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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.
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