Patent ID: 8019076
Filing Date: 2011-09-13
Classification: H04M

Abstract:
1. In a full-duplex teleconferencing product, an audio subsystem implementing false doubletalk detection and recovery, comprising: a full-duplex data port operable to transmit to and receive from a far-side participant audio data; a microphone input adapted to receive audio data from a microphone; a speaker output adapted to provide audio data received from said data port to a sound producing device; a far-side frequency decomposer operable to decompose the far-side audio data received from said data port; a microphone frequency decomposer operable to decompose the audio data received at said microphone input into a number of frequency bands; an echo canceller receiving audio data originating at said microphone input and said data port, said echo canceller including echo cancellation coefficients, wherein said echo canceller is operable to convolve said echo cancellation coefficients with the data received at said data port to generate an echo cancellation signal, further wherein said echo canceller applies the echo cancellation signal to the data received at said microphone input to produce an echo cancelled signal; and echo cancellation coefficients converger operable to converge said echo cancellation coefficients to a solution corresponding to the accumulation of the echo paths in the physical environment between the sound producers producing sound from said speaker output and the sound receivers for which said microphone input is receiving, said converger being further controllable such that at certain times adaptation of said echo cancellation coefficients proceeds and at other times adaptation is prevented; a doubletalk detector a controlling whether said echo cancellation coefficients converger is proceeding, said doubletalk detector determining doubletalk by a comparison between audio signal levels originating at said data port and said microphone input and audio levels of the echo cancelled signal; a false doubletalk discriminator implementing a secondary method of doubletalk detection, said discriminator comparing audio signal levels in different frequency bands than said doubletalk detector, said discriminator determining whether a condition of false doubletalk is present by comparing the times doubletalk is detected by said doubletalk detector and the times that doubletalk is detected through the secondary method of doubletalk detection, wherein said discriminator determines false doubletalk if the times doubletalk is detected by said doubletalk detector and the times detected through the secondary method of doubletalk detection are significantly different; wherein said audio subsystem detects false doubletalk when said false doubletalk discriminator determines that the times doubletalk is detected through said doubletalk detector is significantly different than the times doubletalk is detected through the secondary method of doubletalk detection.