ActiveEye: Enabling Continuous and Responsive Video Understanding for Smart Eyewear Systems

Integrating vision-language models (VLMs) with wearable devices offers great potential for continuous and responsive video understanding, a key capability for applications such as smart eyewear-based conversational assistants. However, achieving this on resource-constrained devices is challenging due to the high energy demands of continuous spatial-temporal sampling and transmission. We propose ActiveEye , a VLM designed for energy-efficient and responsive video understanding. ActiveEye separates visual and motion semantic representations and incorporates an active perception-based feedback path to adaptively adjust spatial-temporal sampling and transmission rates. Implemented as a wearable-mobile-cloud system, ActiveEye is evaluated for energy efficiency, real-time semantic change detection, and video understanding in both laboratory and field studies. Using the EgoSchema dataset, ActiveEye reduces the front-end energy consumption by 49.14%, supporting 8.37 hours of continuous operation on a 2.1 Wh battery. It achieves the highest F1 score (0.80) and the lowest average time difference (1.30 s) compared with heuristic-based event detection algorithms, validating its timely semantic detection. Furthermore, ActiveEye achieves a visual question answering (VQA) accuracy of 61.6%, which is comparable to state-of-the-art VLM agents, despite their reliance on larger language decoders and more computationally intensive frame selection strategies. Two rounds of in-field user evaluations further confirm its effectiveness in real-world settings, demonstrating its practical viability as a continuous and responsive video understanding system, conversational assistant, and wearable companion.