Abstract: A scan converter processes an input video signal having a fixed number of an lines per frame, a horizontal synchronization rate and a vertical synchronization rate on an input video line to produce an output video signal having a predetermined number of scan lines per frame and a selected number of pixels per line on a video output line. The scan converter locks to the vertical synchronization rate of the input video signal to make the output video signal have a vertical synchronization rate equal to the vertical synchronization rate of the input video signal. The output horizontal rate is determined by multiplying the vertical synchronization rate by the predetermined number of scan lines per frame in the output video signal. The input horizontal synchronization rate is multiplied by the selected number of pixels per line to produce a WRITE pointer signal for writing input picture lines into a memory.

Abstract: A teleconferencing system includes desktop computers, external cameras and eripheral apparatus to allow interconnection of two or more terminals to engage in teleconferencing via digital data networks. A frame grabber interfaces each camera with its computer. Signals output from the computer are encoded and compressed before being input to a telephone line via a modulator/demodulator. A decoder is connected between the modulator/demodulator and the computer for decoding compressed video signals received by the modulator/demodulator means from the telephone line so that the signals may be displayed on a video display connected to the computer.