tailieunhanh - Recent Advances in Signal Processing 2011 Part 5

Tham khảo tài liệu 'recent advances in signal processing 2011 part 5', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | JPEG2000-Based Data Hiding and its Application to 3D Visualization 127 embedding method is blind if data extraction by the recipient does not require the original cover. Being an active research area for the last two decades data hiding is now an established field and that is why a lot has been written about it Cox et al. 2008 . We therefore focus on the literature about wavelet-based data hiding which is again very extensive and one is compelled to be brief and limit oneself to JPEG2000 as far as possible. Looking at the structure of JPEG2000 codec as explained in Section 2 makes one think about when and where to interrupt the coding flow in order to embed the message. Theoretically you can interrupt the codec anywhere for embedding but at the periphery the embedding capacity is lower accompanied by relatively higher distortion. DWT Tier 1 Tier 2 Module Coding Coding Embed in the DWT coefficients The method must take into account the quantization and T1 coding loss. Embed in the Quantization indices I The method must cater for the anticipated T1 coding loss. Embed in the Tl-coded symbols Subband and inter-block correspondence Ì intact but intraband correspondence lost. - reduced embedding capacity Embed in the JPEG2000 packets - Compact representation of source image. - Careless modification may result in failure of expanding the bit-stream - use lazy mode Fig. 3. Interrupting the JPEG2000 coding pipeline for information hiding. Fig. 3 illustrates the potential interruption stages during the JPEG2000 coding to embed data in the to-be-encoded image3. Every type of intervention has its advantages and limitations. Embedding immediately after the DWT step would have the advantage of larger word size of the coefficients leading to high capacity. All the components are easily available one can allocate coefficients at will. This strategy may be especially convenient for JPEG2000 in lossless mode. The problem is however that steganalysis is easier since there is a high .