Patent ID: 8699563
Filing Date: 2014-04-15
Classification: H04N

Abstract:
1. An image coding apparatus comprising: a first coding unit that discretely selects quantization parameters of a first range to perform calculation of generated code amounts corresponding to the selected quantization parameters; a second coding unit that performs calculation of generated code amounts corresponding to quantization parameters of a second range which is narrower than the first range and is based on a temporary quantization parameter; and a code amount control unit that (a) decides the temporary quantization parameter corresponding to a target code amount by (1) calculating generated code amounts, corresponding to quantization parameters not selected by the first coding unit, through an interpolation process, and (2) comparing the generated code amounts corresponding to the selected quantization parameters and the generated code amounts calculated through the interpolation process with the target code amount, and (b) decides an optimal quantization parameter corresponding to the target code amount by comparing the generated code amounts calculated by the second coding unit with the target code amount, wherein the code amount control unit determines an interpolation method for each calculated generated code amount according to values of quantization parameters used for calculating the generated code amounts by the interpolation process, the interpolation methods include (a) a quadratic curve for quantization parameters, (b) a quadratic curve for average quantization parameters and (c) using variations in the generated code amounts according to the values of quantization parameters.