| 摘要 |
A decoding system comprises a software-oriented implementation of the decoding process for extracting binary teletext and closed caption data from a signal. The decoder system according to one embodiment includes a processing unit which implements both a closed caption module and a teletext module. The decoder system calls the closed caption module to detect a clock synchronization signal associated with closed caption data. Upon finding the clock synchronization signal, the closed caption module synchronizes to the signal, identifies a framing code, and extracts the closed caption data. 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, the teletext module interpolates the incoming data to reconstruct the data signal. The data signal is then processed to normalize the amplitude and reduce the "ghost" effects of signal echoes prior to the slicing of the data signal. The data is also suitably subjected to Hamming code error detection to ensure the accuracy of the data. |
