Abstract: A method of echo cancellation, particularly for use in high definition applications, splits an input signal and reference signal into M single-sided sub-band. The subbanded signals are downsampled at a downsampling rate N, where N?M, adaptively filtered, and recombined to produce an output signal. The sub-bands are preferably oversampled such that N<M. The use of oversampling and single-sided sub-banding reduces complexity and avoids aliasing problems.

Abstract: A method of echo cancellation, particularly for use in high definition applications, splits an input signal and reference signal into M single-sided sub-band. The subbanded signals are downsampled at a downsampling rate N, where N?M, adaptively filtered, and recombined to produce an output signal. The sub-bands are preferably oversampled such that N<M. The use of oversampling and single-sided sub-banding reduces complexity and avoids aliasing problems.

Abstract: In a closed loop acoustic system with forward and return paths, gain is controlled with different instantiations of a common gain control engine on each path. The gain control engine computes a first gain based on near-end signal levels, computes a second gain based on the output of the gain control engine, computes a third gain based on a howling condition, and computes a final gain as the product of the first, second and third gains.

Abstract: Disclosed is a method of reducing clicking sounds in an audio data stream. The samples of the audio data are delayed by a predetermined amount in a sliding window containing a predetermined number of samples. The presence of a clicking sound in the delayed data within said sliding window is detected and the corresponding audio data replaced by substitute data derived from the audio data stream.

Abstract: A method of recovering timing information in a packet network, involves detecting quiet periods in the packet network when network packet delay variation (PDV) is low. A frequency prediction unit is trained during the quiet periods to learn output clock variations of a timing recovery unit to permit the frequency prediction unit to predict frequency update values for a local oscillator during non quiet periods taking into account the historical output clock variations during quiet periods. The output of the frequency prediction unit is used as the active frequency update values during non quiet periods.

Abstract: A method of reducing noise in an environment where the noise source is in a fixed location relative to a pair of microphones, such as in a camera with a zoom motor, involves receiving signals x1(t), x2(t) from the respective microphones, and filtering each of the signals x1(t), x2(t) with respective first and second linear filters having filter coefficients obtained by computing eigenfilters corresponding to data samples from the respective microphones for noise only and signal only conditions.

Abstract: A multi-mode differential termination circuit has a pair of differential input terminals for receiving external differential signals, a pair of series-connected load elements coupled between said differential input terminals, and an analog interface terminal coupled a common junction point of said load elements. A bias circuit is coupled to the common junction point of the load elements for selectively applying a bias voltage thereto in response to a digital control signal. A control input receives the digital control signal to activate the bias circuit.

Abstract: An automatic gain control unit controls the gain applied to an input signal produced by a microphone subject to ambient noise. The automatic gain control circuit continually monitors the signal level of said input signal. A first gain control circuit decreases the gain applied to the input signal in increments of a first size when the input signal exceeds a first predetermined level. A second gain control circuit increases the gain applied to said input signal in increments of a smaller size when the input signal falls below a second predetermined level and in response to the presence of a speech present signal. The second predetermined level is less than said first predetermined level. In one embodiment, the first gain control circuit controls the analog gain of a codec and the second gain control circuit controls the digital gain of the codec.

Abstract: A digital FM transmitter has a digital controlled oscillator for generating a modulated RF carrier. A digital signal processor receives digital input samples and generates a modulating signal for input to the digital controlled oscillator. A bandpass filter for filters frequency components of the modulated carrier outside a predetermined frequency band and supplies the filtered modulated RF carrier to an antenna.

Abstract: Timing information is transmitted over a network by sending time-stamped packets between a transmitter and receiver. The time-stamped packets are used to compute an estimate of the frequency deviation between the transmitter clock and the receiver clock. The local receiver clock is periodically updated to match the transmitter clock based on the estimate, which is preferably a least squares estimate. A multiple window approach is employed to increase update speed.