运载火箭飞行状态图像箭上实时压缩技术研究

图像信息是火箭性能评估和故障分析的重要依据.提出了基于遥测信道获取飞行图像的系统方案并完成了箭上图像压缩器开发.设计了具有自适应Ⅰ帧强制插入机制的编码器结构,有效地解决了飞行异常场景突变时图像质量下降的问题.提出了结合绝对误差的自适应阈值全零块检测算法,提高了全零块检测率却不增加运算量;提出了基于全零块的快速模式匹配算法,有效降低了模式预测计算量.试验表明:提出的系统方案及开发的压缩器能利用现有遥测信道实时获取图像,提出的图像压缩算法使编码速度提高约30%-45%且图像质量基本不变(与JM13.2比),强制插入Ⅰ帧机制启动时未出现图像质量明显下降和丢帧问题.

Onboard real-time compression of launch vehicle telemetry images

Image information plays a very important role in fault diagnosis for launch vehicles.A video surveillance sub-system based on the present wireless communication system is designed and its corresponding on-board encoder is developed.To prevent from video-quality degradation and the losing frames problem caused by unexpected scene changes during flight tests,an optimal encoder framework is presented which could detect scene changes while encoding,and only I frames are encoded whenever the scenes change rapidly.Two algorithms are also proposed for reducing the computation cost of H.264.The first is a novel all-zero DCT block detecting algorithm which could improve detection efficiency without any additional computational cost by combining sum of absolute difference with adaptive detection thresholds in table.The second is a fast mode-selection algorithm which could early terminate the mode selecting operation by regarding all-zero DCT block as the best one.Experiments show that the proposed algorithms can achieve approximately a 30%-45% computational saving and almost the same PSNR compared with JM13.2,and the encoder can fulfill the requirement of real-time encoding(25f/s).Moreover,both lost frames and video-quality degradation do not occur when unexpected scene changes appear.