MELPe - enhanced Mixed-Excitation Linear Predictive Plus

ADT MELPePlus SPEECH CODERC55x

ADT MELPe SPEECH CODER C64x,C64x+, C6416, C674 OMAP

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 bps MELPe

Sampling Rate: 8 kHz

Data sheet .pdf

FEATURES

Functions are C-callable
Multiple channel capable
Optional noise preprocessing
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

Software - MELPePlus	600 bps		1200 bps		2400 bps
Software - MELPePlus	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

Memory Resource Requirements
All memory usage is given in bytes.

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

C64x™, C64x+™ DSP Generation

Memory Resource Requirements
All memory usage is given in bytes.
Channel data is included with Data Memory

C64	Program	Channel	Scratch	Tables	Data
Encoder	188.4k	6560	5672	148k	63k
Decoder		1376
NPP		11968

C64+	Program	Channel	Scratch	Tables	Data
Encoder	191k	6560	6984	163k	70k
Decoder		1376
NPP		11968

CPU Resource Requirements: C64x, C64x+, OMAP

MIPS (C6416)	MIPS (600bps)	MIPS (1200 bps)	MIPS (2400 bps)
Nonlinear Preprocessor (NPP)	12.2	12.2	13.3
Encoder	23.7	27.5	23.4
Decoder	15.7	22.5	17.9

MIPS (C64+)	MIPS (600bps)	MIPS (1200 bps)	MIPS (2400 bps)
Nonlinear Preprocessor (NPP)	11.4	11.5	13.7
Encoder	23.4	23.5	24.8
Decoder	15.1	15.1	17.4

MIPS (C674 OMAP) Cache Enabled	MIPS (600bps)	MIPS (1200 bps)	MIPS (2400 bps)
Nonlinear Preprocessor (NPP)	11.4	11.5	13.7
Encoder	23.4	23.5	24.8
Decoder	15.1	15.1	17.4

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.