| Summary: | 碩士 === 國立交通大學 === 電信研究所 === 81 === Current research on high-quality audio coding focuses on either
subband or transform coding whereby the masking effect is
exploited in dynamic bit allocation to result in an inaudible
noise spectrum. However, the frequency-domain coding approaches
consume heavy computations and the redundancy remains to be
removed further. On the other hand, time-domain coders have the
potential to achieve transparent reproduction by incorporating
an appropriate excitation structure. In this thesis, we propose
a multi-sinusoids excitation structure which consists of the
sum of gain-scaled sinusoidal functions, rather than the white
noise as in Code-Excited LPC (CELP). The performance results
show significant improvement not only in the conventional
distortion measure such as SNR and segSNR, but also in the
newly proposed objective quality measure called generalized
bark spectral distortion (GBSD). Further more, a multi-
sinusoids excitation structure also simplifies the computation
load in about 90 times.
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