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Abstract

Mobile vision systems would benefit from the ability to situationally sacrifice image resolution to save system energy when imaging detail is unnecessary. Unfortunately, any change in sensor resolution leads to a substantial pause in frame delivery -- as much as 280 ms. Frame delivery is bottlenecked by a sequence of reconfiguration procedures and memory management in current operating systems before it resumes at the new resolution. This latency from reconfiguration impedes the adoption of otherwise beneficial resolution-energy tradeoff mechanisms. We propose Banner as a media framework that provides a rapid sensor resolution reconfiguration service as a modification to common media frameworks, e.g., V4L2. Banner completely eliminates the frame-to-frame reconfiguration latency (226 ms to 33 ms), i.e., removing the frame drop during sensor resolution reconfiguration. Banner also halves the end-to-end resolution reconfiguration latency (226 ms to 105 ms). This enables a more than 49% reduction of system power consumption by allowing continuous vision applications to reconfigure the sensor resolution to 480p compared with downsampling from 1080p to 480p, as measured in a cloud-based offloading workload running on a Jetson TX2 board. As a result, Banner unlocks unprecedented capabilities for mobile vision applications to dynamically reconfigure sensor resolutions to balance the energy efficiency and task accuracy tradeoff.