Consolidated Video Systems, Inc.

Allan L Swain

Michael W Tallent

Ronnie M Harrison

William B Hendershot, Iii

Lee E Scaggs

Thomas C Lyon

Ronald D Long

An input voltage controlled oscillator circuit for a digital video time base corrector used to process television signals to remove time base errors introduced during signal recording, reproducing, or transmission. In the time base corrector, incoming video signals are converted from analog-to-digital form, temporarily stored in a memory unit at a clocking rate which varies in a manner generally proportional to the time base errors, and the stored signals are fetched at a standard clocking rate. The input voltage controlled oscillator circuit generates the clock signals for performing the analog-to-digital conversion and for storing the digital signals in the memory unit. The frequency of the clock signals varies in accordance with the time base errors in the composite sync and burst portions of the incoming video signals. The VCO circuit includes an oscillator for generating an integral multiple of the clock signal train, a first phase lock loop controlled by the frequency of successive composite sync pulses in the incoming video signal, a second phase lock loop controlled by the colorburst portion of successive lines of video information, a gated integrator coupled to the second phase lock loop for integrating successive ones of the VCO control signals generated by the second phase lock loop over a plurality of successive lines of video, and means for enabling the gated integrator during the colorburst portion of successive lines of video. The VCO circuit further includes means for disabling the gating means and the gated integrator when one of the colorburst portions of the video signals lies below a predetermined threshold.

Input voltage controlled oscillator circuit for a television signal time

A method and apparatus for synchronizing unrelated video type signals from two different sources without employing feedback loops between the two sources. Incoming video signals are converted from analog to digital form and are clocked into a shift register unit by input clock signals phase and frequency locked to the instantaneous horizontal frequency and the color burst frequency portions of the incoming signal. The digitized video signals progressing along the shift register are stored at the input clock signal rate in a random access (RAM) having a sufficient capacity to provide continuous output video signals during each field. The signals are clocked out from the RAM by output clock signals derived from the sync and color burst portions of a local signal comprising either composite video or composite color burst, which are synchronized with the local sync generator. The video signals fetched from the RAM are converted from digital to analog form by the output clock signals, are processed to include standard sync, blanking and color burst signals, and are coupled to follow-on equipment. The sync burst portions of the incoming non-synchronized video signals are deleted during storage in the shift register so that a smaller shift register can store an entire video field. The shift register has a plurality of output taps providing different coarse delay periods only one of which is enabled by a vertical sync pulse in the output clock train prior to transfer of a given field into the RAM.

Digital video synchronizer

A sequence control unit for a digital video time base corrector used to process television signals to remove time base errors introduced during signal recording, reproducing, or transmission. In the time base corrector, incoming video signals are converted from analog to digital form, temporarily stored in a memory unit at a clocking rate which varies in a manner generally proportional to the time base errors, and the stored signals are fetched at a standard clocking rate. The sequence control unit controls contemporaneous storing and fetching from different portions of the memory unit and includes circuitry for preventing application of both store and fetch signals to the same memory unit portion when the accumulated time base error would cause such an overlap condition.

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Palo Alto, CA, United States of America

Allan L Swain