IMPROVED BIT PLANE COMPRESSION METHOD

摘要

Both the frequency weighting and region of interest enhancement in MEPG4-FGS are implemented by shifting in a number of zeros in the least significant bits of selected discrete cosine transform (DCT) coefficients, by application of a weighting matrix. This effectively shifts these coefficients up a few bit planes, thereby causing their bits to appear earlier in the enhancement layer bit stream than would otherwise be the case. Thus they are given priority over coefficients that have not been shifted or have been shifted by a smaller amount in the event that the bit stream is cut. To propose herein to modify the enhancement layer bits stream of the MEPG4-FGS standard so that zeros that are shifted in are no longer encoded, thereby increasing the compression efficiency when either no or only a small number of bits is cut off from the enhancement layer.