| 摘要 |
<p>PROBLEM TO BE SOLVED: To suppress the deterioration of picture quality on a visual characteristic to the utmost and to transmit only password information. SOLUTION: A quantization controller 12 sets quantization on a block whose deterioration in the visual characteristic is easily distinguished to be fine and sets the quantization of a block whose deterioration is not easily distinguished to be rough in accordance with the difficulty of picture quality, which is operated in a picture quality difficulty detector 15. A quantization parameter is decided at every block. In an area designation unit 13, the block is judged in such a way that deterioration on the visual characteristic is not easily distinguished when the quantization parameter exceeds a prescribed value, the numeric value of a fixed area in the high frequency of a quantization result is substituted for '0' and an input conversion coefficients are outputted for the respective blocks. Output password information of a password generator 14 is added to the high frequency area of quantization data in an adder 16, it is supplied to a variable length encoder 4 and it is encoded into a variable length code.</p> |
