Global Motion Assisted Low Complexity Video Encoding for UAV Applications

We design a video encoding scheme that is suited for applications such as unmanned aerial vehicle (UAV) video surveillance where the encoder complexity needs to be low. Our low complexity encoder predicts frames using the global motion information available in UAVs and thus achieves lower complexity and more than 40% BD-rate savings for fly-over videos compared to a complexity-constrained H.264 encoder with motion estimation restricted to 8 x 8 blocks and half pixel accuracy. We also incorporate a spectral entropy based bit allocation scheme into this encoder to achieve near constant quality within groups of pictures (GOPs) at the cost of small increases in delay and complexity, and a small drop in compression efficiency. Both these encoders with their corresponding low complexity "matched" decoders provide significant gains of more than 49% BD-rate savings over the Wyner-Ziv based DISCOVER codec which has a low complexity encoder and a high complexity decoder. Furthermore, for videos where the global motion is spatially consistent within 2 x 2 blocks, we show that the computational complexity of these proposed encoders can be significantly reduced with only about 1% BD-rate increase.