Spatial prediction based intra coding

Abstract

A method and device for coding a digital image using intra-mode block prediction, wherein a list of prediction modes for each combination of prediction modes of the neighboring blocks is obtained. The modes assigned to each combination of prediction modes may be divided into two groups. The first group includes n (where n is smaller than the overall number of available modes) most probable prediction modes and the second group includes the remaining modes. The modes in the first group are ordered according to their probability. This order may be specified as a list of modes ordered from most probable to the least probable mode. The modes belonging to the second group may be ordered in some predetermined manner, which may be specified depending on the information already available to the decoder.

1 - 15 . (canceled)  
   
   
       16 . A method, comprising: 
 decoding information from a bitstream, wherein the bitstream comprises image data representative of a plurality of image blocks using a plurality of spatial prediction modes for intra-mode block prediction, wherein the spatial prediction mode of a current block is determined based on a plurality of derived prediction modes, which are derived based on the spatial prediction modes of a plurality of neighboring blocks of the current block, and wherein    said plurality of derived prediction modes are grouped into a first group and a second group, the first group having a first number of first prediction modes and the second group having a second number of second prediction modes, wherein the first number is smaller than the number of the derived prediction modes, and wherein the first prediction modes have a higher probability of occurrence than the second prediction modes,    wherein the information is indicative of whether the spatial prediction mode of the current block belongs to the first group or the second group and    determining the spatial prediction mode of the current block based on the decoded information.    
   
   
       17 . The method of  claim 16 , wherein the first prediction modes are ordered according to the probability of occurrence among the first prediction modes.  
   
   
       18 . The method of  claim 16 , wherein the second prediction modes are arranged in a predetermined fashion known to the decoding device.  
   
   
       19 . (canceled)  
   
   
       20 . The method of  claim 16 , wherein an ordered set is provided to the decoding device so as to allow the decoding device to determine the order of the second prediction modes based on the ordered set.  
   
   
       21 . A decoder capable of decoding information from a bitstream, comprising: 
 means, responsive to decoded information, for determining whether a spatial prediction mode of a current block of a plurality of image blocks belongs to a first group or a second group, wherein a plurality of spatial prediction modes are used for intra mode block prediction of the image blocks, and wherein the spatial prediction mode of the current block is determined based on a plurality of derived prediction modes, which are derived based on the spatial prediction modes of a plurality of neighboring blocks of the current block and said plurality of derived prediction modes are grouped into the first group and the second group, the first group having a first number of first prediction modes and the second group having a second number of second prediction modes, wherein the first number is smaller than the number of the derived prediction modes, and wherein the first prediction modes have a higher probability of occurrence than the second prediction modes, and    means for selecting the spatial prediction mode based on said determining.    
   
   
       22 . The decoder of  claim 21 , wherein the first prediction modes are ordered according to the probability of occurrence among the first prediction modes.  
   
   
       23 . The decoder of  claim 21 , wherein the second prediction modes are arranged in a predetermined fashion, said decoder further comprising 
 means for storing information indicative to said predetermined fashion.    
   
   
       24 . The decoder of  claim 21 , said determining means is also capable of determining based on the decoded information which of the first prediction modes has a highest probability of occurrence when the derived prediction mode with the highest occurrence mode is selected for use in decoding the current block.  
   
   
       25 - 29 . (canceled)  
   
   
       30 . A decoder configured for decoding information from a bitstream, comprising: 
 a module, responsive to decoded information, for determining whether a spatial prediction mode of a current block of a plurality of image blocks belongs to a first group or a second group, wherein a plurality of spatial prediction modes are used for intra-mode block prediction, and the spatial prediction mode of a current block is determined based on a plurality of derived prediction modes, which are derived based on the spatial prediction modes of a plurality of neighboring blocks of the current block, and wherein said plurality of derived prediction modes are grouped into the first group and the second group, the first group having a first number of first prediction modes and the second group having a second number of second prediction modes, wherein the first number is smaller than the number of the derived prediction modes, and wherein the first prediction modes have a higher probability of occurrence than the second prediction modes, and    means for selecting the spatial prediction mode based on said determining.    
   
   
       31 . The decoder of  claim 30 , wherein the first prediction modes are ordered according to the probability of occurrence among the first prediction modes.  
   
   
       32 . The decoder of  claim 30 , wherein the second prediction modes are arranged in a predetermined fashion, said decoder further comprising 
 a module for storing information indicative to said predetermined fashion.    
   
   
       33 . The decoder of  claim 30 , wherein the module is configured for determining based on the decoded information which of the first prediction modes has a highest probability of occurrence when the derived prediction mode with the highest occurrence mode is selected for use in decoding the current block.  
   
   
       34 . A software application product embedded in a computer readable storage medium comprising a software application, the software application comprising programming codes for carrying out the method according to  claim 16.