The Video Coding Experts Group or Visual Coding Experts Group (VCEG, also known as Question 6) is a working group of the ITU Telecommunication Standardization Sector (ITU-T) concerned with video coding standards. It is responsible for standardization of the "H.26x" line of video coding standards, the "T.8xx" line of image coding standards, and related technologies.
Administratively, VCEG is the informal name of Question 6 (Visual coding) of Working Party 3 (Media coding) of Study Group 16 (Multimedia coding, systems and applications) of the ITU-T. Its abbreviated title is ITU-T Q.6/SG 16.
The goal of VCEG is to produce recommendations (international standards) for video coding and image coding methods appropriate for conversational (e.g. videoconferencing and video telephony) and non-conversational (e.g., streaming, broadcast, file download, media storage/playback, or digital cinema) audio/visual services. This mandate concerns the maintenance and extension of existing video coding recommendations, and laying the ground for new recommendations using advanced techniques to significantly improve the trade-offs between bit rate, quality, delay, and algorithm complexity. Video coding standards are desired with sufficient flexibility to accommodate a diverse number of transport types (Internet, LAN, Mobile, ISDN, GSTN, H.222.0, NGN, etc.).
Question 6 is part of Study Group 16, which is responsible for studies relating to multimedia service capabilities, and application capabilities (including those supported for NGN). This encompasses multimedia terminals, systems (e.g., network signal processing equipment, multipoint conference units, gateways, gatekeepers, modems, and facsimile), protocols and signal processing (media coding).
VCEG was preceded in the ITU-T (which was called the CCITT at the time) by the "Specialists Group on Coding for Visual Telephony" chaired by Sakae Okubo (NTT) which developed H.261. The first meeting of this group was held Dec. 11–14, 1984 in Tokyo, Japan. Okubo was also the ITU-T coordinator for developing the H.262/MPEG-2 Part 2 video coding standard and the requirements chairman in MPEG for the MPEG-2 set of standards.
The first digital video coding standard was H.120, created by the CCITT (now ITU-T) in 1984. H.120 was not usable in practice, as its performance was too poor. H.120 was based on differential pulse-code modulation (DPCM), which had inefficient compression. During the late 1980s, a number of companies began experimenting with the much more efficient discrete cosine transform (DCT) compression for video coding, with the CCITT receiving 14 proposals for DCT-based video compression formats, in contrast to a single proposal based on vector quantization (VQ) compression. The H.261 standard was subsequently developed based on DCT compression.
In 1994, Richard Shaphorst (Delta Information Systems) took over new video coding development in ITU-T with the launch of the project for developing H.324. Schaphorst appointed Karel Rijkse (KPN Research) to chair the development of the H.263 video coding standard as part of that project. In 1996, Schaphorst then appointed Gary Sullivan (PictureTel, since 1999 Microsoft) to launch the subsequent "H.263+" enhancement project, which was completed in 1998. In 1998, Sullivan was made rapporteur (chairman) of the question (group) for video coding in the ITU-T that is now called VCEG. After the H.263+ project, the group then completed an "H.263++" effort, produced H.263 Appendix III and H.263 Annex X, and launched the "H.26L" project with a call for proposals issued in January 1998 and a first draft design adopted in August 1999. In 2000, Thomas Wiegand (Fraunhofer HHI) was appointed as an associated rapporteur (vice-chairman) of VCEG. Sullivan and Wiegand led the H.26L project as it progressed to eventually become the H.264 standard after formation of a Joint Video Team (JVT) with MPEG for the completion of the work in 2003. (In MPEG, the H.264 standard is known as MPEG-4 part 10.) Since 2003, VCEG and the JVT have developed several substantial extensions of H.264, produced H.271, and conducted exploration work toward the potential creation of a future new "HEVC". In January 2010, the Joint Collaborative Team on Video Coding (JCT-VC) was created as a group of video coding experts from ITU-T Study Group 16 (VCEG) and ISO/IEC JTC 1/SC 29/WG 11 (MPEG) to develop a new generation video coding standard.
In July 2006, the video coding work of the ITU-T led by VCEG was voted as the most influential area of the standardization work of the CCITT and ITU-T in their 50-year history. The image coding work that is now in the domain of VCEG was also highly ranked in the voting, placing third overall.
In July 2014, Jill Boyce (then of Vidyo, later Intel) was appointed as an additional associated rapporteur for VCEG.
In May 2015 the ITU celebrated its 150-year anniversary, and the work of VCEG was one of the five areas of standardization to be recognized by an "ITU 150 Award" as one of the most influential topics of ITU work.