| 摘要 |
<p>PURPOSE:To suppress the deterioration of a picture quality caused by a quantization error and to raise the efficiency of quantization by setting an allowable quantization error every component expressing a color picture according to the estimated value of the component expressing the brightness of colors and adaptively selecting the quantization characteristic of a differential signal of each component according to the size of the allowable quantization error. CONSTITUTION:In case of quantizing a difference when a color signal changes, the allowable quantization errors deltaY', deltaRY' and deltaBY' of the respective parameters depend on a former value yi-1 and it is desirable that the absolute value of the difference is as large as possible. The minimum values of the allowable quantization errors are deltaY, deltaRY and deltaBY and they are decided with the former value yi-1. The allowable quantization error is decided with yi-1 and the value of alteration quantity. The non- linear quantization characteristic based on the allowable quantization error curve is decided, for example, by the intersecting point between a polygonal line which passes an origin, alternates between the allowable quantization error curve and a quadrature axis and intersects the quadrature axis with the angle of forty-five degrees and the allowable quantization curve. Thus the deterioration of the picture quality caused by the quantization error is not recognized and the compressibility of data can be raised.</p> |
