The main advantage of ACELP is that the algebraic codebook it uses can be made very large (> 50 bits) without running into storage (RAM/ROM) or complexity (CPU time) problems.
A 16-bit algebraic codebook shall be used in the innovative codebook search, the aim of which is to find the best innovation and gain parameters. The innovation vector contains, at most, four non-zero pulses.
In ACELP a block of N speech samples is synthesized by filtering an appropriate innovation sequence from a codebook, scaled by a gain factor g c, through two time varying filters.
The long-term or pitch, synthesis filter is given by: 1/B(z) = 1/(1 - gpz-T)
The short-term synthesis filter is given by: H(z) = 1/A(z) = 1/(1 + ZIGMAi = 1 to Paiz-i)