Verfahren zum Empfangen von Teletextdaten

摘要

When teletext data are received, usually n faulty transmitted information units are corrected on the basis of error control/information (FEC) transmitted with the teletext data, according to their correctability. In addition, the correctness of the wanted information contained in each selected and possibly corrected information block is determined on the basis of checking information (CRC) transmitted together with the teletext data. The error check for the tested information block is prematurely interrupted when the wanted information contained in an information block is recognized as faultless, on the basis of the checking information transmitted with the teletext data. In order to vary and possibly to increase the error correction capacity at the decoder side thanks to the correction capacity of the error control code predetermined at the coder side, the following steps are applied: among the information units of the concerned information block, one or several information units are gradually inverted; after each inversion step a correction attempt is made with n information units on the basis of the error control information (FEC); after each correction attempt the checking information is used to ascertain whether the correction was successful; when the correction was successful, error checking is interrupted; when a correction attempt was unsuccessful, the inverted and tentatively corrected information units are restored to their initial state.