Network Echo Canceller
by D2 Technologies, Inc.

Software Overview

D2's Network Echo Canceller voice-processing algorithm module is an ITU-T G.165- and Deutche 
Bundesposte-compliant network echo canceller that operates in fast adapt, slow adapt, and fixed 
modes.
Designed to the VP Open interface, the Network Echo Canceller module easily integrates with other 
VP Open modules, runs in real-time concurrently with other VP Open modules, and handles any number 
of voice ports assigned to the DSP. Like all of D2's algorithm modules, the Network Echo Canceller 
consists of robust software that is rigorously tested and field proven.

Features and Benefits

•	Exceeds G.165 and Deutche Bundesposte requirements for codec or linear data
•	Programmable echo tails from 8 msec to 96 msec
•	Operates in fast adapt, slow adapt, and fixed modes
•	Programmable minimum Echo Return Loss (ERL) of 0, 3, and 6 dB
•	Non-linear processing (NLP) and comfort noise options

Processor and System Specifications

•	Devices supported: TMS320C5x
•	Processor resource required:
•	Algorithm category: Telecommunications
TMS320C5x
Program memory
4.7 kwords
Data memory/port
1.6 kwords for 32 msec tails
Processor loading
worst case
4.8 MIPS (tails of 32–96 msec and fast adaptation) 
4.0 MIPS (slow adaptation), 3.3 MIPS (fixed cancellation)

Usage Limitations or Performance Considerations

•	The host, voice data input and output, memory allocation, and module to module communication 
interfaces must conform to VP Open as described in the VP Open Software Interface Specification.

Algorithm Verification

D2's Network Echo Canceller algorithm module is validated through the following suite of tests:
•	Standard G.165 and Deutsche Bundeposte test suites for tails of 32-96 msec:  steady state 
residual echo with and without NLP, convergence test with and without NLP, convergence in the 
presence of near end noise, halting of convergence by double-talk, halting of convergence by large 
continuous background noise, long tails test, leak rate test, infinite return loss convergence 
test, tone disable and stability test, and NLP
•	VP Open interface validation – the module is integrated with other VP Open modules and tested 
concurrently in real-time on the D2 VDS50 system for multiple voice ports

Availability

Currently available for the TMS320C5x. A demonstration package is currently available for the Texas 
Instruments EVM50 DSP board.

Company Background and Contact Information

D2 Technologies, Inc. was founded by David Y. Wong and David M. Lindsay to help companies innovate 
telecommunications and information products with voice processing technology, which include 
telephony and voice algorithms, real-time system software, and development services.

Contact:	D2 Technologies, Inc.
		Attn:  Product Sales
		104 West Anapamu Street
		Suite J
		Santa Barbara,  CA 93101
		(805) 564-3424
		Fax:  (805) 966-2144
		e-mail:  sales@d2tech.com