Vidicraft, Inc.

Tektronix, Inc.

Xantech Corporation

Roger A Marin

James A Karlock

David J Jurgensen

A vertical blanking interval standardizer circuit detects the vertical synchronization interval of a video signal and generates a vertical block sync pulse which replaces a serrated vertical sync signal in which the pulse spacing has been modified in a non-standard manner. An early control pulse existing from the beginning of the vertical blanking interval until the trailing edge of the vertical block sync pulse and a late control pulse existing from the trailing edge of the vertical block sync pulse until the end of the vertical blanking interval are generated. The early and late control pulses pre-bias an amplitude limiter transistor such that the transistor is reverse biased by signal components during the vertical blanking interval which exceed a selected blanking level. In this manner, pulses occurring during the vertical blanking interval which have a gray or a white level are blocked and replaced by the selected blanking level.

Vertical blanking interval standardizer circuit

A video processing circuit separates chrominance and luminance signals and processes the same separately from synchronizing information whereby the video signal may be reformed with a selected video level, selected color saturation, and selected chroma hue. The synchronizing information is not reprocessed, but is coupled through the circuit and the other video signal portions are adjusted relative thereto. An output circuit provides a stable output with very low distortion by including a negative feedback circuit having appreciable loop gain. A sync separator circuit also includes a feedback circuit for consistently detecting horizontal sync pulses approximately midrange.

Video circuitry

A video processing circuit separates chrominance and luminance signals and processes the same separately from synchronizing information whereby the video signal may be reformed with a selected video level, selected color saturation, and selected chroma hue. The synchronizing information is not reprocessed, but is coupled through the circuit and the other video signal portions are adjusted relative thereto.

Video circuit

An apparatus for matching the blanking levels of two television video signals is disclosed. When the vertical interval reference signal or any other signal (e.g., sync) is inserted on a program video signal their blanking levels should be matched. The apparatus described accomplishes this by matching the blanking level of the signal being inserted to that of the program video. The match is produced by sampling the residual clamping error of a slow clamp on the program channel and adding it to the signal being inserted. Therefore, the noise which would have been added to the program video is added to the inserted signal instead and therefore will not be visible in the television picture.

Growing community of inventors

Portland, OR, United States of America

Roger A Marin