Research Projects

VSYNC --- A Novel Video File Synchronization Protocol

*** THIS PROJECT IS NO LONGER ACTIVE ***

Hao Zhang, Chuohao Yeo and Kannan Ramchandran

Video file synchronization between remote users is an important task in applications such as remote video editing. Retransmission of a video file that has been modified only slightly, for the purpose of synchronization with a remote-end copy, is extremely expensive but avoidable. While tools such as rsync have been widely used for exact bit-stream synchronization of files and directories between remote locations, they are not effective with compressed video. Such content-agnostic approaches fail because a minor modification of video could result in a complete different compressed bitstream. We are investigating a novel approach for performing incremental video file synchronization on two video files at remote ends up to a user specified distortion constraint through a bi-directional communications link . Our method, which we name VSYNC (for video synchronization), is designed to automatically detect and transmit changes in the modified video file without the knowledge of what was changed. A hierarchical hashing scheme is designed to compare video chunks, converting the high-level content information to a low-level hash stream that is more amenable to the tools of coding theory. Our preliminary results [1] show impressive gains in transmission rate-savings. In a typical example of two 12s video files with about 10% of the frames being edited, transmission savings of 44% to 87% can be obtained compared to directly sending the updated video files using H.264 and rsync. We are now extending the work in [1] by re-designing the hashing scheme in order to transmit modifications on a more spatially fine-grained basis. We are also investigating the use of distributed video coding techniques to exploit correlation between remote copies for an additional rate rebate.

[1]
Hao Zhang, Chuohao Yeo and Kannan Ramchandran, “Remote Video File Synchronization For Heterogeneous Mobile Clients,” SPIE Optical Engineering and Applications, Aug, 2009. (invited paper)
[2]
Hao Zhang, Chuohao Yeo and Kannan Ramchandran, “Rate Efficient Remote Video File Synchronization,” IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP), April, 2009 (Best Student Paper Finalist).
[3]
Chuohao Yeo, Parvez Ahammad, Hao Zhang, and Kannan Ramchandran, “Rate-Constrained Distributed Distance Testing and Its Applications,” IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP), April, 2009. • Hao Zhang, Chuohao Yeo and Kannan Ramchandran, “VSYNC --- A Novel Video File Synchronization Protocol,” ACM Multimedia, Oct, 2008: 757-760 (Best Short Paper Award). [pdf] [slides]