Image predictive decoding apparatus

There is disclosed image predictive coding apparatus and method, image predictive decoding apparatus and method, and recording medium which stores therein the image predictive coding method or the image predictive decoding method, of which the transform efficiency is remarkably improved in comparison with the prior art. According to the image predictive coding apparatus and method, when dividing inputted image data to be coded into image data of a plurality of small regions which are adjacent to each other and coding the image data of an objective small region to be processed among the image data of the plurality of divided small regions which are adjacent to each other, reconstructed image data of a reproduction small region adjacent to the image data of the objective small region to be processed is used as image data of an intra-frame prediction small region of the objective small region to be processed, the image data of the intra-frame prediction small region is used as image data of an optimum prediction small region and image data of a difference small region which are differences between the image data of the objective small region to be processed and the image data of the optimum prediction small region is generated. Then, the generated image data of the difference small region is coded and outputted, and then the coded image data of the difference small region is decoded, so that the reconstructed image data of the reproduction small region is generated by adding the decoded image data of the difference small region to the image data of the optimum prediction small region.

What is claimed:

1. An image predictive decoding apparatus for decoding an input bit stream including variable length coded DCT coefficients, said apparatus comprising:

a variable length decoder operable to decode the variable length coded DCT coefficients into a one-dimensional array of DCT coefficients; and

a prediction unit operable to predict a DC coefficient of a current block from a DC coefficient of an immediately adjacent block adaptively selected from either an above block or a left block, and further operable to predict AC coefficients of the current block from the selected block for the DC coefficient prediction.

2. An image predictive decoding apparatus of claim 1, wherein the DC coefficient of the current block is predicted from the DC coefficient of the immediately adjacent block selected from either the left block or the above block according to a least bit use rule.

3. An image predictive decoding apparatus of claim 1, wherein the prediction of the DC coefficient of the current block is independently repeated for every block of a macroblock.

4. An image predictive decoding apparatus for decoding a input bit stream, the input bit stream is generated by:

sampling an image signal into a plurality of blocks; transforming the image signal of the blocks into a two dimensional array of DCT coefficients having a DC coefficient and AC coefficients; predicting at least one of a DC and AC coefficient of a current block from the DCT coefficients of an immediately adjacent block adaptively selected from either an above block or a left block, variable length encoding the DCT coefficients; and providing an indication bit which indicates that the AC coefficients of the current block are predicted in coding;

said image predictive decoding apparatus comprising:

a variable length decoder operable to decode the variable length coded DCT coefficients into a one-dimensional array of DCT coefficients; and

a prediction device operable to predict a DC coefficient of a current block from a DC coefficient of an immediately adjacent block adaptively selected from either an above block or a left block; and

wherein said prediction device is further operable to predict AC coefficients of the current block from the selected block for the DC coefficient prediction when the indication bit indicates that the AC coefficients of the current block are predicted in coding.

5. An image predictive decoding apparatus of claim 4, herein the DC coefficient of the current block is predicted from the DC coefficient of the immediately adjacent block selected from either the left block or the above block according to a least bit use rule.

6. An image predictive decoding apparatus of claim 2, wherein the prediction of the DC coefficient of the current block is independently repeated for every block of a macroblock.

7. An image prediction method comprising:

receiving a bit stream including DCT coefficients of a plurality of blocks composing an image signal;

predicting a DC coefficient of a current block from a DC coefficient of an immediately adjacent block adaptively selected from either an above block or a left block; and further predicting AC coefficients of the current block from the selected block for the DC coefficient prediction.