Rate-control Techniques in the Latest Visual Compression Standards – a Survey

In lossy compression, the quantisation introduces distortions and allows the encoder to adjust the size of the output stream to a desired bandwidth. The ratedistortion (RD) theory says that for a given source with known statistical properties and a given distortion measure, there exists a function, R(D), called the rate-distortion function which determines the best possible compression rate R(D) for arbitrary amount of tolerable distortion D. The typical shape of the R(D) function is depicted in Fig. 1. When the compression is lossless (D=0), the best possible compression rate is the entropy rate, H.