British Broadcasting Corporation

Marta Mrak

Saverio Blasi

Matteo Naccari

David Flynn

Ebroul Izquierdo

Andrea Gabriellini

Nikola Sprljan

Thomas Davies

Shenglan Huang

Andre Seixas Dias

Andrea Gabrieliini

Marc Gorriz Blanch

Saverio Giovanni Blasi

An intra-prediction mode is provided for chroma data, in which a neural network implemented attention module directs the encoding of a block of chroma data with respect to luma data for the collocated luma block.

Chroma intra prediction in video coding and decoding

The present invention relates to a method of decoding a video bitstream, the method comprising the steps of: receiving a bitstream representing: residual samples produced by subtracting encoder filtered motion compensated prediction samples from image samples; and motion vectors used in forming the motion compensated prediction samples; the encoder filtering process conducted on the motion compensated prediction samples at an encoder having at least one parameter; using said motion vectors to provide motion compensated prediction samples from a previously reconstructed image; decoder filtering said motion compensated prediction samples in accordance with said at least one parameter; and adding said filtered motion compensated prediction samples to said residual samples to reconstruct images. A system and apparatus corresponding to this method are also disclosed.

Video encoding and decoding

An efficient high quality video coding and decoding technique is described. A prediction block is generated that contains modified coefficients. The modified coefficients improve the efficiency of the compression process once the prediction block is subtracted from the original block to generate a residual signal for quantisation and encoding. A similar process operates at the decoder side. The processes may operate in both the frequency and the spatial domain.

Adaptive prediction of coefficients of a video block

A method of encoding image or video content within a set of targets such as a time, a complexity, quality, and bitrate, using an encoder having a plurality of coding configurations, comprises setting an initial coding configuration in the encoder, where coding configurations differ one from the other in the number of options tested for each of one or more tools. A first part of the content is encoded in the initial configuration and measures are made of the number of times a specified tool is used and a representative time taken to test an option for that specified tool. From those measures a prediction is made of the time difference between the time taken to encode content using the initial coding configuration and the time taken to encode content using another coding configuration in which a different number of options are tested for that specified tool.

Image or video encoding and decoding

In video coding or decoding, coding blocks in a current frame are predicted from blocks in previously encoded frames with prediction samples and associated information organised in a prediction unit. A decision on which prediction unit type to consider for coding is made upon analysis of the distribution of a sum of absolute difference or other function of the residual signal over the block.

Video encoding and decoding with selection of prediction units

In video coding, where differences between input picture values and picture prediction values are transformed in a block based transform, the differences are formed in a series of parallel steps. A first step conducted in parallel upon a first subset of pixels uses prediction values based wholly on previously processed blocks. This first subset can include anchor pixels which are not contiguous with any previously processed block. A second step conducted in parallel upon a second subset includes pixels which are predicted from pixels of the first subset.

Compression of pictures

A video decoder has a transform mode and a transform skip mode and in the transform skip mode a residual prediction mode is selected. A compressed bit-stream is entropy-decoded to obtain a block of quantised values. An inverse quantiser operates in the transform mode to form transform coefficients and in the transform skip mode to form differential residual values. In the transform mode an inverse transform is performed to form residual values. In the transform skip mode residual prediction is used perform residual prediction using high accuracy locally decoded residual value. The residual value is then down-scaled to obtain the reconstructed residual. A block predictor is formed from decoded image values at the same precision at which video samples are stored in the frame memory.

Video encoding and decoding with prediction at higher precision

In the encoding of video data, a list of references pictures is constructed to be used in decoding. Prediction (direction) modes are defined by n-tuples (x, x, . . . , x), where xspecifies prediction option of the m-th component of the motion vector field, m=0, . . . , M-1, where M components to the motion fields exist; where a coding option xis an element from a set composed of all defined combinations of motion prediction modes and reference picture indices, with the addition of an option '/', x&#x3b5;{'/', 0, 1, . . . , r&#x2212;1}; where option &#x201c;/&#x201d; specifies that the component is not used, and other options 0, 1, . . . , r&#x2212;1 specify one of rcombinations. A subset of all possible n-tuples is provided and a prediction mode used for predicting an inter-coded block is defined by reference to that subset.

Video encoding and decoding using reference pictures

Video encoding or decoding utilizing a spatial transform operating on rows and columns of a block, with a set of transform skip modes including: transform on rows and columns; transform on rows only; transform on columns only; no transform. An indication of the selected mode is provided to the decoder. Coefficients are scaled by a factor dependent upon the norm of the transform vector of the skipped transform to bring the untransformed image values to the same level as transformed coefficients.

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London, United Kingdom

Marta Mrak