Eventful Transformers: Leveraging Temporal Redundancy in Vision Transformers

Vision Transformers achieve impressive accuracy across a range of visual recognition tasks. Unfortunately, their accuracy frequently comes with high computational costs. This is a particular issue in video recognition, where models are often applied repeatedly across frames or temporal chunks. In this work, we exploit temporal redundancy between subsequent inputs to reduce the cost of Transformers for video processing. We describe a method for identifying and re-processing only those tokens that have changed significantly over time. Our proposed family of models, Eventful Transformers, can be converted from existing Transformers (often without any re-training) and give adaptive control over the compute cost at runtime. We evaluate our method on large-scale datasets for video object detection (ImageNet VID) and action recognition (EPIC-Kitchens 100). Our approach leads to significant computational savings (on the order of 2-4x) with only minor reductions in accuracy.

Event Neural Networks

Video data is often repetitive; for example, the content of adjacent frames is usually strongly correlated. Such repetition occurs at multiple levels of complexity, from low-level pixel values to textures and high-level semantics. We propose Event Neural Networks (EvNets), a novel class of networks that leverage this repetition to achieve considerable computation savings for video inference tasks. A defining characteristic of EvNets is that each neuron has state variables that provide it with long-term memory, which allows low-cost inference even in the presence of significant camera motion. We show that it is possible to transform virtually any conventional neural into an EvNet. We demonstrate the effectiveness of our method on several state-of-the-art neural networks for both high- and low-level visual processing, including pose recognition, object detection, optical flow, and image enhancement. We observe up to an order-of-magnitude reduction in computational costs (2-20x) as compared to conventional networks, with minimal reductions in model accuracy.