Non-square Quadtree Transform Coefficients Energy Distribution Model and Improvement of the Scanning Pattern

The conventional coefficients scanning pattern of the non-square quadtree transform can not fit the energy distribution better enough, which worsens the coding efficiency. In order to improve the coding efficiency, a non-square quadtree transform coefficients energy distribution model is proposed and the coefficients scanning pattern is improved in this paper. The position distribution in spatial frequency domain of the non-square quadtree transform block is deduced. Based on this distribution, the energy distribution model is proposed theoretically. The model is verified by experiment. It is found from the experiment result that the energy decrease gradually from the top-left corner to lower-right corner, and the energy in lower left corner is close to that in upper right corner. According to the energy distribution model, the quantized coefficients scanning pattern in non-square quadtree transform is rebuilt to fit the entropy coding, where the scanning pattern prefers to an ascending order in coefficients.