Patent ID: 8279923

Claim:
A video coding method of coding a video on a per predetermined block basis using one or more predetermined quantization control variables, said video coding method comprising: calculating a correlation degree indicating a correlation between an original block in a current original picture to be coded and a prediction block in a previous uncompressed picture, the correlation degree being calculated based on a difference between a sample value of the original block and a sample value of the prediction block, the correlation degree being greater as the original block and the prediction block are more similar to each other; changing a first predetermined quantization control variable to a second predetermined quantization control variable, so as to reduce a quantization step size when the correlation degree is greater than a predetermined threshold; and determining the quantization step size based on the second quantization control variable, and coding the original block based on the determined quantization step size using a predetermined image coding tool, wherein said changing includes: specifying, for the original block, a predetermined quantization parameter; determining an orthogonal transform size to be used for the original block; judging whether the orthogonal transform size is of a predetermined large size or a predetermined small size; and reducing a value of the predetermined quantization parameter by a predetermined first delta quantization parameter value, when the orthogonal transform size is judged to be the predetermined large size.