| 摘要 |
<p>PROBLEM TO BE SOLVED: To obtain a data encoder in which the encoding rate (compression rate) can be increased as the quantization scale is enlarged (image resolution is higher) as compared with prior art. SOLUTION: The data codec comprises means 1 for subjecting an input image signal to discrete cosine transformation to produce a plurality of discrete cosine transform coefficients, means 2 for encoding the DC component of the plurality of discrete cosine transform coefficients, means 4 for making a decision whether the absolute value of the AC component of the plurality of discrete cosine transform coefficients is smaller than a thresholdαor not if the code length becomes shorter when the AC component to be encoded is represented by a fixed length, means 5 for subjecting the AC component to fixed length encoding when a decision is made that the absolute value of the AC component is not smaller than the threshold valueα, and means 6 for subjecting the AC component to variable length encoding when a decision is made that the absolute value of the AC component is smaller than the threshold valueαor the AC component is subjected once to variable length encoding.</p> |
