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A Study on the Improvements of the Speech Quality by using Distribution Characteristics of LSP parameters in the EVRC(Enhanced Variable Rate Codec)

LSP 파라미터의 분포특성을 이용한 EVRC의 음질개선에 관한 연구

  • Received : 2011.11.25
  • Accepted : 2011.12.13
  • Published : 2011.12.31

Abstract

To improve the efficiency of the channel spectrum and to reduce the power consumption of the system in EVRC, the voice signal is compressed and transmitted only when the user speaks to. In addition to this, voice frames are divided into three rates 1, 1/2 and 1/8 and each frame is handled differently. For example, we assumed that the input is silence region if the 1/8 rate is used. In this paper, the sections are firstly separated into the voiced speech signal region, unvoiced speech signal region, and silence region by using distribution characteristics of LSP parameters. Then the paper suggested to encode 1 rate for the voiced speech signal, 1/2 rate for the unvoiced speech signal region, 1/8 rate for the silence region. In other words, traditional way of transmission is used when sending full rate in the EVRC. However, when sending half rate, the voice is firstly distinguished between voiced and unvoiced. If the voice is distinguished as voiced, voice is converted into full rate before the transmission. If it is distinguished as silence, EVRC's basic rate is applied. In the experimental results with SNR, ASDM, transmission bit rate measurement, we have demonstrated that voice quality was improved by using the proposed algorithm.

Keywords

EVRC;LSP;Speech Quality;Transmission Bit Rate

References

  1. TIA/EIA-IS-127 Enhanced Variable Rate Codec, 1997.
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Acknowledgement

Supported by : 서일대학