适合水声信道传输的水下图像高效编码算法

为抵抗水声信道的传输差错，提出了一种具有较高抗误码能力的水下图像高效编码算法。该算法根据水下图像的特点，对图像进行小波变换预处理以去除其中的视觉冗余。对低频系数采用定长量化编码；对重要高频系数采用数值和位置独立编码的方案，其中对重要高频系数的数值提出了变精度定长量化编码方法，而对重要高频系数的位置采用基于位置差降的可逆变长编码算法。为抵抗水声信道的传输差错，提出了合理的分割、交织策略和变长编码块相对定长信道包的存放策略；对低频和高频系数，分别提出了相应的差错检测和掩盖算法。实验结果表明，提出的算法不仅具有较高的压缩效率，而且具有较高的抗误码能力，满足了水声信道传输图像的要求。

Efficient underwater image coding algorithm suitable for underwater acousticchannel transmission.

An efficient and error resilient underwater image coding algorithm is presented to resist the transmission errors of the under- water acoustic channels. The visual redundancy of underwater images is removed by a wavelet-based preprocessing technique according to the characteristics of underwater images. The low frequency coefficients are quantized and encoded by a fixed length algorithm, and the values and their corresponding positions of the important high frequency coefficients are coded separately, where the values are coded by a variable precision and fixed length algorithm, and their corresponding positions are coded by a position difference reduction-based RVLC （Reversible and Variable Length Coding） algorithm. Moreover, a packing and interleaving scheme and a placing scheme of the variable length coding blocks with respect to the fixed length acoustic channel packets are proposed to resist the transmission errors of the underwater acoustic channels. Error detection and concealment algorithms for low and high frequency coefficients are presented respectively. The experimental results show that the proposed coding algorithm provides both high coding efficiency and high error resilient performance, thus meetim, the reauirement of underwater image,e transmission via underwater acoustic channels.