Multiple description (MD) coding has many applications in transmission of images over unreliable packet or multiple path networks that can not guarantee lossless data delivery. In this paper, an effective multiple description image coding scheme is introduced. This scheme is mainly based on the wavelet transform and multiple description lattice vector quantization (MDLVQ). The haracteristics of wavelet coefficients in different frequency subbands are taken into account in the design of the MD image coder with different optimized MDLVQ parameters. The experimental results are presented to demonstrate the effectiveness of the proposed scheme.

数字水印技术是现代版权保护的手段之一，而数字水印系统的鲁棒性是其能够起到版权保护作用的必要条件，也是当前的研究热点。本文提出了一种Turbo 编码的图像水印的软判决检测算法，在不改变原有的嵌入算法的前提下，只需在接收端采用软判决检测算法就能有效地提高水印系统的鲁棒性。在本文提出的方案中，首先把原始水印信息进行Turbo 编码，在图像DFT变换域中，修改两个相同频点系数的大小关系来嵌入经过编码的水印信息。在检测水印时，采取软判决检测算法提取用于Turbo 译码的软输入信息，可有效地提高系统的鲁棒性。实验结果表明，软判决检测的比特错误率普遍低于硬判决检测的比特错误率，在高斯噪声情况下，甚至能低0.169。