Image coding device, image coding method, and image coding integrated circuit

Abstract

When compression encoding processing of an image is performed in units of macroblocks using pipeline structure, application of the skip mode or the like according to MPEG4AVC to compression encode an encoding target block requires motion vectors and the like of adjacent blocks of the encoding target block. However, depending on the structure of the pipeline stages, the motion vectors and the like may not be determined. In such cases, the skip mode cannot be applied to compression encode the encoding target block. The present invention aims to solve this problem and (i) calculates all motion information candidates, of the encoding target block, corresponding to all motion information selectable by a previous block of the encoding target block, and (ii) selects, as the motion information of the encoding target block in the skip mode, the motion information corresponding to the motion information determined for the previous block.

1 . An image encoding apparatus which compression encodes an image in units of blocks of a predetermined size, the image encoding apparatus comprising:
 a first processing unit operable to sequentially generate candidate designation information corresponding to each of the blocks, based on candidate designation information corresponding to a prior block which has been processed prior to the block, each candidate designation information designating a plurality of prediction images as candidates for a prediction image of the corresponding block, and   a second processing unit operable to, in parallel with generation of the candidate designation information corresponding to the block by the first processing unit, (i) select, as a prediction image of one of the blocks which has been processed by the first processing unit, a prediction image from among the plurality of prediction images indicated by the candidate designation information corresponding to the one of the blocks, based on prediction image designation information designating a prediction image of a block processed prior to the one of the blocks, (ii) outputs a difference signal showing a difference which is between the selected prediction image and an original image of the one of the blocks, and is to be reflected in a result of compression encoding of the one of the blocks, and (iii) generates prediction image designation information designating the selected prediction image.   
   
   
       2 . The image encoding apparatus of  claim 1  compression encoding a plurality of images which are input sequentially, wherein
 each candidate designation information includes designation information designating, as one of the candidates for the prediction image of the corresponding block, one of the plurality of prediction images which is generated based on a motion vector detected by searching one of the plurality of images that is other than the image being compression encoded.   
   
   
       3 . The image encoding apparatus of  claim 1 , wherein
 each candidate designation information includes designation information designating, as a plurality of candidates among the candidates for the prediction image of the corresponding block, out of the plurality of prediction images, two or more prediction images generated based on motion vectors of a plurality of adjacent blocks including the prior block of the corresponding block, the plurality of adjacent blocks being located in predetermined positions with respect to the corresponding block.   
   
   
       4 . The image encoding apparatus of  claim 1  further comprising:
 a third processing unit operable to cause each candidate designation information to include designation information designating, as one of the candidates for the prediction image of the corresponding block, one of the plurality of prediction images which is generated based on one or more pixel values of one or more pixels located in predetermined positions with respect to the corresponding block, wherein   the second processing unit selects the prediction image for the prior block of the corresponding block, from among the plurality of prediction images indicated by the candidate designation information caused by the third processing unit to have the designation information.   
   
   
       5 . The image encoding apparatus of  claim 1 , wherein
 each candidate designation information is generated also based on prediction image designation information of one of the blocks which has been processed by the second processing unit.   
   
   
       6 . The image encoding apparatus of  claim 1 , wherein
 each candidate designation information is generated based on information designating only some of the plurality of prediction images which are candidates for the prediction image of the prior block of the corresponding block.   
   
   
       7 . The image encoding apparatus of  claim 1  performing processing in a pipeline structure composed of two stages that are a first stage and a second stage, wherein
 the first processing unit processes the first stage and includes:
 a motion detection unit operable to generate, for each of the blocks, the candidate designation information including designation information designating, as one of the candidates for the prediction image of the block, one of the plurality of prediction images which is generated based on a motion vector detected by searching an image other than the image being compression encoded; and 
 a motion vector speculative calculation unit operable to cause the candidate designation information of the block to include designation information designating, as a plurality of candidates among the candidates for the prediction image of the block, out of the plurality of prediction images, two or more prediction images generated based on motion vectors of a plurality of adjacent blocks including the prior block, the plurality of adjacent blocks being located in predetermined positions with respect to the block, and 
   the second processing unit processes the second stage and includes:
 a motion vector determination unit operable to, based on the prediction image designation information of the block prior to the one of the blocks, select a prediction image out of the one or more prediction images designated by the designation information caused by the motion vector speculative calculation unit to be included in the candidate designation information of the one of the blocks; and 
 a mode judgement unit operable to (i) select the prediction image for the one of the blocks, from among the prediction image selected by the motion vector determination unit and the prediction image indicated by the designation information generated by the motion detection unit, (ii) output the difference signal, and (iii) generate the prediction image designation information designating the selected prediction image. 
   
   
   
       8 . An image encoding method which compression encodes an image in units of blocks of a predetermined size, the image encoding method comprising:
 a first processing step of sequentially generating candidate designation information corresponding to each of the blocks, based on candidate designation information corresponding to a prior block which has been processed prior to the block, each candidate designation information designating a plurality of prediction images as candidates for a prediction image of the corresponding block, and   a second processing method of, in parallel with generation of the candidate designation information corresponding to the block in the first processing step, (i) selecting, as a prediction image of one of the blocks which has been processed by the first processing unit, a prediction image from among the plurality of prediction images indicated by the candidate designation information corresponding to the one of the blocks, based on prediction image designation information designating a prediction image of a block processed prior to the one of the blocks, (ii) outputting a difference signal showing a difference which is between the selected prediction image and an original image of the one of the blocks, and is to be reflected in a result of compression encoding of the one of the blocks, and (iii) generating prediction image designation information designating the selected prediction image.   
   
   
       9 . A computer program for causing a computer to perform compression encoding processing which compression encodes an image in units of blocks of a predetermined size, the compression encoding processing comprising:
 a first processing step of sequentially generating candidate designation information corresponding to each of the blocks, based on candidate designation information corresponding to a prior block which has been processed prior to the block, each candidate designation information designating a plurality of prediction images as candidates for a prediction image of the corresponding block, and   a second processing method of, in parallel with generation of the candidate designation information corresponding to the block in the first processing step, (i) selecting, as a prediction image of one of the blocks which has been processed by the first processing unit, a prediction image from among the plurality of prediction images indicated by the candidate designation information corresponding to the one of the blocks, based on prediction image designation information designating a prediction image of a block processed prior to the one of the blocks, (ii) outputting a difference signal showing a difference which is between the selected prediction image and an original image of the one of the blocks, and is to be reflected in a result of compression encoding of the one of the blocks, and (iii) generating prediction image designation information designating the selected prediction image.   
   
   
       10 . An integrated circuit used for image encoding, the integrated circuit compression encoding an image in units of blocks of a predetermined size and comprising:
 a first processing unit operable to sequentially generate candidate designation information corresponding to each of the blocks, based on candidate designation information corresponding to a prior block which has been processed prior to the block, each candidate designation information designating a plurality of prediction images as candidates for a prediction image of the corresponding block, and   a second processing unit operable to, in parallel with generation of the candidate designation information corresponding to the block by the first processing unit, (i) select, as a prediction image of one of the blocks which has been processed by the first processing unit, a prediction image from among the plurality of prediction images indicated by the candidate designation information corresponding to the one of the blocks, based on prediction image designation information designating a prediction image of a block processed prior to the one of the blocks, (ii) outputs a difference signal showing a difference which is between the selected prediction image and an original image of the one of the blocks, and is to be reflected in a result of compression encoding of the one of the blocks, and (iii) generates prediction image designation information designating the selected prediction image.