Local edge count heuristic for vector interpolator
View Patent ↗A vector interpolator optimizes the conversion of an interlaced signal to a non-interlaced signal. The vector interpolator improves the visual clarity of slanted features in a displayed image by adjusting the luminance value of each pixel such that the appearance of “steps” or “jaggies” in the features is reduced. For each pixel, the vector interpolator determines a similarity measure for the pixels within a predetermined area around the pixel. From the similarity measure, an angle for interpolation is selected. The luminance value is then interpolated along the selected vector corresponding to the angle and applied to the pixel. One or more ambiguity measures such as a local edge count ambiguity measure may also be computed to indicate the reliability of the computed luminance value.
1. A method for determining the accuracy of an estimated value for a pixel being generated within a window of pixels, comprising:
determining, using a signal processor, a value of each pixel in the window of pixels;
computing a mean value for the window of pixels;
comparing the determined value of each pixel in the window of pixels with the mean value to determine whether each pixel is less than or greater than the mean value;
determining the number of times a pixel having a determined value less than the mean value is horizontally adjacent to a pixel having a determined value greater than the mean value; and
generating, using the signal processor, an ambiguity measure proportional to the determined number, wherein the ambiguity measure is used to produce the estimated value for the pixel being generated.
2. The method of claim 1 , wherein determining the values of the pixels comprises determining luminance values of the pixels.
3. The method of claim 1 , wherein determining the values of the pixels comprises determining chrominance values of the pixels.
4. The method of claim 1 , wherein comparing the determined value of each pixel with the mean value comprises assigning a value of 0 to the pixels having determined values less than the mean value and assigning a value of 1 to pixels having determined values greater than the mean value.
5. The method of claim 4 , wherein determining the number of times a pixel having a determined value less than the mean value is horizontally adjacent to a pixel having a determined value greater than the mean value comprises using an XOR operation on the assigned values of each pair of horizontally adjacent pixels and adding outputs of the XOR operation.
6. The method of claim 1 , wherein the ambiguity measure is proportional to the number of edges in the window.
7. The method of claim 1 , further comprising blending a first interpolated value and a second interpolated value to produce the estimated value for the pixel being generated, wherein the first interpolated value and the second interpolated value are blended using the ambiguity measure as a blending factor.
8. The method of claim 1 , further comprising blending the ambiguity measure with at least one other ambiguity measure to provide an overall ambiguity measure.
9. The method of claim 1 , wherein the ambiguity measure is used as a blending factor.
10. A vector interpolator comprising an ambiguity measure calculator operative to:
determine a value of each pixel in a window of pixels;
compute a mean value for the window of pixels surrounding a pixel being generated;
compare the determined value of each pixel in the window of pixels with the mean value to determine whether each pixel is less than or greater than the mean value;
determine the number of times a pixel having a determined value less than the mean value is horizontally adjacent to a pixel having a determined value greater than the mean value; and
generate an ambiguity measure proportional to the determined number, wherein the ambiguity measure is used to produce an estimated value for the pixel being generated.
11. The vector interpolator of claim 10 , wherein determining the values of the pixels comprises determining luminance values of the pixels.
12. The vector interpolator of claim 10 , wherein determining the values of the pixels comprises determining chrominance values of the pixels.
13. The vector interpolator of claim 10 , wherein comparing the determined value of each pixel with the mean value comprises assigning a value of 0 to the pixels having determined values less than the mean value and assigning a value of 1 to pixels having determined values greater than the mean value.
14. The vector interpolator of claim 13 , wherein determining the number of times a pixel having a determined value less than the mean value is horizontally adjacent to a pixel having a determined value greater than the mean value comprises using an XOR operation on the assigned values of each pair of horizontally adjacent pixels and adding outputs of the XOR operation.
15. The vector interpolator of claim 10 , wherein the ambiguity measure is proportional to the number of edges in the window.
16. The vector interpolator of claim 10 , further operative to blend a first interpolated value and a second interpolated value to produce the estimated value for the pixel being generated, wherein the first interpolated value and the second interpolated value are blended using the ambiguity measure as a blending factor.
17. The vector interpolator of claim 10 , further operative to blend the ambiguity measure with at least one other ambiguity measure to provide an overall ambiguity measure.
18. An apparatus for determining the accuracy of an estimated value for a pixel being generated within a window of pixels, comprising:
means for determining a value of each pixel in the window of pixels;
means for computing a mean value for the window of pixels;
means for comparing the determined value of each pixel in the window of pixels with the mean value to determine whether each pixel is less than or greater than the mean value;
means for determining the number of times a pixel having a determined value less than the mean value is horizontally adjacent to a pixel having a determined value greater than the mean value; and
means for generating an ambiguity measure proportional to the determined number, wherein the ambiguity measure is used to produce the estimated value for the pixel being generated.
19. The apparatus of claim 18 , wherein determining the values of the pixels comprises determining luminance values of the pixels.
20. The apparatus of claim 18 , wherein the means for comparing the determined value of each pixel with the mean value comprises means for assigning a value of 0 to the pixels having determined values less than the mean value and assigning a value of 1 to pixels having determined values greater than the mean value.
21. The apparatus of claim 20 , wherein the means for determining the number of times a pixel having a determined value less than the mean value is horizontally adjacent to a pixel having a determined value greater than the mean value comprises means for using an XOR operation on the assigned values of each pair of horizontally adjacent pixels and adding outputs of the XOR operation.
22. The apparatus of claim 18 , wherein the ambiguity measure is proportional to the number of edges in the window.
23. The apparatus of claim 18 , further comprising means for blending a first interpolated value and a second interpolated value to produce the estimated value for the pixel being generated, wherein the first interpolated value and the second interpolated value are blended using the ambiguity measure as a blending factor.
24. The apparatus of claim 18 , further comprising means for blending the ambiguity measure with at least one other ambiguity measure to provide an overall ambiguity measure.