A bias control device for a data slicer of an auxiliary video information decoder (BIAS CONTROL APPARATUS A DATA SLICER IN AN AUXILIARY VIDEO INFORMATION DECODER)

摘要

An auxiliary video information decoder for extracting an auxiliary video information signal from a video signal comprises a device for adjusting the slice level of the data slicer and the data slicer. The slice level is quickly adjusted until the reference component of the auxiliary video information signal is detected during the display period of the video signal in which the auxiliary video information is expected to occur. The coefficient is increased after the display period in which the reference component is detected and is decreased after the display period in which the reference component is not detected. The adjustment of the slice level is stopped while the coefficient is at least the predetermined number. The device quickly adjusts the slice level to account for a considerable amount of long term video signal amplitude changes (e.g., the next channel change) and maintains a constant slice level when transient changes in the amplitude of the video signal occur.