Remote video file synchronization for heterogeneous mobile clients

Abstract

Bandwidth-efficient video file synchronization between remote clients is an important task. When heterogeneous mobile clients want to synchronize their local video data to that of a remote party at a desired resolution and distortion level, it is wasteful and unnecessary to retransmit the entire video data, especially when the differences are minor while the clients are limited in transmission bandwidth. We present VSYNC (video-sync), an incremental video file synchronization protocol that automatically detects and transmits differences between the video files without prior knowledge of what is different. VSYNC generalizes the popular universal file synchronization tool rsync to a semantics-aware utility that handles synchronization of video data. An important attribute of VSYNC is that it allows synchronization to within some quantitative distortion constraint. VSYNC can be easily embedded in a codec or transcoder, and can be used to synchronize videos encoded with different parameters or stored in different, possibly proprietary, formats. A hierarchical hashing scheme is designed to compare the video content at the remote ends, while a lossy distributed video coding framework is used to realize compression gains in the update steps. Experimental results of three heterogeneous mobile clients synchronizing to an updated video file at the remote server validate the performance gains in rate-savings attained by VSYNC compared to directly sending the updated video files using H.26x or synchronizing using universal file synchronization protocols such as rsync.