| 摘要 |
<p>PURPOSE:To thin a picture without using a means like a low-pass filter while avoiding the loop back noise at the time of decoding a picture encoded by discrete cosine transformation and linear quantization. CONSTITUTION:Quantization coefficients 11 are inputted to an inverse quantization circuit 1 and is multiplied by a quantization step size set in a quantization table 4 by the inverse quantization circuit 1, and the result is sent to a discrete cosine inverse transformation circuit 2. This quantization step size is obtained by substituting the high band part of the quantization table 4 with '0' by a mask processing means 5, and corresponding inverse quantization data becomes '0'. Data inversely transformed in accordance with a transformation formula is sent to a thinning circuit 3 and is subjected to such thinning that only one dot is outputted in each n-dot unit in the longitudinal direction as well as the lateral direction by an (n) designating signal, and a reduction picture signal is outputted. Consequently, the cost is reduced because means like a filter are not used but the mask processing of the quantization table is used.</p> |
