A decoder includes an entropy decoder configured to derive a number of bins of the binarizations from the data stream using binary entropy decoding by selecting a context among different contexts and updating probability states associated with the different contexts, dependent on previously decoded portions of the data stream; a desymbolizer configured to debinarize the binarizations of the syntax elements to obtain integer values of the syntax elements; a reconstructor configured to reconstruct the video based on the integer values of the syntax elements using a quantization parameter, wherein the entropy decoder is configured to distinguish between 126 probability states and to initialize the probability states associated with the different contexts according to a linear equation of the quantization parameter, wherein the entropy decoder is configured to, for each of the different contexts, derive a slope and an offset of the linear equation from first and second four bit parts of a respective 8 bit initialization value.

Context initialization in entropy coding

Techniques coding video data, including a mode for intra prediction of blocks of video data from predictive blocks of video data within the same picture, may include determining a predictive block of video data for the current block of video data, wherein the predictive block of video data is a reconstructed block of video data within the same picture as the current block of video data. A two-dimensional vector, which may be used by a video coder to identify the predictive block of video data, includes a horizontal displacement component and a vertical displacement component relative to the current block of video data. The mode for intra prediction of blocks of video data from predictive blocks of video data within the same picture may be referred to as Intra Block Copy or Intra Motion Compensation.

Intra prediction from a predictive block

A decoder for decoding a data stream into which media data is coded has a mode switch configured to activate a low-complexity mode or a high-efficiency mode depending on the data stream, an entropy decoding engine configured to retrieve each symbol of a sequence of symbols by entropy decoding using a selected one of a plurality of entropy decoding schemes, a desymbolizer configured to desymbolize the sequence of symbols to obtain a sequence of syntax elements, a reconstructor configured to reconstruct the media data based on the sequence of syntax elements, selection depending on the activated low-complexity mode or the high-efficiency mode. In another aspect, a desymbolizer is configured to perform desymbolization such that the control parameter varies in accordance with the data stream at a first rate in case of the high-efficiency mode being activated and the control parameter is constant irrespective of the data stream or changes depending on the data stream, but at a second lower rate in case of the low-complexity mode being activated.

Entropy coding supporting mode switching

An entropy decoder is configured to, for horizontal and vertical components of motion vector differences, derive a truncated unary code from the data stream using context-adaptive binary entropy decoding with exactly one context per bin position of the truncated unary code, which is common for horizontal and vertical components of the motion vector differences, and an Exp-Golomb code using a constant equi-probability bypass mode to obtain the binarizations of the motion vector differences. A desymbolizer is configured to debinarize the binarizations of the motion vector difference syntax elements to obtain integer values of the horizontal and vertical components of the motion vector differences. A reconstructor is configured to reconstruct a video based on the integer values of the horizontal and vertical components of the motion vector differences.

Entropy coding of motion vector differences

An apparatus encodes a binary shape signal by using a zig-zag scanning technique. The apparatus zig-zag scans the binary shape signal to thereby output each of the pixels in the binary shape signal sequentially in order of scanning. Then, a context corresponding to each of the pixels is selected from pixels processed prior to said each of the pixels by taking the scanning order into account. By using the context of said each of the pixels, the apparatus ciphers a context number corresponding to said each of the pixels and detects its probability based on the corresponding context number. Through the above procedure, if the probabilities for all of the pixels in the binary shape signal are detected, the apparatus arithmetically encodes the binary shape signal by using the detected probabilities to thereby produce the encoded binary shape signal.

Method and apparatus for encoding a binary shape signal

In a method for encoding a binary alpha block (BAB) within a current frame based on the current frame and a previous frame, even-numbered horizontal lines of the BAB are sampled to generate a first block and even-numbered vertical lines of the first block are sampled to generate a first sample block. And then, a reconstructed first block and a reconstructed BAB are generated by inserting reconstructed vertical and horizontal lines sequentially at locations of odd-numbered vertical and horizontal lines thereof, respectively. In the above, binary values of first and second binary pixels of the reconstructed vertical and horizontal lines are made by using corresponding first and second context values based on predetermined probability tables, respectively, wherein the corresponding first and second context values are calculated by using the context values of binary pixels within the previous frame located at identical positions to the first and second binary pixels, respectively; and context values of binary pixels located at surrounding positions of the first and the second binary pixels except a binary pixel below the first binary pixel and a binary pixel right to the second binary pixel, respectively.

Seok-Won Daewoo Electronics Co. Ltd. Han

Papers

Method for restoring a binary shape signal