  The high-accuracy and resource-intensive deep neural networks (DNNs) have
been widely adopted by live video analytics (VA), where camera videos are
streamed over the network to resource-rich edge/cloud servers for DNN
inference. Common video encoding configurations (e.g., resolution and frame
rate) have been identified with significant impacts on striking the balance
between bandwidth consumption and inference accuracy and therefore their
adaption scheme has been a focus of optimization. However, previous
profiling-based solutions suffer from high profiling cost, while existing deep
reinforcement learning (DRL) based solutions may achieve poor performance due
to the usage of fixed reward function for training the agent, which fails to
craft the application goals in various scenarios. In this paper, we propose
ILCAS, the first imitation learning (IL) based configuration-adaptive VA
streaming system. Unlike DRL-based solutions, ILCAS trains the agent with
demonstrations collected from the expert which is designed as an offline
optimal policy that solves the configuration adaption problem through dynamic
programming. To tackle the challenge of video content dynamics, ILCAS derives
motion feature maps based on motion vectors which allow ILCAS to visually
``perceive'' video content changes. Moreover, ILCAS incorporates a cross-camera
collaboration scheme to exploit the spatio-temporal correlations of cameras for
more proper configuration selection. Extensive experiments confirm the
superiority of ILCAS compared with state-of-the-art solutions, with 2-20.9%
improvement of mean accuracy and 19.9-85.3% reduction of chunk upload lag.
