| 摘要 |
PURPOSE: To further reduce a transmission bit rate without the loss of picture quality by changing finely or coarsely the quantity of quantization under the control of coding control means when a data block is related with the background of scene. CONSTITUTION: A preprocessing unit 1 compares two continuous data in the sequence of data blocks. When these data are equal as a result of comparison and another system parameter is higher than a scheduled threshold value, a circuit b1 and a coding control means 3 regard these data as the 'background' and operate a quantizer 404 so as to set these 'representative' block data to fine quantization and as long as the 'background' data are not changed, the other block data are set to coarse quantization. When the compared result shows non-coincidence, on the other hand, the preprocessing unit 1 sets a background index to an initial value. As a result, the image including 'background' is processed at the low transmission bit rate but the picture quality is not lowered. |
