  Recent studies made great progress in video matting by extending the success
of trimap-based image matting to the video domain. In this paper, we push this
task toward a more practical setting and propose One-Trimap Video Matting
network (OTVM) that performs video matting robustly using only one
user-annotated trimap. A key of OTVM is the joint modeling of trimap
propagation and alpha prediction. Starting from baseline trimap propagation and
alpha prediction networks, our OTVM combines the two networks with an
alpha-trimap refinement module to facilitate information flow. We also present
an end-to-end training strategy to take full advantage of the joint model. Our
joint modeling greatly improves the temporal stability of trimap propagation
compared to the previous decoupled methods. We evaluate our model on two latest
video matting benchmarks, Deep Video Matting and VideoMatting108, and
outperform state-of-the-art by significant margins (MSE improvements of 56.4%
and 56.7%, respectively). The source code and model are available online:
https://github.com/Hongje/OTVM.
