Syntax-constrained encoder optimization using adaptive quantization thresholding for JPEG/MPEG coders

The authors show a rate-distortion optimal quantization technique to threshold the DCT coefficients in the industry image and video coding standards JPEG and MPEG respectively. Their scheme achieves a decent thresholding gain in terms of both objective SNR (about 1 dB) as well as perceived quality and uses a fast dynamic programming recursive structure which exploits certain monotonicity characteristics of the JPEG and MPEG codebooks to drastically reduce the complexity. The primary advantage of their encoding algorithm is that it is completely compatible with the baseline JPEG and MPEG decoders