Image decoding method and apparatus based on a signal type of the control parameter of the current block

Abstract

The image decoding method includes: determining a context for use in a current block to be processed, from among a plurality of contexts; and performing arithmetic decoding on a bit sequence corresponding to the current block, using the determined context, wherein in the determining: the context is determined under a condition that control parameters of neighboring blocks of the current block are used, when the signal type is a first type, the neighboring blocks being a left block and an upper block of the current block; and the context is determined under a condition that the control parameter of the upper block is not used, when the signal type is a second type.

The invention claimed is: 
     
       1. An image decoding method using arithmetic decoding, the method comprising:
 determining a context for use in a current block, from among a plurality of contexts;   performing arithmetic decoding on a bit sequence corresponding to the current block, using the determined context to decode a binary sequence, the bit sequence being obtained by performing arithmetic coding on a control parameter of the current block; and   inversely binarizing the binary sequence to decode the control parameter of the current block,   wherein the determining of a context includes:   determining a signal type of the control parameter of the current block;   determining the context under a first condition that decoded control parameters of neighboring blocks of the current block are used, when the signal type is a first type, the neighboring blocks being a left block and an upper block of the current block; and   determining the context under a second condition that a predetermined fixed value is used and the decoded control parameters of the left block and the upper block are not used, when the signal type is a second type different from the first type,   wherein the first type is one of (i) a flag indicating whether or not the current block is partitioned into a plurality of blocks and (ii) a flag indicating whether or not the current block is to be skipped, and   the second type is a flag indicating whether or not a merge mode is used for the current block.   
     
     
       2. An image decoding apparatus using arithmetic decoding, the apparatus comprising:
 a context control unit configured to determine a context for use in a current block, from among a plurality of contexts;   an arithmetic decoding unit configured to perform arithmetic decoding on a bit sequence corresponding to the current block, using the determined context to decode a binary sequence, the bit sequence being obtained by performing arithmetic coding on a control parameter of the current block; and   an inverse binarization unit configured to inversely binarize the binary sequence to decode the control parameter of the current block,   wherein the context control unit is configured to:   determine a signal type of the control parameter of the current block;   determine the context under a first condition that decoded control parameters of neighboring blocks of the current block are used, when the signal type is a first type, the neighboring blocks being a left block and an upper block of the current block; and   determine the context under a second condition that a predetermined fixed value is used and the decoded control parameters of the left block and the upper block are not used, when the signal type is a second type different from the first type,   wherein the first type is one of (i) a flag indicating whether or not the current block is partitioned into a plurality of blocks and (ii) a flag indicating whether or not the current block is to be skipped, and   the second type is a flag indicating whether or not a merge mode is used for the current block.   
     
     
       3. A decoding apparatus for decoding a control parameter for controlling decoding of an image, the decoding apparatus comprising:
 a context control unit configured to determine a context for a current block in the image, from among a plurality of contexts; and   an arithmetic decoding unit configured to perform arithmetic decoding on a bitstream corresponding to the current block, using the determined context to obtain the control parameter for the current block,   wherein the context control unit is further configured to:   determine a signal type under which the control parameter for the current block is classified;   determine the context by using both of decoded control parameters for a left block and an upper block, when the signal type is a first type, the left block being a neighboring block to the left of the current block, and the upper block being a neighboring block on top of the current block; and   determine the context by using a predetermined fixed value, without using any decoded control parameters for the left block and the upper block, when the signal type is a second type different from first type,   wherein one of a split flag and a skip flag is classified under the first type, the split flag indicating whether or not the current block is partitioned into a plurality of blocks, and the skip flag indicating whether or not the current block is to be skipped, and   wherein a merge mode flag is classified under the second type, the merge mode flag indicating whether or not a merge mode is used for the current block.    
     
     
       4. A coding apparatus for coding a control parameter for controlling coding of an image, the coding apparatus comprising:
 a context control unit configured to determine a context for a current block in the image, from among a plurality of contexts; and   an arithmetic coding unit configured to perform arithmetic coding on the control parameter for the current block, using the determined context to generate a bitstream corresponding to the current block,   wherein the context control unit is further configured to:   determine a signal type under which the control parameter for the current block is classified;   determine the context by using both of coded control parameters for a left block and an upper block, when the signal type is a first type, the left block being a neighboring block to the left of the current block, and the upper block being a neighboring block on top of the current block; and   determine the context by using a predetermined fixed value, without using any coded control parameters for the left block and the upper block, when the signal type is a second type different from first type,   wherein one of a split flag and a skip flag is classified under the first type, the split flag indicating whether or not the current block is partitioned into a plurality of blocks, and the skip flag indicating whether or not the current block is to be skipped, and   wherein a merge mode flag is classified under the second type, the merge mode flag indicating whether or not a merge mode is used for the current block.