Patent Number: 6,169,533

Title: High speed analog color key detection technique and system

Abstract: A high speed analog color key detection system is disclosed for video/graphics mixing that employs a high speed analog strobe comparator to compare the analog version of a pre-defined color key value to the stream of pixel values in an incoming analog graphics signal. When the comparator indicates a match, the display signal is switched from the analog graphics signal to an incoming analog video signal, enabling the analog video signal to be displayed within a graphics window. Comparisons are triggered by active transitions of a strobe signal with a frequency that is an integer k multiple of the frequency at which the pixel values are generated by a graphics card. Oversampling strobe signals (where the integer k is greater than one) enable comparisons to be performed on small segments of fat pixel values. The strobe signal is generated using a phase locked loop that is synchronized with a horizontal synchronization signal provided by the graphics card. The PLL also regenerates the pixel clock using the horizontal synchronization signal.

Inventors: Tse; Lawrence Tze-Leung (Fremont, CA)

Assignee: Chrontel, Inc.

International Classification: G09G 5/02 (20060101); G09G 5/36 (20060101); H04N 9/75 (20060101); H04N 9/64 (20060101); G09G 5/18 (20060101); G09G 005/00 ()

Expiration Date: 01/02/2018