Signal adaptive filtering method, signal adaptive filter and computer readable medium for storing program therefor

A method of filtering ringing noise caused when decoding a block-based compressed image data, the method comprising the steps of:

• (x) performing a gradient operation on a block subjected to inverse quantization and inverse discrete cosine transform using predetermined one-dimensional horizontal and vertical gradient operators;
• (y) generating a binary edge map representing whether or not each pixel is an edge pixel, using an absolute value of a difference between a gradient-operated value of one pixel and a value of an adjacent pixel, and a Q value used as a dividend for quantizing the block;
• and
• (z) performing a filtering by applying a predetermined filter window to the generated binary edge map.

A signal adaptive filter capable of reducing blocking effect and ringing noise of image data when a frame is composed of a plurality of blocks of a predetermined size, comprising:

• a mode flag checking unit for checking a flag to determine whether or not the frame is an intraframe or an interframe when a bitstream image data is deconstructed for inverse quantization;
• an intra filtering information generator for generating blocking information for reducing the blocking effect and ringing information for reducing the ringing noise, from coefficients of predetermined pixels of upper and left boundary regions of the data block when the frame is determined as an intraframe by the mode flag checking unit;
• an inter filtering information generator for setting the blocking information and ringing information of a previous frame corresponding to a motion vector as blocking information and ringing information of a current frame if the frame is an interframe, and setting the ringing information to “1” if a residual signal of an inverse-quantized current block exists;
• and
• an adaptive filter for adaptively filtering the image data passed through an inverse quantizer and an inverse discrete cosine transformer according to the blocking information and the ringing information generated by the intra filtering information generator and the inter filtering information generator.

A computer readable medium having embodied thereon a computer program for a signal adaptive filtering capable of reducing blocking effect and ringing noise of image data when a frame is composed of a plurality of blocks of a predetermined size,

• wherein the signal adaptive filtering comprises the steps of:
• (a) generating blocking information for reducing the blocking effect and ringing information for reducing the ringing noise, from coefficients of predetermined pixels of upper and left boundary regions of the data block when a frame obtained by deconstructing a bitstream image data for inverse quantization is an intraframe;
• (b) setting the blocking information and ringing information of a previous frame corresponding to a motion vector as blocking information and ringing information of a current frame if the frame is an interframe, and setting the ringing information to “1” which represents the image data requiring filtering if a residual signal of the inverse-quantized current block exists;
• and
• (c) adaptively filtering the image data passed through the inverse quantization and inverse discrete cosine transform based on the block according to the generated blocking information and ringing information.

A computer readable medium having embodied thereon a computer program for a method of filtering ringing noise caused when decoding a block-based compressed image data,

• wherein the ringing noise filtering method comprises the steps of:
• (a) performing a gradient operation on the block subjected to inverse quantization and inverse discrete cosine transform using predetermined one-dimensional horizontal and vertical gradient operators;
• (b) generating a binary edge map representing whether or not each pixel is an edge pixel, using an absolute value of a difference between a gradient-operated value of one pixel and a value of an adjacent pixel, and a Q value used as a dividend for quantizing the block;
• and
• (c) performing a filtering by applying a predetermined filter window to the generated binary edge map.

A method for processing image data comprising:

• (a) inverse-quantizing the image data;
• (b) generating a flag information indicating whether the image data requires filtering based on the inverse-quantized image data;
• and
• (c) filtering the image data according to the generated flag information.