Real-time implementation of a 9.6 kbit/s ACELP wideband speech coder

The real-time implementation of a wideband ACELP speech coder at 9.6 kb/s is presented. The coder is implemented on a TMS320C30 floating-point DSP chip. The attempt to implement an ACELP coder for wideband speech in real time results in 3-4 times more complexity than that for narrowband speech. Very efficient algorithms for searching the pitch and codebook parameters have been introduced. The pitch search was brought down to 20% of real time by the combination of an efficient open-loop approach and a decimation procedure. The excitation search complexity was significantly reduced by using two codebooks. The first models the main features in the excitation and is very efficiently searched using focused search. The second has a simple structure and does not need exhaustive search. The quality of the encoded wideband speech at 9.6 kb/s was judged vastly superior to that of the original narrowband speech