De-interlacing of video data

Abstract

A method and apparatus are provided for deriving a progressive scan image from an interlaced image. In this, for each pixel to be inserted in the field from the interlaced image a difference value is derived from each pair of a set of symmetrically opposed pixels with respect to the pixel to be reconstructed and from adjacent lines to the pixel to be reconstructed. A determination is made as to which pair of pixels has the lowest difference value associated with it and the average value of this pixel is selected as a value of the pixel to be inserted.

1 . A method for deriving a progressive scan image from an interlaced image in which for each pixel to be inserted in a field from the interlaced image the method performs the steps of: 
 a) deriving a difference value from each pair of a set of pairs of symmetrically opposed pixels with respect to the pixel and from adjacent lines to the pixel to be inserted;    b) determining which pair of pixels has the lowest difference value associated with it; and    c) selecting as the value of the pixel to be inserted, the average of the pair of pixels which has the lowest difference value.    
     
     
         2 . A method according to  claim 1  wherein each of said set of pairs of pixels is composed of one pair only.  
     
     
         3 . A method according to  claim 1  wherein each of the sets of pairs of pixels comprises pixels in a plurality of rows.  
     
     
         4 . A method according to  claim 1  wherein each of the sets of pixels comprises a plurality of pixels and has a centre at a reference point, adjacent to the pixel to be inserted.  
     
     
         5 . A method according to  claim 1  further including the step of comparing the average value of the pair of pixels with the lowest difference value with a range of values defined by the values of pixels above and below the pixel to be inserted, and clamping the value of the pixel to be inserted to a point in the range in dependence on the result of the comparison.  
     
     
         6 . A method according to  claim 1  including the step of first deriving average values for each pair of the set of pairs of pixels, determining which pairs have averages which fall within a range of values between the values of pixels above and below the pixel to be inserted, and in which steps b) and c) are performed only for pixels whose averages fall within this range.  
     
     
         7 . Apparatus for deriving a progressive scan image from an interlaced image comprising means for deriving a difference value from each pair of a set of pairs of symmetrically app pixels with respect to a pixel to be inserted in the image from adjacent lines to the pixel to be inserted; 
 means for determining which pair of pixels has the lowest difference value associated with it; and    means for selecting as the value of the pixel to be inserted the average value of the pair of pixels which has the lowest difference value.