A method for encoding a picture of a video sequence in a bit stream that constrains slice header processing overhead is provided. The method includes computing a maximum slice rate for the video sequence, computing a maximum number of slices for the picture based on the maximum slice rate, and encoding the picture wherein a number of slices used to encode the picture is enforced to be no more than the maximum number of slices.

A picture in a data stream is subdivided into different size transform blocks. 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.

Disclosed is an image data encoding/decoding method and apparatus. A method for decoding a 360-degree image comprises the steps of: receiving a bitstream obtained by encoding a 360-degree image; generating a prediction image by making reference to syntax information obtained from the received bitstream; combining the generated prediction image with a residual image obtained by dequantizing and inverse-transforming the bitstream, so as to obtain a decoded image; and reconstructing the decoded image into a 360-degree image according to a projection format.

Disclosed is an image data encoding/decoding method and apparatus. A method for decoding a 360-degree image comprises the steps of: receiving a bitstream obtained by encoding a 360-degree image; generating a prediction image by making reference to syntax information obtained from the received bitstream; combining the generated prediction image with a residual image obtained by dequantizing and inverse-transforming the bitstream, so as to obtain a decoded image; and reconstructing the decoded image into a 360-degree image according to a projection format.

There are provided mechanisms for methods and apparatuses for transform selection in encoding and decoding of video blocks.

A method for intra prediction comprises determining a first MPM candidate corresponding to a left-side candidate block on the basis of a position of the left-side candidate block adjacent to a left side of a current block; determining a second MPM candidate corresponding to an upper-end candidate block on the basis of a position of the upper-end candidate block adjacent to an upper end of the current block; generating an MPM candidate list including a plurality of MPM candidates, on the basis of the first MPM candidate and the second MPM candidate; and determining one MPM candidate of the plurality of the MPM candidates that constitute the MPM candidate list as an intra prediction mode of the current block, and performing intra prediction for the current block on the basis of the determined intra prediction mode to generate a prediction block corresponding to the current block.

A method for intra prediction comprises determining a first MPM candidate corresponding to a left-side candidate block on the basis of a position of the left-side candidate block adjacent to a left side of a current block; determining a second MPM candidate corresponding to an upper-end candidate block on the basis of a position of the upper-end candidate block adjacent to an upper end of the current block; generating an MPM candidate list including a plurality of MPM candidates, on the basis of the first MPM candidate and the second MPM candidate; and determining one MPM candidate of the plurality of the MPM candidates that constitute the MPM candidate list as an intra prediction mode of the current block, and performing intra prediction for the current block on the basis of the determined intra prediction mode to generate a prediction block corresponding to the current block.

Methods are provided for inter-prediction candidate index coding independent of the construction of the corresponding inter-prediction candidate list, i.e., a merging candidate list or an advanced motion vector predictor list. A maximum allowed number of inter-prediction candidates for an inter-prediction candidate list is used for encoding the inter-prediction candidate index in an encoded bit stream. The maximum allowed number may be pre-determined or may be selected by the encoder and encoded in the bit stream. A decoder may then decode the index using the maximum allowed number of inter-prediction candidates independent of the construction of the corresponding inter-prediction candidate list.

A system and method of planar motion vector derivation which, in some embodiments can employ an unequal weighted combination of adjacent motion vectors. In some embodiments, motion vector information associated with a bottom right pixel or block adjacent to a current coding unit can be derived from motion information associated with a top row or top neighboring row of a current coding unit and motion information associated with a left column or left neighboring column of a current coding unit. Weighted or non-weighted combinations of such values can be combined in a planar mode prediction model to derive associated motion information for bottom and/or right adjacent pixels or blocks.

A system and method of planar motion vector derivation which, in some embodiments can employ an unequal weighted combination of adjacent motion vectors. In some embodiments, motion vector information associated with a bottom right pixel or block adjacent to a current coding unit can be derived from motion information associated with a top row or top neighboring row of a current coding unit and motion information associated with a left column or left neighboring column of a current coding unit. Weighted or non-weighted combinations of such values can be combined in a planar mode prediction model to derive associated motion information for bottom and/or right adjacent pixels or blocks.