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Fast Lossless Multi-Resolution Motion Estimation for Scalable Wavelet Video Coding. Yu Liu and King Ngi Ngan Department of Electronic Engineering The Chinese University of Hong Kong ISCAS2006, May 21-24, Island of Kos, Greece. Outline. Introduction Background Proposed Algorithm - PowerPoint PPT Presentation
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Fast Lossless Multi-Resolution Motion EstimationFast Lossless Multi-Resolution Motion Estimation for Scalable Wavelet Video Coding for Scalable Wavelet Video Coding
Yu Liu and King Ngi NganYu Liu and King Ngi Ngan
Department of Electronic EngineeringDepartment of Electronic EngineeringThe Chinese University of Hong KongThe Chinese University of Hong Kong
ISCAS2006, May 21-24, Island of Kos, GreeceISCAS2006, May 21-24, Island of Kos, Greece
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OutlineOutline
IntroductionIntroduction BackgroundBackground Proposed AlgorithmProposed Algorithm Experimental ResultsExperimental Results ConclusionConclusion
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IntroductionIntroduction
• Motion Estimation in Critically-Sampled Wavelet Domain• Pro: basically free form the blocking effects• Con: inefficient in high bands
• Motion Estimation in Shift-Invariant Wavelet Domain• Pro: perform ME more precisely and efficiently• Con: computational complexity
e.g. low-band-shift (LBS) and complete-to-overcomplete DWT (CODWT)
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BackgroundBackground
Motion Estimation in Shift-Invariant Wavelet Domain (1)Motion Estimation in Shift-Invariant Wavelet Domain (1)
• Two Level Shift-Invariant Wavelet Decomposition by using Low-Band-Shift (LBS) or Complete-to-Overcomplete DWT (CODWT)
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BackgroundBackground
Motion Estimation in Shift-Invariant Wavelet Domain (2)Motion Estimation in Shift-Invariant Wavelet Domain (2)
• Generation of Wavelet BlocksGeneration of Wavelet Blocks
jifjiS pkltpklt ,),( ,,,,,,
• The coefficient of the pth wavelet block of current frame t can be represented by
• The v-pixel-shifted or {dx,dy}-pixel-shifted coefficient of the pth wavelet block of reference frame t’ can be represented by
llllpkltvpklt dyjdxidydxfjiS 2/,2/,2%,2%),( ,,,',,,'
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BackgroundBackground
Motion Estimation in Shift-Invariant Wavelet Domain (3)Motion Estimation in Shift-Invariant Wavelet Domain (3)
• The sum of absolute difference (SAD) of the pth wavelet block for the motion vector v is computed as follows:
• The optimum motion vector v ∗ of the pth wavelet block, which has minimum displacement error, is given by:
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BackgroundBackground
Partial Distortion EliminationPartial Distortion Elimination
•Partial Distortion Elimination (PDE) is a fast algorithm which has identical quality as that of FSA.
•The partial SAD (PSAD) is used to eliminate impossible candidates before the complete calculation of the SAD:
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Proposed AlgorithmProposed Algorithm
Wavelet Matching Error CharacteristicWavelet Matching Error Characteristic
• then we assume that this matching order will be generally effective for all of the candidate vectors in the search window.
• Therefore, to fulfill the above objective, we use ep(i, j) to predict the matching error.
• To improve the computational saving of PDE, if the expected values of the matching error dp+v(i, j) in the search window w fulfills the following criterion:
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Proposed AlgorithmProposed Algorithm
Wavelet Matching Error CharacteristicWavelet Matching Error Characteristic
To obtain the predicted matching error To obtain the predicted matching error eepp(i, j)(i, j), solve this equation, solve this equation
We finally can obtain an approximate solution of Eq. (6):We finally can obtain an approximate solution of Eq. (6):
Larger wavelet coefficientLarger wavelet coefficient magnitude in the current magnitude in the current wavelet block tends to produce larger matching errorwavelet block tends to produce larger matching error
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Proposed AlgorithmProposed Algorithm
MR-WMEC-PDEMR-WMEC-PDE
Three key factors which affect the performance of PDEThree key factors which affect the performance of PDE
• the Searching Orderthe Searching Order in which the wavelet blocks are tested during the searching phase.in which the wavelet blocks are tested during the searching phase.
• the Matching Orderthe Matching Order in which the coefficients within a wavelet block are picked up to in which the coefficients within a wavelet block are picked up to
compute the SAD.compute the SAD.
• the Comparison Intervalthe Comparison Interval in which comparison between PSAD and SADmin is performed.in which comparison between PSAD and SADmin is performed.
Three new strategies for PDE by using wavelet matching Three new strategies for PDE by using wavelet matching error characteristic (WMEC) are proposed.error characteristic (WMEC) are proposed.
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Proposed AlgorithmProposed Algorithm
MR-WMEC-PDEMR-WMEC-PDE
Searching Order Strategy based on Wavelet Multi-Resolution Searching Order Strategy based on Wavelet Multi-Resolution PropertyProperty• Instead of the spiral search order, the proposed searching order Instead of the spiral search order, the proposed searching order
strategy uses the normalized partial SAD in LL subband level as the strategy uses the normalized partial SAD in LL subband level as the estimated SAD (ESAD)estimated SAD (ESAD)
• Then,Then, sort the ESAD using the counting sort algorithm in sort the ESAD using the counting sort algorithm in ascending ascending order to obtain the searching order order to obtain the searching order SO = {vSO = {vnn || n = 0, ...,w−1}n = 0, ...,w−1}..
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Proposed AlgorithmProposed Algorithm
MR-WMEC-PDEMR-WMEC-PDE Matching Order Strategy based on Wavelet-tree Grouping Matching Order Strategy based on Wavelet-tree Grouping
SchemeScheme• A A wavelet-tree grouping schemewavelet-tree grouping scheme according to spatial self-similarity according to spatial self-similarity
property and matching error clustering property of wavelet coefficientproperty and matching error clustering property of wavelet coefficient
• SortSort E Epp(B(Bl,bl,bl,ml,m) ) using the quick sort algorithm in descending order to obtain the matching order of leusing the quick sort algorithm in descending order to obtain the matching order of le
velvel l: MO l: MOll = {b = {bl,m l,m | m = 0, ...,M − 1}| m = 0, ...,M − 1}
B2,3
B4,1
B1,0B2,0
B3,0B4,0
B4,2 B4,3
B3,1
B3,2 B3,3
B3,4 B3,5
B3,6 B3,7
B3,8 B3,9
B3,10 B3,11
B2,1
B2,2
B2,7
B2,4 B2,5
B2,6 B2,11
B2,8 B2,9
B2,10
B1,1
B1,2 B1,3
B1,4 B1,5
B1,6 B1,7
B1,8 B1,9
B1,10 B1,11
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Proposed AlgorithmProposed Algorithm
MR-WMEC-PDEMR-WMEC-PDE
Comparison Interval Strategy based on Adaptive Sub-blocks Comparison Interval Strategy based on Adaptive Sub-blocks Checking UnitChecking Unit
• In conventional PDE methods, fixed comparison interval, such as eight-In conventional PDE methods, fixed comparison interval, such as eight-pixels or sixteen-pixels checking unit, is usually adopted.pixels or sixteen-pixels checking unit, is usually adopted.
• Combined with the wavelet-tree grouping scheme, an adaptive Combined with the wavelet-tree grouping scheme, an adaptive comparison interval strategy is proposed. comparison interval strategy is proposed.
• In the proposed strategy, every 2In the proposed strategy, every 2l−l−11 sub-blocks in the decomposition sub-blocks in the decomposition level level l l are used as the checking unit.are used as the checking unit.
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Experimental Results (1)Experimental Results (1)
• Simulation results are reported in the following ways:
• operation number : used to compute the partial distortion
• speed-up ratio : for motion estimation including the required overheads for comparison.
• For performance comparison with other algorithms
• Full Search Algorithm (FSA)
• Spiral-PDE [5]
• CPME-PDS [6]
• proposed MR-WMEC-PDE
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Experimental Results (2)Experimental Results (2)• Average Operation Number per Block for Tested Algorithms
On average speed-up ratio in terms of operation number, MR-WMEC-PDE is better than Spiral-PDE and CPME-PDS by about 92% and 34%, respectively.
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Experimental Results (3)Experimental Results (3)• Average Execution Time per Frame for Tested Algorithms
On average speed-up ratio in terms of execution time, MR-WMEC-PDE is better than Spiral-PDE and CPME-PDS by about 84% and 63%, respectively.
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ConclusionConclusion
Fast Lossless Multi-Resolution Motion Estimation Algorithm• Wavelet Matching Error Characteristic (WMEC)
• Three New Strategies for PDE Searching Order Strategy based on Wavelet Multi-Resolution Propert
y Matching Order Strategy based on Wavelet-tree Grouping Scheme Comparison Interval Strategy based on Adaptive Subblocks Checking
Unit