Methods, Apparatus and Systems for Determining Reconstructed Audio Signal

An audio decoder generating a reconstructed audio signal having a baseband portion and a highband portion, the audio decoder comprising:

• a deformatter for extracting a first part and a second part from an encoded audio signal;
• an extractor for obtaining, from the first part, temporal envelope information, wherein the temporal envelope information includes coefficients representing a reconstruction filter;
• an extractor for obtaining, from the first part, spectral components of the baseband portion, wherein the spectral components of the baseband portion do not include spectral components of the highband portion and the number of the spectral components of the baseband portion may vary dynamically;
• a decoder for obtaining a decoded baseband audio signal from the first part, wherein the decoder includes a reconstruction filter for processing at least some of the spectral components of the baseband portion using the temporal envelope information to shape a temporal envelope of the baseband portion;
• an extractor for obtaining, from the second part, a noise parameter and an estimated spectral envelope of the highband portion;
• a filter for obtaining a plurality of subband signals from the decoded baseband audio signal;
• a generator for creating a high-frequency reconstructed signal by copying in a circular manner a number of consecutive subband signals of the plurality of subband signals;
• an envelope adjuster for obtaining an envelope adjusted high-frequency signal by adjusting, based on the estimated spectral envelope of the highband portion, a spectral envelope of the high-frequency reconstructed signal, wherein a frequency resolution of the estimated spectral envelope is adaptive and wherein the obtaining the envelope adjusted high-frequency signal includes determining and applying a gain;
• a noise generator for generating a noise component based on the noise parameter, wherein the noise parameter indicates a level of noise contained in the highband portion;
• a combiner for obtaining a combined high-frequency signal by adding the noise component to the envelope adjusted high-frequency signal;
• and
• a synthesizer for obtaining a time-domain reconstructed audio signal by combining the decoded baseband audio signal and the combined high-frequency signal;
• wherein the audio decoder comprises one or more hardware elements.