Patent ID: 7680346

Claim:
An image encoding method comprising: creating a predicted block corresponding to a current block to be encoded using a prediction unit; creating a residual block by estimating a difference between the current block and the predicted block using a subtraction unit; creating a transformed residual block and a transformed predicted block by transforming the residual block and the predicted block, respectively using a transform unit; using a minimum threshold block creating unit for obtaining a minimum threshold transform coefficient which allows a corresponding pixel included in the transformed predicted block to be visually noticeable, and creating a minimum threshold block comprising the minimum threshold transform coefficient; and using a quantization unit for determining an optimum quantization step which allows a maximum quantization error to be equal to or less than the minimum threshold transform coefficient with respect to a corresponding coefficient of the transformed residual block, and quantizing the corresponding coefficient of the transformed residual block based on the determined optimum quantization step.