Image encoding device, image decoding device, image encoding method, and image decoding method

An image decoding device for receiving an image-encoded bit stream obtained by dividing each picture of a digital video signal into predetermined unit regions and carrying out, for each of the predetermined unit regions, compression encoding using a motion compensation prediction, and restoring the digital video signal, the image decoding device comprising:

• a decoding unit for restoring a motion vector by extracting virtual-pixel-accuracy specification information for specifying an upper limit of an accuracy of a pixel position indicated by the motion vector from the image-encoded bit stream, and by extracting, for each region to which the motion vector is assigned, encoded data of the motion vector from the image-encoded bit stream;
• and
• a prediction unit for generating, based on the motion vector decoded by the decoding unit, a motion-compensation predicted image,
• wherein the decoding unit decodes the motion vector based on a magnitude of data restored from the encoded data of the motion vector extracted from the image-encoded bit stream and a motion vector used for prediction of the motion vector to be decoded, and the virtual-pixel-accuracy specification information extracted from the image-encoded bit stream.

An image decoding method of receiving an image-encoded bit stream obtained by dividing each picture of a digital video signal into predetermined unit regions and carrying out, for each of the predetermined unit regions, compression encoding using a motion compensation prediction, and restoring the digital video signal, the image decoding method comprising:

• a decoding step of restoring a motion vector by extracting virtual-pixel-accuracy specification information for specifying an upper limit of an accuracy of a pixel position indicated by the motion vector from the image-encoded bit stream, and by extracting, for each region to which the motion vector is assigned, encoded data of the motion vector from the image-encoded bit stream;
• and
• a prediction step of generating, based on the decoded motion vector, a motion-compensation predicted image,
• wherein the decoding step comprises decoding the motion vector based on a magnitude of data restored from the encoded data of the motion vector extracted from the image-encoded bit stream and a motion vector used for prediction of the motion vector to be decoded, and the virtual-pixel-accuracy specification information extracted from the image-encoded bit stream.