TokenPacker: Efficient Visual Projector for Multimodal LLM
Authors: name: Wentong Li, name: Yuqian Yuan, name: Jian Liu, name: Dongqi Tang, name: Song Wang, name: Jianke Zhu, name: Lei Zhang

The visual projector serves as an essential bridge between the visual encoder
and the Large Language Model (LLM) in a Multimodal LLM (MLLM). Typically, MLLMs
adopt a simple MLP to preserve all visual contexts via one-to-one
transformation. However, the visual tokens are redundant and can be
considerably increased when dealing with high-resolution images, impairing the
efficiency of MLLMs significantly. Some recent works have introduced resampler
or abstractor to reduce the number of resulting visual tokens. Unfortunately,
they fail to capture finer details and undermine the visual reasoning
capabilities of MLLMs. In this work, we propose a novel visual projector, which
adopts a coarse-to-fine scheme to inject the enriched characteristics to
generate the condensed visual tokens. In specific, we first interpolate the
visual features as a low-resolution point query, providing the overall visual
representation as the foundation. Then, we introduce a region-to-point
injection module that utilizes high-resolution, multi-level region-based cues
as fine-grained reference keys and values, allowing them to be fully absorbed
within the corresponding local context region. This step effectively updates
the coarse point query, transforming it into an enriched one for the subsequent
LLM reasoning. Extensive experiments demonstrate that our approach compresses
the visual tokens by 75%~89%, while achieves comparable or even better
performance across diverse benchmarks with significantly higher efficiency. The
source codes can be found at https://github.com/CircleRadon/TokenPacker.