  Visual language models (VLMs) rapidly progressed with the recent success of
large language models. There have been growing efforts on visual instruction
tuning to extend the LLM with visual inputs, but lacks an in-depth study of the
visual language pre-training process, where the model learns to perform joint
modeling on both modalities. In this work, we examine the design options for
VLM pre-training by augmenting LLM towards VLM through step-by-step
controllable comparisons. We introduce three main findings: (1) freezing LLMs
during pre-training can achieve decent zero-shot performance, but lack
in-context learning capability, which requires unfreezing the LLM; (2)
interleaved pre-training data is beneficial whereas image-text pairs alone are
not optimal; (3) re-blending text-only instruction data to image-text data
during instruction fine-tuning not only remedies the degradation of text-only
tasks, but also boosts VLM task accuracy. With an enhanced pre-training recipe
we build VILA, a Visual Language model family that consistently outperforms the
state-of-the-art models, e.g., LLaVA-1.5, across main benchmarks without bells
and whistles. Multi-modal pre-training also helps unveil appealing properties
of VILA, including multi-image reasoning, enhanced in-context learning, and
better world knowledge.
