Visual Question Answering Models for Zero-Shot Pedestrian Attribute Recognition: A Comparative Study

Pedestrian Attribute Recognition (PAR) poses a significant challenge in developing automatic systems that enhance visual surveillance and human interaction. In this study, we investigate using Visual Question Answering (VQA) models to address the zero-shot PAR problem. Inspired by the impressive results achieved by a zero-shot VQA strategy during the PAR Contest at the 20th International Conference on Computer Analysis of Images and Patterns in 2023, we conducted a comparative study across three state-of-the-art VQA models, two of them based on BLIP-2 and the third one based on the Plug-and-Play VQA framework. Our analysis focuses on performance, robustness, contextual question handling, processing time, and classification errors. Our findings demonstrate that both BLIP-2-based models are better suited for PAR, with nuances related to the adopted frozen Large Language Model. Specifically, the Open Pre-trained Transformers based model performs well in benchmark color estimation tasks, while FLANT5XL provides better results for the considered binary tasks. In summary, zero-shot PAR based on VQA models offers highly competitive results, with the advantage of avoiding training costs associated with multipurpose classifiers.