Low Delay

Cellular links often present highly-varying network bandwidth and packet delays that can cause the video frames to be excessively delayed, destroying the interactivity of the video call. This paper presents Rebera, a cross-layer design of proactive congestion control, video encoding and rate adaptation. Rebera actively measures the available bandwidth in real-time by employing the video frames as packet trains. Using an online linear adaptive filter, Rebera makes a history-based prediction of the future capacity, and determines a bit budget for the video rate adaptation. Our experiments with real cellular link traces demonstrate Rebera can deliver higher bandwidth utilization and shorter packet delays than Apple’s FaceTime. Our work has been adopted in recent release of WeChat, #1 social media app in China, improving video call quality.