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US 6,320,905 B1Granted
Postprocessing system for removing blocking artifacts in block-based codecs
AssigneeStream Machine Company
InventorKonstantinos Konstantinides
Life of this patent
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Abstract
Video signal post-processor de-blocks signal by processing block edges, particularly vertical and/or horizontal neighboring pixels. Depending on boundary condition, received signal is filtered using smoothing LPF function. Low-memory post-processor system neither requires DCT block characteristics nor blurs image edges close to block boundary.
Claims4
Method for processing digital video signal comprising steps of:
- receiving a digital video signal representing a digitally compressed video image comprising a plurality of pixels arranged horizontally and vertically in a two-dimensional array;
- determining a boundary condition in the received signal in a horizontal direction or a vertical direction, the boundary condition being determined in the digitally compressed video image according to a smoothness measurement associated with a plurality of pixels arranged consecutively in the horizontal or vertical direction;
- and
- modifying the received signal according to the determined boundary condition by applying a smoothing function to the received signal to generate a modified video signal;
- wherein the boundary condition in the horizontal direction is determined, such that the modified video signal is generated according substantially to the following:
- if (|d2−d3|<t1) then
- d′2=(d1+2 d2+d3)/4,
- d′3=(d2+2 d3+d4)/4,
- where d1 to d4 comprise a set of sequential pixel values in vertically neighboring image blocks represented in the processed video signal, and d′2 and d′3 comprise filtered values of d2 and d3 respectively, and t1 comprises an integer threshold for determining an edge presence between the pixel values d2 and d3.
6 more elements
Method for processing digital video signal comprising steps of:
- receiving a digital video signal representing a digitally compressed video image comprising a plurality of pixels arranged horizontally and vertically in a two-dimensional array;
- determining a boundary condition in the received signal in a horizontal direction or a vertical direction, the boundary condition being determined in the digitally compressed video image according to a smoothness measurement associated with a plurality of pixels arranged consecutively in the horizontal or vertical direction;
- and
- modifying the received signal according to the determined boundary condition by applying a smoothing function to the received signal to generate a modified video signal;
- wherein a default mode or a DC-offset mode is selected, thereby effectively achieving filtering across vertical block boundaries in the modified video signal;
- wherein the boundary condition in the vertical direction is determined, such that a default or DC-offset mode is selected, and the modified video signal is generated according substantially to the following:
- let f(x−y)=1, if |x−y|<=t2, and 0 otherwise, l et B = ∑ i = 1 9 f ( c i - c i + 1 )
- if (B>t3) then
- apply the DC-offset mode
- else
- apply the default mode,
- where f comprises a function having variables x and y, B comprises a variable value, t2 and t3 comprise threshold values, and ci and ci+1 comprise a set of sequential pixel values in horizontally-neighboring image blocks represented in the processed video signal;
- and
- wherein the default mode is applied according substantially to the following:
- let Ca=(c5+c6)/2;
- if(|c5−c6|<t1) then
- c′5=(c4+2c5+c6)/4,
- c′6=(C5+2c6+c7)/4;
- for i=5 and i=6
- if (c′i>ca) then
- c′i=ca,
- where ca comprises an average pixel value, c4 to c7 comprise a set of sequential pixel values in horizontally neighboring image blocks represented in the processed video signal, and c′5 and c′6 comprise filtered values of c5 and c6 respectively.
19 more elements
Method for processing digital video signal comprising steps of:
- receiving a digital video signal representing a digitally compressed video image comprising a plurality of pixels arranged horizontally and vertically in a two-dimensional array;
- determining a boundary condition in the received signal in a horizontal direction or a vertical direction, the boundary condition being determined in the digitally compressed video image according to a smoothness measurement associated with a plurality of pixels arranged consecutively in the horizontal or vertical direction;
- and
- modifying the received signal according to the determined boundary condition by applying a smoothing function to the received signal to generate a modified video signal;
- wherein a default mode or a DC-offset mode is selected, thereby effectively achieving filtering across vertical block boundaries in the modified video signal;
- wherein the boundary condition in the vertical direction is determined, such that a default or DC-offset mode is selected, and the modified video signal is generated according substantially to the following:
- let f(x−y)=1, if |x−y|<=t2, and 0 otherwise, l et B = ∑ i = 1 9 f ( c i - c i + 1 )
- if (B>t3) then apply the DC-offset mode
- else
- apply the default mode,
- where f comprises a function having variables x and y, B comprises a variable value, t2 and t3 comprise threshold values, and c1 and Ci+1 comprise a set of sequential pixel values in horizontally-neighboring image blocks represented in the processed video signal;
- wherein the DC-offset mode is applied according substantially to the following:
- for i=2 to i=9
- c′i=(ci−1+2ci+ci+1)/4,
- where c′i comprises a filtered value of ci value.
12 more elements
Dependencies are inferred from the claim text.