Moving picture coding method for quantizing a plurality of pictures using a quantization step and a small quantization step having a size smaller than a size of the quantization step

A moving picture coding method for quantizing, per block, a plurality of pictures by using a quantization step and coding the quantized pictures, the plurality of pictures being temporally consecutive and included in a moving picture signal, said moving picture coding method comprising:

• deriving, based on the moving picture signal, a quantization step and a small quantization step having a size smaller than a size of the quantization step, the small quantization step being derived from the quantization step by (i) subtracting a first constant number from the quantization step or (ii) multiplying the quantization step by a second constant number;
• determining a position, within each of the plurality of pictures, of a first block group, the first block group including one or more blocks to be inter-coded per block, the position of the first block group within the picture cyclically shifting in a coding order direction in each of a predetermined number of pictures that are temporally consecutive among the plurality of pictures that are temporally consecutive;
• and
• quantizing, using a processor, the first block group by using the small quantization step and a second block group by using the quantization step, and coding the quantized first and second block groups, the first block group being at the position determined in said determining, the second block group including one or more blocks at a position within the picture other than the position determined in said determining, the second block group being to be inter-coded per block,
• wherein in said determining, the position of the first block group within the picture is determined such that the position of the first block group within the picture cyclically shifts in the coding order direction, and
• wherein the small quantization step, which has the size smaller than the size of the quantization step used to quantize the second block group to be inter-coded per block, is used to quantize the first block group including the one or more block to be inter-coded per block and whose position cyclically shifting in the coding order direction in each of the predetermined number of pictures that are temporally consecutive among the plurality of pictures that are temporally consecutive.

A non-transitory computer-readable recording medium for use in a computer, said recording medium having a computer program recorded thereon, the program being for quantizing, per block, a plurality of pictures by using a quantization step and coding the quantized pictures, the plurality of pictures being temporally consecutive and included in a moving picture signal, the program causing the computer to execute:

• deriving, based on the moving picture signal, a quantization step and a small quantization step having a size smaller than a size of the quantization step, the small quantization step being derived from the quantization step by (i) subtracting a first constant number from the quantization step or (ii) multiplying the quantization step by a second constant number;
• determining a position, within each of the plurality of pictures, of a first block group, the first block group including one or more blocks to be inter-coded per block, the position of the first block group within the picture cyclically shifting in a coding order direction in each of a predetermined number of pictures that are temporally consecutive among the plurality of pictures that are temporally consecutive;
• and
• quantizing the first block group by using the small quantization step and a second block group by using the quantization step, and coding the quantized first and second block groups, the first block group being at the position determined in said determining, the second block group including one or more blocks at a position within the picture other than the position determined in said determining, the second block group being to be inter-coded per block,
• wherein in said determining, the position of the first block group within the picture is determined such that the position of the first block group within the picture cyclically shifts in the coding order direction, and
• wherein the small quantization step, which has the size smaller than the size of the quantization step used to quantize the second block group to be inter-coded per block, is used to quantize the first block group including the one or more block to be inter-coded per block and whose position cyclically shifting in the coding order direction in each of the predetermined number of pictures that are temporally consecutive among the plurality of pictures that are temporally consecutive.

An integrated circuit which quantizes, per block, a plurality of pictures by using a quantization step and codes the quantized pictures, the plurality of pictures being temporally consecutive and included in a moving picture signal, said integrated circuit comprising:

• a quantization step deriving unit configured to derive, based on the moving picture signal, a quantization step and a small quantization step having a size smaller than a size of the quantization step, the small quantization step being derived from the quantization step by (i) subtracting a first constant number from the quantization step or (ii) multiplying the quantization step by a second constant number;
• a position determining unit configured to determine a position, within each of the plurality of pictures, of a first block group, the first block group including one or more blocks to be inter-coded per block, the position of the first block group within the picture cyclically shifting in a coding order direction in each of a predetermined number of pictures that are temporally consecutive among the plurality of pictures that are temporally consecutive;
• and
• a coding unit configured to quantize the first block group by using the small quantization step and a second block group by using the quantization step, and to code the quantized first and second block groups, the first block group being at the position determined by said position determining unit, the second block group including one or more blocks at a position within the picture other than the position determined by said position determining unit, the second block group being to be inter-coded per block,
• wherein said position determining unit is configured to determine the position of the first block group within the picture such that the position of the first block group within the picture cyclically shifts in the coding order direction, and
• wherein coding unit uses the small quantization step, which has the size smaller than the size of the quantization step used to quantize the second block group to be inter-coded per block, to quantize the first block group including the one or more block to be inter-coded per block and whose position cyclically shifting in the coding order direction in each of the predetermined number of pictures that are temporally consecutive among the plurality of pictures that are temporally consecutive.