Low-delay techniques are proposed for coding 7 kHz speech using subban
d code-excited linear predictive coding (CELP). The use of separate an
d joint index codebooks is compared. Specifically, the joint-index-sub
band CELP (JISBC) algorithm is found to provide good quality with proc
essing delay in the range 2.375-3.375 ms at corresponding bit rates of
16-8 k bit/s.