Robust MELP vocoder 4800 bps
Robust MELP vocoder with rate 4800 bit/s (RMELP 4800 bps) is intended for using in discrete channels with bit error rates (BER) up to 7-9%.
Robust MELP vocoder is built on the base of low bit rate MELP vocoder and original channel coding scheme using codes with high bit error correction capability.
Low bit rate MELP (Mixed Excitation Linear Prediction) speech coders use classical parametric model of description of speech signals. This model is implemented on the base of linear prediction filter with mixed excitation in several frequency bands.
Independent estimation of voiced/unvoiced decision in different frequency bands is providing more natural synthetic speech sounding then quality of classical LPC vocoders with binary voiced/unvoiced decision for single band.
RMELP 4800 bps is implemented as fixed-point ANSI-C models for PC. It also has real-time implementations on the base of TMS320c54xx DSP families.
DSP implementations have following features:
Parameters of RMELP 4800 bps TMS320C54xx implementation:
N – number of channels
Parameters of RMELP 4800 bps TMS320C55xx implementation will be sent on demand. Please ask.
Here you can test speech quality of following speech samples of RMELP 4800 bps vocoder with different channel bit error rates (BER) with or without error bit grouping. (In case of modeling of error bit grouping we use 2 state Hilbert model with BER probability and PGB probability that mean probability of transition channel from "good" state to "bad" state and vice versa.)
For example here you can listen the standard USA FS-1016 CELP 4800 bps vocoder in the same channel conditions:
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