Several improvements for use with Bidirectionally Predictive (B) pictures within a video sequence are provided. In certain improvements Direct Mode encoding and/or Motion Vector Prediction are enhanced using spatial prediction techniques. In other improvements Motion Vector prediction includes temporal distance and subblock information, for example, for more accurate prediction. Such improvements and other presented herein significantly improve the performance of any applicable video coding system/logic.

Several improvements for use with Bidirectionally Predictive (B) pictures within a video sequence are provided. In certain improvements Direct Mode encoding and/or Motion Vector Prediction are enhanced using spatial prediction techniques. In other improvements Motion Vector prediction includes temporal distance and subblock information, for example, for more accurate prediction. Such improvements and other presented herein significantly improve the performance of any applicable video coding system/logic.

A moving picture coding apparatus, method, and medium for coding a current block of a picture are provided. A motion vector candidate list is generated that includes motion vector candidates and, for each of the motion vector candidates, a value. The motion vector candidates include a first candidate and a second candidate. The second candidate is arranged before the first candidate in the motion vector candidate list. The first candidate is sorted before the second candidate in the motion vector candidate list based on the value of the first candidate and the value of the second candidate. The value of the first candidate is higher than the value of the second candidate. For each of the motion vector candidates, the value is based on a number of times the motion vector candidate is selected as a motion vector predictor for neighboring blocks.

A moving picture coding apparatus, method, and medium for coding a current block of a picture are provided. A motion vector candidate list is generated that includes motion vector candidates and, for each of the motion vector candidates, a value. The motion vector candidates include a first candidate and a second candidate. The second candidate is arranged before the first candidate in the motion vector candidate list. The first candidate is sorted before the second candidate in the motion vector candidate list based on the value of the first candidate and the value of the second candidate. The value of the first candidate is higher than the value of the second candidate. For each of the motion vector candidates, the value is based on a number of times the motion vector candidate is selected as a motion vector predictor for neighboring blocks.

The present invention is about an image encoding/decoding method and apparatus. According to present invention, a method of decoding an image, the method comprising, deriving an initial motion vector of a current block; deriving a refined motion vector by using the initial motion vector; and generating a prediction block of the current block by using the refined motion vector.

The present invention is about an image encoding/decoding method and apparatus. According to present invention, a method of decoding an image, the method comprising, deriving an initial motion vector of a current block; deriving a refined motion vector by using the initial motion vector; and generating a prediction block of the current block by using the refined motion vector.

A moving picture coding apparatus for coding a current block is provided. A first candidate is derived from a first motion vector that has been used to code a first block, and it is determined whether a total number of candidates including the first candidate is less than a maximum candidate number. A second candidate having a second motion vector is derived when the total number of the candidates is less than the maximum candidate number, with the second motion vector including a zero vector. A candidate is selected from a plurality of candidates including the first candidate and the second candidate, and the current block is decoded using the selected candidate.

A moving picture coding apparatus for coding a current block is provided. A first candidate is derived from a first motion vector that has been used to code a first block, and it is determined whether a total number of candidates including the first candidate is less than a maximum candidate number. A second candidate having a second motion vector is derived when the total number of the candidates is less than the maximum candidate number, with the second motion vector including a zero vector. A candidate is selected from a plurality of candidates including the first candidate and the second candidate, and the current block is decoded using the selected candidate.

A video decoding method performed by a decoding apparatus includes the steps of: deriving control points (CP) for a current block; acquiring movement vectors for the CPs; deriving a sample unit movement vector in the current block on the basis of the acquired movement vectors; and deriving a prediction sample for the current block on the basis of the sample unit movement vector. According to the present invention, it is possible to effectively perform, through sample unit motion vectors, inter-prediction not only in a case where an image in the current block is plane-shifted but also in a case where there are various image distortions.

A video decoding method performed by a decoding apparatus includes the steps of: deriving control points (CP) for a current block; acquiring movement vectors for the CPs; deriving a sample unit movement vector in the current block on the basis of the acquired movement vectors; and deriving a prediction sample for the current block on the basis of the sample unit movement vector. According to the present invention, it is possible to effectively perform, through sample unit motion vectors, inter-prediction not only in a case where an image in the current block is plane-shifted but also in a case where there are various image distortions.