Bias control apparatus for a data slicer in an auxiliary video information decoder

Apparatus for processing a video signal having a reference signal component occurring during a reference signal interval included in each of a plurality of horizontal display intervals of said video system, said apparatus comprising:

• means for determining during each of said reference signal intervals whether said reference signal component exhibits a predetermined relationship to a reference level;
• and
• means for modifying said reference level after a delay including said plurality of horizontal display intervals;
• said delay beginning in response to said reference signal component and said reference level exhibiting a relationship other than said predetermined relationship;
• said reference signal component and said reference level exhibiting said relationship other than said predetermined relationship during more than one of said reference signal intervals included in said delay.

Apparatus for decoding auxiliary information included in a video signal comprising:

• means for producing a first count representative of a number of signal transitions of said video signal that cross a reference level during each interval included in a plurality of intervals;
• means responsive to a binary value for providing said reference level;
• and
• control means responsive to said first count for modifying said binary value in only one direction for changing said reference level such that said first count tends to become a predetermined count;
• said reference level being increased and decreased in response to said binary value being modified in only said one direction.