  Linear predictive coders form an important class of speech coders. This paper
describes the software level implementation of linear prediction based
vocoders, viz. Code Excited Linear Prediction (CELP), Low-Delay CELP (LD-CELP)
and Mixed Excitation Linear Prediction (MELP) at bit rates of 4.8 kb/s, 16 kb/s
and 2.4 kb/s respectively. The C programs of the vocoders have been compiled
and executed in Linux platform. Subjective testing with the help of Mean
Opinion Score test has been performed. Waveform analysis has been done using
Praat and Adobe Audition software. The results show that MELP and CELP produce
comparable quality while the quality of LD-CELP coder is much higher, at the
expense of higher bit rate.
