Energy-efficient design of an always-on smart visual trigger

In this work, we present the design of an always-on smart visual trigger. To maximize the energy-efficiency, the whole system is kept in stand-by mode until a significant information is detected by the early-processing of the low-power imager. Within two considered scenarios of vehicle detection, the system runs at minimal power consumption for 84% and 39% of the time. When active, the generation of triggers due to relevant events is conducted by analyzing the trajectory of multiple tracked objects. A parallel event-driven implementation speeds-up the digital computation and leads to a duty cycle below 1% over the frame period. The optimized power management is enabled by defining an always-on camera interface for the System-on-Chip (SoC) processor, which is able to individually activate both the sensor and the processor while running at minimal power consumption. In the considered case-study of vehicle detection, an estimated power consumption of up to 23μW is accounted, depending on the context-activity, and the smart triggers fails one detection over 72 moving vehicles.