Multimedia Watermarking

(quoted from Kwangwoon University digital media lab)
Speaker: Bede Liu(Princeton University)
Digital watermark
What?
-Secondary information embedded in media data
-Watermarking and data hiding
How?
-Natural images
-Document: binary images, sketches, maps, Check 21,…
Attacks
-To render watermarking ineffective
-Legal issues

How to insert watermark
How to extract watermark

Spread spectrum embedding
Ideas
-Place watermark in perceptually significant spectrum
-Use random vector as wmk to avoid artifacts

Robustness
-scaling JPEG, dithering, cropping

Comment
-Need original unmarked image
-May need to perform registration
-Other attacks

How to embed watermark
-Additive embedding ex spread spectrum
-Forcing a relationship ex odd-even

Data hiding for error concealment
-recovery of blocks lost in transmission
-simple interpolation gives poor image quality

Edge estimation and interpolation
-Edge estimation from surrounding blocks

Error concealment using date hiding
-Need s good neighboring blocks
-Two steps of error concealment estimation edge

Shuffling for binary images
-Uneven distribution of flappable pixels among blocks
-Random shuffling “equalized” distribution

A dilemma
-To prove that a watermark W has been embedded in an image.
-Given inages->block DCT(32x32)->subset X
-Prove existence of W