Television – Synchronization – Sync generation
Patent
1996-12-26
1999-05-04
Peng, John K.
Television
Synchronization
Sync generation
348521, 348524, 348531, 348540, 358148, 358153, 358158, H04N 500, H04N 506, H04N 508, H04N 510
Patent
active
059009144
ABSTRACT:
A horizontal synchronization signal generating circuit self-generates a horizontal synchronization signal if an actual horizontal synchronization signal fails to be detected in a composite video signal. Each time an edge-detection circuit detects an actual horizontal synchronization pulse, a counter and decoder are reset. An actual horizontal synchronization signal has a period of 63.5 .mu.s. If the edge detection circuit fails to detect the actual horizontal synchronization signal, then the decoder outputs a self-generated horizontal synchronization signal at 64 .mu.s and a selector circuit disables the edge detection circuit for approximately 35 .mu.s. In contrast, if the edge-detection circuit detects an actual horizontal synchronization signal, the decoder is reset before it can output the self-generated signal and the selector disables the edge detection circuit for approximately 60 .mu.s. Accordingly, a period of 35 .mu.s exists during which an edge-detecting signal is disabled after a horizontal synchronizing output produced by self-generation has been outputted. The disabling period allows detection of horizontal synchronizing inputs when narrow pulse signals are lost during vertical synchronous periods, and allows immediate extraction of the horizontal synchronizing inputs regardless of the difference of the odd/even fields and allows outputting of the corresponding horizontal synchronizing output.
REFERENCES:
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patent: 5208672 (1993-05-01), Konishi et al.
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Natnael Paulos M.
Peng John K.
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