| 摘要 |
PURPOSE:To prevent the change of picture quality caused by factors other than the change of the image contents in moving image compressing/coding. CONSTITUTION:The input moving image data are converted by a DCT converting part 100 and written into a frame memory 14 and also inputted to an AC component adder 16 which calculates a high frequency component. A quantization control part 50 selects approximately optimum quantization characteristics based on the sum of the target code value and the AC component, and a quantizer 200 quantizes a DCT coefficient. This quantized coefficient is coded by a variable length coder 300, and this coding data is written in a buffer memory BM 40. Meanwhile the 2nd quantization characteristic decided by the difference between the code value of the coding data and the target code value is selected. Then the DCT coefficient undergoes again the quantization and the variable length coding and is stored in a BM 42. Then the coding data closer to the target code value is used as the compression data out of both coding data stored in the BM 40 and the BM 42 in regard of the frame images. |
