Video telephone systems

Details Video telephone systems Video telephone systems

H - Electricity

04

N

H04N 7/26 (2006.01) H04N 7/045 (2006.01) H04N 7/12 (2006.01) H04N 7/36 (2006.01) H04N 7/52 (2006.01)

Patent

CA 2048623

-46- Abstract of the Disclosure Differential image data compression systems and techniques are disclosed for use in video telephone systems for full duplex, real time transmission of audio and video images over nominal 3 kHz residential telephone lines and other narrow bandwidth channels. Each video telephone device consists of a transmitting portion (12) and a receiving portion (38). In the transmitting section (12) a reduced grey-scale (luminance) image, preferably consisting of only black-and-white pixels, is compared in an image processing module (20) with a similarly reduced image derived from previous values to determine pixel positions that have changed. Information representative of the changes is then encoded and modulated and (time or frequency) multiplexed with the audio and/or chrominance signals for transmission. At the receiver (38), the incoming signal is demodulated and demultiplexed to separate the audio and video portions, the image portion is decoded and the luminance value is updated by an image updating unit (50). Adaptive resolution, pixel averaging and interpolation techniques are also disclosed for picture enhancement.

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