Virtually all teleconferencing systems incorporating video use compres
sion algorithms to reduce the video data rate to manageable proportion
s. For a given bit rate, higher compression brings higher quality, alt
hough there can also be disadvantages, such as increased delay. Confer
encing implies interconnectability, so the development of appropriate
standards has played a vital part in enabling the videoconferencing ma
rket in particular to become established. This paper describes the mai
n techniques used in video compression and how these have been embodie
d in successive generations of standards appropriate to various applic
ation areas. Other non-standardised techniques, and forthcoming standa
rds are also discussed.