  In recent years, significant progress has been made in video instance
segmentation (VIS), with many offline and online methods achieving
state-of-the-art performance. While offline methods have the advantage of
producing temporally consistent predictions, they are not suitable for
real-time scenarios. Conversely, online methods are more practical, but
maintaining temporal consistency remains a challenging task. In this paper, we
propose a novel online method for video instance segmentation, called TCOVIS,
which fully exploits the temporal information in a video clip. The core of our
method consists of a global instance assignment strategy and a spatio-temporal
enhancement module, which improve the temporal consistency of the features from
two aspects. Specifically, we perform global optimal matching between the
predictions and ground truth across the whole video clip, and supervise the
model with the global optimal objective. We also capture the spatial feature
and aggregate it with the semantic feature between frames, thus realizing the
spatio-temporal enhancement. We evaluate our method on four widely adopted VIS
benchmarks, namely YouTube-VIS 2019/2021/2022 and OVIS, and achieve
state-of-the-art performance on all benchmarks without bells-and-whistles. For
instance, on YouTube-VIS 2021, TCOVIS achieves 49.5 AP and 61.3 AP with
ResNet-50 and Swin-L backbones, respectively. Code is available at
https://github.com/jun-long-li/TCOVIS.
