Backward Linear Prediction for Lossless Coding of Stereo Audio
Philippe Gournay, Jean-Luc Garcia, Roch Lefebvre · Journal of the Audio Engineering Society · 2004
Lossless audio coding aims at achieving the lowest possible bitrate for transmission or storage of audio without any loss of information. This is usually done by first removing redundancy from the audio signal, and then applying entropy coding to the residual signal. Linear prediction (LP), when applied to monophonic signals, is a very effective way to remove redundancy. It produces minimum-phase predictors that are efficiently compressed by combining vector quantization with a meaningful representation of the LP coefficients (such as the LSFs). When applied to stereo signals however, joint channel prediction often produces non-minimum-phase predictors, whose quantization requires a high bit rate and poses stability problems. In this paper, we show that backward estimation of the LP coefficients (where those are estimated on the past decoded signal) solves most of the problems associated with the use of joint channel prediction in a lossless audio coder.