Problmatique Mthodes de contrle d'erreurs Schma d'allocation conjointe de dbit : cas unicast Evoluti

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Fully scalable object based video coder based on
analysis-synthesis scheme
Marc Chaumont, Nathalie Cammas1 and Stéphane
Pateux Temics, IRISA/INRIA, France, 1France
Telecom, France
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Context

• What is scalability ?
• ordering the coded information by decreasing
  significant order.
• different scalability object, SNR, temporal,
  spatial, bitstream.
• Why looking for scalability ?
• bitstream can be decoded at different bitrate and
  different qualities
• Why using an object coder instead of an non
  object coder ?
• object manipulation
• bitrate allocation
• better motion estimation (limit mesh degeneracy
  on occlusion boundaries)
• good tradeoff between pixel based and model based
  approach.

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Proposed approach

• Objectives
• scalability on the 3 informations motions -
  textures - shapes
• independent coding of the 3 informations
• long term approach
• Why those objectives
• scalability
• independent coding to allow a better rate
  distribution between motion -texture - shape.
• long term approach to allow an efficient coding
  with wavelet
• Our proposed solution
• using wavelet (to allow scalability)
• decorrelation (to allow independent coding)
• long term motion estimation (to allow a long term
  approach)

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Proposed approach analysis-synthesis scheme
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Proposed approach analysis-synthesis scheme
S E G M E N T A T I O N
S Y N T H E S I S
obj1
reconstructed sequence
obj2
frames
frames
1 - ANALYSIS 2 - CODING 3 - DECODING
NO SHAPE
shapes
z-order
z-order
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Proposed approach analysis-synthesis scheme
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Proposed approach analysis-synthesis scheme
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Proposed approach analysis-synthesis scheme
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Proposed approach analysis-synthesis scheme
GOP
GOP
long term motion estimation (active mesh)
motions
decorrelation thanks to motion and padding
textures
contours
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Proposed approach analysis-synthesis scheme
GOP
GOP
long term motion estimation (active mesh)
motions
decorrelation thanks to motion and padding
textures
contours
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Long term motion estimation
GOP size 8
Motion estimation via active mesh
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Proposed approach analysis-synthesis scheme
GOP
GOP
long term motion estimation (active mesh)
motions
decorrelation thanks to motion and padding
textures
contours
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Decorrelation motion projection padding
textures projected
textures padded
initial textures
contours projected
contours padded
initial contours
contours projected
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Proposed approach analysis-synthesis scheme
GOP
GOP
long term motion estimation (active mesh)
motions
decorrelation thanks to motion and padding
textures
contours
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motion - texture - contour
3 independent information
GOP size 8
motion (mesh)
textures projected and padded
contours projected and padded
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Benefits of the decorrelation

• Decorrelation allows
• independent coding of the 3 informations motion
  -texture - shape.
• ? allows independent lossy coding on each
  information
• ? a better rate distribution between motion
  -texture - shape.
• distribution example for Foreman foreground CIF
  15Hz at 85 Kb/s
• texture 76
• motion 17
• shape 7
• long term approach
• ? efficient coding with wavelet
• Example our scheme on Erik sequence CIF 15Hz
  at 64Kb/s is better than H26L VM 8.4 (less than 1
  dB)
• scalability on the 3 information thanks to
  wavelet

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Proposed approach analysis-synthesis scheme
GOP
GOP
long term motion estimation (active mesh)
motions
decorrelation thanks to motion and padding
textures
contours
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Coding step
Spatio-temporal transformation
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Results
Background object
Texture Motion 11,5 Kb/s
Foreground object
Shape 3 Kb/s
Reconstructed sequence at 62 Kb/s
Texture 39,7 Kb/s
Motion 7,3 Kb/s
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Results

• With or without shape distortion

Without shape distortion
Reconstructed sequence at 62 Kb/s (with shape
distortion)
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Results

• H264/AVC versus our object scalable scheme

Our scheme 62 Kb/s PSNRtexture-foreground 29.3
H264/AVC non object 62 Kb/s PSNRforeground 27.9
. 1 B frame, . RD optimization, . CABAC.
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Results

• Spatial scalability

Sequence 62 Kb/s CIF 15 Hz
Sequence 49 Kb/s QCIF 15 Hz
shape 3
Kb/s background text mvt 11,5
Kb/s foreground text mvt 47 Kb/s
shape 1,7
Kb/s background text mvt 9,6
Kb/s foreground text mvt 37,5 Kb/s
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Results

• Spatio-temporal scalability

Sequence 49 Kb/s QCIF 15 Hz
Sequence 36 Kb/s QCIF 7.5Hz
shape 1,2
Kb/s background text mvt 6,7
Kb/s foreground text mvt 27,9 Kb/s
shape 1,7
Kb/s background text mvt 9,6
Kb/s foreground text mvt 37,5 Kb/s
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Results

• SNR scalability

Sequence 49 Kb/s CIF 15 Hz
Sequence 126 Kb/s CIF 15 Hz
shape 6,8
Kb/s background text mvt 24,4
Kb/s foreground text mvt 94,9 Kb/s
shape 1,7
Kb/s background text mvt 9,6
Kb/s foreground text mvt 37,5 Kb/s
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Conclusion A novel object based video coder

• Based on
• analysis-synthesis scheme
• decorrelation of the 3 informations
• (active mesh - padding - z-order)
• fully scalable
• Benefits
• fully scalable (SNR, spatial, temporal on each
  information)
• independent coding of the 3 informations
• ? better bitrate distribution
• long term approach
• ? allow the use of longer wavelet kernels
• Future work
• improving texture coding
• improving motion estimation in occlusion part