Gary J. Sullivan has been a chairman and co-chairman of various video and image coding standardization activities in ITU-T VCEG, ISO/IEC MPEG, ISO/IEC JPEG, and in their joint collaborative teams since 1996 and in 2021 he became the chair of ISO/IEC JTC 1 Subcommittee 29, the organization that oversees JPEG and MPEG. He has led the development of the Advanced Video Coding (AVC) standard (ITU-T H.264 | ISO/IEC 14496-10), the High Efficiency Video Coding (HEVC) standard (ITU-T H.265 | ISO/IEC 23008-2), the Versatile Video Coding (VVC) standard (ITU-T H.266 | ISO/IEC 29090-3), the various extensions of those standards, and several other standardization projects. He is a Video and Image Technology Architect at Microsoft Research in Redmond, Washington. At Microsoft, he has also been the originator and lead designer of the DirectX Video Acceleration (DXVA) video decoding feature of the Microsoft Windows operating system.

The team efforts that Sullivan has led have been recognized by three Emmy Awards. He has received the SMPTE Digital Processing Medal, the IEEE Masaru Ibuka Consumer Electronics Award, the IEEE Consumer Electronics Engineering Excellence Award, two IEEE Trans. CSVT Best Paper awards, the INCITS Technical Excellence Award, the IMTC Leadership Award, and the University of Louisville J. B. Speed Professional Award in Engineering. He is also Fellow of IEEE and SPIE.