John A Sparks

US Patent:

39506070, Apr 13, 1976

Filed:

Apr 30, 1973

Appl. No.:

5/355802

Inventors:

Glen R. Southworth - Boulder CO
Roy W. Lewallen - Denver CO
John E. Sparks - Boulder CO

Assignee:

Colorado Video, Inc. - Boulder CO

International Classification:

H04N 712

US Classification:

178 6

Abstract:

A method and apparatus is disclosed for converting a wide-bandwidth signal to a narrow-bandwidth signal, the disclosed method and apparatus being particularly well suited for converting a wide-bandwidth real-time television signal to a narrow-bandwidth signal. A sampled video signal is coupled to an analog-to-digital converter which converts the amplitude of each sampled element to a binary code word having a predetermined number of bits. The binary code words are then written into a buffer storage element controlled by a clock switching device and later clocked out of the buffer storage device at a clock rate less than the input rate with the output from the buffer storage device being coupled to a digital-to-analog converter whose output is an analog signal with the same amplitude variations as the sampled video signal but with a time base stretched out by a predetermined factor. The field, either odd or even interlace, from which the sampled video signal was taken is identified by ascertaining the location of the horizontal signal pulses relative to the vertical signal pulse, and this field index may then be used to code the output narrow-bandwidth video signal. Another embodiment is disclosed which utilizes an analog shift register as the buffer storage device in place of the digital buffer storage with its attached analog-to-digital and digital-to-analog converter.