Image encoding device, image encoding method, image decoding device, image decoding method, program, and storage medium
View Patent ↗A prediction set determining section ( 13 ) selects a prediction set from a prediction set group including a plurality of prediction sets having different combinations of prediction modes corresponding to different prediction directions. Further, a prediction mode determining section ( 11 ) selects a prediction mode from the prediction set thus selected. An entropy encoding section ( 4 ) encodes the prediction set thus selected, the prediction mode thus selected, and residual data between an input image and a predicted image formed on the basis of the prediction set and the prediction mode. This allows an image encoding device to carry out predictions from more various angles, thereby improving prediction efficiency.
1. An image decoding device for decoding encoded data so as to form a decoded image, comprising:
a decoder configured to decode, from the encoded data,
(i) an encode parameter including intra prediction mode information and
(ii) prediction residual data, wherein the intra prediction mode information indicates that an intra prediction mode is one of a plurality of intra prediction modes for use in generating a predicted image of the target block to be decoded;
an intra prediction mode information obtaining section configured to obtain, from the encode parameter,
(i) a flag which indicates whether or not any of a plurality of intra prediction mode candidates related to a target block to be decoded is identical to an intra prediction mode for use in generating a predicted image of the target block to be decoded,
(ii) first intra prediction mode selection information which, in a case where the flag indicates that any of the plurality of intra prediction mode candidates is identical to the intra prediction mode for use in generating a predicted image of the target block to be decoded, designates which one of the plurality of intra prediction mode candidates is to be used as a prediction mode for use in generating a predicted image of the target block to be decoded, and
(iii) second intra prediction mode selection information which, in a case where the flag indicates that none of the plurality of intra prediction mode candidates is identical to the intra prediction mode for use in generating a predicted image of the target block to be decoded, designates which one of remaining intra prediction modes other than the plurality of intra prediction mode candidates is to be applied to the target block to be decoded;
an intra prediction mode selector configured to select, by use of the first intra prediction mode selection information or the second intra prediction mode selection information, an intra prediction mode for use in generating a predicted image of the target block to be decoded;
a predictor configured to form, on the basis of the intra prediction mode thus selected, a predicted image of the target block to be decoded; and
an adder configured to form a decoded image of the target block to be decoded by adding the predicted image formed by the predictor and the prediction residual data obtained by decoding the encoded data.
2. An image decoding device as set forth in claim 1 , wherein the intra prediction mode designated by the first intra prediction mode selection information includes an intra prediction mode of a decoded block positioned on the left or on the top of the target block to be decoded.
3. An image encoding device for encoding an input image, comprising:
a determination component configured to determine an intra prediction mode to be used for forming a predicted image of a target block to be encoded,
wherein the intra prediction mode is determined from among a plurality of intra prediction modes for use in generating a predicted image of the target block to be encoded;
an intra prediction mode information generator configured to generate
(i) a flag which indicates whether or not any of a plurality of intra prediction mode candidates of the target block to be encoded is identical to the intra prediction mode determined by the determination component,
(ii) first intra prediction mode selection information which, in a case where the flag indicates that any of the plurality of intra prediction mode candidates is identical to the intra prediction mode determined by the determination component, designates which one of the plurality of intra prediction mode candidates is to be used as an intra prediction mode for use in generating a predicted image of the target block to be encoded, and
(iii) second intra prediction mode selection information which, in a case where the flag indicates that none of the plurality of intra prediction mode candidates is identical to the intra prediction mode determined by determination component, designates which one of the remaining intra prediction modes other than the plurality of intra prediction mode candidates is to be used as an intra prediction mode for use in generating a predicted image of the target block to be encoded; and
an encoder configured to encode, as an encode parameter related to intra prediction mode information, (i) the flag and the first intra prediction mode selection information or (ii) the flag and the intra prediction mode selection second information.
4. An image encoding device as set forth in claim 3 , wherein the intra prediction mode designated by the first intra prediction mode selection information includes an intra prediction mode of an encoded block positioned on the left or on the top of the target block to be encoded.