Automatic phase control apparatus for phase locking the chroma burst of analog and digital video data using a numerically controlled oscillator
First Claim
1. A video display system comprising:
- a. a receiving circuit configured for receiving an analog input composite video signal having a first phase and a first frequency, and a digital input composite video signal having a second phase and a second frequency;
b. a transmitting circuit configured for outputting an output composite video signal representing a predetermined ratio of the analog input composite video signal and the digital input composite video signal; and
c. an automatic phase and frequency correction circuit coupled to the receiving circuit and to the transmitting circuit for monitoring the first phase, the second phase, the first frequency and the second frequency and ensuring that the second phase and the second frequency are equal to the first phase and the first frequency, wherein the analog input composite video signal is a master signal and is not adjusted and the digital input composite video signal is a slave signal and is adjusted so that the second phase equals the first phase and the second frequency equals the first frequency.
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Accused Products
Abstract
A video/graphics overlay integrated circuit receives an analog composite video signal and a digital composite video signal and combines them in a predetermined format into an output composite video signal which is transmitted to a display device such as a television set. The digital video signal may be comprised of digital video, graphics data or a combination of digital video and graphics data. The digital video and graphics data are encoded by a digital encoder integrated circuit into a digital composite video signal. The digital composite video signal is coupled to the video/graphics overlay integrated circuit. An automatic phase correction circuit detects any phase difference between the burst signals of the analog composite video signal and the digital composite video signal. A phase control signal is generated by the automatic phase correction circuit and used to correct the phase and frequency of the digital composite video signal and ensure that it corresponds to the phase and frequency of the analog composite video signal. The automatic phase correction circuit uses the analog composite video signal as the master and adjusts the phase and frequency of the digital composite video signal until they are locked to the phase and frequency of the analog composite video signal. A numerically controlled oscillator generates an appropriate oscillating sinusoidal signal representing a burst frequency signal within the digital composite video signal. The phase and frequency of the oscillating sinusoidal signal are appropriately monitored and adjusted to correspond with the phase and frequency of the analog composite video signal.
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Citations
28 Claims
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1. A video display system comprising:
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a. a receiving circuit configured for receiving an analog input composite video signal having a first phase and a first frequency, and a digital input composite video signal having a second phase and a second frequency; b. a transmitting circuit configured for outputting an output composite video signal representing a predetermined ratio of the analog input composite video signal and the digital input composite video signal; and c. an automatic phase and frequency correction circuit coupled to the receiving circuit and to the transmitting circuit for monitoring the first phase, the second phase, the first frequency and the second frequency and ensuring that the second phase and the second frequency are equal to the first phase and the first frequency, wherein the analog input composite video signal is a master signal and is not adjusted and the digital input composite video signal is a slave signal and is adjusted so that the second phase equals the first phase and the second frequency equals the first frequency. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A video display system for receiving video input signals and outputting an output composite video signal comprising:
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a. an analog input video receiving circuit configured for receiving an analog input video signal having a first phase and a first frequency; b. a digital input video receiving circuit configured for receiving a digital input video signal having a second phase and a second frequency; c. a phase and frequency detecting circuit coupled to receive a first signal representative of the first phase and the first frequency and a second signal representative of the second phase and the second frequency for detecting a difference between the first signal and the second signal and generating a control output signal representative of the difference signal; and d. a correction circuit coupled to receive the control output signal for adjusting the second phase and the second frequency in response to a magnitude of the control output signal. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17)
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18. An automatic phase correction circuit configured for receiving an analog video signal having a first phase and a first frequency, and a digital input composite video signal having a second phase and a second frequency, comprising:
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a. means for generating an output video signal including a predetermined ratio of the analog video signal and the digital input composite video signal; b. means for comparing the first phase and the first frequency with the second phase and the second frequency; and c. means for adjusting, coupled to the means for generating and to the means for comparing, for adjusting the second phase and the second frequency in order to lock the second phase to the first phase and the second frequency to the first frequency. - View Dependent Claims (19, 20, 21, 22, 23)
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24. A method of automatically adjusting a phase and frequency of an encoded digital composite video signal to lock to a phase and frequency of an analog video signal comprising the steps of:
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a. receiving an analog video signal having a first phase and a first frequency; b. receiving an encoded digital composite video signal having a second phase and a second frequency; c. monitoring the first phase, the first frequency, the second phase and the second frequency; d. detecting a first difference between the first phase and the second phase and a second difference between the first frequency and the second frequency; e. adjusting the encoded digital composite video signal in order to eliminate the first and second differences; and f. generating an output composite video signal including a predetermined ratio of the analog video signal and the encoded digital composite video signal. - View Dependent Claims (25, 26, 27, 28)
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Specification