In this study, a modification to ISO MPEG-1 and MPEG-2 digital video coding standards is proposed and preliminary results on its performance are reported. The proposed modification aims to improve the visual quality of MPEG-1 and MPEG-2 coding at medium-to-low bit-rate regimes by eliminating the blocking effect caused by the Discrete Cosine Transform. This goal is achieved without introducing a significant change in the MPEG hierarchy and algorithm. The theory of Lapped Orthogonal Transforms which constitutes a rather recently introduced tool for block transform coding suggests that they can reduce the blocking effect to very low levels. Hence, in the modified MPEG-like system, instead of the original two dimensional Discrete Cosine Transform a Lapped Orthogonal Transformation is used as the basic spatial correlation reduction operation and also customized quantization and variable length codeword tables are provided to ensure efficiency. The modified coding algorithm is implemented in software. Simulations are made to compare its performance to the original MPEG-1 algorithm. As performance criteria, PSNR versus compression ratio (equivalently bit-rate) plots and also subjective ratings of visual quality are used.
Download Full PDF Version (Non-Commercial Use)