Controlling the combining of video signals
First Claim
1. Apparatus for controlling the combining of video signals, so as to produce a composite picture in which a first picture represented by a first video signal is inserted into a second picture represented by a second video signal with such composite picture having a plurality of horizontal scanning lines, and each of said scanning lines including a row of pixels, said apparatus comprising:
- generating means for generating edge data defining respective edges of a polygon which correspond to edges of said first picture;
line rate microprocessor means responsive to said edge data to generate information for each horizontal scanning line of said composite picture in which the row of pixels corresponding to the respective scanning line is intersected by edges of said first picture, said information representing horizontal locations of first and second start pixels, said first and second start pixels being pixels in which first and second edges, respectively, of said first picture start to intersect said row of pixels corresponding to said respective scanning line;
gradients of said first and second edges; and
a start key value for each of said first and second start pixels which is equal to a proportion of said first picture to said composite picture contained in said first and second start pixels, respectively; and
key value generator means responsive to said information for each horizontal scanning line of said composite picture to generate a respective key value for each successive pixel in the respective row of pixels in which the key values for pixels preceding said first start pixel are zero, said key values for pixels following said first start pixel are incremented by an amount per pixel determined by said gradient of said first edge until the key value reaches a value of unity; and
said key values for pixels following said second start pixel are decremented by an amount per pixel determined by said gradient of said second edge until the key value reaches zero.
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Accused Products
Abstract
Apparatus for controlling the combining of video signals includes a field rate microprocessor (10) that generaes edge data defining the edges of a polygonal first picture (KP) which is to be keyed into a second picture (B) to produce a composite picture. Two line rate microprocessors (16, 18) generate from the edge data, for each horizontal scanning line of the composite picture in which a row of pixels corresponding to that scanning line is intersected by edges of the first picture, signals representing: the horizontal locations of first and second start pixels, namely those of the row of pixels in which first and second edges (e.g. Eb, E2), respectively, of the first picture (KP) start to intersect the row; the gradients of the first and second edges; and a key value (the proportion of the first picture to be contained in a pixel of the composite picture) for each of the first and second start pixels. A key value generator (32) generates, for each scanning line of the composite picture, a key value for each successive one of the row of pixels corresponding thereto, by: ramping up the key value from zero, for pixels preceding the first start pixel, by incrementing the key value for the first start pixel, for pixels following the first start pixel, by an amount per pixel determined by the gradient of the first edge (e.g. E1), until the key vaue reaches unity; and ramping down the key value from unity, by decrementing the key value for the second start pixel, for pixels following the second start pixel, by an amount per pixel determined by the gradient of the second edge (e.g. E2), until the key value reaches zero.
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Citations
17 Claims
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1. Apparatus for controlling the combining of video signals, so as to produce a composite picture in which a first picture represented by a first video signal is inserted into a second picture represented by a second video signal with such composite picture having a plurality of horizontal scanning lines, and each of said scanning lines including a row of pixels, said apparatus comprising:
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generating means for generating edge data defining respective edges of a polygon which correspond to edges of said first picture; line rate microprocessor means responsive to said edge data to generate information for each horizontal scanning line of said composite picture in which the row of pixels corresponding to the respective scanning line is intersected by edges of said first picture, said information representing horizontal locations of first and second start pixels, said first and second start pixels being pixels in which first and second edges, respectively, of said first picture start to intersect said row of pixels corresponding to said respective scanning line;
gradients of said first and second edges; and
a start key value for each of said first and second start pixels which is equal to a proportion of said first picture to said composite picture contained in said first and second start pixels, respectively; andkey value generator means responsive to said information for each horizontal scanning line of said composite picture to generate a respective key value for each successive pixel in the respective row of pixels in which the key values for pixels preceding said first start pixel are zero, said key values for pixels following said first start pixel are incremented by an amount per pixel determined by said gradient of said first edge until the key value reaches a value of unity; and
said key values for pixels following said second start pixel are decremented by an amount per pixel determined by said gradient of said second edge until the key value reaches zero. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A method of controlling the combining of video signals, so as to produce a composite picture in which a first picture represented by a first video signal is inserted into a second picture represented by a second video signal, with such composite picture having a plurality of horizontal scanning lines, and each of said scanning lines including a row of pixels, said method comprising the steps of:
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generating edge data defining respective edges of a polygon which correspond to edges of said first picture; generating information from said edge data for each horizontal scanning line of said composite picture in which the row of pixels corresponding to the respective scanning line is intersected by edges of said first picture, said information representing horizontal locations of first and second start pixels, said first and second start pixels being pixels in which first and second edges, respectively, of said first picture start to intersect said row of pixels corresponding to said respective scanning line;
gradients of said first and second edges; and
a start key value for each of said first and second start pixels which is equal to a proportion of said first picture to said composite picture contained in said first and second start pixels, respectively; andgenerating in response to said information for each horizontal scanning line of said composite picture a respective key value for each successive pixel in the respective row of pixels in which the key values for pixels preceding said first start pixel are zero, said key values for pixels following said first start pixel are incremented by an amount per pixel determined by said gradient of said first edge until the key value reaches a value of unity; and
said key values for pixels following said second start pixel are decremented by an amount per pixel determined by said gradient of said second edge until the key value reaches zero. - View Dependent Claims (12, 13, 14, 15, 16, 17)
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Specification