Encoder, decoder, encoding method and decoding method for frequency domain long-term prediction of tonal signals for audio coding

An apparatus, comprising:

• a decoder comprising instructions executed by a processor and configured to reconstruct a current frame of an audio signal, wherein audio content of the reconstructed current frame is playable by one or more loudspeakers;
• wherein the audio signal includes one or more previous frames that precede the current frame, each of the current previous frames comprising one or more harmonic components a plurality of spectral coefficients in a frequency domain or a transform domain,
• wherein the decoder is configured to:
• receive an encoded representation of the current frame,
• determine an estimation of two harmonic parameters for each harmonic component of a most previous frame, wherein the estimation is based on a first group of three or more reconstructed spectral coefficients for each of the one or more previous frames;
• reconstruct the current frame based on the encoded representation and the estimated harmonic parameters;
• receive the encoded representation of the current frame, which includes a gain factor and a residual signal;
• and
• reconstruct the current frame based on the gain factor, the residual signal, and a fundamental frequency of the harmonic components in the current and previous frames.

An apparatus for frame loss concealment in an audio signal, wherein the audio signal comprises a current frame and one or more previous frames preceding the current frame

• each frame including one or more harmonic components and a plurality of spectral coefficients in either a frequency domain or in a transform domain;
• wherein the apparatus comprises instructions executed by a processor and is configured to:
• determine an estimation of two harmonic parameters of a most recent previous frame, wherein the estimation is based on a first group of three or more reconstructed spectral coefficients from the one or more previous frames;
• receive an encoding of the current frame, the encoding comprising a gain factor and a residual signal, wherein the gain factor and residual signal are dependent on a fundamental frequency of the harmonic components in the current and previous frames and on the two harmonic parameters of each harmonic component of the most recent previous frame;
• reconstruct the current frame based on the estimated harmonic parameters when the current frame is not received or is received in a corrupted state;
• and
• enable playback of the reconstructed audio content of the current frame through one or more loudspeakers.

A method for encoding a current frame of an audio signal based on one or more previous frames, wherein the current frame can be decoded to reconstruct audio content for playback by one or more loudspeakers, the method comprising:

• receiving an audio signal comprising a current frame and one or more previous frame, wherein each frame includes one or more harmonic components and a plurality of spectral coefficients in a frequency domain or in a transform domain,
• determining an estimation of two harmonic parameters for each of the one or more harmonic components of a most previous frame of the one or more previous frames,
• wherein determining the estimation of the two harmonic parameters for each harmonic component of a most previous frame, wherein the estimation is based a first group of three or more of the plurality of spectral coefficients from the one or more previous frames;
• determining a gain factor and a residual signal as part of the encoding of the current frame, wherein the gain factor and residual signal are based on a fundamental frequency of the harmonic components in the current and previous frames and on the estimated harmonic parameters of the most recent previous frame;
• and
• generating the encoding of the current frame, wherein the encoding comprises the gain factor and the residual signal for use in decoding.

A method for reconstructing a current frame of an audio signal for playback by one or more loudspeakers, the method comprising:

• receiving an encoded representation of the current frame, wherein the audio signal comprises the current frame and one or more previous frames, each frame including one or more harmonic components and a plurality of spectral coefficients in a frequency domain or a transform domain,
• determining an estimation of two harmonic parameters for each harmonic component of a most recent previous, wherein the estimation is based on a first group of three or more reconstructed spectral coefficients from the one or more previous frames;
• reconstructing the current frame based on the encoded representation and the estimated harmonic parameters of the most recent previous frame;
• receiving an encoded representation of the current frame comprising a gain factor and a residual signal;
• and
• reconstructing the current frame based on the gain factor, the residual signal, and a fundamental frequency of the harmonic components in the current and previous frames.

A method for frame loss concealment in an audio signal, the method comprising:

• receiving an audio signal comprising a current frame and one or more previous frames, each frame including one or more harmonic components and a plurality of spectral coefficients in a frequency domain or in a transform domain,
• determining an estimation of two harmonic parameters for each harmonic component of a most recent previous frame, wherein the estimation is based on a first group of three or more reconstructed spectral coefficients from the one or more previous frames;
• reconstructing the current frame based on the estimated harmonic parameters when the current frame is not received or is in a corrupted state;
• receiving an encoded representation of the current frame comprising a gain factor and a residual signal;
• and
• reconstructing the current frame based on the gain factor, the residual signal, and a fundamental frequency of the harmonic components in the current and previous frames, thereby enabling playback of the reconstructed audio content through one or more loudspeakers.

A non-transitory digital storage medium storing a computer program that, when executed by a computer, performs a method for encoding a current frame of an audio signal, the method comprising:

• receiving an audio signal comprising a current frame and one or more previous frames, wherein each frame includes one or more harmonic components and a plurality of spectral coefficients in a frequency domain or in a transform domain;
• determining an estimation of two harmonic parameters for each harmonic component of a most recent previous frame, wherein the estimation is based on a first group of three or more spectral coefficients from the one or more previous frames;
• determining a gain factor and a residual signal for encoding the current frame, wherein the gain factor and residual signal are based on a fundamental frequency of the harmonic components in the current and previous frames and on the estimated harmonic parameters of the most recent previous frame;
• and
• generating an encoded representation of the current frame, wherein the encoding includes the gain factor and the residual signal for subsequent decoding and playback by one or more loudspeakers.

A non-transitory digital storage medium a computer program that, when executed by a computer, performs a method for reconstructing a current frame of an audio signal, the method comprising:

• receiving an encoded representation of a current frame of the audio signal wherein the audio signal comprises the current frame and one or more previous frames, each frame including one or more harmonic components and a plurality of spectral coefficients in a frequency domain or a transform domain,
• determining an estimation of two harmonic parameters for each harmonic component of a most recent previous frame, wherein the estimation is based on a first group of three or more of reconstructed spectral coefficients from the one or more previous frames;
• reconstructing the current frame based on the encoded representation and the estimated harmonic parameters of the most recent previous frame;
• determining a gain factor and a residual signal as part of the encoding of the current frame, wherein the gain factor and residual signal are based on a fundamental frequency of the harmonic components in the current and previous frames and on the estimated harmonic parameters of the most recent previous frame;
• and
• generating an encoded representation of the current frame, wherein the encoding includes the gain factor and the residual signal for subsequent decoding and playback by one or more loudspeakers.

A non-transitory digital storage medium storing a computer program that, when executed by a computer, performs a method for frame loss concealment in an audio signal, the method comprising:

• receiving an audio signal comprising a
• current frame and one or more previous frames, wherein the one or more previous frames precede the current frame, and wherein each frame includes one or more harmonic components a plurality of spectral coefficients in a frequency domain or in a transform domain;
• determining an estimation of two harmonic parameters for each harmonic component of a most recent previous frame, wherein the estimation is based on a first group of three or more reconstructed spectral coefficients from the one or more previous frames;
• determining a gain factor and a residual signal as part of the encoding of the current frame, wherein the gain factor and residual signal are based on a fundamental frequency of the harmonic components in the current and previous frames and on the estimated harmonic parameters of the most recent previous frame;
• generating an encoded representation of the current frame, wherein the encoding includes the gain factor and the residual signal;
• if the current frame is not received or is received in a corrupted state, reconstructing the current frame based on the estimated harmonic parameters of the most recent previous frame;
• enabling playback of the reconstructed audio content through one or more loudspeaker.