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MELPe - enhanced Mixed-Excitation Linear Predictive Plus

Vocoders by Adaptive Digital

ADT MELPePlus SPEECH CODERC55x

DESCRIPTION

Adaptive Digital's enhanced-MELP (MELPe) the new Federal Standard, is a low bit rate vocoder supporting 2400, 1200 and 600 bps. It can operate at half the rate of the MELP standard.

Enhancements include: Improved encoding/decoding, transcoding between 2400, 1200 and 600 bps bit streams, and noise preprocessing for removing background noise.

MELPe provides better quality than all older military standards, especially in noisy environments such as battlefield, vehicles and aircraft. MELPe is suitable for use by OEM customers for VoIP, telecom, military, secure voice & radio, and other low bit-rate compressed speech applications.

MELPe vocoder is also known as military standard MIL-STD-3005 and NATO STANAG 4591

Coding Rate: 2400, 1200, and 600 bpsMELPe

Sampling Rate: 8 kHz

FEATURES

  1. Functions are C-callable
  2. Multiple channel capable
  3. Optional noise preprocessing
  4. Transcodes between rates

FRAME SIZE

The Melpe coder frame size is dependent on the Encode/Decode rate

Rate Frame Size (Samples) Frame Size (msec.)
600 bps 720 90 .0
1200 bps 540 67.5
2400 bps 180 22.5

 

AVAILIBILITY

ADT MELPePlus is available on the TMS320C5000™ DSP Family

C55xx™ DSP Generation

C55x™ DSP Generation

MIPS (Peak) CPU Resource Requirements
Software - MELPePlus 600 bps 1200 bps 2400 bps
Max Average Max Average Max Average
Encode 34.2 32.5 46.5 41.3 29.7 26.6
Decode 12.7 10.7 14.4 11.2 14.8 13.3
Noise Preprocessor (NPP) 19.6 18.7 20.0 19.0 21.8 20.5

 


All memory usage is given in bytes.

C55x Memory Resource Requirements
Software Program Memory Channel Scratch Tables Data
Encoder 78.3k 6560 6984 162k 5k
Decoder 1600
NPP 11968


FUNCTIONS

MELPE_ADT_initEncode (…) Initializes the MELPe encoder
MELPE_ADT_initDecode (…) Initializes the MELPe decoder
MELPE_ADT_encode (…) Executes the MELPe encoder
MELPE_ADT_decode (…) Executes the MELPe decoder
NPP_ADT_init (…) Initializes the Melpe noise pre-processor
NPP_ADT_process (…) Executes the Melpe noise pre-processor

APPLICATIONS

Military communications requiring a lower bit rate, used in narrow band channels.

 



 

PRODUCTS