| 摘要 |
<p>PURPOSE:To attain quantization according to an activity divided in class at every block. CONSTITUTION:Coefficient data in an AC component generated by DCT are fed to an activity detection circuit 8. Coefficient data with a comparative high frequency except an area generated when edge information is in existence are compared with a threshold level TH1. Number NH of coefficient data whose threshold level TH1 or over per one block is counted by a counter 27. The count NH is compared with threshold levels TH3, TH4, TH5 at comparator circuits 29-31 and the result of comparison is fed to a logic 33 and a code AT indicating the activity class is generated from the logic 33. Sets of quantization steps are adjusted according to the activity class and when the activity is high, quantization is made rough and when lower, the quantization is made fine.</p> |
