Image decoding device, image encoding device, and method thereof

Abstract

A lossless decoding unit 52 takes quantization parameters of decoded blocks spatially or temporally adjacent to a block to be decoded, as selection candidates, and extracts, from stream information, difference information indicating difference as to a prediction quantization parameter selected from the selection candidates. A quantization parameter calculating unit 59 calculates, from the prediction quantization parameter and the difference information, a quantization parameter of the block to be decoded. Thus, decoding of the image can be performed correctly by calculating a quantization parameter equal to a quantization parameter used at the time of image encoding.

1 . An image encoding apparatus comprising:
 circuitry configured to:
 calculate, if a block adjacent to the left of a to-be-encoded block cannot be referenced and a block adjacent above the to-be-encoded block can be referenced, a prediction quantization parameter of the to-be-encoded block using a quantization parameter of the block adjacent above; 
 calculate, if the block adjacent to the left can be referenced and the block adjacent above cannot be referenced, the prediction quantization parameter of the to-be-encoded block using a quantization parameter of the block adjacent to the left; 
 generate difference information indicating a difference between the prediction quantization parameter and a quantization parameter set for the to-be-encoded block; and 
 generate a bit stream comprising the difference information. 
   
     
     
         2 . The image encoding apparatus according to  claim 1 , wherein
 the block is a coding unit, and the coding unit has a hierarchical structure.   
     
     
         3 . The image encoding apparatus according to  claim 2 , wherein
 the circuitry generates the bit stream by performing encoding processing using the quantization parameter set for the to-be-encoded block.   
     
     
         4 . The image encoding apparatus according to  claim 3 , wherein
 the circuitry generates difference information indicating a difference between an initial value of a quantization parameter for a slice and the set quantization parameter, in a case that no block can be referenced.   
     
     
         5 . The image encoding apparatus according to  claim 1 , wherein
 the circuitry generates the bit stream by performing encoding processing using the quantization parameter set for the to-be-encoded block.   
     
     
         6 . The image encoding apparatus according to  claim 5 , wherein
 the circuitry generates difference information indicating a difference between an initial value of a quantization parameter for a slice and the set quantization parameter, in a case that no block can be referenced.   
     
     
         7 . The image encoding apparatus according to  claim 1 , wherein
 the circuitry generates difference information indicating a difference between an initial value of a quantization parameter for a slice and the set quantization parameter, in a case that no block can be referenced.   
     
     
         8 . An image encoding method comprising:
 calculating, if a block adjacent to the left of a to-be-encoded block cannot be referenced and a block adjacent above the to-be-encoded block can be referenced, a prediction quantization parameter of the to-be-encoded block using a quantization parameter of the block adjacent above;   calculating, if the block adjacent to the left can be referenced and the block adjacent above cannot be referenced, the prediction quantization parameter of the to-be-encoded block using a quantization parameter of the block adjacent to the left;   generating difference information indicating a difference between the prediction quantization parameter and a quantization parameter set for the to-be-encoded block; and   generating a bit stream comprising the difference information.   
     
     
         9 . A non-transitory computer-readable medium having embodied thereon a program, which when executed by a computer causes the computer to execute a method, the method comprising:
 calculating, if a block adjacent to the left of a to-be-encoded block cannot be referenced and a block adjacent above the to-be-encoded block can be referenced, a prediction quantization parameter of the to-be-encoded block using a quantization parameter of the block adjacent above;   calculating, if the block adjacent to the left can be referenced and the block adjacent above cannot be referenced, the prediction quantization parameter of the to-be-encoded block using a quantization parameter of the block adjacent to the left;   generating difference information indicating a difference between the prediction quantization parameter and a quantization parameter set for the to-be-encoded block; and   generating a bit stream comprising the difference information.   
     
     
         10 . An image decoding apparatus comprising:
 circuitry configured to:
 obtain, when a block adjacent to the left of a current block cannot be referenced and a block adjacent above the current block can be referenced, a prediction quantization parameter derived from a quantization parameter of the block adjacent above; 
 obtain, when the block adjacent to the left can be referenced and the block adjacent above cannot be referenced, the prediction quantization parameter derived from a quantization parameter of the block adjacent to the left; 
 obtain, from bit stream information, a difference information indicating a difference between the obtained prediction quantization parameter and a quantization parameter of the current block; and 
 generate the quantization parameter of the current block, from the prediction quantization parameter and the difference information. 
   
     
     
         11 . The image decoding apparatus according to  claim 10 , wherein
 the block is a coding unit, and the coding unit has a hierarchical structure.   
     
     
         12 . The image decoding apparatus according to  claim 11 , wherein
 the circuitry decodes the bit stream by performing decoding processing.   
     
     
         13 . The image decoding apparatus according to  claim 12 , wherein
 the circuitry obtains difference information indicating a difference between an initial value of a quantization parameter for a slice and the quantization parameter of the current block, in a case that no block can be referenced.   
     
     
         14 . The image decoding apparatus according to  claim 10 , wherein
 the circuitry decodes the bit stream by performing decoding processing.   
     
     
         15 . The image decoding apparatus according to  claim 14 , wherein
 the circuitry obtains difference information indicating a difference between an initial value of a quantization parameter for a slice and the quantization parameter of the current block, in a case that no block can be referenced.   
     
     
         16 . The image decoding apparatus according to  claim 10 , wherein
 the circuitry obtains difference information indicating a difference between an initial value of a quantization parameter for a slice and the quantization parameter of the current block, in a case that no block can be referenced.   
     
     
         17 . An image decoding method comprising:
 obtaining, when a block adjacent to the left of a current block cannot be referenced and a block adjacent above the current block can be referenced, a prediction quantization parameter derived from a quantization parameter of the block adjacent above;   obtaining, when the block adjacent to the left can be referenced and the block adjacent above cannot be referenced, the prediction quantization parameter derived from a quantization parameter of the block adjacent to the left;   obtaining, from bit stream information, a difference information indicating a difference between the obtained prediction quantization parameter and a quantization parameter of the current block; and   generating the quantization parameter of the current block, from the prediction quantization parameter and the difference information.   
     
     
         18 . The image decoding method according to  claim 17 , wherein
 the block is a coding unit, and the coding unit has a hierarchical structure.   
     
     
         19 . The image decoding method according to  claim 18 , further comprising
 decoding the bit stream by performing decoding processing.   
     
     
         20 . The image decoding method according to  claim 19 , further comprising
 obtaining difference information indicating a difference between an initial value of a quantization parameter for a slice and the quantization parameter of the current block, in a case that no block can be referenced.   
     
     
         21 . The image decoding method according to  claim 17 , further comprising
 decoding the bit stream by performing decoding processing.   
     
     
         22 . The image decoding method according to  claim 21 , further comprising
 obtaining difference information indicating a difference between an initial value of a quantization parameter for a slice and the quantization parameter of the current block, in a case that no block can be referenced.   
     
     
         23 . The image decoding method according to  claim 17 , further comprising
 obtaining difference information indicating a difference between an initial value of a quantization parameter for a slice and the quantization parameter of the current block, in a case that no block can be referenced.   
     
     
         24 . A non-transitory computer-readable medium having embodied thereon a program, which when executed by a computer causes the computer to execute a method, the method comprising:
 obtaining, when a block adjacent to the left of a current block cannot be referenced and a block adjacent above the current block can be referenced, a prediction quantization parameter derived from a quantization parameter of the block adjacent above;   obtaining, when the block adjacent to the left can be referenced and the block adjacent above cannot be referenced, the prediction quantization parameter derived from a quantization parameter of the block adjacent to the left;   obtaining, from bit stream information, a difference information indicating a difference between the obtained prediction quantization parameter and a quantization parameter of the current block; and   generating the quantization parameter of the current block, from the prediction quantization parameter and the difference information.