Abstract: Apparatus for digitally processing a composite video signal recorded in PAL format for producing a continuous waveform at a four-line rate indicates at any four-frame reference time if the polarity of the subcarrier is in phase with a reference or inverted for matching the subcarrier phase of two PAL signals as required in electronic splicing of video tape recordings, in special effects switching, or mixing of PAL video signals.

Abstract: The line-by-line R-Y component phase is detected by digital means directly from the composite video source, for example, the recorded composite video signal reproduced from a video tape recorder, and a continuous signal waveform at a two-line period is produced which indicates the instantaneous polarity of the R-Y component of each line of a PAL format video signal. The invention further provides for a positive elimination of the effect of spurious signals, such as dropouts, as well as compensating for the frame rate offset of the subcarrier employed in certain signal formats, such as PAL-B.

Abstract: A single pre-vertical sync pulse that repeats once each field and the line-by-line chroma phase information which exists in the form of the PAL square wave at one-half of the horizontal line frequency are combined in a novel circuit comprising a pair of J-K flip-flops to directly produce the complete Bruch blanking function in digital form for each field on an independent field-by-field basis.