The Free On-line Dictionary of Computing (30 December 2018):

H.261

    A video compression standard
   developed by ITU-T before 1992 to work with integrated
   service digital network.  Data is compressed at the rate of
   64P kilobits per second, where P can range from 1 to 30
   depending on the number of ISDN channels used.  This standard
   was developed primarily to support video phones and video
   conferencing.

   See also ivs.

   (http://crs4.it/~luigi/MPEG/mpeggloss-h.html#H.261).

   [Date?  Details?]

   (1994-11-03)