Joint optimization of LPC and closed-loop pitch parameters in CELP coders

Abstract

In code-excited linear prediction (CELP) coders, computation of linear prediction coefficient (LPC) parameters is generally performed open-loop, and subsequently the pitch predictor parameters are found for each subframe by a closed-loop search. To improve these two parameter sets we propose a new closed-loop joint search technique for joint optimization, called the joint pitch and LPC (JP-LPC) method. When applied to a reference CELP coder, performance gains include an overall improvement in segmental signal-to-noise ratio (SNR) of 0.61 dB and for subframes with high pitch periodicity, a gain of 0.83 dB.