  Video Referring Expression Comprehension (REC) aims to localize a target
object in videos based on the queried natural language. Recent improvements in
video REC have been made using Transformer-based methods with learnable
queries. However, we contend that this naive query design is not ideal given
the open-world nature of video REC brought by text supervision. With numerous
potential semantic categories, relying on only a few slow-updated queries is
insufficient to characterize them. Our solution to this problem is to create
dynamic queries that are conditioned on both the input video and language to
model the diverse objects referred to. Specifically, we place a fixed number of
learnable bounding boxes throughout the frame and use corresponding region
features to provide prior information. Also, we noticed that current query
features overlook the importance of cross-modal alignment. To address this, we
align specific phrases in the sentence with semantically relevant visual areas,
annotating them in existing video datasets (VID-Sentence and VidSTG). By
incorporating these two designs, our proposed model (called ConFormer)
outperforms other models on widely benchmarked datasets. For example, in the
testing split of VID-Sentence dataset, ConFormer achieves 8.75% absolute
improvement on<EMAIL_ADDRESS>compared to the previous state-of-the-art model.
