Fraunhofer-Gesellschaft Zur Foerderung Der Angewandten Forschung E.V.

Phan Hoang Tung Nguyen

Thomas Wiegand

Detlev Marpe

Heiko Schwarz

Benjamin Bross

Heiner Kirchhoffer

Paul Haase

Christian Rudat

Mischa Siekmann

Paul Keydel

Christian Helmrich

Adam Wieckowski

Valeri George

Gerhard Tech

Tobias Hinz

Jonathan Pfaff

Santiago De Luxán Hernández

Michael Schäfer

Soenke Schmidt

Jennifer Rasch

An apparatus for decoding a picture is configured to partition the picture into coding blocks, using recursive multi-tree splitting. Splitting schemes for the multi-tree splitting are described. According to an embodiment, the decoder decodes a split direction flag from a data stream by context adaptive entropy decoding using a context which depends on whether, and discriminates between, a first number of criteria which would be fulfilled in case of a split direction indicated by the split direction flag being horizontal equals a second number of criteria which would be fulfilled in case of the split direction indicated by the split direction flag being vertical, the first number being greater than the second number, and the first number being smaller than the second number.

Encoding and decoding a picture

A picture in a data stream is subdivided into different size transform bocks. For a transform block, a transformation is selected by checking whether the block's size exceeds a threshold. If it does, a default technique is used to select the transformation. If it does not, a transformation is used from a list of transformations as identified by an index, the list including an identity transformation and non-identity transformations. A coefficients block in the data stream is decoded, and if the selected transformation is the identity transformation, then the coefficients block is used as a residual sample array, and if the selected transformation is not the identity transformation, the coefficients block is subjected to an inverse transformation corresponding to the selected transformation to obtain a residual sample array used to correct a prediction for the transform block.

Unified transform type signaling and transform type dependent transform coefficient level coding

Concepts for transform coefficient block coding are described which enable coding of coefficients of a transform block in a manner suitable for dependent quantization and effectively implementable by entropy coding in terms of coding efficiency.

Entropy coding of transform coefficients suitable for dependent scalar quantization

A video decoder employs context-adaptive binary arithmetic coding for decoding a video from a data stream. The video decoder determines a parametrization for the context-adaptive binary arithmetic coding.

Determining a parametrization for context-adaptive binary arithmetic coding

Concepts are presented which achieve a more efficient coding of coefficients of a transform block by use of dependent quantization and context adaptive entropy coding or achieve a coding of coefficients of a transform block in a manner which allows a more efficient coding even if a usage of dependent quantization is combined with the usage of context adaptive entropy coding.

Efficient coding of transform coefficients using or suitable for a combination with dependent scalar quantization

The coding of a media signal is rendered more efficient by describing the media signal using a sequence of samples and sequentially encoding this sequence by selecting, for a current sample, a set of quantization levels out of a plurality of quantization level sets depending on indices encoded into the data stream for previous samples of the sequence of samples, quantizing the current sample onto one level of the set of quantization levels, and encoding a quantization index to the one level for the current sample into the data stream. In other words, scalar quantization of the individual samples of the sequence of samples is used, but it is rendered dependent on quantization indices encoded into the data stream for previous samples of the sequence of samples. By this measure, it is possible to 'construe' a grid of quantization points in the multi-dimensional space across which all possible settings of the sequence of samples are spread, onto which values of the samples are quantized according to the sequence of quantization indices coded into the data stream. This grid, in turn, reduces, statistically, a mean quantization error.

Dependent quantization

A video encoder is configured to entropy encode an absolute value of a quantization level of a current transform coefficient at position (xC, yC), wherein the absolute value is encoded using context adaptive binary arithmetic encoding of bins of a first binarization. The video coder is further configured, for the current transform coefficient, to encode a bin of the first binarization by using a context which is determined based on a sum of minimum absolute values of transform coefficient quantization levels, based on encoded bins of the first binarization, at one or more transform coefficient positions among (xC+1, yC), (xC+2, yC), (xC+1, yC+1), (xC, yC+1), and (xC, yC+2).

Transform coefficient block coding

Decoder for decoding a residual signal from a data stream, configured to decode, from the data stream, a quantized prediction residual and at least one quantization error compensation signal; scale the quantized prediction residual to determine a scaled prediction residual; determine a reconstructed prediction residual based on the scaled prediction residual and the at least one quantization error compensation signal.

Multiple stage residual coding in modern hybrid image and video coding solutions

The refinement of block-based predictive coding and decoding of pictures as applicable in, e.g., hybrid video codecs, using additional reconstructed samples or residuals is described. An apparatus for block-based predictive decoding of a picture is described. The apparatus includes a combiner configured to combine a residual signal a predetermined block of the picture and a reference signal for the predetermined block so as to obtain a first spectrum, the residual signal correcting a prediction error of a prediction of the predetermined block of the picture; a reducer configured to perform thresholding on the first spectrum to obtain a second spectrum so that coefficients below a threshold value are set to a predefined value; an extractor configured to obtain from the second spectrum a modified version of the residual signal; and a reconstructor block configured to decode the predetermined block of the picture from the data stream on the basis of the modified version of the residual signal.

Refined block-based predictive coding and decoding of a picture

A decoder configured to decode residual levels, and sequentially dequantize the residual levels by selecting a quantizer out of a set of default quantizers depending on a current transition state, and updating the current transition state depending on a current residual level's characteristic obtained by an application of a binary function onto the current residual level, and depending on a quantization mode information contained in the data stream. The current transition state transitions, according to a surjective mapping which depends on the quantization mode information, from a domain of combinations of a set of one or more transition states with the current residual level's characteristic onto the set of one or more transition states, wherein a cardinality of the set of one or more transition states differs depending on the quantization mode information.

Decoder, encoder and method for supporting adaptive dependent quantization of transform coefficient levels

Arithmetic encoder for encoding a plurality of symbols is configured to derive an interval size information for an arithmetic encoding of one or more symbol values to be encoded on the basis of one or more state variable value, in a first mode of operation, and to update the one or more state variable values and/or the interval size information for an encoding of one or more subsequent symbol values to be encoded in the first mode; in a second mode, the arithmetic encoder is configured to disable an update of the one or more state variable values and/or of the interval size information. Additionally, further embodiments of arithmetic encoders and decoders and video encoders and decoders are described.

Arithmetic encoders and decoders, video encoders and decoders, methods for encoding or decoding symbols, and methods for encoding or decoding video content

Decoder for block-based decoding of a picture from a data stream, configured to decode an intra-coding mode for a predetermined block of the picture from the data stream, configured to decode a partition dimension flag for the predetermined block of the picture from the data stream and set a partition dimension depending on the partition dimension flag to be horizontal or vertical and the decoder is configured to partition, along the predetermined dimension, the predetermined block into transform partitions which are as wide as the predetermined block perpendicular to predetermined dimension, furthermore configured to decode, for each transform partition, a transform of a prediction residual from the data stream; intra-predicting the predetermined block depending on one or more already reconstructed samples neighboring the predetermined block in a manner depending on the intra-coding mode to obtain a predictor for the predetermined block; and reconstructing the predetermined block by correcting the predictor within each transform partition using the transform of the prediction residual decoded for the respective transform partition.

Implementation efficient partition-based intra coding concept

An apparatus for decoding a picture is configured to partition the picture into coding blocks, using recursive multi-tree splitting. Splitting schemes for the multi-tree splitting are described. According to an embodiment, the decoder decodes a split direction flag from a data stream by context adaptive entropy decoding using a context which depends on whether, and discriminates be-tween, a first number of criteria which would be fulfilled in case of a split direction indicated by the split direction flag being horizontal equals a second number of criteria which would be fulfilled in case of the split direction indicated by the split direction flag being vertical, the first number being greater than the second number, and the first number being smaller than the second number.

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Berlin, Germany

Phan Hoang Tung Nguyen