| 摘要 |
PURPOSE:To compress picture data with high compressibility without degrading the quality of source pictures by performing quantization by respectively different bit numbers and performing encoding for respective re-transformed coefficient picture data and the other respective coefficient picture data. CONSTITUTION:A small bit number is allocated to the picture data of a high frequency band provided with a lot of noise components and the large bit number is allocated to the picture data of a low frequency band provided with the information of a main object. Further, wavelet conversion is executed again to wavelet transformation coefficient signals WV1 and VW1 whose frequency bands are different in main and sub directions and separation to the coefficient signals of the low frequency band provided with the main object and the coefficient signals of the high frequency band provided with a lot of noise is performed. Then, for the coefficient signals of the respective frequency bands, the bit number at the time of the quantization is defined as 0 bit for the one of the high frequency band and as 1 bit for the one of the low frequency band. Thus, the picture quality is maintained by raising the bit number for the important part, the bit number is lowered for the unimportant part, the picture quality of the main part of the pictures is maintained as a whole and the compressibility is improved. |
