Application of Enhanced Hadamard Error Correcting Code in Video-Watermarking and his comparison to Reed-Solomon Code

摘要

Error Correcting Codes are playing a very important role in Video Watermarking technology. Because of very high compression rate (about 1:200) normally the watermarks can barely survive such massive attacks, despite very sophisticated embedding strategies. It can only work with a sufficient error correcting code method. In this paper, the authors compare the new developed Enhanced Hadamard Error Correcting Code (EHC) with well known Reed-Solomon Code regarding its ability to preserve watermarks in the embedded video. The main idea of this new developed multidimensional Enhanced Hadamard Error Correcting Code is to map the 2D basis images into a collection of one-dimensional rows and to apply a 1D Hadamard decoding procedure on them. After this, the image is reassembled, and the 2D decoding procedure can be applied more efficiently. With this approach, it is possible to overcome the theoretical limit of error correcting capability of (d-1)/2 bits, where d is a Hamming distance. Even better results could be achieved by expanding the 2D EHC to 3D. To prove the efficiency and practicability of this new Enhanced Hadamard Code, the method was applied to a video Watermarking Coding Scheme. The Video Watermarking Embedding procedure decomposes the initial video trough multi-Level Interframe Wavelet Transform. The low pass filtered part of the video stream is used for embedding the watermarks, which are protected respectively by Enhanced Hadamard or Reed-Solomon Correcting Code. The experimental results show that EHC performs much better than RS Code and seems to be very robust against strong MPEG compression.