Improving Image Captioning via Enhancing Dual-Side Context Awareness

Abstract

Recent work on visual question answering demonstrate that grid features can work as well as region feature on vision language tasks. In the meantime, transformer-based model and its variants have shown remarkable performance on image captioning. However, the object-contextual information missing caused by the single granularity nature of grid feature on the encoder side, as well as the future contextual information missing due to the left2right decoding paradigm of transformer decoder, remains unexplored. In this work, we tackle these two problems by enhancing contextual information at dual-side:(i) at encoder side, we propose Context-Aware Self-Attention module, in which the key/value is expanded with adjacent rectangle region where each region contains two or more aggregated grid features; this enables grid feature with varying granularity, storing adequate contextual information for object with different scale. (ii) at decoder side, we incorporate a dual-way decoding strategy, in which left2right and right2left decoding are conducted simultaneously and interactively. It utilizes both past and future contextual information when generates current word. Combining these two modules with a vanilla transformer, our Context-Aware Transformer(CATNet) achieves a new state-of-the-art on MSCOCO benchmark.