Disclosed are systems, methods, and non-transitory computer-readable media for a segmented ECF that includes multiple filter components to replicate an echo pulse response. The different filter components are used to replicate different portions of the echo pulse response. Each filter components can include filter coefficients of different sizes based on the portions of the echo pulse response that is replicated by the filter component. For example, a filter component that replicates a portion of the echo pulse response that includes a large reflection can include large filter coefficients suitable to replicate the larger reflection. In contrast, a filter component that replicates a portion of the echo pulse response that includes smaller reflections can include smaller filter coefficients that are suitable to replicate the smaller reflection. The output of each of the filter components is combined to replicate the full echo pulse response.

In an example embodiment, a full duplex transceiver includes an analog-to-digital converter (ADC), at least one processor, a first digital-to-analog converter (DAC) and an amplifier. The ADC is configured to convert an analog first signal to a digital first signal, the analog first signal being based on a transmitted signal from the transceiver and a received signal from a far-end transceiver. The at least one processor is configured to determine pre-distortion compensation coefficients using the digital first signal and a first input signal and generate a pre-distorted compensated input signal based on the pre-distortion compensation coefficients. The first DAC is configured to convert the pre-distortion compensated input signal to an analog input signal. The amplifier is configured to amplify the analog input signal to a subsequent transmit signal.

Systems and techniques relating to channel degradation detection for communication systems are described. A described system includes a processor and an interface to transmit signals and receive signals via a channel that includes a cable. The processor can be configured to perform echo cancellation based on echo tap values to remove portions of the transmitted signals that appear as echoes within the received signals, signal equalization based on equalizer tap values, or both. The processor can be configured to determine a channel quality indicator of the channel based on one or more of the echo tap values, one or more of the equalizer tap values, or both. The processor can be configured to generate a warning indication based on the channel quality indicator indicating a degradation of the cable or the channel.

A controller for an echo suppressor configured to suppress a residual echo of a far-end signal included in a primary error signal, the controller adapted for operation with a primary adaptive filter configured to form a primary echo estimate of the far-end signal included in a microphone signal and an echo canceller configured to cancel that primary echo estimate from the microphone signal so as to form the primary error signal, the controller comprising: a secondary adaptive filter configured to form a secondary echo estimate of the far-end signal comprised in the microphone signal; and control logic operable in at least two modes selected in dependence on a convergence state of the primary adaptive filter, the control logic being configured to control activation of the echo suppressor in dependence one or more transient or steady state decision parameters.

Disclosed is an echo canceller (10) including: a false echo calculator (32) that acquires current and previous filter-coefficient groups used by an adaptive filtering unit (20), and that calculates plural false echo signals by performing a filtering operation using each of the current and previous filter-coefficient groups on a sequence of reception signals (x(n)); a voice-transmission signal buffer that outputs a previous voice-transmission signal (y(n1)); an evaluation value calculator (34) that calculates plural evaluated values of an echo cancellation quantity by using the previous voice-transmission signal; a filter selector (36) that selects a new filter-coefficient group on the basis of the plural evaluated values of the echo cancellation quantity; a foreground filter (39) that performs a filtering operation using the new filter-coefficient group on the sequence of reception signals (x(n)) to generate an estimated echo component; and a subtractor (25) that subtracts the estimated echo component from a voice-transmission signal to generate a residual signal (e(n)).

Methods and systems detect residual echo in an audio signal in a non-causal manner. A non-causal residual echo detector allows accurate detection of any residual echo from an AEC (acoustic echo canceller). The non-causally detected residual echo may be utilized to perform various actions such as selecting between different causal AECs, tuning a causal AEC, and/or characterizing the performance of the causal AEC. Aspects leverage an understanding that the information about residual echo being present in a signal does not have to be causal in the sense that it is acceptable and even advantageous to know some time afterwards (e.g., after a signal has undergone acoustic echo cancellation and is output for further processing or transmission) that a residual echo was present in the signal. Such an approach is different from the case of an AEC, which needs to know right away, with a fairly low signal delay involved, whether residual echo is present.

Techniques of performing acoustic echo cancellation involve providing a bi-magnitude filtering operation that performs a first filtering operation when a magnitude of an incoming audio signal to be output from a loudspeaker is less than a specified threshold and a second filtering operation when the magnitude of the incoming audio signal is greater than the threshold. The first filtering operation may take the form of a convolution between the incoming audio signal and a first impulse response function. The second filtering operation may take the form of a convolution between a nonlinear function of the incoming audio signal and a second impulse response function. For such a convolution, the bi-magnitude filtering operation involves providing, as the incoming audio signal, samples of the incoming audio signal over a specified window of time. The first and second impulse response functions may be determined from an input signal input into a microphone.

A system for estimating delay between a far-end signal and an echo of the far-end signal in a microphone signal, the system comprising: a buffer configured to store a time-series of far-end samples representing the far-end signal; a first delay estimator configured to form a first estimate of the delay in respect of a speech frame representing speech in the microphone signal; a second delay estimator configured to form a second estimate of the delay for the speech frame by operating a first set of one or more filters on far-end samples selected from the buffer in dependence on an operating delay; a second set of one or more filters for operation on far-end samples; and a controller configured to, in response to a determination that the first estimate of the delay for the speech frame differs from the operating delay for a previous frame by at least a predefined length of time, cause the one or more filters of the second set to operate on far-end samples selected from the buffer according to the first estimate of the delay and, if in respect of one or more speech frames a measure of convergence of the second set of filters exceeds a measure of convergence of the first set of filters by at least a first predefined threshold, update the operating delay using the first estimate of the delay.

Systems and techniques relating to channel degradation detection for communication systems are described. A described system includes a processor and an interface to transmit signals and receive signals via a channel that includes a cable. The processor can be configured to perform echo cancellation based on echo tap values to remove portions of the transmitted signals that appear as echoes within the received signals, signal equalization based on equalizer tap values, or both. The processor can be configured to determine a channel quality indicator of the channel based on one or more of the echo tap values, one or more of the equalizer tap values, or both. The processor can be configured to generate a warning indication based on the channel quality indicator indicating a degradation of the cable or the channel.

A method which includes receiving a first modulated signal from a first user device, the first modulated signal being generated based upon a time-frequency transformation of first user data. The method further includes receiving a second modulated signal from a second user device, the second modulated signal being generated based upon a time-frequency transformation of second user data. The first modulated signal and the second modulated signal are then processed.