Scott N. Levine

A switched parametric and transform audio coder

In this paper, we present a system of sines+transients+noise modeling techniques that dynamically switches between parametric representations and transform coding based representations. The sines and noise are represented by parametric models using multiresolution sinusoidal modeling and Bark-band noise modeling, respectively. The transients are modeled by short regions of transform coding. In addition, new methods are presented for selection and quantization of sinusoidal trajectories based on trajectory length and signal-to-masking thresholds. This system is useful for both low bitrate audio coding (20-40 kbps) and compressed-domain processing, such as time-scale modification.

Multiresolution sinusoidal modeling for wideband audio with modifications

We describe a computationally efficient method of generating more accurate sinusoidal parameters {amplitude, frequency, phase} from a wideband polyphonic audio source in a multiresolution, non-aliased fashion. This significantly improves upon previous work of sinusoidal modeling that assumes a single-pitched monophonic source, such as speech or an individual musical instrument, while using approximately the same number of sinusoids. In addition to a more general analysis, we can now perform high-quality modifications such as time-stretching and pitch-shifting on polyphonic audio with ease.

Improvements to the switched parametric and transform audio coder

We introduce improvements to previous sines+transients+noise audio modeling systems, including new sinusoidal trajectory selection and quantization procedures. In a previous work by Levine and Smith (see Proc. Int. Conf. Acoustics, Speech, and Signal Processing, Phoenix, 1999), the audio is first segmented into transient and non-transient regions. The transient region is modeled using traditional transform coding techniques, while the non-transient regions are modeled using parametric sines plus noise modeling. Because such a system contains a mix of parametric and non-parametric techniques, compressed-domain processing such as time-scale modifications are possible.