Closed captioning processing architecture for providing text data during

Abstract

A graphics display system processes a video signal that includes closed caption text. A digitizer and decoder circuit retrieves the closed caption data and formats the data to avoid loss by decimation, to be scalable, and to include an indicator of capture or display. The digitizer and decoder circuit includes ping pong buffers for storing the data. During a first odd field, the closed caption data is stored in the ping buffer and the closed caption data from a previous field is read from the pong buffer. During the even field, the closed caption data is again read from the pong buffer. During the next odd field, the operation is repeated with the functions of the ping and pong buffers reversed. Alternatively the even field may contain the closed caption data. The digitizer and decoder circuit includes a capture or display valid bit in the closed caption data to indicate that the caption data is from the current field. The formatted data and a vertical synchronization signal are provided to a graphics user interface (GUI) accelerator which stores the data in a frame buffer or on disk. Response to the vertical synchronization signal, the GUI accelerator generates an interrupt that is serviced by the host processor which controls the reading and display of the caption data.