1. A practical Projection-Based Postprocessing of Block-Coded Images with Fast Convergence Rate Yeonsik Jeong, Inkyeom Kim, and Hyunchul Kang

2. Blocking effect (1/2) Blocking effect is the problem of Block-Coded Image

3. Blocking effect (2/2)

4. POCS(projection onto convex set) reduction blocking effect SCS (smoothness constraint set)and QCS (quantization constraint set) 10155 38

5. 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 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 QCS 11 = [-416-16/2,-416+16/2] = [-424,-408]

6. QCS(2/3) QCS 11 = [-416-16/2,-416+16/2] = [-424,-408] d 11 = -425P QCS (d 11 ) = -424 d 11 = -400P QCS (d 11 ) = -408 d 11 = -420P QCS (d 11 ) = -420

7. QCS(3/3) Problem ： Over-blurring is unavoidable when iterationproceeds =>how to improve in this paper ： converge at fast rate

8. AQCS(Adaptive QCS)(1/5) Range from 0 to 1 Estimated form and its eight –neighbors in the same location of BDCT domain ~ ~

9. Block-Region Classification –For types ： ： flat region ： horizontal edge region ： vertical edge region ： mid-range region AQCS(Adaptive QCS)(2/5)

10. R hv = variance of horizontally difference block / variance of vertically difference block R vh = 1/R hv Difference = R hv - R vh

12. AQCS(Adaptive QCS)(3/5) Maximum DCT coefficient ~

13. 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 determined Maximum value in case of flat region Minimum value in other region

14. AQCS(Adaptive QCS)(5/5)

15. Experimental Results(1/3)

16. Experimental Results(2/3)

17. Experimental Results(3/3)

18. Conclusion Number of Iterations can be reduced,but Computation time is long => hardware