode. Additionally, the encoder may select the greater value between the minimum value of the quantization parameter (eg, QpPrimeTsMin) and the quantization parameter Qp (Qp'Y for the luma component and Qp'Cb or Qp'Cr for the chrominance component) and use it as the quantization parameter in the mode palettes.

[213] In other words, the palette mode quantization parameter may have a value greater than or equal to the minimum quantization parameter value (eg, QpPrimeTsMin) derived from the minimum quantization parameter information (eg, min_qp_prime_ts_minus4) regarding the transform skip mode.

[214] The encoder may output the quantized transition value using the palette mode quantization parameter output as described above. The encoder may generate the quantized transition value as a palette_escape_val syntax element, as shown in Tables 5 and 6, and signal it. Additionally, the encoder may generate information (eg, palette_escape_val_present_flag) to indicate that a sample having a transition value is present in the current block and signal it.

[215] According to an embodiment, the encoder may limit the quantized transition value to a specific range. Because transition values have different characteristics from those of neighboring samples, they are quantized and signaled directly. However, an error may occur due to quantization. To reduce such error and encode a more accurate value, the range of the quantized transition value can be limited based on the bit depth.

[216] For example, the range of the quantized transition value information may be determined based on the bit depth, as shown in Tables 10 and 11, and may be limited to be no greater than (1<<BitDepth)-1, for example. Additionally, the bit depth may include a bit depth BitDepthY for the luma component and a bit depth BitDepthC for the chrominance component. Here, the range of quantized transition value information for the luma component may have a value between 0 and (1<<BitDepthY)-1, and the range of quantized transition value information for the chrominance component may have a value between 0 and (1<<BitDepthC)-1.

[217] Additionally, in one embodiment, the encoding device may determine the number of entries in the palette table (ie, the number of palette table indices) and signal it to the decoding device. That is, the encoding device may determine palette size information regarding the maximum index of the palette table and signal it. The palette size information may be a preset value or may be determined based on the encoding unit size.

[218] For example, the palette size may be represented by palette_max_size, as shown in Table 12, may be the same for the entire sequence, or may be defined differently according to the size of the CU (ie, the number of pixels in the CU).

[219] For example, the palette size may be represented as palette_max_size, as shown in Tables 13 and 14, and may be signaled by the SPS. In this case, the palette size (eg, palette_max_size) may indicate the maximum enabled palette table index and may be limited to a range from 1 to 63. Additionally, the palette size (eg, palette_max_size) may be signaled based on information (eg, sps_palette_enabled_flag) to indicate whether palette mode is enabled.

[220] Additionally, for example, the palette size may be represented as log2_palette_max_size, as shown in Tables 15 and 16, and may be signaled by SPS. In this case, the palette size (eg, log2_palette_max_size) may indicate a log2 value of the palette size (ie, palette_max_size+1). Accordingly, palette_max_size, indicating the maximum allowed index of the palette table, may be derived by calculating (1<<log2_palette_max_size)-1 and may be limited to a range from 1 to 63. Additionally, the palette size (eg, log2_palette_max_size) may be signaled based on information (eg , sps_palette_enabled_flag) to indicate whether palette mode is enabled.

[221] Additionally, for example, the palette size may be inferred based on log2_palette_CU_size_TH1, log2_palette_max_size_TH1, and log2_palette_max_size_default, as shown in Tables 17 and 18, and may be signaled by SPS. Since a specific embodiment of palette size output and signaling has been described above in Tables 17 and 18, their description will be omitted here.

[222] The encoding device may encode image information (or video information) (S920). Here, the image information may include various types of information used for the above-described palette mode encoding.

[223] As an example, an encoder may generate and encode image information, including information about quantized transition values. Additionally, the encoding device can generate and encode image information including palette entry information and palette index information. Additionally, the encoding device can generate and encode image information, including minimum quantization parameter information regarding the skip transform mode. In this case, the image information may include the SPS, and the SPS may include minimum quantization parameter information regarding the skip conversion mode.

[224] Additionally, according to an embodiment, the encoding device may determine whether to perform encoding on the current block using the palette mode described above based on information about whether the palette mode is turned on.

[225] For example, as shown in Tables 1-4, the encoder may determine whether the palette mode is enabled, generate information (eg, sps_palette_enabled_flag) about whether the palette mode is enabled according to the determination, and signal the information via the SPS.

[226] Additionally, the encoder may generate information (eg, pred_mode_plt_flag) indicating whether the current block should be encoded by applying a palette mode to it based on information (eg, sps_palette_enabled_flag) about whether the palette mode is enabled, and signal the information by coding unit syntax. For example, when the value of pred_mode_plt_flag is 1, it is possible to apply a palette mode to the current block to generate a reconstructed sample by signaling palette_coding() syntax.

[227] Information indicating whether a palette mode is enabled (eg, sps_palette_enabled_flag) and information indicating whether the current block should be encoded by applying a palette mode to it (eg, pred_mode_plt_flag) may be encoded by including an image in the information.

[228] Image information, including various types of information as described above, may be encoded and output in the form of a bit stream. The bitstream may be transmitted to the decoding device via a network or a (digital) storage medium. Here, the network may include a broadcast network and/or a communications network, and the digital storage medium may include various storage media such as USB, SD, CD, DVD, Blu-ray, HDD and SSD.

[229] FIG. 10 schematically shows an example of a video/image decoding method in accordance with embodiment(s) of the present disclosure.

[230] The method disclosed in FIG. 10 may be performed by the decoding apparatus 300 illustrated in FIG. 3. Specifically, step S1000 in FIG. 10 may be performed by the entropy decoder 310 illustrated in FIG. 3, and steps S1010 and S1020 in FIG. 10 may be performed by the predictor 330 illustrated in FIG. 3. Also, the method disclosed in FIG. 10 may include the embodiments described above in the present disclosure. Accordingly, in FIG. 10, a detailed description of the redundant parts in FIG. 10 and the above-described embodiments will be omitted or simplified.

[231] With reference to FIG. 10, the decoding apparatus may receive image information (or video information) from the bitstream (S1000).

[232] The decoding apparatus may parse the bitstream to output information (eg, video/image information) necessary for image reconstruction (or picture reconstruction). In this case, the image information may include prediction-related information (eg, prediction mode information). Additionally, the image information may include various types of information used for the palette mode encoding described above. For example, the image information may include information about quantized transition values, palette entry information, palette index information, minimum quantization parameter information regarding a skip transform mode, and the like. That is, the image information may include various types of information required in a decoding process, and may be decoded based on a coding method such as exponential Golomb coding, CAVLC, or CABAC.

[233] As an embodiment, the decoding apparatus may obtain image information, including quantized palette mode transition value information, from the bit stream. For example, the quantized transition value information may be a syntax element palette_escape_val, as shown in Tables 5 and 6. In this case, the quantized transition value information (for example, palette_escape_val) can be obtained based on information (for example, palette_escape_val_present_flag) indicating whether a sample that has a transition value in the current block. For example, when a sample having a transition value exists in the current block (ie, when the value of palette_escape_val_present_flag is 1), the decoding apparatus may obtain quantized transition value information (eg, palette_escape_val) from the bitstream.

[234] The decoding apparatus may output a transition value for the current block based on the quantized transition value information (S1010).

[235] As an embodiment, the decoding device may output a transition value by performing a dequantization (scaling process) on the quantized transition value based on the quantization parameter.

[236] Here, a quantization parameter may be derived based on the minimum quantization parameter information regarding the skip conversion mode. For example, the quantization parameter may be inferred based on the minimum quantization parameter information (eg, min_qp_prime_ts_minus4) regarding the transform skip mode shown in Tables 7-9. As described above, since the transform is not applied to the palette mode transition value, the transition value can be quantized based on the information of the minimum quantization parameter used in the transform skip mode. Here, minimum quantization parameter information (eg, min_qp_prime_ts_minus4) regarding the transform skip mode can be parsed/signaled from the SPS.

[237] As a specific example, as shown in Table 9, first, the decoding apparatus may output a minimum quantization parameter value (eg, QpPrimeTsMin) based on the minimum quantization parameter information (eg, min_qp_prime_ts_minus4) regarding the transform skip mode. Additionally, the decoder may select the greater value between the minimum value of the quantization parameter (eg, QpPrimeTsMin) and the quantization parameter Qp (Qp'Y for the luma component and Qp'Cb or Qp'Cr for the chrominance component) and use it as the quantization parameter in the mode palettes.

[238] In other words, the palette mode quantization parameter may have a value greater than or equal to the minimum quantization parameter value (eg, QpPrimeTsMin) derived from the minimum quantization parameter information (eg, min_qp_prime_ts_minus4) regarding the transform skip mode.

[239] The decoding apparatus may derive a transition value from the quantized transition value based on the palette mode quantization parameter derived as described above.

[240] According to an embodiment, the decoding device may limit the quantized transition value to a specific range. Because transition values have different characteristics from those of neighboring samples, they are quantized and signaled directly. However, an error may occur due to quantization. To reduce such error and encode a more accurate value, the range of the quantized transition value can be limited based on the bit depth.

[241] For example, the range of the quantized transition value information may be determined based on the bit depth, as shown in Tables 10 and 11, and may be limited to be no greater than (1<<BitDepth)-1, for example. Additionally, the bit depth may include a bit depth BitDepthY for the luma component and a bit depth BitDepthC for the chrominance component. Here, the range of quantized transition value information for the luma component may have a value between 0 and (1<<BitDepthY)-1, and the range of quantized transition value information for the chrominance component may have a value between 0 and (1<<BitDepthC)-1.

[242] Additionally, in one embodiment, the decoding apparatus may obtain image information, including the number of palette table entries (ie, the number of palette table indices). That is, the decoding device can obtain image information including palette size information regarding the maximum index of the palette table. Here, the palette size information may be a preset value or may be determined based on the encoding unit size.

[243] For example, the palette size may be represented as palette_max_size, as shown in Table 12, may be the same for the entire sequence, or may be defined differently according to the size of the CU (ie, the number of pixels in the CU).

[244] For example, the palette size may be represented as palette_max_size, as shown in Tables 13 and 14, and may be parsed/signaled by the SPS. In this case, the palette size (eg, palette_max_size) may indicate the maximum allowed index of the palette table and may be limited to the range from 1 to 63. Additionally, the palette size (eg, palette_max_size) may be parsed/signaled based on the information (eg, sps_palette_enabled_flag ) to indicate whether palette mode is enabled.

[245] Additionally, for example, the palette size can be represented as log2_palette_max_size, as shown in Tables 15 and 16, and can be parsed/signaled by SPS. In this case, the palette size (eg, log2_palette_max_size) may indicate the log2 value of the palette size (ie, palette_max_size+1). Accordingly, palette_max_size, indicating the maximum allowed index of the palette table, can be derived by computing (1<<log2_palette_max_size)-1 and can be limited to the range from 1 to 63. Additionally, the palette size (e.g., log2_palette_max_size) can be parsed/signaled based on information (for example, sps_palette_enabled_flag) to indicate whether palette mode is enabled.

[246] Additionally, for example, the palette size may be inferred based on log2_palette_CU_size_TH1, log2_palette_max_size_TH1, and log2_palette_max_size_default, as shown in Tables 17 and 18, and may be parsed/signaled by SPS. Since a specific embodiment of palette size inference and parsing/signaling has been described above in Tables 17 and 18, a description thereof will be omitted here.

[247] The decoding apparatus may generate reconstructed samples based on the transition value (S1020).

[248] As an embodiment, the decoding apparatus may generate reconstructed samples based on a branch value relative to a current block including at least one branch-encoded sample. For example, if there is a sample having a transition value in the current block (ie, when the value of palette_escape_val_present_flag is 1), the decoder may output the transition value as described above to generate a reconstructed sample of the transition-encoded sample.

[249] Additionally, when executing the prediction-based palette mode on the current block (that is, when the palette mode is applied to the current block), for samples other than the transition-coded samples in the current block, the decoding device can obtain image information, including recording information palette and palette index information, and generate reconstructed samples based on the received image information.

[250] As an example, the decoding device may configure a palette table for the current block based on the palette entry information. For example, the palette entry information may include palette_predictor_run, num_signalled_palette_entries, new_palette_entries and the like, as shown in Tables 5 and 6. That is, the decoding device may output the palette predictor entries and palette entry reuse information used in the block encoded in the previous palette mode, and output palette entries for the current block to configure the palette table. Additionally, the decoder may configure the palette table based on previous palette predictor entries and current palette entries.

[251] Additionally, the decoding apparatus may configure a palette index map for the current block based on the palette index information. For example, the palette index information may include palette_transpose_flag, palette_idx_idc, COPY_ABOVE_indices_for_final_run_flag, num_palette_indices_minus1 and the like used to configure a palette index map, as shown in Tables 5 and 6. That is, the decoding device may configure a palette index map (e.g., PaletteIndexMap) based on information (eg, palette_idx_idc) indicating the palette index value of each sample when traversing the selections of the current block based on information (eg, palette_transpose_flag) indicating the transverse scanning direction (vertical direction or horizontal direction).

[252] Additionally, the decoder may output sample values for palette entries in the palette table based on the palette index map. The decoder may generate reconstructed samples based on the palette index map and sample values for the palette entries.

[253] Here, the palette table may include representative color values (palette entries) for samples in the current block and may consist of palette index values corresponding to the corresponding color values. Accordingly, the decoding apparatus may output sample values (ie, color values) of entries in the palette table corresponding to the index values of the palette index map, and generate them as reconstructed sample values of the current block.

[254] Additionally, according to an embodiment, the decoding apparatus may determine whether to perform encoding on the current block using the palette mode described above based on information about whether the palette mode is enabled.

[255] For example, as shown in Tables 1-4, the decoding apparatus may obtain image information including information (eg, s_palette_enabled_flag) about whether the palette mode is enabled, and, based on this information, obtain palette entry information, palette index information , quantized transition value information and the like from the bit stream.

[256] Additionally, for example, the decoding device may obtain information (eg, pred_mode_plt_flag) indicating whether the current block should be encoded by applying palette mode to it from the bitstream based on information (eg, sps_palette_enabled_flag) about whether palette mode is enabled. . For example, when the value of pred_mode_plt_flag is 1, the decoding device may further obtain the palette_coding() syntax and apply a palette mode to the current block based on the information included in the palette_coding() syntax to obtain reconstructed samples.

[257] In the exemplary system described above, the methods are described in accordance with a flow chart using a sequence of steps and blocks. However, this document is not limited to a particular order of steps, and some steps may be performed with other steps and in a different order than described above, or simultaneously. Also, those skilled in the art will understand that the steps shown in the sequence flowchart are not exclusive, and other steps may be additionally included, or one or more steps from the sequence flowchart may be deleted without affecting the technical scope of this document.

[258] The method according to the present document may be in the form of software, and the encoding device and/or the decoding device according to the present document may be included in a device for performing image processing, for example, a TV, computer, smartphone, set-top box, display device or the like.

[259] When embodiments of the present document are implemented by software, the above method may be implemented by a module (process or function) that performs the above function. The module can be stored in memory and executed by the processor. The memory may be located inside or outside the processor and may be coupled to the processor through various well known means. The processor may include an application specific integrated circuit (ASIC), other chipsets, logic circuitry, and/or data processing apparatus. The memory may include read only memory (ROM), random access memory (RAM), flash memory, memory card, storage medium, and/or other storage device. In other words, embodiments according to this document may be implemented and executed on a processor, microprocessor, controller, or chip. For example, the functional modules illustrated in the respective drawings may be implemented and executed on a computer, processor, microprocessor, controller, or chip. In this case, implementation information (eg, instruction information) or algorithms may be stored in a digital storage medium.

[260] In addition, the decoding device and encoding device to which the present disclosure is applied may be included in a multimedia broadcast transceiver, mobile communication terminal, home theater device, digital cinema device, surveillance camera, video talking device, communication device in such as video communication, mobile streaming device, storage medium, camera recorder, video on demand (VoD) service provider, over-the-top (OTT) video delivery device, Internet streaming service provider, 3D video device, virtual reality device reality (VR), augmented reality (AR) device, video phone device for transmitting images, vehicle terminal (for example, a vehicle terminal (including an autonomous vehicle), an on-board terminal or a ship terminal) and a medical video device; and can be used to process signal or image data. For example, an OTT video device may include a game console, Blu-ray player, Internet-enabled television, home theater system, smartphone, tablet PC, digital video recorder (DVR).

[261] Moreover, the processing method employing the embodiment(s) of the present disclosure may be in the form of a computer-executable program and may be stored in a computer-readable recording medium. Multimedia data having a data structure in accordance with embodiment(s) of the present disclosure may also be stored in computer-readable recording media. The computer-readable recording medium includes all types of storage devices and distributed storage devices in which computer-readable data is stored. Computer-readable recording media may include, for example, Blu-ray disc (BD), universal serial bus (USB), ROM, PROM, EPROM, EEPROM, RAM, CD-ROM, magnetic tape, floppy disk, and optical device data storage. Additionally, the computer-readable recording medium includes media embodied in the form of a carrier wave (eg, transmission over the Internet). In addition, the bitstream generated by the encoding method can be stored in a computer-readable recording medium or transmitted over wired/wireless communication networks.

[262] Additionally, the embodiment(s) of the present disclosure may be implemented as a computer program product based on program code, and the program code may be executed on a computer in accordance with the embodiment(s) of the present disclosure. The program code may be stored on a computer-readable medium.

[263] FIG. 11 shows an example of a content streaming system to which embodiments of the present disclosure may be applied.

[264] With reference to FIG. 11, a content streaming system to which embodiments of the present disclosure are applied may generally include an encoding server, a streaming server, a web server, a media storage device, a user equipment, and a multimedia input device.

[265] The encoding server functions to compress digital data of content input from multimedia input devices such as a smartphone, camera, dash cam, etc. to generate a bit stream and transmit it to the streaming server. As another example, when a multimedia input device such as a smartphone, camera, dash cam and the like directly generates a bitstream, the encoding server may be omitted.

[266] The bitstream may be generated by an encoding method or a bitstream generation method that employs embodiments of the present disclosure, and the streaming server may temporarily store the bitstream during the process of transmitting or receiving the bitstream.

[267] The streaming server transmits media data to the user equipment based on the user's request through a web server, which functions as a tool that informs the user about the service. When a user requests a desired service, the web server forwards the request to the streaming server, and the streaming server transmits the media data to the user. In this regard, the content streaming system may include a separate control server, in which case, the control server functions to manage commands/responses between associated equipment in the content streaming system.

[268] The streaming server may receive content from a media storage and/or encoding server. For example, when content is received from an encoding server, the content may be received in real time. In this case, to provide a smooth streaming service, the streaming server may store the bitstream for a predetermined period of time.

[269] For example, user equipment may include a mobile phone, smartphone, laptop, digital broadcast terminal, personal digital assistant (PDA), portable media player (PMP), navigation device, slim PC, tablet PC, ultrabook, wearable device (eg , watch type terminal (smart watch), glasses type terminal (smart glasses), head mounted display (HMD)), digital TV, desktop computer, digital pointer and the like.

[270] Each of the servers in the content streaming system may operate as a distributed server, in which case, data received by each server may be processed in a distributed manner.

[271] The claims described in this disclosure may be combined in various ways. For example, the technical features in the method claims herein may be combined to be implemented or performed in an apparatus, and the technical features in the device claims may be combined to be implemented or performed in a method. In addition, technical features in the method claims and device claims may be combined to be implemented or performed in the device. In addition, technical features in the method claims and in the device claims can be combined to be implemented or performed in the method.

Claims (24)

1. A decoding device for decoding an image, the decoding device comprising: memory; And at least one processor coupled to the memory, wherein the at least one processor is configured to: obtaining image information including quantized palette mode transition value information from the bit stream; deriving a transition value for the current block based on the quantized transition value information; And generating reconstructed samples based on the transition value, wherein the transition value is output based on the information of the quantized transition value and the quantization parameter, wherein the quantization parameter is derived based on the minimum quantization parameter information for the transform skip mode, wherein the minimum quantization parameter information for the transform skip mode is a syntactic element obtained from a sequence parameter set (SPS) included in the image information, wherein the quantization parameter is output as a value greater than or equal to the minimum quantization parameter value derived from the minimum quantization parameter information for the skip conversion mode. 2. An encoding device for encoding an image, the encoding device comprising: memory; And at least one processor coupled to the memory, wherein the at least one processor is configured to: displaying the transition value in palette mode for the current block; deriving a quantized transition value based on the transition value; And encoding image information including quantized transition value information, wherein the quantized transition value is derived based on the quantization parameter for the transition value in the current block, wherein the quantization parameter is derived based on the minimum quantization parameter information for the transform skip mode, wherein the minimum quantization parameter information for the transform skip mode is a syntax element included in a sequence parameter set (SPS), wherein the SPS is included in the image information, and wherein the quantization parameter is output as a value greater than or equal to the minimum quantization parameter value derived from the minimum quantization parameter information for the skip conversion mode. 3. A device for transmitting image data, the device comprising: at least one processor configured to obtain a bitstream, wherein the bitstream is generated based on obtaining a palette mode transition value for the current block, deriving a quantized transition value based on the transition value, and encoding image information including the quantized transition value information , to generate a bit stream; And a transmitter configured to transmit data containing a bit stream, wherein the quantized transition value is derived based on the quantization parameter for the transition value in the current block, wherein the quantization parameter is derived based on the minimum quantization parameter information for the transform skip mode, wherein the minimum quantization parameter information for the transform skip mode is a syntax element included in a sequence parameter set (SPS), wherein the SPS is included in the image information, and wherein the quantization parameter is output as a value greater than or equal to the minimum quantization parameter value derived from the minimum quantization parameter information for the skip conversion mode.

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