A Comparative Analysis of Vocoders for Communications in Portuguese

This paper analyzes the performance of voice encoders used for digital communications, especially in VoIP calls, for Brazilian Portuguese phonemes. The focus is the adaptation capacity of encoders to vocal tract changes in these intervals during the signal processing. Short sentences containing all the basic Portuguese phonemes were used. Information about fundamental frequency and the three first formants was extracted, for each interval, for a group formed by men and women of different ages. These intervals were created using the software Praat, which was also used to extract all the parameters. The results obtained showed a subtle difference in signal processing of the formant frequencies between sexes. It was observed a phenomenon of pitch correction in some intervals with a variant phoneme for both sexes. The encoders G.722, G.723.1, G.726, G.728, G.729A, iLBC and Speex were analyzed