Mobile video calls are widely used to share information about real-world objects and environments with remote collaborators. While these calls provide valuable visual context in real time, the experience of interacting with people and moving around a space is significantly reduced when compared to co-located conversations. Recent work has demonstrated the potential of Mobile Augmented Reality applications to enable more spatial forms of collaboration across distance. To better understand the dynamics of mobile AR collaboration and how this medium compares against the status quo, we conducted a comparative structured observation study to analyze people's perception of space and interaction with remote collaborators across mobile video calls and AR-based calls. Fourteen pairs of participants completed a spatial collaboration task using each medium. Through a mixed-methods analysis of session videos, transcripts, motion logs, post-task exercises, and interviews, we highlight how the choice of medium influences the roles and responsibilities that collaborators take on and the construction of a shared language for coordination. We discuss the importance of spatial reasoning with one's body, how video calls help participants "be on the same page" more directly, and how AR calls enable both onsite and remote collaborators to engage with the space and each other in ways that resemble in-person interaction. Our study offers a nuanced view of the benefits and limitations of both mediums, and we conclude with a discussion of design implications for future systems that integrate mobile video and AR to better support spatial collaboration in its many forms.

翻译：移动视频通话被广泛用于与远程协作者共享现实世界物体和环境的信息。尽管这些通话能实时提供宝贵的视觉背景，但与共处一地的对话相比，其人际互动与空间移动的体验显著受限。近期研究揭示了移动增强现实应用在实现跨距离空间协作形态方面的潜力。为深入理解移动增强现实协作的动态特性及其与现有媒介的差异，我们开展了一项对比性结构化观察研究，以分析人们在移动视频通话和基于增强现实的通话中对空间的感知及与远程协作者的交互行为。十四组参与者分别使用两种媒介完成了空间协作任务。通过对会话视频、转录文本、运动日志、任务后练习及访谈的混合方法分析，我们揭示了媒介选择如何影响协作者承担的角色与责任，以及协调性共享语言的构建过程。我们探讨了身体空间推理的重要性，阐释了视频通话如何更直接地帮助参与者"达成共识"，并说明增强现实通话如何使现场与远程协作者能以近似面对面互动的方式融入空间并实现彼此交互。本研究对两种媒介的优势与局限提出了细致见解，最后讨论了未来整合移动视频与增强现实的系统设计启示，以更好地支持多种形态的空间协作。