Facsimile and static presentation processing – Static presentation processing – Attribute control
Patent
1989-04-14
1991-10-01
Groody, James J.
Facsimile and static presentation processing
Static presentation processing
Attribute control
358158, H04N 504
Patent
active
050538624
ABSTRACT:
A method and apparatus for synchronizing a received television signal to a subcarrier locked signal is provided. The apparatus includes a comparison block for determining whether the received television signal and subcarrier locked signal are related by a predetermined fixed frequency relationship and for providing indications of the same, and a signal generation block for dividing down the subcarrier locked signal according to the predetermined fixed frequency relationship so as to provide an output signal which is synchronized with the subcarrier locked signal, and at a frequency determined according to the fixed frequency relationship when the signals are related. The apparatus is particularly useful in PIP applications where the received television signal is a horizontal signal and the subcarrier locked signal is a four times multiple of the subcarrier frequency. The comparison block preferably includes a counter and a windowing circuit for determining whether edges of horizontal signal pulses are received within or outside a predetermined time window, and a decision circuit for determining whether the occurrences (counts) of in and out of window edges are indicative of related or unrelated signals. The entire apparatus preferably includes only flip-flops, simple logic gates such as AND, NAND, or OR gates, inverters, multiplexer switches, and resettable counters. The apparatus also preferably further includes a standard combination of flip-flops and a NAND gate for providing a synchronized horizontal reset output signal when the comparison block determines that the received horizontal clock and the subcarrier locked clock are not related.
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Greene David C.
Meyer Edwin R.
Phillips Larry G.
Goodman Edward W.
Groody James J.
Harvey David E.
North American Philips Corporation
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