Method for encoding and decoding moving vector, encoder and decoder for moving vector, and recording medium stored with encoding and decoding programs for moving vector

A motion vector encoding method used in a motion-picture encoding method which uses motion-compensating interframe prediction, the motion vector encoding method comprising the steps of:

• calculating a length component of a motion vector when the motion vector is encoded;
• encoding the calculated length component;
• determining the value of the calculated length component;
• calculating a direction component of the motion vector;
• selectively determining the contents of an encoding table for encoding the direction component of the motion vector, in accordance with the determined value of the length component;
• and
• encoding the calculated direction component based on the selected encoding table.

A motion vector encoding apparatus used for a motion-picture encoding method which uses motion-compensating interframe prediction, the motion vector encoding apparatus comprising:

• length-component calculating means for calculating a length component of a motion vector;
• length-component encoding means for encoding the calculated length component and outputting the encoded result as length component information;
• direction-component calculating means for calculating a direction component of the motion vector;
• and
• direction-component encoding means for encoding the calculated direction component and outputting the encoded result as direction component information.

A motion vector encoding apparatus used for a motion-picture encoding method which uses motion-compensating interframe prediction, the motion vector encoding apparatus comprising:

• length-component calculating means for calculating a length component of a motion vector when the motion vector is encoded;
• length-component determining means for determining the value of the length component of the motion vector;
• length-component encoding means for encoding the calculated length component;
• direction-component calculating means for calculating a direction component of the motion vector;
• encoding-table switching means for selectively determining an encoding table for encoding the direction component of the motion vector, in accordance with the length component;
• and
• direction-component encoding means for encoding the calculated direction component based on the selected encoding table.

A computer-readable storage medium storing a motion vector encoding program for executing a motion vector encoding operation used in a motion-picture encoding method which uses motion-compensating interframe prediction, the encoding program including:

• a first step of calculating a length component of a motion vector;
• a second step of encoding the calculated length component and outputting the encoded result as length component information;
• a third step of calculating a direction component of the motion vector;
• and
• a fourth step of encoding the calculated direction component and outputting the encoded result as direction component information.

A computer-readable storage medium storing a motion vector encoding program for executing a motion vector encoding operation used in a motion-picture encoding method which uses motion-compensating interframe prediction, the program including the steps of:

• calculating a length component of a motion vector when the motion vector is encoded;
• encoding the calculated length component;
• determining the value of the calculated length component;
• calculating a direction component of the motion vector;
• selectively determining the contents of an encoding table for encoding the direction component of the motion vector, in accordance with the determined value of the length component;
• and
• encoding the calculated direction component based on the selected encoding table.

A motion vector encoding method used in a motion-picture encoding method which uses motion-compensating interframe prediction, the motion vector encoding method comprising:

• a first step of calculating a length component of a motion vector;
• a second step of encoding the calculated length component and outputting the encoded result as a length component information;
• a third step of calculating a direction component of the motion vector;
• and
• a fourth step of encoding the calculated direction component and outputting the encoded result as direction component information;
• wherein in the fourth step, one of a plurality of encoding tables is selected, the selected tables corresponding to the value of the length component calculated in the first step, wherein each encoding table stores codes corresponding to each calculated direction component of the motion vector, and the number of possible values for the direction component of the motion vector depends on the value of the length component of the motion vector, and the direction component of the motion vector calculated in the third step is encoded with reference to the selected encoding table.

A motion vector decoding method for decoding a motion vector which was encoded by a motion vector encoding method which uses motion-compensating interframe prediction and includes a first step of calculating a length component of a motion vector, a second step of encoding the calculated length component and outputting the encoded result as a length component information, a third step of calculating a direction component of the motion vector, and a fourth step of encoding the calculated direction component and outputting the encoded result as direction component information, the decoding method comprising:

• a fifth step of decoding the length component of the motion vector based on the length component information obtained by the motion vector encoding method;
• a sixth step of decoding the direction component of the motion vector based on the direction component information obtained by the motion vector encoding method and performed subsequent to the fifth step;
• wherein in the sixth step, one of a plurality of decoding tables is selected, the selected table corresponding to the value of the length component decoded in the fifth step, wherein each decoding table stores values of the direction component corresponding to the code of the decoded direction component, and the number of possible values for the decoded direction component of the motion vector depends on the value of the decoded length component of the motion vector, and the encoded direction component of the motion vector is decoded with reference to the selected decoding table;
• and
• a seventh step of synthesizing the motion vector using the length and direction components decoded in the fifth and sixth steps.

A motion vector encoding apparatus used for a motion picture encoding method which uses motion-compensating interframe prediction, the motion vector encoding apparatus comprising:

• length-component calculating means for calculating a length component of a motion vector;
• length-component encoding means for encoding the calculated length component and outputting the encoded result as length component information;
• direction-component encoding means for encoding the calculated direction component and outputting the encoded result as direction component information;
• switching signal output means for outputting a switching signal in accordance with the length component of the motion vector;
• wherein the direction-component encoding means previously stores a plurality of encoding tables, wherein each encoding table stores codes corresponding to each calculated direction component of the motion vector, and the number of possible values for the direction component of the motion vector depends on the value of the length component of the motion vector;
• and
• the direction-component encoding means selects one of the encoding tables which corresponds to the length component of the motion vector in accordance with the switching signal output from the switching signal output means and encodes the direction component of the motion vector based on the selected encoding table.

A motion vector decoding apparatus for decoding a motion vector encoded by a motion vector encoding apparatus having length-component calculating means for calculating a length component of a motion vector, length-component encoding means for encoding the calculated length component and outputting the encoded result as length component information, and direction-component encoding means for encoding the calculated direction component and outputting the encoded result as direction component information, the decoding apparatus comprising:

• length-component decoding means for decoding the length component of the motion vector based on the length component information output from the length-component encoding means;
• direction-component decoding means for decoding the direction component of the motion vector based on the direction component information output from the direction-component encoding means after the length-component decoding means decodes the length component of the motion vector;
• vector synthesizing means for synthesizing the motion vector using the decoded length and direction components;
• switching signal output means for outputting a switching signal in accordance with the decoded length component of the motion vector;
• wherein the direction-component decoding means previously stores a plurality of decoding tables, wherein each decoding table stores values of the direction component corresponding to the code of the decoded direction component, and the number of possible values for the decoded direction component of the motion vector depends on the value of the decoded length component of the motion vector;
• and
• the direction-component decoding means selects one of the decoding tables which corresponds to the length component of the motion vector in accordance with the switching signal output from the switching signal output means, and decodes the direction component of the motion vector based on the selected decoding table.

A computer-readable storage medium storing a motion vector encoding program for executing a motion vector encoding operation used in a motion-picture encoding method which uses motion-compensating interframe prediction, the encoding program including:

• a first step of calculating a length component of a motion vector;
• a second step of encoding the calculated length component and outputting the encoded result as a length component information;
• a third step of calculating a direction component of the motion vector;
• and
• a fourth step of encoding the calculated direction component and outputting the encoded result as direction component information;
• wherein in the fourth step, one of a plurality of encoding tables is selected, the selected table corresponding to the value of the length component calculated in the first step, wherein each encoding table stores codes corresponding to each calculated direction component of the motion vector, and the number of possible values for the direction component of the motion vector depends on the value of the length component of the motion vector;
• and
• the direction component of the motion vector, calculated in the third step, is encoded with reference to the selected encoding table.

A computer-readable storage medium storing a motion vector decoding program for decoding a motion vector which was encoded by executing a motion vector encoding operation used in a motion-picture encoding method which uses motion-compensating interframe prediction, the encoding operation including a first step of calculating a length component of a motion vector, a second step of encoding the calculated length component and outputting the encoded result as a length component information, a third step of calculating a direction component of the motion vector, and a fourth step of encoding the calculated direction component and outputting the encoded result as direction component information, the decoding program including:

• a fifth step of decoding the length component of the motion vector based on the length component information obtained by the motion vector encoding method;
• a sixth step of decoding the direction component of the motion vector based on the direction component information obtained by the motion vector encoding method subsequent to performing the fifth step;
• wherein in the sixth step, one of a plurality of decoding tables is selected, the selected table corresponding to the value of the length component decoded in the fifth step, wherein each decoding table stores values of the direction component corresponding to the code of the decoded direction component, and the number of possible values for the decoded direction component of the motion vector depends on the value of the decoded length component of the motion vector, and the encoded direction component of the motion vector is decoded with reference to the selected table;
• and
• a seventh step of synthesizing the motion vector using the length and direction components decoded in the fifth and sixth steps.