Narrowband perceptual audio coding: enhancements for speech
Hossein Najaf-Zadeh, P. Kabal · 2001
This paper presents a bi-modal coding paradigm to com-press narrowband audio signals at 8 kbit/s. In the general mode, the Enhanced Narrowband Audio Coder (ENPAC) exploits the characteristics of the human hearing system to adaptively code the perceptually important spectral components of the input audio. The other mode is em-ployed to handle audio inputs with a strong harmonic structure. In that mode, the input block is represented by its audible harmonics. The spectral magnitude is mod-eled by the linear prediction analysis in the time domain. The phase of each harmonic is predicted and the phase residues are quantized using an adaptive bit allocation algorithm. This paper introduces a perceptually-based upper bound for phase errors of spectral components. The ENPAC encoder delivers good quality for narrow-band speech and non-speech inputs. 1