Method and apparatus for correcting timing errors for a multi-picture display

摘要

A picture-in-a-picture television receiver displays a compound image which includes a compressed image derived from an auxiliary signal inset in a full-size image derived from a main signal. The auxiliary composite video signal is sampled (124,126) synchronous with a system clock signal that is burst locked to the main signal. The sampled data signal is separated (128) into luminance and color information component signals, which are subsampled (130) and stored in a field memory (136) synchronous with the system clock signal. The clock signal phase used for horizontal subsampling is determined at the start of each line to compensate for skew errors in the auxiliary signal. The luminance samples retrieved from the memory are applied to clock transfer circuitry (146) which resynchronizes the samples to a phase shifted version of the system clock signal to compensate for skew errors in the main signal. The phase shifted (142) clock signal is synchronized to the horizontal scanning signals used to display the compound image. The color information component signals (150) are not resynchronized to the phase shifted clock signal. The component signals of the compressed image are combined (154) to form a composite signal having color information that is synchronized to the main signal. The compressed signal is substituted (114) for a portion of the main signal to generate a signal representing the compound image.