Abstract:
An audio signal is received that might include keyboard noise and speech. The audio signal is digitized and transformed from a time domain to a frequency domain. The transformed audio is analyzed to determine whether there is likelihood that keystroke noise is present. If it is determined there is high likelihood that the audio signal contains keystroke noise, a determination is made as to whether a keyboard event occurred around the time of the likely keystroke noise. If it is determined that a keyboard event occurred around the time of the likely keystroke noise, a determination is made as to whether speech is present in the audio signal around the time of the likely keystroke noise. If no speech is present, the keystroke noise is suppressed in the audio signal. If speech is detected in the audio signal or if the keystroke noise abates, the suppression gain is removed from the audio signal.
Abstract:
Suppressing one or more frequency ranges of a signal prevents the occurrence of feedback in a voice data communications application. A system recognizes a frequency range in a signal where feedback occurs, or anticipates a frequency range where feedback is anticipated. The signal includes a signal the input system generates or that the output system renders. The system suppresses the signal in the frequency range by disregarding one or more sampling bits representing the frequency range, or by applying one or more filters to attenuate or eliminate the signal in the frequency range. The system may monitor the signal to identify feedback resulting in different or additional frequency ranges and suppress the signal in the different or additional frequency ranges to prevent feedback from occurring.
Abstract:
A method is provided for reducing the adverse impact of echo on audio quality in a two-communication system. The method includes two parts. The first part begins by detecting non-linear effects (e.g. clippings and audio glitches). If a non-linear effect is detected, the system temporarily disables adaptation of the adaptive filter. In this way, filter coefficients obtained before the non-linear effect happens will not be corrupted, so the AEC can quickly recover from the non-linear effects. The second part begins by monitoring a parameter reflecting signal quality (e.g., ERLE). If the signal quality parameter falls below a given value the system switches from a full-duplex mode of operation to a half-duplex mode of operation. In this way, when a non-linear effect that is undetectable or occurs repeatedly (e.g., speaker volume changes) and which can corrupt an acoustic echo canceller (AEC) for a relatively long period of time, the system switches from full-duplex operation to half-duplex operation. In half-duplex operation, communication can only happen in one direction at a time, and thus the echo path is broken, effectively eliminating echoes. When the non-linear effect is no longer present and the quality parameter rises to a normal level, communication returns to a full-duplex mode of operation and the AEC once again removes the echoes.
Abstract:
Center clipping is applied with acoustic echo suppression in a two-way voice communication system to reduce a microphone signal to the background noise floor when speech is not present. For integration with a microphone array, the center clipping processing determines whether speech is present based on estimates of the overall leak through and instantaneous microphone power across the microphone array channels. The overall estimates can be calculated as a dot product of the microphone array coefficients computed by a sound source localization process and separate estimates for the respective microphone channel.
Abstract:
The quality and robustness of audio echo cancellation is enhanced by selectively applying glitch recovery processes based on a quality measurement of the relative offset between capture and render audio streams. For example, large and small glitch detection is enabled for low relative offset variance; large glitch detection is enabled in a medium range of relative offset variance; and neither enabled at high variance. Further, a fast glitch recovery process suspends updating the adaptive filter coefficients of the audio echo cancellation while buffers are re-aligned to recover from the glitch, so as to avoid resetting the adaptive filter. When clock drift exists between capture and render audio streams, a multi-step compensation method is applied to improve AEC output quality in case the drifting rate is low; and a resampler is used to compensate the drift in case the drifting rate is high. An anti-clipping process detects clipping of the signals, and also suspends adaptive filter updating during clipping.
Abstract:
A method and a system for authenticating an entity based on a symmetric encryption algorithm are provided. The method includes the following steps: 1) an entity A sends an authentication request message to an entity B; 2) after receiving the authentication request message, the entity B sends an authentication response message to the entity A; 3) the entity A determines the validity of the entity B according to the received authentication response message. The implementation cost of the system can be reduced by using the authentication according to the invention.