APPENDIX B: ITU Video Standards

The standards are grouped alphabetically and can be found at http://www.itu.int/rec/recommendation.asp?type=series&lang=e&parent=T-REC or at http://www.ituaj.or.jp/book/itut-rec.html

H.320 – ISDN - Narrow-band visual telephone systems and terminal equipment.

H.321 – ATM - Adaptation of H.320 visual telephone terminals to B-ISDN environments.

H.323 – IP - Framework and wire-protocol for multiplexed call signaling transport.

Underneath these three variations of video are several other protocols that make video conferencing as rich and full-featured as we know it today. The earliest video protocols were designed for ISDN and adapted for ATM and IP as the other protocols were developed.

H.221 - Frame structure for a 64 to 1920 kbps channel in audiovisual teleservices.

H.224 - Real time control protocol for simplex application using the H.332 LSD/HSD/MLP channels. This helps in sending real time information over Low Speed Data, High Speed Data, or MLP, which is T.120.

H.281 - A far end camera control protocol for videoconferences using H.224. This allows the caller to manipulate the callee’s camera.

H.243 - Procedures for establishing communication between three or more audiovisual terminals using digital channels up to 1920 kbps. Also known as Chair Control. This allows one person in a multipoint conference to control who is being shown to the rest of the participants. The person with chair control can also grant or deny permission to a participant who wants to speak.

H.261 - Video codec for audiovisual services at p x 64 kpbs. This is the actual video protocol for low speed video transmission such as ATM and ISDN.

H.263 - Video coding for low bit rate communication. This protocol uses compression to send video that produces a better quality picture. However, sender and receiver must have this protocol selected in order to decode it.

H.263+ and H.263++ are further refinements to the H.263 protocol to further enhance the video over IP.

H.231 - Multipoint control units for audiovisual systems using digital channels up to 1920 kbps. This allows codecs to act as a four port MCU.

H.331 - Broadcasting type audiovisual multipoint systems and terminal equipment. This protocol provides for the one way broadcasting of video.