A method for encoding a video sequence in a scalable video encoder to generate a scalable bitstream is provided that includes encoding the video sequence in a first layer encoder of the scalable video encoder to generate a first sub-bitstream, encoding the video sequence in a second layer encoder of the scalable video encoder to generate a second sub-bitstream, wherein portions of the video sequence being encoded in the second layer encoder are predicted using reference portions of the video sequence encoded in the first layer encoder, combining the first sub-bitstream and the second sub-bitstream to generate the scalable bitstream, and signaling in the scalable bitstream an indication of a maximum decoded picture buffer (DPB) size needed for decoding the second sub-bitstream and the first sub-bitstream when the second sub-bitstream is a target sub-bitstream for decoding.

An adaptive motion vector prediction unit configured to adaptively perform spatial prediction that performs prediction using a motion vector around a target block and temporal prediction that performs prediction using a motion vector of a collocated picture is included, and in the temporal prediction performed by the adaptive motion vector prediction unit, the collocated picture to be referred to is designated on a per picture basis, and a reference list is designated on a per slice basis.

A picture coding method includes: performing a first derivation process for deriving a first merging candidate which includes a candidate set of a prediction direction, a motion vector, and a reference picture index for use in coding of a current block;

performing a second derivation process for deriving a second merging candidate; selecting a merging candidate to be used in the coding of the current block from among the first and second merging candidates; and attaching an index for identifying the selected merging candidate to the bitstream; wherein the first derivation process is performed so that a total number of the first merging candidates does not exceed a predetermined number, and the second derivation process is performed when the total number of the first merging candidates is less than a predetermined maximum number of merging candidates.

A picture coding method includes: performing a first derivation process for deriving a first merging candidate which includes a candidate set of a prediction direction, a motion vector, and a reference picture index for use in coding of a current block;

performing a second derivation process for deriving a second merging candidate; selecting a merging candidate to be used in the coding of the current block from among the first and second merging candidates; and attaching an index for identifying the selected merging candidate to the bitstream; wherein the first derivation process is performed so that a total number of the first merging candidates does not exceed a predetermined number, and the second derivation process is performed when the total number of the first merging candidates is less than a predetermined maximum number of merging candidates.

A method for decoding a picture block is disclosed. The decoding method comprises: reconstructing reference picture from another reference picture of a decoder picture buffer of a first layer of a multi-layered stream and from data decoded from a second layer of said multi-layered stream and storing said reference picture in a decoder picture buffer of said second layer, wherein said reference picture is indicated as not to be displayed; decoding a flag indicating that a subsequently decoded picture of the second layer is not using any inter-layer prediction; and reconstructing a picture block of said subsequently decoded picture at least from said reference picture.

A method for decoding a picture block is disclosed. The decoding method comprises: reconstructing reference picture from another reference picture of a decoder picture buffer of a first layer of a multi-layered stream and from data decoded from a second layer of said multi-layered stream and storing said reference picture in a decoder picture buffer of said second layer, wherein said reference picture is indicated as not to be displayed; decoding a flag indicating that a subsequently decoded picture of the second layer is not using any inter-layer prediction; and reconstructing a picture block of said subsequently decoded picture at least from said reference picture.

The present disclosure relates to a method by which a decoding apparatus performs video coding, comprising the steps of: generating a motion information candidate list for a current block; selecting one candidate from among those included in the motion information candidate list; deriving control point motion vectors (CPMVs) of the current block based on the selected candidate; deriving sub-block-unit or sample-unit motion vectors of the current block based on the CPMVs; deriving a predicted block based on the motion vectors; and reconstructing a current picture based on the predicted block, wherein the motion information candidate list includes an inherited affine candidate, the inherited affine candidate is derived based on candidate blocks coded by affine prediction, from among spatial neighboring blocks of the current block, and the inherited affine candidate is generated up to a pre-defined maximum number.

The present disclosure relates to a method by which a decoding apparatus performs video coding, comprising the steps of: generating a motion information candidate list for a current block; selecting one candidate from among those included in the motion information candidate list; deriving control point motion vectors (CPMVs) of the current block based on the selected candidate; deriving sub-block-unit or sample-unit motion vectors of the current block based on the CPMVs; deriving a predicted block based on the motion vectors; and reconstructing a current picture based on the predicted block, wherein the motion information candidate list includes an inherited affine candidate, the inherited affine candidate is derived based on candidate blocks coded by affine prediction, from among spatial neighboring blocks of the current block, and the inherited affine candidate is generated up to a pre-defined maximum number.

An inter prediction method includes obtaining predicted motion information of a current image block, where the predicted motion information is used to obtain one or more motion vectors of the current image block, the motion vectors include a forward MV and a backward MV for a bidirectional inter prediction, determining a motion vector difference for the current image block, and calculating the motion vectors based on the predicted motion information and the motion vector difference, where the motion vector difference is shared by the forward MV and the backward MV.

An inter prediction method includes obtaining predicted motion information of a current image block, where the predicted motion information is used to obtain one or more motion vectors of the current image block, the motion vectors include a forward MV and a backward MV for a bidirectional inter prediction, determining a motion vector difference for the current image block, and calculating the motion vectors based on the predicted motion information and the motion vector difference, where the motion vector difference is shared by the forward MV and the backward MV.