Fugue : Time scales of adaptation in mobile video

Providing interactive video on hand-held, mobile devices is extremely difficult. These devices are subject to processor, memory, and power constraints, and communicate over wireless links of rapidly varying quality. Furthermore, the size of encoded video is difficult to predict, complicating the encoding task. We present Fugue, a system that copes with these challenges through a division along time scales of adaptation. Fugue is structured as three separate controllers: transmission, video, and preference. This decomposition provides adaptation along different time scales: per-packet, per-frame, and per-video. The controllers are provided at modest time and space costs compared to the cost of video encoding. We present simulations confirming the efficacy of our transmission controller, and compare our video controller to several alternatives. We find that, in situations amenable to adaptive compression, our scheme provides video quality equal to or better than the alternatives at a comparable or substantially lower computational cost. We also find that distortion, the metric commonly used to compare mobile video, under-values the contribution smooth motion makes to perceived video quality.