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DCT-Domain Inverse Motion Compensation (IMC)

w. h. 8x8. 8x8. DCT-Domain Inverse Motion Compensation (IMC). Extract the Prediction Block in the DCT-Domain Previous Algorithms Pre-compute Q ij [Chang & Messerschmitt, 93] Factorize Q ij [Merhav & Bhaskaran, 97] Approximate Q ij [Assuncao & Ghanbari, 98] Use the shared information in

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DCT-Domain Inverse Motion Compensation (IMC)

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  1. w h 8x8 8x8 DCT-Domain Inverse Motion Compensation (IMC) • Extract the Prediction Block in the DCT-Domain • Previous Algorithms • Pre-computeQij[Chang & Messerschmitt, 93] • Factorize Qij[Merhav & Bhaskaran, 97] • Approximate Qij[Assuncao & Ghanbari, 98] • Use the shared information in each macro-block [Song & Yeo, 00]

  2. Windowing Effect (in 1-D) x1(n) y(n)= x1(n) + x2(n) x2(n) X1(n) Y(n)= X1(n) + X2(n) X2(n)

  3. Local Bandwidth Constrained DCT Domain IMC • Neighboring Pixels Are Highly Correlated in Images DCT coefficients L1 = [5, 0, 1, 0, 0, 0, 0, 0] L2 = [3, 2, 0, 1, 0, 0, 0, 0] L3 = [x, x, x, x, 0, 0, 0, 0] x: element needs computation

  4. Experimental Results Time to convert a P frame to an I frame at bit rate of 4 Mb/s and 1 Mb/s (Unit: seconds) • Reduce the Computing Time by 25-30% at 4 Mb/s, 45-55% at 1Mb/s • Average PSNR Degradation is Less Than 0.3 dB • Similar results for B frames • Can Work on Top of Other Fast Methods S. Liu, and A. C. Bovik, “Local Bandwidth Constrained Fast Inverse Motion Compensation for DCT-Domain Video Transcoding ”, IEEE Trans. On Circuits and Systems for Video Technology, revised

  5. DCT-Domain IMC [Liu & Bovik, 01] [Song & Yeo, 00] [Chang & Messerschmitt, 93] [Liu & Bovik, 01] • [Merhav & Bhaskaran, 97] [Assuncao & Ghanbari, 98]

  6. Look-Up-Table (LUT) Based DCT Domain IMC • Model DCT Coefficients as Laplacian Distribution [Smoot & Rowe, 96] • The Value of is Estimated as 0.0284 • Let , Pre-compute the Results for Coefficients with • 800KB Memory Required • LUT Can Be Shared by Multi- ple Processes , , Probability Values of DCT AC coefficients

  7. Video sequence Chang’s method LUT based method P frame B frame P frame B frame Foreman 0.3137 0.4738 0.0931 0.1423 Coastguard 0.2374 0.3417 0.0912 0.1190 Mobile 0.3487 0.4136 0.1462 0.2000 Stefan 0.2057 0.3667 0.0780 0.1416 Experimental Results Table: The average time to convert one P or B frame to an I frame (Unit: Second) • Saves More Than 50% of Computing Time • Reduces Jerkiness S. Liu, and A. C. Bovik, “Look-Up-Table Based DCT Domain Inverse Motion Compensation ”, ICIP 2001

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