• Title/Summary/Keyword: CELP

Search Result 132, Processing Time 0.022 seconds

Highband Coding Method Using Matching Pusuit Estimation and CELP Coding for Wideband Speech Coder (광대역 음성부호화기를 위한 매칭퍼슈잇 알고리즘과 CELP 방법을 이용한 고대역 부호화 방법)

  • Jeong Gyu-Hyeok;Ahn Yeong-Uk;Kim Jong-Hark;Shin Jae-Hyun;Seo Sang-Won;Hwang In-Kwan;Lee In-Sung
    • The Journal of the Acoustical Society of Korea
    • /
    • v.25 no.1
    • /
    • pp.21-29
    • /
    • 2006
  • In this Paper a split bandwidth wideband speech coder and its highband coding method are Proposed. The coder uses a split-band approach. where the wideband input speech signal is split into two equal frequency bands from 0-4kHz and 4-8kHz. The lowband and the highband are coded respectively by the 11.8kb/s G.729 Annex E and the proposed coding method. After the LPC analysis, the highband is divided by two modes according to the properties of signals. In stationary mode. the highband signals are compressed by the mixture excitation model; CELP algorithm and W (Matching Pursuit) algorithm. The others are coded by the only CELP algorithm. We compare the performance of the new wideband speech coder with that of G.722 48kbps SB-ADPCM and G.722.2 12.85kbps in a subjective method. The simulation results show that the Performance of the proposed wideband speech coder has better than that of 48kbps G.722 and no better than that of 12.85kbps G.722.2.

Investigation on the Dielectric, Physical and Chemical Properties of Palm Oil and Coconut Oil under Open Thermal Ageing Condition

  • Mohamad, Nur Aqilah;Azis, Norhafiz;Jasni, Jasronita;Kadir, Mohd Zainal Abidin Ab;Yunus, Robiah;Ishak, Mohd Taufiq;Yaakub, Zaini
    • Journal of Electrical Engineering and Technology
    • /
    • v.11 no.3
    • /
    • pp.690-698
    • /
    • 2016
  • In this paper, a study is carried out to investigate the dielectric, physical and chemical properties of Palm Oil (PO) and Coconut Oil (CO) under open thermal ageing condition. The type of PO used in this study is Refined Bleached and Deodorized Palm Oil (RBDPO) Olein. The ageing experiment was carried out at 85 ℃ and 115 ℃ for 1, 3, 5, 7 and 14 days. Several parameters were measured such as AC breakdown voltage, dielectric dissipation factor, relative permittivity, resistivity, viscosity, moisture and acidity throughout the ageing duration. Based on the study, it is found that there are no significant changes on the AC breakdown voltages and relative permittivities for both RBDPO and CO. At ageing temperature of 115℃, there are clear reduction trends of dielectric dissipation factor for CO and resistivities for most of RBDPO. On the other hand, no clear trends are observed for viscosities, moisture and acidities of RBDPO and CO throughout the ageing duration.

Improving LD-CELP using frame classification and modified synthesis filter (프레임 분류와 합성필터의 변형을 이용한 적은 지연을 갖는 음성 부호화기의 성능)

  • 임은희;이주호;김형명
    • The Journal of Korean Institute of Communications and Information Sciences
    • /
    • v.21 no.6
    • /
    • pp.1430-1437
    • /
    • 1996
  • A low delay code excited linear predictive speech coder(LD-CELP) at bit rates under 8kbps is considered. We try to improve the perfomance of speech coder with frame type dependent modification of synthesis filter. We first classify frames into 3 groups: voiced, unvoiced and onset. For voicedand unvoiced frame, the spectral envelope of the synthesis filter is adapted to the phonetic characteristics. For transition frame from unvoiced to voiced, the synthesis filter which has been interpolated with the bias filter is used. The proposed vocoder produced more clear sound with similar delay level than other pre-existing LD-CELP vocoders.

  • PDF

Suitability of Palm Based Oil as Dielectric Insulating Fluid in Transformers

  • Azis, Norhafiz;Jasni, Jasronita;Kadir, Mohd Zainal Abidin Ab;Mohtar, Mohd Nazim
    • Journal of Electrical Engineering and Technology
    • /
    • v.9 no.2
    • /
    • pp.662-669
    • /
    • 2014
  • Mineral oil has been widely used as dielectric insulating fluid in transformers due to its excellent performance in-service. However, there are few issues with mineral oil such as it has poor biodegradability and could contaminate the environment if a spillage occurs. With the increasing tight regulation on safety and environment, alternative fluids for mineral oil are currently being investigated and among the suitable candidate is the vegetable oil. There are different types of vegetable oils and one of them is the palm based oil. At the moment, extensive research works are carried out to examine its feasibility to be applied in transformers. This paper will review the previous research works that were carried out to examine the suitability of palm based oil as dielectric insulating fluid in transformers. The physical and chemical properties of palm based oil are studied based on viscosity, acidity, oxidation stability and flash point. Next, the electrical characteristics of palm based oil are examined based on AC breakdown voltage, relative permittivity, dissipation factor and partial discharge.

A High-Speed LSF Transformation Algorithm for CELP Vocoders

  • Min, So-Yeon;Bae, Myung-Jin
    • The Journal of the Acoustical Society of Korea
    • /
    • v.20 no.1E
    • /
    • pp.20-24
    • /
    • 2001
  • We propose the computation reduction method of real root method that is mainly used in the CELP(Code Excited Linear Prediction) vocoder. The real root method is that if polynomial equations have the real roots, we are able to find those and transform them into LSF[1]. However, this method takes much time to compute, because the root searching is processed sequentially in frequency region. But, the important characteristic of LSF is that most of coefficients are occurred in specific frequency region. So, the searching frequency region is ordered by each coefficient's distribution. And coefficients are searched in ordered frequency region. Transformation time can be reduced by this method than the sequential searching method in frequency region. When we compare this proposed method with the conventional real root method, the experimental result is that the searching time was reduced about 46% in average.

  • PDF

A Nonlinear Regression Analysis Method for Frame Erasure Concealment in VoIP Networks (VoIP 망에서의 프레임손실은닉을 위한 비선형 회귀분석 기법)

  • Choi, Seung-Ho;Sung, Ho-Sang
    • The Journal of the Institute of Internet, Broadcasting and Communication
    • /
    • v.9 no.5
    • /
    • pp.129-132
    • /
    • 2009
  • Frame erasure is one of the most difficult problems in voice over IP (VoIP) networks and is a major source of speech quality degradation. In this paper, a frame erasure concealment algorithm based on nonlinear regression analysis is presented to minimize speech quality deterioration in code-excited linear prediction (CELP) based coders. We applied the proposed scheme to the ITU-T G.729 standard and obtained improved perceptual evaluation of speech quality (PESQ) scores compared to the conventional methods.

  • PDF

On a Study of Measurement Method of Utterance Velocity for the Reduction of Transmission Rate in CELP Vocoder. (CELP 보코더 전송률 감소를 위한 발성속도 측정 방법)

  • 장경아;나덕수;배명진
    • Proceedings of the IEEK Conference
    • /
    • 2000.09a
    • /
    • pp.175-179
    • /
    • 2000
  • 음성의 발성속도가 빠른 경우에는 발성속도가 느린 경우보다 적은 정보만으로도 부호화가 가능하다 음성의 발성속도가 빠른 경우에는 청취시 낮은 주파수 대역의 정보가 높은 주파수대역의 정보보다 중요하게 된다. 음성 부호화 기술은 전송를과 복잡도를 줄이고 음질을 향상시키는 방향으로 진행되고 있다. 현재 상용화되고 있는 CELP형 보코더는 낮은 전송를에 비해 우수한 음질을 제공하지만, 기존 방식은 음성의 발성속도에 대해서 처리를 달리하지 않고 사용하고 있다. 음성의 발성속도를 측정하여 발성속도가 빠를 경우에, 발성속도가 느린 경우보다 낮은 대역의 정보만 전송한다면 전송율을 감소시킬 수 있다. 본 논문에서는 CELP 부호화기의 전송률 감소를 위해 발성속도를 측정하는 방법을 제안한다. LSP 파라미터가 가지고 있는 정보로 음소의 변화율을 측정하였다. 각각 다른 발성속도를 갖는 음성시료에 대하여 음소 변화율을 구한 결과 발성속도가 다른 경우, 뚜렷하게 다른 음소 변화율을 갖는 것을 알 수 있었고. 빠르게 발성한 경우가 느리게 발성한 경우보다 42.8%가 높게 나왔다.

  • PDF

A Study on the Bandwidth Extension Adopted for 4800 bps CELP Speech Coder (4800bps CELP 음성 부호화기에 적용한 대역폭 확장에 관한 연구)

  • Park Sin Soo;Kim Hyung Soon
    • Proceedings of the KSPS conference
    • /
    • 2002.11a
    • /
    • pp.175-178
    • /
    • 2002
  • Most existing telephone networks transmit narrowband speech witch has been bandlimited below 4 kHz. Compared with wideband speech up to 8 kHz, narrowband speech shows reduced intelligibility and a muffled quality. Bandwidth extension is a technique to generate wideband speech by reconstructing 4-8 kHz highband speech without any additional information. This paper presents experimental results of the bandwidth extension adopted for 4800 bps CELP speech coder. In this experiment, we examine various methods for reconstruction of wideband spectrum and excitation signal, compare and analyze their performance by performing the subjective preference test and measuring the cepstral distortion.

  • PDF

Low-band Extension of CELP Speech Coder by Recovery of Harmonics (고조파 복원에 의한 CELP 음성 부호화기의 저대역 확장)

  • Park Jin Soo;Choi Mu Yeol;Kim Hyung Soon
    • MALSORI
    • /
    • no.49
    • /
    • pp.63-75
    • /
    • 2004
  • Most existing telephone speech transmitted in current public networks is band-limited to 0.3-3.4 kHz. Compared with wideband speech(0-8 kHz), the narrowband speech lacks low-band (0-0.3 kHz) and high-band(3.4-8 kHz) components of sound. As a result, the speech is characterized by the reduced intelligibility and a muffled quality, and degraded speaker identification. Bandwidth extension is a technique to provide wideband speech quality, which means reconstruction of low-band and high-band components without any additional transmitted information. Our new approach considers to exploit harmonic synthesis method for reconstruction of low-band speech over the CELP coded speech. A spectral distortion measurement and listening test are introduced to assess the proposed method, and the improvement of synthesized speech quality was verified.

  • PDF

The Computation Reduction Algorithm Independent of the Language for CELP Vocoders (각국 언어 특성에 독립적인 CELP 계열 보코더에서의 계산량 단축 알고리즘)

  • 민소연;배명진
    • Proceedings of the IEEK Conference
    • /
    • 2003.07e
    • /
    • pp.2451-2454
    • /
    • 2003
  • In this paper, we propose the computation reduction methods of LSP(Line spectrum pairs) transformation that is mainly used in CELP vocoders. In order to decrease the computational time in real root method the characteristic of four proposed algorithms is as the following. First, scheme to reduce the LSP transformation time uses met scale. Developed the second scheme is the control of searching order by the distribution characteristic of LSP parameters. Third, scheme to reduce the LSP transformation time uses voice characteristics. Developed the fourth scheme is the control of searching interval and order by the distribution characteristic of LSP parameters. As a result of searching time, computational amount, transformed LSP parameters, SNR, MOS test, waveform of synthesized speech, speech, spectrogram analysis, searching time reduced about 37.5%, 46.21%, 46.3%, 51.29% in average, computational amount is reduced about 44.76%, 49.44%, 47.03%, 57.40%. But the transformed LSP parameters of the proposed methods were the same as those of real root method.

  • PDF