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 and decoding apparatus comprising:
 an image coding apparatus using arithmetic coding; and   an image decoding apparatus using arithmetic decoding,   wherein the image coding apparatus includes:   a binarization unit configured to binarize a first control parameter of a first current block to generate a first binary sequence;   a first context control unit configured to determine a first context for use in the first current block, from among a plurality of first contexts; and   an arithmetic coding unit configured to perform arithmetic coding on the first binary sequence using the determined first context to generate a first bit sequence,   wherein the first context control unit is configured to:   determine a first signal type of the first control parameter of the first current block;   determine the first context under a first condition that coded first control parameters of neighboring blocks of the first current block are used, when the first signal type is a first type, the neighboring blocks being a first left block and a first upper block of the first current block; and   determine the first context under a second condition that a predetermined fixed value is used and the coded first control parameters of the first left block and the first upper block are not used, when the first 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 first current block is partitioned into a plurality of blocks and (ii) a flag indicating whether or not the first current block is to be skipped, and   the second type is a flag indicating whether or not a merge mode is used for the first current block, and   wherein the image decoding apparatus includes:   a second context control unit configured to determine a second context for use in a second current block, from among a plurality of second contexts;   an arithmetic decoding unit configured to perform arithmetic decoding on a second bit sequence corresponding to the second current block, using the determined second context to decode a second binary sequence, the second bit sequence being obtained by performing arithmetic coding on a second control parameter of the second current block; and   an inverse binarization unit configured to inversely binarize the second binary sequence to decode the second control parameter of the second current block,   wherein the second context control unit is configured to:   determine a second signal type of the second control parameter of the second current block;   determine the second context under a third condition that decoded second control parameters of neighboring blocks of the second current block are used, when the second signal type is a third type, the neighboring blocks being a second left block and a second upper block of the second current block; and   determine the second context under a fourth condition that a predetermined fixed value is used and the decoded second control parameters of the second left block and the second upper block are not used, when the second signal type is a fourth type different from the third type,   wherein the third type is one of (i) a flag indicating whether or not the second current block is partitioned into a plurality of blocks and (ii) a flag indicating whether or not the second current block is to be skipped, and   the fourth type is a flag indicating whether or not a merge mode is used for the second current block.