Low-complexity frame-size down-scaling integrated with IDCT

This work develops a low-complexity method that integrates the inverse transform and downscaling. According to the application requirement, the reduction ratios of the frame width and length are adopted at the matrix computation of the inverse transform. Since a small matrix is employed to compute the inverse transform and downscaling, the non-zero high-frequency components are compensated at the spatial and frequency domains. As compared to the conventional methods, the computational complexity of proposed method with the frequency-domain compensation can be reduced effectively under the similar decoded picture quality. Particularly, the proposed method can meet various downscaling ratios to accomplish low-complexity transforms for mobile video applications.