  Due to the limited scale and quality of video-text training corpus, most
vision-language foundation models employ image-text datasets for pretraining
and primarily focus on modeling visually semantic representations while
disregarding temporal semantic representations and correlations. To address
this issue, we propose COSA, a COncatenated SAmple pretrained vision-language
foundation model. COSA jointly models visual contents and event-level temporal
cues using only image-text corpora. We achieve this by sequentially
concatenating multiple image-text pairs as inputs for pretraining. This
transformation effectively converts existing image-text corpora into a pseudo
long-form video-paragraph corpus, enabling richer scene transformations and
explicit event-description correspondence. Extensive experiments demonstrate
that COSA consistently improves performance across a broad range of downstream
tasks, including long-form/short-form video-text tasks and image-text tasks
such as retrieval, captioning, and question answering. Notably, COSA achieves
state-of-the-art results on various competitive benchmarks. Code and model are
released at https://github.com/TXH-mercury/COSA.
