Compandent's STANAG-4591 compliant MELPe suite also enables on the fly varying data rate (VDR) among the 2400/1200/600 bps rates, for varying channel conditions. Note that the STANAG-4591 standard reference, and also TSVCIS Narrowband (NB) vocoder which is basically STANAG-4591, do not implement this feature of good sounding VDR. Varying the rate in the STANAG-4591 standard reference implementation generates hursh artifacts that can render the speech unintelligible. However, Compandent developed and implemented an excellent solution that solved this problem and allows for smooth transitions from one vocoder rate to another on the fly.
Varying data rate (VDR) capability is useful in varying channel conditions. The standard reference STANAG-4591 MELPe was designed to operate at one of three possible independent rates (2400/1200/600 bps), and did not enable varying the rate on the fly. Each rate was designed to operate and implemented in isolation from the other rates. In other words, the STANAG-4591 (and TCVCIS NB) reference implementation was multi-rate but not VDR. Compandent enhanced its STANAG-4591 compliant MELPe implementation to allow for varying data rate on the fly for varying channel conditions. The resulted speech quality is remarkable and without noticable artifacts.
Contact Us
For more information about Compandent's MELPe sounds better than the standard reference implementation, please contact us by our contact form or by phone at 650-241-9231.