Masking of transformed intra-predicted blocks for high quality image and video coding

Many professional applications for image and video coding require very high levels of quality of the decoded signal. Under these conditions, even state-of-the-art standards such as High Efficiency Video Coding (HEVC) may not provide sufficient compression efficiency. Large values of the residual samples, especially at high frequency components, are difficult to encode and result in high bitrates of the coded signal. A novel scheme for image and video coding is presented in this paper to enhance compression at high quality levels, based on separate transform to the frequency domain of original and prediction signals. Selected frequency components of the prediction signal are discarded by means of appropriate masking patterns prior to the residual computation. The optimal masking pattern is selected for each transformed block and signalled in the bitstream. The approach is shown achieving gains against conventional HEVC under high quality constraints when coding both still images and video sequences.