tub @ mediaeval 2014 visual privacy task: reversible scrambling on foreground masks

TUB @ MediaEval 2014 Visual Privacy Task: Reversible Scrambling on foreground masks

S. Schmiedeke, P. Kelm, L. Goldmann, T. Sikora Communication Systems Group | Imcube Labs GmbH

TUB @ MediaEval 2014 Visual Privacy Task: Reversible Scrambling on Foreground Masks

• Motivation

• Method overview

• Experimental results

• Conclusion

Seite 2

Motivation

TUB @ MediaEval 2014 Visual Privacy Task: Reversible Scrambling on Foreground MasksSeite 3

Color Histogramm DescriptorColor Histogramm Descriptor

Visual Distance

Motivation


revertible

Scrambling of foreground masks

Descrambling of foreground masks

Transmission/ Compression Error


Method overview

Seite 5

Background modelling• Based on Gaussian-Mixture models (GMM)• Number of needed components is automatically detected

Region of interest: Foreground masks• Background subtraction• Erosion and morphological operations

Scrambling of ROI• Reversible shuffling of pixels within disjunct ROI areas


Method overview

Seite 6

• Simple and fast

• On-the-fly background modelling

• Parameter-free (except for global pixel threshold)


Method overview

Seite 7

• Robust to camera shaking

• Slight camera movements were• compensated by frame subsampling and by GMM


Method overview

Seite 8

• Scene information remains • visible to operator

• Events such as left-luggage, vandalism, emergency cases, etc. stay visible

Method overview


• Shapes of scrambled persons • allow basic scene understanding

• Actions such as fighting, mugging, etc. are still recognizable


Experimental results

• Good privacy preservation (above median scores)

• Fair visual „appropriateness“ (near to median)

• Good Level of Intelligibility (near to median)

Seite 10

Evaluation scores (median scores in brackets)

Stream 1 Stream 2 Stream 3

Intelligibility 73.6% (74.9%) 75.2% (79.3%) 66.5% (69.6%)

Privacy 59.0% (50.2%) 62.6% (46.5%) 60.7% (40.7%)

Pleasantness 21.9% (24.8%) 60.8% (69.6%) 58.1% (59.7%)

Conclusion

11

• Good overall privacy level

• Good level of retention of ‘useful’ information

• Fast (real-time) and easy to implement

• Compression does not break recovering

scrambling

Conclusion

12

• Still room for improvement in background modelling


Thank You! Questions?

[email protected]


Backup


Method overview

Seite 15

• Simple and fast

• Robust to camera shaking

• Scene information remains visible to operator

• Shapes of scrambled persons allow basic scene understanding (fighting, mugging, etc.)

tub @ mediaeval 2014 visual privacy task: reversible scrambling on foreground masks

Software