Audio encoding/decoding based on an efficient representation of auto-regressive coefficients

A method of decoding an encoded parametric spectral representation ({circumflex over (f)}) of auto-regressive coefficients (a) that partially represent an audio signal, said method including the steps of:

• reconstructing elements ({circumflex over (f)}L) of a low-frequency part (fL) of the parametric spectral representation (f) corresponding to a low-frequency part of the audio signal from at least one quantization index (IfL) encoding that part of the parametric spectral representation;
• reconstructing elements ({circumflex over (f)}H) of a high-frequency part (fH) of the parametric spectral representation by weighted averaging based on the decoded elements ({circumflex over (f)}L) flipped around a decoded mirroring frequency ({circumflex over (f)}m), which separates the low-frequency part from the high-frequency part, and a decoded frequency grid (gopt).

An encoder for encoding a parametric spectral representation (f) of auto-regressive coefficients (a) that partially represent an audio signal, said encoder including:

• a low-frequency encoder configured to encode a low-frequency part (fL) of the parametric spectral representation (f) by quantizing elements of the parametric spectral representation that correspond to a low-frequency part of the audio signal;
• a high-frequency encoder configured to encode a high-frequency part (fH) of the parametric spectral representation (f) by weighted averaging based on the quantized elements ({circumflex over (f)}L) flipped around a quantized mirroring frequency ({circumflex over (f)}m), which separates the low-frequency part from the high-frequency part, and a frequency grid (gopt) determined from a frequency grid codebook in a closed-loop search procedure.

A decoder for decoding an encoded parametric spectral representation ({circumflex over (f)}) of auto-regressive coefficients (a) that partially represent an audio signal, said decoder including:

• a low-frequency decoder configured to reconstruct elements ({circumflex over (f)}L) of a low-frequency part (fL) of the parametric spectral representation (f) corresponding to a low-frequency part of the audio signal from at least one quantization index (IfL) encoding that part of the parametric spectral representation;
• a high-frequency decoder configured to reconstruct elements ({circumflex over (f)}H) of a high-frequency part (fH) of the parametric spectral representation by weighted averaging based on the decoded elements ({circumflex over (f)}L) flipped around a decoded mirroring frequency ({circumflex over (f)}m), which separates the low-frequency part from the high-frequency part, and a decoded frequency grid (gopt).