'C3x Full-Duplex 
Speakerphone Algorithm
by SignalWorks Inc.

Software Overview

SignalWorks Acoustic Echo Cancellation (AEC) Software technology facilitates high-quality 
full-duplex voice communication for various applications. The end-user experiences a pleasant 
speakerphone experience with no clipping, dropouts, or echo. The algorithm is compatible with ITU 
G.165 and G.167 recommendations and supports the signal quality requirements for speech codecs 
including G.728, G.722, G.711. The SignalWorks proprietary, patent pending, algorithm makes fast 
convergence, long tail-length, and MIPs efficient solutions possible on both fixed-point and 
floating-point platforms.
The software is highly optimized for the 'C3x architecture. Processor utilization and memory 
requirements are tail-length dependent. For a 256-millisecond tail-length less than 9-kwords data 
memory and 7-kwords program memory are required, and less than 14 MIPs are consumed. Only 256 words 
of 'C3x internal memory is required for reasonably efficient operation making this software ideal 
for the 'C32 memory configuration. It is also possible to run the algorithm with more than 
zero-wait states without a significant MIPs impact.

Features and Benefits

•	Low MIPs on long tail length.
•	Proven in videoconferencing and PC speakerphones.
•	Supports narrowband and wideband modes.
•	Trains on voice; no training sequence required.
•	Fast continuous adaptation to changing acoustic conditions.


Processor and System Requirements

Devices supported:	Supports 'C3x or 'C4x
Algorithm category:	Audio
Program memory:		7 kwords includes narrowband and wideband modes
Data memory:		9 kwords for 256 millisecond tail-length
Processor loading:
12.5-MIPs narrowband (8-kHz sample rate)
14.5-MIPs wideband (16-kHz sample rate)

Algorithm Verification

Conforms with ITU G.165, G.167 echo cancellation specifications.
Compatible with known speech codecs including G.728 and G.722.

Availability

•	Available now for `C3x
•	Please call regarding `C5x availability

Company Background

SignalWorks has developed audio solutions for clients in teleconferencing and videoconferencing 
applications.
The foundation of SignalWorks technology is state-of-the-art acoustic echo cancellation technology 
necessary for high-performance full-duplex speakerphone applications. SignalWorks is completely 
focused on speakerphone technology.
SignalWorks licenses proprietary full duplex speakerphone technology and provides related support 
and consulting services. SignalWorks' experience with microphones, loudspeakers, POTS, H.320, and 
PC conferencing significantly reduces the system integration time and effort.

Contact:	Hugh McLaughlin
		SignalWorks
		625 Ellis St. Suite 208
		Mountain View, CA 94043
		USA
		(415) 254-0186
		fax: (415) 254-0187
		e-mail: 70474.252@compuserve.com