Fading of main video signal without affecting display of superimposed video signal
AssigneeLSI Logic Corporation
InventorNing Xue
Life of this patent
Estimating the term…
Abstract
A fade circuit adjusts the luma as well as one or more chroma components of a main video so that the fade ins and fade outs of the main video do not change the color of an on-screen display image, such as the volume bar. In one embodiment, luma component (Y) is adjusted by subtracting a fade factor from the luma component to form a faded luma component. At the same time, one or more chroma components (Cb and Cr) are scaled by (1) subtracting a predetermined value from the chroma component to form a resultant, (2) multiplying the resultant with a scale factor to form a product, and (3) adding the predetermined value to the product to form a faded chroma component.
Claims19
A method for fading a video signal, the method comprising:
- changing a first chroma value in response to a scale factor to form a faded chroma value;
- changing a first luma value by subtracting a fade factor to form a faded luma value;
- displaying a pixel generated from at least the faded chroma and the faded luma values;
- mixing the faded chroma value with a second chroma value to form a mixed chroma value;
- and
- mixing the faded luma value with a second luma value to form a mixed luma value.
A circuit for fading a video signal comprising a fade circuit comprising:
- a first arithmetic unit having (i) a first port coupled to a first bus carrying a chroma signal and (ii) a second port coupled to a second bus carrying a scale signal, wherein the first arithmetic unit adjusts the chroma signal using the scale signal;
- a second arithmetic unit having (i) a third port coupled to a third bus carrying a luma signal and (ii) a fourth port coupled to a fourth bus carrying a fade signal, wherein the second arithmetic unit adjusts the luma signal using the fade signal;
- and
- a clipper having a fifth port coupled to a fifth bus of the second arithmetic unit, wherein the fifth bus carries a difference between the luma signal and the fade signal, the clipper outputs on a sixth bus (1) a maximum signal when said difference is greater than the maximum signal, (2) a minimum signal when said difference is less than the minimum signal, or (3) said difference when said difference is less than the maximum signal and greater than the minimum signal.
A method for fading a video signal, the method comprising:
- changing a first chroma value in response to a scale factor to form a faded chroma value;
- changing a first luma value by subtracting a fade factor to form a faded luma value;
- displaying a pixel generated from at least the faded chroma and the faded luma values;
- and
- mixing the faded chroma value with a second chroma value to form a mixed chroma value.
Dependencies are inferred from the claim text.