` 1 department of electrical engineering, stanford university anne aaron, prashant ramanathan and...
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1
Department of Electrical Engineering,Stanford University
Anne Aaron, Prashant Ramanathan and Bernd Girod
Wyner-Ziv Coding of Light Fields for Random Access
Aaron, Ramanathan, Girod: Wyner-Ziv coding of light fields for random access 2
Overview
Light fields Predictive coding and random access Wyner-Ziv coding for light fields Simulation results
Aaron, Ramanathan, Girod: Wyner-Ziv coding of light fields for random access 3
What is a Light Field?
A 4-D data set for image-based rendering,typically parameterized as a 2-D set of images. [Levoy and Hanrahan, 1996] [Gortler et al., 1996]
Aaron, Ramanathan, Girod: Wyner-Ziv coding of light fields for random access 4
Light Field Coding using Prediction
geometrymodel
image 1 image 2
level 0
level 1
level 2
hierarchical prediction
desired image
decodedimages
[Magnor and Girod, 2000] [Ramanathan et al., 2002][Chang et al., 2003]
Aaron, Ramanathan, Girod: Wyner-Ziv coding of light fields for random access 5
Rendering a Single Novel View
Garfield light field
How do we perform better than intracoding?
Aaron, Ramanathan, Girod: Wyner-Ziv coding of light fields for random access 6
Wyner-Ziv Coding
Lossy compression with decoder side information
EncoderX
Y
Decoder
X
)(| dRWZYX
Statistically dependent
[Wyner and Ziv, 1976]
Aaron, Ramanathan, Girod: Wyner-Ziv coding of light fields for random access 7
Wyner-Ziv image
Key image
•Better rate-distortion performance than intracoding [Zhu, Aaron, Girod, 2003]
•Similar work by [Jagmohan, Sehgal, Ahuja, 2003]
At the decoder, side information for decoding Wyner-Ziv image is rendered from available key images
Wyner-Ziv Coding of Light Fields
Aaron, Ramanathan, Girod: Wyner-Ziv coding of light fields for random access 8
Wyner-Ziv DCT Light Field Codec
WZ imageW
Rendering
Reconstruction
Key image
KShape-adaptive
Intracoding
Shape-adaptivedecoding
DCT
For each transform band k
K’
Yk
Xk Xk’
IDCT
Decoded WZ image
level Quantizer
DCT
kM2 Turbo Encoder
Turbo Decoder
Extract bit-planes
qk
bit-plane 1
bit-plane 2
bit-plane Mk
…
qk’
Side information
Shape processing
Shape processing
Aaron, Ramanathan, Girod: Wyner-Ziv coding of light fields for random access 9
R-D Performance for WZ images
Garfield light field
288 images each at 144x192 pixelsHemispherical camera setting with 8 rows and 32 columns
Half of the images are WZ images
Aaron, Ramanathan, Girod: Wyner-Ziv coding of light fields for random access 10
Rendering a Single Novel View
Garfield light field data set
R-D Performance averaged over 20 novel views. Each novel view is rendered from closest 4 images.25%
2 dB
Aaron, Ramanathan, Girod: Wyner-Ziv coding of light fields for random access 11
Sample Rendered View
Intracoding 1.5 bpop, 33.8 dB
Original Wyner-Ziv coding 1.4 bpop, 36.2 dB
Aaron, Ramanathan, Girod: Wyner-Ziv coding of light fields for random access 12
Summary
Wyner-Ziv coding of light field images for random access and compression efficiency
Up to 2 dB PSNR improvement over intracoding for rendering novel views
Single representation of data setmultiple representation solution [Ramanathan and Girod, MMSP 2004]
Aaron, Ramanathan, Girod: Wyner-Ziv coding of light fields for random access 13
Sample Rendered View
Intracoding 1.6 bpop, 33.7 dB
Original Wyner-Ziv coding 1.9 bpop, 36.6 dB