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为满足水声信道有限带宽的要求,提出了一种高效的水下视频图像压缩编码方案。编码系统主要由图像预处理、帧内编码和帧间预测编码3个模块组成。基于小波变换的预处理模块用于去除水下图像中的视觉冗余。根据水下图像的特点,采用基于小波树的WDR(wavelet difference reduction)算法对帧内图像进行高效编码。帧间运动估计和补偿是针对预处理后的图像子带进行,运动补偿后的残差图像采用基于重要子块和重要系数的双重WDR编码策略。实验结果表明:在保证图像重建质量的前提下,本文算法的平均压缩比可以达到250∶1～500∶1,基本满足水声信道传输速率为16 Kbps时的要求。
In order to meet the requirement of the limited bandwidth of underwater acoustic channel, an efficient underwater video compression scheme is proposed. The coding system is mainly composed of three modules: image pre-processing, intra-frame coding and inter-frame predictive coding. Pretreatment Module Based on Wavelet Transform Used to Remove Visual Redundancy in Underwater Image. According to the characteristics of underwater images, WDR (wavelet difference reduction) algorithm based on wavelet tree is used to efficiently encode intra-frame images. Interframe motion estimation and compensation are performed on pre-processed image subbands. The motion-compensated residual image adopts a dual WDR coding strategy based on important sub-blocks and significant coefficients. The experimental results show that the average compression ratio of the proposed algorithm can reach 250: 1 ~ 500: 1 under the premise of guaranteeing the quality of image reconstruction, which basically meets the requirements of underwater acoustic channel transmission rate of 16 Kbps.