Television – Synchronization – Sync separation
Patent
1997-12-29
2000-12-12
Hsia, Sherrie
Television
Synchronization
Sync separation
348558, H04N 508, H04N 546
Patent
active
061605891
ABSTRACT:
A video frame detector circuit used in synchronizing one video signal with another video signal. The video frame detector of the present invention is able to automatically detect a start of frame portion of any video composite synchronization signal connected to it without requiring programming. The start of frame commences with the least frequent vertical field, or if all fields are equally frequent, a deterministic process is used to promote one of the fields to be the start of the frame. Since the video frame detector circuit of the present invention does not require programming to recognize various video signal formats, it readily adapts to different video signal conditions with little or no manual intervention. The video frame detector contains a number of memory stores for storing previously detected video patterns obtained from a composite synchronization signal. Once a current pattern is ascertained from the composite synchronization signal, it is compared against the stored patterns. Information regarding recognized patterns is stored in a history FIFO. New patterns are stored in vacant memories replacing those stored patterns that are most frequently seen. Frequency counters maintain information as to the frequency of each stored pattern. A state machine assumes that the least frequently ascertained patterns are the start of frame portion and generates a start of frame pulse accordingly. The start of frame pulse can be delayed to properly align with the video signal.
REFERENCES:
patent: 5012339 (1991-04-01), Kurata et al.
patent: 5608461 (1997-03-01), Sadowski et al.
Hsia Sherrie
Silicon Graphics Inc.
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