Optimization of MPEG-2 SNR scaleable codecs

It is shown how the signal-to-noise (SNR) scaleable coder can benefit from optimizing quantified discrete cosine transform (DCT) coefficients, in a rate-distortion context, in order to reduce bit-rate overheads. The technique is based on adjusting the quantized coefficients rather than dropping them, since the former gives finer control over rate-distortion trade-offs. The widely used Lagrangian optimization technique is then applied to arrive at the optimally adjusted coefficients block. We show that such an optimization is very efficient for the second layer, but has little effect on the base layer.