A practical Projection-Based Postprocessing of Block-Coded Images with

Fast Convergence RateYeonsik Jeong, Inkyeom Kim, and Hyunch

ul Kang

Blocking effect (1/2)

• Blocking effect is the problem of Block-Coded Image

Blocking effect (2/2)

POCS(projection onto convex set)

• reduction blocking effect

• SCS (smoothness constraint set)and QCS (quantization constraint set)

10 155

3 8

QCS(1/3)

Decoded image DCT coefficient

-416 -33 -60 32 48 0 0 0

12 -24 -56 0 0 0 0 0

-42 13 80 -24 -40 0 0 0

-56 17 44 -29 0 0 0 0

18 0 0 0 0 0 0 0

0 0 0 0 0 0 0 0

0 0 0 0 0 0 0 0

0 0 0 0 0 0 0 0

16 11 10 16 24 40 51 61

12 12 14 19 26 58 60 55

14 13 16 24 40 57 69 56

14 17 22 29 51 87 80 62

18 22 37 56 68 109 103 77

24 35 55 64 81 104 113 92

49 64 78 87 103 121 120 101

72 92 95 98 112 100 103 99 Quantization table

QCS11 = [-416-16/2,-416+16/2] = [-424,-408]

QCS(2/3)

QCS11 = [-416-16/2,-416+16/2] = [-424,-408]

d11 = -425 PQCS(d11) = -424

d11 = -400 PQCS(d11) = -408

d11 = -420 PQCS(d11) = -420

QCS(3/3)

• Problem ： Over-blurring is unavoidable when iteration proceeds

=>how to improve in this paper ： converge at fast rate

AQCS(Adaptive QCS)(1/5)

Range from 0 to 1

Estimated form and its eight –neighbors in the same location of BDCT domain

~

~

• Block-Region Classification– For types ：

• ： flat region

• ： horizontal edge region

• ： vertical edge region

• ： mid-range region

AQCS(Adaptive QCS)(2/5)

Rhv = variance of horizontally difference block / variance of vertically difference block

Rvh = 1/Rhv

Difference = Rhv - Rvh

AQCS(Adaptive QCS)(3/5)

Maximum DCT coefficient

~

AQCS(Adaptive QCS)(4/5)

• Basic idea ： change energy before and after projection should be minimal

•Four BS*BS are obtained(four types)

•If is not uniquely determinedMaximum value in case of flat regionMinimum value in other region

AQCS(Adaptive QCS)(5/5)

Experimental Results(1/3)

Experimental Results(2/3)

Experimental Results(3/3)

Conclusion

• Number of Iterations can be reduced ,but Computation time is long => hardware