Patent ID: 8902985
Filing Date: 2014-12-02
Classification: H04N

Abstract:
1. An image coding method of coding an original image, the image coding method comprising: partitioning the original image into a plurality of blocks; determining a coding condition for a current block that is one of the blocks each having a predetermined size; and coding the current block according to the determined coding condition, wherein the determining of the coding condition for the current block includes determining the coding condition for the current block, based on a spatial-activity value that is a value indicating complexity of the current block, the spatial-activity value becoming smaller as the current block becomes a flatter image, wherein the determining of the coding condition based on the spatial-activity value includes: calculating a first spatial-activity value indicating complexity of at least a part of regions of the current block, the first spatial-activity value increasing as the complexity increases and becoming smaller as the part of regions of the current block becomes a flatter image; comparing the calculated first spatial-activity value with a first predetermined threshold value; determining, as the coding condition for the current block, a first coding condition indicating that the current block is coded in units of a sub-block having a first partitioning size, when the first spatial-activity value is smaller than the first predetermined threshold value; and determining, as the coding condition for the current block, a second coding condition indicating that the current block is coded in units of a sub-block having a second partitioning size larger than the first partitioning size, when the first spatial-activity value is equal to or larger than the first predetermined threshold value, wherein the calculating of the first spatial-activity value includes: forming a plurality of small-block clusters each including at least a part of regions of the current block, based on an extended block including at least the current block; and calculating a small-block cluster spatial-activity value (i) that is a value indicating complexity of a corresponding one of the small-block clusters, and (ii) that becomes smaller as the corresponding small-block cluster becomes a flatter image, and calculating, as the first spatial-activity value, a lowest value among the calculated small-block cluster spatial-activity values, and wherein the extended block is larger than the current block and less than the size of a whole picture.