PLT: a new class of low-complexity optimal transform coders

Abstract

Transform coding and differential pulse code modulation (DPCM) are two of the most important techniques for signal compression. The Karhunen-Loeve transform (KLT) is the optimal unitary transform that maximizes the coding gain. For DPCM coder, the optimal linear predictor maximizes its coding gain. In this paper, we will provide a connection between KLT and DPCM. A new class of nonunitary transform called Prediction-based Lower triangular Transform (PLT) is introduced. We will show that PLT is a special case of vector prediction, when the predictor is a lower triangular matrix. PLT has the same coding gain as KLT but its design and computational cost is much lower. In addition, it has many other desired features that make it a good choice for signal compression.