| CPC H04N 19/119 (2014.11) [H04N 19/154 (2014.11); H04N 19/176 (2014.11); H04N 19/86 (2014.11)] | 20 Claims |
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1. A method for partitioning a block of an image to reduce quantization artifacts, comprising:
estimating an expected entropy of the block, wherein estimating the expected entropy comprises:
determining respective Laplacians for pixels of the block, wherein determining the respective Laplacians for the pixels of the block comprises:
for a pixel in a row and a column of the block, subtracting from the pixel a first value that is a first function of a first average of all pixels of the row and subtracting from the pixel a second value that is a second function of a second average of all pixels of the column;
partitioning the block into sub-blocks;
calculating respective amounts of visual masking for the sub-blocks, wherein a respective amount of visual masking for a respective sub-block is indicative of how visible an artifact resulting from inverse transformation is in the respective sub-block;
selecting, as a visual masking characteristic of the block, a highest visual masking value of the respective amounts of visual masking for the sub-blocks;
combining the visual masking characteristic of the block and the expected entropy of the block to obtain a splitting indicator value, wherein the combining comprises using a linear model or multiplying the visual masking characteristic and the expected entropy of the block; and
determining whether to split the block based on the splitting indicator value.
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