Enhanced Mixed Excitation Linear Predictive (MELPe) Vocoder is implemented in accordance with STANAG 4591 standard as three standalone software:
- 2400 bps vocoder,
- 1200 bps vocoder,
- 600 bps vocoder,
If you need Dual-Rate or Triple-Rate Vocoder in any combination of the bit rates, please inform us and we will customize our software under your requirements.
Our MELPe implementation differs by high optimization, in spite of the fact that MELPe algorithm requires a lot of computational resources and memory.
Features:
We used ITU-T P.50 multilanguage speech base and ITU-T P.862 utility to estimate speech quality for each bit rate.
Speech quality of the MELPe vocoder is:
- about 3.3 PESQ for 2400 bps rate,
- about 3.1 PESQ for 1200 bps rate,
- about 2.6 PESQ for 600 bps rate
If your application doesn't require strict usage of the standard, we recommend to use our proprietary vocoders (SPR Classic or SPR Robust). These vocoders provide the same speech quality, however have all other characteristics much better in comparison with MELPe.
SPEECH QUALITY
We passed encoded bit streams through AWGN channel simulator with various SNR and estimated quality of decoded speech for each bit rate.
MELPe provides good robustness in channel with low errors.
However, it provide a poor robustness in channel with errors more than 1%.
If you need a high-robust vocoder and if usage of the standard is not required strictly in your application, we recommend to use our proprietary vocoders of the "SPR Robust" line.
ROBUSTNESS
Time delay is very important characteristic of communication system. Algorithmic delay of vocoder does play determinative role in total delay of communication system.
MELPe vocoder has the following algorithmic delay:
- 42,5 ms for 2400 bps rate,
- 103,7 ms for 1200 bps rate,
- 110 ms for 600 bps rate
If your application doesn't require strict usage of the standard, we recommend to use our proprietary vocoders (SPR Classic or SPR Robust), which have much less time delay in comparison with MELPe.
ALGORITHMIC DELAY
Computing complexity defines both a cost and a power consumption of the end-user equipment.
MELPe Object Code for TI's C55xx DSP requires:
- about 36 MIPS for 2400 bps rate,
- about 44 MIPS for 1200 bps rate,
- about 44 MIPS for 600 bps rate
If your application doesn't require strict usage of the standard, we recommend to use our proprietary vocoders (SPR Classic or SPR Robust), which require much less of the resources in comparison with MELPe.
COMPUTING COMPLEXITY
A cost of the end-user equipment is depended upon memory volume, which is required for used software.
As you can see on the figure, MELPe requires relatively a lot memory, in low bit rate eminently.
If your application doesn't require strict usage of the standard, we recommend to use our proprietary vocoders (SPR Classic or SPR Robust), which require much less of the resources in comparison with MELPe.
MEMORY USAGE
Enhanced Mixed Excitation Linear Predictive (MELPe) vocoder is available right now as:
- Object Code for ADI's Blackfin DSP,
- DLL (Win32) for PC
Also it is available for any other DSP, RISC or general-purpose platform during two-three months.
AVAILABILITY
Download:
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