Bandwidth Extension of Narrowband Speech for Low Bit-Rate Wideband Coding

TL;DR

This paper introduces a low bit-rate algorithm to extend narrowband speech to wideband, improving quality by predicting and extrapolating spectral components with minimal side information.

Contribution

It presents a novel method for bandwidth extension of speech from narrowband to wideband using only 500 bits/s of side information, combining spectral prediction and excitation extrapolation.

Findings

Enhanced speech quality over narrowband with minimal side info

Effective bandwidth extension with low bit-rate

Acceptable artifacts in reconstructed wideband speech

Abstract

Wireless telephone speech is usually limited to the 300-3400 Hz band, which reduces its quality. There is thus a growing demand for wideband speech systems that transmit from 50 Hz to 8000 Hz. This paper presents an algorithm to generate wideband speech from narrowband speech using as low as 500 bits/s of side information. The 50-300 Hz band is predicted from the narrowband signal. A source-excitation model is used for the 3400-8000 Hz band, where the excitation is extrapolated at the receiver, and the spectral envelope is transmitted. Though some artifacts are present, the resulting wideband speech has enhanced quality compared to narrowband speech.