无人机机载侦察视频的高效视频码率控制

提出了一种基于缓冲区状态及梯度算子的低延时高效视频码(HEVC)率控制方法,以解决现有的码率控制算法在无人机机载侦察系统中因比特分配不当引起的视频质量较差的问题。首先,利用剩余比特及缓冲区状态预分配帧层目标比特;然后,以视频中每帧各最大编码单元(LCU)的时空复杂度作为权重,预分配各LCU的目标比特;最后,通过R-λ模型获得目标比特下的编码参数,实现视频压缩编码,并完成模型参数更新。实验结果表明:在8 Mbps的带宽下,提出的算法使码率控制误差缩小到HM16.0的2/5,视频中图像质量波动范围降低到HM16.0的1/4以内。提出的方法有效抑制了帧间比特消耗波动,使得缓冲区占用量能在小范围内平稳波动,图像主观质量也得到了改善,更好地满足了机载侦察系统低延时的应用需求。

HEVC rate control for unmanned aerial vehicle airborne reconnaissance

A High Efficiency Video Coding (HEVC) rate control algorithm with a low-delay was proposed based on buffer status and a gradient operator to improve the poor video quality of the current HEVC rate control scheme caused by the improper bit allocation in Unmanned Aerial Vehicle (UAV) airborne reconnaissance. First, both the buffer state and the remained bits were used to pre-allocate the frame layer target bits. Then, the time and space complexity of the Largest Coding Unit (LCU) in each frame was taken as the weight, layer bits hierarchically with the reconnaissance video features was evaluated by a gradient value. Finally, Quantization Parameter (QP) was derived from R-λ model, the encoder in the LCU and the model parameter updating were implemented. Experimental results show that the proposed algorithm reduces mismatch ratio to 2/5 that of the rate control scheme in HM16.0, and PSNR (Peak Signal-to-noise Ratio) fluctuation has been within 1/4 under the 8 Mbps bandwidth. Moreover, the proposed algorithm provides an improvement in subjective quality evaluation and has less bit fluctuation and lower, steadier buffer occupancy, which enables a lower delay of aerial photography applications.