by Liang-Jin Lin.
The author says “The control scheme defined in MPEG Test Model 5 provides
a solution with very light computational overhead. However, the results are not
always good for any given video sequence and channel rates. It is also difficult
to adjust parameters to improve the quality without the help of some trial and
error encoding tests. Moreover, it does not control the buer to prevent buer
overflow. Several rate-distortion (R-D) based techniques have been proposed.
The new approaches solved all these problems and generate better and more
stable results. However, these approaches are complex because they require the
R-D characteristics of the input data to be measured before making quantization
assignment decisions.
In this research, we show how the complexity of computing the R-D data can be
reduced without reducing too much the performance of the optimization procedure.”

http://sipi.usc.edu/~ortega/PhDTheses/LiangjinLin.pdf