Quality Improvement Using a Sinusoidal Model in HE-AAC

This paper identifies a phenomenon that a signal is distorted because noise floor is generated when restoring a tone in HE-AAC, which does not exist in the original input signal; and to solve this matter, it suggests how to restore only the original tonal components in decoding by adding a sinusoidal model to the HE-AAC encoder. In this process, the sinusoidal model is used to analyze a tone and to move it to the place where noise floor is reduced. The lower the bit-rate is, the lower the frequency where the restoration by SBR(Spectral Band Replication) is started becomes, and in the lower frequency, the distortion phenomenon by noise inflow can be sensed easily; thus, the effect of improvement in the suggested method is greater, and it is beneficial that no additional information or operation in the decoding process is needed.