Thomas Mccarthy

DCT coding for motion video storage using adaptive arithmetic coding

Abstract We describe a motion compensated hybrid DCT/DPCM video compression scheme, which has been proposed for the storage of compressed digital video. The scheme, an extension of a current CCITT/ISO proposal for compressing still-frame images, differs from other hybrid DCT proposals in several ways. (1) Reduction of DCT block-artifacts by implementing inverse AC-quantizers which are of finer granularity than the corresponding encoder quantizers. This process, which we label ‘AC-Correction’, is applied to intraframe coded frames. (2) Entropy coding by means of an adaptive binary arithmetic coder. Arithmetic coding results in better compression efficiency than Huffman coding, thus improving image quality when a fixed bandwidth channel is available. (3) Non-linear loop filtering that preserves edge definition. (4) Tight tolerances in the rate control of groups of frames.