Synchronization system for overlay of an internal video signal upon an external video signal
First Claim
1. A video signal mixing system comprising:
- an input means for receiving an external composite video signal;
a horizontal synchronization pulse detecting means connected to said input means for detecting the horizontal synchronization pulses of said first composite video signal;
an external signal loss detector connected to said input means for detecting and indicting the loss for longer than a first predetermined period of time greater than the period of said horizontal synchronization pulses the loss of said external composite video signal;
a video clock frequency standard for determining a frequency;
a video clock signal generating means connected to said horizontal synchronization pulse detecting means and said external signal loss detector for generating a video clock signal, said video clock signal generating means havinga horizontal phase lock loop means connected to said horizontal synchronization pulse detecting means including a horizontal controlled oscillator for generating internal horizontal synchronization pulses in phase synchronization with said detected horizontal synchronization pulses, anda video clock phase lock loop means connected to said horizontal phase lock loop means and said video clock frequency standard including a video clock controlled oscillator for generating said video clock signal having a frequency corresponding to and corrected by the frequency of said internal horizontal synchronization pulses when said external signal loss detector does not indicate the loss of said external composite video signal and having a frequency corresponding to said frequency determined by said video frequency standard when said external signal loss detector indicates loss of said external composite video signal, whereby momentary loss of said external composite video signal for a time less than said predetermined period of time causes said frequency of said video clock signal to be controlled by said horizontal controlled oscillator;
a video signal generating means connected to said video clock signal generating means for generating an internal composite video signal in synchronization with said video clock signal thereby generating said internal composite video signal having horizontal lines in synchronism with said detected horizontal synchronization pulses; and
a video switching means connected to said input means, said external signal loss detector and said video signal generating means having an output means for selectively connecting either said external composite video signal or said internal composite video signal to said output means, said video switching means selecting said internal composite video signal when said external signal loss detector indicates loss of said external composite video signal, whereby said output means receives a combined video signal having synchronized horizontal lines.
1 Assignment
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Accused Products
Abstract
The present invention is manner of synchronization in a video overlay system for overlay of an internal video signal upon an external video signal. In the video overlay system of the present invention the horizontal synchronization pulses of the external video signal are detected to enable generation of the internal video signal having synchronized horizontal lines. This is achieved by generating a video clock signal for control of video signal generation at a frequency that is a multiple of the frequency of the horizontal lines of the external video signal. The vertical synchronization signal of the external video signal is detected in the preferred embodiment to enable generation of the internal video signal having video frames in synchronism with those of the external video signal. In order to insure further stability in the combined video signal, the color burst signal of the external video signal is detected for control of the frequency, phase and amplitude of the color modulation of the internal video signal. Loss of the external video signal for more than a predetermined number of lines causes the overlay system to switch to an internal signal only mode. Return to the external video signal upon its restoration is delayed until the internal and external signals are resynchronized, thereby preventing picture instability.
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Citations
20 Claims
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1. A video signal mixing system comprising:
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an input means for receiving an external composite video signal; a horizontal synchronization pulse detecting means connected to said input means for detecting the horizontal synchronization pulses of said first composite video signal; an external signal loss detector connected to said input means for detecting and indicting the loss for longer than a first predetermined period of time greater than the period of said horizontal synchronization pulses the loss of said external composite video signal; a video clock frequency standard for determining a frequency; a video clock signal generating means connected to said horizontal synchronization pulse detecting means and said external signal loss detector for generating a video clock signal, said video clock signal generating means having a horizontal phase lock loop means connected to said horizontal synchronization pulse detecting means including a horizontal controlled oscillator for generating internal horizontal synchronization pulses in phase synchronization with said detected horizontal synchronization pulses, and a video clock phase lock loop means connected to said horizontal phase lock loop means and said video clock frequency standard including a video clock controlled oscillator for generating said video clock signal having a frequency corresponding to and corrected by the frequency of said internal horizontal synchronization pulses when said external signal loss detector does not indicate the loss of said external composite video signal and having a frequency corresponding to said frequency determined by said video frequency standard when said external signal loss detector indicates loss of said external composite video signal, whereby momentary loss of said external composite video signal for a time less than said predetermined period of time causes said frequency of said video clock signal to be controlled by said horizontal controlled oscillator; a video signal generating means connected to said video clock signal generating means for generating an internal composite video signal in synchronization with said video clock signal thereby generating said internal composite video signal having horizontal lines in synchronism with said detected horizontal synchronization pulses; and a video switching means connected to said input means, said external signal loss detector and said video signal generating means having an output means for selectively connecting either said external composite video signal or said internal composite video signal to said output means, said video switching means selecting said internal composite video signal when said external signal loss detector indicates loss of said external composite video signal, whereby said output means receives a combined video signal having synchronized horizontal lines. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A video signal mixing system comprising:
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an input means for receiving an external composite video signal; a horizontal synchronization pulse detecting means connected to said input means for detecting the horizontal synchronization pulses of said external composite video signal; a color burst amplitude detector connected to said input means for detecting the amplitude of the color burst of said external composite video signal; a video signal generating means connected to said horizontal synchronization pulse detecting means and said color burst amplitude detector for generating a internal composite video signal having horizontal lines in synchronism with said detected horizontal synchronization pulses and having color modulation corresponding to said detected amplitude of said color burst of said external composite video signal, whereby said internal composite video signal has the same color saturation as said external composite video signal; and a video switching means connected to said input means, and said video signal generating means having an output means for selectively connecting either said external composite video signal or said internal composite video signal to said output means, whereby said output means receives a combined video signal having synchronized horizontal lines. - View Dependent Claims (9)
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10. A video signal mixing system comprising:
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a first input means for receiving a first composite video signal; a horizontal synchronization pulse detecting means connected to said first input means for detecting the horizontal synchronization pulses of said first composite video signal; a first composite video signal loss detector connected to said first input means for detecting and indicating the loss for longer than a first predetermined period of time greater than the period of said horizontal synchronization pulses the loss of said first composite video signal; a video clock frequency standard for determining a frequency; a video clock signal generating means connected to said horizontal synchronization pulse detecting means and said first composite video signal loss detector for generating a video clock signal for enabling generation of a second video signal having horizontal lines synchronized with said detected horizontal synchronization pulses, said video clock signal generating means having a horizontal phase lock loop means connected to said horizontal synchronization pulse detecting means including a horizontal controlled oscillator for generating internal horizontal synchrnization pulses in phase synchronization with said detected horizontal synchronization pulses, and a video clock phase lock loop means connected to said horizontal phase lock loop means and said video clock frequency standard including a video clock controlled oscillator for generating said video clock signal having a frequency corresponding to and corrected by the frequency of said internal horizontal synchronization pulses when said first composite video signal loss detector does not indicate the loss of said first composite video signal and having a frequency corresponding to said frequency determined by said video frequency standard when said first composite video signal loss detector indicates loss of said first composite video signal, whereby momentary loss of said first composite video signal for a time less than said predetermined period of time causes said frequency of said video clock signal to be controlled by said horizontal controlled oscillator; a second input means for receiving a second video signal having a luminance signal and two color difference signals; a video encoding means connected to said video clock phase lock loop and said second input means for generating a second composite video signal from said luminance signal and said two color difference signals; and a video switching means connected to said first input means, said first composite video signal loss detector and said video encoding means having an output means for selectively connecting either said first composite video signal or said second composite video signal to said output means, said video switching means selecting said second composite video signal when said first composite video signal loss detector indicates loss of said first composite video signal, whereby said output means receives a combined video signal having synchronized horizontal lines. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17)
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18. A video signal mixing system comprising:
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a first input means for receiving a first composite video signal; a horizontal synchronization pulse detecting means connected to said first input means for detecting the horizontal synchronization pulses of said first composite video signal; a color burst amplitude detector connected to said input means for detecting the amplitude of the color burst of said first composite video signal; a second input means for receiving a second video signal having a luminance signal and two color difference signals; a video encoding means connected to said horizontal synchronization pulse detecting means, said second input means and said color burst amplitude detector for generating a second composite video signal from said luminance signal and said two color difference signals having horizontal lines in synchronism with said detected horizontal synchronization pulses and having color modulation corresponding to said detected amplitude of said color burst of said first composite video signal, whereby said second composite video signal has the same color saturation as said first composite video signal; and a video switching means connected to said input means, and said video encoding means having an output means for selectively connecting either said first composite video signal or said second composite video signal to said output means, whereby said output means receives a combined video signal having synchronized horizontal lines. - View Dependent Claims (19)
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20. A video signal mixing system comprising:
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a first input means for receiving a first composite video signal; a horizontal synchronization pulse detecting means connected to said first input means for detecting the horizontal synchronization pulses of said first composite video signal; a video clock signal generating means connected to said horizontal synchronization pulse detecting means for generating a video clock signal having a frequency corresponding to the frequency of said detected horizontal synchronization pulses for enabling generation of a second video signal having horizontal lines synchronized with said detected horizontal synchronization pulses; a second input means for receiving a second video signal having a luminance signal and two color difference signals; a video encoding means connected to said video clock signal generating means and said second input means for generating a second composite video signal from said luminance signal and said two color difference signals; a video switching means connected to said input means, and said video encoding means having an output means for selectively connecting either said first composite video signal or said second composite video signal to said output means, whereby said output means receives a combined video signal having synchronized horizontal lines; and said video mixing system being embodied in two integrated circuits, a first analog integrated circuit including said first input means, said second input means, said video encoding means and said video switching means and a second digital integrated circuit including said horizontal synchronization pulse detecting means and said video clock signal generating means.
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Specification