Patent ID: 6760481
Filing Date: 2004-07-06
Classification: H04N

Abstract:
A method for processing image data, comprising:a) transforming the image data into sub-bands, the transformed image data for each sub-band comprising a set of transform coefficients, each of said set of transform coefficients having a sign and a value; b) quantizing the transformed image data using successive approximation quantization to produce a bit-stream, the successive approximation being embedded in the coding process and comprising quantisation at a number of successive quantisation levels, each quantisation level having an associated quantisation threshold; and c) coding the bit-stream with significance information to produce a coded bit-stream using a quadtree based method and including sign and refinement information in the coded bit-stream, wherein for a given sub-band at any one of said number of successive approximation quantisation levels, the method comprises:d) determining whether a sub-band contains at least one transform coefficient that is significant with respect to the quantisation threshold defined for said quantisation level; e) if said sub-band contains at least one transform coefficient that is significant with respect to said quantisation threshold, indicating in the coded bit-stream that the sub-band contains at least one significant transform coefficient value using a first significance value; f) if said sub-band does not contain any transform coefficient that is significant with respect to said quantisation threshold, indicating in the coded bit-stream that the sub-band does not contain any significant transform coefficient value using a second significance value; g) if said sub-band contains at least one transform coefficient that is significant with respect to said quantisation threshold, dividing said sub-band into four quadrants and repeating steps d) to g) for each of the quadrants until no further division is possible or until a desired level of division is reached.