Signal adaptive filtering method and signal adaptive filter for reducing blocking effect and ringing noise

摘要

A signal adaptive filtering method is disclosed for reducing a blocking effect and ringing noise of an image data.;A gradient of the image data is calculated for each pixel of the image data. Then, the gradient data of each pixel is compared with a global threshold value (T_g) which is determined based on a predetermined quantization step size (Q), and global edge map information of the pixel is generated. Meanwhile, the gradient data of each pixel is compared with a local threshold value (T_n) determined for each block having a predetermined size, and local edge map information of the pixel is generated. An OR operation is performed with respect to the global edge map information and the local edge map information to generate binary edge map information. Then, a predetermined sized filter window is applied to determine whether edges are present in the binary edge map information within the filter window. Afterwards, the image data pixel values of the corresponding filter window are filtered, pixel by pixel, by using predetermined first weighted values to generate a first new pixel value if it is determined that edges are not present. The image data pixel values within the corresponding filter window are filtered, pixel by pixel, by using predetermined second weighted values to generate a second new pixel value if it is determined that edges are present within the window. No filtering is performed if the pixel located at the center of the filter window represents an edge.