Automatic phase control apparatus for phase locking the chroma burst of analog and digital video data using a numerically controlled oscillator

• US 6,014,176 A
• Filed: 01/11/1996
• Issued: 01/11/2000
• Est. Priority Date: 06/21/1995
• Status: Expired due to Term

• Current Assignee: Sony Corporation (Sony Group Corp.), Sony Electronics Inc. (Sony Group Corp.)
• Original Assignee: Sony Corporation (Sony Group Corp.), Sony Electronics Inc. (Sony Group Corp.)
• Inventors: Edwards, Steve, Nayebi, Mehrdad
• Primary Examiner(s): LEE, MICHAEL
• Application Number:
  US08/585,398
• Time in Patent Office: 1,461 Days
• Field of Search: 348/505, 348/512, 348/508, 348/516, 348/517, 348/537, 348/559, 348/549, 348/563, 348/584, 348/589, 348/600
• US Class Current: 348/539
• CPC Class Codes: G09G 2320/0266 Reduction of sub-frame artefacts
• CPC Class Codes: G09G 3/2022 using sub-frames
• CPC Class Codes: H04N 5/44504 Circuit details of the additional information generator, e.g. details of the character or graphics signal generator, overlay mixing circuits
• CPC Class Codes: H04N 9/641 Multi-purpose receivers, e.g. for auxiliary information H04N9/642 takes precedence

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.

Claims

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.

2. The video display system as claimed in claim 1 wherein the automatic phase and frequency correction circuit comprises a numerically controlled oscillator for generating a sinusoidal output signal.

3. The video display system as claimed in claim 2 wherein the first phase and first frequency are monitored during a burst period of the analog input composite video signal.

4. The video display system as claimed in claim 3 wherein the second phase and second frequency are monitored during a burst period of the digital input composite video signal.

5. The video display system as claimed in claim 4 wherein the sinusoidal output signal generated by the numerically controlled oscillator represents a burst signal of the digital input composite video signal.

6. The video display system as claimed in claim 1 wherein the output composite video signal is coupled to a display device.

7. The video display system as claimed in claim 6 wherein the display device is a television.

8. The video display system as claimed in claim 7 wherein the video display system is included within a settop box.

9. The video display system according to claim 1 wherein the output composite video signal includes both chrominance and luminance information.

10. A video display system for receiving video input signals and outputting an output composite video signal comprising:

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.

11. The video display system as claimed in claim 10 wherein the correction circuit comprises a numerically controlled oscillator for generating the output signal.

12. The video display system as claimed in claim 11 wherein the output signal is a sinusoidal signal.

13. The video display system as claimed in claim 12 wherein the sinusoidal output signal generated by the numerically controlled oscillator represents a burst signal of the digital input video signal.

14. The video display system as claimed in claim 13 wherein the sinusoidal output signal is combined into the digital input video signal.

15. The video display system as claimed in claim 14 further comprising a video output circuit coupled to receive the analog input video signal and the digital input video signal for combining the analog input video signal and the digital input video signal into an output composite video signal.

16. The video display system as claimed in claim 15 wherein the analog input video signal and digital input video signal are combined in a predetermined ratio into the output composite video signal.

17. The video display system as claimed in claim 16 wherein the output composite video signal is an analog format signal.

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:

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.

19. The automatic phase correction circuit as claimed in claim 18 wherein the means for comparing includes a phase detector circuit for comparing the second phase to the first phase and generating a phase control signal in response to a detected difference between the second phase and the first phase.

20. The automatic phase correction circuit as claimed in claim 19 wherein the means for comparing further includes a numerically controlled oscillator coupled to receive the phase control signal for generating an output signal in response to the phase control signal.

21. The automatic phase correction circuit as claimed in claim 20 wherein the output signal is a sinusoidal signal.

22. The automatic phase correction circuit as claimed in claim 21 wherein the sinusoidal output signal generated by the numerically controlled oscillator represents a burst signal of the digital input video signal.

23. The automatic phase correction circuit as claimed in claim 22 wherein the sinusoidal output signal is combined into the digital input video signal.

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:

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.

25. The method as claimed in claim 24 wherein the step of adjusting is comprised of providing a phase control signal representative of the first difference to a numerically controlled oscillator which generates an oscillator output signal in response to the phase control signal.

26. The method as claimed in claim 25 wherein the oscillator output signal is a sinusoidal output signal.

27. The method as claimed in claim 26 wherein the sinusoidal output signal generated by the numerically controlled oscillator represents a burst signal of the digital input video signal.

28. The method as claimed in claim 27 wherein the sinusoidal output signal is combined into the encoded digital composite video signal.