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

A decoder circuit for decoding an encoded line spectral frequencies (LSF) representation ({circumflex over (f)}) of linear prediction coefficients (a) that partially represent an audio signal, said decoder circuit including:

• a low-frequency decoder circuit configured to reconstruct coefficients of a low-frequency part of the LSF representation corresponding to a low-frequency part of the audio signal, from indices representing the coefficients of the low-frequency part;
• a high-frequency decoder circuit configured to reconstruct coefficients of a high-frequency part of the LSF representation based on a decoded frequency grid and based on flipping the decoded coefficients for the low-frequency part around a decoded mirroring frequency that separates the low-frequency part from the high-frequency part.

A method, in a digital circuit, of digitally encoding a line spectral frequencies (LSF) representation of linear prediction coefficients that partially represent an audio signal, said method comprising:

• encoding a low-frequency part of the LSF representation by quantizing coefficients of the LSF representation corresponding to a low-frequency part of the audio signal;
• encoding a high-frequency part of the LSF representation by flipping the quantized coefficients around a quantized mirroring frequency that separates the low-frequency part from the high-frequency part and selecting an optimal frequency grid based on the flipped coefficients.

An encoder circuit for digitally encoding a line spectral frequencies (LSF) representation of linear prediction coefficients that partially represent an audio signal, said encoder circuit including:

• a low-frequency encoder circuit configured to encode a low-frequency part of the LSF representation by quantizing coefficients of the LSF representation corresponding to a low-frequency part of the audio signal;
• a high-frequency decoder circuit configured to encode a high-frequency part of the LSF representation by flipping the quantized coefficients around a quantized mirroring frequency that separates the low-frequency part from the high-frequency part and selecting an optimal frequency grid based on the flipped coefficients.