| 摘要 |
The invention provides an adaptive echo canceller and method for detecting double talk (DT) and echo path change (EPC) conditions and for distinguishing therebetween. DT and EPC conditions are detected by comparing a generated echo return loss enhancement (ERLE) signal with a selected ERLE threshold level. Similarly, the energy level of the echo canceller incoming signal is compared with a second threshold level. If the level of the ERLE signal is below its threshold and the level of the incoming signal is above the second threshold, a DT or EPC condition is deemed to exist and a predetermined signal is generated. Responsive to this signal, an orthogonality monitor recognizes the predetermined signal as representing either a DT or EPC condition. The determination is obtained by comparing the absolute value of cross-correlation between the output signal to be transmitted from the echo canceller and the echo estimate signal generated by the adaptive filter of the echo canceller to the product of a predetermined EPC threshold level and an average amplitude estimate of the product of the output signal to be transmitted from the echo canceller and the echo estimate signal generated by the adaptive filter of the echo canceller.
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