A method of encoding an image into a coded image, the method comprising: writing a quantization offset parameter into the coded image, determining a prediction mode type for coding a block of image samples of the image into a coding unit of the coded image, determining a quantization parameter for the block of image samples, and determining if the prediction mode type is of a predetermined type, wherein if the prediction mode type is of the predetermined type, the method further comprises: modifying the determined quantization parameter using the quantization offset parameter, and performing a quantization process for the block of image samples using the modified quantization parameter, and wherein if the prediction mode type is not of the predetermined type, the method further comprises: performing a quantization process for the block of image samples using the determined quantization parameter.

A method of encoding an image into a coded image, the method comprising: writing a quantization offset parameter into the coded image, determining a prediction mode type for coding a block of image samples of the image into a coding unit of the coded image, determining a quantization parameter for the block of image samples, and determining if the prediction mode type is of a predetermined type, wherein if the prediction mode type is of the predetermined type, the method further comprises: modifying the determined quantization parameter using the quantization offset parameter, and performing a quantization process for the block of image samples using the modified quantization parameter, and wherein if the prediction mode type is not of the predetermined type, the method further comprises: performing a quantization process for the block of image samples using the determined quantization parameter.

Disclosed are an apparatus and a method of encoding/decoding a video, particularly a method and an apparatus for storing a quantization parameter differential value in a largest coding unit (LCU) based on quadtree splitting and adaptively predicting a quantization parameter value based on context information on neighboring CUs. Quadtree-based quantization parameter encoding and decoding methods and apparatuses effectively show information on a block having a quantization parameter differential value based on splitting information on a CU and adaptively predict a quantization parameter value using context information including a block size, block partition and a quantization parameter of a neighboring CU.

Disclosed are an apparatus and a method of encoding/decoding a video, particularly a method and an apparatus for storing a quantization parameter differential value in a largest coding unit (LCU) based on quadtree splitting and adaptively predicting a quantization parameter value based on context information on neighboring CUs. Quadtree-based quantization parameter encoding and decoding methods and apparatuses effectively show information on a block having a quantization parameter differential value based on splitting information on a CU and adaptively predict a quantization parameter value using context information including a block size, block partition and a quantization parameter of a neighboring CU.

A video decoding method includes: performing entropy decoding processing on an encoding block of a video image frame to obtain a quantized coefficient block of residual data corresponding to the encoding block; calculating quantization coefficients in the quantized coefficient block to obtain an implicitly derived index value; determining a transformation mode of the encoding block according to the implicitly derived index value and a value of an index identifier included in the encoding block; and performing inverse transformation processing on an inverse quantization result of the quantized coefficient block based on the transformation mode of the encoding block.

A video decoding method includes: performing entropy decoding processing on an encoding block of a video image frame to obtain a quantized coefficient block of residual data corresponding to the encoding block; calculating quantization coefficients in the quantized coefficient block to obtain an implicitly derived index value; determining a transformation mode of the encoding block according to the implicitly derived index value and a value of an index identifier included in the encoding block; and performing inverse transformation processing on an inverse quantization result of the quantized coefficient block based on the transformation mode of the encoding block.

In a video bitstream, Cb and Cr channels are demultiplexed before dequantization instead of after inverse transformation. In this way, regular Cb and Cr quantization control parameters can be used, optionally with minor adjustments when a video block is joint-chroma coded. In one embodiment, some specific quantization control parameters canbe specified. In another embodiment, separate Cb and Cr offsets can be specified for joint chroma coded blocks. In another embodiment, quantization control parameters specific to joint chroma coded blocks can be used for both Cb and Cr channels instead of nominal chroma quantization parameters.

Different quantization matrices may be transmitted corresponding to different block sizes, color components and prediction modes. To more efficiently signal the coefficients of the quantization matrices, in one implementation, a unified matrix identifier matrixId is used, based on a size identifier (sizeId) that relates to CU size with larger sizes listed first, and a matrix type (matrixTypeId) with luma QMs listed first. For example, the unified identifier is derived as: matrixId=N*sizeId+matrixTypeId, where N is the number of possible type identifiers, e.g., N=6. This single identifier allows referring to any previously transmitted matrix when using prediction (copy), and transmitting larger matrices first avoids interpolation in the prediction process. When a block uses the Intra Block Copy prediction mode, QM identifier may be derived as if the block uses the INTER prediction mode.

Different quantization matrices may be transmitted corresponding to different block sizes, color components and prediction modes. To more efficiently signal the coefficients of the quantization matrices, in one implementation, a unified matrix identifier matrixId is used, based on a size identifier (sizeId) that relates to CU size with larger sizes listed first, and a matrix type (matrixTypeId) with luma QMs listed first. For example, the unified identifier is derived as: matrixId=N*sizeId+matrixTypeId, where N is the number of possible type identifiers, e.g., N=6. This single identifier allows referring to any previously transmitted matrix when using prediction (copy), and transmitting larger matrices first avoids interpolation in the prediction process. When a block uses the Intra Block Copy prediction mode, QM identifier may be derived as if the block uses the INTER prediction mode.

A point cloud encoding method, including: obtaining attribute information about the attributes of a current point in a point cloud; processing the attribute information of the current point to obtain a residual value of the attribute information of the current point; using a target quantization manner, quantizing the residual value of the attribute information of the current point to obtain a quantized residual value of the attribute information of the current point; the target quantization manner comprises at least two of the following quantization manners: a first quantization manner, a second quantization manner, and a third quantization manner.