High frequency regeneration of an audio signal with synthetic sinusoid addition

An audio decoder for decoding an encoded audio bitstream, the audio decoder comprising:

• a demultiplexer for extracting a frequency domain representation of a lowband audio signal having frequency content below a predetermined frequency, envelope data, and additional information from the encoded audio bitstream;
• a core decoder for receiving the frequency domain representation of the lowband audio signal and decoding the frequency domain representation of the lowband audio signal to produce a time domain lowband audio signal;
• an envelope decoder for receiving the envelope data and decoding the envelope data to produce an estimated spectral envelope;
• an analysis filterbank for filtering the time domain lowband audio signal to produce a subband domain representation of the lowband audio signal;
• a high frequency reconstructor for regenerating a subband domain representation of a highband audio signal from the subband domain representation of the lowband audio signal;
• a manipulator for adding a spectral line that is a sinusoidal component specified by the additional information to the subband domain representation of the highband audio signal;
• an envelope adjuster for adjusting a spectral envelope of the subband domain representation of the highband audio signal based, at least in part, on the estimated spectral envelope;
• and
• a synthesis filterbank for combining the subband domain representation of the lowband audio signal and the subband domain representation of the highband audio signal to produce a wideband time domain audio signal, the produced wideband time domain audio signal is output as an analog wideband signal;
• wherein the high frequency reconstructor includes a transposer for transposing several consecutive analysis filter bank channels below the predetermined frequency to certain consecutive synthesis filter bank channels above the predetermined frequency,
• wherein the analysis filterbank and the synthesis filterbank are complex quadrature mirror filter (QMF) banks,
• wherein the predetermined frequency includes a variable cross-over frequency,
• wherein the core decoder operates at half the sampling rate of the high frequency reconstructor,
• wherein the additional information includes a location of the spectral line,
• wherein the location represents a filterbank channel,
• wherein the spectral line is added to a middle of a scalefactor band associated with the location, and
• wherein one or more of the demultiplexer, the core decoder, the envelope decoder, the analysis filterbank, the high frequency reconstructor, the manipulator, the envelope adjuster, and the synthesis filterbank are implemented, at least in part, by one or more hardware elements of the audio decoder.