| 摘要 |
<p>A decoding system (Fig. 4, 106) for extracting digital teletext and closed caption data from a video signal comprises a software implementation executed on a processor (Fig. 4, 408) which includes both a closed caption module (Fig. 5) and a teletext module (Fig. 8). The decoder system calls the closed caption module to detect a clock synchronization signal (Fig. 5, 502). Upon finding such signal, the closed caption module synchronizes to the signal (Fig. 5, 506), identifies a framing code (Fig. 5, 504), and extracts the closed caption data (Fig. 5, 506). Similarly, the decoder system may call the teletext module for the teletext lines, which also synchronizes using a teletext clock synchronization signal. When the clock synchronization signal is detected (Fig. 8, 802), the teletext module interpolates the incoming data to reconstruct the data signal (Fig. 8, 804). The data signal is then processed to normalize the amplitude (Fig. 8, 806) and reduce the 'ghost' effects of signal echoes (Fig. 8, 808) prior to the slicing of the data signal (Fig. 8, 812). Hamming code error detection may be used to ensure the accuracy of the data (Fig. 8, 814).</p> |
