  The Depth-aware Video Panoptic Segmentation (DVPS) is a new challenging
vision problem that aims to predict panoptic segmentation and depth in a video
simultaneously. The previous work solves this task by extending the existing
panoptic segmentation method with an extra dense depth prediction and instance
tracking head. However, the relationship between the depth and panoptic
segmentation is not well explored -- simply combining existing methods leads to
competition and needs carefully weight balancing. In this paper, we present
PolyphonicFormer, a vision transformer to unify these sub-tasks under the DVPS
task and lead to more robust results. Our principal insight is that the depth
can be harmonized with the panoptic segmentation with our proposed new paradigm
of predicting instance level depth maps with object queries. Then the
relationship between the two tasks via query-based learning is explored. From
the experiments, we demonstrate the benefits of our design from both depth
estimation and panoptic segmentation aspects. Since each thing query also
encodes the instance-wise information, it is natural to perform tracking
directly with appearance learning. Our method achieves state-of-the-art results
on two DVPS datasets (Semantic KITTI, Cityscapes), and ranks 1st on the
ICCV-2021 BMTT Challenge video + depth track. Code is available at
https://github.com/HarborYuan/PolyphonicFormer .
