Image signal processing apparatus utilizing a 2D Haar transform and adaptive selection of images based on a parameter such as a ratio of coefficients for reducing block distortion and method thereof

Claim 1

A method for processing a restored image signal having distortions obtained by decoding coded data by utilizing a two-dimensional inverse orthogonal transformation, said coded data obtained by coding an image signal by utilizing a two-dimensional orthogonal transformation, said method comprising the steps of: constructing a correction block having pixels of four coded blocks which are adjacent to one another and having a distortion; performing two-dimensional orthogonal transformation in units of said correction block by utilizing a Haar function so as to form a plurality of coefficients including higher-order side coefficients, three lower-order side coefficients and a dc coefficient; calculating a ratio of one of a power sum and absolute value sum of said three lower-order side coefficients to a corresponding one of a power sum and absolute value sum of the coefficients other than said dc coefficient and said three lower-order side coefficients; adding a correction value to said higher-order side coefficients in accordance with said three lower-order side coefficients after the coefficients other than said dc coefficient and said three lower-order side coefficients have been made zero so as to form a correction coefficient signal; performing two-dimensional inverse orthogonal transformation on said correction coefficient signal in units of said correction block by utilizing the Haar function so as to generate a smoothed image signal in which step-shaped distortions on the boundaries of said coded blocks have been smoothed; and combining together said restored image signal and said smoothed image signal in accordance with said ratio so as to obtain an image signal in which the distortions on the boundaries of the coded blocks have been substantially eliminated.

Claim 2

A method for processing a restored image signal having distortions obtained by decoding coded data by utilizing a two-dimensional inverse orthogonal transformation, said coded data obtained by coding an image signal by utilizing a two-dimensional orthogonal transformation, said method comprising the steps of: constructing a correction block having pixels of four coded blocks which are adjacent to one another and having a distortion; performing two-dimensional orthogonal transformation in units of said correction block by utilizing a Haar function so as to form a plurality of coefficients including higher-order side coefficients, three lower-order side coefficients and a dc coefficient; calculating a ratio of one of a power sum and absolute value sum of said three lower-order side coefficients to a corresponding one of a power sum and absolute value sum of the coefficients other than said dc coefficient and said three lower-order side coefficients; adding a correction value to said higher-order side coefficients in accordance with said three lower-order side coefficients after the coefficients other than said dc coefficient and said three lower-order side coefficients have been made zero so as to form a correction coefficient signal; performing two-dimensional inverse orthogonal transformation on said correction coefficient signal in units of said correction block by utilizing the Haar function so as to generate a smoothed image signal in which step-shaped distortions on the boundaries of said coded blocks have been smoothed; and combining together said restored image signal and said smoothed image signal in accordance with said ratio so as to obtain an image signal in which the distortions on the boundaries of the coded blocks have been substantially eliminated.

Claim 4

A method for processing a decoded image signal having a distortion obtained by decoding coded data by utilizing a two-dimensional inverse orthogonal transformation, said coded data obtained by coding an image signal by utilizing a two-dimensional orthogonal transformation, said method comprising the steps of: constructing at least one correction block each including a plurality of pixels from a plurality of coded blocks from said decoded image signal and having a distortion on at least one boundary therebetween, said coded blocks of each said correction block being adjacent to one another; performing two-dimensional orthogonal transformation of each said correction block by utilizing a Haar function so as to form a plurality of coefficients including higher-order side coefficients, lower-order side coefficients and a dc coefficient; calculating a ratio of one of a power sum and absolute value sum of a predetermined number of said lower-order side coefficients to a corresponding one of a power sum and absolute value sum of said higher-order side coefficients; adding a correction value to said higher-order side coefficients in accordance with said predetermined number of said lower-order side coefficients after said higher-order side coefficients have been set to zero so as to form a correction coefficient signal for each said correction block; performing two-dimensional inverse orthogonal transformation on the correction coefficient signal of each said correction block by utilizing the Haar function so as to generate a smoothed image signal in which said distortion on said at least one boundary of said coded blocks has been smoothed; and combining said decoded image signal and said smoothed image signal in accordance with said ratio so as to obtain an image signal in which said distortion on said at least one boundary of the coded blocks has been substantially eliminated.

Claim 5

A method for processing a decoded image signal having a distortion obtained by decoding coded data by utilizing a two-dimensional inverse orthogonal transformation, said coded data obtained by coding an image signal by utilizing a two-dimensional orthogonal transformation, said method comprising the steps of: constructing at least one correction block each including a plurality of pixels from a plurality of coded blocks from said decoded image signal and having a distortion on at least one boundary therebetween, said coded blocks of each said correction block being adjacent to one another; performing two-dimensional orthogonal transformation of each said correction block by utilizing a Haar function so as to form a plurality of coefficients including higher-order side coefficients, lower-order side coefficients and a dc coefficient; calculating a ratio of one of a power sum and absolute value sum of a predetermined number of said lower-order side coefficients to a corresponding one of a power sum and absolute value sum of said higher-order side coefficients; adding a correction value to said higher-order side coefficients in accordance with said predetermined number of said lower-order side coefficients after said higher-order side coefficients have been set to zero so as to form a correction coefficient signal for each said correction block; performing two-dimensional inverse orthogonal transformation on the correction coefficient signal of each said correction block by utilizing the Haar function so as to generate a smoothed image signal in which said distortion on said at least one boundary of said coded blocks has been smoothed; and combining said decoded image signal and said smoothed image signal in accordance with said ratio so as to obtain an image signal in which said distortion on said at least one boundary of the coded blocks has been substantially eliminated.

Claim 8

An apparatus for processing a decoded image signal having a distortion obtained by decoding coded data by utilizing a two-dimensional inverse orthogonal transformation, said coded data obtained by coding an image signal by utilizing a two-dimensional orthogonal transformation, said apparatus comprising: means for constructing at least one correction block each including a plurality of pixels from a plurality of coded blocks from said decoded image signal and having a distortion on at least one boundary therebetween, said coded blocks of each said correction block being adjacent to one another; means for performing two-dimensional orthogonal transformation of each said correction block by utilizing a Haar function so as to form a plurality of coefficients including higher-order side coefficients, lower-order side coefficients and a dc coefficient; means for calculating a ratio of one of a power sum and absolute value sum of a predetermined number of said lower-order side coefficients to a corresponding one of a power sum and absolute value sum of said higher-order side coefficients; means for setting said higher-order side coefficients to zero and for determining respective correction values in accordance with said predetermined number of said lower-order side coefficients and for respectively adding said correction values to said higher-order side coefficients so as to form a correction coefficient signal for each said correction block; means for performing two-dimensional inverse orthogonal transformation on the correction coefficient signal of each said correction block by utilizing the Haar function so as to generate a smoothed image signal in which said distortion on said at least one boundary of said coded blocks has been smoothed; and means for combining said decoded image signal and said smoothed image signal in accordance with said ratio so as to obtain an image signal in which said distortion on said at least one boundary of the coded blocks has been substantially eliminated.

Claim 9

An apparatus for processing a decoded image signal having a distortion obtained by decoding coded data by utilizing a two-dimensional inverse orthogonal transformation, said coded data obtained by coding an image signal by utilizing a two-dimensional orthogonal transformation, said apparatus comprising: means for constructing at least one correction block each including a plurality of pixels from a plurality of coded blocks from said decoded image signal and having a distortion on at least one boundary therebetween, said coded blocks of each said correction block being adjacent to one another; means for performing two-dimensional orthogonal transformation of each said correction block by utilizing a Haar function so as to form a plurality of coefficients including higher-order side coefficients, lower-order side coefficients and a dc coefficient; means for calculating a ratio of one of a power sum and absolute value sum of a predetermined number of said lower-order side coefficients to a corresponding one of a power sum and absolute value sum of said higher-order side coefficients; means for setting said higher-order side coefficients to zero and for determining respective correction values in accordance with said predetermined number of said lower-order side coefficients and for respectively adding said correction values to said higher-order side coefficients so as to form a correction coefficient signal for each said correction block; means for performing two-dimensional inverse orthogonal transformation on the correction coefficient signal of each said correction block by utilizing the Haar function so as to generate a smoothed image signal in which said distortion on said at least one boundary of said coded blocks has been smoothed; and means for combining said decoded image signal and said smoothed image signal in accordance with said ratio so as to obtain an image signal in which said distortion on said at least one boundary of the coded blocks has been substantially eliminated.