De-blocking filtering method of image data and de-blocking filter

• US 20080095244A1
• Filed: 10/17/2007
• Published: 04/24/2008
• Est. Priority Date: 10/20/2006
• Status: Active Grant

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: Kim, Han-Sang, Joo, Young-Hun, Choi, Kwang-Pyo
• Granted Patent: US 8,184,713 B2
• Time in Patent Office: Days
• US Class Current: 375/240.24
• CPC Class Codes: H04N 19/527 Global motion vector estimation

Abstract

Disclosed are a deblocking filtering method for image data and a deblocking filter. According to the deblocking filtering method for image data and the deblocking filter, when computation of BS values for each boundary based on one of horizontal and vertical directions from input image data is completed, it is possible to estimate BS values for each boundary based on a direction different from the currently selected direction by using the computed BS values. Further, deblocking filtering is performed based on corresponding directions according to the estimated values, so that the deblocking filtering can be completely performed with only a BS value of boundaries based on a selected one direction. Consequently, a BS value computation process necessarily required in a deblocking filtering process can be considerably reduced, and thus time required in the operation process of a deblocking filter can also be considerably reduced.

Claims

1. A method for deblocking filtering of image data divided into a plurality of macro blocks, the method comprising the steps of:

computing Boundary Strength (BS) values for boundaries based on a selected direction of the image data, wherein the direction is selected from the group consisting vertical and horizontal directions;

performing filtering based on the selected direction by using the computed BS values;

estimating BS values for boundaries based on the unselected direction by using the computed BS values; and

performing filtering based on the unselected direction by using the estimated BS values.

2. The method as claimed in claim 1, wherein the step of computing the BS values comprises the steps of:

dividing the macro blocks into a plurality of blocks;

sequentially selecting the macro blocks, and selecting one of boundaries based on the currently selected direction in boundaries of the currently selected macro block;

selecting boundary blocks based on the currently selected boundary;

determining if the boundary blocks are intra-coded blocks;

if the boundary blocks are the intra-coded blocks, primarily setting a BS value of the currently selected boundary to 4 or 3 according to whether the currently selected boundary corresponds to a macro block boundary;

if the boundary blocks are not the intra-coded blocks, comparing Coded Block Pattern (CBP) values of the boundary blocks;

if there is a difference as a result of the comparison, secondarily setting the BS value of the currently selected boundary to 2;

if there is no difference as a result of the coding, setting the BS value of the currently selected boundary to 1 or 0 according to predetermined conditions.

3. The method as claimed in claim 2, wherein, in the step of setting the BS value comprises the step of:

setting the BS value to 1 according to whether the boundary blocks have an equal reference picture, or whether a difference in motion vector values in a horizontal direction or a vertical direction of the boundary blocks is more than a predetermined value.

4. The method as claimed in claim 1, wherein the step of estimating the BS values comprises the steps of:

sequentially selecting the macro blocks, and selecting one of boundaries based on the currently unselected direction in boundaries of the selected macro block;

selecting secondary boundary blocks based on the selected boundary;

determining if the secondary boundary blocks are intra-coded blocks;

if the secondary boundary blocks are the intra-coded blocks, setting a BS value of the boundary based on the currently unselected direction of the secondary boundary blocks to 4 or 3 according to whether the selected boundary corresponds to a macro block boundary;

if the boundary blocks are not the intra-coded blocks, and if a previously computed BS value of the secondary boundary blocks is 2, setting the BS value of the boundary based on the currently unselected direction of the secondary boundary blocks to 2;

if the boundary blocks are not the intra-coded blocks, and if the previously computed BS value of the secondary boundary blocks is 1 or 0, setting the BS value of the boundary based on the currently unselected direction of the secondary boundary blocks to 0; and

5. A deblocking filter comprising:

a block divider for dividing received image data into macro blocks of a preset size, and selecting boundary blocks based on a boundary in a direction selected from the group consisting of;

a vertical direction and a horizontal direction;

a BS value computation unit for computing Boundary Strength (BS) values for boundaries between the boundary blocks based on the currently selected direction;

a BS value estimation unit for estimating BS values of boundary blocks based on a currently unselected direction by using the previously computed BS values of the boundary blocks;

a filtering unit for performing filtering for the boundaries in the vertical or horizontal direction according to a deblocking filtering method; and

a controller for;

selecting either the vertical direction or the horizontal direction, controlling the BS value computation unit so as to compute the BS values for the boundaries based on the currently selected direction,

controlling the BS value estimation unit so as to estimate the BS values for the boundaries based on the currently unselected direction by using the computed the BS values when the BS values for the boundaries based on all the currently unselected directions of the image data are computed; and

controlling the filtering unit so as to perform filtering in the horizontal or vertical direction by using the computed or estimated BS values.

6. The deblocking filter as claimed in claim 5, wherein the BS value computation unit computes the BS value based on the selected direction boundary according to:

are;

whether boundary blocks intra-coded blocks;

whether there is a difference in Coded Block Pattern (CBP) values when they are not the intra-coded blocks;

whether the boundary blocks have an equal reference picture;

whether a difference in motion vector values between the boundary blocks is more than a predetermined value; and

whether the boundary blocks correspond to a block boundary of the macro block when they are the intra-coded blocks.

7. The deblocking filter as claimed in claim 6, wherein the BS value computation unit:

sets a BS value of the currently selected boundary to 4 or 3 according to whether the selected boundary corresponds to the boundary of the macro block when they are the intra-coded blocks;

sets the BS value of the currently selected boundary to 2 if there is a difference in the boundary blocks as a result of comparing CBP values of the boundary blocks when they are not the intra-coded blocks, and

sets the BS value of the currently selected boundary to 1 or 0 according to whether the boundary blocks have the equal reference picture, or whether the difference in the motion vector values in the selected direction of the boundary blocks is more than the predetermined value when there is no difference in the boundary blocks as a result of the coding.

8. The deblocking filter as claimed in claim 5, wherein the BS value estimation unit estimates the BS value of the currently selected boundary in the unselected direction according to whether boundary blocks based on a boundary are blocks coded based on an intra mode, and whether the boundary to be estimated corresponds to a boundary surface of the macro block when they are not the intra-coded blocks.

9. The deblocking filter as claimed in claim 8, wherein the BS value estimation unit sequentially:

selects the macro blocks,

selects one of boundaries based on the currently unselected direction in boundaries of the selected macro block,

selects boundary blocks based on the selected boundary,

sets a BS value of the boundary to 4 or 3 according to whether the selected boundary corresponds to a macro block boundary when they are the intra-coded blocks,

sets the BS value of the boundary based on the currently unselected direction of the boundary blocks to 2 when they are the intra-coded blocks and when a previously computed BS value of the boundary blocks is 2, and

sets the BS value of the boundary based on the currently unselected direction of the boundary blocks to 0 when the previously computed BS value of the boundary blocks is 1 or 0.

10. A computer-program product providing instruction to a computer system for performing deblocking filtering of image data divided into a plurality of macro blocks, the computer system executing the steps of:

computing Boundary Strength (BS) values for boundaries based on a selected direction of the image data, wherein the direction is selected from the group consisting vertical and horizontal directions;

performing filtering based on the selected direction by using the computed BS values;

estimating BS values for boundaries based on the unselected direction by using the computed BS values; and

performing filtering based on the unselected direction by using the estimated BS values.

11. The computer product as claimed in claim 10, wherein the step of computing the BS values comprises the steps of:

dividing the macro blocks into a plurality of blocks;

sequentially selecting the macro blocks, and selecting one of boundaries based on the currently selected direction in boundaries of the currently selected macro block;

selecting boundary blocks based on the currently selected boundary;

determining if the boundary blocks are intra-coded blocks;

if the boundary blocks are the intra-coded blocks, primarily setting a BS value of the currently selected boundary to 4 or 3 according to whether the currently selected boundary corresponds to a macro block boundary;

if the boundary blocks are not the intra-coded blocks, comparing Coded Block Pattern (CBP) values of the boundary blocks;

if there is a difference as a result of the comparison, secondarily setting the BS value of the currently selected boundary to 2;

if there is no difference as a result of the coding, setting the BS value of the currently selected boundary to 1 or 0 according to predetermined conditions.

12. The computer product as claimed in claim 11, wherein, in the step of setting the BS value comprises the step of:

setting the BS value to 1 according to whether the boundary blocks have an equal reference picture, or whether a difference in motion vector values in a horizontal direction or a vertical direction of the boundary blocks is more than a predetermined value.

13. The computer product as claimed in claim 10, wherein the step of estimating the BS values comprises the steps of:

sequentially selecting the macro blocks, and selecting one of boundaries based on the currently unselected direction in boundaries of the selected macro block;

selecting secondary boundary blocks based on the selected boundary;

determining if the secondary boundary blocks are intra-coded blocks;

if the secondary boundary blocks are the intra-coded blocks, setting a BS value of the boundary based on the currently unselected direction of the secondary boundary blocks to 4 or 3 according to whether the selected boundary corresponds to a macro block boundary;

if the boundary blocks are not the intra-coded blocks, and if a previously computed BS value of the secondary boundary blocks is 2, setting the BS value of the boundary based on the currently unselected direction of the secondary boundary blocks to 2;

if the boundary blocks are not the intra-coded blocks, and if the previously computed BS value of the secondary boundary blocks is 1 or 0, setting the BS value of the boundary based on the currently unselected direction of the secondary boundary blocks to 0; and