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参数资料
| 型号： | SW300031 |
| 厂商： | Microchip Technology |
| 文件页数： | 1/2页 |
| 文件大小： | 0K |
| 描述： | RTOS CMX-RTX PREEMPTIVE |
| 标准包装： | 1 |
| 类型： | RTOS |
| 适用于相关产品： | dsPIC30F |
dsPIC30F Acoustic Echo Cancellation Library
Summary
The dsPIC30F Acoustic Echo Cancellation (AEC) Library provides a
function to eliminate echo generated in the acoustic path between a
speaker and a microphone. This function is useful for speech and
Far End
Speech
User Application
Receive Path
Far End
Speech
telephony applications in which a speaker and a microphone are located
in close proximity to each other, and therefore susceptible to signals
propagating from the speaker to the microphone resulting in a perceptible
and distracting echo effect at the far end. It is especially suitable for these
Acoustic Echo
Cancellation
applications:
? Hands-free Cell Phone Kits
? Speakerphones
? Intercoms
? Teleconferencing Systems
For hands-free phones intended to be used in compact environments,
Near End
Speech
Adaptive
Filter
-
∑ +
Send Path
Near End
Speech
Echo
such as a car cabin, this library is fully compliant with the G.167 standard
for Acoustic Echo Cancellation.
Description
The Acoustic Echo Cancellation Library is written entirely in assembly
language and is highly optimized to make extensive use of the dsPIC30F
DSP instruction set and advanced addressing modes. The algorithm
FAR END
Features
Key features of the AEC Library include:
NEAR END
avoids data overflow. The AEC Library provides an
“ AcousticEchoCancellerInit ” function for initializing the various data
structures required by the algorithm and an “ AcousticEchoCanceller ”
function to remove the echo component from a 10 ms block of sampled
16-bit speech data. The user can easily call both functions through a
well-documented Application Programmer's Interface (API).
The “ AcousticEchoCanceller ” function is primarily a Time Domain
algorithm. The received far end speech samples (typically received across
a communication channel such as a telephone line) are filtered using an
adaptive Finite Impulse Response (FIR) filter. The coefficients of this filter
are adapted using the Normalized Least Mean Square (NLMS) algorithm,
such that the filter closely models the acoustic path between the near end
speaker and the near end microphone (i.e., the path traversed by the
echo). Voice Activity Detection (VAD) and Double Talk Detection (DTD)
algorithms are used to avoid updating the filter coefficients when there is
no far end speech and also when there is simultaneous speech from both
ends of the communication link (double talk). As a consequence, the
algorithm functions correctly even in the presence of full-duplex
communication. A Non-Linear Processor (NLP) algorithm is used to
eliminate residual echo.
The dsPIC30F Acoustic Echo Canceller Library uses an 8 kHz sampling
rate. However, the library includes a sample rate conversion function that
ensures interoperability with libraries designed for higher sampling rates
(9.6 kHz, 11.025 kHz or 12 kHz). The conversion function allows incoming
signals at higher sampling rates to be converted to a representative 8 kHz
sample. Similarly, the conversion function allows the output signal to be
converted upward from 8 kHz to match the user application.
Resource Requirements
Acoustic Echo Cancellation
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All functions can be called from either a C or assembly application
program
Five user functions:
– AcousticEchoCancellerInit
– AcousticEchoCanceller
– InitRateConverter
– SRC_upConvert
– SRC_downConvert
Full compliance with the Microchip dsPIC30F C30 Compiler,
Assembler and Linker
Simple user interface – just one library file and one header file
Highly optimized assembly code, utilizing DSP instructions and
advanced addressing modes
Echo cancellation for 16, 32 or 64 ms echo delays or ‘tail lengths’
(configurable)
Fully tested for compliance with G.167 specifications for
in-car applications
Audio Bandwidth: 0-4 kHz at 8 kHz sampling rate
Convergence Rate: Up to 43 dB/sec., typically > 30 dB/sec.
Echo Cancellation: Up to 50 dB, typically > 40 dB
Can be used together with the Noise Suppression (NS) Library,
since the same processing block size (10 ms) is used
dsPIC30F Acoustic Echo Cancellation Library User’s Guide is
provided to help the user understand and use the library
Demo application source code is provided with the library
Accessory Kit available for purchase includes: an audio cable,
headset, oscillators, microphone, speaker, DB9 M/F RS-232
cable, DB9M-DB9M Null Modem Adapter and can be used for
Echo Tail
MIPS
Program Flash
RAM
library evaluation
Length (ms)
64 16.5
32 10.5
16 7.5
Sample Rate Conversion
Computational Requirements: 1 MIPS
Program Flash Memory: 2.6 KB
RAM: 0.5 KB
Memory (KB)
6
6
6
(KB)
5.7
3.4
2.6
Note:
The user application might require an additional 2 KB-2.5 KB of
RAM for data buffering (application-dependent).
Microchip Technolog y Incor porated
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相关代理商/技术参数 |
参数描述 |
|---|---|
| SW300032 | 功能描述:开发软件 RTOS for dsPIC30 RoHS:否 制造商:Atollic Inc. 产品:Compilers/Debuggers 用于:ARM7, ARM9, Cortex-A, Cortex-M, Cortex-R Processors |
| SW300040-100K | 功能描述:开发软件 Noise Supp Lib RoHS:否 制造商:Atollic Inc. 产品:Compilers/Debuggers 用于:ARM7, ARM9, Cortex-A, Cortex-M, Cortex-R Processors |
| SW300040-25K | 功能描述:开发软件 Noise Supp Lib RoHS:否 制造商:Atollic Inc. 产品:Compilers/Debuggers 用于:ARM7, ARM9, Cortex-A, Cortex-M, Cortex-R Processors |
| SW300040-5K | 功能描述:开发软件 Noise Supp Lib RoHS:否 制造商:Atollic Inc. 产品:Compilers/Debuggers 用于:ARM7, ARM9, Cortex-A, Cortex-M, Cortex-R Processors |
| SW300040-EVAL | 功能描述:开发软件 Noise Supp Lib Eval Copy RoHS:否 制造商:Atollic Inc. 产品:Compilers/Debuggers 用于:ARM7, ARM9, Cortex-A, Cortex-M, Cortex-R Processors |
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