Video action recognition, a critical problem in video understanding, has been
gaining increasing attention. To identify actions induced by complex
object-object interactions, we need to consider not only spatial relations
among objects in a single frame, but also temporal relations among different or
the same objects across multiple frames. However, existing approaches that
model video representations and non-local features are either incapable of
explicitly modeling relations at the object-object level or unable to handle
streaming videos. In this paper, we propose a novel dynamic hidden graph module
to model complex object-object interactions in videos, of which two
instantiations are considered: a visual graph that captures appearance/motion
changes among objects and a location graph that captures relative
spatiotemporal position changes among objects. Additionally, the proposed graph
module allows us to process streaming videos, setting it apart from existing
methods. Experimental results on benchmark datasets, Something-Something and
ActivityNet, show the competitive performance of our method.

本文提出了基于动态隐藏图模块的视频动作识别方法，该模块既可以捕捉多对象间的外观 / 运动变化，又能捕捉他们的时空关系，该方法具有处理流式视频数据的能力，并在 Something-Something 和 ActivityNet 数据集上取得了竞争性的性能。

基于动态图模块的对象交互建模在活动识别中的应用

Dynamic Graph Modules for Modeling Object-Object Interactions in  Activity Recognition

Current approaches to semantic image and scene understanding typically employ
rather simple object representations such as 2D or 3D bounding boxes. While
such coarse models are robust and allow for reliable object detection, they
discard much of the information about objects' 3D shape and pose, and thus do
not lend themselves well to higher-level reasoning. Here, we propose to base
scene understanding on a high-resolution object representation. An object class
- in our case cars - is modeled as a deformable 3D wireframe, which enables
fine-grained modeling at the level of individual vertices and faces. We augment
that model to explicitly include vertex-level occlusion, and embed all
instances in a common coordinate frame, in order to infer and exploit
object-object interactions. Specifically, from a single view we jointly
estimate the shapes and poses of multiple objects in a common 3D frame. A
ground plane in that frame is estimated by consensus among different objects,
which significantly stabilizes monocular 3D pose estimation. The fine-grained
model, in conjunction with the explicit 3D scene model, further allows one to
infer part-level occlusions between the modeled objects, as well as occlusions
by other, unmodeled scene elements. To demonstrate the benefits of such
detailed object class models in the context of scene understanding we
systematically evaluate our approach on the challenging KITTI street scene
dataset. The experiments show that the model's ability to utilize image
evidence at the level of individual parts improves monocular 3D pose estimation
w.r.t. both location and (continuous) viewpoint.

本文提出了一种基于 3D 可变形线框的高分辨率车辆对象表示，该表示能精细地建模单个点和面的水平，结合此表示和明确的 3D 场景模型，我们能够对场景进行更细致和准确的理解并从单个视角评估多个对象的位置与视点的单眼 3D 姿态估计。