An audio decoder for providing at least four bandwidth-extended channel signals on the basis of an encoded representation provides first and second downmix signals on the basis of a jointly encoded representation of the first and second downmix signals using a multi-channel decoding and provides at least first and second audio channel signals on the basis of the first downmix signal using a multi-channel decoding, and provides at least third and fourth audio channel signals on the basis of the second downmix signal using a multi-channel decoding. It performs a multi-channel bandwidth extension on the basis of the first and third audio channel signals, to obtain first and third bandwidth-extended channel signals, and performs a multi-channel bandwidth extension on the basis of the second and fourth audio channel signals, to obtain second and fourth bandwidth extended channel signals. An audio encoder uses a related concept.

An audio decoder for providing at least four bandwidth-extended channel signals on the basis of an encoded representation provides first and second downmix signals on the basis of a jointly encoded representation of the first and second downmix signals using a multi-channel decoding and provides at least first and second audio channel signals on the basis of the first downmix signal using a multi-channel decoding, and provides at least third and fourth audio channel signals on the basis of the second downmix signal using a multi-channel decoding. It performs a multi-channel bandwidth extension on the basis of the first and third audio channel signals, to obtain first and third bandwidth-extended channel signals, and performs a multi-channel bandwidth extension on the basis of the second and fourth audio channel signals, to obtain second and fourth bandwidth extended channel signals. An audio encoder uses a related concept.

Disclosed herein is a method of constructing and utilizing a sound engineering evaluation and comparison process to allow for improved finished results. Such a method entails the utilization of a high-pass filter for listening evaluation of recorded music or sounds including consistency with low-frequency mixing to allow for a tool to implement changes in relation to the filtered results in order to accommodate sensitivities of the human ear (with the optional inclusion of a comparison method to provide possible further enhanced results and the avoidance of biases). In such a manner, a facilitating method for sound engineering mixing adjustments that provide such accommodations are provided for improved sound recordings for distribution within on-line or recording product frameworks.

Disclosed herein is a method of constructing and utilizing a sound engineering evaluation and comparison process to allow for improved finished results. Such a method entails the utilization of a high-pass filter for listening evaluation of recorded music or sounds including consistency with low-frequency mixing to allow for a tool to implement changes in relation to the filtered results in order to accommodate sensitivities of the human ear (with the optional inclusion of a comparison method to provide possible further enhanced results and the avoidance of biases). In such a manner, a facilitating method for sound engineering mixing adjustments that provide such accommodations are provided for improved sound recordings for distribution within on-line or recording product frameworks.

An adaptive dynamic audio hum extractor eliminates line frequency hum components and associated higher harmonics from an audio signal. An audio signal containing line frequency hum can be processed by providing dynamically controlled notch filters at the fundamental line frequency and additional harmonic multiples of the fundamental frequency. The audio signal is detected to provide dynamic control of the depth of the notch filters. Alternatively, an audio signal containing hum can be processed by dividing the spectrum into at least two frequency bands, an unaltered high band combined with a dynamically processed low band. The adaptive dynamically controlled notch filters vary the depth of the notches in relation to the envelope or time averaged level of the bandwidth limited audio signal. This allows masking of the hum components with higher levels of audio, thereby providing transparency devoid of audio path notches.

An adaptive dynamic audio hum extractor eliminates line frequency hum components and associated higher harmonics from an audio signal. An audio signal containing line frequency hum can be processed by providing dynamically controlled notch filters at the fundamental line frequency and additional harmonic multiples of the fundamental frequency. The audio signal is detected to provide dynamic control of the depth of the notch filters. Alternatively, an audio signal containing hum can be processed by dividing the spectrum into at least two frequency bands, an unaltered high band combined with a dynamically processed low band. The adaptive dynamically controlled notch filters vary the depth of the notches in relation to the envelope or time averaged level of the bandwidth limited audio signal. This allows masking of the hum components with higher levels of audio, thereby providing transparency devoid of audio path notches.

Disclosed is an audio coding method, including: obtaining a current frame of an audio signal, which includes a high frequency band signal and a low frequency band signal; obtaining a first encoding parameter based on the high frequency band signal and the low frequency band signal; obtaining a second encoding parameter based on the high frequency band signal, where the second encoding parameter includes tone component information of the high frequency band signal; obtaining a third encoding parameter based on the high frequency band signal, where the third encoding parameter includes sub-band envelope information of a part of a sub-band of the high frequency band signal that needs to be encoded; and performing bitstream multiplexing on the first encoding parameter, the second encoding parameter, and the third encoding parameter, to obtain an encoded bitstream.

An audio decoding method includes obtaining an encoded bitstream; performing bitstream demultiplexing on the encoded bitstream, to obtain a high frequency band parameter of a current frame of an audio signal, wherein the high frequency band parameter indicates a location, a quantity, and an amplitude or energy of a tone component comprised in a high frequency band signal of the current frame; obtaining a reconstructed high frequency band signal of the current frame based on the high frequency band parameter; and obtaining an audio output signal of the current frame based on the reconstructed high frequency band signal of the current frame.

A method for decoding an encoded audio bitstream is disclosed. The method includes receiving the encoded audio bitstream and decoding the audio data to generate a decoded lowband audio signal. The method further includes extracting high frequency reconstruction metadata and filtering the decoded lowband audio signal with an analysis filterbank to generate a filtered lowband audio signal. The method also includes extracting a flag indicating whether either spectral translation or harmonic transposition is to be performed on the audio data and regenerating a highband portion of the audio signal using the filtered lowband audio signal and the high frequency reconstruction metadata in accordance with the flag.

The application relates to HFR (High Frequency Reconstruction/Regeneration) of audio signals. In particular, the application relates to a method and system for performing HFR of audio signals having large variations in energy level across the low frequency range which is used to reconstruct the high frequencies of the audio signal. A system configured to generate a plurality of high frequency subband signals covering a high frequency interval from a plurality of low frequency subband signals is described. The system comprises means for receiving the plurality of low frequency subband signals; means for receiving a set of target energies, each target energy covering a different target interval within the high frequency interval and being indicative of the desired energy of one or more high frequency subband signals lying within the target interval; means for generating the plurality of high frequency subband signals from the plurality of low frequency subband signals and from a plurality of spectral gain coefficients associated with the plurality of low frequency subband signals, respectively; and means for adjusting the energy of the plurality of high frequency subband signals using the set of target energies.