| 摘要 |
<p>PROBLEM TO BE SOLVED: To reduce amount of an arithmetic operation in comparison with definite calculation of a high frequency component by deciding whether or not the high frequency component is calculated based on a rate signal set in the quantization step in the case of conversion from a real space into a frequency space. SOLUTION: A compression coder 11 applies input image data to a DCT calculation circuit 12, in which a DCT coefficient is calculated. Quantization data being a result of arithmetic operation of an electronic circuit 13 are given to a variable length coding circuit 14, where the data are coded. The code is outputted from an output terminal and given to a code amount measurement circuit 15, in which a generated code amount per unit time is calculated. The value is converted into a rate signal and given to a DCT calculation circuit and quantization circuit 13. The quantization circuit 13 decides a quantization step used for succeeding data based on the rate signal to quantize the data. In this case, the DCT calculation circuit 12 decides whether or not the high frequency component of image data is to be calculated based on the rate signal.</p> |
