Motion picture encoding/decoding apparatus, adaptive deblocking filtering apparatus and filtering method for same, and recording medium

• US 9,596,485 B2
• Filed: 10/22/2009
• Issued: 03/14/2017
• Est. Priority Date: 10/27/2008
• Status: Active Grant

• Current Assignee: SK Telecom Co., Ltd.
• Original Assignee: SK Telecom Co., Ltd.
• Inventors: Kim, Hayoon, Choi, Yungho, Choe, Yoonsik, Kim, Yonggoo, Kim, Byongho, Ahn, Junhyuk
• Primary Examiner(s): Ustaris, Joseph
• Assistant Examiner(s): Navas, Jr., Edemio
• Application Number:
  US13/126,144
• Publication Number:
  US 20110200100A1
• Time in Patent Office: 2,700 Days
• Field of Search: None
• US Class Current: 1/1
• CPC Class Codes: H04N 19/117 Filters, e.g. for pre-processing or post-processing sub-band filter banks H04N19/635
• CPC Class Codes: H04N 19/14 Coding unit complexity, e.g. amount of activity or edge presence estimation H04N19/146 takes precedence
• CPC Class Codes: H04N 19/176 the region being a block, e.g. a macroblock
• CPC Class Codes: H04N 19/61 in combination with predictive coding
• CPC Class Codes: H04N 19/82 involving filtering within a prediction loop
• CPC Class Codes: H04N 19/86 involving reduction of coding artifacts, e.g. of blockiness

Abstract

A video encoding/decoding apparatus, an adaptive deblocking filtering apparatus and a filtering method for same, and a recording medium are disclosed. The filtering apparatus includes: a boundary strength determiner for determining strength of boundaries between subblocks of current block; a direction selector for selecting multiple directions preset with reference to the boundary sequentially; a filtering pixel selector for selecting pixels for filtering based on selected directions; a filtering determiner for determining whether to perform the filtering for the selected directions depending on relationships between pixel values of selected pixels; and a filtering unit for filtering the selected pixels in the selected directions depending on the determination of whether to perform filtering to apply pixel-wide deblocking filtering in a plurality of directions as well as in vertical and horizontal directions, thus effectively removing block distortions resulting from a diagonal discontinuity caused by edges in a plurality of diagonal directions.

Claims

1. A deblocking filtering apparatus comprising a microprocessor configured to:

determine a boundary among four boundaries corresponding to four sides of a current block, the determined boundary being located between the current block and a neighboring block adjacent to the current block;

determine a plurality of corresponding filtering directions for boundary pixels along and in the determined boundary of the current block by selecting, per each boundary pixel of the boundary pixels, each of the plurality of corresponding filtering directions from among a plurality of candidate directions based on each pixel value difference between relating pixels positioned, with respect to said each boundary pixel, in every direction of the plurality of candidate directions;

determine a filtering direction for the boundary of the current block, by selecting the determined filtering direction mostly selected from among the plurality of the determined corresponding filtering directions for said each boundary pixel of the boundary pixels, wherein each of the plurality of the determined corresponding filtering directions corresponds to said each corresponding filtering direction for said each boundary pixel of the boundary pixels;

select pixels for filtering based on the determined filtering direction with respect to said each boundary pixel of the boundary pixels;

determine whether to perform the filtering for the determined filtering direction depending on a first condition on a relationship between pixel values of the selected pixels for filtering, with respect to said each boundary pixel of the boundary pixels; and

perform the filtering with respect to the selected pixels for filtering in the determined filtering direction, depending on the determination of whether to perform the filtering, the filtering being performed, for all the boundary pixels, in the same determined filtering direction,

wherein said each pixel value difference is calculated corresponding to said each boundary pixel of the boundary pixels.

2. The deblocking filtering apparatus of claim 1, wherein the microprocessor is configured to

calculate said each pixel value difference based on

(i) an absolute value of a pixel value difference between two first pixels, of the relating pixels, facing each other with reference to the boundary,

(ii) an absolute value of a pixel value difference between a second pixel and a first pixel, of the relating pixels, both at one side with reference to the boundary,

(iii) an absolute value of a pixel value difference between a second pixel and a first pixel, of the relating pixels, at another side with reference to the boundary,

(iv) an absolute value of a pixel value difference between a third pixel and the second pixel, of the relating pixels, at the one side with reference to the boundary, and

(v) an absolute value of a pixel value difference between a third pixel and the second pixel, of the relating pixels, at the another side with reference to the boundary, and

select, among the plurality of candidate directions, a candidate direction with a smallest pixel value difference as said each corresponding filtering direction.

3. The deblocking filtering apparatus of claim 1, wherein the microprocessor is configured to perform the filtering in the determined filtering direction when the relationships between pixel values of the selected pixels satisfy the first condition that

(i) an absolute value of a pixel value difference between two first pixels, of the selected pixels, facing each other with reference to the boundary,

(ii) an absolute value of a pixel value difference between a second pixel and a first pixel, of the selected pixels, both at one side with reference to the boundary, and

(iii) an absolute value of a pixel value difference between a second pixel and a first pixel, of the selected pixels, at another side with reference to the boundary

are smaller than thresholds respectively preset.

4. The deblocking filtering apparatus of claim 1, wherein

when the determined filtering direction does not satisfy the first condition, the microprocessor is configured to

perform a check if a vertical direction of the boundary satisfies a second condition on a relationship between pixel values of the selected pixels for filtering with respect to the vertical direction, and

perform a filtering with respect to a vertical direction according to the check.

5. The deblocking filtering apparatus of claim 1, wherein the plurality of candidate directions include 45 degrees, 56.25 degrees, 67.5 degrees, 78.75 degrees, 90 degrees, 101.25 degrees, 112.5 degrees, 123.75 degrees, and 135 degrees with respect to a horizontal direction.

6. A deblocking filtering method comprising:

determining a boundary among four boundaries corresponding to four sides of a current block, the determined boundary being located between the current block and a neighboring block adjacent to the current block;

determining a plurality of corresponding filtering directions for boundary pixels along and in the determined boundary of the current block by selecting, per each boundary pixel of the boundary pixels, each of the plurality of corresponding filtering directions from among a plurality of candidate directions based on each pixel value difference between relating pixels positioned, with respect to said each boundary pixel, in every direction of the plurality of candidate directions;

determining a filtering direction for the boundary of the current block, by selecting the determined filtering direction mostly selected from among the plurality of the determined corresponding filtering directions for said each boundary pixel of the boundary pixels, wherein each of the plurality of the determined corresponding filtering directions corresponds to said each corresponding filtering direction for said each boundary pixel of the boundary pixels;

selecting pixels for filtering based on the determined filtering direction, with respect to said each boundary pixel of the boundary pixels;

determining whether to perform the filtering for the determined filtering direction depending on a first condition on a relationship between pixel values of the selected pixels for filtering, with respect to said each boundary pixel of the boundary pixels; and

performing the filtering with respect to the selected pixels for filtering in the determined filtering direction depending on the determination of whether to perform the filtering, the filtering being performed, for all the boundary pixels, in the same determined filtering direction,

wherein said each pixel value difference is calculated corresponding to said each boundary pixel of the boundary pixels.

7. The deblocking filtering method of claim 6, wherein the selecting the direction includes

calculating said each pixel value difference based on

(i) an absolute value of a pixel value difference between two first pixels, of the relating pixels, facing each other with reference to the boundary,

(ii) an absolute value of a pixel value difference between a second pixel and a first pixel, of the relating pixels, both at one side with reference to the boundary,

(iii) an absolute value of a pixel value difference between a second pixel and a first pixel, of the relating pixels, at another side with reference to the boundary,

(iv) an absolute value of a pixel value difference between a third pixel and the second pixel, of the relating pixels, at the one side with reference to the boundary, and

(v) an absolute value of a pixel value difference between a third pixel and the second pixel, of the relating pixels, at the another side with reference to the boundary, and

selecting a candidate direction with a smallest pixel value difference, among the plurality of candidate directions, as said each corresponding filtering direction.

8. The deblocking filtering method of claim 6, wherein the step of performing the determination of whether to perform the filtering includes

determining whether to perform the filtering depending on whether the relationships between pixel values of the selected pixels satisfy the first condition that

(i) an absolute value of a pixel value difference between two first pixels, of the selected pixels, facing each other with reference to the boundary,

(ii) an absolute value of a pixel value difference between a second pixel and a first pixel, of the selected pixels, both at one side with reference to the boundary, and

(iii) an absolute value of a pixel value difference between a second pixel and a first pixel, of the selected pixels, at another side with reference to the boundary are

smaller than thresholds respectively preset.

9. The deblocking filtering method of claim 6, wherein

when the determined filtering direction does not satisfy the first condition, the step of performing the determination of whether to perform the filtering includes

performing a check if a vertical direction of the boundary satisfies a second condition on a relationship between pixel values of the selected pixels for filtering with respect to the vertical direction

performing a filtering with respect to the vertical direction according to the check.

10. The deblocking filtering method of claim 6, wherein the plurality of candidate directions include 45 degrees, 56.25 degrees, 67.5 degrees, 78.75 degrees, 90 degrees, 101.25 degrees, 112.5 degrees, 123.75 degrees, and 135 degrees with respect to a horizontal direction.

11. A video encoding apparatus comprising a microprocessor configured to:

predict a current block of an image to generate a predicted block;

subtract the predicted block from the current block to generate a residual block;

perform a transform on the residual block into a frequency domain;

perform a quantization on the residual block after the transform;

encode the residual block after the quantization;

perform an inverse quantization on the residual block;

perform an inverse transform on the residual block after the inverse quantization into a residual block having pixel signals on time axis;

add the predicted block to the residual block after the inverse transform to perform a reconstruction of the current block;

perform a deblocking filtering of the current block after the reconstruction by

determining a boundary among four boundaries corresponding to four sides of the current block, the determined boundary being located between the current block and a neighboring block adjacent to the current block;

determining a plurality of corresponding filtering directions for boundary pixels along and in the determined boundary of the current block by selecting, per each boundary pixel of the boundary pixels, each of the plurality of corresponding filtering directions from among a plurality of candidate directions based on each pixel value difference between relating pixels positioned, with respect to said each boundary pixel, in every direction of the plurality of the candidate directions,

determining a filtering direction for the boundary of the current block, by selecting the determined filtering direction mostly selected from among the plurality of the determined corresponding filtering directions for said each boundary pixel of the boundary pixels, wherein each of the plurality of the determined corresponding filtering directions corresponds to said each corresponding filtering direction for said each boundary pixel of the boundary pixels,

selecting pixels for filtering based on the determined filtering direction, with respect to said each boundary pixel of the boundary pixels,

determining whether to perform the filtering for the determined filtering direction depending on a first condition on a relationship between pixel values of the selected pixels for filtering, with respect to said each pixel of the pixels in the boundary of the current block, and

performing the filtering with respect to the selected pixels for filtering in the determined filtering direction depending on the determination of whether to perform the filtering, the filtering being performed, for all the boundary pixels, in the same determined filtering direction,

wherein said each pixel value difference is calculated corresponding to said each boundary pixel of the boundary pixels.

12. A non-transitory computer readable medium storing a computer program comprising functions of:

determining a boundary among four boundaries corresponding to four sides of a current block, the determined boundary being located between the current block and a neighboring block adjacent to the current block;

determining a plurality of corresponding filtering directions for boundary pixels along and in the determined boundary of the current block by selecting, per each boundary pixel of the boundary pixels, each of the plurality of corresponding filtering directions from among a plurality of candidate directions based on each pixel value difference between relating pixels positioned, with respect to said each boundary pixel, in every direction of the plurality of candidate directions;

determining a filtering direction for the boundary of the current block, by selecting the determined filtering direction mostly selected from among the plurality of the determined corresponding filtering directions for said each boundary pixel of the boundary pixels, wherein each of the plurality of the determined corresponding filtering directions corresponds to said each corresponding filtering direction for said each boundary pixel of the boundary pixels;

selecting pixels for filtering based on the determined filtering direction, with respect to said each boundary pixel of the boundary pixels;

determining whether to perform the filtering for the determined filtering direction depending on a first condition on a relationship between pixel values of the selected pixels for filtering, with respect to said each boundary pixel of the boundary pixels; and

performing the filtering with respect to the selected pixels for filtering in the determined filtering direction depending on the determination of whether to perform the filtering, the filtering being performed, for all the boundary pixels, in the same determined filtering direction,

wherein said each pixel value difference is calculated corresponding to said each boundary pixel of the boundary pixels.