Moving picture coding device, moving picture coding method, and moving picture coding program, and moving picture decoding device, moving picture decoding method, and moving picture decoding program

A moving picture decoding method of decoding a bitstream in which moving pictures are coded by partitioning a first block, which is obtained by partitioning each picture of the moving pictures into predetermined sizes, into one or a plurality of second blocks, the method comprising:

• a decoding step of extracting a differential quantization parameter of the second block by decoding the bitstream;
• a predictive quantization parameter deriving step of deriving a predictive quantization parameter of the second block using quantization parameters of a third block adjacent to the left of the second block and a fourth block adjacent to the top of the second block;
• and
• a quantization parameter generation step of generating a quantization parameter of the second block by adding the differential quantization parameter of the second block and the predictive quantization parameter of the second block, wherein
• in the predictive quantization parameter deriving step, the quantization parameter of the third block is set as a first quantization parameter when the third block is at a position not beyond a boundary of the first block, a quantization parameter of a fifth block decoded immediately before the second block in a decoding order is set as the first quantization parameter when the third block is at a position beyond the boundary of the first block so as to set the first quantization parameter having a non-zero value regardless of the position for the boundary of the first block, the quantization parameter of the fourth block is set as a second quantization parameter when the fourth block is at a position not beyond the boundary of the first block, the quantization parameter of the fifth block is set as the second quantization parameter when the fourth block is at a position beyond the boundary of the first block so as to set the second quantization parameter having a non-zero value regardless of the position for the boundary of the first block, and the predictive quantization parameter of the second block is derived using both the first and second quantization parameters regardless of the position of the third block or the fourth block, or both the third and fourth blocks, with respect to the boundary of the first block.

A recording medium having a moving picture decoding program for decoding a bitstream in which moving pictures are coded by partitioning a first block, which is obtained by partitioning each picture of the moving pictures into predetermined sizes, into one or a plurality of second blocks, the program causing a computer to execute:

• a decoding step of extracting a differential quantization parameter of the second block by decoding the bitstream;
• a predictive quantization parameter deriving step of deriving a predictive quantization parameter of the second block using quantization parameters of a third block adjacent to the left of the second block and a fourth block adjacent to the top of the second block;
• and
• a quantization parameter generation step of generating a quantization parameter of the second block by adding the differential quantization parameter of the second block and the predictive quantization parameter of the second block, wherein
• in the predictive quantization parameter deriving step, the quantization parameter of the third block is set as a first quantization parameter when the third block is at a position not beyond a boundary of the first block, a quantization parameter of a fifth block decoded immediately before the second block in a decoding order is set as the first quantization parameter when the third block is at a position beyond the boundary of the first block so as to set the first quantization parameter having a non-zero value regardless of the position for the boundary of the first block, the quantization parameter of the fourth block is set as a second quantization parameter when the fourth block is at a position not beyond the boundary of the first block, the quantization parameter of the fifth block is set as the second quantization parameter when the fourth block is at a position beyond the boundary of the first block so as to set the second quantization parameter having a non-zero value regardless of the position for the boundary of the first block, and the predictive quantization parameter of the second block is derived using both the first and second quantization parameters regardless of the position of the third block or the fourth block, or both the third and fourth blocks, with respect to the boundary of the first block.