Ivan Damnjanovic

Contact Details

Title: Research Student
Tel: National: 020 7882 7880
International: +44 20 7882 7880
Fax: National: 020 7882 7997
International: +44 20 7882 7997
Email: ivan.damnjanovic@elec.qmul.ac.uk
Room: 103

Research Lab: Multimedia and Vision Lab

Supervisor: Prof Ebroul Izquierdo

Research Area: Watermark Embedding in MPEG2 bit-stream

Research interests: Digital Watermarking, Video Coding, Perceptual Modelling, Information Theory, Error Correction Coding.

Participation in projects: BUSMAN - Bringing User Satisfaction to Media Access Networks

Research Scope

A rapid expansion in digital technology, we are witnessing in past two decades, introduced huge benefits both for the industry and for the consumers. However, it also raises a number of questions regarding digital media copyrights. Digital media encryption can provide secure delivery of the content, but once the content is decrypted on a consumer side, it cannot prevent unlimited copping of the material. Digital watermarking, as a technique for embedding secret watermark directly to the digital content, came as possible solution to complement encryption, but also to a range of other interesting applications such as authentication, broadcast monitoring or data embedding.

Digital media are mainly transferred and archived in a compressed form. Due to performance constraints in terms of computing efficiency and degradation, re-encoding and watermarking in the pixel domain is not feasible. Hence, it is desirable to embed and detect watermark in compressed domain. Several techniques have been reported in the literature aiming at watermarking in the compressed domain and they are mainly based on spread-spectrum paradigm, where a watermark message is transmitted as a narrow-band signal via a video signal, which acts as a wide-band channel.

One of the main requirements in digital watermarking is that the watermark must be embedded in such way that it does not introduce visual artefacts to the host signal. Since the watermark power is bounded by perceptual visibility, watermark bits need to be spread by a large chip-factor in order to have reliable detection, which will decrease a number of watermarking bits that can be put in the same embedding window. Detection reliability can be increased by pseudo-random spreading of the watermarking bits and also perceptual watermarking models can be incorporated to increase the embedding power. In our technique, we used combination of Watson’ JND model ( A.J. Ahumada, H.A. Peterson and A. B. Watson, “An Improved Detection Model for DCT Coefficients Quantization”, ”, Proc. of SPIE, Human Vision, Visual and Digital Display IV, ed. B. E. Rogowitz, vol. 1913-14, 1993, pp. 191-201.) and improved JND model using block classification (X.H. Zhang, W.S. Lin and P. Xue, “Imroved Estimation for Just-noticeable Visual Distortions”, Signal Processing, vol. 85, no. 4, 2005, pp. 795-808).

In compressed domain watermarking, another limiting factor is that the video bit-rate must remain the same. Embedding in a particular coefficient is not allowed if it increases the bit-rate giving decrease in the power of the watermarked signal. The number of altered coefficients can be increased with an optimized bit-rate preserving scheme on macro-block level.

The watermarking process can be seen as a communication of secret message via a noisy channel, where noise is originated by the host video signal by itself and the attacks. Although, above mentioned techniques can increase the watermarking power and Signal to Noise Ratio of the watermarking channel, the SNR is still low to communicate desirable number of bits with high decoding rate. Hence, it is necessary to introduce some form of error correction coding to boost the capacity and improve the detection rates.

We are proposing to use duo binary Turbo codes to protect watermarking channel. Turbo codes (TCs) have received great attention since their introduction in 1993. This is due to the extra-ordinary performance at low bit error rates, reasonable complexity, and versatility for encoding blocks with various rates and sizes.

Publications

I. Damnjanovic, and E. Izquierdo, Turbo Coding Protection of Compressed Domain Watermarking Channel, Proc. of IEEE International Conference on Computer as a Tool, Belgrade, Serbia and Montenegro, 21-24 November 2005.

I. Damnjanovic, and E. Izquierdo, Capacity Enhancement of Compressed Video Watermarking Using Turbo Codes, 6th European workshop on Image Analysis for Multimedia Interactive Services, Wiamis’05, Montreux, Switzerland, Apr. 13-15, 2005

E. Izquierdo, I. Damnjanovic, P. Villegas, L.-Q. Xu, S. Herrmann, "Bringing user satisfaction to media access: the IST BUSMAN Project", Information Visualisation, 2004. IV 2004. Proceedings. Eighth International Conference on, 14-16 July 2004 Page(s):444 - 449