The ITU G.168 specification was developed to address and standardize the performance of echo cancellers in the PSTN. This specification strictly limits the convergence time, allowed residual echo, tolerance for varying signal levels, and allowed divergence in the presence of destabilizing narrow-band energy. It also specifies the required performance of any additional non-linear processing such as clamping and/or suppression, ability to handle data communication, and disabling signals such as the modem 'ANSam' tone. Addendums in 2000 and 2003 further restricted and quantified the requirements for compliance. The ITU G.168 Recommendation and subsequent addendums may be found at the ITU web site.
VOCAL has developed a variety of echo cancellation modules and solutions, including acoustic echo cancellers (AEC), line echo cancellers (LEC), and digital network echo cancellers (DNEC). Our echo cancellers are used in millions of installations world-wide, including the public telephone system, a variety of VoIP products, as well many other types of manufactured items. Our experts can provide a custom, optimized echo cancellation solution to meet most types of processing and acoustic environment requirements. These echo cancellers have been rigorously tested, meeting ITU compliance tests as well as our own. Please contact us for more information or to arrange a demonstration.
G.168 Echo cancellers must be placed in the 4-wire portion of a circuit (which may be an individual circuit path or a path carrying a multiplexed signal). While intended for use in the PSTN, the extremely high performance of G.168 compliant cancellers has allowed them to be used in a wide variety of other situations. For VoIP and embedded devices, the canceller may be placed after an audio codec (such as G.711, G.722, G.723.1, G.726, G.728, G.729, G.729A, G.729AB, GSM, MELP, etc.) to reduce the echo from local or customer hardware.
Like all of VOCAL's software libraries, the G.168 echo canceller is available in a variety of forms, including optimized ANSI C and assembly language optimized implementations for leading DSP architectures (including but not limited to processors from TI, ADI, AMD, ARM, MIPS, CEVA, LSI Logic ZSP, etc.). These libraries are modular and can be executed as a single task under a variety of operating systems or standalone with its own microkernel. To find out if your desired platform and processor is supported, please contact us.
As an experienced leader in this field, VOCAL has recognized shortcomings in the G.168 standard and has implemented several additional test sets to guarantee world-class performance in the harshest acoustic environments. All G.168 echo canceller modules must pass these VOCAL specific tests in addition to the standard ITU Test Suite, as well as undergo voice testing in our labs.