Patent ID: 6011864
Filing Date: 2000-01-04
Classification: G06T,H04N

Abstract:
A computer-implemented method for transforming a block of pixels within a frame of a digitized video image using a selectable one of a set of transform functions, each transform function having an inverse transform function, and each block having a predetermined set of image characteristics, the method comprising the steps of:associating the transform functions with the set of image characteristics, with predetermined quantization values, and with adjustable thresholds associated with the image characteristics;obtaining respective characteristic values for the image characteristics of a block;selecting a transform function from the set of transform functions based on comparisons between said characteristic values and said adjustable thresholds;applying said transform function to the block to form a transformed block;quantizing said transformed block using a quantization value to form a quantized block;selecting an inverse transform function whose application minimally covers said quantized block;inversely quantizing said quantized block to form an inversely quantized block;applying said inverse transform function to said inversely quantized block to form a decoded block;obtaining a quality value for said decoded block by obtaining a peak signal-to-noise ratio for said decoded block;updating said adjustable thresholds based on said quality value and said characteristic values;establishing histograms of characteristic values for each of the image characteristics and associated transform functions and quantization values;recording said characteristic values in histograms referenced by said transform function and said quantization value;selecting a statistical function to apply to said histograms;applying said statistical function to said histograms; andupdating said adjustable thresholds with data from application of said statistical function to said histograms byselecting an order statistic based on the quality value, transform function, and quantizer value;applying said order statistic to said histograms to obtain new thresholds; andupdating said adjustable thresholds with said new thresholds.