Performance Comparison of Linear Prediction based Vocoders in Linux Platform
This is an incremental comparison of existing speech coding methods for Linux platform users.
The paper implemented three linear prediction-based vocoders (CELP, LD-CELP, MELP) at different bit rates on Linux and evaluated them using subjective testing and waveform analysis. Results showed MELP and CELP had comparable quality, while LD-CELP achieved much higher quality at a higher bit rate.
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.