High-frequency tonal components restoration in low-bitrate audio coding using multiple spectral translations

At reduced bitrates, the audio compression affects high frequency tonal components of signals, which results in a roughness phenomenon. Audio coders are limited in the reconstruction of the high-frequency spectrum mainly because of the potential unpredictability of the structure of the latter, as well as unprecise indicators of tonal to noise ratio. We propose a technique for high-frequency tones restoration, based on the correction of the tonal positions in the decoded signal, using a small set of information transmitted through an auxiliary channel at a very low bit-rate (typically <; 2 kbps). The proposed approach is evaluated using objective measures of perceptual roughness. The experimental results with HE-AAC coding at 16 kbps exhibits an efficient preservation of the harmonicity and a significant improvement of the audio quality.