Abstract
Problem statement: The flexible bit-rate speech coder plays an important role in the modern speech communication. The MP-CELP speech coder which is a candidate of the MPEG4 natural speech coder supports a flexible and wide bit-rate range. However, a fine scalability had not been included. To support finer scalability of the coding rate, it had been studied in this study. Approach: In this study, based on the MP-CELP speech coding with HPDR technique, Fine Granularity Scalability was introduced by adjusting the amount of transmitted fixed excitation information. The FGS feature aim at changing the bit rate of the conventional coding more finely and more smoothly. Results: Through performance analysis and computer simulation, the quality of scalability of the MP-CELP coding was presented with an improvement from conventional scalable MP-CELP. The HPDR technique is also applied to the MP-CELP to use for tonal language, meanwhile it can support the core coding rate of 4.2, 5.5, 7.5 kbps and additional scaled bit rates. Conclusion: The core coder with high pitch delay resolution technique and adaptive codebook for tonal speech quality improvement has been conducted and the FGS brings about further efficient scalability.
Highlights
In the 3GPP CDMA systems, the EVRC speech coder performs very well with much more robustness than the older codec’s
Since pitch delay significantly involves in tone of tonal language, this study proposes an improvement of the bit rate scalable MP-CELP coder by applying the High Pitch Delay Resolutions (HPDR) technique to the pitch analysis of the core coder
The comparison tests between the spontaneous Fine Granularity Scalability (FGS) and conventional scalable MP-CELP were conducted and shown in graphs of Fig. 4 and 5
Summary
In the 3GPP CDMA systems, the EVRC speech coder performs very well with much more robustness than the older codec’s. According to (Chompun et al, 2001a; 2003; Tan and Hussain, 2009; Al-Haddad et al, 2009; Haratyand El Ariss, 2007), a bit rate scalable tonal language speech coder based on a multi-pulse based code excited linear predictive coding is proposed. The coder provides the bit rate scalabilities which is effective in multimedia communications(Ozawa and Serizawa, 1998; Taumi et al, 1996; Ozawa et al, 1997). This coder is improved for the tonal language speech by applying the high pitch delay resolutions to retain the tone information precision
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