A method of generating a residual signal performed by an encoder includes identifying an input signal including an audio sample, generating a first residual signal from the input signal using linear predictive coding (LPC), generating a second residual signal having a less information amount than the first residual signal by transforming the first residual signal, transforming the second residual signal into a frequency domain, and generating a third residual signal having a less information amount than the second residual signal from the transformed second residual signal using frequency-domain prediction (FDP) coding.

A method, executed by a processor for compressing an audio signal in multiple layers, may comprise: (a) restoring, in a highest layer, an input audio signal as a first signal; (b) restoring, in at least one intermediate layer, a signal obtained by subtracting an upsampled signal, which is obtained by upsampling the audio signal restored in the highest layer or an immediately previous intermediate layer, from the input audio signal as a second signal; and (c) restoring, in a lowest layer, a signal obtained by subtracting an upsampled signal, which is obtained by upsampling the audio signal restored in an intermediate layer immediately before the lowest layer, from the input audio signal as a third signal, wherein the first signal, the second signal, and the third signal are combined to output a final restoration audio signal.

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 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 apparatus for generating a score signal representing the quality of an audio or video signal supplied to the apparatus is proposed. The apparatus comprises: an input for supplying an audio or video signal, a computing unit implementing a neural network, the computing unit being supplied with the audio or video signal, and producing a score signal representing the quality of an audio or video signal supplied representing at least one predefined quality parameter of the audio or video signal, the neural network being set up by being trained with training data of a specific transmission standard and/or codec used for generating the audio or video data.

An apparatus for generating a score signal representing the quality of an audio or video signal supplied to the apparatus is proposed. The apparatus comprises: an input for supplying an audio or video signal, a computing unit implementing a neural network, the computing unit being supplied with the audio or video signal, and producing a score signal representing the quality of an audio or video signal supplied representing at least one predefined quality parameter of the audio or video signal, the neural network being set up by being trained with training data of a specific transmission standard and/or codec used for generating the audio or video data.

Apparatus for decoding an encoded audio signal including an encoded core signal and parametric data, including: a core decoder for decoding the encoded core signal to obtain a decoded core signal; an analyzer for analyzing the decoded core signal before or after performing a frequency regeneration operation to provide an analysis result; and a frequency regenerator for regenerating spectral portions not included in the decoded core signal using a spectral portion of the decoded core signal, the parametric data, and the analysis result.

In methods and apparatus and non-transitory memory units for encoding/decoding audio signal information, the encoder side may determine if a signal frame is useful for long term post filtering and/or packet lost concealment and may encode information in accordance to the results of the determination, and the decoder side may apply the LTPF and/or PLC in accordance to the information obtained from the encoder.

Methods, systems, and apparatus, including computer programs encoded on computer storage media, for performing audio coding are described. One example of the methods includes receiving an audio signal that includes one or more subband signals. A residual signal of at least one of the one or more subband signals is generated based on the at least one of the one or more subband signals. It is determined that the at least one of the one or more subband signals is a high pitch signal. In response to determining that the at least one of the one or more subband signals is a high pitch signal, weighting is performed on the residual signal of the at least one of the one or more subband signal to generate a weighted residual 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.