When Tokens Talk Too Much: A Survey of Multimodal Long-Context Token
  Compression across Images, Videos, and Audios
Authors: name: Kele Shao, name: Keda Tao, name: Kejia Zhang, name: Sicheng Feng, name: Mu Cai, name: Yuzhang Shang, name: Haoxuan You, name: Can Qin, name: Yang Sui, name: Huan Wang
Organization: Westlake University

Multimodal large language models (MLLMs) have made remarkable strides,
largely driven by their ability to process increasingly long and complex
contexts, such as high-resolution images, extended video sequences, and lengthy
audio input. While this ability significantly enhances MLLM capabilities, it
introduces substantial computational challenges, primarily due to the quadratic
complexity of self-attention mechanisms with numerous input tokens. To mitigate
these bottlenecks, token compression has emerged as an auspicious and critical
approach, efficiently reducing the number of tokens during both training and
inference. In this paper, we present the first systematic survey and synthesis
of the burgeoning field of multimodal long context token compression.
Recognizing that effective compression strategies are deeply tied to the unique
characteristics and redundancies of each modality, we categorize existing
approaches by their primary data focus, enabling researchers to quickly access
and learn methods tailored to their specific area of interest: (1)
image-centric compression, which addresses spatial redundancy in visual data;
(2) video-centric compression, which tackles spatio-temporal redundancy in
dynamic sequences; and (3) audio-centric compression, which handles temporal
and spectral redundancy in acoustic signals. Beyond this modality-driven
categorization, we further dissect methods based on their underlying
mechanisms, including transformation-based, similarity-based, attention-based,
and query-based approaches. By providing a comprehensive and structured
overview, this survey aims to consolidate current progress, identify key
challenges, and inspire future research directions in this rapidly evolving
domain. We also maintain a public repository to continuously track and update
the latest advances in this promising area.