Consider the following scenario:
You have a Microsoft Windows 8.1-based device that has Microsoft Lync 2013 installed.
You start a Lync 2013 video conference on the device.
You try to rotate the device to change the screen orientation from landscape orientation to portrait orientation in the conference.
In this scenario, all programs that are running on the device are changed to portrait orientation. However, the video window in the Lync 2013 video conference is still in landscape orientation.
To resolve this issue, install the following service pack:
2817430 Description of Microsoft Office 2013 Service Pack 1 (SP1)