Moving picture encoding method and decoding method considering motion vectors of blocks adjacent to target block
Decoding method for a moving picture included in a coded stream, including: determining whether a prediction mode (PM) of a target block (TB) is a PM in which motion vector (MV) is not transmitted from an encoding to decoding side, based on coded stream included information; and executing a decoding process when the PM of the TB is determined as the PM in which MV is not transmitted from an encoding to decoding side, wherein a calculation method of a MV used in the second step is selected among plural calculation methods including at least: a first method to select one MV among MVs used in plural adjacent blocks adjacent to the TB; and a second method to calculate a MV based on a MV used in a block that is located at the same position as the TB in another frame positioned backward of a frame including the TB.
1. A method for decoding a moving picture included in a coded stream, comprising:
a first step to determine whether a prediction mode of a target block is a prediction mode in which motion vector is not transmitted from an encoding side to a decoding side or not, based on information included in the coded stream; and
a second step to execute a decoding process when the prediction mode of the target block is determined as the prediction mode in which motion vector is not transmitted from the encoding side to the decoding side,
wherein a determining method of the motion vector used in the second step is selected from among a plurality of determining methods based on a flag for selecting the determining method of the motion vector in the prediction mode in which the motion vector is not transmitted and based on whether a plurality of adjacent blocks adjacent to the target block are located outside of a picture to be decoded or not,
wherein the plurality of determining methods include at least: a first method to select one motion vector as the vector used in the second step from among motion vectors used in the plurality of adjacent blocks adjacent to the target block, a second method to select a zero vector used in the second step, and a third method to calculate the motion vector used in the second step based on another motion vector used in a block that is located at a same position as the target block in another frame positioned backward of a frame including the target block,
wherein a zero vector can be selected as the vector used in the second step even if an adjacent block directly adjacent to the target block at left side is located inside of the picture to be decoded, which has a motion vector that is not a zero vector, and all the adjacent blocks adjacent to the target block at an upper side are located outside of the picture to be decoded, and
wherein the prediction mode in which a motion vector is not transmitted from an encoding side to a decoding side, referred to in the first step and the second step is a different prediction mode from intra prediction mode.