| 摘要 |
PURPOSE: To enable efficient encoding by accurately estimating a quantization coefficient SF generating any positive error. CONSTITUTION: Converting processing at an image converting part 1, quantizing processing at a quantizing part 2 with quantizing width from a quantizing width estimating part 10, encoding processing at a variable length encoding part 3 and the amount of codes at a code amount calculating part 4 are repeatedly calculated. An inclination calculating part 8 calculates the inclination of an approximate straight line by selecting two sets of quantization coefficients and code amounts larger or smaller than the target quantization coefficient when the shape of a graph showing the logarithm of a quantization coefficient and the logarithm of a code amount is convex upward, and by selecting two sets of coefficients with the target amount in between when the graph is convex downward. A quantization width calculation part 9 calculates the quantization coefficient from the approximate straight line and sends the quantization width to the quantizing part 2. The approximate straight line becomes always made larger than the graph near the target quantization coefficient and the error of the code amount becomes always negative. |
