Harmonic Speech Coding - Digital Speech: Coding for Low Bit Rate Communication Systems - page 271

of SB-LPC and disperses the energy of the excitation pulses. However the
waveform shape of the synthesized speech is different from the original
speech.
8.5 Summary
The fundamental sinusoidal speech analysis and synthesis techniques have
been briefly discussed in this chapter. The basic sinusoidal model has been
modified to reduce the number of parameters in order to adapt it for low
bit-rates. At low bit-rates the frequencies of the sinusoids are restricted to
be harmonics of the pitch frequency and the harmonic phases are mod-
elled at the decoder. The concept of frequency-domain voicing is intro-
duced to achieve a compromise between the hoarseness and buzzyness of
harmonically-synthesized speech.
Three examples of low bit-rate harmonic coders have been presented:
sinusoidal transform coding (STC), improved multi-band excitation (IMBE),
and split-band linear predictive coding (SB-LPC). One of the main limitations
of low bit-rate harmonic coders is their inability to produce adequate quality
at the speech transitions.
Bibliography
[1] R. J. McAulay and T. F. Quatieri (1986) 'Speech analysis/synthesis based
on a sinusoidal representation', in IEEE Trans. on Acoust., Speech and
Signal Processing , 34(4):744-54.
[2] R. J. McAulay and T. F. Quatieri (1995) 'Sinusoidal coding', in Speech
coding and synthesis by W. B. Kleijn and K. K. Paliwal (Eds), pp. 121-74.
Amsterdam: Elsevier Science
[3] L. B. Almeida and F. M. Silva (1984) 'Variable frequency synthesis: an
improved harmonic coding scheme', in Proc. of Int. Conf. on Acoust.,
Speech and Signal Processing , pp. 27.5.1-4.
[4] I. Atkinson, S. Yeldener, and A. Kondoz (1997) 'High quality split-band
LPC vocoder operating at low bit rates', in Proc. of Int. Conf. on Acoust.,
Speech and Signal Processing , pp. 1559-62. May 1997. Munich
[5] J. Makhoul, R. Viswanathan, R. Schwartz, and A. W. F. Huggins (1978) 'A
mixed source excitation model for speech compression and synthesis',
in Proc. of Int. Conf. on Acoust., Speech and Signal Processing , pp. 163-6.
[6] D. Griffin and J. S. Lim (1988) 'Multiband excitation vocoder', in IEEE
Trans. on Acoust., Speech and Signal Processing , 36(8):1223-35.
[7] A. Kondoz, (1994) Digital Speech: coding for low bit rate communication
systems . New York: John Wiley & Sons Ltd