Patent ID: 7490123
Filing Date: 2009-02-10
Classification: H04N

Abstract:
1. A data compression apparatus for performing data compression on input data, said apparatus comprising: a quantisation parameter estimation unit configured to detect whether input data is source data or non-source data, said non-source data having undergone a previous compression/decompression cycle, and derive an estimated value of a quantisation parameter used in a previous compression/decompression cycle applied to said input data if non-source data is detected, by detecting rounding effects in data values of at least a subset of said input data, said quantisation parameter estimation unit is configured to detect rounding effects by identifying one or more frequencies of occurrence of respective one or more particular sequences of ones and zeros corresponding to a respective predetermined number of least significant bits of said input data; and a parameter selection unit configured to select a quantisation parameter for use in compression of said input data based on receiving the detection result on whether input data is source data or non-source data from the quantisation parameter estimation unit and, if non-source data is detected, the estimated value of the quantisation parameter used in a previous compression/decompression cycle received from the quantisation parameter estimation unit.