Motorola Corporation

Mansour Tahernezhaadi

Michael J Kirk

Lee Michael Proctor

J Douglas Brophy

A method and apparatus for effecting multi-party teleconferencing that avoids the need for tandem vocoding of packet based information from conference call participants. In particular, the teleconferencing bridge infrastructure utilizes packet tagging of encoded packets with a tag as well as adaptive scheduling of bandwidth to transmit packet based information to the end user call participants. Decoding is accomplished at each end user based on information included within the tag such that an appropriate decoding algorithm is selected for the packet-based audio information thereby avoiding tandem vocoding.

Apparatus and method for implementing a packet based teleconference bridge

The invention provides an apparatus and method for bulk delay insertion prior to echo cancellation, with echo suppression. The exemplary apparatus embodiment () bandpass filters () and down samples (), by a down sampling factor, a reference signal and a combined signal that includes an echo of the reference signal. An adaptive echo delay filter () determines a plurality of filter coefficients, using the down sampled reference signal, and using an error signal formed as a difference between the down sampled combined signal and the adaptive echo delay filter output. When the filter coefficients have converged, an echo delay time period is determined as a product of the tap location of the maximum filter coefficient and the down sampling factor. When the echo delay time period is greater than the capacity of an associated echo canceller, an adaptive delay inserter () inserts the echo delay time period prior to echo cancellation. Following insertion of the delay, echo suppression () is implemented while the echo canceller retrains with the new, inserted delay.

Delay insertion for echo cancellation, with echo supression, in a communication network

A method for providing echo cancellation between a first and second communication unit detects an echo condition () between first and second communication units. In addition, the method includes detecting whether a decoded near end audio packet contains a suitable level of background noise to be used as a background noise packet. If so, the current near end encoded audio packet is stored () in a buffer (), such as a circular buffer. Previous near end encoded audio packets () that are also determined to have a suitable level of background noise based on their decoded corresponding counterparts are also stored in the circular buffer. When an echo condition is detected with respect to a current near end encoded audio packet, the method includes substituting a previous near end encoded audio packet stored in the buffer as the next encoded audio packet for transmission ().

Method and apparatus for providing echo cancellation

A method and apparatus that performs specific automatic gain control in an echo canceller (). The disclosed method and apparatus utilize a low complexity algorithm that performs automatic gain control to achieve greater speed of convergence of the echo canceller () and an increased ability to distinguish between near-end speech and echo through the use of specific automatic gain control. A double talk threshold of the echo canceller is adjusted by using, in part, computed gains of inbound and outbound signals internally within the echo canceller in order to adjust the echo canceller double talk threshold.

Method and apparatus for echo canceller automatic gain control

A method and apparatus is capable of detecting the presence of a non-linear echo path as well as transitions from non-linear echo path to linear echo path and vice versa. Additionally, when non-linear echo path is detected, the echo canceller ( ) is configured to follow a prescribed logic routine that combats possible echo leak-through as a result of compromised cancellation due to non-linearity. This prescribed logic routine affords the echo canceller ( ) protection against non-linear echo path by preserving an already converged state of the echo canceller ( ) from possible divergence due to the occurrence of non-linearity in the echo path and thereby prevents echo leak-through that would occur due to divergence of the echo canceller ( ).

Protecting an echo canceller against random transitions in echo paths

An apparatus ( ) checks voice quality when in a vocoder bypass mode. If the voice quality level is beyond an acceptable range, the apparatus ( ) ends the vocoder bypass mode and returns to tandem vocoding. For example, a vocoder bypass controller ( ) includes a speech quality detector ( ) that determines the speech quality level of speech information based on at least one of detected volume level, echo level and noise level of the speech information. The vocoder bypass controller ( ) with the speech quality detector ( ) outputs a speech quality-based vocoder bypass control signal ( ) to selectively activate or deactivate a vocoder bypass operation in response to the speech quality-based vocoder bypass control signal ( ). In another embodiment, a network element for communicating speech packets includes an incoming decoder ( ) and a speech quality detector ( ) operative to determine the speech quality level of incoming speech packets. The speech quality detector ( ) determines whether to activate speech quality enhancement operations in response to a determined speech quality level of incoming speech packets.

Method and apparatus for providing speech quality based packet enhancement in packet switched networks

A system and method for detecting and controlling severe echo. The system includes an echo canceller having an adaptive filter responsive to a set of coefficients, a first memory storing a software program operative to evaluate these coefficients to determine the severity of echo existing in the system, and a second memory accessible by the echo canceller and the first memory which stores the coefficients. Upon evaluating the coefficients, the system and method enables the proper mode of echo cancellation in the echo canceller.

Method and system for detecting and controlling severe echo

A system and method for controlling echo using zero echo path, ringing, and off-hook detection. When conditions for zero echo path are detected, the present embodiment bypasses echo cancellation by replacing the output signal with the input to the echo canceller. In addition, the present embodiment also provides ringing and off-hook detection which additionally evaluate when the output signal should be replaced by the input to the echo canceller. The system and method provides additional detection and control benefits to echo cancellers and can be implemented in echo cancellation systems without substantial change to the existing echo canceller.

Method and system for controlling echo cancellation using zero echo path, ringing, and off-hook detection

In a communication system ( ), a first echo return loss through communication system ( ) associated with a first call connection between a caller ( ) and a first caller ( ) is estimated. A second echo return loss associated with a second call connection between caller ( ) and a second caller ( ) is estimated. The call connection may be switching from the first call connection to the second call connection after estimating the first echo return loss, and from the second call connection to the first call connection after estimating the second echo return loss. Echo generated in the first call connection is cancelled based on at least the first echo return loss by an echo canceller in communication system ( ) after switching from the second call connection to the first call connection.

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Naperville, IL, United States of America

Mansour Tahernezhaadi