11 results about "Ac coefficient" patented technology

The embodiment of the application provides a transform coefficient coding method, a transform coefficient decoding method and a terminal, and belongs to the technical field of coding and decoding. The transform coefficient coding method comprises the following steps: obtaining transform coefficients corresponding to a point cloud; the transform coefficients comprise a direct current (DC) coefficient and at least two alternating current (AC) coefficients; encoding the DC coefficient according to a first order corresponding to the DC coefficient and a context probability model corresponding to the DC coefficient; encoding each AC coefficient according to a second order corresponding to each AC coefficient and a context probability model corresponding to each AC coefficient; the second order is determined based on the first order and an index of a coding point corresponding to the AC coefficient; and generating a target code stream based on the encoding result of the DC coefficient and the encoding result of each AC coefficient.

Embodiments of the present application provide a point cloud encoding method, a point cloud decoding method, an encoder, a decoder, and a storage medium. The point cloud decoding method comprises: parsing a code stream, and determining a residual value of an AC coefficient of a current transform block, wherein the current transform block belongs to a first RAHT layer, and the first RAHT layer is any one of a plurality of RAHT layers of a point cloud of a current frame; determining a reconstructed value of the AC coefficient of the current transform block on the basis of the residual value of the AC coefficient of the current transform block; determining a reconstructed attribute value of the current transform block on the basis of the reconstructed value of the AC coefficient of the current transform block; determining whether to perform a filtering operation on the first RAHT layer; and if it is determined to perform the filtering operation on the first RAHT layer, filtering the reconstructed attribute value of the current transform block on the basis of a first group of filtering coefficients.

Provided in the embodiments of the present application are a point cloud encoding method, a point cloud decoding method, an encoder, a decoder, and a storage medium. The point cloud decoding method comprises: parsing a bitstream to determine residual values of AC coefficients of one or more transform blocks in a current RAHT layer, wherein the current RAHT layer is any one of a plurality of RAHT layers of a current frame; on the basis of the residual values of the AC coefficients of the one or more transform blocks, determining reconstructed values of the AC coefficients of the one or more transform blocks; on the basis of the reconstructed values of the AC coefficients of the one or more transform blocks, determining reconstructed attribute values of the one or more transform blocks; determining whether to adjust the reconstructed attribute values in the current RAHT layer; and if it is determined to adjust the reconstructed attribute values in the current RAHT layer, adjusting the reconstructed attribute values of the one or more transform blocks on the basis of a target offset value.

The present invention provides a JPEG reversible data hiding method based on chaos theory and histogram shifting. First, a pseudo-random sequence is generated based on a JPEG image using a chaotic system. Then, the JPEG image is entropy decoded to obtain quantized discrete cosine transform (DCT) coefficients, resulting in a DCT coefficient block. All DCT coefficient blocks are scrambled using a pseudo-random sequence x for data embedding, thereby enhancing the concealment and security of data embedding. The present invention does not modify the zero AC coefficients in the quantization block, but only expands the AC coefficients with an absolute value of 1 to carry secret information. Furthermore, a new coefficient block selection strategy is proposed, in which, during the information embedding process, the embedding coefficient block is selected based on the ratio R of the number of AC coefficients with a value of 1 to the number of other non-zero AC coefficients. This method effectively preserves the visual quality and storage size of the image, and has a high embedding capacity, which depends solely on the number of AC coefficients with an absolute value of 1 in the DCT coefficient block.

The application discloses a JPEG image encryption method based on coefficient grouping encryption, which comprises the following steps: obtaining original DC coefficient difference entropy coding and AC coefficient entropy coding of all blocks; predicting the DC coefficient to obtain a DC prediction error value; obtaining and using an initial key to group and scramble and encrypt AC coefficients containing complete AC coefficient entropy coding; extracting image features; obtaining and using an adaptive key related to image content to scramble and encrypt blocks without DC coefficients to obtain encrypted AC coefficients; using a quantization table of a to-be-encrypted JPEG image and the adaptive key to normalize and encrypt the DC prediction error value through modulo operation to obtain encrypted DC coefficients; and performing entropy coding on the encrypted DC coefficients and AC coefficients to obtain an encrypted image. The application improves the generality of encryption and decryption, and improves the change rate of NCC, EAC and PLZ features by scrambling and encrypting different types of AC coefficient groups.

The invention discloses a video watermark extraction method and device based on a quick response code, equipment and a medium, and relates to the technical field of image processing, and the method comprises the steps: obtaining a first scene change frame and a quick response code matrix of a first video, and carrying out the processing of the first scene change frame and the quick response code matrix, and obtaining an encrypted quick response code matrix and a plurality of size image blocks; performing discrete cosine transform on the brightness component of the first scene change frame, and combining the encrypted quick response code matrix to obtain a DC coefficient and an AC coefficient; inverse discrete cosine transform is carried out on the image blocks with the multiple sizes, embedding of watermark information is achieved, and a first video with a watermark is obtained; processing the first video with the watermark to obtain a target estimation value of the encrypted quick response code matrix; and decrypting and decoding the target estimation value in sequence to obtain target watermark information, thereby realizing extraction of the watermark information. According to the method, the size of the embedded watermark can be dynamically adjusted, the extraction efficiency is improved, and the safety of the watermark can also be improved.

The embodiment of the application provides a transform coefficient coding method, a transform coefficient decoding method and a terminal, and belongs to the technical field of coding and decoding. The transform coefficient coding method comprises the following steps: determining a first columbus order corresponding to a DC coefficient according to an amplitude corresponding to the DC coefficient in transform coefficients; in the case that the transform coefficients comprise the DC coefficient, generating a target code stream according to the first columbus order corresponding to the DC coefficient and a coding result of the DC coefficient; or in the case that the transform coefficients comprise the DC coefficient and AC coefficients, performing at least one of the following operations: generating the target code stream based on the first columbus order corresponding to the DC coefficient, the coding result of the DC coefficient and a coding result of each AC coefficient; or determining a second columbus order corresponding to the AC coefficient according to the first columbus order and an amplitude corresponding to the first AC coefficient; and generating the target code stream based on the first columbus order corresponding to the DC coefficient, the coding result of the DC coefficient and the coding result of each AC coefficient.

Embodiments of the present application provide a point cloud encoding method, a point cloud decoding method, an encoder, a decoder, and a storage medium. The point cloud decoding method comprises: parsing a code stream, and determining a residual value of an AC coefficient of a current transform block, wherein the current transform block belongs to a first RAHT layer, and the first RAHT layer is any one of a plurality of RAHT layers of a point cloud of a current frame; determining a reconstructed value of the AC coefficient of the current transform block on the basis of the residual value of the AC coefficient of the current transform block; determining a reconstructed attribute value of the current transform block on the basis of the reconstructed value of the AC coefficient of the current transform block; determining whether to perform a filtering operation on the first RAHT layer; and if it is determined to perform the filtering operation on the first RAHT layer, filtering the reconstructed attribute value of the current transform block on the basis of a first group of filtering coefficients.

The invention discloses an image steganography method and device based on a pseudo-random generator. The method comprises the following steps: acquiring a carrier image, converting the carrier image into a YCrCb color space and extracting a brightness channel to obtain a brightness matrix, and performing 8 * 8 partitioning on the brightness matrix to generate a pixel block matrix; generating a pseudo-random sequence based on the date vector and the task number through a pseudo-random generator, and determining an embedded block sequence list; embedded blocks in the pixel block matrix are determined according to the embedded block sequence list, 2D-DCT conversion and quantization are carried out on the embedded blocks, then Z-shaped scanning is carried out, a 1 * N frequency domain coefficient vector matrix is obtained, the first vector of the frequency domain coefficient vector matrix is a DC coefficient, and the rest are AC coefficients; sequentially splicing the data to be steganographic into an embedded information bit string, and embedding the embedded information bit string into the AC coefficient of the frequency domain coefficient vector; and performing inverse Z-shaped scanning, inverse quantization and 2D-IDCT transformation on the frequency domain coefficient vector matrix of the embedded data to reconstruct a secret-carrying image. According to the scheme, the security of image steganography can be improved.

The embodiment of the present application provides a transform coefficient encoding method, a transform coefficient decoding method and a terminal, which belong to the field of coding and decoding technology. The above-mentioned transform coefficient encoding method includes: obtaining the transform coefficient corresponding to the point cloud; the transform coefficient includes a direct current (DC) coefficient and at least two alternating current (AC) coefficients; encoding the DC coefficient according to the first order corresponding to the DC coefficient and the context probability model corresponding to each component of the DC coefficient; encoding each AC coefficient according to the second order corresponding to each AC coefficient and the context probability model corresponding to each component of each AC coefficient; the second order is determined based on the first order and the level corresponding to the transform coefficient; based on the encoding result of the DC coefficient and the encoding result of each AC coefficient, generating a target code stream.

To improve efficiency of decoding attribute information.SOLUTION: In a point cloud decoding device 200 of the present invention, an RAHT unit 2080 is configured to perform scaling on intra-predicted attribute values or AC coefficients obtained by applying RAHT to the attribute values in decoding processing of the attribute values using RAHT.SELECTED DRAWING: Figure 2