Method and decoder system for reducing quantization effects of a decoded image

Abstract

A method (200) and decoder system (100) for reducing quantization effects or ringing artifacts imposed upon decoded image of hybrid block based coding schemes such as MEPG and H 261. The system (100), in use, and method (200) receive (220) decoded image decoded blocks that were decoded from transform coded blocks quatized by a selected quantization parameter. The system (100) and method (200) then analyze (230) selected pixel values of selected pixels with neighboring pixel values of associated neighboring pixels in the decoded blocks to determine difference values for each of the selected pixels. Potential object edges, of the decoded image represented by the decoded blocks, are then detected (240) to identify the selected pixels as edge pixels, the detecting is effected by comparing the difference values with selected threshold values that are determined with respect to the selected quantization parameter associated with the blocks. The selected threshold values have a non-linear relationship with varying quantization parameter values of the image. The selected pixel values are modified (250) if they are not identified as edge pixels.

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