Digital processing of speech signals

Foundations of modern auditory theory

An encoding device (200) includes an MDCT unit (202) that transforms an input signal in a time domain into a frequency spectrum including a lower frequency spectrum, a BWE encoding unit (204) that generates extension data which specifies a higher frequency spectrum at a higher frequency than the lower frequency spectrum, and an encoded data stream generating unit (205) that encodes to output the lower frequency spectrum obtained by the MDCT unit (202) and the extension data obtained by the BWE encoding unit (204). The BWE encoding unit (204) generates as the extension data (i) a first parameter which specifies a lower subband which is to be copied as the higher frequency spectrum from among a plurality of the lower subbands which form the lower frequency spectrum obtained by the MDCT unit (202) and (ii) a second parameter which specifies a gain of the lower subband after being copied.

Encoding device and decoding device

A system, computer-readable medium and generated signal are disclosed for extending the bandwidth of a first signal (i.e., a narrowband signal) such as a speech signal. The system produces a second signal from a first signal by computing first area coefficients from a first signal, generating second area coefficients from the first area coefficients and generating a second signal using the second area coefficients. The first signal may be a narrowband signal and second signal may be a wideband signal. The first area coefficients may be narrowband coefficients and the second area coefficients may be wideband area coefficients.

System for bandwidth extension of narrow-band speech

Efficient and Scalable Parametric Stereo Coding for Low Bitrate Applications

This paper contributes to narrowband speech enhancement by means of frequency bandwidth extension A new algorithm is proposed for generating synthetic frequency components in the high-band (ie, 4-8 kHz) given the low-band ones (ie, 0-4 kHz) for wide-band speech synthesis It is based on linear prediction (LPC) analysis-synthesis It consists of a spectral envelope extension using efficiently line spectral frequencies (LSF) and a bandwidth extension of the LPC analysis residual using a spectral folding The low-band LSF of the synthesis signal are obtained from the input speech signal and the high-band LSF are estimated from the low-band ones using statistical models This estimation is achieved by means of four models that are distinguished by means of the first two reflection coefficients obtained from the input signal linear prediction analysis

Speech enhancement via frequency bandwidth extension using line spectral frequencies

In this paper, an encoding technique called Hi-BIN (High Band Injection), which can be combined with any narrowband coder to achieve good quality wideband speech, is described. The principle behind this technique is to model frequencies above 4 kHz by noise with an appropriate spectral shape. This simple way of injecting synthetic noise in the higher frequencies gives surprisingly good quality when compared to very widely used computationally intensive waveform coding techniques such as CELP. We show that Hi-BIN offers a low bit-rate representation of the higher band and is backwards compatible with existing narrowband speech coding systems.

Hi-BIN: an alternative approach to wideband speech coding

This paper presents a new time-domain algorithm for compressing speech signals. Using a novel tool which we will refer to as time weighted average (TWA), a periodically extendable pitch cycle is extracted from the voiced regions in the speech signal. This procedure is carried out every x/sup th/ pitch period. The discarded x-1 pitch periods are recovered using pitch synchronous interpolation (PSI). The computational complexity of the resulting decoder is surprisingly modest and shows reasonable potential of implementation on hardware as primitive as the Intel 8088 /spl mu/-processor. Simulation results show that the reconstruction quality is comparable to G.721.

R.J. Sluijter

Papers

Speech enhancement via frequency bandwidth extension using line spectral frequencies

Hi-BIN: an alternative approach to wideband speech coding

Speech compression using pitch synchronous interpolation

State of the art and trends in speech coding