DSP implementation of low bit-rate CELP based speech orders

Low bit-rate speech coding techniques are very important in applications where power and bandwidth are very limited. Prime requirements for speech coding are low bit-rate, high quality and low implementation cost. Since 1984 CELP coding of speech has been most popular at medium to low bit-rates. The major drawback of CELP coding, however, has been its large computational requirement. The authors report on the real-time implementation of a CELP coder in a single DSP32C floating-point processor on a four-layer single Eurocard size board with its appropriate input/output stages and 32 kbytes of external RAM. They also report on various complexity reduction techniques that they have employed to achieve a single DSP solution for both encoder, decoder and a very effective voice activity detection (VAD) devices