Testing MELPe (enhanced MELP)

[John Reilley]

Hi everyone,

I heard that MELP or more precisely that MELPe (enhanced MELP) is
probably the best vocoder (voice coder) that is available in real-time
and low complexity for rates 2400 bits/sec and below, so we want to
explore it further.

What we'd like is to run some quality testing on the MELPe vocoder and
to compare it to other vocoders in different conditions and speech data,
preferably in real-time. Also, we want to be able to connect MELPe
vocoder (preferably using hardware: board, device) to our system (either
serial link or IP link would work). It has to be not too expensive
(i.e. not a custom project) and yet reliable. Any suggestion how we can
do that? What's the best option / vendor around?

Thanks,
JR

[MELPeWiz]

See in the following links, looks like an excellent choice of MELPe device:

http://www.compandent.com/products_flexi232.htm
http://www.compandent.com/products_MELPe.htm
http://www.MELPe.com/
http://www.compandent.com/

FLEXI-232 Low-Cost MELPe Data Terminal Equipment (DTE)

Compandent offers low-cost Data-Terminal Equipment (DTE) for interfacing
vocoders (such as MELPe) with external Data Communication Equipment
(DCE) such as modems or crypto devices. For example, Compandent’s
Flexible-Link for EXternal Instrument using RS-232 (FLEXI-232) is a
low-cost card that can be used as DTE connected to various external
devices such as modems or crypto device using RS-232 or other protocols.
It is easy to use, just plug-and-play, and comes with optional
Push-To-Talk (PTT) switch for your convenience. The FLEXI-232 board, may
be mounted to DSK board (such as the DSK5416, DSK5510, DSK6416 and the
OMAP) or PC-104 DSP board that runs vocoders such as MELPe, G729,
G723.1, etc.. The FLEXI-232 is an extremely versatile board that can be
programmed to handle any required standard or customized communication
protocol (beyond what a typical DSP may be capable of) including
MIL-STD-188-114, RS-232, RS-422, RS-423, USB, TCP-IP Ethernet, 802.11b/g
Wireless, etc.. It also has user friendly control and set-up interface.
In addition, the FLEXI-232 has general purpose I/O lines that can be
customized to your special needs. It can be also delivered as a
standalone portable device in appropriate enclosure.

Also, see: http://www.compandent.com/products_melpe.htm

MELPe - Enhanced Mixed-Excitation Linear Predictive Vocoder

Compandent's MELPe (MELPe-Plus-Plus) produces better quality than the
standard reference! Compandent has been supporting and improving the
MELPe real-time implementation, and has found and fixed numerous bugs in
it, many of these bugs could not be discovered by simply processing the
standard Test Vectors, rather than by comprehensive process of analyzing
and optimizing the code and testing it under wide variety of scenarios
and conditions conducted by Compandent's speech coding and DSP experts.
We can show you examples where the standard reference produces hoarse
speech or annoying clicks while Compandent's MELPe (MELPe++) produces
much better sounding and cleaner speech. Therefore Compandent's MELPe
(MELPe++) is in fact better than the standard reference! Compandent has
also greatly improved and optimized the code. Compandent has ported
MELPe to various DSPs by Texas Instruments such as TMS320c54xx,
TMS320c55xx, TMS320c64xx, and OMAP.

The MELPe-Plus-Plus software suite includes the following features:

hand optimized Assembly real-time implementation of all algorithm components
extensively analyzed, tested, fixed, and improved real-time implementation
C-callable high-level functions
optional components available (customer can select desired combination):
MELPe at 2400 bps - high rate encoder and/or decoder
MELPe at 1200 bps - low rate encoder and/or decoder
MELPe at 600 bps - very low rate encoder and/or decoder
compressed bit-stream transcoding between the rates
noise pre-processor - for reducing background noise
postfilter - for quality enhancement of the reproduced speech
multi-channel implementation
example of main C program that initializes and runs the MELPe vocoder
functions
"Packetized-Network-Ready" - to maintain high quality even in severe FER
conditions
operation mode can be switched on the fly (no need to reload the program
to the DSP)
easy and fast Test Vectors running and verification setup
comprehensive and spectacular Real-Time demo, using DIP-switch control
and LEDs indicators
comprehensive and detailed documentation that allows for smooth and easy
integration
Compandent support and service
very low-cost (about $400) complete DSP development board and tools
(CCS) on which Compandent's MELPe may run, process the Test Vectors, and
spectacular real-time audio demo
System solution FLEXI-232 and FLEXI-PC104 : Cost-effective board and
software for customized communication link to your modem or other equipment.

[stra...@gmail.com]

There's lots of helpful information and data about the MELP vocoder and MELPe codec at:
Http://www.melpe.com
Incluing implementations, software, hardware and solutions