MOTOROLA Semiconductor Software Product Brief RefleXion: Motorola DSP56300 DSP56300REFLEXP/D (Motorola Order Number) Rev. 0, 09/99 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. 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. 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. (c) Motorola, Inc., 1999 RefleXion: Motorola DSP56300 Algorithm 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. Program memory (Words) Data Memory (Words) Processing Load (MIPS) 3.6 k 7.7 k < 35 Narrowband 8kHz sampled - - - Narrowband 16kHz sampled 3.6 k 6.5 k < 26 Acoustic Echo Canceller Wideband 16kHz sampled * The benchmark figures given are for the Motorola DSP56300 DSP family, and assume the use of external, one wait-state memory. Availability The code is available now, under license, for a one-time payment and/or royalties, depending on the commercial application. Also available are: 1-2 * Application note * Demonstration system * Support consultancy for code porting and system integration RefleXion: Motorola DSP56300 Motorola Availability 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 For further information, visit our Web site at http://www.sasl.com, send us email at sales@sasl.com, or contact your nearest Signals + Software Office at: 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 Motorola 1-3 Signals + Software, Ltd. 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