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Scalable Video Watermarking

Peter MeerwaldJune 25, 2007

Watermarking

� Watermarking is imperceptible embedding of information into multimedia data [Cox02a]

� Applications: copyright protection, data authentication, fingerprinting, �

� Video pecularities:

� Need perceptual model for temporal dimension [Watson, Koz05a]

� Highly correlated data gives rise to collusion attack [Su05a, Doerr05b]

� Data volume favors compressed-domain embedding, real-time processing

Scalable Video� Capability to adapt video bitstream to

presentation device or transmission conditions

� SNR or quality scalability

� Resolution scalability, eg. CIF � QCIF

� Spatial scalability

� Temporal scalability, eg. 30 15 frames/s�

Frame 0, CIFFrame 0, CIF Frame 1, CIFFrame 1, CIF Frame 2, CIFFrame 2, CIF Frame 3, CIFFrame 3, CIF

Frame 0, QCIFFrame 0, QCIF Frame 2, QCIFFrame 2, QCIF

Scalabe Video Codecs

� H.264 SVC extension based on hybrid H.264/AVC codec [Schwarz06a]

� Resolution layers, quantization refinement (FGS)

� GOP structure

� MC-EZBC builds on motion-compensated temporal filtering (MCTF) followed by spatial subband decomposition [Ohm05a]

� Embedded bitstream

Scalable Video Watermarking

Host Video

Target Video

HostModificaton

MessageCoding

Message

FormationBitsteam

Scalable Video Coding

Watermark Embedder

BitstreamExtraction

Key

DistortionTransmission

Transmission properties

Scalable Coding Knowledge

Scalability Control

DecoderVideo

Receiver

DecoderWatermark Message

Key

Processing / AttackDistortion

Communication channel, detection or decoding problem

Scalable Watermark Properties

[Piper05a]

� Detectability: Watermark is detectable in any portions of the scaled content which is of 'acceptable' quality.

� Graceful Improvement: Increased portions of the scaled content provide reduced error in watermark detection.

� Pseudo-random, bipolar sequence (same key for all frames)

� 3-level spatial DWT decomposition

� Embedding: Perceptually shaped (Watson) embedding in detail subbands

� Detection: whitening filter (3x3, high-pass), correlation per decomposition level

A Simple Watermarking Scheme (1)

wi�{�1 ,1}

vi=v

i�� s

iwi

cl=�v �w

��v�� �w� c=maxlcl

A Simple Watermarking Scheme (2)

Watermarked Foreman sequenceCIF (352x288, 4:2:0)

PSNR ~35.5 dB

Spatial domaindifference image

DFT domaindifference image

Scheme is called 'DWT'

Scalability Distortion On Watermark

SNR

Resolution

Temporal

Quantization

Block Replacement Attack due to motion-compensation (?)

Downsampling, synchronization problem

Resynchronization, depending on key-schedule

Reduced data rate

Reduced data rate

Experiment

� Embed DWT watermark in first 8 frames of Foreman, PSNR ~35 dB

� Form scalable bitstream

� H.264/SVC: GOP size 8, 2 resolution layers (QCIF, CIF), 3 FGS layers, QP 40

� MC-EZBC: 4 level decomposition

� Extract bitstream:

� BitStreamExtract <fname> -e <res.>@<frate>:<brate> (SVC)

� pull <fname> -s <res. layer> -r <brate> (MC-EZBC)

� Decode bitstream & detect watermark

SNR Scalability

0

0.2

0.4

0.6

0.8

1

500 1000 1500 2000 2500 3000 3500 30

32

34

36

38

40

42

Cor

rela

tion

PS

NR

(dB

)

Rate (kbit/s)

Threshold

Strength

MC-EZBC R/DH.264 SVC R/D

Correlation (MZ-EZBC)Correlation (SVC)

8 frame average, Foreman sequence (CIF)

Resolution Scalability

8 frame average, Foreman sequence

0

0.1

0.2

0.3

0.4

0.5

0.6

500 1000 1500 2000 2500 3000 3500

Cor

rela

tion

Rate (kbit/s)

Threshold

Correlation CIF (MZ-EZBC)Correlation QCIF (MZ-EZBC)

Correlation CIF (SVC)Correlation QCIF (SVC)

Further Investigations

� Implement collusion attacks (TFA, etc.)

� Motion compensation as Block Replacement Attack (BRA) (?)

� Temporal scalability vs. synchronization with key-schedule

� Try quantization-based schemes (QIM, ST-SCS, TCQ)

� Consider authentication application & compressed-domain embedding

� Use temporal transform: 3D-DCT, 3D-DFT, DFT-2D-DCT, t+2D DWT

� Exploit temporal masking, motion-coherent watermarking

� Employ ROC, BER measure instead of correlation

References

� Cox02a, Digital watermarking, Morgan Kaufman, 2002.

� Su05a, Statistical invisibility for collusion-resistant digital video watermarking, IEEE Tr. MM, 7(1):43-51, 2005.

� Koz05a, Oblivious video watermarking using temporal sensitivity of HVS, 961-964, ICIP '05.

� Schwarz06a, Overview of the scalable H.264/MPEG4-AVC extension, ICIP '06.

� Ohm05a, Advances in scalable video coding, Proc. IEEE, 93(1):42-56, 2005.

� Piper05a, Resolution and quality scalable spread spectrum image watermarking, 79-89, MM-SEC '05.

� Doerr05b, Security issue and collusion attacks in video watermarking, PhD thesis, Univ. of Nice at Sophia-Antipolis, France. 2005.