Methods, systems, and apparatus, including computer programs encoded on computer storage media, for performing residual quantization are described. One example of the methods includes performing a first residual quantization on a first target residual signal at a first bit rate to generate a first quantized residual signal. A second target residual signal is generated based at least on the first quantized residual signal and the first target residual signal. A second residual quantization is performed on the second target residual signal at a second bit rate to generate a second quantized residual signal, where the first bit rate is different from the second bit rate.

A computer-implemented method, a computer program product, and a computer system for system monitoring. A computer system convert a time domain representation of first sound into a frequency domain representation, maps monitoring datasets of a monitored system to frequencies in the frequency domain representation, modifies the amplitudes of the respective frequencies according mapping rules defined by a user, convert the frequency domain representation into the time domain representation and generate a sound wave in a digital format which has modified amplitudes, converts the sound wave in the digital format to a sound wave in an analog format, and feeds the sound wave in the analog format to a sound system to play second sound. Performance of the monitored system is monitored by the user listening to the second sound and comparing the first and second sound.

A computer-implemented method, a computer program product, and a computer system for system monitoring. A computer system convert a time domain representation of first sound into a frequency domain representation, maps monitoring datasets of a monitored system to frequencies in the frequency domain representation, modifies the amplitudes of the respective frequencies according mapping rules defined by a user, convert the frequency domain representation into the time domain representation and generate a sound wave in a digital format which has modified amplitudes, converts the sound wave in the digital format to a sound wave in an analog format, and feeds the sound wave in the analog format to a sound system to play second sound. Performance of the monitored system is monitored by the user listening to the second sound and comparing the first and second sound.

An audio processor for generating a frequency enhanced audio signal from a source audio signal has: an envelope determiner for determining a temporal envelope of at least a portion of the source audio signal; an analyzer for analyzing the temporal envelope to determine temporal values of certain features of the temporal envelope; a signal synthesizer for generating a synthesis signal, the generating having placing pulses in relation to the determined temporal values, wherein the pulses are weighted using weights derived from amplitudes of the temporal envelope related to the temporal values, where the pulses are placed; and a combiner for combining at least a band of the synthesis signal that is not included in the source audio signal and the source audio signal to obtain the frequency enhanced audio signal.

An audio processor for generating a frequency enhanced audio signal from a source audio signal has: an envelope determiner for determining a temporal envelope of at least a portion of the source audio signal; an analyzer for analyzing the temporal envelope to determine temporal values of certain features of the temporal envelope; a signal synthesizer for generating a synthesis signal, the generating having placing pulses in relation to the determined temporal values, wherein the pulses are weighted using weights derived from amplitudes of the temporal envelope related to the temporal values, where the pulses are placed; and a combiner for combining at least a band of the synthesis signal that is not included in the source audio signal and the source audio signal to obtain the frequency enhanced audio signal.

Methods, systems, and apparatus, including computer programs encoded on computer storage media, for performing long-term prediction (LTP) are described. One example of the methods includes determining a pitch gain and a pitch lag of an input audio signal for at least a predetermined number of frames. It is determined that the pitch gain of the input audio signal has exceeded a predetermined threshold and that a change of the pitch lag of the input audio signal has been within a predetermined range for at least the predetermined number of frames. In response to determining that the pitch gain of the input audio signal has exceeded the predetermined threshold and that the change of the third pitch lag has been within the predetermined range for at least the predetermined number of frames, a pitch gain is set for a current frame of the input audio signal.

A device for signal processing includes a memory and a processor. The memory is configured to store a parameter associated with a bandwidth-extended audio stream. The processor is configured to select a plurality of non-linear processing functions based at least in part on a value of the parameter. The processor is also configured to generate a high-band excitation signal based on the plurality of non-linear processing functions.

An encoder for encoding an audio signal has: an analyzer configured for deriving prediction coefficients and a residual signal from an unvoiced frame of the audio signal; a gain parameter calculator configured for calculating a first gain parameter information for defining a first excitation signal related to a deterministic codebook and for calculating a second gain parameter information for defining a second excitation signal related to a noise-like signal for the unvoiced frame; and a bitstream former configured for forming an output signal based on an information related to a voiced signal frame, the first gain parameter information and the second gain parameter information.

An encoder for encoding an audio signal has: an analyzer configured for deriving prediction coefficients and a residual signal from an unvoiced frame of the audio signal; a gain parameter calculator configured for calculating a first gain parameter information for defining a first excitation signal related to a deterministic codebook and for calculating a second gain parameter information for defining a second excitation signal related to a noise-like signal for the unvoiced frame; and a bitstream former configured for forming an output signal based on an information related to a voiced signal frame, the first gain parameter information and the second gain parameter information.

An apparatus for playing back an audio object associated with a position includes a distance calculator for calculating distances of the position to speakers or for reading the distances of the position to the speakers. The distance calculator is configured to take a solution with a smallest distance. The apparatus is configured to play back the audio object using the speaker corresponding to the solution.