Adaptive post-filtering of reconstructed image data in a video encoder

摘要

Disclosed is a method of encoding image data in which adaptive post-filtering is applied to a reconstructed image. The reconstructed (or rough) image is obtained by first encoding pixel values in an original image into coefficients (such as in a Discrete Cosine Transform, DCT encoder) and then subjecting the coded image data to an inverse transform to obtain the rough decoded image. This rough decoded image is then processed through an adaptive post filter that is adjustable depending on an input parameter derived based on values of the original image. In one embodiment the post filtering is adjustable as a function of an input parameter that depends on a frame merit. The post filter may be a de-blocking filter (DBF), a sample adaptive offset filter (SAO) or an adaptive loop filter (ALF) and the input parameter may be a rate-distortion slope or a quantisation parameter. The filter parameters may be added to the encoded bit-stream to be used by an adaptive post-filter in a HEVC (High Efficiency Video Coding) decoder.