A Simple Recipe for Contrastively Pre-training Video-First Encoders Beyond 16 Frames

Understanding long real-world videos requires modeling of long-range visual dependencies. To this end we explore video-first architectures building on the common paradigm of transferring large-scale image--text models to video via shallow temporal fusion. However we expose two limitations to the approach: (1) decreased spatial capabilities likely due to poor video--language alignment in standard video datasets and (2) higher memory consumption bottlenecking the number of frames that can be processed. To mitigate the memory bottleneck we systematically analyze the memory/accuracy trade-off of various efficient methods: factorized attention parameter-efficient image-to-video adaptation input masking and multi-resolution patchification. Surprisingly simply masking large portions of the video (up to 75%) during contrastive pre-training proves to be one of the most robust ways to scale encoders to videos up to 4.3 minutes at 1 FPS. Our simple approach for training long video-to-text models which scales to 1B parameters does not add new architectural complexity and is able to outperform the popular paradigm of using much larger LLMs as an information aggregator over segment-based information on benchmarks with long-range temporal dependencies (YouCook2 EgoSchema).