UCL Discovery
UCL home » Library Services » Electronic resources » UCL Discovery

Using Watson perceptual model to improve quantization index modulation based watermarking schemes

Li, Qiao; (2007) Using Watson perceptual model to improve quantization index modulation based watermarking schemes. Doctoral thesis , UCL (University College London). Green open access

[thumbnail of Li.Qiao_thesis.Redacted.pdf]
Preview
Text
Li.Qiao_thesis.Redacted.pdf

Download (23MB) | Preview

Abstract

Quantization index modulation (QIM) is a popular watermarking scheme that has received considerable attention. Nevertheless, there are practical limitations of QIM. For example, traditional QIM uses a fixed quantization step size, which may lead to poor fidelity in some areas of the content. More serious problems of the original QIM algorithm include its extremely sensitivity to valumetric scaling (e.g., changes in amplitude) and re-quantization (e.g., JPEG compression). In this thesis, we first propose using Watson's perceptual model to adaptively select the quantization step size based on the calculated perceptual "slack". Experimental results on 1000 images indicate improvements in fidelity as well as improved robustness in high-noise regimes. Watson's perceptual model is then modified such that the slacks scale linearly with valumetric scaling, thereby providing a QIM algorithm that is theoretically invariant to valumetric scaling. In practice, the robustness against valumetric scaling is significantly improved, but scaling can still result in errors due to cropping and roundoff that are an indirect effect of scaling. Two new algorithms are proposed the first based on regular QIM and the second based on rational dither modulation. A comparison with other methods demonstrates improved performance over other recently proposed valumetric-invariant QIM algorithms, with only small degradations in fidelity. Spread transform dither modulation (STDM) is a form of QIM that is more robust to re-quantization. However, the robustness of STDM to JPEG compression is still poor and it remains very sensitive to valumetric scaling. We describe how a perceptual model can be incorporated into the STDM framework to (i) provide robustness to valumetric scaling, (ii) reduce the embedding-induced perceptual distortion and (iii) significantly improve the robustness to re-quantization.

Type: Thesis (Doctoral)
Title: Using Watson perceptual model to improve quantization index modulation based watermarking schemes
Identifier: PQ ETD:591238
Open access status: An open access version is available from UCL Discovery
Language: English
Additional information: Thesis digitised by ProQuest. Third party copyright material has been removed from the ethesis. Images identifying individuals have been redacted or partially redacted to protect their identity.
UCL classification: UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science > Dept of Electronic and Electrical Eng
URI: https://discovery.ucl.ac.uk/id/eprint/1443976
Downloads since deposit
35Downloads
Download activity - last month
Download activity - last 12 months
Downloads by country - last 12 months

Archive Staff Only

View Item View Item