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Résumé:
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Digital watermarking of multimedia content has been proposed as a method for different
applications such as copyright protection, content authentication, transaction
tracking and data hiding.
In this thesis, we propose a lossless watermarking approach based on Discrete Cosine
Transform (DCT) for a new application of watermarking. A depth map obtained from
a stereoscopic image pair is embedded into one of the two images using a reversible
watermarking algorithm. Different from existing approaches which hide depth map
in spatial domain, the depth information is hidden in the quantized DCT domain of
the stereo image in our method. This modification makes the watermarking algorithm
compatible with JPEG and MPEG-2 compression.
After the investigation of the quantized DCT coefficients distribution of the compressed
image and video, The bit-shift operation is utilized to embed the depth map into its associated 2D image reversibly for the purpose of achieving high compression efficiency of the watermarked image and/or video and high visual quality of stereo image and/or video after the depth map is extracted.
We implement the proposed method to analyze its performance. The experimental results show that a very high payload of watermark (e.g. depth map) can be embedded into the JPEG compressed image and MPEG-2 video. The compression efficiency is only slightly reduced after the watermark embedding and the quality of the original image or video can be restored completely at the decoder side. |
