IP Library › Granted Patent US 7,098,961
Granted Patent B2
US 7,098,961 · App. 10/746,921 · Granted Aug 29, 2006

Horizontal sync pulse detection for video signal decoding

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Quick Facts
Patent No.
US 7,098,961
App. No.
10/746,921
Granted
Aug 29, 2006
Kind
B2
Abstract

Methods and systems are described for determining a slice level used for detecting an edge of a horizontal sync pulse of a horizontal line of a video signal, where the horizontal line has a plurality of samples. An exemplary method comprises low-pass filtering the video signal to generate a plurality of filtered samples; determining a first level, wherein a predetermined number of the plurality of filtered samples have levels above the first level; determining a second level, wherein the second level is a minimum level of levels for the plurality of filtered samples; and determining the slice level by adding the first level and the second level to generate a summed level, and dividing the summed level by two to determine the slice level.

Claims (66)

1. A method of determining a slice level used for detecting an edge of a horizontal sync pulse of a horizontal line of a video signal, said horizontal line having a plurality of samples, said method comprising:

low-pass filtering said video signal to generate a plurality of filtered samples;

determining a first level, wherein a predetermined number of said plurality of filtered samples have levels above the first level;

determining a second level, wherein said second level is a minimum level of levels for said plurality of filtered samples; and

determining said slice level based on said first level and said second level.

2. The method of claim 1 , wherein said determining said slice level comprises:

adding said first level and said second level to generate a summed level; and

dividing said summed level by two to determine said slice level.

3. The method of claim 1 , wherein said predetermined number is 88% of said plurality of samples.

4. The method of claim 1 , wherein said plurality of samples are approximately 1,825 samples.

5. The method of claim 4 , wherein said predetermined number is approximately 1,600.

6. The method of claim 1 , wherein said first level is a back porch level of said horizontal line.

7. The method of claim 1 , wherein said second level is a sync level of said horizontal line.

8. The method of claim 1 , wherein said determining said first level includes:

initializing said first level with an arbitrary level;

comparing a sample level of each said plurality of samples with said first level;

incrementing a counter for each sample level greater than said first level;

subtracting said pre-determined number from said counter after receiving said plurality of samples for said horizontal line; and

adjusting said first level based on said subtracting.

9. The method of claim 8 , wherein said adjusting includes:

increasing said first level if said subtracting generates a positive result;

decreasing said first level if said subtracting generates a negative result; and

maintaining said first level if said subtracting generates a zero result.

10. A system for determining a slice level used for detecting an edge of a horizontal sync pulse of a horizontal line of a video signal, said horizontal line having a plurality of samples, said system comprising:

a low-pass filter configured to filter said video signal to generate a plurality of filtered samples;

a first level detection block configured to determine a first level, wherein a predetermined number of said plurality of filtered samples have levels above the first level;

a second level detection block configured to determine a second level, wherein said second level is a minimum level of levels for said plurality of filtered samples; and

a slice level block configured to determine said slice level based on said first level and said second level.

11. The system of claim 10 , wherein said slice level block includes an adder configured to add said first level and said second level to generate a summed level, and a divider configured to divide said summed level by two to determine said slice level.

12. The system of claim 10 , wherein said predetermined number is 88% of said plurality of samples.

13. The system of claim 10 , wherein said plurality of samples are approximately 1,825 samples.

14. The system of claim 13 , wherein said predetermined number is approximately 1,600.

15. The system of claim 10 , wherein said first level is a back porch level of said horizontal line.

16. The system of claim 10 , wherein said second level is a sync level of said horizontal line.

17. The system of claim 10 , wherein said first level detection block includes:

an integrator initialized to an arbitrary level;

a comparator configured to compare a sample level of each said plurality of samples with said first level;

a counter configured to count each sample level greater than said first level; and

an adder configured to subtract said pre-determined number from said counter after receiving said plurality of samples for said horizontal line;

wherein said integrator is further configured to adjust said first level based on said subtracting.

18. The system of claim 17 , wherein said integrator adjusts said first level by:

increasing said first level if said subtracting generates a positive result;

decreasing said first level if said subtracting generates a negative result; and

maintaining said first level if said subtracting generates a zero result.

19. A system for determining a slice level used for detecting an edge of a horizontal sync pulse of a horizontal line of a video signal, said horizontal line having a plurality of samples, said system comprising:

means for low-pass filtering said video signal to generate a plurality of filtered samples;

means for determining a first level, wherein a predetermined number of said plurality of filtered samples have levels above the first level;

means for determining a second level, wherein said second level is a minimum level of levels for said plurality of filtered samples; and

means for determining said slice level based on said first level and said second level.

20. The system of claim 19 , wherein said means for determining said slice level comprises:

means for adding said first level and said second level to generate a summed level; and

means for dividing said summed level by two to determine said slice level.

21. The system of claim 19 , wherein said predetermined number is 88% of said plurality of samples.

22. The system of claim 19 , wherein said plurality of samples are approximately 1,825 samples.

23. The system of claim 22 , wherein said predetermined number is approximately 1,600.

24. The system of claim 19 , wherein said first level is a back porch level of said horizontal line.

25. The system of claim 19 , wherein said second level is a sync level of said horizontal line.

26. The system of claim 19 , wherein said first level is initialized with an arbitrary level, and wherein said means for determining said first level includes:

means for comparing a sample level of each said plurality of samples with said first level;

means for incrementing a counter for each sample level greater than said first level;

means for subtracting said pre-determined number from said counter after receiving said plurality of samples for said horizontal line; and

means for adjusting said first level based on said subtracting.

27. The system of claim 26 , wherein said means for adjusting includes:

means for increasing said first level if said subtracting generates a positive result;

means for decreasing said first level if said subtracting generates a negative result; and

means for maintaining said first level if said subtracting generates a zero result.