Abstract
The impact of various signals on the vertical blanking interval (VBI) lines before and after the line containing a Ghost Cancellatip Reference (GCR) s$nal has been of great interest to broadcasters, standards setting bodies, and manufacturers. This paper will discuss some properties of the US standard GCR, various types of signals that can be on VBI lines, effects of these on ghost cancellation, and algorithms. OCR Properties The US standard GCR[l] can be described as a signal with a group delay linearly related to frequency. This signal is transmitted in an eight field sequence of changing polarity (+,-,+,-,-,+,-,+). The GCR starts 12 psec after the leading edge of the horizontal sync and ends 36 pec later. It is specified to cancel ghosts from -3 psec to +45 pec relative to the main signal. The above will serve as the basis for analysis of the VBI issue.
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