He joined the faculty of the University of Washington in 1996. Before that, he was the Director of Video Signal Processing at Bellcore. He has been a chaired professor and visiting professor at many universities.

Sun’s research interests include video processing, computer vision and machine learning. He has been awarded 13 patents and has published more than 200 technical publications, including 18 book chapters. He has guest-edited 12 special issues for various journals. He was actively involved in the development of video coding standards, and has co-edited a book entitled Compressed Video over Networks.