| 摘要 |
<p>PROBLEM TO BE SOLVED: To provide an image coder and an image decoder that can surely enhance a compression ratio without deteriorating image quality only through addition of a simple circuit. SOLUTION: A DCT control section 1 of a coding section 11 converts a received image into a DCT coefficient, and a quantization section 2 quantizs an output of the control section 1. A subtractor section 13 calculates a difference between the transform coefficient after the quantization outputted from the coding section 11 and a transform coefficient after quantization of a preceding block stored in a preceding block transform coefficient storage section 12. An absolute value sum calculation section 14 calculates the total sum of absolute values of the differences calculated by the subtractor section 13. Moreover, an absolute value sum calculation section 15 calculates the total sum of absolute values of the transform coefficients after quantization of a current block. A comparator section 16 compares the absolute sums calculated by the absolute value sum calculation sections 14, 15, and a selection section 17 selects the difference calculated by the subtractor section 13 or the transform coefficient after the quantization of the current block which has a smaller absolute sum according to the comparison result.</p> |
