Patents Assigned to Packeteer Incorporated
  • Publication number: 20020131645
    Abstract: A method of JPEG compression of an image frame divided up into a plurality of non-overlapping, tiled 8×8 pixel blocks Bij where i, j are integers covering all of the blocks in the image frame. A global quantization matrix Q is determined by either selecting a standard JPEG quantization table or selecting a quantization table such that the magnitude of each quantization matrix coefficient, Qij is inversely proportional to a visual importance, Iij, to the image of a corresponding DCT basis vector. Next a linear scaling factor Sij is selected which defines bounds over which the image is to be variably quantized. Transform coefficients, Dijmn, obtained from a digital cosine transform of Bij, are quantized and the quantized coefficients Tijmn and Q*Smin are entropy encoded, where Smin is a user selected minimum scaling factor, to create a JPEG image file. The algorithm is unique in that it allows for the effect of variable-quantization to be achieved while still producing a fully compliant JPEG file.
    Type: Application
    Filed: January 16, 2001
    Publication date: September 19, 2002
    Applicant: Packeteer Incorporated
    Inventor: Chris H. Hamilton