Abstract: A method system and program for encoding and decoding a speech signal including error correction data. The method comprises: receiving a speech signal comprising successive frames, for each of a plurality of frames of the speech signal, analysing the speech signal to determine side information and a residual signal, encoding the residual signal at a first bit rate, and generating an output bitstream based on the residual signal encoded at the first bit rate, and for at least one of the plurality of frames of the speech signal, encoding the residual signal at a second bit rate that is lower than the first bit rate; and generating error correction data based on the residual signal encoded at the second bit rate.

Abstract: A method, system and computer program for encoding speech according to a source-filter model. The method comprises deriving a spectral envelope signal representative of a modelled filter and a first remaining signal representative of a modelled source signal, and deriving a second remaining signal from the first remaining signal by, at intervals during the encoding: exploiting a correlation between approximately periodic portions in the first remaining signal to generate a predicted version of a later portion from a stored version of an earlier portion, and using the predicted-version of the later portion to remove an effect of said periodicity from the first remaining signal. The method further comprises, once every number of intervals, transforming the stored version of the earlier portion of the first remaining signal prior to generating the predicted version of the respective later portion.

Abstract: A method, system and program for encoding and decoding speech according to a source-filter model whereby speech is modeled to comprise a source signal filtered by a time-varying filter. The method comprises: receiving a speech signal; and from the speech signal, deriving a spectral envelope signal representing the modeled filter and a remaining signal representing the modeled source. At intervals during the encoding, the method further comprises determining a period between portions of the remaining signal having a degree of repetition and determining a correlation between said portions based on that period, thus producing a respective vector of the correlation for each interval. Once every number of said intervals, the method further comprises selecting a codebook from a plurality of codebooks for quantizing the vectors, quantizing the vectors of that number of intervals according to the selected codebook, and transmitting the quantized vectors along with an indication of the selected codebook.

Abstract: A method of encoding one or more parent blocks of values, the number of values being the length of each block, the method comprising for each parent block: (a) determining a first sum of values in the parent block; (b) splitting the parent block into smaller subblocks; (c) for at least one of the subblocks, determining a second sum of the values in the subblock, selecting a likelihood table from the plurality of likelihood tables based on said first sum of values in the parent block and encoding the second sum using the likelihood table; (d) designating each subblock a parent block; (e) carrying out steps (a), (b), (c) and (d) until at least one parent block reaches a predetermined condition.

Abstract: A method of encoding speech, the method comprising: receiving a signal representative of speech to be encoded; at each of a plurality of intervals during the encoding, determining a pitch lag between portions of the signal having a degree of repetition; selecting for a set of said intervals a pitch lag vector from a pitch lag codebook of such vectors, each pitch lag vector comprising a set of offsets corresponding to the offset between the pitch lag determined for each said interval and an average pitch lag for said set of intervals, and transmitting an indication of the selected vector and said average over a transmission medium as part of the encoded signal representative of said speech.

Abstract: A method and system for regenerating wideband speech from narrowband speech. The method comprises: receiving samples of a narrowband speech signal in a first range of frequencies; modulating received samples of the narrowband speech signal with a modulation signal having a modulating frequency adapted to upshift each frequency in the first range of frequencies by an amount determined by the modulating frequency wherein the modulating frequency is selected to translate into a target band a selected frequency band within the first range of signals; filtering the modulated samples using a high pass filter to form a regenerated speech signal in the target band, wherein the lower limit of the high pass filter defines the lowermost frequency in the target band; and combining the narrow band speech signal with the regenerated speech signal in the target band to regenerate a wideband speech signal.

Abstract: A wideband speech encoder according to one embodiment includes a filter bank having a lowband processing path and a highband processing path. The processing paths have overlapping frequency responses. A first encoder is configured to encode a speech signal produced by the lowband processing path according to a first coding methodology. A second encoder is configured to encode a speech signal produced by the highband processing path according to a second coding methodology that is different than the first coding methodology.

Abstract: A method of filtering a speech signal for speech encoding in a communications network, includes determining a cut off frequency for a filter, wherein a component of the speech signal in a frequency range less than the cut off frequency is to be attenuated by the filter; receiving the speech signal at the filter; determining at least one parameter of the received speech signal, the at least one parameter providing an indication of the energy of the component of the received speech signal that is to be attenuated; and adjusting the cut off frequency in dependence on the at least one parameter, thereby adjusting the frequency range to be attenuated.

Abstract: In one embodiment, a method of generating a highband excitation signal includes generating a spectrally extended signal by extending the spectrum of a signal that is based on an encoded lowband excitation signal; and performing anti-sparseness filtering of a signal that is based on the encoded lowband excitation signal. In this method, the highband excitation signal is based on the spectrally extended signal, and the highband excitation signal is based on a result of the anti-sparseness filtering.

Abstract: A method, program and apparatus for estimating a bandwidth of a channel from a transmitter to a receiver. The method comprises: receiving a packet stream at the receiver from the transmitter; receiving from the transmitter an indication of data transmitted from the transmitter to one or more other recipients than said receiver between packets of said packet stream; and determining at the receiver, using said indication, an estimate of the bandwidth of said channel. The estimate may enable transmission of packets from the transmitter to be controlled.

Abstract: A method of encoding one or more parent blocks of values, the number of values being the length of each block, the method comprising for each parent block: (a) determining a first sum of values in the parent block; (b) splitting the parent block into smaller subblocks; (c) for at least one of the subblocks, determining a second sum of the values in the subblock, selecting a likelihood table from the plurality of likelihood tables based on said first sum of values in the parent block and encoding the second sum using the likelihood table; (d) designating each subblock a parent block; (e) carrying out steps (a), (b), (c) and (d) until at least one parent block reaches a predetermined condition.

Abstract: In one embodiment, a method of generating a highband excitation signal includes harmonically extending the spectrum of a signal that is based on a lowband excitation signal; calculating a time-domain envelope of a signal that is based on the lowband excitation signal; and modulating a noise signal according to the time-domain envelope. The method also includes combining (A) a harmonically extended signal based on a result of the harmonically extending and (B) a modulated noise signal based on a result of the modulating. In this method, the highband excitation signal is based on a result of the combining.

Abstract: In one embodiment, a highband burst suppressor includes a first burst detector configured to detect bursts in a lowband speech signal, and a second burst detector configured to detect bursts in a corresponding highband speech signal. The lowband and highband speech signals may be different (possibly overlapping) frequency regions of a wideband speech signal. The highband burst suppressor also includes an attenuation control signal calculator configured to calculate an attenuation control signal according to a difference between outputs of the first and second burst detectors. A gain control element is configured to apply the attenuation control signal to the highband speech signal. In one example, the attenuation control signal indicates an attenuation when a burst is found in the highband speech signal but is absent from a corresponding region in time of the lowband speech signal.

Abstract: A method of encoding one or more parent blocks of values, the number of values being the length of each block, the method comprising for each parent block: (a) determining a first sum of values in the parent block; 1(b) splitting the parent block into smaller subblocks; (c) for at least one of the subblocks, determining a second sum of the values in the subblock, selecting a likelihood table from the plurality of likelihood tables based on said first sum of values in the parent block and encoding the second sum using the likelihood table; (d) designating each subblock a parent block; (e) carrying out steps (a), (b), (c) and (d) until at least one parent block reaches a predetermined condition.

Abstract: A wideband speech encoder according to one embodiment includes a lowband encoder and a highband encoder. The lowband encoder is configured to encode a lowband portion of a wideband speech signal as a set of filter parameters and an encoded excitation signal. The highband encoder is configured to calculate values for coding parameters that specify a spectral envelope and a temporal envelope of a highband portion of the wideband speech signal. The temporal envelope is based on a highband excitation signal that is derived from the encoded excitation signal. In one such example, the temporal envelope is based on a difference in levels between the highband portion and a synthesized highband signal, wherein the synthesized highband signal is generated according to the highband excitation signal and a set of highband filter parameters.

Abstract: In one embodiment, a method of signal processing including includes encoding a low-frequency portion of a speech signal into at least an encoded narrowband excitation signal and a plurality of narrowband filter parameters; and generating a highband excitation signal based on a narrowband excitation signal. The encoded narrowband excitation signal includes a time warping, and the method includes applying a time shift to a high-frequency portion of the speech signal based on the information related to the time warping. The method also includes encoding the time-shifted high-frequency portion of the speech signal into at least one (A) a plurality of highband filter parameters and (B) a plurality of high band gain factors.

Abstract: A quantizer according to an embodiment is configured to quantize a smoothed value of an input value (e.g., a vector of line spectral frequencies) to produce a corresponding output value, where the smoothed value is based on a scale factor and a quantization error of a previous output value.

Abstract: A method system and program for encoding and decoding a speech signal including error correction data. The method comprises: receiving a speech signal comprising successive frames, for each of a plurality of frames of the speech signal, analysing the speech signal to determine side information and a residual signal, encoding the residual signal at a first bit rate, and generating an output bitstream based on the residual signal encoded at the first bit rate, and for at least one of the plurality of frames of the speech signal, encoding the residual signal at a second bit rate that is lower than the first bit rate; and generating error correction data based on the residual signal encoded at the second bit rate.

Abstract: A first user terminal, host terminal, method and program. The first terminal comprises: a transceiver for communicating with a plurality of other user terminals over a communication network; and communications processing apparatus, coupled to the transceiver, and arranged to participate in a call with a selected number of the other user terminals via the transceiver and communication network, the call including transmission of a voice signal from the first user terminal. The communications processing apparatus is operable in a mode whereby it temporarily discontinues transmission of the voice signal in response to detecting less than a predetermined level of activity on said voice signal, and the communications processing apparatus is further configured to selectively enable that mode in dependence on the selected number of other user terminals in the call.

Abstract: A method of regenerating wideband speech from narrowband speech, the method comprising: receiving samples of a narrowband speech signal in a first range of frequencies; modulating received samples of the narrowband speech signal with a modulation signal having a modulating frequency adapted to upshift each frequency in the first range of frequencies by an amount determined by the modulating frequency wherein the modulating frequency is selected to translate into a target band a selected frequency band within the first range of signals; filtering the modulated samples using a target band filter to form a regenerated speech signal in the target band; and combining the narrow band speech signal with the regenerated speech signal in the target band to regenerate a wideband speech signal, the method comprising the step of controlling the modulated samples to lie in a second range of frequencies identified by determining a signal characteristic of frequencies in the first range of frequencies.