Patent ID: 7283157

Claim:
An automatic level control (ALC) method for use in a video signal processing system, the method comprising the steps of: determining the mean back porch level (N BP ) over a selected interval of the video signal; selecting a target back-porch level (L NOM ); determining a new fine offset control value O F [n], described by the relationship; O F [n] =(1−α)*[ N BP /G P −( N BP /G P −O F [n− 1])*( a/b+G F [n ])/( a/b+G F [n− 1])]+α*[ L NOM /G P −( N BP /G P −O F [n− 1])*( a/b+G F [n ])/( a/b+G F [n −1])], wherein; O F [n] is the new fine offset control value; O F [n−1] is the immediately preceding fine offset control value; α is a recursive filter coefficient; G F [n] is a fine gain control value; G F [n−1] is an immediately preceding fine gain control value; a is the y-intercept, and b is the slope of a linear fine gain control equation; L NOM is the target back porch level value referred to the signal output; N BP is the mean measured back porch level value; and G P is gain applied between a fine offset stage and the signal output.