In a teleconferencing system, a video encoder at the transmit end of the system includes a frame memory for storing video samples of a frame of a motion-picture signal and reading video samples at frame intervals. For still-picture transmission, an encoder circuit translates video samples read out of...http://www.google.ca/patents/US4924311?utm_source=gb-gplus-sharePatent US4924311 - Dual-mode teleconferencing system
