Motion vector predictive encoding method, motion vector decoding method, predictive encoding apparatus and decoding apparatus, and storage media storing motion vector predictive encoding and decoding programs

Abstract

A motion vector predictive encoding method, a motion vector decoding method, a predictive encoding apparatus, a decoding apparatuses, and storage media storing motion vector predictive encoding and decoding programs are provided, thereby reducing the amount of generated code with respect to the motion vector, and improving the efficiency of the motion-vector prediction. If the motion-compensating mode of the target small block to be encoded is the global motion compensation, the encoding mode of an already-encoded small block is the interframe coding mode, and the motion-compensating mode of the already-encoded small block is the global motion compensation, then the motion vector of the translational motion model is determined for each pixel of the already-encoded small block, based on the global motion vector (steps S1-S5). Next, the representative motion vector is calculated as the predicted vector, based on the motion vector of each pixel of the already-encoded small block (step S6). Finally, the prediction error is calculated for each component of the motion vector and each prediction error is encoded (steps S7 and S8).

Description

TECHNICAL FIELD [0001] The present invention relates to motion vector predictive encoding and decoding methods, predictive encoding and decoding apparatuses, and storage media storing motion vector predictive encoding and decoding programs. These methods, apparatuses, and storage media are used for motion-compensating interframe prediction for motion picture encoding. BACKGROUND ART [0002] The interframe predictive coding method for coding motion pictures (i.e., video data) is known, in which an already-encoded frame is used as a prediction signal so as to reduce temporal redundancy. In order to improve the efficiency of the time-based prediction, a motion-compensating interframe prediction method is used in which a motion-compensated picture signal is used as a prediction signal. The number and the kinds of components of the motion vector used for the motion compensation are determined depending on the assumed motion model used as a basis. For example, in a motion model in which on...

AI Technical Summary

Benefits of technology

[0055] According to the motion vector predictive encoding method, decoding method, predictive encoding apparatus, decoding apparatus, motion vector predictive encoding program, and decoding program of the present invention, the motion vector can be predicted between motion vectors of different motion models, and also between motion vectors of the global motion compensation and the local motion compensation. Therefore, the amount of generated code with respect to the motion vector can be reduced.

[0056] In addition, if the predicted vector determined based on the global motion parameters is not within the range of the local motion vector, the predicted vector can be clipped to have the maximum value or the minimum value of the range. Therefore, if “fcode=3” (the motion vector range is from −64 to +63.5 pixels), the motion vector of the present block: (Vx, Vy)=(+48, +36.5), and the predicted vector calculated based on the global motion parameters: (PVx, PVy)=(+102, +75), then the predicted vector (PVx, PVy) is clipped to “(+63.5, +63.5)”. Accordingly, the prediction error (MVDx, MVDy) is “(−15.5, −27)” and the absolute values thereof are smaller than those obtained by the above-mentioned conventional method in which the prediction error is “(−54, −38.5)”. The smaller the absolute values of the prediction error, the shorter the length of the codeword assigned to a difference between two motion vectors; thus, the total amount of code can be reduced.

Problems solved by technology

It may be impossible to compensate more complicated motions with a simpler model, such as MPEG-1, which has few components of the motion vector.

However, redundancy of the motion vector may also occur between different motion models.

However, in the conventional method, such redundancy between motion vectors of different motion models cannot be reduced because no motion vector of a motion model which is differs from the present motion model is predicted based on the motion vector of the present model.

However, the range of the local motion vector is smaller than the above range and the prediction may have a large error.

Therefore, there is a disadvantage in that the amount of code are increased due to the prediction of the motion vector.

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