CONCEALMENT OF DAMAGED BLOCK TRANSFORM CODED IMAGES USING PROJECTIONSONTO CONVEX-SETS

An algorithm for lost signal restoration in block-based still image an d video sequence coding is presented, Problems arising from imperfect transmission of block-coded images result in lost blocks, The resultin g image is flawed by the absence of square pixel regions that are nota bly perceived by human vision, even in real-time video sequences, Erro r concealment is aimed at masking the effect of missing blocks by use of temporal or spatial interpolation to create a subjectively acceptab le approximation to the true error-free image, This paper presents a s patial interpolation algorithm that addresses concealment of lost imag e blocks using only intra-frame information, It attempts to utilize sp atially correlated edge information from a large local neighborhood of surrounding pixels to restore missing blocks, The algorithm is a Gerc hberg-type spatial domain/spectral domain constraint-satisfying iterat ive process, and may be viewed as an alternating projections onto conv ex sets method.