| 摘要 |
<p>From a television signal data such as teletext or closed caption data is extracted by slicing. A binary data signal is formed dependent on whether the television signal level is above or below a slicing level (S). The slicing level (S) is selected by defining a reconstructed data signal (D) with signal values equal to plus and minus an amplitude value relative to a middle level and transitions between these signal values at time points where the television signal crosses the slicing level. An auxiliary signal (R) is formed that contains the television signal (Vi) from which the reconstructed data signal (D) has been subtracted. A feedback loop (34, 36, 37, 38, 32) is provided that adapts the amplitude value (A) to regulate a residual data signal amplitude in the auxiliary signal (R) to zero. The slicing level (S) is determined from a difference between television signal (Vi) and from a television signal data such as teletext or closed caption data is extracted by slicing. A binary data signal is formed dependent on whether level (S is selected by defining a reconstructed data signal (D) with signal values equal to plus and minus an amplitude value relative to a middle level and transitions between these signal values at time points where the television signal crosses the slicing level. An auxiliary signal (R) is formed that contains the television signal (Vi) from which the reconstructed data signal (D) has been substracted. A feedback loop (34, 36, 37, 38, 32) is provided that adapts the amplitude value (A) to regulate a residual data signal amplitude in the auxiliary signal (R) to zero. The slicing level (S) is determined from a difference between television signal (Vi) and the reconstructed data signal (D).</p> |
