Hue control without chrominance demodulation for PAL

摘要

A hue control circuit for adjusting the color phase of a composite PAL television signal without demodulating the chrominance component of the composite PAL television signal uses a polyphase interpolator to change the phase of the modulated chrominance component. A set of coefficients corresponding to a desired hue adjustment is applied to the polyphase interpolator. A hue coefficient address circuit addresses a coefficient memory containing a plurality of sets of coefficients, the sets being in complementary pairs. During each horizontal blanking line interval for a given desired hue adjustment the hue coefficient address circuit swaps the sets of coefficients between the complementary pair defining the desired hue adjustment in synchronization with the alternating sign of one of the color difference components of the modulated chrominance component on a line by line basis. The adjusted modulated chrominance component is combined with the luminarice component, suitably delayed, to produce an output composite PAL television signal with the desired hue adjustment.