Line echo cancellation software is available for dsPIC digital signal controllers -

Line echo cancellation software is available for dsPIC digital signal controllers


Chandler, Ariz. &#151 There’s a new software library available for Microchip Technology’s 16-bit dsPIC Digital Signal Controllers (DSCs). The G.168-standard compliant Line Echo Cancellation Library (SW300080-EVAL) offers telecom designers improved integration possibilities and the ability to reduce costs.

The dsPIC DSC's DSP instructions are used extensively in this library. Yet, despite the complex functionality of these libraries, the user interface is simple – just one library file and one header file, according to Microchip. This library also leaves sufficient resource headroom to integrate other application requirements, including traditional microcontroller tasks, onto the dsPIC DSC to reduce cost and board space Applications that Microchip believes can benefit from these advanced libraries include hands-free cell phone kits, speaker phones, intercoms, voice over I/P solutions, teleconferencing systems, and cellular telephony applications.

“Designers today are under pressure to bring products to market quickly and at a lower cost,” said Sumit Mitra, vice president of Microchip's Digital Signal Controller Division. “Our C-friendly DSC architecture, coupled with ready-to-use application libraries, reduces development risk and time to market. The low, one-time license cost of our libraries enables a lower overall solution cost.”

The G.168 Line Echo Cancellation Library is easily callable via a well-documented Application Programmer's Interface (API). Two user functions are associated with this library; one is for initialization and the second function removes the echo component from a 5-, 10-, or 20-millisecond block of sampled 16-bit speech data.

This library is configurable for 16-, 32- or 64-millisecond maximum echo delays (echo tail-lengths). Double-talk detection can be invoked to avoid updating filter coefficients when there is simultaneous speech from both ends of the communication link. As a result, the algorithm functions correctly in the presence of full-duplex communication. Also, an optional non-linear processor can be used to eliminate residual echo, which is typically caused by non-linearity in the echo path.

“The evaluation/development license is downloadable from the Internet for just $5USD. A full license is required only when product shipment begins. We have made it as easy and low risk for our customers as possible,” Mitra said. Line echo cancellation is primarily a time-domain algorithm. The received near-end speech samples are filtered using an adaptive Finite Impulse Response (FIR) filter. The coefficients of this filter are adapted using the Normalized Least Means Square (NLMS) algorithm, so that the filter closely matches the path between the transmitter and receiver. One such example is the path through a telephone hybrid, which is essentially the path traversed by the echo. Echo cancellation of up to 70 dB can be obtained, although echo is typically at least 40 dB.

The G.168 Line Echo Cancellation Library is compatible with Microchip's Noise Suppression and Acoustic Echo Cancellation libraries, which are designed for a similar range of applications. All licensing options for the G.168 Line Echo Cancellation Library are immediately available. Among these options is a one-year evaluation/development license, which is unaltered from the libraries that are used for production and can be purchased online at Microchip Direct.

The G.168 Line Echo Cancellation Evaluation Library license (SW300080-EVAL) is $5USD. Industry-unique, one-time-fee licensing options are also available for production, which runs counter to the per-unit royalty business model that is common for this class of library. Starting at $2,500USD for 5,000-unit products, the license fee that Microchip charges is attractive to many customers, since it is a fraction of the cost they would incur developing it and assuring compliance themselves. These one-time fees are based on the estimated lifetime volume of products derived from the design effort that uses the library.

For additional pricing or other information, contact any Microchip sales representative or authorized worldwide distributor, or visit Microchip's Web site at microchip/dspic.

Microchip Technology 1-888.MCU-MCHP


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