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Common description
Low bit rate MELP (Mixed Excitation Linear Prediction)
speech coder with rate 2400 bps uses 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.
The full list of transmitting bits is presented in table:
Transmitted parameters |
Parameter |
Voiced frame |
Unvoiced frame |
Linear spectral pairs (LSP) |
25 |
25 |
Fourier amplitudes |
8 |
- |
Gain (2 per frame) |
8 |
8 |
Pitch, V/UV flag |
7 |
7 |
Band voicing flags |
4 |
- |
Aperiodical flag |
1 |
- |
Forward error correction |
- |
13 |
Synchronization bit |
1 |
1 |
Total per frame 22.5 ms |
54 |
54 |
More precise description of standard MELP 2400 bps algorithm
you can find here:
Specifications for the Analog to Digital Conversion of Voice
by 2,400 Bit/Second Mixed Excitation Linear Prediction. - May 28, 1998
- Draft.
Standard MELP 2400 bps vocoder has fixed-point ANSI-C
model for PC and real-time implementation on the base of DSP TMS320C54x.
Real-time implementation on the base of DSP TMS320C55x will be done on
demand. Please ask for it.
| Processor loading
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MELP encoder |
MELP decoder |
| Peak loading per channel, MIPS |
21.7 |
6.7 |
| 28.4 |
| Memory |
| program, K words |
7.58 |
| tables, K words |
8.05 |
| data, K words |
2.2 + 2.66 * N |
| All, K words |
17.83 + 2.66 * N |
Here you can test speech quality of standard MELP 2400 bps algorithm
by listening following speech samples:
Original english speech |
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MELP vocoder 2400 bps |
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 Common description
Implementation
Speech samples
All technical and commercial questions about products, prices,
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