Video Overlay Synchronizer/Sync Generator
Original Publication Date: 1986-Jun-01
Included in the Prior Art Database: 2005-Mar-09
This article describes a circuit arrangement that generates the proper horizontal and vertical sync signals for video controllers that can both overlay text on an external video signal and generate video output when no external video source is available. In designing video circuits that can both overlay text on an external video input and also generate video output when no external video source is available, the following two cases must be supported: 1. Video Source Synchronization - In this case the sync signals used to generate the overlay video must be synchronous with the sync signals of the external source. 2. Sync Generation - Sync signals for generating the video must be created even when there are no external sync signals available.