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March 2, 2006
3D Mesh Coding and 3D Mesh Coding and TransmissionTransmission
Lihang YingDepartment of Computing Science
University of Alberta
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OutlineOutline
3D Mesh Data3D Mesh Coding
– Valence-Driven Approach
Error-Resilient 3D Mesh Coding and Transmission– Multiple Description Coding
Proposed Research
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3D Mesh Data3D Mesh Data
Geometry:– 3D positions (x-y-z coordinates) of vertices– Coding: 1)Quantization, 2)Differential Coding,
3) Entropy Coding
Connectivity:– How vertices are connected
• Raw data: vertex indices of each face• Large redundancy
– Main Focus of 3D Mesh Coding
Photometry– Colors,Normals,Texture
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3D Mesh Coding3D Mesh Coding
Since early 1990s Up-to-date Survey: [PKK05]
VRML V.2 and MPEG-4 Standard
State-of-the-art Method
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Valence-Driven ApproachValence-Driven Approach
Encoding
Thick line: active lists Dashed line: visited edge Dark point: focus
Encoding Stream: add 6, add 7, add 4, add 4, add 8, add 5, add 5, add 4, add 5, split 5, add 4, add 4, add dummy 6, add 4
add 6, add 7, add 4 add 4 add 8
add 5 add 5 add 4add 5
split 5 add 4 add 4 add dummy 6
add 4
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Valence-Driven ApproachValence-Driven Approach
Decoding
Encoding Stream: add 6, add 7, add 4, add 4, add 8, add 5, add 5, add 4, add 5, split 5, add 4, add 4, add dummy 6, add 4
Thick line: active lists Dashed line: visited edge Dark point: focus
add 6, add 7, add 4 add 4 add 8 add 5 add 5
add 4 add 5split 5
add 4 add 4 add dummy 6
add 4
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Progressive Valence-Progressive Valence-Driven 3D Mesh CodingDriven 3D Mesh Coding
–
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Connectivity Coding is Connectivity Coding is Sensitive to Error Sensitive to Error
– Previous codes impact all subsequent codes.
– Example: one-code error in Edgebreaker method [Rossignac99] results (the right):
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Error ResilienceError Resilience
Error-Resilient Transmission [AAR05]
– Unequal Error Protection– Interleaved Packets
Piece-based Error-Resilient Coding [YKK01]
– Divide mesh into pieces, encode piece by piece, then encode connectivity between pieces.
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Progressive Coding– Enhance layers depends on base layers
Piece-based Error-Resilient Coding– Not friendly to Perceptual Quality
Multiple Description Coding– Each description can be encoded
independently– More descriptions received result
higher quality.– Less efficient
Multiple Description Multiple Description Coding(1)Coding(1)
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Multiple Description Multiple Description Coding(2)Coding(2)Existing Work [JWC04]
– Idea:• Only split the geometry (vertex position)
data into descriptions• Transmit the connectivity of the entire mesh
via a high quality channel.
– How to split vertices into descriptions • Should be spaced evenly in the mesh for
interpolating missed vertices• Construct a vertex spanning tree and assign
each vertex at level l into i-th description.
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Multiple Description Multiple Description Coding(3)Coding(3)Existing Work [JWC04]
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Proposed ResearchProposed Research
Objective– With packet loss: wireless network– No retransmission: real-time
applications– No error protection– Perceptual quality friendly
Multiple Description Connectivity Coding
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Will Improve on Valence-Will Improve on Valence-Driven ApproachDriven Approach
With trivial size and be kept in all descriptions
Or, can be interpolated
add 6, add 7, add 4 add 4 add 8 add 5 add 5
add 4 add 5split 5
add 4 add 4 add dummy 6
add 4
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The EndThe End
Thank you!