Gary Joseph Sullivan (born 1960) is an American electrical engineer who led the development of the H.264/MPEG-4 AVC and HEVC video coding standards and created the DirectX Video Acceleration (DXVA) API/DDI video decoding feature of the Microsoft Windows operating system.
He was the chairman of the Joint Video Team (JVT) standardization committee that developed the H.264/AVC standard, and he personally edited large portions of it. Since January 2010, he has been a co-chairman of the Joint Collaborative Team on Video Coding (JCT-VC) and an editor for developing the High-Efficiency Video Coding (HEVC) standard. He has also led and contributed to a number of other video and image related standardization projects such as extensions of ITU-T H.263 video coding, multiview, and 3D video coding for AVC and HEVC, and JPEG XR image coding. Since October 2015, he has been a co-chairman of the Joint Video Exploration Team (JVET) for the exploration of video coding beyond the capability of HEVC. He has also published research work on various topics relating to video and image compression.