VIDEO TRAVELING MATTE SYSTEM

摘要

VIDEO TRAVELING MATTE SYSTEM A video traveling matte system is disclosed in which the video signal from a foreground televion camera is examined for the presence of a particular color by an arrangement employing multipliers to multiply the differences between the red and blue components of the video signal and a luminance signal derived from the video signal by the signals from a sine/cosine potentiometer. The combined signal from the outputs of the multipliers is fed to a first comparator for comparison with a reference value and the resulting pulses are filtered by a 4-pole active Bessel filter and compared with a reference value in a second comparator to increase the width of the pulses by a selected amount. The pulses of increased width prevent the formation of a matte outline between foreground and background images as the true and complementary values thereof are applied to alternately gate the video signals from the foreground television camera and a background television camera to a common output. The effects of shadows in the foreground image are maintained despite substitution of the background image by utilizing the combined signal from the multipliers to modulate pulses from the second comparator prior to use of such pulses to gate the video signal from the background television camera to the common output. The effects of shadows are further enhanced by a logarithmic amplifier which introduces a predetermined logarithmic transfer characteristic into the modulation signal to compensate for the black stretch circuits used in most television cameras.