MOTOROLA
Semiconductor Software Product Brief DSP56300REFLEXP/D
(Motorola Order Number)
Rev. 0, 09/99
© Motorola, Inc., 1999
RefleXion: Motorola DSP56300
Introduction
RefleXion, the Acoustic Echo Cancellation software now available from Signals + Software,
offers excellent performance in a variety of loud speaking audio systems. Originally for use in
premier roll-about video conferencing terminals, the design has now been crafted for use in digital
desktop applications, such as Digital Simultaneous Voice and Data (DSVD), and for analog
applications such as POTS speaker phone. Sold under license, the RefleXion software is available
for the Motorola DSP56300 range of processors. Where applicable, it can port to any suitable
customer hardware.
Background
The software performs both Wideband and Narrow band acoustic echo cancellation. It enables
loud speaking audio terminals to use full-duplex audio by cancelling the feedback that occurs
between the loud speaker and microphone(s). The echo canceller is designed for use with G.722
specified wideband (0-7 kHz) audio sampled at 16 kHz. A narrowband 8 kHz sampled interface is
also selectable, as is narrowband operation within a 16 kHz sampled environment.
Features and Performance
The software has been extensively tested and optimized in video conferencing environments to
give excellent subjective performance. However, the echo canceller operates in a variety of
environments without the need for any special set-up or adjustment.
Interface Details
The software consists of two subroutines, one for initialization and one for processing. The
initialization routine is normally called only on DSP reset. The processing subroutine operates on
20-sample frames of data. Three buffers are used for data I/O: one for loudspeaker signal
input/output, one for microphone path input, and one for microphone path output. A single control
word can be programmed for echo canceller on/off, wideband/narrowband selection, and other
features.
Algorithm 24 sub-band structure with oversampling, complex adaptive FIR filters.
Additional echo control by adaptive echo attenuation.
Echo tailspan 200 ms to 100 ms lengths cancelled depending on frequency band.
Bandwidth 0 to 7 kHz (wideband mode) or 0 to 3.4 kHz (narrowband mode).
Insertion Delay 60 ms in microphone path (this is not cancellation tail length)
Cancellation depth 30-35 dB, adaptive filters only, up to 75 dB total, echo attenuator in
place.
Convergence time 1-2 s to -30 dB (noise) / 3-5 s to -20 dB (speech), adaptive filters only,
<10 ms to -75 dB, adaptive filters plus echo attenuator.
RefleXion: Motorola DSP56300
1-2 RefleXion: Motorola DSP56300 Motorola
DSP Requirements
DSP Requirements
There are three possible variants of the Acoustic Echo Canceller; one for wideband operation and two
for narrowband operation. The narrowband options depend on whether the system is clocked at 16 kHz
or 8 kHz for the sample data; this allows for efficient narrowband operation within a wideband
hardware environment when narrowband audio is used. In analog speaker phone applications, line
echo cancellation can also be employed, back-to-back with the AEC, to remove hybrid echo. The
various options and their processing load and memory requirements are detailed in the following table.
Availability
The code is available now, under license, for a one-time payment and/or royalties, depending on the
commercial application. Also available are:
Application note
Demonstration system
Support consultancy for code porting and system integration
Acoustic Echo Canceller Program memory
(Words) Data Memory (Words) Processing Load
(MIPS)
Wideband 16kHz sampled 3.6 k 7.7 k < 35
Narrowband 8kHz sampled - - -
Narrowband 16kHz sampled 3.6 k 6.5 k < 26
* The benchmark figures given are for the Motorola DSP56300 DSP family, and assume the use of external, one
wait-state memory.
Availability
Motorola 1-3
DSP56300 Application Software Modules
Application/Module Part Number
CDMA Speech Codecs
IS-127 (EVRC) MSW1D103AAF
IS-96A (8Kbps QCELP) MSW1D101AAF
IS-733 (13Kbps QCELP) Consult Factory
GSM Speech Codecs
Half Rate (HR) VSELP, 5.6Kbps MSW1D201AAF
Full Rate (FR) RPE-LTP, 13Kpbs MSW1D201AAF
Enhanced Full Rate (EFR) ACELP, 12.2Kbps MSW1D202AAF
Adaptive Multi-Rate (AMR) Consult Factory
ITU Standard Speech Codecs
G.711, 48, 56, and 64Kbps MSW1D001AAF
G.722, 48, 56, and 64Kbps MSW1D002AAF
G.723.1, 5.3 and 6.4Kbps MSW1D004AAF
G.726, 16, 24, 32, and 40Kbps MSW1D007AAF
G.728, 16Kbps MSW1D003AAF
G.729 with annex A and B MSW1D006AAF
Other Speech Processing
Acoustic Echo Cancellation MSW1A003AAF
General Telecommunication
Multi-channel Dual Tone Multi-Frequency (DTMF) Transmit and Receive MSW1A002AAF
Modem and Wireline
Group 3 FAX Modem Pumps (V.17, V.21, V.27ter, V.29) MSW1B002AAF
V.32/V.32bis Data Modem Pump MSW1B003AAF
G.165/G.168 Hybrid Echo Cancellation (HEC) MSW1A001AAF
For further information, visit our Web site at http://www.sasl.com, send us email at sales@sasl.com, or contact
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How to reach us:
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Internet:
http://www.motorola-dsp.com/
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