Methods, Devices, and Computer Readable Mediums for Processing a Digital Picture

• US 20130004096A1
• Filed: 10/29/2010
• Published: 01/03/2013
• Est. Priority Date: 10/30/2009
• Status: Active Grant

• Current Assignee: Agency For Science Technology and Research
• Original Assignee: Agency For Science Technology and Research
• Inventors: Goh, Kwong Huang, Tham, Jo Yew, Lee, Wei Siong, Oo, Zaw Min
• Granted Patent: US 9,183,617 B2
• Time in Patent Office: Days
• US Class Current: 382/260
• CPC Class Codes: G06T 2207/10016 Video; Image sequence
• CPC Class Codes: G06T 2207/20012 Locally adaptive
• CPC Class Codes: G06T 2207/20021 Dividing image into blocks, subimages or windows
• CPC Class Codes: G06T 2207/20182 Noise reduction or smoothing in the temporal domain; Spatio-temporal filtering
• CPC Class Codes: G06T 5/70 Denoising; Smoothing
• 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 19/13 Adaptive entropy coding, e.g. adaptive variable length coding [AVLC] or context adaptive binary arithmetic coding [CABAC]
• CPC Class Codes: H04N 19/137 Motion inside a coding unit, e.g. average field, frame or block difference
• CPC Class Codes: H04N 19/139 Analysis of motion vectors, e.g. their magnitude, direction, variance or reliability
• 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 19/615 using motion compensated temporal filtering [MCTF]
• CPC Class Codes: H04N 19/63 using sub-band based transform, e.g. wavelets
• CPC Class Codes: H04N 19/80 Details of filtering operations specially adapted for video compression, e.g. for pixel interpolation H04N19/635, H04N19/86 take precedence
• CPC Class Codes: H04N 19/85 using pre-processing or post-processing specially adapted for video compression

Abstract

Embodiments provide a method for processing a digital picture, wherein the digital picture comprises a plurality of pixels. The method comprises dividing the digital picture into a plurality of blocks, each block comprising a plurality of pixels. The method further comprises determining a type of block for each block. The method further comprises associating each block with a filtering mode of a plurality of different filtering modes according to the type determined for the block. The method further comprises filtering each block using the associated filtering mode associated with the block.

Claims

1. A method for processing a digital picture, the digital picture comprising a plurality of pixels, the method comprising:

dividing the digital picture into a plurality of blocks, each block comprising a plurality of pixels;

determining a type of block for each block;

associating each block with a filtering mode of a plurality of different filtering modes according to the type determined for the block;

filtering each block using the associated filtering mode associated with the block.

2. The method according to claim 1, wherein the digital picture is a digital picture of a video sequence of digital pictures.

3. The method according to claim 1, wherein the type of a block is determined based on a characteristic value of the block.

4. The method according to claim 3, wherein the characteristic value is contrast value of the pixels in each block.

5. The method according to claim 3, wherein

a block is determined to be of an edge type if the characteristic value of the block is larger than a first threshold;

the block is determined to be of a texture type if the characteristic value of the block is between the first threshold and a second threshold, the second threshold being smaller than the first threshold; and

the block is determined to be of a homogeneous type if the characteristic value of the block is smaller than the second threshold.

6. The method according to claim 5, wherein

each block that is determined to be of an edge type is associated with an edge filtering mode;

each block that is determined to be of a texture type is associated with a texture filtering mode;

each block that is determined to be of a homogeneous type is associated with a homogeneous filtering mode.

7. The method according to claim 6, wherein filtering the blocks being associated with the texture filtering mode or homogeneous filtering mode comprises:

applying spatial filtering to the blocks being associated with the texture filtering mode or homogeneous filtering mode.

8. The method according to claim 7, wherein blocks being associated with the texture filtering mode are spatially filtered in a less degree compared with the blocks being associated with the homogeneous filtering mode.

9. The method according to claim 1, wherein filtering each block comprises:

applying motion compensated temporal filtering to each block.

10. The method according to claim 9, wherein applying motion compensated temporal filtering to each block comprises:

determining, for each pixel of the block, whether the pixel is similar to a corresponding pixel in a temporally preceding digital picture according to a first similarity criterion; and

applying motion compensated temporal filtering to the block for the pixels in the block which are determined to be similar with the corresponding pixels in the temporally preceding digital picture according to the first similarity criterion.

11. The method according to claim 10, wherein the determination for each pixel of the block of whether the pixel is similar to the corresponding pixel in the temporally preceding digital picture is based on a similarity check for the pixel with reference to the corresponding pixel in the temporally preceding digital picture.

12. The method according to claim 11, wherein the similarity check comprises:

producing a motion map of the digital picture by differencing pixels of the digital picture with corresponding pixels from the temporally preceding digital picture;

wherein the motion map has a plurality of motion map values, each motion map value being associated to a pixel of the digital picture;

wherein each motion map value is set to be a first number if the associated pixel is determined to be similar to the corresponding pixel in the temporally preceding digital picture according to a second similarity criterion, and each map value is set to be a second number if the associated pixel is determined to not be similar with the corresponding pixel in the temporally preceding digital picture according to the second similarity criterion;

determining, for each pixel, whether the pixel is similar with the corresponding pixel in the temporally preceding digital picture according to the first similarity criterion which is based on the motion map value associated with the pixel and motion map values associated with pixels adjacent to the pixel.

13. The method according to claim 12, wherein according to the first similarity criterion, for each pixel,

a sum of the motion map value associated with the pixel and motion map values associated with pixels adjacent to the pixel is compared with a third threshold, and

the pixel is determined to be similar to the corresponding pixel in the temporally preceding digital picture if the sum is larger than the first pre-determined value, and

the pixel is determined not to be similar to the corresponding pixel in the temporally preceding digital picture if the sum is smaller than the third threshold.

14. The method according to claim 12, wherein according to the second similarity criterion, for each pixel,

a difference value between the pixel and the corresponding pixel in the temporally preceding digital picture is determined, and

the pixel is determined to be similar to the corresponding pixel in the temporally preceding digital picture if the difference value is smaller than a fourth threshold, and

the pixel is determined not to be similar to the corresponding pixel in the temporally preceding digital picture if the difference value is larger than the fourth threshold.

15. A device for processing a digital picture, the digital picture comprising a plurality of pixels, the device comprising:

a dividing unit for dividing the digital picture into a plurality of blocks, each block comprising a plurality of pixels;

a determining unit for determining a type of block for each block;

an associating unit for associating each block with a filtering mode of a plurality of different filtering modes according to the type determined for the block;

a filtering unit for filtering each block using the associated filtering mode associated with the block.

16. A method for processing a sequence of digital pictures, comprising:

obtaining motion information based on a motion estimation between a first digital picture and a second digital picture of the sequence of digital pictures;

filtering a third digital picture of the sequence of digital pictures based on the motion information.

17. The method according to claim 16, wherein the first digital picture and the second digital picture are digital pictures preceding the third digital picture in the sequence of digital pictures.

18. The method according to claim 16, wherein the filtering is motion compensated temporal filtering.

19. The method according to claim 16 further comprising

encoding the third digital picture.

20. The method according to claim 16, further comprising

encoding the first digital picture and the second digital picture;

and

obtaining the motion information from the encoding process of the first digital picture and the second digital picture.

21. A device for processing a sequence of digital pictures, comprising:

an obtaining unit for obtaining motion information based on a motion estimation between a first digital picture and a second digital picture of the sequence of digital pictures;

a filtering unit for filtering a third digital picture of the sequence of digital pictures based on the motion information.

22. A computer readable medium having a program recorded thereon, wherein the program is executed to make a computer process a digital picture, the digital picture comprising a plurality of pixels, the computer readable medium comprising:

instructions for dividing the digital picture into a plurality of blocks, each block comprising a plurality of pixels;

instructions for determining a type of block for each block;

instructions for associating each block with a filtering mode of a plurality of different filtering modes according to the type determined for the block; and

instructions for filtering each block using the associated filtering mode associated with the block.

23. A computer readable medium having a program recorded thereon, wherein the program is executed to make a computer process a sequence of digital pictures, the computer readable medium comprising:

instructions for obtaining motion information based on a motion estimation between a first digital picture and a second digital picture of the sequence of digital pictures; and

instructions for filtering a third digital picture of the sequence of digital pictures based on the motion information.