Abstract: A device (2) for changing the pitch of an audio signal (r), such as a speech signal, comprises a sinusoidal analysis unit (21) for determining sinusoidal parameters of the audio signal (r), a parameter production unit (22) for predicting the phase of a sinusoidal component, and a sinusoidal synthesis unit (23) for synthesizing the parameters to produce a reconstructed signal (r?). The parameter production unit (22) receives, for each time segment of the audio signal, the phase of the previous time segment to predict the phase of the current time segment.

Abstract: Coding of an audio signal represented by a respective set of sampled signal values for each of a plurality of sequential segments is disclosed. The sampled signal values are analyzed (40) to determine one or more sinusoidal components for each of the plurality of sequential segments. The sinusoidal components are linked (42) across a plurality of sequential segments to provide sinusoidal tracks. For each sinusoidal track, a phase comprising a generally monotonically changing value is determined and an encoded audio stream including sinusoidal codes (r) representing said phase is generated (46).

Abstract: Wideband extension of telephone speech for higher perceptual quality. A method for extending the frequency range of a speech signal using wideband extension method with an inverse filter and a synthesis filter where both filters receive LPC coefficients from an LPC estimator. The wideband LPC coefficients are obtained from wideband LSFs. The wideband LSFs are obtained by appending highband LSFs, created by applying a matrix to narrowband LSFs, and lowband LSFs, created by dividing the narrowband LSFs by two. The matrix used to create the highband LSFs is selected from a predetermined list of matrices. The selection is based on either wideband or narrowband reflection coefficients extracted from the narrowband speech signal.

Abstract: Described is a transmission system (10) comprising a transmitter (12) for transmitting a narrowband audio signal to a receiver (14) via a transmission channel (16). The receiver (14) comprises a frequency domain bandwidth extender (18) for extending a bandwidth of the received narrowband audio signal by complementing the received narrowband audio signal with a highband extension thereof. The bandwidth extender (18) comprises an amplitude extender (24) for extending the bandwidth of an amplitude spectrum of the received narrowband audio signal by mapping narrowband amplitudes onto highband amplitudes. The bandwidth extender (18) further comprises a phase extender (26) for extending the bandwidth of a phase spectrum of the received narrowband signal and a combiner (28) for combining the extended amplitude spectrum and the extended phase spectrum into a bandwidth extended audio signal.

Abstract: An analyzer determines frequency and amplitudes of an audio signal represented by sinusoids for transmission transmitted to a receiver decoder which includes a synthesizer to reconstruct the audio signal. A pitch detector determines the pitch for transmission to the receiver along with the structure of the spectrum of the speech signal. The structure of the spectrum is often transmitted in the form of LPC parameters. To correct for frequency changes of the periodic component of an audio signal, a frequency change determiner determines a change of the frequency of the periodical component over the analysis period. This change of frequency is transmitted to the decoder for increasing the accuracy of the reconstruction of the audio signal. Further, the frequency change is only used to obtain a more accurate value of the pitch. The frequency change is determined by using a time warper which performs a time transformation such that a time transformed audio signal is obtained with a minimum frequency change.

Abstract: Described is a transmission system (10) comprising a transmitter (12) for transmitting a narrowband audio signal to a receiver (14) via a transmission channel (16). The receiver (14) comprises a frequency domain bandwidth extender (18) for extending a bandwidth of the received narrowband audio signal by complementing the received narrowband audio signal with a highband extension thereof. The bandwidth extender (18) comprises an amplitude extender (24) for extending the bandwidth of an amplitude spectrum of the received narrowband audio signal by mapping narrowband amplitudes onto highband amplitudes. The bandwidth extender (18) further comprises a phase extender (26) for extending the bandwidth of a phase spectrum of the received narrowband signal and a combiner (28) for combining the extended amplitude spectrum and the extended phase spectrum into a bandwidth extended audio signal.

Abstract: Described is a transmission system (20) comprising a transmitter (22) for transmitting a narrowband speech signal, e.g. bandwidth limited between 300 and 3400 Hz, to a receiver (24) via a transmission channel (26). The transmission system (20) is characterized in that the transmitter (22) or the receiver (24) comprise amplifying means (28,30,32,34,36,38) for enhancing a listener's perception of low-frequency speech signal components by amplifying a frequency band of the narrowband speech signal. The frequency band may contain frequencies in the range of 300-450 Hz. The amplifying means (28,30,32,34,36,38) may comprise a band pass filter (28,34) for deriving the frequency band from the narrowband speech signal and an amplifier (30,36) for amplifying the frequency band. The amplification of the frequency band gives a reinforced perception of frequency components below the narrowband speech signal (e.g. 50-300 Hz), compensating for the lack of the physical presence of these components.

Abstract: In an audio transmission system, an input signal is split up into two spectral portions in a transmitter. These spectral portions are coded by their own respective coder. The low-frequency signal portion is coded by a regular narrow-band coder and the high frequency portion is coded using a coder that outputs LPC codes and signal amplitude codes. In the receiver, the low frequency signal portion is reconstructed by a narrow-band decoder and the high frequency portion is reconstructed by applying a high pass filter to a white noise signal and applying an LPC filter that is controlled by the LPC codes to this filtered white noise signal and adjusting the signal amplitude with an amplifier that is controlled using the amplitude codes of the transmitter. The reconstructed low frequency signal and the reconstructed high frequency signal are then combined to yield a reconstructed output signal containing both frequency ranges.

Abstract: A narrow-band audio signal (9) contains information, present as recognisable distortions, for processing the signal into a wide-band signal.

Abstract: Wideband extension of telephone speech for higher perceptual quality. A method for extending the frequency range of a speech signal using wideband extension method with an inverse filter and a synthesis filter where both filters receive LPC coefficients from an LPC estimator. The wideband LPC coefficients are obtained from wideband LSFs. The wideband LSFs are obtained by appending highband LSFs, created by applying a matrix to narrowband LSFs, and lowband LSFs, created by dividing the narrowband LSFs by two. The matrix used to create the highband LSFs is selected from a predetermined list of matrices. The selection is based on either wideband or narrowband reflection coefficients extracted from the narrowband speech signal.