Audiocodes Ltd.

Dsp Group Limited

Leon Bialik

Felix Flomen

Mark Raifel

Eli Shoval

As part of a system and method for transmitting a signaling tone over a packet switched data (or other communication) network, an audio encoder may have a speech encoding unit and a tone distorter. The tone distorter may distort one or more components of a signaling tone within an audio signal and the speech encoding unit may encode speech and the distorted signaling tone within the audio signal. A control signal may be sent to a tone generator to reproduce the distorted tone.

Method and apparatus for transmitting signaling tones over a packet switched network

A voice encoder which utilizes future data, such as the lookahead data typically available for linear predictive coding (LPC), to partially encode a future packet and to send the partial encoding as part of the current packet. A decoder utilizes the partial encoding of the previous packet to decode the current packet if the latter did not arrive properly.

Systems and methods for encoding and decoding speech for lossy transmission networks

A voice encoder and decoder which attempt to minimize the effects of voice data packet loss, typically over wide area networks is provided. The voice encoder utilizes future data, such as the lookahead data typically available for linear predictive coding (LPC), to partially encode a future packet and to send the partial encoding as part of the current packet. The decoder utilizes the partial encoding of the previous packet to decode the current packet if the latter did not arrive properly.

An improved speech processing system has a short-term analyzer, a target vector generator and a maximum likelihood, multi-pulse analyzer. The multi-pulse analyzer generates a plurality of sequences of equal amplitude, variable sign, variably spaced pulses. Each of the sequences have a different amplitude value and each of the pulses within each sequence have equal amplitudes but variable signs. The multi-pulse analyzer generates a signal corresponding to the sequence of equal amplitude, variable sign, variably spaced pulses which, according to maximum likelihood criteria, most closely represents the target vector. The maximum likelihood criteria are based on the cross-correlation of the target vector with an impulse response for the pulses in each sequence and on either a covariance matrix or an autocorrelation vector of the impulse response. In an alternative embodiment, the multi-pulse analyzer generates a plurality of sequences of variable sign trains of equal amplitude, uniformly spaced pulses and performs the analysis on the pulse trains. The pulses within each train have the same sign and each of the sequences of trains of pulses having a different amplitude value.

Speech processing system quantizer of single-gain pulse excitation in

A pitch determination device which separates at least each frame of the input speech signal into separate, lower resolution portions is provided. The pitch determination device includes a resolution lowering unit, a signal selecting unit and a pitch determination device. The resolution lowering unit has an input line on which the input speech signal is provided and K output lines, on each of which output lines, one of K lower resolution input signals is provided. The signal selecting unit has K input lines connected to the K output lines of the resolution lowering unit and has an output line on which is provided one of the K lower resolution signals which fulfill a predetermined quality criterion. The criterion is typically based on the energy content of the lower resolution signals. The pitch determination device has an input line connected to the output line of the signal selecting unit and an output line which provides a pitch value for the selected lower resolution input signal. The lower resolution signals are subsampled by K, where each ith lower resolution signal is offset from said input signal by i sample points, where i varies from 0 to K-1. The pitch determination is performed by cross-correlating or autocorrelating between two low resolution signals, that of the input signal and of a shifted and offset lower resolution signal. For cross-correlation, the shifted lower resolution signal is a previously received signal. For autocorrelation, the shifted lower resolution signal is a shifted version of the low resolution input signal.

Pitch determination using low time resolution input signals

A speech compression/decompression system and method which do not require special hardware are described. The compression unit represents an input audio signal as a collection of parameters, wherein the parameters are a remnant excitation pulse sequence, a set of spectral coefficients and a set of pitch parameters. The decompression unit utilizes the pitch parameters and remnant excitation pulse sequence to produce a reconstructed excitation signal. The decompression unit also utilizes the spectral coefficients to filter the reconstructed excitation signal into a speech waveform. The compression unit includes a short-term predictor, a two-step long-term predictor and a multi-pulse analyzer.

System and method for compression and decompression of audio signals

A speech processing system and method are disclosed. In one embodiment of the present invention, the system includes at least a maximum likelihood quantization (MLQ) multi-pulse analysis unit operating on a target vector. The MLQ multi-pulse analyses unit typically determines an initial gain level for the multi-pulse sequence and performs single gain multi-pulse analysis (MPA) a number of times, each with a different gain level. The pulse sequence which most closely represents the target vector is provided as an output signal. In another embodiment, the system includes at least a pulse train multi-pulse analysis unit wherein the target vector is modeled as a series of pulse trains. Each pulse train comprises a plurality of single gain pulses, wherein each pulse is at a position which is a pitch value distance apart from the previous pulse in the pulse train. Combinations of maximum likelihood analyses with pulse trains are also part of the present invention.

Multi-pulse analysis speech processing System and method

A filter utilizes future and past information for at least some of the subframes. Specifically, the filter receives a frame of synthesized speech and, for each subframe of the frame of synthesized speech, produces a signal which is a function of the subframe and of windows of earlier and later synthesized speech. Each window is utilized only when it provides an acceptable match to the subframe.

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Rishon LeZion, Israel

Leon Bialik