A DM642-Based Underwater Video Coding System

Underwater video systems have assumed an increasingly important role in exploration and survey of the unknown deep ocean environments. This paper presents a real-time underwater video compression system that can be mounted on autonomous underwater vehicles (AUVs) for underwater survey applications. The hardware system is based on the digital media processor TMS320DM642 (DM642) of Texas Instruments, and is mainly composed of the frame-grabber, the DM642 based processing unit, and several interfaces for display and communications. According to the characteristics of underwater video, a very low-bit-rate coding algorithm has been developed, which is composed of three modules, namely, the wavelet-based preprocessing technique, the efficient intra-frame coding algorithm based on modified Wavelet Difference Reduction (WDR), and the inter-frame coding algorithm based on double WDR. In addition, some code optimizing measures are described for the video coding algorithms to efficiently operate on the DM642 based hardware system. The experimental results show that while maintaining the acceptable quality of the reconstructed images, the proposed underwater video-coding algorithm can provide average compression ratios from 250:1 to 400:1, and the DM642 based system exhibits a real-time coding performance of greater than 25 frames per second, thereby meeting the requirement of transmission and storage.