DCT-Domain Inverse Motion Compensation (IMC)

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DCT-Domain Inverse Motion Compensation (IMC)

• Extract the Prediction Block in the DCT-Domain
• Previous Algorithms
• Pre-compute Qij Chang Messerschmitt, 93
• Factorize Qij Merhav Bhaskaran, 97
• Approximate Qij Assuncao Ghanbari, 98
• Use the shared information in
• each macro-block Song Yeo, 00

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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)
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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
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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
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DCT-Domain IMC
Liu Bovik, 01
Song Yeo, 00
Chang Messerschmitt, 93
Liu Bovik, 01
Merhav Bhaskaran, 97
Assuncao Ghanbari, 98
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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
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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