A video decoding method and apparatus and a video encoding method and apparatus based on a scanning order of hierarchical data units are provided. The decoding method includes: receiving and parsing a bitstream of an encoded video; extracting from the bitstream information about a size of a maximum coding unit for decoding a picture of the encoded video, and encoding information about a coded depth and an encoding mode for coding units of the picture, wherein the size of the maximum coding unit is a maximum size of a coding unit which is a data unit for decoding the picture; and determining a hierarchical structure of the maximum coding unit and the coding units into which the picture is divided according to depths, and decoding the picture based on the coding units, by using the information about the size of the maximum coding unit and the encoding information about the coded depth and the encoded mode.

An image decoding method of decoding, on a block-by-block basis, image data included in a coded stream includes: deriving candidates for an intra prediction mode to be used for intra prediction for a decoding target block, the number of the candidates constantly being a plural number; obtaining, from the coded stream, an index for identifying one of the derived candidates for the intra prediction mode; and determining, based on the obtained index, one of the derived candidates for the intra prediction mode as the intra prediction mode to be used for intra prediction for the decoding target block.

There is disclosed an apparatus, a method and a computer program for video coding. The apparatus comprises a selector configured for selecting a pixel for prediction; a projection definer configured for determining a projection of said pixel to a set of reference pixels; and a prediction definer configured for selecting one or more reference pixels from said set of reference pixels on the basis of said projection, and using said selected one or more reference pixels to obtain a prediction value for said pixel to be predicted.

Devices, systems and methods for digital video coding, which includes Prediction from Multiple Cross-components (PMC) methods, are described. An exemplary method for video processing includes making a first determination that a cross-component prediction (CCP) mode is disabled for a conversion between a video block of a video and a bitstream representation of the video and making a second determination, based on the first determination, regarding whether a first syntax element indicating usage of an enhanced Two-Step Cross-component Prediction Mode (TSCPM) coding tool or an enhanced cross-component linear model (CCLM) coding tool is included in the bitstream representation. The method also includes performing a conversion based on the second determination

An image decoding method performed by a decoding apparatus according to the present disclosure comprises the steps of: obtaining a reference sample line index of a current block and most probable mode (MPM)-related information; constructing an alternative MPM list on the basis of the reference sample line index; deriving an intra prediction mode of the current block on the basis of the alternative MPM list and the MPM-related information; and generating a predicted block of the current block on the basis of the intra prediction mode, wherein the alternative MPM list is constructed on the basis of an intra prediction mode of an upper adjacent block of the current block and an intra prediction mode of a left adjacent block of the current block.

Techniques for selecting a coding mode for an image coding process are described. Coding modes can be selected through a coding mode transition state machine, a re-quantization process, selection of an optimal transform size, by skipping some quantization parameters, or by performing motion search.

A method is provided for coding at least one image split up into partitions, a current partition to be coded containing data, at least one data item of which is allotted a sign. The coding method includes, for the current partition, the following steps: calculating the value of a function representative of the data of the current partition with the exclusion of the sign; comparing the calculated value with a predetermined value of the sign; as a function of the result of the comparison, modifying or not modifying at least one of the data items of the current partition, in the case of modification, coding the at least one modified data item.

Quantization matrix can be used to adjust quantization of transform coefficients at different frequencies. In one embodiment, a single fixed parametric model, such as a polynomial is used to represent a quantization matrix. Modulation of bit cost and complexity is achieved by specifying only the n first polynomial coefficients, the remaining ones being implicitly set to zero or other default values. One form of the single fixed polynomial is a fully developed polynomial in (x, y), where x, y indicate the coordinates of a given coefficient in a quantization matrix, with terms ordered by increasing exponent. Since higher exponents are the last ones, reducing the number of polynomial coefficients reduces the degree of the polynomial, hence its complexity. The polynomial coefficients can be symmetrical in x and y, and thus reducing the number of polynomial coefficients that need to be signaled in the bitstream.

Methods and apparatus for coding video information having a plurality of video samples are disclosed. Blocks for video data are coded by an encoder based upon a quantization parameter (QP) for each block. The QP used for each block may be limited by a maximum QP value. A buffer fullness of a buffer unit may be determined that indicates of a ratio between a number of bits currently occupied in the buffer unit and a current capacity of the buffer unit. The encoder may determine an adjustment value for the maximum QP based upon the determined buffer fullness. By dynamically adjusting the maximum QP for coding blocks of video data, distortion from quantization may be reduced while preventing the buffer unit from overflowing or emptying.

The disclosed invention is a enhancement to the Video Encoder component of the MPEG standard to improve both the efficiency and quality of the video presentation at the display device. The inventions described below pertain to the enhancement of video compression technology. In general, they are compatible with MPEG video standards (as in current art), but represent novel enhancements thereof. The above inventions apply to several transmission media and networks including cable, DSL, wireless, satellite and IP networks. Another category of invention in this disclosure enhances networking performance by recognizing that the transmitted information is video, rather than data. This invention can be scaled to other classes of multimedia data such as speech or audio or images.