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A practical Projection-Based Postprocessing of Block-Coded Images with Fast Convergence Rate

A practical Projection-Based Postprocessing of Block-Coded Images with Fast Convergence Rate. Yeonsik Jeong, Inkyeom Kim, and Hyunchul Kang. Blocking effect (1/2). Blocking effect is the problem of Block-Coded Image. Blocking effect (2/2). 5. 15. 3. 8. POCS(projection onto convex set).

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A practical Projection-Based Postprocessing of Block-Coded Images with Fast Convergence Rate

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  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. 5 15 3 8 POCS(projection onto convex set) • reduction blocking effect • SCS (smoothness constraint set)and QCS (quantization constraint set) 10

  5. -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 • 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 Decoded image DCT coefficient Quantization table QCS(1/3) QCS11 = [-416-16/2,-416+16/2] = [-424,-408]

  6. 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

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

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

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

  10. Rhv = variance of horizontally difference block / variance of vertically difference block Rvh = 1/Rhv Difference = Rhv - Rvh

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

  12. Four BS*BS are obtained(four types) • If is not uniquely determined • Maximum value in case of flat region • Minimum value in other region AQCS(Adaptive QCS)(4/5) • Basic idea：change energy before and after projection should be minimal

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

  14. Experimental Results(1/3)

  15. Experimental Results(2/3)

  16. Experimental Results(3/3)

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

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