Patent ID: 8879638
Filing Date: 2014-11-04
Classification: H04N

Abstract:
1. An image coding apparatus, comprising: an evaluation value calculation part for dividing inputted uncompressed image data into a plurality of macroblocks and calculating an activity indicating the degree of dispersion of pixel values in each macroblock; a statistical value calculation part for specifying a plurality of surrounding macroblocks positioned around an object macroblock of which a quantization step value is to be determined and calculating a first statistical value of a plurality of surrounding activities corresponding to said plurality of surrounding macroblocks, respectively; an activity adjustment part for decreasing an activity of the object macroblock when the first statistical value is smaller than a predetermined threshold and said activity of said object macroblock is larger than the first statistical value; a correction factor determination part for determining a correction factor depending on said activity of said object macroblock based on a lookup table that specifies a distinct correction factor for each of a plurality of non-overlapping, predetermined ranges of adjustment values, which are based on said activity of said object macroblock; and a quantization step value determination part for correcting a reference quantization step value allocated to said object macroblock on the basis of said correction factor to determine a quantization step value to be used for quantizing said object macroblock.