Image decoding apparatus and image coding apparatus

摘要

When a filtering process on decoded image data is performed using filter parameters, gradient values near the pixel to be the target of the filtering process are calculated. In accordance with the calculated gradient, a single filter parameter is selected from a set of filter parameters. Based on the selected filter parameter, weight coefficients for the filtering process are calculated. Then, using the pixel value to be the processing target, the surrounding pixel values and the calculated weight coefficients, the pixel value after correction of the processing target pixel is calculated. With this process, it is possible to provide an image coding apparatus that can efficiently code an image properly and an image decoding apparatus that can decode an image, by performing a filtering process in accordance with the image characteristics.

主权项

1. An image decoding apparatus comprising;
a filter parameter decoding circuit configured to decode one or more sets of filter parameters from coded data; a filtering circuit configured to perform a filtering process by multiplying weight coefficients and reference pixels that are made up of a pixel to be targeted for the filtering process and pixels in a vicinity of the pixel to be targeted; an index calculating circuit configured to calculate an amount of variation in said reference pixels and an index for said pixel to be targeted by classifying a magnitude of the amount of variation based on a group of predetermined threshold values; and a weight coefficient calculating circuit configured to derive the weight coefficients according to positions of the reference pixels with respect to the pixel to be targeted and a corresponding set of filter parameters, wherein the weight coefficient calculating circuit includes a selecting circuit configured to select said corresponding set of filter parameters from said sets of filter parameters, in accordance with the calculated index.