Applying 3 d methods to video for compression
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Applying 3-D Methods to Video for Compression. Salih Burak Gokturk Anne Margot Fernandez Aaron March 13, 2002 EE 392J Project Presentation. OUTLINE. MOTIVATION PREVIOUS WORK ALGORITHMS RESULTS CONCLUSION. BACKGROUND. Most common video compression scheme

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Applying 3-D Methods to Video for Compression

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Applying 3 d methods to video for compression

Applying 3-D Methods to Video for Compression

Salih Burak Gokturk

Anne Margot Fernandez Aaron

March 13, 2002

EE 392J Project Presentation


Outline

OUTLINE

  • MOTIVATION

  • PREVIOUS WORK

  • ALGORITHMS

  • RESULTS

  • CONCLUSION


Applying 3 d methods to video for compression

BACKGROUND

  • Most common video compression scheme

    • Blockwise transform (i.e. 2D-DCT) for spatial compression

    • Blockwise Motion Estimation and Compensation for temporal redundancy

    • Used in MPEG

  • Motion Compensated Predictive Coding is better than Image based coding since it uses a good prediction from the previous frame.


Applying 3 d methods to video for compression

OBJECTIVE

Exploit Temporal Redundancies MORE!

  • Why?

  • How?

    • Use 3-D Transformations and Methods.


3 d transform methods

3-D Transform Methods

  • Good for ideal case – smooth motion, global motion

  • Bad for non-uniform motion

  • Need large number of frame stores


Previous work

PREVIOUS WORK

  • 3-D DCT for Video

    • Bauer and Sayood, Chan and Sui, Servais and de Jager

  • 3-D Wavelets for Video

    – Pearlman et al. , Taubman et al.,

  • Motion Compensated Coding


Algorithms in our experiments

ALGORITHMS IN OUR EXPERIMENTS

  • 2D DCT

  • 3D DCT

  • (Block) Motion Compensated Coding

  • 3D (Volume) Motion Compensated Coding

  • Other Transformation as a prediction scheme (PCA, Wavelet)


2 d versus 3 d dct

2-D versus 3-D DCT

  • 2-D Blocks versus 3-D Blocks

  • 2-D DCT versus 3-D DCT

  • When would 3-D DCT not work?

Markov-1 chain

P(Xn=Xn-1) = p

Xn uniform [0, 255]


3d volume motion compensated coding

3D Volume Motion Compensated Coding

depth

Current stack of frames

Previous stack of frames

For each volume block…

Divide stack into volume blocks

Find 3D motion vectors

Calculate residual

3D DCT on residual

Q


3d volume motion compensated coding1

3D Volume Motion Compensated Coding

  • Finding the motion vectors

    • Full Search

    • Measurement criterion

      • MAD

      • standard deviation of residual

  • When it does not work

    • No smooth motion (acceleration present)

    • Cases when 2D MC does not work (occlusion, illumination, non-uniform motion)

    • Block size (depth) along time axis is too small or too big

  • Centroid Effect : Center of the block usually has a better prediction than edges of the block.


Initial prediction results

Initial Prediction Results

2D MC Prediction

3D MC Prediction


3d principal component analysis

[ ]

U=[ ]

2 – Each Block is represented by a linear

combination of principal components:

1

+

2

+

3

+

=

For each volume block…

Divide each stack into volume blocks

Find PCA

Coefs

Calculate residual

3D DCT on residual

Q

3D Principal Component Analysis

Current stack of frames

1 – Apply PCA on a large collection of blocks

= A = U  VT


Experimental setup

Experimental Setup

  • Techniques

    • 2D DCT by 8x8 Blocks

    • 3D DCT by 8x8x8 Blocks

    • Block Motion Compensated Coding (8x8 and 16x16 followed by 2-D DCT)

    • Volume Motion Compensated Coding (8x8x4, 8x8x6 and 8x8x8) followed by 3-D DCT.

    • Principal Component Analysis (use principal components of 8x8x8 blocks as prediction followed by 3-D DCT)

  • Bit Rate vs PSNR Comparison

    • DCT coefficients were quantized using a uniform quantizer

    • PSNR was computed over the same support region.

    • Bit rate was calculated by finding the theoretical entropy of the quantized DCT coefficients and motion vectors.


Miss am

Miss Am


Miss am1

0.14 bit/pixel

Miss Am

2D-DCT

2D-MC

3D-DCT

3D-MC

3D-PCA


Salesman 2d mc vs 3d mc

Salesman – 2D-MC vs 3D-MC

2D-MC

3D-MC

0.11 bit/pixel


Salesman 3d dct vs 3d mc

Salesman – 3D-DCT vs 3D-MC

3D-DCT

3D-MC

0.16 bit/pixel


Foreman

2D-MC

3D-MC

Foreman

3D-DCT

0.56 bit/pixel


Applying 3 d methods to video for compression

Bus


Conclusion

CONCLUSION

  • There is redundancy across temporal domain.

  • There is a lot of room for improvement if we use 3-D compression methods!

  • 2-D motion compensated coding is good for movies with A LOT of motion.

  • When movements are smooth, 3-D methods will perform better than 2-D motion compensated coding.

FUTURE WORK

  • Find Better Residual Coding Schemes for 3D MC. (That deals with centroid effect better)

  • Other 3D Methods ?


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