A Multiband Excited Waveform-Interpolated 2.35-kbps Speech Codec for Bandlimited Channels

Following a brief portrayal of the activities in 2.4-kbps speech coding, a wavelet-based pitch detector is invoked, which reduces the complexity of conventional autocorrelation-based pitch detectors, while ensuring smooth pitch trajectory evolution. This scheme is incorporated in a waveform-interpolated codec, which uses voiced–unvoiced (V/U) classification, and instead of simple Dirac pulses, an unconventional zinc basis function excitation is employed for modeling the voiced excitation. The required zinc-function parameters are determined in an analysis-by-synthesis loop, and for the sake of smooth waveform evolution and reduced complexity, a focused search strategy and a few further suboptimum restrictions are imposed without seriously affecting the speech quality. This baseline codec operates at a rate of 1.9 kbps, but it suffers from slight buzziness during the periods of excessive voicing. This impediment is then mitigated by invoking a mixed V/U multiband excitation, which slightly increases the bit rate to 2.35 kbps due to the transmission of the 3-b voicing strength code in each of the three excitation bands. Index Terms—Low-rate speech coding, multiband excitation, waveform-interpolated speech coding, wavelet-based pitch estimation

A Sixth-Rate, 3.8 kbps GSM-Like Speech Transceiver

A 1.9 kbps Zinc-function excited, wave-form interpolated speech codec is proposed and its bit error sensitivity is analysed. This codec is incorporated in a standard GSM-like system, employing either convolutional or turbo coding. Ironically, the higher complexity turbo codec provides only a modest robustness gain over the standard convolutional code due to the short interleaver constraint imposed by the highly bandwidth-efficient speech codec

Very low bit rate voice compression for mobile communications

SIGLEAvailable from British Library Document Supply Centre-DSC:DXN027101 / BLDSC - British Library Document Supply CentreGBUnited Kingdo

A 2.35 KBPS Joint-Detection CDMA Speech Transceiver

The speech encoded bits generated by the proposed 2.35kbps prototype waveform interpolated (PWI) speech coder are channel-coded using turbo code. or convolutional codes and transmitted using a Joint-detection Code-division Multiple Access (JD-CDMA) scheme. The speech codec combines Zinc basis function excitation (ZFE) and mixed-multiband excitation (MMBE), in order to model the mixed voiced / unvoiced speech segments at the highest possible quality. At the receiver, a joint detection algorithm is used to separate the information of the different up-link users. It is demonstrated that for channel Signal-to-Noise Ratios (SNR) in excess of about 9dB near-unimpaired speech quality is achieved, virtually independently of the number of users supported, as long as the number of users does not exceed half of the spreading factor. Furthermore, due to the limited acceptable turbo interleaver latency the more complex turbo coded system did not outperform the convolutionally coded scheme