Design and implementation of an LD-CELP codec

This paper discusses the design and implementation of a low bit rate codec along with its performance at different bit rates. The International Telecommunications Union´s G.728 CELP speech coder is specifically designed for low coding delay and toll quality speech at a rate of 16kbps. Here, we present the design of a CELP(Code Excited Linear Prediction) algorithm similar to the above coder, but can compress speech up to rates like 6.4kbps(as in the G.723.1 standard). This codec shares the advantages of both the above standards; it has a low delay (up to 1.25ms) and greater compression, even though the techniques used are simpler. This advantage makes this coder suitable for applications like video conferencing, mobile communications etc.