• Title/Summary/Keyword: Pitch searching

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On a Performance Comparison of Pitch Search Algorithms with the Correlation Properties for the CELP Vocoder (상관관계 특성을 이용한 CELP 보코더의 피치검색시간 단축법의 비교)

  • 김대식
    • Proceedings of the Acoustical Society of Korea Conference
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    • 1994.06c
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    • pp.188-194
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    • 1994
  • Code excited linear prediction speech coders exhibit good performance at data rates as low as 4800bps. But the major drawback to CELP type coders is their large computational requirements. Therefore, in this paper a comparative performance study of three pitch searching algorithms for the CELP vocoder was conducted. For each of the algorithms, a standard pitch searching algorithm was used by the full pitch searching algorithm that was implimented in the QCELP vocoder. The algorithms used in this study is to reduce the pitch searching time 1) using the skip table, 2) using the symmetrical property of the autocorrelation , and 3) using the preprocessing autocorrelation, 4) using the positive autocorrelation, 5) using the preliminary pitch. Performance scores are presented for each of the five pitch searching algorithms based on computation speed and on pitch prediction error.

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An Algorithm to Reduce the Pitch Computational amount using Modified Delta Searching in CELP Vocoders (CELP 보코더에서 델타 피치 검색 방법 개선에 대한 연구)

  • Ju, Sang-Gyu
    • Proceedings of the KAIS Fall Conference
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    • 2010.05a
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    • pp.269-272
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    • 2010
  • In this paper, we propose the computation reduction methods of delta pitch search that is used in G.723.1 vocoder. In order to decrease the computational amount in delta pitch search the characteristic of proposed algorithms is as the following. First, scheme to reduce the computation amount in delta pitch search uses NAMDF. Developed the second scheme is the skipping technique of lags in pitch searching by using the threshold value. By doing so, we can reduce the computational amount of pitch searching more than 64% with negligible quality degradation.

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An Algorithm to Reduce the Pitch Computational Complexity Using Modified Delta Searching in G.723.1 Vocoder (CELP 보코더에서 델타 피치 검색 방법 개선에 대한 연구)

  • Min, So-Yeon;Bae, Myung-Jin
    • Speech Sciences
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    • v.11 no.3
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    • pp.165-172
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    • 2004
  • In this paper, we propose the computational complexity reduction methods of delta pitch search that is used in G.723.1 vocoder. In order to decrease the computational complexity in delta pitch search the characteristic of proposed algorithms is as the following. First, scheme to reduce the computational complexity in delta pitch search uses NAMDF. Developed the second scheme is the skipping technique of lags in pitch searching by using the threshold value. By doing so, we can reduce the computational amount of pitch searching more than 64% with negligible quality degradation.

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On a Performance Comparison of Pitch Search Algorithms by using a Correlation Properties for the CELP Vocoder (CELP 보코더의 피치 검색시간 단축법의 비교)

  • 배명진
    • Proceedings of the Acoustical Society of Korea Conference
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    • 1993.06a
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    • pp.280-287
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    • 1993
  • Code Excited Linear Prediction(CELP) speech coders exhibit good performance at data rates as low as 4800bps. The major drawback to CELP type paper, a comparative performance study of three pitch searching algorithms for the CELP vocoder was conducted. For each of the algorithms, a standard pitch searching algorithm was used by the sequential pitch searching algorithm that was implimented in the QCELP vocoder. The algorithms used in this study were 1) using the skip table(TABLE), 2) using the symmetrical property of the autocorrelation(SYMMT), and 3) using the preprocessing autocorrelation(PREPC). Performance scores are presented for each of the three pitch searching algorithms based on computation speed and on pitch prediction error.

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An Algorithm on Improving a Pitch Searching by Energy Compensation in a Frame for Vocoder (보코더에서 프레임별 에너지 보상에 의한 피치검색 성능 개선에 관한 연구)

  • Baek, Geum-Ran;Min, So-Yeon;Bae, Myung-Jin
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.13 no.7
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    • pp.3188-3193
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    • 2012
  • It is important to search a pitch for vocoder. The major drawback to vocoders is their large computational requirements in searching a pitch and a codebook. In this paper, a simple method is proposed to improve the pitch searching process in the pitch filter almost without degradation of quality. The period of speech signal is emphasized by using Dual Pulse technique, the same type of autocorrelation method, in pitch search. Sometimes the incorrect pitch can be obtained by halving, doubling and trifling, To solve it, before searching a pitch, we estimate energy rate in a frame and compensate envelop of signal with it. By using the proposed algorithm in pitch search, its required computation are reduced and searching pitch is improved.

AN ALGORITHM TO REDUCE THE PITCH SEARCHING TIME USING MODIFIED DELTA SEARCH IN CELP VOCODER (개선된 델타검색기법을 이용한 피치검색시간의 단축)

  • 이주헌
    • Proceedings of the Acoustical Society of Korea Conference
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    • 1994.06c
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    • pp.214-217
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    • 1994
  • The major drawback in the Code Excited Linear Prediction type vocoders is their large computational requirements. In this paper, a simple method is proposed to reduce the pitch searching time in the pitch filter almost without degradation of quality. On the basis of the observational regularity of the correlation function of speech, only the limited numbers of pitch lags are considered to be an optimum pitch. This is done by skipping the negative envelope side of the correlation function and limiting the maximum number of lags to be considered preliminarily. By doing so, we can reduce the computational time of pitch searching more than 51% with negligible quality degradation. In addition to that, by combining that method with the conventional delta search technique, we can reduce the computational time requirements more than 60% without serious lowering the speech quality in segmental SNR measure compared to the conventional full search method.

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A Study on Improving Voice Quality and Pitch Searching of the VSELP Coder (VSELP 부호화기의 음질 및 주기탐색 개선에 관한 연구)

  • 성기철;문상재
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.19 no.4
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    • pp.740-749
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    • 1994
  • This paper presents method for improving the performance of the VSELP speech coder. The hybrid method is employed for pitch period searching. Pitch searching time is reduced and pitch detection error, caused by quantization error of excitation signal of encoder in VSELP coder, is reduced by this method. This paper also adopts a pitch period enhancement filter and an adaptive first order filter. In this result, pitch period searching time is reduced to 26%, and MOS of reconstructed speech signal is increased by 3.19 to 4.04.

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A Study on Improving Pitch Search for Vocoder (보코더에서 피치검색 성능개선에 관한 연구)

  • Baek, Geum-Ran;Bae, Myung-Jin
    • The Journal of the Acoustical Society of Korea
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    • v.31 no.7
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    • pp.419-426
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    • 2012
  • The pitch searching is a vital process in a vocoder. Generally, the method of pitch searching is employed after highlighting the periodicity, where a correlation is identified with the signal by changing the interval of two pulses. When the correlation value reaches the peak, the pitch can be found by the pulse interval because it is the repetition interval with most striking period. However if the identified period happens to be one of half period, double period or triple period, this cannot be considered as the pitch period. Many methods were suggested to solve this problem. An inaccurate pitch could be obtained as well, when there is an interval where signal amplitude is not constant but varies abruptly in the frame. To solve this matter, searching the pitch by dividing a frame into various subframes is adopted, but too much calculation has to be followed while it leads the correct value. This paper suggests an algorithm to resolve these two problems. First, to search the pitch after advance correction of the signal energy level with an estimated overall energy change ratio in the frame before pitch search to reduce half period, double period and triple period is suggested. Second, to vary the number of subframes by predicting the amplitude change rate in the frame by the energy ratio obtained by the above-mentioned method is advised. If these two methods are applied, the pitch searching time can be reduced and the general pitch searching performance can be improved without affecting the sound quality in the synthesized signal.

On a Reduction of Pitch Search Time for IMBE Vocoder by Using the Spectral AMDF (SAMDF를 이용한 IMBE VOCODER의 피치 검색 시간 단축에 관한 연구)

  • 홍성훈
    • Proceedings of the Acoustical Society of Korea Conference
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    • 1998.06c
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    • pp.155-158
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    • 1998
  • IMBE(Improved Multi-Band Excitation) vocoders exhibit good performance at low data rates. The major drawback to IMBE coders is their large computational requirements. In this paper, thus, we propose a new pitch search method that preserves the quality of the IMBE vocoder with reduced complexity. The basic idea is to reduce computation complexity of the pitch searching by using the SAMDF. Applying the proposed method to the IMBE vocoder, we can get approximately 52.02% searching time reduction in the pitch search. There is no difference in voice quality between conventional IMBE and proposed IMBE.

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A Study on Improving Pitch Search by Varying the number of Subframes for Vocoder (보코더에서 서브프레임 수의 변화를 이용한 피치검색 성능 개선에 관한 연구)

  • Baek, Geum-Ran;Bae, Myung-Jin
    • Journal of the Institute of Electronics and Information Engineers
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    • v.49 no.10
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    • pp.83-88
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    • 2012
  • The pitch searching is a very important process in a vocoder. Generally, the method of pitch searching method is used by highlighting the periodicity, where a correlation is identified with the signal by changing the interval of two pulses. When the correlation value is highest, the pitch can be found by the pulse interval because it is the repetition interval with most striking period. There are many methods to solve this problem and search the pitch by dividing a frame into many subframes, but there is too much calculation to solve. A method in this paper is suggested to vary the number of subframes by predicting the amplitude change rate in a frame. If this method is applied, the general pitch searching performance will be improved because the accuracy may be enhanced without affecting the sound quality in the synthesized signal after parameter transmission; and the pitch searching time may be reduced.