System and method for long term prediction in audio codecs

A method for encoding an audio signal, comprising:

• generating a frequency transformation for the audio signal, the frequency transform representing a windowed time signal in a frequency domain;
• estimating long-term predictor coefficients based on an analysis of the frequency transformation and a criteria of optimality in the frequency domain;
• filtering the audio signal in the time domain using a long-term linear predictor, wherein the long-term linear predictor is an adaptive filter with coefficients that are the long-term predictor coefficients that were estimated from the analysis in the frequency domain;
• quantizing frequency transform coefficients of a windowed frame to be encoded to generate quantized frequency transform coefficients;
• and
• constructing an encoded signal containing the quantized frequency transform coefficients, wherein the encoded signal is a representation of the audio signal.

A method for encoding an audio signal, comprising:

• filtering the audio signal using a long-term linear predictor, wherein the long-term linear predictor is an adaptive filter;
• generating a frequency transformation for the audio signal, the frequency transform representing a windowed time signal in a frequency domain;
• estimating an optimal long-term linear predictor based on an analysis of the frequency transformation and a criteria of optimality in the frequency domain;
• extending a 1-tap long-term linear predictor into a k-th order long-term linear using a predictor filter shapes table containing pre-determined filter shapes;
• selecting an optimal filter shape from the predictor filter shapes table that minimizes an energy of an output of the k-th order long-term linear predictor for use in the optimal long-term linear predictor;
• quantizing frequency transform coefficients of a windowed frame to be encoded to generate quantized frequency transform coefficients;
• and
• constructing an encoded signal containing the quantized frequency transform coefficients, wherein the encoded signal is a representation of the audio signal.