| 摘要 |
PURPOSE:To improve the quality of a transmission picture by comparing a transformation coefficient at a prescribed frequency area with plural reference values and deciding a threshold level depending on the level. CONSTITUTION:A transformation coefficient being an output of an orthogonal transformation section 300 is inputted to a threshold level control section 450 provided to a picture element supplement section 400 and the control section 450 compares the transformation coefficient at a prescribed frequency area with a preset 1st reference level. When the transformation coefficient larger than the 1st reference level is in existence, the threshold level is set to a 2nd reference level. When all the transformation coefficients for the prescribed area are smaller than the 1st reference level, the control section 450 sets the threshold level to a 3rd reference level larger than the 2nd threshold level. In this case, the orthogonal transformation section 300 obtains a difference of the picture data between frames for each block and applies orthogonal transformation to the difference data and outputs a transformation coefficient represented by a frequency component. Then the threshold level is set to a larger value to set forcibly the transformation coefficient to zero and outputted, then the quality of the transmission picture is improved. |
