Patent Document ID: 4589013
Application ID: 06520067
Patent Status: 1

Claim One:
1. A method of automatically controlling the compositing of encoded color image background scene and foreground scene video signals involving a background scene and a foreground scene having a foreground subject placed before a colored backing, which comprises the steps of; (a) forming a first control signal E.sub.b as a function of the brightness and visibility of the colored backing and also as a function of a secondary illumination on the foreground subject received from the colored backing, said first control signal E.sub.b being input to a foreground video subtraction circuit; (b) forming a second control signal E.sub.c as a function of the brightness and visibility of the colored backing, but not as a function of the secondary illumination being reflected from the foreground subject, said second control signal E.sub.c being input to a background video level control circuit; (c) forming a gating pulse identifying that portion of the foreground scene representing the colored backing; (d) comparing and automatically controlling the phase-angle of a generated subcarrier signal to match the phase-angle of a foreground video subcarrier signal during said gating pulse; (e) comparing and automatically controlling the level of the generated subcarrier signal to match the level of the foreground video subcarrier signal during said gating pulse; (f) removing the chroma of the colored backing, and discoloration chroma from the foreground subject resulting from the secondary illumination by subtracting the phase and level matched generated subcarrier under control of the first control signal E.sub.b from the foreground scene video signal; (g) automatically comparing and adjusting the level of the second control signal E.sub.c to match the level of the foreground scene video signal during the gating pulse; (h) removing the luminance of the colored backing from the foreground scene video signal by subtracting the adjusted level of the second control signal E.sub.c from the foreground scene video signal; (i) comparing the second control signal E.sub.c during the gating pulse, with a predetermined constant and automatically adjusting the level of said second control signal E.sub.c to match the level of the constant; and (j) combining the foreground scene video signal, the colored backing chroma and luminance thereof having been removed, with the background scene video signal, the level of which has been controlled by the second control signal, to form a composite video image.