A 2 ms-delay adaptive code excited linear predictive coder

The technique proposed is based on a feedback adaptation of the LPC and LTP (long-term prediction) coefficients on a block basis, and on an adaptive linear code-book vector quantizer. The authors designed a 12 kb/s coding scheme with high quality, low delay, and low complexity. A 4 kb/s block protection can then be applied to ensure a robust operation at 16 kb/s. The authors give a detailed description of the backward block adapted ACELP for an operation at 12 kbps. They report quality tests including comparisons with the 32 kb/s G.721 and the 13 kb/s GSM. Finally they show that the implementation requires only 11 MIPS on a fixed point 16 bit DSP