| 摘要 |
<p>PURPOSE:To encode a picture with a coding characteristic optimum to an entire pattern and to attain high speed processing. CONSTITUTION:An address control circuit 22 reads block data being 1/4 of a picture from a frame memory 21 prior to coding, the data are subject to DCT processing and the result is given to a quantization circuit 26. The quantization circuit 26 quantizes the data based on a quantization value based on a scale factor alpha. A coding circuit 31 applies Huffman coding to a quantization output and outputs the result and a code quantity calculation circuit 36 multiplies 4 with a code quantity of the Huffman code to estimate the total code quantity. An a calculation circuit 37 revises the scale factor a based on the estimate value and the quantization circuit 26 implements quantization for plural number of times by a different quantization value. The alpha calculation circuit 37 obtains an optimum scale factor alphaT from a code quantity of plural Huffman codes and an object code quantity and uses the factor for the substantial coding. Block data being part of the picture are read to estimate the code quantity and the code quantity is estimated in a short time.</p> |
