I. Introduction
As front-facing cameras become popular on personal devices (e.g., laptops, tablets, and smart phones), recent years have witnessed a skyrocketing growth of video conferencing (VC) systems on those devices. According to Cisco, the number of video conferencing users is growing at an annual rate of 51.7% and will surpass that of audio conferencing users by 2015 [2]. Another trend has been the advocation of cloud computing services in multi-party VC systems, to overcome the constraints of user devices and boosting the conferencing experience by employing the rich and on-demand resources provided by a geo-distributed cloud platform.