Apparatus and method for selecting one of a first encoding algorithm and a second encoding algorithm using harmonics reduction

Apparatus for selecting one of a first encoding algorithm having a first characteristic and a second encoding algorithm having a second characteristic for encoding a portion of an audio signal to obtain an encoded version of the portion of the audio signal, comprising:

• a long-term prediction filter configured to receive the audio signal, to reduce the amplitude of harmonics in the audio signal and to output a filtered version of the audio signal;
• a first estimator to estimate a segmental signal to noise ratio of the portion of the audio signal as a first quality measure of the portion of the audio signal, the first quality measure being associated with the first encoding algorithm, wherein the first estimator is to transform the filtered version of the audio signal with a modified discrete cosine transform, MDCT, to shape the transformed filtered version of the audio signal using a weighted linear prediction coding, LPC, filter, and to estimate a first distortion in the weighted MDCT domain using a global gain estimator;
• a second estimator to estimate a segmental signal to noise ratio of the portion of the audio signal as a second quality measure of the portion of the audio signal, the second quality measure being associated with the second encoding algorithm, wherein the second estimator is to use an approximation of an adaptive codebook distortion and an approximation of an innovative codebook distortion, wherein the adaptive codebook is approximated in the weighted signal domain using a pitch-lag estimated by a pitch analysis algorithm, wherein a second distortion is computed in the weighted signal domain assuming an optimal gain and wherein the second distortion is then reduced by a constant factor, approximating the innovative codebook distortion;
• a controller for selecting the first encoding algorithm or the second encoding algorithm based on a comparison between the first quality measure and the second quality measure,
• wherein the first encoding algorithm is a transform coding algorithm, a MDCT based coding algorithm or a transform coding excitation, TCX, coding algorithm and wherein the second encoding algorithm is a code excited linear prediction, CELP, coding algorithm or an algebraic code excited linear prediction, ACELP, coding algorithm.