Robust block selection for watermarking video streams Tamás Polyák, Gábor Fehér Budapest University of Technology and Economics Hungary

What is watermarking? Embed information into a digital signal Audio Video Text file … Classification of watermarks Visible / invisible Robust / fragile …

Embed information into a digital signal

Audio

Video

Text file

…

Classification of watermarks

Visible / invisible

Robust / fragile

…

Use cases Multimedia security Fingerprinting Copyright information Copy protection … Other areas Subtitles Metadata Secret communication …

Multimedia security

Fingerprinting

Copyright information

Copy protection

…

Other areas

Subtitles

Metadata

Secret communication

…

Conflicting requirements Robustness Capacity Imperceptibility

Watermark life cycle Original ≈ Extracted

Our goals Watermarking low resolution video CIF (352 x 288) QCIF (176 x 144) Requirements Robust against lossy compressions Low quality loss Limited complexity

Watermarking low resolution video

CIF (352 x 288)

QCIF (176 x 144)

Requirements

Robust against lossy compressions

Low quality loss

Limited complexity

Base algorithms Ellinas (2007) Image watermarking in the wavelet domain Embedding data around the edges Too complex Hides only 1 bit Cox (1998) Video watermarking in the spatial domain Spread spectrum noise Weak against lossy compression

Ellinas (2007)

Image watermarking in the wavelet domain

Embedding data around the edges

Too complex

Hides only 1 bit

Cox (1998)

Video watermarking in the spatial domain

Spread spectrum noise

Weak against lossy compression

Proposed algorithm Data hiding in wavelet domain Fast 2-level DWT

Data hiding in wavelet domain

Fast 2-level DWT

Proposed algorithm Edge detection in middle frequency components Sobel edge detector

Edge detection in middle frequency components

Sobel edge detector

Steps of embedding process Apply DWT, calculate suitable area Transform data into noise Extend data with a chip-rate (cr): 1 0 1 0 1 1 1 1 -1-1-1-1 1 1 1 1 -1-1-1-1 Multiplicate with key (N i ) 1 1 1 1 -1-1-1-1 1 1 1 1 -1-1-1-1 Data * 1 -1-1 1 -1 1 -1 1 1 -1 1 -1 -1 1 1 -1 Key 1 -1-1 1 1 -1 1 -1 1 -1 1 -1 1 -1-1 1 Apply strength (  ) 5 -5-5 5 5 -5 5 -5 5 -5 5 -5 5 -5-5 5 Add noise to the selected area Apply IDWT

Apply DWT, calculate suitable area

Transform data into noise

Extend data with a chip-rate (cr):

1 0 1 0

1 1 1 1 -1-1-1-1 1 1 1 1 -1-1-1-1

Multiplicate with key (N i )

1 1 1 1 -1-1-1-1 1 1 1 1 -1-1-1-1 Data

* 1 -1-1 1 -1 1 -1 1 1 -1 1 -1 -1 1 1 -1 Key

1 -1-1 1 1 -1 1 -1 1 -1 1 -1 1 -1-1 1

Apply strength (  )

5 -5-5 5 5 -5 5 -5 5 -5 5 -5 5 -5-5 5

Add noise to the selected area

Apply IDWT

Apply DWT, calculate suitable area Correlating key with values in area Make decision: d j < -T : 0 d j > T : 1 else: x Steps of detection process

Apply DWT, calculate suitable area

Correlating key with values in area

Make decision:

d j < -T : 0

d j > T : 1

else: x

Quality loss Original Watermarked

Original

Watermarked

Quality loss The watermarked frame and the watermark

The watermarked frame and the watermark

Robustness test Hide 128 bits Apply lossy compressions with various bitrates H.264/AVC XviD Extract watermark, compare to original Correct bits: extracted bit = original bit Erroneous bits: extracted bit ≠ original bit Unrecognized bits: detector could not decide

Hide 128 bits

Apply lossy compressions with various bitrates

H.264/AVC

XviD

Extract watermark, compare to original

Correct bits: extracted bit = original bit

Erroneous bits: extracted bit ≠ original bit

Unrecognized bits: detector could not decide

Video quality after H.264 /AVC Lower bitrate  lower quality Lower bitrate  weaker watermark signal Uncompressed 1008 kbps 32,72 dB 720 kbps 31,31 dB 384 kbps 28,58 dB

Lower bitrate  lower quality

Lower bitrate  weaker watermark signal

Results of robustness test

Conclusion The algorithm is resistant against lossy compression  imperceptible to the HVS  not real-time  speed needs to be improved

The algorithm is

resistant against lossy compression 

imperceptible to the HVS 

not real-time 

speed needs to be improved