Method and device to estimate motion in a sequence of moving pictures
First Claim
1. A method to estimate motion in a sequence of television type moving pictures, where each picture is formed by a determined number of light spots located at intersections of lines and columns, said method of the type where motion is estimated by performing a gradient algorithm which minimizes a mean square deviation between local variations in luminance of a current pel of the picture and those of a pel in a similar position to the current pel in the prior image, said method comprising the steps of:
- initializing an algorithm by displacement values estimated according to several directions within a close causal neighborhood of the current pel and of the propagation of each estimate in a scanning direction of picture lines,choosing a propagating direction for the algorithm depending on a position, in the picture, of a line to which the current pel belongs,calculating a modulus of a gradient of the current pel and comparing the result with a pre-determined threshold value,choosing a displacement for the present pel in the causal neighborhood of this pel when the modulus of the gradient obtained is below the pre-determined threshold value, andchoosing the displacement that gives the smallest displaced frame difference, or estimating a new displacement when the gradient modulus obtained is above the predetermined threshold.
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Abstract
The method consists in estimating motion by performing a gradient algorithm which minimalizes the mean square deviation of local luminance variations of the present pel of the picture with the pel that is homologous with it in the prior picture, in initializing the execution of the algorithm by displacement values estimated along several directions within the close causal neighborhood of the present pel and in propagating each estimate in the scanning direction if the picture lines.
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Citations
24 Claims
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1. A method to estimate motion in a sequence of television type moving pictures, where each picture is formed by a determined number of light spots located at intersections of lines and columns, said method of the type where motion is estimated by performing a gradient algorithm which minimizes a mean square deviation between local variations in luminance of a current pel of the picture and those of a pel in a similar position to the current pel in the prior image, said method comprising the steps of:
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initializing an algorithm by displacement values estimated according to several directions within a close causal neighborhood of the current pel and of the propagation of each estimate in a scanning direction of picture lines, choosing a propagating direction for the algorithm depending on a position, in the picture, of a line to which the current pel belongs, calculating a modulus of a gradient of the current pel and comparing the result with a pre-determined threshold value, choosing a displacement for the present pel in the causal neighborhood of this pel when the modulus of the gradient obtained is below the pre-determined threshold value, and choosing the displacement that gives the smallest displaced frame difference, or estimating a new displacement when the gradient modulus obtained is above the predetermined threshold. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16)
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17. A device for implementation of a method to estimate motion in a sequence of television type moving pictures, where each picture is formed by a determined number of light spots located at intersections of lines and columns, of the type where motion is estimated by performing a gradient algorithm which minimizes a mean square deviation between local variations in luminance of a current pel of the picture and those of a pel which is homologous to it in the prior image, where the method includes the steps of initializing an algorithm by displacement values estimated according to several directions within a close causal neighborhood of the current pel and of the propagation of each estimate in a scanning direction of picture lines, choosing a propagating direction for the algorithm depending on a position, in the picture, of a line to which the current pel belongs, calculating a modulus of the gradient of the current pel and comparing the result with a pre-determined threshold value, choosing a displacement for the present pel in the causal neighborhood of this pel when the modulus of the gradient obtained is below the pre-determined threshold value, and choosing the displacement that gives the smallest displaced frame difference, or estimating a new displacement when the gradient modulus obtained is above the pre-determined threshold, said device comprising:
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a picture memory to store the luminance values of a determined number of pels surrounding the pel of P(z,t-1) of a coordinate z in the picture homologous with the current pel P(z,t) in the picture frame IMS.sub.(t-1) preceding the current pel frame IMS.sub.(t), a device to compute the modulus of the luminance gradient of the current pel, a first decision element and a second decision element, a displacement estimating device, and a switching device, the outputs of the two decision elements being coupled to elements of the switching device controlled by the gradient modulus computing device, said switching device controlled such that if the value of the current gradient modulus is smaller than or equal to a pre-determined threshold value, the displacement chosen is the one coming from the second decision element, otherwise, the displacement chosen is the one coming from the first decision element. - View Dependent Claims (18, 19, 20, 21, 22, 23, 24)
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Specification