A Fast and Efficient VOP Extraction Method Based on Watershed Segmentation

Alireza TavakkoliDr. Shohreh Kasaei

Gholamreza AmayehSharif University of Technology

2

Outline

Problem Definition. Literature Review. Proposed Method. Performance Analysis. Conclusions.

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Content-Based Functionalities in Video

User Interaction. Very Low Bit-rate Video

Compression. Video Indexing.

Object-Based Video Coding Systems: MPEG 4. H.263.

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Video Object Plane (VOP). A Video Scene is decomposed into VOPs. Multiple VOPs shape Video Object Layers. Proposing an Automatic VOP Extractor is a very difficult task.

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VOP Extraction

Spatio-Temporal Segmentation: Spatial Segmentation:

Watershed Segmentation. Temporal Information:

Motion Detection. Change Detection Masks.

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Watershed Segmentation Rain Fall Simulation:

Immersion Simulation: Vincent & Soille

(1991).

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Drawbacks of Watershed Segmentation

Results in over segmentation. Very time consuming. Solutions:

Region Merging Techniques. Predictive Watershed.

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Over Segmentation

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Region Merging Using Modified Gradient

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Preparing Image for Watershed Segmentation

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Resulting Watershed Segmentation

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Predictive Watershed Some Definitions:

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Prediction of Watershed

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Why CDM? Distance Learning Application:

Video is supposed to have stationary Background.

Real time video compression system. Stationary Background:

No Global Motion. No Camera Motion. No Illumination Changes.

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CDM and Noise Difference Noise:

Gaussian Noise: Due to intensity

changes. Can be reduced by

a Hypothesis test. Hypothesis test:

Noise if H0 True. Object if H1 True.

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Region Labeling Method Hypothesis Test

objx

objx

w dif

i

dif

i

dif

cameradif

thDPH

thDPH

yxObjD

dDif

1

0

2

2

2

2

2

22

,

2exp

2

1

2

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Watershed Update

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VOP Extraction Algorithm

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Experimental Results

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Experimental Results (Contd.)

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Experimental Results (Contd.)

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Experimental Results (Contd.)

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Experimental Results (Contd.)

Seq. Name

Frame Watershed

Method

Number of

Pixels

Number of

Regions

Time (msc.)

≈

Hall& Monitor

F-Frame Soile 84480 5961 10

Proposed

84480 396 20

P-Frame Proposed

1346 29 2

Walking Daniel

F-Frame Soile 110592 3749 10

Proposed

110592 352 20

P-Frame Proposed

2565 21 2

Matlab 6.2 Software, Pentium 4, 2.0GHz.

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Conclusions

Ceasing the Over segmentation Problem.

Speeding up the conventional method using temporal information.

A fast VOP extraction algorithm to be used in real time video processing systems.

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Questions?

?