| 摘要 |
<p>An auxiliary video information decoder, for decoding auxiliary video information signals such as closed caption data, includes a data slicer (210) having a variable slicing level. The slicing level is adjusted in response to the amplitude of a run-in-clock (RIC) signal that is included in the auxiliary video information portion of the video signal. Slicing level adjustment involves averaging the RIC signal amplitude during a substantially integral number of cycles of the RIC signal that occur during a control interval (RICWND). The timing of the RIC signal waveform with respect to the control interval is evaluated to verify that the desired number of cycles of the RIC signal occur during a control interval. The timing evaluation operation involves counting (250) cycles of the RIC signal during a control interval. If the desired number of cycles do not occur, the timing of the control interval is modified (200, 220, 230) with respect to the RIC signal and the timing is reevaluated during a subsequent control interval. The evaluation and timing-modification operations may be repeated until the desired number of cycles of the RIC signal are detected. If repeated operation does not provide the desired result, a control signal may be generated indicating that the video signal may not include auxiliary video information.</p> |
