  Multimodal learning aims to build models that can process and relate
information from multiple modalities. Despite years of development in this
field, it still remains challenging to design a unified network for processing
various modalities ($\textit{e.g.}$ natural language, 2D images, 3D point
clouds, audio, video, time series, tabular data) due to the inherent gaps among
them. In this work, we propose a framework, named Meta-Transformer, that
leverages a $\textbf{frozen}$ encoder to perform multimodal perception without
any paired multimodal training data. In Meta-Transformer, the raw input data
from various modalities are mapped into a shared token space, allowing a
subsequent encoder with frozen parameters to extract high-level semantic
features of the input data. Composed of three main components: a unified data
tokenizer, a modality-shared encoder, and task-specific heads for downstream
tasks, Meta-Transformer is the first framework to perform unified learning
across 12 modalities with unpaired data. Experiments on different benchmarks
reveal that Meta-Transformer can handle a wide range of tasks including
fundamental perception (text, image, point cloud, audio, video), practical
application (X-Ray, infrared, hyperspectral, and IMU), and data mining (graph,
tabular, and time-series). Meta-Transformer indicates a promising future for
developing unified multimodal intelligence with transformers. Code will be
available at https://github.com/invictus717/MetaTransformer
