Compandent's MELPe also enables varying date rate among 2400/1200/600 bps on the fly for varying channel conditions, while the standard reference does not enable that feature. Varying the rate in the 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 allowed 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 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 reference implementation was multi-rate but not VDR. Compandent enhanced its 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.
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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.