HCELP: low bit rate speech coder for voice storage applications

There is an increasing need for low cost, fully integrated digital phone systems including telephony functions, fax, hands-free and answering machines. For the latter feature, a high quality, low bit rate speech coder is recommended. It should require only a reasonable complexity to stay competitive in this product range. Recent advances in CELP speech coding have shown the feasibility of this concept for this kind of consumer applications. A 4.8 kbps Hamming code excited linear prediction (HCELP) coder is proposed in this paper with an algebraic structure for the codebook. It features a very fast search algorithm which has been evaluated to be 3 times faster than usual algebraic codebook search procedures. Quality evaluation yielded satisfactory results. Implementation aspects and the integration of the coder in an advanced telephone set are also detailed.