Results on low-delay vector excitation coding (LD-VXC) obtained byusing adaptive lattice filters for implementing the short-term predictorand the perceptual weighting filter are discussed. The new codec, thelattice LD-VXC (LLD-VXC), is based on a backward adaptiveanalysis-by-synthesis configuration in which a least-mean-square (LMS)recursive algorithm is used for updating the lattice filters. Theshape-only codebook and the gain-shape codebook are compared as possiblecandidates for the excitation codebook. The performance of the LLD-VXCcodec versus the short-term predictor order is studied. It is shown thatthe performance increases for short-term predictor orders of up to 20-30and then saturates. A LLD-VXC codec with a pitch predictor and ashort-term predictor or order 20 achieves the same speech quality as asystem without a pitch predictor and with a short-term predictor oforder 50, and the LLD-VXC codec offers toll speech quality at 16 kb/swith moderate complexity and a total communications delay of under 2 ms
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