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. An image coding apparatus using arithmetic coding, the apparatus comprising:
 a binarization unit configured to binarize a control parameter of a current block to generate a binary sequence;   a context control unit configured to determine a context for use in the current block, from among a plurality of contexts; and   an arithmetic coding unit configured to perform arithmetic coding on the binary sequence using the determined context to generate a bit sequence,   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 coded 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 coded 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.