| 摘要 |
<p>PURPOSE:To improve the picture quality by decreasing a threshold level of threshold level processing so as to preserve a high frequency component of a spatial frequency when an area including a character or complicated contour is coded. CONSTITUTION:The coder is provided with a discrete cosine transformation section 1, a threshold level processing section 2, a quantization section 3, a variable length coding section 4, a transmission buffer section 5, an area discrimination section 10 and a threshold level setting section 131. Then a specific threshold level is adopted for a block including a character or complicated contour or a block not including it so as to preserve the high frequency component of the spatial frequency in the block including the character or complicated contour. Thus, even to a picture in mixture with a character and a natural picture, the local picture quality deterioration in the character area is prevented.</p> |
